All India Difficult Airway Association 2025 Guidelines for the management of unanticipated difficult airway in adults under general anaesthesia

Abstract

The All India Difficult Airway Association 2025 Adult guideline provides guidance for the management of an unanticipated difficult airway under general anaesthesia. The American Heart Association (AHA) Class of Recommendation and Level of Evidence was used. In addition, for interventions where the evidence was absent or weak, a Delphi process among airway experts was convened to generate expert consensus statements. The most significant difference from the 2016 guidelines is providing guidance for a failed supraglottic airway (SGA) insertion, tracheal intubation, face mask ventilation, or other strategies commonly used as part of the primary airway plan under general anaesthesia, not restricting to a failed intubation. Airway assessment should be routinely performed to identify an anatomical as well as the physiologically difficult airway. Peri-intubation oxygenation with pre-oxygenation and apnoeic oxygen with nasal oxygen (10–15 L/min) or high-flow nasal oxygen increases the safe apnoea time. Videolaryngoscopy and adjuncts such as stylets and bougies improve first pass intubation success. Tracheal tube position should be confirmed by waveform capnography. If the primary airway plan fails, activate ‘Code D’ as the hospital emergency code to call for help. Airway rescue should then be attempted with any of the three devices (tracheal tube, SGA, or face mask), and switching promptly between them as needed, with no hierarchy, until effective ventilation and adequate oxygen saturation (SpO₂) are achieved. Optimise patient position, ensure neuromuscular blockade, and consider changing the tools, technique, or operator. Allow up to three failed attempts with these devices provided the SpO₂ remains ≥95%. Complete ventilation failure (ventilation using a tracheal tube, SGA, and face mask have all failed, even if oxygenation may be maintained) is the trigger to perform an emergency cricothyroidotomy, preferably by a surgical approach. Team debriefing, team support, patient and family counselling, and documentation are paramount after encountering an unanticipated difficult airway.

DISCLAIMER

These guidelines have been developed to help clinicians manage unanticipated difficult airways in patients using evidence-based recommendations or Delphi consensus opinions from airway experts, wherever evidence was lacking or weak. These guidelines do not represent the minimum standard of practice, nor are they a substitute for good clinical judgement. The recommendations in the guidelines assume that the airway operator has adequate experience with the devices and techniques described and that these are applied within the scope of their practice. Recommendations regarding the use of specific resources (devices, medications, or workforce) apply where these resources are available. These recommendations should be viewed as aspirational, when this is not the case. While careful attention has been paid to provide the accurate and updated information, the authors acknowledge that the literature related to airway management is rapidly changing, altering our attitudes and clinical practice. It is important to note that application of these recommendations in specific settings remains the responsibility of the clinician.

INTRODUCTION

A difficult airway is defined as a clinical situation in which an experienced airway operator encounters difficulty or failure with face mask ventilation, laryngoscopy, tracheal intubation, ventilation using a supraglottic airway (SGA), or invasive surgical airway.[1,2,3] Managing an unanticipated difficult airway is one of the most critical and stressful situations, testing an airway operator’s technical and non-technical skills. This scenario can often become life-threatening if not managed effectively. The fourth National Audit Project (NAP4) conducted in the UK strongly recommended the adoption of airway algorithms and proposed that their utilisation might lead to improved patient outcomes.[4]

In 2016, the All India Difficult Airway Association (AIDAA) developed the first national guidelines for evidence-based management of unanticipated difficult airway in adults, obstetrics, paediatrics, management of difficult extubation, and management of tracheal intubation in intensive care unit (ICU).[3,5,6,7,8] The AIDAA 2016 Guidelines introduced several unique features, including a strong emphasis on peri-intubation oxygenation and the recommendation to proceed with further airway attempts only when oxygen saturation (SpO₂) is maintained at ≥95%. Confirmation of tracheal intubation was mandated by the presence of six consecutive, sustained capnography waveforms without a fall in carbon dioxide levels. The guidelines also introduced a new term, ‘complete ventilation failure’, as the trigger for cricothyroidotomy, with a call for additional help in such situations. Furthermore, they recommended selecting the cricothyroidotomy technique based on the clinician’s familiarity and the availability of equipment.[6,9] A survey conducted among practising anaesthesiologists in 2020 showed high awareness (81%) of the guidelines.[10] While most recommendations were followed, there was wide variation in their adherence by anaesthesiologists, primarily related to the use of apnoeic oxygenation, capnography, debriefing after an airway event, and issuing an airway alert card.[10] The acceptability and adherence of the AIDAA guidelines have increased since.

The evolution of technology, medical literature, and clinical practices in airway management over the past few years has necessitated the revision of the AIDAA guidelines. While the AIDAA 2016 adult guidelines provide an algorithmic approach for a failed tracheal intubation, they do not provide guidance for a failed SGA insertion, face mask ventilation, or other strategies commonly used as part of a primary airway management plan. This important limitation makes these guidelines incomplete for addressing unanticipated difficult airway scenarios, where tracheal intubation has not been a part of the primary or initial airway management plan. The AIDAA leadership therefore planned to update the existing AIDAA 2016 guidelines.

HOW DO THE AIDAA 2025 ADULT GUIDELINES DIFFER FROM 2016 GUIDELINES?

In the AIDAA 2025 guidelines, the recommendations and best practice statements have been categorised according to the American Heart Association (AHA) Class of Recommendation and Level of Evidence to clinical strategies, interventions, treatments, or diagnostic testing in patient care.[11] In addition, for interventions where the evidence was absent or weak, a Delphi process among airway experts was convened to generate expert practice statements.[12] The AIDAA 2016 guidelines did not include graded recommendations.

The most significant difference in the AIDAA 2025 guidelines is providing guidance for a failed SGA insertion, tracheal intubation, face mask ventilation, or other strategies commonly used as part of a primary airway management plan under general anaesthesia, not restricting to guidance following a failed intubation. “Code D” has been proposed as the hospital emergency code to indicate that the patient has a difficult airway and immediate assistance and intervention is needed.[13] The AIDAA 2025 guidelines have moved away from a linear approach to a circular pattern with emphasis on interchangeability between the three devices used for ventilation (tracheal tube, SGA, and face mask) following a failed primary airway plan to achieve effective ventilation and oxygenation. Surgical cricothyroidotomy has been suggested as the preferred technique for performing cricothyroidotomy based on updated evidence, while in 2016, any cricothyroidotomy technique could be performed based on familiarity and availability of equipment. The role of peri-intubation oxygenation and use of waveform capnography to confirm tracheal tube placement has been further emphasised in the AIDAA 2025 guidelines.

METHODS

Six Patient/Population, Intervention, Comparison, and Outcome (PICO) questions were formulated based on the literature review and discussions among the adult Guideline Subcommittee members. A systematic literature search, data extraction, and evidence synthesis were conducted for each PICO question. The literature search was performed in PubMed and Scopus, covering the period from January 2000 to December 2024, using search strings tailored to each PICO question. A concept table, search strings, and PRISMA flowcharts outlining the search process for each PICO question are summarised in Appendices (1–6). All retrieved articles were imported into the Rayyan software (Rayyan Systems Inc., Cambridge, Massachusetts, USA; http://rayyan.qcri.org) for initial screening.[14] Two reviewers independently screened the titles and abstracts of each article and selected the final list of full-text studies for inclusion. A table of the shortlisted articles was compiled. The evidence was summarised, and recommendations were categorised according to the American Heart Association (AHA) Class of Recommendation and Level of Evidence for clinical strategies, interventions, treatments, or diagnostic testing in patient care.[11] Where evidence was absent or weak, the Steering Committee initiated a Delphi process to reach consensus (75% and above) among airway experts.[12] Statements were included in successive Delphi rounds until stability criteria were met. Expert consensus statements were then drafted based on survey items that reached consensus. Complete details of the guideline development process and methodology, including the Delphi process, are provided in the AIDAA Guideline Development Process and Methodology article.[15] The consensus and stability analysis of the clinical statements from Delphi Survey are available in Appendix 7.

HUMAN FACTOR CONSIDERATIONS

Human factors are defined as environmental, organisational, and job factors together with individual human characteristics, which influence behaviour at work in a way which can affect health and safety.[16] These factors can often result in avoidable errors in high-stress, time-sensitive scenarios such as airway emergencies.

During an airway crisis, the primary airway operator may be presented with more information than can be processed, often resulting in cognitive overload which can impair decision-making, and cause fixation on a particular task.[17] The NAP4 showed that 40% of the major complications in airway management were associated with human factor-related issues.[4] The non-technical skills of the airway operator form an integral component of human factors and are as important as the technical skills in airway management in influencing patient outcomes. Addressing human factors principles can reduce the dependence on exceptional staff performance in a difficult airway situation.[18]

Human factors that commonly influence performance during airway emergencies include cognitive challenges (e.g., cognitive overload, loss of situational awareness, and fixation errors), communication barriers (e.g., ineffective exchange of information and lack of role clarity), impaired decision-making under stress (e.g., inadequate preparation or deviation from a structured plan), and equipment and ergonomic issues such as unfamiliarity with devices or a cluttered environment; limitations related to training, experience, and fatigue, including inexperience or impaired judgment; and cultural or systemic influences, such as hierarchical barriers and deviations from established protocols.[2,19,20]

Various strategies can be adopted to overcome these issues, including the use of checklists, team preparation, advance planning, role briefing task sharing, flattening the hierarchy, closed-loop communication, a “stop and think” approach, use of cognitive aids, and team debriefing. A post-event debrief is essential to identify what went wrong as this may help in preventing any such future event. The use of cognitive aids have shown to improve non-technical skills during a simulated airway crisis.[21] The Vortex Approach has been devised to support decision-making during difficult airway management.[22] Every adverse event should be seen as an opportunity to improve, correct system faults, and enhance safe practices. This can happen only when there is a culture of no blaming, naming and shaming.[3] Simulation-based training has been shown to improve outcomes during airway management.[23] Regular simulation training using airway protocols and airway scenarios can go a long way in enhancing non-technical skills required for difficult airway management.

TEAM DYNAMICS DURING AN AIRWAY EMERGENCY

Effective teamwork is paramount during an airway emergency where time-sensitive interventions may be required and life-threatening conditions may occur. Team dynamics in airway management refers to the way airway teams communicate and coordinate with each other during an airway intervention, especially during an emergency. Effective leadership and teamwork, clarity of roles and responsibilities, closed loop communication, team members empowered to speak up, situational awareness, using available resources efficiently, and debriefing and reviewing team performance after an airway event are integral components of team dynamics.[18,20]

RISK ASSESSMENT FOR AIRWAY MANAGEMENT

Risk assessment for airway management includes airway assessment to predict an anatomically or physiologically difficult airway and assessment of the risk of pulmonary aspiration. Risk assessment includes evaluation of information obtained from the patient/family history, clinical examination, medical records, diagnostic tests, imaging, and overall assessment of the clinical condition of the patient. We suggest that risk assessment for airway management should be performed in advance and prior to initiation of anaesthesia and airway management by the person responsible for airway management, if feasible.

Airway assessment should be routinely performed to identify anatomical factors that may lead to difficulty with facemask ventilation, SGA device insertion, laryngoscopy, tracheal intubation, or emergency surgical airway access. Recognising potential airway challenges in advance enables the formulation of a safe airway management plan for the patient.[3] A history of previous difficulty is a more reliable predictor of difficulty than any bedside examination.[24,25,26] Although the upper lip bite test has shown to have the most favourable diagnostic test accuracy, none of the commonly used individual or group indices are reliable to screen for a difficult airway with good accuracy.[24,25,26] Therefore, one should be prepared for managing an unanticipated difficult airway in a patient at any given time.

A physiologically difficult airway is one in which the patient’s physiological (e.g., pregnancy) and pathophysiological alterations increase the risk for complications during tracheal intubation and transition to positive pressure ventilation. Pathophysiological alterations include hypoxaemia, cardiovascular instability, right ventricular dysfunction, and increased intracranial pressure, commonly occurring in critically ill patients.[27] Patients at risk of pulmonary aspiration during general anaesthesia include those who are not adequately fasted, neurologically impaired patients, patients with altered consciousness, critically ill patients, and those with gastrointestinal conditions (e.g., bowel obstruction, gastroesophageal reflux disease, gastroparesis, those taking glucagon-like peptide-1 receptor agonists, etc.). Gastric point-of-care ultrasound (POCUS) is emerging as a powerful bedside tool to achieve personalised risk assessment of the likelihood of pulmonary aspiration in patients undergoing general anaesthesia when the fasting status is uncertain, or patient physiology predisposes to delayed gastric emptying.[28]

PATIENT PREPARATION FOR AIRWAY MANAGEMENT UNDER GENERAL ANAESTHESIA

The risk assessment for airway management should be considered to plan the strategy for airway management before the induction of anaesthesia. The strategy should be discussed in advance with the team, including the roles and responsibilities of the members and the back-up plan in case of failure.

For patients at risk of aspiration, a rapid sequence induction should be considered. Reduction of the gastric volume and an increase in pH should be done before surgery through adequate fasting and pharmacological means. In conditions where there is delayed gastric emptying or intestinal obstruction, a nasogastric tube insertion should be considered for mechanical drainage.[4]

Preoperative sedation and analgesia should be used with caution in patients with a compromised airway (both anatomically and physiologically). An anatomically compromised airway is one in which airway patency, protective function, or adequacy of ventilation is impaired or at risk of becoming compromised.

PRE-OXYGENATION

Pre-oxygenation is performed prior to securing the airway to increase the oxygen reserve and prolong the safe apnoea time [time between onset of neuromuscular bloackade and oxygen desaturation]. Whenever possible, pre-oxygenation should be done in a 20° head-up position as it is generally more comfortable for patients and facilitates taking deep breaths. In contrast, the supine position predisposes the posterior lung segments to atelectasis and collapse, thereby reducing oxygen reserves.[3]

Pre-oxygenation should be performed with tidal volume breathing for a minimum of 3 minutes[29] and should be prolonged for 5 min if a mask leak is present.[30] Nasal cannula oxygen supplementation can improve the efficacy of pre-oxygenation if there is a mask leak.[30] Pre-oxygenation with eight vital capacity breaths over 60 seconds is an alternative method that is effective. Pre-oxygenation following forced exhalation followed by tidal breathing is more effective. An end-tidal oxygen concentration >90% and an end-tidal nitrogen concentration <4% should be targeted if gas monitoring is available.[29] When a closed circuit is used, pre-oxygenation should be done with a pre-filled oxygen circuit using a minimum oxygen flow rate of 10 L/min. Non-invasive ventilation improves the effectiveness of pre-oxygenation.[29] Application of continuous positive airway pressure (CPAP) of 5–10 cm H₂O or pressure support ventilation of 5–15 cm H₂O with positive end expiratory pressure (PEEP) or high flow nasal oxygenation (HFNO) should be applied if feasible in high-risk patients including obese, obstetric, and critically ill patients.[29]

OPTIMISING TRACHEAL INTUBATION IN ADULTS

Patient positioning for tracheal intubation

Optimal patient positioning improves the likelihood of successful laryngoscopy and tracheal intubation.[31] The sniffing position, traditionally used for direct laryngoscopy, has been challenged in recent years.[32,33] The theoretical rationale was that sniffing position led to the alignment of the laryngeal, pharyngeal, and oral axes, making the line of sight fall directly on the glottis.[33] A meta-analysis of six randomised controlled trials found no benefit of sniffing position over other positions with respect to laryngeal visualisation, first pass intubation success rate, or intubation time. However, sniffing position was associated with a better Intubation Difficulty Scale (IDS) compared with simple head extens tube insertion should be considered

ion position.[34] The authors suggested that sniffing position should still be considered as the initial position for tracheal intubation as it provides easier conditions for intubation.

The ramped position, achieved by elevating the head and upper body to align the external auditory meatus with the sternal notch horizontally, offers better glottic visualisation during direct laryngoscopy than the sniffing position in morbidly obese patients.[35] The head elevated laryngoscopy position (HELP), a 25° head elevation, or back-up of the operating table improved glottic visualisation during laryngoscopy when compared with the supine position.[36,37] While recent studies have found the ramped position or HELP to be superior to sniffing position, the degree of head elevation required to facilitate the external auditory meatus and sternal notch alignment is variable among patients. Of note, the use of videolaryngoscopes and flexible bronchoscopes does not mandate the use of any of these positions.[31]

Induction agent, neuromuscular blockade, and mask ventilation

The choice of the induction agent will depend on the patient condition and the clinical context. Propofol suppresses the laryngeal reflexes, providing superior intubating conditions as compared to other agents, and is the most commonly used induction agent. Adequate depth of anaesthesia should be ensured during repeated attempts at tracheal intubation to prevent awareness. Mask ventilation should be provided soon after induction of anaesthesia.

NMBAs result in apnoea, abolish the laryngeal reflexes, and improve chest wall compliance[38,39] and thus can improve the chances of successful airway management when face mask ventilation is difficult.[40] Rocuronium has a rapid onset of action and can be antagonised with sugammadex. Sugammadex reverses the effects of steroidal NMBA rapidly and completely. Unlike neostigmine, its antagonism is long-lasting, has no ceiling effect, and does not lead to paradoxical reversal. However, the incidence of anaphylaxis may be higher than with other non-depolarising NMBAs.

The conventional practice of testing mask ventilation prior to administering NMBA is not evidence-based and has been questioned in recent times. Omitting mask ventilation after induction of anaesthesia and before administering NMBA saves crucial time, prioritising the primary goal which is tracheal intubation. In patients with a limited oxygen reserve, relying on succinylcholine alone to regain spontaneous ventilation quickly following complete ventilation failure may not be practical. In contrast, administration of 16 mg/kg sugammadex can reverse the effects of rocuronium and restore neuromuscular function within 1.3–5.2 minutes.[41,42,43] The resumption of spontaneous breathing with a high dose of sugammadex is much faster than the spontaneous recovery after a standard dose of succinylcholine.

In a cohort of 22,660 mask ventilations, only 37 (0.16%) were truly impossible. Of these 37 patients, 36 (97.3%) were successfully intubated using direct laryngoscopy, while one patient required a surgical cricothyrotomy.[44] These findings suggest that initial test mask ventilation in these cases was futile and wasted valuable time during a critical period. Moreover, use of NMBA has shown to improve, rather than hinder the efficacy of mask.[39,45,46]

During rapid sequence induction, either rocuronium or succinylcholine may be used unless contraindicated to rapidly achieve intubating conditions. When rocuronium is used at a dose of ≥ 1.2 mg/kg, intubating conditions equivalent to those of succinylcholine are achieved within 60 seconds.

Apnoeic oxygenation

Insufflation of continuous oxygen at 10–15 L into the pharynx through the nasal cannula, airway, or catheter can extend the duration of the safe apnoea time after neuromuscular blockade.[47,48] The two prerequisites for apnoeic oxygenation to be beneficial are prior optimal pre-oxygenation and maintaining upper airway patency. These techniques are not beneficial when used in a desaturating patient as a rescue. NODESAT (Nasal Oxygen During Efforts at Securing A Tube) is a technique of providing apnoeic oxygenation through a nasal cannula at 15 L/min. This is an easy and effective means of giving apnoeic oxygenation during tracheal intubations; however, the CO₂ rise during apnoea cannot be controlled.[49] The nasal cannula can be placed under a facemask during pre-oxygenation, and then it can be used to administer nasal oxygen during tracheal intubation. AIDAA suggests the use of this technique, not only in anticipated difficult airway but also during routine intubations.

The Trans-nasal Humidified Rapid Insufflation Ventilatory Exchange (THRIVE),[50] which provides 100% oxygen at a flow rate of up to 70 L/min, is used for pre-oxygenation and continued apnoeic oxygenation, until a definitive airway is secured. This requires dedicated equipment with an oxygen humidification unit, nasal oxygen cannula, and tubing connecting the standard oxygen regulator to the trans-nasal oxygen cannula. This technique provides CPAP during pre-oxygenation and apnoeic oxygenation with a flow-dependent flushing of the dead space, thereby reducing the rate of rise of CO₂ during apnoea.[50] This method significantly prolongs the safe apnoea time, thus allowing securing a definitive airway during a difficult intubation or failed intubation to be done in an unhurried manner. THRIVE should be used if feasible, especially when a difficult airway is anticipated.

Laryngoscopy and tracheal intubation

Nasal oxygenation using NODESAT (oxygen flow at 15 L/min)[49] or THRIVE[50] should be continued during attempts at tracheal intubation to prolong the safe apnoea time, especially in cases of an anticipated difficult airway. Each insertion of a laryngoscope blade into the oral cavity is considered as an attempt at laryngoscopy. Repeated attempts at laryngoscopy can result in airway trauma, which increase the risk of progressing to a ‘complete ventilation failure’ situation. Each successive attempt is associated with increased risk of complications, and therefore, attempts at intubation should be kept to a minimum. Therefore, it is essential to emphasise the importance of first pass intubation success and use tools and strategies to achieve this.

The use of videolaryngoscopy (VL) and adjuncts such as stylets and bougies should be encouraged to improve first pass intubation success. VL provides an indirect view of the glottis, often superior to direct laryngoscopy. Use of VL has clearly demonstrated a higher first pass intubation success rate compared to direct laryngoscopy, especially in difficult airway cases, and therefore should be used as the default tool for laryngoscopy, when feasible.[51] In addition, VL has the unique advantage of not requiring optimal position or excessive force as with direct laryngoscopy (DL), making it beneficial for use in trauma victims and other conditions requiring cervical immobilisation. The shared glottic view provides an excellent opportunity for teaching, training, documentation, and review. Despite the effectiveness of the VL, and even when available, DL may be considered based on operator experience and the clinical context.

External laryngeal manipulation or backward, upward, and right-directed pressure (BURP) applied by an assistant may improve the laryngoscopic view.[52,53] A pre-shaped stylet or bougie may be used to facilitate tracheal intubation in Cook’s modification of Cormack and Lehane Grade 2b and 3a laryngeal view.[54,55] However, blind insertion in Grade 3b or 4 direct laryngoscopic view is not recommended as it may cause trauma.[56] A stylet should be considered during VL, especially when a hyperangulated blade is used. Changing the airway device, technique, or operator may increase the chances of intubation success.

Confirmation of tracheal tube position

The gold standard for confirming tracheal tube position is continuous waveform capnography, which provides breath-by-breath confirmation of effective alveolar ventilation. Other methods such as visual confirmation of passage of the tracheal tube between the vocal cords, bilateral chest expansion, and five-point auscultation should complement and not replace capnography. In 2016, AIDAA was the first airway society to put a number to the capnography traces to be detected before confirmation of tracheal tube position.[2] AIDAA recommended the presence of six consistent capnography traces without any decline in the detected carbon dioxide (CO₂) levels. The rationale for this is that one or two waveform capnography traces may be noted when the tracheal tube is in the oesophagus, especially when there is gastric insufflation with gas, as is seen following a difficult mask ventilation. However, this capnography trace will soon start declining with the tube still in the oesophagus and touch baseline. Therefore, confirming tube placement based on one or two capnography traces is not reliable.

The consensus guideline for preventing unrecognised oesophageal intubation from the Project for Universal Management of Airways[57] (PUMA) and international airway societies (including AIDAA) recommends verifying the presence of sustained exhaled CO₂ meeting all four criteria: (1) amplitude rises during exhalation and falls during inspiration, (2) consistent or increasing amplitude over at least seven breaths, (3) peak amplitude more than 7.5 mmHg above baseline, and (4) reading is clinically appropriate.

In addition, they recommend that both the airway operator and assistant should each verbalise the presence of sustained exhaled CO₂ and adequate SpO₂ following tracheal intubation. Oesophageal intubation should be actively ruled out if there is absence of sustained exhaled CO₂. The default response should be to remove the tube and attempt ventilation using a facemask or SGA. If immediate tube removal is not undertaken, one should rule out oesophageal intubation by performing repeat laryngoscopy, flexible bronchoscopy, or ultrasound. Clinical examination should not be used to exclude oesophageal intubation. Tracheal tube removal should be done immediately if oesophageal placement cannot be excluded, sustained exhaled CO₂ cannot be restored, or SpO₂ deteriorates at any point before restoring sustained exhaled CO₂.[57]

MASK VENTILATION

Mask ventilation should be provided soon after induction of anaesthesia and between attempts at securing the airway. Inadequate chest rise during mask ventilation may be due to an obstructed airway or an air leak around the mask. Use of continuous waveform capnography should be considered during pre-oxygenation and continued during mask ventilation. A triangular, rather than a square end tidal carbon dioxide (EtCO₂) trace or a low numerical EtCO₂ value may indicate a leak around the face mask and should prompt interventions to improve the seal.[58] When difficulty is encountered during mask ventilation, consider changing to a mask with a better fit; optimise position; use airway manoeuvres such as head tilt, chin lift, or jaw thrust; consider two-handed mask holding techniques; and consider using adequately sized oropharyngeal and/or nasopharyngeal airways. Increasing the depth of anaesthesia, ensuring NMBA, and changing the airway operator may help.[59,60]

Failure of mask ventilation despite the best efforts described above should be identified early, and alternate methods of ventilation should be implemented without any delay. When there is difficulty or failure of mask ventilation, SGA insertion can be used as the primary hands-free technique for maintaining oxygenation.[59]

SUPRAGLOTTIC AIRWAY DEVICES

SGA devices have become popular globally to facilitate general anaesthesia and surgery as an alternative to tracheal intubation for non-cardiac surgery. The SGA is easier to place and results in less tracheal injury and airway stimulation than a tracheal tube.[61] SGAs also play an important role as airway rescue devices for failed tracheal intubation and mask ventilation.

Second-generation SGAs have improved efficacy and increased safety as compared to first-generation devices.[62,63] They have a higher sealing pressure, a gastric tube, and a bite block. They are recommended as rescue devices during difficult airway management over first-generation devices by airway societies.[2,3,19] Use of cricoid pressure may interfere with SGA insertion by reducing the hypopharyngeal space and therefore should be removed.[64,65] If initial insertion of the SGA fails, changing over to another type of SGA has been shown to be successful.[66] Repeated attempts at SGA insertion may result in trauma and will further delay the use of other measures to maintain oxygenation.

If tracheal intubation is required in a patient in whom an SGA has been inserted as a rescue airway, it should be performed only under vision using a flexible bronchoscope[67,68,69] provided the patient is stable, oxygenation through the SGA is possible, and the operator is familiar with the technique. Blind intubation through the SGA has a very low first attempt success rate, with a potential to cause complete loss of an established airway and serious adverse events, and therefore should not be attempted when an SGA has been inserted as a rescue device. The use of an Aintree Intubation Catheter™ (Cook Medical, Bloomington, USA) over a bronchoscope facilitates guided tracheal intubation through the SGA where direct bronchoscopy-guided intubation is not possible.[67,70] In addition, it facilitates the passage of a larger size tube of any type, which may may not be possible while intubating through an SGA.

CRITICAL LANGUAGE DURING AN AIRWAY EMERGENCY

Effective communication is crucial during an airway emergency to minimise errors and avoid complications.[71,72] Terminology should not be used merely because it is catchy and advocated by a few. It must accurately reflect the nature of the situation, convey a sense of urgency, and suggest an action sequence.[73] The term “critical language” refers to standard communication, where specific terms having a clear, mutually understood meaning are used to avoid confusion and improve team situational awareness.[74,75] Critical language should be clear, simple, concise, precise, easy to articulate, intuitive, easy to remember, consistently used, and readily understood by all team members. Having anatomical or physiological words in the terminology further aids understanding in an emergency situation.[73] The term “cardiac arrest” used during cardiopulmonary resuscitation is an example of effective critical language. The terms “Code D”, “complete ventilation failure”, and “emergency cricothyroidotomy” are examples of the critical language proposed for use by AIDAA.

CALL FOR HELP

A call for help should be made when the first difficulty in airway management is encountered. In case this has been missed or help has not arrived, one should call for help at any stage while managing an unanticipated difficult airway. The help of an airway expert should be sought, if available. The AIDAA suggests calling for additional help after the best attempt at ventilation using a tracheal tube, SGA, and mask is unsuccessful (complete ventilation failure) and emergency cricothyroidotomy is planned. An additional person who has not been part of the process may be able to think more rationally and perform better in this situation, in addition to being an extra helping hand. In a crisis situation, one can be presented with more information than can be processed, making the clinician get fixated on a particular task.[22] The human factor considerations during this critical juncture justify calling for additional help. The AIDAA proposes “Code D”, as the hospital emergency code to indicate that the patient has a difficult airway and immediate assistance and intervention is needed.

COMPLETE VENTILATION FAILURE

Airway societies have used different terminologies to describe the situation where attempts to manage the airway using a tracheal tube, SGA, or a mask are unsuccessful, despite using the best attempt. The Difficult Airway Society (DAS),[25] Canadian Airway Focus Group (CAFG),[1] and the American Society of Anaesthesiologists (ASA)[3] use the terminology ‘cannot intubate, cannot oxygenate’ (CICO), ‘cannot ventilate, cannot oxygenate’ (CVCO), and ‘cannot intubate, cannot ventilate’ (CICV), respectively.

In 2016, AIDAA coined a new terminology, “complete ventilation failure”. Complete ventilation failure is defined as a clinical situation where ventilation using a tracheal tube, SGA, and face mask have all failed after giving the best attempt, even if oxygenation may be maintained.[2] The AIDAA guidelines recommend immediately proceeding with an emergency cricothyroidotomy when complete ventilation failure is encountered. Ventilation failure precedes oxygenation failure and is therefore a safer trigger to perform emergency cricothyroidotomy, while oxygenation is maintained and not when hypoxaemia sets in.

Airway guidelines continue to use “cannot intubate” in their critical language terminology.[3,25] In present times, tracheal intubation is not the only means of ventilating a patient. Ventilation can be achieved by other means such as using an SGA. Therefore, the use of “cannot intubate” in the terminology seems redundant. The term “oxygenation” is poorly understood. To some, it means preservation of SpO₂, while to some, oxygenation could refer to a state where there is delivery of oxygen to the lungs by ventilation, confirmed by an EtCO₂ trace; thus, an absence of this confirms that one “can’t oxygenate”. However, adequate oxygenation can also be achieved by pre-oxygenation and apnoeic oxygenation, where the oxygen concentration in the alveoli is maintained, despite not ventilating the lungs. In this situation, the SpO₂ may be preserved for several minutes. While it is not known how long the SpO₂ will be in the normal range, it is inevitable that once ventilation has failed, the SpO₂ will fall. The time to oxygen desaturation however depends on factors including the patient’s oxygen reserve, the duration of pre-oxygenation, and the use of apnoeic oxygenation. Thus, despite the inability to ventilate the lungs, the interpretation of “oxygenation” and therefore “can’t oxygenate” can vary significantly, leading to disparity in the trigger for proceeding to a rescue surgical airway. This may delay the appropriate action and result in adverse outcomes. Figure 1 shows the pathway to hypoxia and adverse events following a failed airway. Using complete ventilation failure as the trigger for emergency cricothyroidotomy (time point one) involves an earlier intervention, providing a safer margin to prevent hypoxia.

Figure 1.

Pathway to hypoxia and adverse events following a failed airway. Points 1, 2, and 3 represent potential time points at which one may consider emergency cricothyroidotomy. Reference: Adapted from Indian J Anaesth. 2020;64 (4):275-279

EMERGENCY CRICOTHYROIDOTOMY

A recent survey of anaesthetists found emergency cricothyroidotomy to be the most dominant terminology used in clinical practice, suggesting that there is quite a disconnect between the dominant terminology used in literature (e.g., front of neck airway) and in clinical practice.[76] The terminology emergency cricothyroidotomy conveys the sense of urgency with a focus on the anatomical landmark to be targeted. In addition, it is simple, concise, intuitive, precise, and inclusive of various techniques.

Emergency cricothyroidotomy is the rescue procedure to be performed when there is complete ventilation failure. The cricothyroid membrane (CTM) is a superficial structure which can be easily located and accessed, is relatively avascular, and is less mobile, making cricothyroidotomy faster to perform than tracheostomy. The membrane can be easily identified by using a technique called the laryngeal handshake described by Levitan. The ‘laryngeal handshake’ is more accurate, though it takes longer than the conventional palpation technique in locating the CTM and the midline.[77] The laryngeal handshake involves palpation of the greater cornu of the hyoid bone with the index finger and thumb. “Then roll the larynx from side to side. The fingers and thumb slide down over the thyroid lamina. Keep the middle finger and thumb on the cricoid cartilage and move the index finger down to palpate the cricothyroid membrane.” It may be useful to identify and mark the cricothyroid membrane before induction of anaesthesia in patients with an anticipated difficult airway. In obese individuals where the landmarks are not easily palpable, the use of ultrasound to locate and mark the cricothyroid membrane may prove useful, including in crisis situations.

The options for the emergency cricothyroidotomy include surgical cricothyroidotomy, needle cricothyroidotomy, or wide bore cannula cricothyroidotomy. The surgical cricothyroidotomy technique requires a scalpel/stab knife, a bougie, and a size six tracheal tube, which are universally available to airway operators. The needle cricothyroidotomy technique requires pressure-regulated jet ventilation. Special commercially available cricothyroidotomy kits are required to perform wide bore cannula cricothyroidotomy.

The patient is positioned supine with the neck extended. A shoulder roll or dropping the head over the operating table may help. Aseptic techniques and universal precautions should be observed. While emergency cricothyroidotomy is performed, attempts at face-mask ventilation and apnoeic oxygenation should be continued by the other airway operators. Once successful ventilation is achieved, the cricothyroidotomy may be converted to a tracheostomy.

While emergency cricothyroidotomy should be the default procedure performed during complete ventilation failure, a surgical tracheostomy may be considered if a surgeon experienced to perform the procedure is available at site.

SURGICAL CRICOTHYROIDOTOMY

The surgical techniques have demonstrated better success rates and faster airway access even when performed by inexperienced operators.[78,79] In adult patients, AIDAA suggests performing surgical cricothyroidotomy using the “stab-twist-bougie-tube” technique, which is simple, easy to learn and perform, and uses equipment that is universally available in most resource-limited settings.[3]

The stab-twist-bougie-tube technique

This requires a size 10 stab knife, a bougie, and a size 6 cuffed tracheal tube. The steps for performing a surgical cricothyroidotomy using the ‘stab, twist, bougie, tube’ technique are shown in Figure 2. After adequate positioning and site preparation, a laryngeal handshake should be performed to locate the cricothyroid membrane using the non-dominant hand of the airway operator. Following this, a bold horizontal stab (perpendicular to the airway) is given through the cricothyroid membrane using the dominant hand with the cutting edge facing the operator. The blade is then rotated by 90 degrees within the incision, with the cutting edge moving caudally away from the operator. The knife is then pulled towards the operator by a few millimetres to create space for introduction of a bougie along the side of the knife. The bougie with its coude tip is introduced up to 7–10 cm into the trachea. The knife is removed and a size six cuffed tracheal tube is inserted over bougie into the trachea till the proximal part of cuff disappears (approximately three centimetres in the trachea). The bougie is then withdrawn and the tracheal tube position is confirmed with EtCO₂ after ventilation following inflation of the cuff. Check the presence of bilaterally equal breath sounds. Hold the tube until it is secured to the skin. Haemostasis at the incision site should be achieved. Perform tracheal suction if required. An x-ray chest should be performed to exclude endobronchial intubation or a pneumothorax.

Figure 2.

Steps for performing a surgical cricothyroidotomy using the ‘stab, twist, bougie, tube’ technique

Needle cricothyroidotomy

This technique requires insertion of cannula 12-14 G through a cricothyroid membrane. Because of familiarity with the Seldinger technique, anaesthesiologists often prefer this technique over the surgical technique.[80] However, it has been found to be associated with longer time to establish ventilation and higher procedural difficulties.[81] For effective ventilation through a narrow bore cannula, an unobstructed upper airway and a pressure-regulated jet ventilation device are required, which may not be universally available. Jet ventilation is associated with breath stacking, barotrauma, catheter kinking, and malposition, leading to subcutaneous emphysema. As it is not a definitive airway, the risk of aspiration is present. The Ventrain^TM (Ventinova Medical) allows active expiration though the narrow bore cannula, which may reduce the incidence of barotrauma. Case reports and animal studies have shown promising results of this new technology in this challenging situation.[82,83]

Wide-bore cannula technique

This technique involves the use of commercially available kits. The wide bore cannula allows ventilation with conventional methods (self-inflating bag, breathing circuits). Most of the devices have a cuff which protects the airway and improves the ventilation. They employ either cannula over trocar technique or Seldinger technique for the placement of the tube across the cricothyroid membrane. Lack of universal availability and cost are major limiting factors for the usage of wide bore cannula commercial kits.

Cricothyroidotomy and associated ventilation carry a range of reported complications. Immediate complications include serious events such as hypoxia, emphysema, pneumothorax, vocal cord injury, needle dislodgement or kinking, bleeding, and perforation of the trachea, or oesophagus. However, it is crucial to balance these potential risks against the life-threatening consequences of failing to oxygenate the patient if cricothyroidotomy is not performed.

DESCRIPTION OF ALGORITHM FOR MANAGEMENT OF UNANTICIPATED DIFFICULT AIRWAY UNDER GENERAL ANAESTHESIA IN ADULTS

The AIDAA adult algorithm [Figure 3] provides guidance for management of an unanticipated difficult airway in an adult when the primary airway plan fails following induction of general anaesthesia. The primary airway plan may include tracheal intubation, SGA use, use of a facemask, and total intravenous anaesthesia with oxygen supplementation using any of the oxygen delivery devices including the use of high-flow nasal oxygen.

Figure 3.

Algorithm for the management of unanticipated difficult airway in adults under general anaesthesia

It is important to remember that while following any step in the algorithm, if the oxygen saturation is not maintained or begins to fall rapidly or bradycardia develops, any step may be bypassed, and it may be necessary to proceed directly to an emergency cricothyrotomy.

Primary airway plan

If the primary airway plan is successful, one must continue as planned. By “successful”, we mean that adequate ventilation is maintained and the SpO₂ ≥95. Call for help if any difficulty is encountered during airway management.

Call for help: Declare Code D

The call for help should be done when the first difficulty in airway management is encountered. Declare “Code D” immediately. AIDAA proposes, “Code D’, as the hospital emergency code to indicate that the patient has a difficult airway and immediate assistance and intervention is needed.[13] In case this has been missed or help has not arrived, one should call for help at any stage while managing an unanticipated difficult airway. Help of an experienced airway operator should be sought, if available. Refer to the “call for help” section above for details.

Maintain depth of anaesthesia

Maintain optimal depth of anaesthesia throughout the airway rescue process to prevent awareness and increase the chances of successful ventilation with the intended airway device.

Continue nasal oxygen

Apnoeic oxygenation during intubation is beneficial to reduce the risk of desaturation (Best Practice Statement). Refer to Table 1, Research question 5, and Appendix 5 for details. Nasal oxygenation using 15 L/min of oxygen through a nasal cannula or THRIVE should be continued throughout the airway rescue if feasible to prevent hypoxemia.

Table 1.

Summary of recommendations and best practice statements

Clinical Research Question	Recommendation/Best practice statement	Type of statement	Strength of recommendation	Level of evidence (LOE)
Does videolaryngoscopy improve the success rate of intubation compared to direct laryngoscopy?	Videolaryngoscopy improves the success rate of intubation compared to direct laryngosopy and is recommended to be used as a primary device or in rescue situations whenever expertise is available	Recommendation	1	A
Does the use of a bougie or stylet improve intubation success following a failed first attempt at intubation?	A bougie may be considered to improve intubation success with a Macintosh blade laryngoscope	Best Practice Statement	2b	C-LD
	Use of a stylet can be beneficial to improve intubation success with a hyper-angulated videolaryngoscopes.	Best Practice Statement	2a	B-R
Does apnoeic oxygenation during intubation reduce the risk of desaturation?	Apnoeic oxygenation during intubation can be beneficial to reduce the risk of desaturation.	Best Practice Statement	2a	B-R

Consider interchanging between the three devices

When the primary airway plan fails, one of the three airway devices (tracheal tube, SGA, or face mask) should be immediately used to establish effective ventilation and oxygen saturation. Either of the three devices may be used initially. However, one should rapidly move to an alternate device until adequate ventilation and SpO₂ are achieved. There is no hierarchy between the three devices. The bidirectional arrows in Figure 3 clearly show that one could move to either of the two alternate devices. The concept of interchanging between the three airway devices is used in the vortex approach, a cognitive aid used to manage a failed airway during an emergency situation.[22]

Improve the chances of successful ventilation

Repeatedly performing the same actions at each airway attempt is less likely to increase success. The airway operator should consider optimising the position and changing the tools (including the size or type of device), technique, or airway operator to improve the chance of successful ventilation. Neuromuscular blockade should be administered to improve mask ventilation when difficulty with mask ventilation is encountered in adult patients (Best Practice Statement). Refer to Table 2 and Appendix 7 for details.

Table 2.

Expert consensus statements using Delphi methodology

Clinical Question	Expert Consensus Statement	Consensus (%)
Should neuromuscular blockade be administered when difficulty with mask ventilation is encountered in adult patients?	Neuromuscular blockade should be administered to improve mask ventilation when difficulty with mask ventilation is encountered in adult patients.	96%
At what oxygen saturation (SpO2) should laryngoscopy be re-attempted following a failed intubation in adult patients?	Laryngoscopy should be re-attempted following a failed intubation only when the oxygen saturation (SpO2) ≥95% in adult patients.	96%
What is the maximum number of attempts at tracheal intubation that should be permitted to limit airway management-related complications in adult patients?	A maximum of three attempts at tracheal intubation that should be permitted to limit airway management-related complications in adult patients.	87%
What is the maximum number of attempts at supraglottic airway (SGA) insertion that should be permitted to limit airway management-related complications in adult patients?	A maximum of three attempts at supraglottic airway insertion should be permitted to limit airway management-related complications in adult patients.	100% *
Which cricothyroidotomy technique should be performed when there is complete ventilation failure in adult patients?	A surgical cricothyroidotomy should be performed when there is complete ventilation failure in adult patients.	91%

*This statement achieved consensus through a majority vote by the Steering Committee members

Use of a videolaryngoscope and adjuncts such as a bougie or stylet should be considered to improve the chances of intubation success. Videolaryngoscopy is recommended as the primary device or in a rescue situation when expertise is available (IA Recommendation) to improve the success rate of tracheal intubation. Refer to Table 1, Research question 1, and Appendix 1 for details. A bougie may be considered to improve intubation success with a Macintosh blade laryngoscope (2b Recommendation). Use of a stylet is beneficial to improve intubation success with hyper-angulated videolaryngoscopes (2a Recommendation). Refer to Table 1, Research question 4, and Appendix 4 for details on the use of a bougie and stylet during failed intubation.

Limit device attempts

Repeated attempts at laryngoscopy or SGA insertion can result in airway trauma, increasing the risk of progressing to a ‘cannot ventilate’ situation. There is limited evidence for the maximum number of attempts that should be undertaken at tracheal intubation or SGA insertion to limit complications. Airway guidelines recommend anywhere between a maximum of 2 and 4 attempts at each device.[1,19] The vortex approach suggests a maximum of 3 attempts with each device.[22] However, since mask ventilation is non-invasive, multiple attempts may be acceptable. Nevertheless, an exit strategy is required to stop attempts with the three devices and proceed to emergency cricothyroidotomy. Therefore, we suggest a maximum of up to three failed attempts at each (rather than 3 attempts), that is, at tracheal intubation, SGA insertion, and mask ventilation (expert consensus statement). Details are available in Table 2, Research questions 2 and 3, and Appendices 2, 3, and 7.

Keep track of time and SpO₂

The airway operator may lose track of time during stressful situations and get fixated with repeating the same task (fixation errors).[1,20] Therefore, it is important that a member of the team keeps track of the time and verbalises this to the team at regular intervals. This will help alert the airway operator and team of the time elapsed, to help consider proceeding to alternate rescue techniques.

It is important to keep track of the SpO₂ throughout the rescue process. Laryngoscopy should be re-attempted following a failed intubation only when the oxygen saturation (SpO₂) ≥95% in adult patients (expert consensus statement). Refer to Table 2 and Appendix 7 for more details. A maximum of three attempts is permitted, provided the SpO₂ remains ≥95%. Mask ventilation should be performed between attempts if feasible to improve saturation. Hypoxia typically begins when SpO₂ falls below 90% (corresponds roughly to an arterial oxygen tension of <60 mmHg). The rationale for using a higher threshold is to avoid even mild hypoxia (SpO₂ 91%–94%), if feasible. In addition, there is usually a lag time with pulse oximeters, which may lead to recording a higher SpO2 value than the actual value at that time.

Successful ventilation and oxygenation

If tracheal intubation is successful, confirmation of tracheal tube position should be done using waveform capnography (refer to section on confirmation of tracheal tube position).

If an SGA has been successfully inserted with effective ventilation and oxygenation achieved, the airway operator has time to think about the further airway management plan. The safest option will be to awaken the patient if the surgery is not an emergency. If it is an emergency procedure or continuation of the procedure is considered safe using an SGA, one may proceed. If the SGA insertion was to rescue a failed tracheal intubation, one must keep in mind that any trauma during attempts at tracheal intubation may produce airway oedema which may worsen during the course of the surgery. If the procedure is considered unsafe to be continued using an SGA, intubation through the SGA using a flexible bronchoscope should be performed if the equipment and expertise are available. In remote locations, performing a tracheostomy may be the safest option, if the procedure is considered unsafe to be continued using an SGA, and tracheal intubation is not possible.

Complete ventilation failure

Complete ventilation failure is defined as a situation where ventilation using a tracheal tube, SGA, and face mask have all failed after giving the best attempt, even if oxygenation may be maintained. This should be the trigger to perform emergency cricothyroidotomy (refer to section on complete ventilation failure for details). Nasal oxygen and efforts at rescue ventilation should continue.

Call for additional help

Call for additional help when there is complete ventilation failure, and proceed to perform emergency cricothyroidotomy. An additional person who has not been part of the process may be able to think more rationally and perform better in this stressful situation, in addition to being an extra helping hand.

Emergency cricothyroidotomy

Most airway guidelines recommend performing emergency cricothyroidotomy when faced with a complete ventilation failure-like situation. However, even in the most experienced hands, the success of this technique is only 35%, highlighting the urgent need for alternative or complementary rescue strategies when such situations arise.[4] Although current difficult airway guidelines recommend immediate transition to emergency invasive airway access once a complete ventilation failure-like scenario has occurred, this approach assumes reliable execution, which is often not the case in high-stress settings. The prompt reversal of neuromuscular blockade to restore spontaneous ventilation using sugammadex is one such strategy. However, this may be considered only if a steroid neuromuscular blocking agent has been used, there is no hypoxaemia, and a high dose of sugammadex (16 mg/kg) is readily available. It must be noted that this is not always successful and takes time. Therefore, performing emergency cricothyroidotomy should be the default technique.

In 2016 Guidelines, AIDAA suggested performing either a needle or a surgical cricothyroidotomy based on familiarity and availability of equipment. However, in the AIDAA 2025 guidelines, we suggest that a surgical cricothyroidotomy should be adopted when there is complete ventilation failure in adult patients (expert consensus statement). Refer to Table 2, Research question 6, and Appendices 6 and 7. Considering the universal availability of a stab knife, bougie, and size six tracheal tube, there was consensus among the airway experts in the Delphi process to choose a surgical cricothyroidotomy as the preferred technique.

While surgical cricothyroidotomy is the preferred technique, needle cricothyroidotomy with pressure-regulated jet ventilation or wide bore cannula cricothyroidotomy sets may be used if the equipment and experience to use it are available. Surgical tracheostomy may be considered if a surgeon experienced to perform the procedure is available at site. Since cricothyroidotomy is not performed in routine anaesthesia practice, training in the procedure and retention of skills remain a challenge and need prioritisation.

Post-procedure plan

Once oxygenation has been established, a definitive airway plan should be formulated to ensure patient safety. If airway oedema is suspected, it should be treated using steroids and nebulisation with adrenaline, if feasible. It is necessary to follow up these patients for any immediate or late complication and treat them accordingly. A complete airway examination may be required to evaluate any airway injury. A cricothyroidotomy should be converted to a tracheostomy at the earliest to minimise the risk of tracheal stenosis.

Counselling the patient and/or the family after the event and documentation in the case notes of the airway difficulty faced and management strategies employed are important. In addition, a ‘difficult airway alert form’[13] should be filled by the attending physician and a copy must be given to the patient/surrogate and maintained in the department for future reference.[13]

Failed intubations or any airway-related morbidity or mortality should be discussed among the team members immediately after the event to assess their well being and ensure that they feel supported. At a later time, a proper debriefing should be performed to improve team performance and prevent adverse events in future.

SUMMARY OF RESEARCH QUESTIONS

Research question 1: Does videolaryngoscopy improve the success rate of intubation compared with direct laryngoscopy? Appendix 1[84,85,86,87,88,89,90,91,92,93,94,95]

Summary: A total of 283 abstracts were reviewed. All retrieved article citations were entered into the reference management software program, Rayyan, where duplicates were removed and the remainder were screened for eligibility. Search results were independently screened by two authors using the title and the abstract. Twelve articles were included for final review by AS and RK, encompassing eight systematic review and meta-analysis of randomised trial and four randomised controlled trials (RCTs).

Key findings from the analysis highlight that videolaryngoscopy (VL) demonstrates superior performance compared to direct laryngoscopy (DL) in adult patients, supported by multiple studies with high levels of evidence. Systematic reviews and meta-analyses (e.g., Hansel J et al., 2022 (Grade A)[85]; de Carvalho CC et al., 2022 (Grade A)[86]), rated as Level A evidence, confirm that VL improves first-pass success (FPS) rates, reduces failed intubation attempts, and enhances glottic visualisation, as indicated by improved Cormack-Lehane (CL) grading and percentage of glottic opening (POGO). RCTs (e.g., Kriege et al., 2024 (Grade B-R)[87]; Gamze Küçükosman et al., 2024 (Grade B-R)[88]), rated as Level B evidence, demonstrate that devices like McGrath VL and C-MAC VL outperform DL for both routine and difficult intubations. Additionally, VL devices have proven effective as rescue tools following failed DL attempts, with studies [e.g., Hansel J et al., 2022 (Grade A)[85]] showing reduced rates of esophageal intubation and hypoxia. Hyper-angulated blades like GlideScope and channeled devices such as Airtraq offer further advantages in achieving successful intubation in difficult airway scenarios [Carron M et al., 2021 (Grade A)[89]]. These findings establish VL as a reliable primary and rescue device for managing routine and difficult intubations. It is essential to have proper training in VL devices and techniques to maximise first pass success and minimise complications across a range of devices.

VL is the preferred device for tracheal intubation due to its higher success rates, improved glottic visualisation, and reduced complications such as hypoxemia and esophageal intubation. It is particularly effective for managing difficult airways. VL is suitable for routine intubations and serves as a dependable rescue option in difficult airway scenarios, making it an essential tool for safer and more efficient intubations in clinical practice. Ensure adequate training and practice with the specific type of device, especially for managing difficult or rescue airways.

Recommendation: Videolaryngoscopy improves the success rate of intubation compared to direct laryngosopy and is recommended to be used as a primary device or in rescue situations whenever expertise is available. (Level of evidence: A, Class of recommendation: I)

Research question 2: What is the maximum number of attempts at tracheal intubation that should be permitted to limit airway management-related complications in adult patients? Appendix 2[87,96,97,98,99,100,101,102,103,104]

Summary: A total of 114 abstracts were reviewed. Ten studies were included in the final review by AP and AS. Several studies indicate that repeated intubation attempts may lead to increased airway trauma, edema, desaturation, and haemodynamic complications. Kriege et al. (2024, Level B-R),[87] in an RCT, reported improved outcomes when intubation was successful within two attempts during induction. Mort (2004, Level C-LD)[97] found that more than three attempts during emergency intubations outside the OR were associated with significantly higher rates of airway and cardiovascular complications. Similarly, Inoue et al. (2019, Level C-LD)[98] observed a rise in post-intubation hypertension when three or more attempts were made.

A systematic review and meta-analysis by Teshome et al. (2024, Level A)[99] examined post-operative sore throat (POST) in OR patients and identified repeated intubation attempts as a contributing factor, suggesting a cumulative risk of airway irritation and injury. Additional observational studies, such as those by Kim (2014, Level C-LD)[100] and Sakles (2013, Level C-LD),[101] reinforce the importance of first-pass success, linking it to fewer adverse events in emergency settings.

Although these studies support minimising intubation attempts, the level of evidence is generally low, with limited randomised data and inconsistent definitions of harmful attempt thresholds. Given the variability in current data and the absence of large-scale prospective studies, a Delphi consensus process among airway experts is recommended to define an acceptable limit on intubation attempts and to guide standardised clinical practice. Delphi Survey results: Appendix 7

Expert consensus statement: A maximum of three attempts at tracheal intubation should be permitted to limit airway management-related complications in adult patients.

Research question 3: What is the maximum number of attempts at supraglottic airway (SGA) insertion that should be permitted to limit airway management-related complications in adult patients? Appendix 3[105,106,107,108,109,110,111,112,113,114,115,116]

Summary: A total of 181 abstracts were reviewed by RK and AS. Twelve studies were included in the final review. Review of studies showed number of attempts as primary of attempts as secondary objectives, but most of them had not identified our research question of linking number of attempts with trauma or complications. Most studies have identified attempts to successful insertion of a SGA. In a few studies, repeated attempts beyond that are linked to increased risks such as sore throat, trauma, or the need for more invasive airway management like tracheostomy. While all studies support reducing the number of attempts, only Klementova et al. (2021, Level B-NR)[106] explicitly defined a maximum of three attempts, but have not identified the trauma with it. Notably, Ebied et al. (2017, B-R)[107] allowed up to three attempts in their protocol and found more trauma with additional tries.

Other high-quality RCTs provide additional support. For instance, Hattori et al. (2016, Level B-R)[108] showed that muscle relaxants made insertions easier and reduced complications. Lee et al. (2024, Level B-R)[109] found that turning the head improved first-attempt success rates. Studies by Joly et al. (2014, Level B-R),[110] Yildiz et al. (2007, Level B-R),[111] Nishiyama et al. (2012, Level B-R),[112] Polat et al. (2015, Level B-R),[113] Farbood et al. (2023, Level B-R),[114] Ishio et al. (2016, Level B-R),[115] and Ebied et al. (2017, Level B-R)[107] consistently showed that most SGAs are placed successfully on the first or second try, and that complications increase with further attempts. Notably, Ebied et al. allowed up to three attempts in their protocol and still found more trauma with additional tries.

Two observational studies also support limiting attempts. Wharton et al. (2008, Level C-LD)[116] found more airway trauma with repeated efforts, and Hernandez et al. (2018, Level C-LD)[105] showed that trauma patients needing multiple SGA attempts were more likely to end up with a tracheostomy.

In short, although all studies favour reducing SGA attempts, only one clearly defines a limit, and the overall level of evidence is moderate—not high. Therefore, a Delphi survey involving expert consensus is recommended to formally define a safe maximum number of SGA insertion attempts. Delphi survey results: Appendix 7.

Expert consensus statement

A maximum of three attempts at SGA insertion should be permitted to limit airway management-related complications in adult patients.

Research question 4: Does the use of a bougie or stylet improve intubation success following a failed first attempt at intubation? Appendix 4[1,117,118,119,120,121,122,123,124,125,126,127]

Summary: A total of 538 abstracts were reviewed by two authors, AP and AS, and 13 articles were included in the final review. While substantial evidence supports the use of the bougie with standard Macintosh blades for both direct and video laryngoscopy (DL and VL), the choice of adjuncts like stylets or bougies should be tailored to specific clinical scenarios. Law JA (2021, C-EO)[1] recommended the use of bougies and stylets based on consensus guidelines, emphasising their utility in unconscious patients. Jaber S (2021, B-R)[118] demonstrated in a randomised trial that using a stylet with a Macintosh laryngoscope significantly increased first-pass success (78.2% vs. 71.5%). Xu X (2024, C-LD)[119] demonstrated a bougie-first approach with VL offered higher first-attempt success rates in a simulated manikin study (98.5% compared to 86.2% for ETT with stylet). The Endotrol tube, while effective, has longer intubation times than alternatives like GlideRite (Cattano D, 2012, B-R).[120]

Videolaryngoscopes and stylets are beneficial for obese patients, with devices like the Frova catheter offering superior performance in specific scenarios (Henderson JJ, 2004, C-EO).[121] Bougie-first approaches, reusable bougies, and aerosol box intubation with stylets also lead to better outcomes (Puthenveettil N, 2023, B-R; Marfin JV, 2003, B-R).[122,123] Lighted stylets and Truflex articulating stylets enhance intubation success in direct and videolaryngoscopy procedures, respectively (Xu X, 2024, C-LD; Ozdemirkan A, 2022, C-LD).[119,124]

While evidence strongly supports the bougie in combination with standard Macintosh blades for DL and VL, critical nuances exist. Studies indicate that the bougie improves first-attempt success by securely guiding the endotracheal tube into the trachea during both Macintosh DL and VL. Conversely, for hyper-angulated VL blades, a stylet offers greater success due to its ability to accommodate the blade’s geometry, facilitating easier tube manipulation and positioning. Thus, the choice of intubation adjunct should be guided by the type of laryngoscope blade and airway challenge, ensuring the most effective strategy for each clinical scenario.

Best Practice Statement: A bougie may be considered to improve intubation success with a Macintosh blade laryngoscope. (Strength of recommendation: 2b, Level of evidence: C-LD).

Best Practice Statement: Use of a stylet can be beneficial to improve intubation success with hyper-angulated videolaryngoscopes. (Strength of recommendation: 2a, Level of evidence: B-R).

Research question 5: Does apnoeic oxygenation during intubation reduce the risk of desaturation? Appendix 5.[128,129,130,131,132,133,134,135,136,137,138,139,140]

Summary: A total of 591 abstracts were screened to retrieve 24 full-text articles by SS and AS. Thirteen articles were included in the final review. Apneic oxygenation (AO) is a valuable technique that helps maintain oxygen levels during tracheal intubation in the operating room. The majority of finally included 13 studies have shown that different methods of AO—like high-flow nasal oxygen (HFNO), nasal cannulas, nasopharyngeal catheters, and even buccal oxygen delivery—can effectively prolong the safe apnoea time in patients. Most research has focussed on high-risk groups, including obese patients, pregnant women, and those undergoing major surgeries.

Abdelmoneim et al. (2023, AHA Level B-R)[129] found that using nasal oxygen at 10 litres per minute during intubation significantly improved oxygen levels in obese pregnant women. Preya et al. (2023, B-R)[130] showed that using a nasal catheter at 10 L/min reduced the drop in oxygen levels during a 90-second apnea period in patients undergoing laparotomy (abdominal surgery). Pierpoint et al. (2023, B-R)[131] reported that using a nasopharyngeal catheter at 18 L/min significantly extended safe apnea time for obese patients. Geng et al. (2022, B-R)[132] compared two methods of oxygen delivery (a modified nasopharyngeal airway and HFNO) and found both were equally good at keeping oxygen levels stable for up to 20 minutes. Schutzer-Weissmann et al. (2023, B-R)[133] indicated that HFNO at 35–70 L/min was as effective as using a face mask at 15 L/min for maintaining oxygen saturation in obese patients. One interesting finding from Heard et al. (2017, B-R)[134] showed that delivering oxygen through a buccal mucosa oxygenation at 10 L/min could delay significant drops in oxygen levels for up to 750 seconds in obese patients. Wong et al. (2019, B-R)[135] highlighted that combining HFNO for pre-oxygenation and AO led to longer times before oxygen levels dropped in severely obese patients.

While many studies support the benefits of AO, not all results were positive. For example, Bright et al. (2023, A)[136] found no significant difference in oxygen drop rates between HFNO and face masks in obese patients, even though the apnea time was longer. Similarly, Lyons et al. (2024, B-R)[137] and Hanouz et al. (2019, B-R)[138] found no advantages of HFNO over traditional methods in terms of carbon dioxide clearance and oxygen targets.

Overall, despite a few mixed results, the majority of evidence supports the use of apneic oxygenation during intubation, particularly in high-risk patients. When HFNO is available, it is the preferred option. In settings without HFNO, simpler methods like nasal prongs or nasopharyngeal catheters that provide 10–15 L/min of oxygen are still highly effective. Incorporating AO into the protocols for intubation enhances safety, delays oxygen drops, and improves overall airway management during anesthesia.

Best Practice Statement: Apnoeic oxygenation during intubation can be beneficial to reduce the risk of desaturation. (Class of Recommendation: 2a, Level of Evidence: B-R)

Research question 6: Is surgical cricothyroidotomy preferred over other techniques of emergency cricothyroidotomy? Appendix 6.[4,77,78,79,80,81,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157]

Summary

A total of 169 abstracts were reviewed by RK and AS. Twenty four articles were included in the final review. A review of the literature highlights various techniques for emergency cricothyroidotomy, with a focus on surgical cricothyroidotomy. While the evidence underscores the advantages of surgical techniques in terms of success rates and procedural efficiency, it is crucial to acknowledge that most studies are conducted in simulation-based settings, including manikin and cadaveric models (level C-LD). This inherently limits the quality of evidence and its applicability to real-world emergency scenarios.

Surgical cricothyroidotomy, particularly the scalpel-bougie method, has consistently demonstrated higher success rates in controlled settings. Duggan et al. (2018)[79] reported a first-attempt success rate of 82% (37/45) for scalpel-bougie cricothyroidotomy, compared to 60% for surgical cricothyroidotomy (15/25) and lower rates for cannula-based methods. Additionally, Schober et al. (2009)[78] found that anatomical-surgical techniques achieved higher success rates, faster tracheal tube insertion times, and fewer complications compared to puncture techniques, especially among inexperienced personnel. In a cadaver-based study by Schaumann et al. (2005),[142] surgical cricothyroidotomy exhibited longer times to tracheal puncture (P < 0.01) and first ventilation (P < 0.001) during training, but its role in skill acquisition was emphasised.

Alternative approaches, including needle and wire-guided cricothyroidotomy, remain common in certain scenarios. Wong et al. (2014)[143] reported that in a survey of 955 anaesthesiologists, 39% preferred wire-guided cricothyroidotomy as the first-choice surgical airway in “cannot intubate, cannot ventilate” (CICV) situations, with 28% favoring intravenous catheter cricothyroidotomy and 23% deferring to tracheostomy. However, needle-based techniques often demonstrate slower times to ventilation and higher procedural difficulties. For example, Kanji et al. (2012)[81] found that an incision-first modification was significantly faster than the traditional needle-first approach (median 53 seconds vs. 90 seconds, P < 0.001), highlighting the limitations of needle-first methods.

Training programs focussing on surgical cricothyroidotomy have shown promising results in skill improvement. Asselin et al. (2021)[144] described a cadaver-based workshop where 97% of surveyed participants (n = 32) reported improved confidence and skills in surgical cricothyroidotomy, emphasising the value of repetitive practice. Additionally, Schober et al. (2009)[78] demonstrated that anatomical-surgical techniques had fewer complications and higher efficiency compared to puncture-based methods in simulated emergencies.

Despite the promising findings, the low quality of evidence from simulation-based studies highlights the need for caution in translating these results to clinical practice. Nevertheless, the evidence supports prioritising surgical cricothyroidotomy in training programs and emergency airway guidelines, given its higher reliability and effectiveness under controlled conditions. Because of low-quality evidence, a Delphi survey is advisable. Delphi survey results: Appendix 7

Expert consensus statement

A surgical cricothyroidotomy should be performed when there is complete ventilation failure in adult patients.

GUIDELINE SUMMARY

The AIDAA 2025 adult guideline provides a comprehensive structured approach for the management of an unanticipated difficult airway under general anaesthesia. It includes guidance for a difficult or failed supraglottic airway insertion, tracheal intubation, face mask ventilation, or other strategies commonly used as part of the primary airway plan under general anaesthesia, not restricting to guidance following a failed intubation. A systematic literature search, data extraction, and evidence synthesis was conducted for the six PICO questions drafted by the Steering Comminate, and recommendations were categorised according to the American Heart Association (AHA) Class of Recommendation and Level of Evidence.[11] Where evidence was absent or weak, the Steering Committee initiated a robust Delphi process to reach consensus (75% and above) among airway experts to provide guidance.

If the primary airway plan fails, activate ‘Code D’ as the hospital emergency code to call for help. Airway rescue should then be attempted with any of the three devices (tracheal tube, SGA, or face mask), switching promptly between them as needed, with no hierarchy, until effective ventilation and adequate SpO₂ are achieved. Emphasis has been laid on limiting device attempts and proceeding with the next attempt at laryngoscopy only if the SpO2 remains ≥95%. AIDAA suggests a maximum of up to 3 failed attempts with tracheal intubation, SGA insertion, and mask ventilation. Nasal oxygen delivery during airway rescue, keeping track of SpO2 and the time lapsed, have been emphasised. Complete ventilation failure (ventilation using a tracheal tube, SGA, and face mask have all failed, even if oxygenation may be maintained) is the trigger to perform an emergency cricothyroidotomy. A call for additional help is advised when there is complete ventilation failure. Surgical cricothyroidotomy is suggested as the preferred technique over others for emergency cricothyroidotomy. A post-procedure plan including team debriefing, team support, patient and family counselling, and documentation has been included.

In addition to the management of an unanticipated difficult airway in adults, guidance on risk assessment for airway management, pre-oxygenation, and optimisation of tracheal intubations including proper positioning, choice of induction agent and NMBA, choice of laryngoscope and other adjuncts, apnoeic oxygenation, and confirmation of tracheal tube position using waveform capnography are provided in the guidelines. Optimising SGA use and mask ventilation have also been discussed. The timing and method to call for help and the use of critical language such as complete ventilation failure and emergency cricothyroidotomy during airway management along with the rationale for their use have been discussed.

Presentation at conferences/CMEs and abstract publication

Nil.

Study data availability

De-identified data may be requested with reasonable justification from the authors (email to the corresponding author) and shall be shared upon request.

Disclosure of use of artificial intelligence (AI)-assistive or generative tools

The AI tools or language models (LLM) have not been utilised in the manuscript, except that software has been used for grammar corrections and references.

Declaration of use of permitted tools

The tables and figures are self-made and not copyrighted.

Author contributions

SNM served as the lead for the AIDAA 2025 adult guidelines. APS served as the project administrator and led the literature review process. SNM, APS, VR, PK, SRS, RG, SMA, JRD and JVD served as core committee members of the adult Guideline Subcommittee. The core committee members were involved the conceptualisation and design of the guidelines, drafting the PICO questions, conducting the literature search, drafting and editing the manuscript, and critical review and approved the final version of the manuscript. AP, DKP, SLS, RK and SD as adult Guideline Subcommittee members provided specialised inputs in the development of the recommendations, contributed to the literature review, reviewed the manuscript for accuracy and relevance, and approved the final version. All authors contributed to reviewing and editing of the manuscript for intellectual content and are responsible for the content of this guideline.

Conflicts of interest

Dr Amit Shah- inventor of Patwashahi video laryngoscope (non-commercial), designer of HFNO device HuFlo2. Dr Apeksh Patwa-inventor of Patwashahi video laryngoscope (non-commercial), designer of HFNO device HuFlo2. Dr Rakesh Garg, Dr Pankaj Kundra, Dr Sheila Nainan Myatra, Dr Syed Moied Ahmed, and Dr Jeson R Doctor, who are co-authors of this manuscript, are editors of this journal. They were not involved in the decision-making process, and an independent editor handled this manuscript. Other authors declare that they have no conflicts of interest.

Supplementary material

This article has supplementary material and can be accessed at this link. Supplementary Material at http://links.lww.com/IJOA/A46.

APPENDICES

Appendix 1

Research Question 1: Does videolaryngoscopy improve the success rate of intubation compared with direct laryngoscopy?

• P - Adult patients undergoing intubation

• I - Videolaryngoscopy

• C - Direct laryngoscopy

• O - Intubation success, desaturation, Duration of intubation, trauma

supplementary Table 1a.

Concept Table for Research Question Does- Does videolaryngoscopy improve the success rate of intubation when compared with direct laryngoscopy?

Research question	Concept 1	Concept 2	Concept 3	Concept 4	Concept 5	Concept 6	Concept 7
Key concepts	Adults	Intubation	GA	Direct laryngoscopy	Videolaryngoscopy	Video laryngoscopes (VL) C-MAC, GlideScope, King Vision, McGrath	Classification 1. Macintosh type of VL, 2. Flyperagulated VL, 3. Channel type of VL**
Free text terms/ natural language terms (synonyms, UK/ US terminology, medical/laymen’s terms, acronyms/ abbreviations, drug brands, more narrow search terms) Consider: phrase searching, proximity operators, truncation, wildcards, field qualification (e.g. textword)	“adult” “adults” “adult’s”	“intubate”[AII Fields] OR “intubated”[AII Fields] OR “intubates”[AII Fields] OR “intubating”[AII Fields] OR “intubation”[MeSFI Terms] OR “intubation”[AII Fields] OR “intubations”[AII Fields] OR “intubator”[AII Fields] OR “intubator s”[AII Fields] OR “intubators”[AII Fields]	Anesthesia, General/methods* Anesthesia* Anesthesia, Obstetrical/ methods* Anesthesia, Obstetrical* Anesthesias, General General Anesthesia General Anesthesias	“direct laryngoscopy”[AII Fields] Direct laryngoscopy Direct laryngoscope Traditional laryngoscopy Conventional laryngoscopy (“miller laryngoscope”[AII Fields] OR “miller laryngoscopes”[AII Fields] OR “miller laryngoscopy”[AII Fields] OR “miller laryngoscope blade”[AII Fields]) AND ((humans[Filter]) AND (english[Filter]))	“videolaryngoscopy”[AII Fields] Videolaryngoscopy Video laryngoscopy Video-assisted laryngoscopy Video Assisted Techniques and Procedures Video Assisted Techniques Techniques, Video Assisted Technique, Video Assisted Video Assisted Technique Recordings, Video Recording, Video Video Recordings Audiovisual Recording Audiovisual Recordings Recording, Audiovisual Videorecording Videorecordings	“C-Mac” “glidescope”[AII Fields] “king vision”[AII Fields] (mcgrath [tiab]) NOT (mcgrath [auth]) ((Macintosh [tiab]) OR	(“Macintosh laryngoscope”)) NOT (Macintosh [auth]) “hyperangulated”[AII Fields] "Nothing specific is coming for Channel type of VL
Controlled vocabularyterms/ Subject terms (MeSH terms, Emtree terms) Consider: explode, major headings, subheadings	“adult”[MeSH Terms]	“Intubation, lntratracheal”[Mesh]	“Anesthetics, General”[Mesh] “Anesthesia”[Mesh] “Anesthesia, Obstetrical”[Mesh]	“Laryngoscopy”[MeSFI] “Laryngoscopes”[Mesh]	“Video-Assisted Techniques and Procedures”[Mesh] “Video Recording”[Mesh] Laryngoscope “Laryngoscopes”[Mesh] “Laryngoscopy”[Mesh]

Search String

PubMed: 135 results

((“adult”[MeSH Terms] OR “adult”[All Fields] OR “adults”[All Fields] OR “adult s”[All Fields]) AND (“intubate”[All Fields] OR “intubated”[All Fields] OR “intubates”[All Fields] OR “intubating”[All Fields] OR “intubation”[MeSH Terms] OR “intubation”[All Fields] OR “intubations”[All Fields] OR “intubator”[All Fields] OR “intubator s”[All Fields] OR “intubators”[All Fields]) AND (“videolaryngoscopies”[All Fields] OR “videolaryngoscopy”[All Fields]) AND (“direct”[All Fields] OR “directed” [All Fields] OR “directing” [All Fields] OR “direction” [All Fields] OR “directional”[All Fields] OR “directions”[All Fields] OR “directivities”[All Fields] OR “directivity”[All Fields] OR “directs”[All Fields] OR ((“conventional”[All Fields] OR “conventionals”[All Fields]) AND (“laryngoscopy”[MeSH Terms] OR “laryngoscopy”[All Fields] OR “laryngoscopies”[All Fields])) OR ((((“Macintosh”[Title/Abstract] OR “Macintosh laryngoscope”[Title/Abstract]) NOT Macintosh[Author]) OR “hyperangulated”[All Fields]) AND (“humans”[MeSH Terms] AND 2000/01/01:2024/12/31[Date - Publication] AND “english”[Language])) OR ((“C-Mac”[All Fields] OR “glidescope”[All Fields] OR “king vision”[All Fields] OR (“mcgrath”[Title/Abstract] NOT mcgrath[Author])) AND (“humans”[MeSH Terms] AND 2000/01/01:2024/12/31[Date - Publication] AND “english”[Language])))) AND ((humans[Filter]) AND (2000:2024[pdat]) AND (english[Filter]))

Scopus: 162 results

((adult OR adults) AND (intubate OR intubated OR intubates OR intubating OR intubation OR intubations OR intubator OR intubators) AND (videolaryngoscopy OR videolaryngoscopies) AND (direct OR directed OR directing OR direction OR directional OR directions OR directivities OR directivity OR directs OR (conventional AND laryngoscopy) OR (conventional AND laryngoscopies) OR ((“Macintosh” OR “Macintosh laryngoscope”) AND NOT AUTHOR-NAME (macintosh)) OR hyperangulated OR (“C-Mac” OR glides cope OR “king vision” OR (“mcgrath” AND NOT AUTHOR-NAME (mcgrath)))) AND PUBYEAR > 1999 AND PUBYEAR < 2025 AND LANGUAGE (english) AND PUBYEAR > 2019 AND PUBYEAR < 2025) AND (meta AND analysis) AND (videolaryngoscope) AND (videolaryngoscopy) AND (randomized AND control AND trial) AND (randomised AND control AND trial) AND (LIMIT-TO (DOCTYPE, “ar”) OR LIMIT-TO (DOCTYPE, “re”)) AND (LIMIT-TO (LANGUAGE, “English”)) AND (LIMIT-TO (EXACTKEYWORD, “Human”)) AND (LIMIT-TO (SUBJAREA, “MEDI”))

Supplementary Figure 1

PRISMA flow chart for Research Question: Does videolaryngoscopy improve the success rate of intubation compared with direct laryngoscopy?

Supplementary Table 1b.

Summary Table for included studies for Research Question- Does videolaryngoscopy improve success rate of intubation when compared with direct laryngoscopy?

Author (Year)	Journal	Type of Article	Level of Evidence (AHA)	Intervention	Supports as Primary	Supports as Rescue
McNarry P (2024)[90]	Patient Saf Surg	Cochrane Review	A	Macintosh VL vs DL Objective: Intubation success,	Yes	Not mentioned
Hansel J (2022)[85]	Br J Anaesth	Cochrane Systematic Review and Meta-analysis	A	VL vs DL Objective: Failed intubation, hypoxaemia, successful first attempt, oesophageal intubation, etc.	Yes	Yes
De Carvalho C (2022)[86]	Anaesthesia	Systematic Review and Network Meta-analysis	A	VL vs DL Objective: Risk of failed intubation, failed 1st attempt, within 2 attempts etc.	Yes	Not mentioned
Lee JH (2022)[91]	J Pers Med	Systematic Review and Network Meta-analysis	A	VL vs VL. Objective: 1st attempt success rate, glottic view, sort throat	Yes	Not mentioned
Carron M (2021)[89]	J Clin Anesth	Meta-analysis	A	GlideScope, Airtraq vs DL. Objective: Laryngoscopic view, 1 st attempt success rate	Yes	Yes
Vargas M (2021)[92]	Eur Rev Med Pharmacol Sci	Systematic Review and Meta-analysis	A	VL vs VL. Objective: 1 st attempt success rate, glottic view, sore throat	Yes	Yes
Gupta N (2021)[93]	Korean J Anesthesiol	Systematic Review and Meta-analysis	A	VL vs DL. Objective: 1 st attempt success rate, trauma, etc.	Yes	Not mentioned
Kriege A (2024)[87]	Anaesthesia	Multicentre Randomised Controlled Trial	B-R	McGrath VL vs DL. Objective: time to intubate from glottic view, attempts, glottic view etc.	Yes	Yes
Lee Y (2024)[94]	Medicina (Kaunas)	Randomised Controlled Trial	B-R	CMAC-DVL vs McCoy DL Objective: time to intubate etc	Yes	Yes
Kriege A (2023)[95]	Anaesthesia	Multicentre Randomised Controlled Trial	B-R	McGrath VL vs DL Objective: 1st attempt success rate, overall success rate, time to glottic view etc.	Yes	Yes
Küçükosman M (2024)[88]	Medicina (Kaunas)	Randomised Controlled Trial	B-R	McGrath-MAC VL vs DL Objective: glottic view, incubation time, number of attempts etc.	Yes	Not mentioned
Halder S (2022)[84]	Expert Rev Med Devices	Randomised Controlled Trial	B-R	DL vs C-MAC vs Smart Trach Objective: Time to intubate, attempts, CL Grading, etc	Yes	Not mentioned

VL=Videolaryngoscope, DL=Direct laryngoscope, CMAC=C-MAC Videolaryngoscope, DVL=Direct videolaryngoscope, LOE=Level of evidence

Appendix 2

Research Question 2: What is the maximum number of attempts at tracheal intubation that should be permitted to limit airway management-related complications in adult patients?

• P-Adult patients undergoing intubation

• I-Intubation attempts

• C-Intubation attempts

• O-Airway trauma and edema, desaturation

Supplementary Table 2a.

Concept Table for Research Question - What is the maximum number of attempts at tracheal intubation that should be permitted to limit airway management-related complications in adult patients?

Research question	Concept 1	Concept 2	Concept 3	Concept 4	Concept 5
Key concepts	Adults	Intubation	repeated	Attempt	Laryngoscopy and scope types
Free text terms/natural language terms (synonyms, UK/US terminology, medical/ laymen's terms, acronyms/ abbreviations, drug brands, more narrow search terms) Consider: phrase searching, proximity operators, truncation, wildcards, field qualification (e.g. textword)	“adult” “adults” “adult's”	“intubate”[All Fields] OR “intubated”[All Fields] OR “intubates”[All Fields] OR “intubating”[All Fields] OR “intubation”[MeSH Terms] OR “intubation”[All Fields] OR “intubations”[All Fields] OR “intubator”[All Fields] OR “intubator s”[All Fields] OR “intubators”[All Fields]	“repeatabilities”[All Fields] OR “repeatability”[AN Fields] OR “repeatable”[All Fields] OR “repeated”[All Fields] OR “repeatibility”[All Fields]	“attempt”[All Fields] OR “attempted”[All Fields] OR “attempter”[All Fields] OR “attempters”[All Fields] OR “attempting”[All Fields] OR “attempts”[All Fields	((“Direct laryngoscopy”[All Fields] OR “Direct laryngoscopy”[All Fields] OR “Direct laryngoscope”[All Fields] OR “Traditional laryngoscopy”[All Fields] OR “Conventional laryngoscopy”[All Fields] OR ((“miller laryngoscope”[All Fields] OR “miller laryngoscopes”[All Fields] OR “miller laryngoscopy”[All Fields] OR “miller laryngoscope blade”[All Fields]
Controlled vocabularyterms/ Subject terms (MeSH terms, Emtree terms) Consider: explode, major headings, subheadings	“adult”[MeSH Terms]	“Intubation, Intratracheal”[Mesh]	“Anesthetics, General”[Mesh] “Anesthesia”[Mesh] “Anesthesia, Obstetrical”[Mesh]		(“Laryngoscopy”[MeSH Terms] OR “Laryngoscopes”[MeSH Terms]))

Search String:

PubMed: 76 results

((“repeatabilities”[All Fields] OR “repeatability”[All Fields] OR “repeatable”[All Fields] OR “repeated”[All Fields] OR “repeatibility”[All Fields]) AND (“intubate”[All Fields] OR “intubated”[All Fields] OR “intubates”[All Fields] OR “intubating” [All Fields] OR “intubation”[MeSH Terms] OR “intubation” [All Fields] OR “intubations” [All Fields] OR “intubator”[All Fields] OR “intubator s”[All Fields] OR “intubators”[All Fields]) AND (“adult”[MeSH Terms] OR “adult”[All Fields] OR “adults”[All Fields] OR “adult s”[All Fields]) AND (“attempt”[All Fields] OR “attempted”[All Fields] OR “attempter”[All Fields] OR “attempters”[All Fields] OR “attempting”[All Fields] OR “attempts”[All Fields])) AND ((humans[Filter]) AND (2000:2024[pdat]))

Scopus: 102 results

(TITLE-ABS-KEY (repeatabilities OR repeatability OR repeatable OR repeated OR repeatibility) AND TITLE-ABS-KEY (intubate OR intubated OR intubates OR intubating OR intubation OR intubations OR intubator OR intubators) AND TITLE-ABS-KEY (adult OR adults) AND TITLE-ABS-KEY (attempt OR attempted OR attempter OR attempters OR attempting OR attempts)) AND PUBYEAR > 1999 AND PUBYEAR < 2025

Supplementary Figure 2

PRISMA flow chart for Research Question: What is the maximum number of attempts at tracheal intubation that should be permitted to limit airway management-related complications in adult patients?

Supplementary Table 2b.

Summary table for included studies for Research Question - What is the maximum number of attempts at tracheal intubation that should be permitted to limit airway management-related complications in adult patients?

Author (Year)	Journal	Type of Article	Level of Evidence (AHA)	Intervention/Focus	Supports Limiting Attempts	Specific Numbers /Notes
Teshome D (2024)[99]	Prev Med Rep	Systematic Review and Meta-analysis	A	Pooled POST prevalence in Ethiopian OR patients	Yes	Not specified
Kriege M (2024)[87]	Anaesthesia	Randomised Controlled Trial	B-R	Videolaryngoscope vs Direct laryngoscope in OR for RSI	Yes	Limit to 2 attempts
Ono Y (2015) [102]	J Anesth	Case Report	C-EO	Intubation complications outside OR	Yes	Not specified
Gemechu BM (2017)[103]	Pan Afr Med J	Quantitative Cross-sectional Study	C-LD	POST incidence and causes post­intubation	Yes	Not specified
Tachibana N (2015)[104]	J Anesth	Retrospective Analysis	C-LD	CICV incidence under general anaesthesia	Yes	Not specified
Nagaro T (2003)[96]	J Anesth	Retrospective Survey	C-LD	Incidence of CVCI during General Anaesthesia	Yes	Not specified
Mort TC (2004)[97]	AnesthAnalg	Prospective Evaluation	C-LD	Emergency intubation and complications vs number of attempts	Yes	Limit to 3 attempts; complications increased with more
Sakles JC (2013)[101|	Acad Emerg Med	Retrospective Analysis	C-LD	First-pass success vs adverse events in ED intubations	Yes	Not specified
Kim J (2014)[100]	Resuscitation	Retrospective Analysis	C-LD	OHCA ED intubation success linked to ROSC	Yes	Emphasizes importance of first attempt success
Inoue A (2019)[98]	PLOS ONE	Prospective Evaluation	C-LD	Hypertension post-intubation linked to multiple attempts	Yes	≥3 attempts associated with higher post-intubation hypertension

LOE=Level of Evidence; RCT=Randomised Controlled Trial; POST=Postoperative sore throat; OR=Operating Room; RSI=Rapid sequence induction; CICV=Cannot intubate cannot ventilate; CVCI=Cannot ventilate cannot intubate; GA=General anaesthesia; ED=Emergency Department; OHCA=Out-of-Hospital Cardiac Arrest; ROSC=Return of spontaneous circulation; HTN=Hypertension

Appendix 3

Research Question 3: What is the maximum number of attempts at supraglottic airway (SGA) insertion that should be permitted to limit airway management-related complications in adult patients?

• P- Adult patients undergoing intubation

• I - SGA insertion attempts

• C— SGA insertion attempts

• O- Airway trauma and oedema, desaturation

Supplementary Table 3a.

Concept Table for Research Question - What is the maximum number of attempts at supraglottic airway (SGA) insertion that should be permitted to limit airway management-related complications in adult patients?

Research Question	Concept 1	Concept 2	Concept 3	Concept 4	Concept 5
Key concepts	Adults	Intubation	GA	SGA Supraglottic airway	SGA insertion attempts
Free text terms/ natural language terms (synonyms, UK/US terminology, medical/laymen's terms, acronyms/ abbreviations, drug brands, more narrow search terms) Consider: phrase searching, proximity operators, truncation, wildcards, field qualification (e.g. textword)	“adult” “adults” “adult's”	“intubate”[All Fields] OR “intubated”[All Fields] OR “intubates”[All Fields] OR “intubating”[All Fields] OR “intubation”[MeSH Terms] OR “intubation”[All Fields] OR “intubations”[All Fields] OR “intubator”[All Fields] OR “intubator s”[All Fields] OR “intubators”[All Fields]	Anesthesia, General/methods* Anesthesia* Anesthesia, Obstetrical/ methods* Anesthesia, Obstetrical* Anesthesias, General General Anesthesia General Anesthesias	(“supraglottal”[All Fields] OR “supraglottic”[All Fields]) AND (“airway”[All Fields] OR “airway s”[All Fields] OR “airways”[All Fields}	(“supraglottal”[All Fields] OR “supraglottic”[All Fields]) AND (“airway”[All Fields] OR “airway s”[All Fields] OR “airways”[All Fields]) AND (“insert”[All Fields] OR “insert s”[All Fields] OR “inserted”[All Fields] OR “inserter”[All Fields] OR “inserters”[All Fields] OR “inserting”[All Fields] OR “insertion s”[All Fields] OR “insertional”[All Fields] OR “insertions”[All Fields] OR “inserts”[All Fields] OR “insertional”[All Fields]) OR “insertion”[All Fields]) AND (“attempt”[All Fields] OR “attempted”[All Fields] OR “attempter”[All Fields] OR “attempters”[All Fields] OR “attempting”[All Fields] OR “attempts”[All Fields])))
Controlled vocabularyterms/ Subject terms (MeSH terms, Emtree terms) Consider: explode, major headings, subheadings	“adult”[MeSH Terms]	“Intubation, Intratracheal”[Mesh]	“Anesthetics, General”[Mesh] “Anesthesia”[Mesh] “Anesthesia, Obstetrical”[Mesh]

Search String:

PubMed: 134 results

((“adult”[MeSH Terms] OR “adult”[All Fields] OR “adults”[All Fields] OR “adult s”[All Fields]) AND (“intubate”[All Fields] OR “intubated”[All Fields] OR “intubates”[All Fields] OR “intubating”[All Fields] OR “intubation”[MeSH Terms] OR “intubation”[All Fields] OR “intubations”[All Fields] OR “intubator”[All Fields] OR “intubator s”[All Fields] OR “intubators”[All Fields] OR (“general anaesthesia”[All Fields] OR “anesthesia, general”[MeSH Terms] OR (“anesthesia”[All Fields] AND “general”[All Fields]) OR “general anesthesia”[All Fields] OR (“general”[All Fields] AND “anesthesia”[All Fields]))) AND ((“supraglottal”[All Fields] OR “supraglottic”[All Fields]) AND (“airway”[All Fields] OR “airway s”[All Fields] OR “airways”[All Fields])) AND ((“attempt”[All Fields] OR “attempted”[All Fields] OR “attempter”[All Fields] OR “attempters”[All Fields] OR “attempting”[All Fields] OR “attempts”[All Fields]) AND (“supraglottal”[All Fields] OR “supraglottic”[All Fields]) AND (“airway”[All Fields] OR “airway s”[All Fields] OR “airways”[All Fields]) AND (“insert”[All Fields] OR “insert s”[All Fields] OR “inserted”[All Fields] OR “inserter”[All Fields] OR “inserters”[All Fields] OR “inserting”[All Fields] OR “insertion s”[All Fields] OR “insertional”[All Fields] OR “insertions”[All Fields] OR “inserts”[All Fields] OR “insertion”[All Fields]))) AND ((humans[Filter]) AND (2000:2024[pdat]) AND (english[Filter]) AND (alladult[Filter]))

Scopus: 90 results

(TITLE-ABS-KEY (adult OR adults) AND TITLE-ABS-KEY (intubate OR intubated OR intubates OR intubating OR intubation OR intubations OR intubators) AND TITLE-ABS-KEY (“general anesthesia” OR “general anaesthesia”) AND TITLE-ABS-KEY (supraglottic OR supraglottal) AND TITLE-ABS-KEY (airway OR airways) AND TITLE-ABS-KEY (attempt OR attempted OR attempts OR attempting) AND TITLE-ABS-KEY (insert OR inserted OR inserting OR insertion OR insertions)) AND PUBYEAR > 1999 AND (LIMIT-TO (SUBJAREA, “MEDI”)) AND (LIMIT-TO (LANGUAGE, “English”))

Supplementary Figure 3

PRISMA flow chart for Research Question: What is the maximum number of attempts at supraglottic airway (SGA) insertion that should be permitted to limit airway management-related complications in adult patients?

Supplementary Table 3b.

Summary table for included studies for Research Question - What is the maximum number of attempts at supraglottic airway (SGA) insertion that should be permitted to limit airway management-related complications in adult patients?

First Author (Year)	Journal	Type of Article	Level of Evidence (AHA)	Intervention	Support limiting SGA Attempts	Specific attempt limits
Klementova M (2021)[106]	BMJ Open	Prospective Evaluation	B-NR	I-gel Plus	Yes	Not mentioned
Hattori H (2016)[108]	J Clin Anesth	Randomised Controlled Trial	B-R	I-gel	Yes	Not mentioned
Lee S (2024)[109]	BMC Anesthesiol	Randomised Controlled Trial	B-R	I-gel	Yes	Not mentioned
Wharton NM (2008)[116]	Anaesthesia	Prospective Evaluation	C-LD	I-gel	Yes	Not mentioned
Joly N (2014)[110]	Can J Anaesth	Randomised Controlled Trial	B-R	I-gel vs LMA Supreme	Yes	Not mentioned
Yildiz TS (2007)[111]	Eur J Anaesthesiol	Randomised Controlled Trial	B-R	Laryngeal tube vs LMA	Yes	Not mentioned
Nishiyama T (2012)[112]	Am J Emerg Med	Randomised Controlled Trial	B-R	I-gel	Yes	Not mentioned
Ishio J (2016)[115]	J Clin Anesth	Randomised Controlled Trial	B-R	LMA ProSeal	Yes	Not mentioned
Polat R (2015)[113]	Rev Bras Anestesiol	Randomised Controlled Trial	B-R	I-gel vs LMA Classic	Yes	Not mentioned
Farbood A (2023)[114]	Saudi J Anaesth	Randomised Controlled Trial	B-R	Classic LMA	Yes	Not mentioned
Hernandez MC (2018)[105]	Am J Emerg Med	Observational Study	C-LD	Prehospital SGA	Yes	Not mentioned
Ebied RS (2017)[107]	Egypt J Anaesth	Randomised Controlled Trial	B-R	Air-Q	Yes	3

SGA=Supraglottic airway; LMA=Laryngeal mask airway

Appendix 4

Research Question 4: Does the use of a bougie or stylet improve intubation success following a failed first attempt at intubation?

• P- Adult patient undergoing intubation

• I - Airway adjuncts (Bougie/stylet)

• C - Without adjuncts

• O- Successful intubation, duration

Concept table:

Supplementary Table 4a.

Concept Table for Research Question - Does the use of a bougie or stylet improve intubation success following a failed first attempt at intubation?

Research Question	Concept 1	Concept 2	Concept 3	Concept 4
Key concepts Free text terms/natural language terms (synonyms, UK/US terminology, medical/ laymen's terms, acronyms/ abbreviations, drug brands, more narrow search terms) Consider: phrase searching, proximity operators, truncation, wildcards, field qualification (e.g. textword)	Adults “adult” “adults” “adult's”	Intubation “intubate”[All Fields] OR “intubated”[All Fields] OR “intubates”[All Fields] OR “intubating”[All Fields] OR “intubation”[MeSH Terms] OR “intubation”[All Fields] OR “intubations”[All Fields] OR “intubator”[All Fields] OR “intubator s”[All Fields] OR “intubators”[All Fields]	GA Anesthesia, General/ methods* Anesthesia* Anesthesia, Obstetrical/ methods* Anesthesia, Obstetrical* Anesthesias, General General Anesthesia General Anesthesias	Airway adjuncts (bougie, stylet) “airway”[All Fields] OR “airway s”[All Fields] OR “airways”[All Fields]) AND (“adjunct”[All Fields] OR “adjunction”[All Fields] OR “adjunctions”[All Fields] OR “adjunctive”[All Fields] OR “adjunctively”[All Fields] OR “adjunctives”[All Fields] OR “adjuncts”[All Fields])) OR (“bougie”[All Fields] OR “bougies”[All Fields]) OR (“stylet”[All Fields] OR “styleted”[All Fields] OR “stylets”[All Fields] OR “styletted”[All Fields
Controlled vocabularyterms/ Subject terms (MeSH terms, Emtree terms) Consider: explode, major headings, subheadings	“adult”[MeSH Terms]	“Intubation, Intratracheal”[Mesh]	“Anesthetics, General”[Mesh] “Anesthesia”[Mesh] “Anesthesia, Obstetrical”[Mesh]

Search String

PubMed: 117 results

(((“adult”[MeSH Terms] OR “adult”[All Fields] OR “adults”[All Fields] OR “adult s”[All Fields]) AND (“intubate”[All Fields] OR “intubated”[All Fields] OR “intubates”[All Fields] OR “intubating”[All Fields] OR “intubation”[MeSH Terms] OR “intubation” [All Fields] OR “intubations”[All Fields] OR “intub ator” [All Fields] OR “intubator s”[All Fields] OR “intubators”[All Fields]) AND (“general anaesthesia” [All Fields] OR “anesthesia, general”[MeSH Terms] OR (“anesthesia”[All Fields] AND “general”[All Fields]) OR “general anesthesia”[All Fields] OR (“general”[All Fields] AND “anesthesia”[All Fields]))) AND (((“airway”[All Fields] OR “airway s”[All Fields] OR “airways”[All Fields]) AND (“adjunct” [All Fields] OR “adjunction” [All Fields] OR “adjunctions”[All Fields] OR “adjunctive”[All Fields] OR “adjunctively”[All Fields] OR “adjunctives”[All Fields] OR “adjuncts”[All Fields])) OR (“bougie”[All Fields] OR “bougies”[All Fields]) OR (“stylet”[All Fields] OR “styleted”[All Fields] OR “stylets”[All Fields] OR “styletted”[All Fields]))) AND ((humans[Filter]) AND (2000:2024[pdat]) AND (english[Filter]) AND (alladult[Filter]))

Scopus (Stylet): 340 results

((TITLE-ABS-KEY (intubate OR intubated OR intubates OR intubating OR intubation) AND TITLE-ABS-KEY (“general anesthesia”) AND TITLE-ABS-KEY (airway OR airways OR adjunct OR adjuncts OR bougie OR bougies OR stylet OR stylets)) AND PUBYEAR > 1999) AND (stylet) AND (LIMIT-TO (SUBJAREA, “MEDI”)) AND (LIMIT-TO (LANGUAGE, “English”))

Scopus (Bougie): 219 results

((TITLE-ABS-KEY (intubate OR intubated OR intubates OR intubating OR intubation) AND TITLE-ABS-KEY (“general anesthesia”) AND TITLE-ABS-KEY (airway OR airways OR adjunct OR adjuncts OR bougie OR bougies OR stylet OR stylets)) AND PUBYEAR > 1999) AND (bougie) AND (LIMIT-TO (SUBJAREA, “MEDI”)) AND (LIMIT-TO (LANGUAGE, “English”))

Supplementary Figure 4

PRISMA flow chart for Research Question: Does the use of a bougie or stylet improve intubation success following a failed first attempt at intubation?

Supplementary Table 4b.

Summary Table for included studies for Research Question - Does the use of a bougie or stylet improve intubation success following a failed first attempt at intubation?

Author (Year)	Journal	Type of Study	Level of Evidence (LOE)	Intervention	Specific Adjunct	Supports Airway Adjuncts
Cattano D (2012)[120]	Intern Emerg Med	Prospective Randomised Trial	B-R	Videolaryngo scope + Glide Rite stylet vs Endotrol tube	GlideRite Stylet with VL	Yes
Jaber S (2021)[118]	Intensive Care Med	Randomised Clinical Trial	B-R	Direct Laryngoscopy + stylet vs DL alone	GlideRite stylet	Yes
Eum J (2024)[125]	Anaesthesia	Randomised Controlled Trial	B-R	Hyperangulated VL + bougie vs stylet	Stylet with hyperangulated VL	Yes
Marfin JV (2003)[123]	Anaesthesia	Randomised Controlled Trial	B-R	DL + reusable vs single-use bougie	Resuable bougie	Yes
Puthenveettil N (2023)[122]	J Anaesthesiol Clin Pharmacol	Randomised Controlled Trial	B-R	Aerosol box + stylet vs bougie	Stylet over Bougie	Yes
Korkusuz I (2023)[126]	Trends Anaesth Crit Care	Randomised Controlled Trial	B-R	DL/VL with and without stylet	Stylet	Yes
Park S (2019)[127]	J Clin Med	Randomised Controlled Trial	B-R	DL + lighted vs simple stylet	Lighted stylet better than simple stylet	Yes
Al-Qasmi A (2013)[117]	Trials	Randomised Controlled Trial	B-R	C-MAC D Blade + articulating vs rigid stylet	Articulating stylet with hyperangulated VL	Yes
Law JA (2021)[1]	Can J Anaesth	Guideline/Special Article	C-EO	Not Applicable	Supports Stylet and bougie	Yes
Henderson JJ (2004)[121]	Anaesthesia	Guideline/Special Article	C-EO	Not Applicable	Recommends Bougie (Guideline)	Yes
Strøm C (2015)	Acta Anaesthesiol Scand	Prospective Observational Study	C-LD	McGrath VL + Boedeker forceps	Stylet	No
Xu X (2024)	BMC Anesthesiol	Randomised Crossover Manikin Study	C-LD	VL + Bougie/ Stylet under chest compression	Supports bougie	Yes
Ozdemirkan A (2022)	Braz J Anesthesiol	Prospective, Randomised Study	C-LD	Frova catheter with DL vs McGrath VL	Supports Frova with DL	Yes

VL=Videolaryngoscope; DL=Direct laryngoscope; RCT=Randomised Controlled Trial; Stylet=Intubation stylet; Bougie=Intubation bougie

Appendix 5

Research Question 5: Does apnoeic oxygenation during intubation reduce the risk of desaturation?

• P- Adult patient undergoing intubation

• I -Nasal oxygen/oxygen supplementation/HFNO

• C-No nasal oxygen/no oxygen supplementation

• O- Desaturation during airway management (SpO₂ < 90%)

Supplementary Table 5a.

Concept Table for Research Question - Does apnoeic oxygenation during intubation reduce the risk of desaturation?

Research question	Concept 1	Concept 2	Concept 3	Concept 4
Key concepts	Adults	Intubation	GA	Oxygen supplementation OR Nasal oxygen OR (High Flow Nasal Oxygen)
Free text terms/ natural language terms (synonyms, UK/ US terminology, medical/laymen's terms, acronyms/ abbreviations, drug brands, more narrow search terms) Consider: phrase searching, proximity operators, truncation, wildcards, field qualification (e.g. textword)	“adult” “adults” “adult's”	“intubate”[All Fields] OR “intubated”[All Fields] OR “intubates”[All Fields] OR “intubating”[All Fields] OR “intubation”[MeSH Terms] OR “intubation”[All Fields] OR “intubations”[All Fields] OR “intubator”[All Fields] OR “intubator s”[All Fields] OR “intubators”[All Fields]	Anesthesia, General/ methods* Anesthesia* Anesthesia, Obstetrical/ methods* Anesthesia, Obstetrical* Anesthesias, General General Anesthesia General Anesthesias	((“cell respiration”[MeSH Terms] OR (“cell”[All Fields] AND “respiration”[All Fields]) OR “cell respiration”[All Fields] OR “oxygenation”[All Fields] OR “oxygen”[MeSH Terms] OR “oxygen”[All Fields] OR “oxygen s”[All Fields] OR “oxygenate”[All Fields] OR “oxygenated”[All Fields] OR “oxygenates”[All Fields] OR “oxygenating”[All Fields] OR “oxygenations”[All Fields] OR “oxygenative”[All Fields] OR “oxygenator s”[All Fields] OR “oxygenators”[MeSH Terms] OR “oxygenators”[All Fields] OR “oxygenator”[All Fields] OR “oxygene”[All Fields] OR “oxygenic”[All Fields] OR “oxygenous”[All Fields] OR “oxygens”[All Fields]) AND (“supplemental”[All Fields] OR “supplementating”[All Fields] OR “supplementation”[All Fields] OR “supplementation s”[All Fields] OR “supplementations”[All Fields] OR “supplemention”[All Fields])) OR ((“nasalance”[All Fields] OR “nasality”[All Fields] OR “nasalization”[All Fields] OR “nasalized”[All Fields] OR “nasally”[All Fields] OR “nose”[MeSH Terms] OR “nose”[All Fields] OR “nasal”[All Fields] OR “nasals”[All Fields]) AND (“cell respiration”[MeSH Terms] OR (“cell”[All Fields] AND “respiration”[All Fields]) OR “cell respiration”[All Fields] OR “oxygenation”[All Fields] OR “oxygen”[MeSHTerms] OR “oxygen”[All Fields] OR “oxygen s”[All Fields] OR “oxygenate”[All Fields] OR “oxygenated”[All Fields] OR “oxygenates”[All Fields] OR “oxygenating”[All Fields] OR “oxygenations”[All Fields] OR “oxygenative”[All Fields] OR “oxygenator s”[All Fields] OR “oxygenators”[MeSH Terms] OR “oxygenators”[All Fields] OR “oxygenator”[All Fields] OR “oxygene”[All Fields] OR “oxygenic”[All Fields] OR “oxygenous”[All Fields] OR “oxygens”[All Fields])) OR (“High”[All Fields] AND (“flow camb”[Journal] OR “flow”[All Fields]) AND (“nasalance”[All Fields] OR “nasality”[All Fields] OR “nasalization”[All Fields] OR “nasalized”[All Fields] OR “nasally”[All Fields] OR “nose”[MeSH Terms] OR “nose”[All Fields] OR “nasal”[All Fields] OR “nasals”[All Fields]) AND (“cell respiration”[MeSH Terms] OR (“cell”[All Fields] AND “respiration”[All Fields]) OR “cell respiration”[All Fields] OR “oxygenation”[All Fields] OR “oxygen”[MeSH Terms] OR “oxygen”[All Fields] OR “oxygen s”[All Fields] OR “oxygenate”[All Fields] OR “oxygenated”[All Fields] OR “oxygenates”[All Fields] OR “oxygenating”[All Fields] OR “oxygenations”[All Fields] OR “oxygenative”[All Fields] OR “oxygenator s”[All Fields] OR “oxygenators”[MeSHTerms] OR “oxygenators”[All Fields] OR “oxygenator”[All Fields] OR “oxygene”[All Fields] OR “oxygenic”[All Fields] OR “oxygenous”[All Fields] OR “oxygens”[All Fields]))
Controlled vocabularyterms/ Subject terms (MeSH terms, Emtree terms) Consider: explode, major headings, subheadings	“adult”[MeSH Terms]	“Intubation, Intratracheal”[Mesh]	“Anesthetics, General”[Mesh] “Anesthesia”[Mesh] “Anesthesia, Obstetrical”[Mesh]	“oxygen”[MeSH Terms]

Search String:

PubMed: 345 results

((“adult”[MeSH Terms] OR “adult”[All Fields] OR “adults”[All Fields] OR “adult s”[All Fields]) AND (“intubate”[All Fields] OR “intubated”[All Fields] OR “intubates”[All Fields] OR “intubating”[All Fields] OR “intubation”[MeSH Terms] OR “intubation”[All Fields] OR “intubations”[All Fields] OR “intubator”[All Fields] OR “intubator s”[All Fields] OR “intubators”[All Fields]) AND (((“nasalance”[All Fields] OR “nasality”[All Fields] OR “nasalization”[All Fields] OR “nasalized”[All Fields] OR “nasally”[All Fields] OR “nose”[MeSH Terms] OR “nose”[All Fields] OR “nasal”[All Fields] OR “nasals”[All Fields]) AND (“cell respiration”[MeSH Terms] OR (“cell”[All Fields] AND “respiration”[All Fields]) OR “cell respiration”[All Fields] OR “oxygenation”[All Fields] OR “oxygen”[MeSH Terms] OR “oxygen”[All Fields] OR “oxygen s”[All Fields] OR “oxygenate”[All Fields] OR “oxygenated”[All Fields] OR “oxygenates” [All Fields] OR “oxygenating” [All Fields] OR “oxygenations” [All Fields] OR “oxygenative”[All Fields] OR “oxygenator s”[All Fields] OR “oxygenators”[MeSH Terms] OR “oxygenators”[All Fields] OR “oxygenator” [All Fields] OR “oxygene”[All Fields] OR “oxygenic” [All Fields] OR “oxygenous” [All Fields] OR “oxygens”[All Fields]) AND (“supplemental”[All Fields] OR “supplementating”[All Fields] OR “supplementation”[All Fields] OR “supplementation s”[All Fields] OR “supplementations”[All Fields] OR “supplemention”[All Fields])) OR (“High”[All Fields] AND (“flow camb”[Journal] OR “flow”[All Fields]) AND (“nasalance”[All Fields] OR “nasality”[All Fields] OR “nasalization”[All Fields] OR “nasalized”[All Fields] OR “nasally”[All Fields] OR “nose”[MeSH Terms] OR “nose”[All Fields] OR “nasal”[All Fields] OR “nasals”[All Fields]) AND (“cell respiration”[MeSH Terms] OR (“cell”[All Fields] AND “respiration”[All Fields]) OR “cell respiration”[All Fields] OR “oxygenation”[All Fields] OR “oxygen”[MeSH Terms] OR “oxygen”[All Fields] OR “oxygen s”[All Fields] OR “oxygenate”[All Fields] OR “oxygenated”[All Fields] OR “oxygenates”[All Fields] OR “oxygenating”[All Fields] OR “oxygenations”[All Fields] OR “oxygenative”[All Fields] OR “oxygenator s”[All Fields] OR “oxygenators”[MeSH Terms] OR “oxygenators”[All Fields] OR “oxygenator”[All Fields] OR “oxygene”[All Fields] OR “oxygenic”[All Fields] OR “oxygenous” [All Fields] OR “oxygens”[All Fields])))) AND ((humans [Filter]) AND (english[Filter]) AND (2000:2024[pdat]))

Scopus: 279 results

((adult OR adults) AND (intubate OR intubated OR intubates OR intubating OR intubation OR intubations OR intubator OR intubators) AND ((nasal OR nasality OR nasalization OR nasalized OR nasally OR nose) AND (oxygenation OR oxygen OR oxygenate OR oxygenated OR oxygenates OR oxygenating OR oxygenators) AND (supplemental OR supplementation)) AND (“high flow” OR “cell respiration”) AND PUBYEAR > 1999 AND PUBYEAR < 2025 AND PUBYEAR > 2007 AND PUBYEAR < 2025) AND (anesthesia) AND (anaesthesia) AND (LIMIT-TO (DOCTYPE, “ar”) OR LIMIT-TO (DOCTYPE, “re”)) AND (LIMIT-TO (LANGUAGE, “English”)) AND (LIMIT-TO (EXACTKEYWORD, “Human”) OR LIMIT-TO (EXACTKEYWORD, “Humans”))

Supplementary Figure 5

PRISMA flow chart for Research Question: Does apnoeic oxygenation during intubation reduce the risk of desaturation?

Supplementary Table 5b.

Summary Table for included studies for Research Question - Does apnoeic oxygenation during intubation reduce the risk of desaturation?

Author (Year)	Journal	Type of Study	Level of Evidence (AHA)	Intervention	Outcome	Supports Apneic Oxygen?
Bright D (2023)[136]	AnesthAnalg	Meta-analysis	A	HFNC 50-70 l/ min) preoxygenation until intubation vs FM preoxygenation (8-15 L +/- CPAP) in obese	Primary- Desaturation less than 92% till intubation Secondary- Safe apnea time	No difference in desaturation but longer safe apnea time
Abdelmoneim W (2023)[129]	J Cell Mol Anesth	Randomised Controlled Trial (Prospective)	B-R	Nasal O2 10 L/min vs No Nasal oxygen during intubation in obese parturient	lowest oxygen saturation recorded.	Yes (improves SpO2 in apnoeic oxygenation)
Preya R (2023)[130]	J Anaesthesiol Clin Pharmacol	Randomised Controlled Trial (Prospective)	B-R	Preoxygeantion (5 L same in both + No Nasal oxygen vs Nasal catheter 10 L/min in RSI in laparotomy	PaO2 fall after 90 second apnea.	Yes (less PaO2 fall) 2
Pierpoint J (2023)[131]	J Clin Anesth	Randomised Controlled Trial	B-R	Standard preoxygenation in both group + Nasopharyngeal catheter apneic oxygenation 18 L/min vs no apneic oxygenation in obese patients	Safe apnea time (to desaturation of 92% or 600 sec)	Yes (significantly prolong desaturation time in apnoeic oxygen group)
Geng W (2022)[132]	Sci Rep	Randomised Controlled Trial	B-R	Modified nasopharyngeal airway 12 L/min vs HFNO 60 L/min in female patient for laparoscopy	Safe apnea time - SpO2 to 95% or 20 minutes	Yes (equally effective)
Schutzer-Weissmann J (2023)[133]	Br J Anaesth	Randomised Controlled Trial	B-R	Preoxygenation + apneic oxygen with HFNO 35-70 L/min vs Face mask preoxygenation plus apneic oxygenation 15 L/min in obese patients	Desaturation in apnea duration	Yes (HFNO comparable with face mask)
Heard A (2017)[134]	AnesthAnalg	Randomised Controlled Trial	B-R	Buccal oxygen via RAE tube 10 L/min vs no apneic oxygen in obese patients	time to reach SpO2 <95% or 750 sec	Yes (buccal oxygen is helpful)
Wong DT (2019)[135]	AnesthAnalg	Randomised Controlled Trial	B-R	HFNO Preoxygenation 40 L/min +Apneic oxygenation with 60 L/min vs facemask (EtO2>85%) preoxygenation and no apnoeic oxygenation in morbid obese patients	Time to reach SpO2 <95% or 6 minutes	Yes
Lyons J (2024)[137]	Anaesthesia	Randomised Controlled Trial	B-R	HFNO at 0, 70, 120 L/min during apnea, for rise in CO2 during apnea	Rate of CO2 rise is same	No
Hanouz JL (2019)[138]	Eur J Anaesthesiol	Crossover Randomised Controlled Trial	B-R	HFNO 60L/min vs face mask preoxygenation (12 L) healthy volunteer,	Achieving EtO2 with preoxygenation	No
Moon Y (2019)[139]	Obes Surg	Double-blind Randomised Controlled Trial	B-R	No apnoeic oxygen vs Nasal cannula 15 L O2 vs Nasal cannula 15 l air in Obese Patients	Safe apnea duration	Yes
Ng I (2018)[140]	Anaesth Intensive Care	Randomised Controlled Trial	B-R	HFNO 30-70 L/min as preoxygenation plus apneic oxygenation vs facemask preoxygenation (10 L/min) plus BMV before laryngoscopy	PaO2 after 5 minutes	Yes
Grude M (2018)[128]	J Clin Anesth	Narrative Review (of RCTs)	C-LD	Nasal/ nasopharyngeal apneic oxygenation (3-10 L/min)- 8 RCT in adult patients	Time until desaturation or degree of hypoxemia	Yes

RCT=Randomised Controlled Trial; HFNO=High-Flow Nasal Oxygen; FM=Facemask; AO=Apnoeic oxygenation; THRIVE=Transnasal Humidified Rapid Insufflation Ventilatory Exchange; BMV=Bag-valve mask; ED=Emergency Department; NIV=Noninvasive ventilation; PaO2=Partial pressure of oxygen; EtO2 =End tidal Oxygen; CO₂=Carbon dioxide; SpO₂=Oxygen saturation

Appendix 6

Research Question 6: Is surgical cricothyroidotomy preferred over other techniques of emergency cricothyroidotomy?

• P- Adult patient undergoing intubation

• I - Surgical cricothyroidotomy

• C- Narrow bore cricothyroidotomy/wide bore/tracheostomy

• O- Securing the airway, desaturation, ventilation success

Supplementary Table 6a.

Concept Table for Research Question - Is surgical cricothyroidotomy preferred over other techniques of emergency cricothyroidotomy?

Research Question	Concept 1	Concept 2	Concept 3	Concept 4
Key concepts	Adults	Intubation	GA	Surgical cricothyrotomy/ cricothyroidotomy
Free text terms/natural language terms (synonyms, UK/US terminology, medical/ laymen's terms, acronyms/abbreviations, drug brands, more narrow search terms) Consider: phrase searching, proximity operators, truncation, wildcards, field qualification (e.g. textword)	“adult” “adults” “adult's”	“intubate”[All Fields] OR “intubated”[All Fields] OR “intubates”[All Fields] OR “intubating”[All Fields] OR “intubation”[MeSH Terms] OR “intubation”[All Fields] OR “intubations”[All Fields] OR “intubator”[All Fields] OR “intubator s”[All Fields] OR “intubators”[All Fields]	Anesthesia, General/methods* Anesthesia* Anesthesia, Obstetrical/ methods* Anesthesia, Obstetrical* Anesthesias, General General Anesthesia General Anesthesias	“surgical procedures, operative”[MeSH Terms] OR (“surgical”[All Fields] AND “procedures”[All Fields] AND “operative”[All Fields]) OR “operative surgical procedures”[All Fields] OR “surgical”[All Fields] OR “surgically”[All Fields] OR “surgicals”[All Fields]) AND (“cricothyrotomies”[All Fields] OR “cricothyrotomy”[All Fields])) OR ((“surgical procedures, operative”[MeSH Terms] OR (“surgical”[All Fields] AND “procedures”[All Fields] AND “operative”[All Fields]) OR “operative surgical procedures”[All Fields] OR “surgical”[All Fields] OR “surgically”[All Fields] OR “surgicals”[All Fields]) AND (“cricothyroidotomies”[All Fields] OR “cricothyroidotomy”[All Fields]
Controlled vocabularyterms/Subject terms (MeSH terms, Emtree terms) Consider: explode, major headings, subheadings	“adult”[MeSH Terms]	“Intubation, Intratracheal”[Mesh]	“Anesthetics, General”[Mesh] “Anesthesia”[Mesh] “Anesthesia, Obstetrical”[Mesh]	“surgical procedures, operative”[MeSH Terms] “surgical procedures, operative”[MeSH Terms]

Search string

PubMed: 124 results

(((“adult”[MeSH Terms] OR “adult”[All Fields] OR “adults”[All Fields] OR “adult s”[All Fields]) AND (“intubate”[All Fields] OR “intubated”[All Fields] OR “intubates”[All Fields] OR “intubating”[All Fields] OR “intubation”[MeSH Terms] OR “intubation”[All Fields] OR “intubations”[All Fields] OR “intubator”[All Fields] OR “intubator s”[All Fields] OR “intubators”[All Fields] OR (“general anaesthesia”[All Fields] OR “anesthesia, general”[MeSH Terms] OR (“anesthesia”[All Fields] AND “general”[All Fields]) OR “general anesthesia” [All Fields] OR (“general”[All Fields] AND “anesthesia”[All Fields])))) AND ((((“surgical procedures, operative”[MeSH Terms] OR (“surgical”[All Fields] AND “procedures” [All Fields] AND “operative” [All Fields]) OR “operative surgical procedures”[All Fields] OR “surgical”[All Fields] OR “surgically”[All Fields] OR “surgicals”[All Fields]) AND (“cricothyrotomies”[All Fields] OR “cricothyrotomy”[All Fields])) OR ((“surgical procedures, operative”[MeSH Terms] OR (“surgical”[All Fields] AND “procedures”[All Fields] AND “operative”[All Fields]) OR “operative surgical procedures”[All Fields] OR “surgical”[All Fields] OR “surgically”[All Fields] OR “surgicals”[All Fields]) AND (“cricothyroidotomies”[All Fields] OR “cricothyroidotomy”[All Fields]))) AND (“humans”[MeSH Terms] AND “english”[Language] AND “adult”[MeSH Terms]))) AND ((humans[Filter]) AND (english[Filter]) AND (alladult[Filter]) AND (2000:2024[pdat]))

Scopus: 118 result

(TITLE-ABS-KEY (adult OR adults) AND TITLE-ABS-KEY (intubate OR intubated OR intubates OR intubating OR intubation OR intubations OR intubators) AND TITLE-ABS-KEY (“surgical procedures” OR surgical OR surgically OR “operative procedures”) AND TITLE-ABS-KEY (cricothyrotomy OR cricothyrotomies OR cricothyroidotomy OR cricothyroidotomies)) AND PUBYEAR > 1999 AND (LIMIT-TO (SUBJAREA, “MEDI”)) AND (LIMIT-TO (LANGUAGE, “English”))

Supplementary Figure 6

PRISMA flow chart for Research Question: Is surgical cricothyroidotomy preferred over other techniques of emergency cricothyroidotomy?

Supplementary Table 6b.

Summary Table for included studies for Research Question - Is surgical cricothyroidotomy preferred over other techniques of emergency cricothyroidotomy?

Author (Year)	Journal	Type of Article	Level of Evidence (AHA)	Intervention	Type of Surgical Airway Suggested	Supports Surgical Airway as Preferred Method?
Asselin M (2021)[144]	MedEdPORTAL	Original Publication	C-LD	Bougie-assisted surgical cricothyrotomy on fresh human cadavers	Surgical cricothyroidotomy	Yes
Schaumann N (2005)[142]	Anesthesiology	Randomised Controlled Trial	C-LD	Conventional surgical and Seldinger techniques	Surgical cricothyroidotomy	No
Wong DT (2014)[143]	Can J Anaesth	Survey	C-LD	Wire-guided cricothyroidotomy	Wire-guided cricothyroidotomy	Partial
Silverio SA (2021)[145]	PLoS One	Simulation-based training	C-LD	Simulation-based training on FONA in CICO scenarios	Surgical cricothyroidotomy	Yes
Adigbli G (2015)[146]	BMJ Case Rep	Case Report	C-LD	Needle cricothyroidotomy and jet ventilation or surgical cricothyroidotomy	Surgical cricothyroidotomy	Yes
Nachshon A (2024)[147]	Anaesthesiol Intensive Ther	Retrospective Study	C-LD	Percutaneous dilatational tracheostomy vs Cricothyrotomy (CTM)	Cricothyrotomy	No
Wong DT (2005)[80]	AnesthAnalg	Survey	C-LD	Cricothyroidotomy by IV catheter	IV Catheter cricothyroidotomy	Partial
Duggan LV (2018)[79]	Anaesthesia	Retrospective Observational Study	C-LD	Emergency front-of- neck airway procedures including scalpel-bougie and surgical	Scalpel-bougie/ Surgical cricothyroidotomy	Yes
Wong DT (2003)[148]	Anesthesiology	Mannequin study	C-LD	Percutaneous dilational cricothyroidotomy	Percutaneous cricothyroidotomy	Yes
Schober P (2009)[78]	Resuscitation	Randomised Controlled Trial (Human cadavers)	C-LD	Anatomical -Surgical vs puncture technique	Anatomical -Surgical cricothyroidotomy	Yes
Kanji H (2012)[81]	Acad Emerg Med	Randomised Controlled Trial	C-LD	Incision-first vs needle- first percutaneous technique	Surgical cricothyroidotomy (IF)	Yes
Berkow LC (2009)[149]	AnesthAnalg	Retrospective Review	C-LD	Comprehensive difficult airway program vs surgical airway	Surgical cricothyroidotomy	Yes
Helm M (2013)[150]	Emerg Med J	Randomised Controlled Trial (Human cadavers)	C-LD	Indicator-guided puncture vs standard surgical technique	Surgical cricothyroidotomy	Yes
Drew T, (2018)[77]	Br J Anaesth	Comparative Study	C-LD	Laryngeal handshake technique vs usual CTM identification	Not applicable (CTM identification study)	No
Tscharlou ASP (2006)[151]	Clin Anat	Original Article (Cadaver)	C-LD	Device for cricothyroidotomy	Surgical cricothyroidotomy	Unclear
Wexler S (2018)[152]	Anaesth Intensive Care	Case Report	C-LD	Cannula cricothyroidotomy	Cannula cricothyroidotomy	Unclear
Hill JS (2023)[153]	Int J ObstetAnesth	Case Report	C-LD	Scalpel-bougie technique	Scalpel-bougie cricothyroidotomy	Yes
Tanaka S (2023)[154]	Am J Case Rep	Case Report	C-LD	Scalpel	Scalpel cricothyroidotomy	Yes
Nabecker S (2021)[155]	Eur J Anaesthesiol	Randomised Trial	C-LD	Pocketknife vs cricothyroidotomy sets	Knife cricothyroidotomy	Yes
Bielka K (2024)[156]	BMC Anesthesiol	Prospective Controlled Study	C-LD	Simulation on CI and CICO scenarios	Surgical cricothyroidotomy	Yes
Cook TM (2011)[4]	Br J Anaesth	Audit (NAP4)	C-LD	Tracheostomy or cricothyroidotomy	Surgical cricothyroidotomy	Yes
Govardhane BT (2023)[157]	Indian J Anaesth	Cross-sectional Survey	C-LD	Practice patterns among anaesthesiologists	Varied surgical techniques	Partial
Eisenburger P (2000)[141]	Anesthesiology	Randomised Controlled Trial (Cadavers)	C-LD	Surgical vs Seldinger techniques	Surgical cricothyroidotomy	No

LOE=Level of Evidence; RCT=Randomised Controlled Trial; CTM=Cricothyroid membrane; FONA=Front-of-Neck Access; CI=Cannot intubate; CICO=Cannot intubate cannot oxygenate; IF=Incision first; IV=Intravenous; NAP4=4th National Audit Project

Appendix 7

Supplementary Table 7.

Consensus and Stability Analysis of the Clinical Statements from Delphi Survey

Likert Scale Statements and Multiple-Choice Questions	Agree (%)	Neutral (%)	Disagree (%)	Median (IQR)	P
1. Administration of neuromuscular blockade can improve mask ventilation when difficulty with mask ventilation is encountered in adult patients	96	4	0	7(0)	0.06
2. Following a failed intubation, laryngoscopy should be re-attempted only if the oxygen saturation (SpO2) is above the following value • >90% • >95% • >98%	4 96 0				0.25
3. What is the maximum number of attempts at intubations that should be permitted to prevent airway management-related complications in adult patients? • Maximum 1 • Maximum 2 • Maximum 3 • Maximum 4	0 13 87 0				0.37
4. What is the maximum number of attempts at supraglottic airway (SGA) insertion that should be permitted to prevent airway management-related complications in adult • Maximum 2 • Maximum 3	65 35				0.76
5. When there is complete ventilation failure (a situation where intubation, ventilation using SGA and face mask have all failed after giving the best attempt, even if oxygenation may be maintained) which of the following rescue techniques should we recommend in adult patients? • Prefer surgical cricothyroidotomy (Needle or cannula cricothyroidotomy may also be used) • Only surgical cricothyroidotomy (scalpel bougie technique) • Only wide bore cannula cricothyroidotomy with commercial kits • Only needle cricothyroidotomy with jet ventilation	91 9 0 0				1.0

IQR=Interquartile Range

Funding Statement

All expenses related to the development of the guidelines were entirely funded by the All-India Difficult Airway Association (AIDAA).