Management of airway obstruction

Key points.

• •Patients with airway obstruction are high risk; they should be managed by senior anaesthetic and surgical staffs that have good technical and non-technical skills.
• •There is no universal ‘best approach’ with experts often providing differing opinions on optimal management.
• •The best outcomes are achieved by the right personnel using equipment with which they are familiar and skilled, at the right time, and in the right location.
• •Holding measures are often useful, allowing time to assemble team members, gain further information, and plan airway intervention.
• •Oxygen delivery utilising high-flow nasal cannula is revolutionising airway management and should be available.

Anaesthetists are experts in airway management, but serious complications of airway management still occur. In 1998, the National Confidential Enquiry into Perioperative Deaths reported concern about management of the obstructed airway.¹ The Fourth National Audit Project (NAP4) illustrated that 40% of cases that resulted in a significant adverse outcome had involved a disease process in the head, neck, or trachea.² Approximately 70% of adverse outcomes involved an obstructed airway, with management being considered poor in one-third.

Anaesthetists and patients have benefitted from excellent evidence-based guidelines from the UK Difficult Airway Society (DAS) pertaining to failed intubation and extubation; however, at present, there remains no guidance on best management strategies for airway obstruction. This goes some way to demonstrate the complexity of airway management in the context of obstruction: patients present with a variety of symptoms, severity, and urgency with a wide spectrum of pathology, to anaesthetists who have a range of experience and competency in airway techniques and critical decision making. The reality is that, in addition to the lack of guidelines for management, there is often not even a consensus for optimal management amongst experts.³

The Royal College of Anaesthetists' Guidelines for the Provision of Anaesthetic Services for head and neck surgery states that these patients should have care provided by anaesthetists skilled in the management of complex airway problems.⁴ However, not all anaesthetists get sufficient exposure to these challenging cases, which can often present out of routine working hours. It is important that anaesthetists are skilled in a variety of techniques, adapting them to each specific case, and have good non-technical skills to work in complex scenarios.

Mechanics of obstruction

Airway patency is dynamic and is affected by the interplay of pressures within the airway.⁵ A degree of obstruction can occur both during anaesthesia and normal sleep with loss of tone within the supporting pharyngeal muscles. The presence of an airway lesion, with further loss of space within the airway, will compound the effects by increasing resistance and reducing rate of passing airflow. This is particularly the case during spontaneous ventilation when negative intra-thoracic pressures are created downstream of the lesion, increasing the tendency for airway collapse. All anaesthetic agents, to some degree, increase the propensity of the airway to collapse.

Presentation of airway obstruction

Airway obstruction covers a spectrum of presentations and comprises upper-airway obstruction, with pathology extending from the nose or mouth to the larynx, and lower-airway obstruction relating to the tracheobronchial tree. The obstruction can be intrinsic, lying within the airway lumen, or be extrinsic/compressive.

Patient history and assessment are crucial. Presence of noisy breathing; voice change; dyspnoea; and dyspnoea on exertion, dysphagia, or nocturnal/postural symptoms should be sought in addition to a standard anaesthetic history. Assessment of the patient's work of breathing and accompanying hypoxaemia should alert the team to a more time-critical situation.

Patients presenting acutely often have significant signs and symptoms, with a marked increase in their work of breathing, respiratory fatigue, hypoxia, and may be extremely agitated. Signs of accessory muscle use, tracheal tug, and chest-wall recession may be visible and added noise may be present, classically depicting the level of obstruction (Table 1). A patient with a more slowly developing obstruction may have few symptoms. Slow progression allows the respiratory muscles to become conditioned, helping generate the required negative pressure to overcome the obstruction. Patients with a chronic progressive disease can deteriorate rapidly, as they can be precariously close to a ‘tipping point’ with a lack of respiratory reserve working against an already compromised airway.

Table 1.

Aetiology of airway obstruction and typical signs and symptoms.

Site	Symptoms/signs	Example of pathology
Oropharyngeal	Snoring, gurgling sounds audible, visible swelling	Tumour, angioedema, abscess
Base of tongue/epiglottis	Dysphagia, drooling, stridor	Epiglottitis, tumour, angioedema
Glottis	Stridor, paroxysmal nocturnal dyspnoea, voice changes	Tumour, Reinke's oedema, subglottic stenosis
Tracheal	Expiratory stridor	Retrosternal goitre

Patients with a chronic disease or sub-acute disease will present for elective or expedited surgery. In this setting, anaesthetists are afforded the luxury of time for investigations and reviewing these in conjunction with surgical colleagues.

Emergent airway obstruction is time critical and may involve anaesthetic team members providing on-call duties with less experience in head and neck anaesthesia. There is much less time for investigation and planning. The unpredictability of presentation renders attempts to conduct meaningful studies in airway obstruction very difficult, and thus, this area is ‘bereft of any high quality evidence to support particular approaches’.³

Decision making in airway obstruction

The first most appropriate step is to define the urgency of the situation. This requires patient assessment and is best done in conjunction with a senior ear, nose, and throat (ENT) surgeon. Progression of symptoms should raise alarm: evolution from a simple change in voice, to a weakening cough, and to difficulty swallowing, drooling, and stridor, should make the team aware of the presence of an increasingly compromised airway and one that will be increasingly difficult to manage. Respiratory distress and increased oxygen requirements are late signs. Consideration must be given to the anticipated clinical course, potential for deterioration, timing of intervention, and efficacy of holding measures.

The key questions are: (i) How time critical is airway management? and (ii) Will holding measures be useful?

Next, one should attempt to define the lesion. Knowledge of the location of the lesion provides crucial information, as some pathologies and their size, positioning, or movement with respiration will render some techniques unsuitable. Investigations, if time allows, may be appropriate and these should be carried out with the aim of answering the following questions: (i) Where is the lesion?, (ii) Is it mobile?, and (iii) How does it influence airway intervention?

One must then consider how best to provide airway security for this patient safely. Ideally, these cases should be managed in the operating theatre. This was supported by a NAP4 recommendation. Although this is true for almost all cases, it should be accepted that, in an acutely compromised patient, undertaking an intra-hospital transfer of a patient who has presented to the emergency department must be carefully considered. It may be more prudent to mobilize the expert team and equipment to the patient. Just like in theatre, confirmation of the availability of the equipment required as the team is verbalising the airway plan is crucial. Further consideration should be given to the following: (i) Am I in the most appropriate location, with the most appropriate personnel and equipment present? and (ii) Given my own skill set, which technique is most appropriate?

These questions highlight the issue of ‘context-sensitive airway management’.⁶ This and the ethos of having the right person in the right place at the right time using the right equipment (in which they are familiar and skilled) are crucial to success.

Holding measures

High-flow nasal oxygen

Oxygen delivery via high-flow nasal cannulae (HFNC) is revolutionising airway management. This therapy has been present in adult and paediatric critical care for some time, and is rapidly becoming a cornerstone in the management of the difficult airway. HFNC systems, such as the Optiflow (Fisher & Paykel Healthcare, Auckland, New Zealand), have been introduced in many areas within anaesthesia, and are being utilized for tubeless field anaesthesia and awake intubation, and in prolonging apnoea time during high-risk general-anaesthesia (GA) inductions. Its use in airway obstruction is hugely beneficial. Oxygen via HFNC can improve airway patency through low-level positive pressure, vastly improves oxygenation, and reduces the work of breathing, and thus, patient distress. Its incorporation as a holding measure, its use as an adjunct during any ensuing awake technique, and its use in prolonging apnoea time if GA is induced are all invaluable, provided that airway patency is maintained. Additionally, continuous oxygen delivery during airway intervention reduces time pressure, which should have a beneficial impact on the anaesthetist's overall performance in a difficult scenario.

Steroid therapy

If there is inflammation or oedema associated with the obstruction, steroids may be helpful, particularly in more elective procedures where there is sufficient time for the drug to act. In the acute setting, they are unlikely to cause harm and may be beneficial. There is little specific evidence to support steroid use as a therapeutic option in an adult with airway obstruction; however, it may be of benefit in some cases, and there is indirect evidence that steroids reduce symptoms of croup in children, and reduce laryngeal oedema and post-extubation stridor.⁷ As a result, their use remains widespread with a perceived benefit as a temporising measure weighed against minimal risk with short-term use. The dose and route for steroid administration are heterogeneous throughout the literature.

Nebulized epinephrine

Epinephrine is a vasoconstrictor and is frequently utilized, although robust evidence to support its use in the acute setting is lacking. It appears to be effective in reducing stridor in a variety of case reports with varying obstructive aetiology. There is evidence for nebulized epinephrine reducing symptom severity in children with croup. A number of resources for adults recommend doses of between 1 and 5 mg of 1:1000 epinephrine nebulized in oxygen.

Heliox

Helium is a less dense gas than oxygen, and this improves airflow, reducing the increased work of breathing secondary to the obstruction by encouraging laminar flow within the narrowed upper airway. Helium–oxygen mixtures have been used in airway obstruction; however, the scope is limited by the reduced oxygen content of any mixture required to maximize favourable flow characteristics. Other than case reports, data supporting heliox use are limited.

Continuous positive airway pressure

Continuous positive airway pressure (CPAP) is successfully used in obstructive sleep apnoea, and works by splinting the collapsible segment. It is a useful adjunct during airway obstruction and in the treatment of any associated post-obstructive pulmonary oedema. As a preoperative measure or for use in the postoperative recovery room, HFNC is better tolerated and may itself provide a small degree of CPAP.

Investigations for the obstructed airway

Nasendoscopy

A nasendoscopy is quick to perform and provides a great deal of information about the appearance of the airway, yet remains underutilized. If the clinical situation does not allow other imaging, a nasendoscopy can still be performed in theatre immediately before anaesthesia. It is extremely helpful for the anaesthetist to carry out or at least be present during the nasendoscopy rather than relying on surgical ‘artwork’ or printed photographs in the notes. Visualising dynamic changes with patient's respiration is important (Fig. 1 online video), as this will impact strategy. In addition, it must be remembered that a view of the larynx from above does not guarantee a view on direct or indirect laryngoscopy, nor does it provide any information on how the airway is likely to behave under anaesthesia.

Supplementary data related to this article can be found online at https://doi.org/10.1016/j.bjae.2017.11.006.

The following are the Supplementary data related to this article:

Video 1

Fig 1 Nasendoscopy showing a mobile lesion adherent to the left vocal cord. This lesion falls through the glottis on inspiration causing significant airway obstruction. Avoidance of positive-pressure ventilation in a ‘ball-valve’ lesion is important. If reading the pdf online, click on the image to view the video.

Computed tomography

Computed tomography (CT) scans provide a rapid and accurate assessment of the structures of the airway. It is readily available, quick and usually well tolerated, and can be performed with the patient in a lateral position if required. CT images can be manipulated into multiplanar reconstructions, allowing further interpretation in various anatomical planes or be used to create a 3D virtual endoscopy using specialist software that offers a digital ‘fly-through’ reconstruction. This process takes several minutes, but images adhere closely to real-time endoscopy.⁸ It must be remembered that these CT images and any manipulation reflect the airway in the supine position, and posture may have an important influence on the appearance. The lack of information regarding any dynamic component of the lesion must be recognized, and thus, this mode of investigation is best viewed as an additional test rather than a replacement for real-time endoscopy, which is likely to be more readily available and appropriate in the emergency situation.

Magnetic resonance imaging

Magnetic resonance imaging is extremely good for delineating soft tissue structures and the physical structure of the airway. However, they take time to perform and patients must lie flat in the scanner with an imaging coil over their head. They are less frequently used than CT.

Approaches to the obstructed airway

Any airway strategy that is implemented should take account of the patient's pathology, the technique that best addresses it, the equipment and team members available, and the teams' familiarity in using that equipment. A primary plan of securing the patient's airway safely must be carefully considered and well communicated. It is crucial to optimize oxygen administration during attempts to secure the airway. Backup plans are required and must include consideration of the reasons for primary plan failure. These may involve an alternative awake technique, induction of GA with potential wake up, or invasive rescue techniques if waking the patient is inappropriate.

Controversy will exist as to what a plan should entail. Experts often fail to agree, and the best strategy for an individual anaesthetist in a given situation may be an anathema for another. Clearly, the absolute priority is oxygenation, by whichever means it is achieved.

Awake fibreoptic intubation

Awake fibreoptic intubation (AFOI) is a very useful technique in airway obstruction if the operator is skilled and feels the fibrescope can be navigated around any lesion and the tracheal tube passed without causing significant trauma. It is a technique that can be used in situations where face-mask ventilation is predicted to be challenging, such as in supraglottic obstructing lesions or masses at the base of the tongue and epiglottis. The application of HFNC during AFOI is a useful adjunct for many reasons.⁹ Several factors can lead to failure of AFOI: a lack of operator skill; secretions or blood in the airway impairing visualisation; or the hypoxic, agitated patient failing to tolerate and comply with the procedure. AFOI can be used with glottic pathology, but an endoscopic assessment must be made on whether the fibrescope and tube can be passed safely. If the laryngeal aperture is small, it is possible to occlude the airway with the scope, causing the ‘cork in the bottle’ phenomenon and total airway obstruction with rapid patient intolerance. Some more cooperative patients, if warned, can be managed through this stage. If the glottis is too stenotic, AFOI is inappropriate. Masses may be difficult to topicalize with local anaesthesia and endoscope/tube-related trauma may provoke brisk bleeding.

Choosing to perform a fibre-optic intubation under GA is a high-risk strategy. If performed in patients with airway pathology, the addition of anaesthesia-induced airway collapse will make concurrent oxygen delivery and navigating the airway even more challenging. In the 14 failures of fibre-optic intubation reported to NAP4, 10 occurred with the patient anaesthetized. Guided intubation via a supraglottic device is more likely to succeed and ensures maintenance of oxygenation throughout. It is the authors' opinion that planned GA non-guided fibre-optic intubation is inadvisable for situations that are anticipated to be difficult.

Awake videolaryngoscopy

The technique of awake videolaryngoscopy (AVL) is gaining prominence.¹⁰ As with any awake technique, the benefit of allowing oxygenation with the patient's own respiratory effort and airway maintenance is beneficial. It can confer a number of advantages over AFOI. Videolaryngoscopy (VL) is becoming a more familiar technique to most anaesthetists, and one that is easier to learn and to remain competent. The use of a hyper-angulated blade will minimize patient discomfort during laryngoscopy as a result of a reduced lifting force during indirect glottic visualisation. VL use provides a wide-angled view and allows airway visualisation in a familiar orientation, which is helpful during instrumentation of a pathological airway. Further benefit is conferred by creating more space within the lumen, perhaps providing some relief from obstruction, allowing passage of the tracheal tube under direct vision, and reducing the risk of trauma and tube impingement. Hence, it is useful for patients with laryngeal pathology and largely overcomes the ‘cork in the bottle’ phenomenon, except for the brief period before the removal of the stylet from the tracheal tube. AVL is less suitable for the base of the tongue or epiglottic lesions, as the laryngoscope is placed in or near the vallecula. AFOI or awake intubation using optical stylets (e.g. Bonfils; KARL STORZ Endoskope, Tuttlingen, Germany) may be more suitable for approaching these lesions.

AVL is a technique that is likely to grow further in popularity. Anaesthetists with infrequent exposure to AFOI, who can learn effective topicalisation and sedation techniques, will have the skills to offer a safe awake option that they may not have undertaken using an AFOI because of lack of skill or confidence.

Awake tracheostomy

Often forwarded as gold-standard management in acute upper-airway obstruction, awake tracheostomy must certainly be considered for patients in whom mask ventilation or intubation is likely to be difficult or impossible, such as those with significant supraglottic or glottic obstruction. Awake tracheostomy cannot be considered a panacea and is by no means an easy option for our surgical colleagues, particularly given the situational factors during such emergent cases. Tracheostomy is increasingly carried out by intensivists using percutaneous techniques, and so, in general terms, is a less commonly performed technique by ENT surgeons. A patient whose airway is critically obstructed may find it impossible to lie flat or still in order to tolerate the procedure, and the use of sedation in such a patient comes with the risk of further airway compromise, but may be required. Concurrent delivery of oxygen with HFNC is once again beneficial, reducing work of breathing and patient distress, and perhaps increasing safety margins in the administration any sedative that has been is carefully titrated.

In many situations of critical airway stenosis, awake techniques are often offered as preferred management; however, the reality of performing these in agitated, distressed, and hypoxic patients may not be straightforward and may prove impossible in terms of patient compliance with the technique or positioning for tracheostomy. Introducing GA may be more appropriate as long as rescue techniques are agreed.

GA with i.v. induction

Historically, GA in combination with the administration of neuromuscular blocking agents (NMBA) has been avoided in airway obstruction. This viewpoint has changed over the years, but it still remains controversial.

Paralysis facilitates routine face-mask ventilation under GA. In cases of difficulty, NMBAs may help, but administration is unlikely to make airway conditions any worse. There is evidence that NMBAs improve ventilation in stridulous patients with glottic pathology.¹¹ It may be that GA is the only technique that a distressed patient with severe acute obstruction will tolerate. Laryngoscopy, both direct and indirect, and tracheal intubation may be difficult, but concurrent oxygen delivery by HFNC can lengthen the time to onset of desaturation, enhancing patient safety and potentially improving anaesthetist performance. The combination of HFNC with GA in conjunction with VL may increase in use.

Some experts advocate the pre-emptive placement of a needle cricothyroidotomy before GA in order to provide an in situ rescue method for oxygen insufflation should the primary airway plan fail. Alternative backup plans can include supraglottic airway devices, surgical front-of-neck access, or rigid bronchoscopy, and these should all be discussed amongst the team before beginning. As with all airway instrumentation, attempts should be limited to avoid iatrogenic trauma, and failure should trigger the transition to the next stage of management. Any plan that involves waking the patient as an option must consider whether or not this is a viable option.

Sugammadex, at a dose of 16 mg kg⁻¹, provides rapid reversal of deep neuromuscular block produced by rocuronium, and was initially lauded as the solution to a 'cannot intubate, cannot ventilate' situation; however, it only reverses the NMBA component and does not influence the effect of hypnotic drugs. The immediate reversal of neuromuscular block with sugammadex has been demonstrated to be associated with laryngospasm and worsening of airway patency.12, 13

GA with inhalation induction

Inhalation induction has historically been the technique of choice for the management of an obstructed airway and was advocated in previous versions of this publication.¹⁴ The perceived advantage of an inhalation induction is that, by maintaining spontaneous ventilation and hence reversibility, there may be the option of waking the patient if required. However, the partially obstructed airway is at risk of deteriorating during this process, further impairing gas exchange and limiting safe reversal. Continued negative-pressure generation during inspiration favours pharyngeal collapse, leading to worsening airway obstruction and is often encountered before sufficient anaesthetic depth, necessary to allow airway instrumentation, is achieved. If obstruction cannot be resolved, the volatile inhalation anaesthetic agent cannot be expelled and the patient cannot be woken. The process of inhalation induction is a slow one, and sufficient depth may not even be achieved using sevoflurane at 8%. Application of CPAP should help splint the airway, but may not provide patency if significant negative pressures are being generated during inspiration.

Of interest, Booth and colleagues¹⁵ have reported spontaneous respiration with total i.v. anaesthesia and oxygen via HFNC as their institution's favoured technique for tubeless airway surgery, and have suggested it as an alternative to the traditional inhalation induction in obstruction. The advantage of separating routes of anaesthesia and oxygen delivery should mean some issues with inhalation induction, such as achieving insufficient depth, speed of induction, and reversibility, are addressed.

Inhalation induction can work, but may be more likely to fail in patients with more significant obstruction. NAP4 reported 27 cases with inhalation induction, with four proceeding uneventfully. In 12 patients, there was difficulty managing the airway with significant desaturation, and 11 patients where maintenance of spontaneous ventilation was impossible.

Final rescue

The final step in a plan may be most crucial and it is likely to involve a surgical colleague. Their role must be communicated clearly so they are standing ready with specific equipment for surgical front-of-neck access, or with a rigid bronchoscope and an available high-pressure oxygen source. The latter approach may of course come as part of the primary plan in obstruction of the lower airway caused by tracheobronchial lesions.

The performance of a rescue tracheostomy takes too long. A surgical cricothyroidotomy should therefore be considered the technique of choice, especially in cases of hypoxaemia. DAS is currently working with the surgical colleges in the UK to ensure this technique is recognized within their training programmes.

Cardiopulmonary bypass is unrealistic for most scenarios.

Human factors

The management of airway obstruction is stressful and complex. NAP4 reported that human-factor failures contributed to 40% of cases reported, and recommended that human-factor training be part of the ‘corporate mandatory training for all members of staff who work with patients with difficult airways’. The importance of transitions within that strategy cannot be stressed enough. It is important to have delineated the parameters that indicate that one should proceed from one airway plan to another. It may be helpful to have these written on a board or to have an empowered member of staff present specifically to prompt progression through the airway-management strategy.

Conclusions

The management of airway obstruction is a challenging scenario for all anaesthetists, and there is no perfect approach. Oxygenation is the key, and HFNC is becoming a cornerstone of management. The fundamental aspects of managing airway obstruction are defining urgency, describing the expectant pathology, and then formulating with the entire team a series of plans that work best for each particular patient, with the clinicians available. Within any airway-management plan, the non-technical ability of the team to recognize a failing technique and shift focus to an alternative approach is as crucial as the plan itself, and is especially important in these high-risk and dynamic situations.

Acknowledgements

With thanks to Dr Pamela Farquharson and Dr Ben Ulyatt Consultant Anaesthetists, Ninewells Hospital and Medical School, Dundee.

Biographies

Joanna Lynch, MA (Hons) FRCA is a specialty registrar in Anaesthesia at Ninewells Hospital and Medical School. She has an interest in airway management and has completed the NHS Tayside Airway Fellowship.

Simon Crawley, FRCA is a consultant anaesthetist at Ninewells Hospital and Medical School. He specialises in anaesthesia for head and neck surgery, and is secretary of the Scottish Airway Group.

Matrix codes: 1C01, 2A01, 2AO6, 3AO1

Declaration of interest

The authors confirm no interests to be declared.

MCQs

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Appendix A. Supplementary material

The following is the supplementary data related to this article: