Comparison of pulmonary dynamic compliance between Laryngeal Mask Airway Supreme^TM and endotracheal intubation during laparoscopic cholecystectomy: study protocol for a non-inferiority, randomized, controlled trial

Abstract

Background

During laparoscopic cholecystectomy, pneumoperitoneum reduces pulmonary compliance, which may result in atelectasis and postoperative hypoxia. The efficacy of laryngeal mask ventilation during laparoscopic surgery is currently up for dispute. The objective of this study is to determine whether a Laryngeal Mask Airway Supreme™ (LMA-S) is non-inferior to an endotracheal tube (ETT) in maintaining lung compliance among low-risk patients undergoing laparoscopic cholecystectomy. The findings could be applied to implement novel airway management strategies for laparoscopic cholecystectomy procedures.

Methods

A total of 100 American Society of Anaesthesiologists Classification (ASA) I–II patients will be randomly allocated to airway management with an LMA-S (L group, n = 50) or an ETT (T group, n = 50). After the induction of general anaesthesia, patients in group L will receive LMA-S, while patients in group T will receive ETT. Lung-protective ventilation strategy (LPVS) will be employed throughout the procedure in both groups. The primary outcome is pulmonary dynamic compliance (Cdyn) 15 min after pneumoperitoneum and up-head position. Secondary outcomes include the oxygenation index (OI), peak inspiratory pressure (PIP), end-expiratory carbon dioxide (EtCO₂), Richmond Agitation-Sedation Scale (RASS) scores, perioperative hemodynamics, and adverse respiratory events.

Discussion

This study will evaluate the effects of LMA-S ventilation on Cdyn and oxygenation in patients undergoing laparoscopic cholecystectomy. Clinical evidence to optimize airway management strategies for low-risk patients undergoing laparoscopic cholecystectomy will be provided by the results.

Trial registration

China Clinical Trial Registry (ChiCTR2400083333). Registered 22 April 2024, https://www.chictr.org.cn.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-026-09650-2.

Introduction

Background and rationale {6a}

As one of the most common laparoscopic surgeries, laparoscopic cholecystectomy (LC) is increasingly being developed as a day surgery which is associated with a shorter hospital stay and faster recovery. Better anaesthetic administration is therefore required for both circulatory and airway management [1]. The laryngeal mask, a supraglottic airway device, has grown in use in general anaesthesia in recent years [2]. The laryngeal mask’s simplicity of use, hemodynamic stability, minimal muscle relaxant, and low incidence of airway complications contribute to it being a popular choice for low-risk patients undergoing laparoscopic cholecystectomy [3, 4]. The Laryngeal Mask Airway Supreme ™ (LMA-S) is an innovative dual-lumen supraglottic airway device (SAD) with a low-pressure balloon and esophageal drain. This device separates the esophagus from the airway and provides a better airway seal, with a leakage pressure of up to 37cmH₂O [5]. Previous clinical research has shown that this device is safe and can lower the risk of reflux aspiration during laparoscopic surgery [6–8], cardiac surgery [9], and procedures performed in various settings, such as the prone position [10]. A systematic review suggests that using a laryngeal mask reduces the incidence of coughing, sore throat, laryngospasm, and hoarseness when compared with using ETT [11]. Thus, laryngeal masks have been acknowledged as a safe substitute for ETT in low-risk patients.

However, pneumoperitoneum during laparoscopic surgery is associated with elevated airway pressures, decreased lung compliance, and barotrauma [12]. The patient’s lung function and oxygenation may be impacted by these modifications in respiratory physiology, which could result in problems such as pulmonary atelectasis and postoperative hypoxia. Therefore, the majority of anaesthesiologists prefer tracheal intubation for airway control and are skeptical about the use of laryngeal masks in laparoscopic surgery. Research contrasting the impact of tracheal intubation and laryngeal masks on respiratory mechanics is still controversial. Mohaghegh MR discovered that LMA ventilation causes lower pulmonary dynamic compliance and greater airway pressures than ETT in an adult population undergoing orthopedic surgery [13]. Therefore, studies on the effect of the laryngeal mask on pulmonary dynamic compliance are controversial, and further research is needed.

In recent years, intraoperative LPVS has been demonstrated to improve lung compliance and lessen ventilator-induced lung injury by using tiny tidal volumes (Vt), proper positive end-expiratory pressure (PEEP), and frequent recruitment manoeuvres (RMs) [14–16]. These procedures are intended to decrease atelectasis, minimize alveolar overdistention, and prevent alveolar collapse and reopening. According to a study, LPVS can greatly enhance pulmonary compliance and intraoperative oxygenation function when utilized in abdominal laparoscopic surgery [17]. However, studies contrasting the ventilatory characteristics of ETT and LMA-S under LPVS during laparoscopic cholecystectomy are fewer. Thus, we hypothesize that, in terms of lung dynamic compliance, LMA-S is not inferior to ETT when used during laparoscopic cholecystectomy under LPVS.

Objectives {7}

The objective of this trial is to determine whether LMA-S is non-inferior to ETT in maintaining lung compliance among low-risk patients undergoing laparoscopic cholecystectomy.

Trial design {8}

This trial is a non-inferiority, prospective, randomized controlled clinical trial. The participants will be randomly allocated into one of two parallel groups in a 1:1 ratio.

Methods: participants, interventions, and outcomes

Study setting {9}

The study will be conducted at a tertiary hospital (Beijing Tongren Hospital, Capital Medical University) in China. One hundred patients undergoing elective laparoscopic cholecystectomy under general anaesthesia will participate in this trial. Patients who fulfil the requirements listed below are given consideration for inclusion. The flowchart is shown in Fig. 1.

Fig. 1.

CONSORT flowchart of the study

Eligibility criteria {10}

Inclusion criteria

Patients must meet the following criteria to be eligible for the study:

1. ASA I-II

2. Age ranges from 18 up to 65 years

3. BMI ranges from 18.5 to 30 kg/m²

4. Anticipated anaesthesia duration of less than 3 h

Exclusion criteria

If the patients meet any of the following criteria at the screening visit, they will not be eligible for the study:

1. Patients at risk of regurgitation/aspiration of gastric contents (full stomach, inadequate fasting, known hiatus hernia, gastroesophageal reflux disease, history of peptic ulcer, pregnancy, previous upper gastrointestinal surgery)

2. Patients with any neck or upper respiratory airway pathology

3. Suspected difficult airway

4. Patients with severe respiratory disease, sore throat, dysphonia, and dysphagia

5. Pregnant and lactating female patients

Who will take informed consent? {26a}

Patients who will undergo elective laparoscopic cholecystectomy under general anaesthesia are screened for eligibility to participate in this study based on the abovementioned criteria. On the day before surgery, every participant will be visited by a trained investigator, introduced to the study process, and sign the informed consent form.

Additional consent provisions for collection and use of participant data and biological specimens {26b}

N/A. This trail does not involve biological specimens. Blood gas samples are available for this study but not for other ancillary studies.

Interventions

Explanation for the choice of comparators {6b}

During laparoscopic surgery, carbon dioxide pneumoperitoneum is utilized. In this procedure, ETT is still regarded as a routine and safe method for managing the airway. Nonetheless, the laryngeal mask has gained popularity for managing airways during general anaesthesia since the creation of the SAD. The LMA-S is an innovative SAD with the main advantages of stable haemodynamic function, high rate of successful placement, and lower incidence of airway complications compared with ETT. The special feature of this laryngeal mask is that there are two outlets at the top, one for ventilation and another for inserting a gastric tube to avoid aspiration in the event of elevated intragastric pressure. Therefore, we chose this type of SAD for comparison with ETT. Patients will be randomly assigned to the ETT group and LMA-S group in a 1:1 ratio.

Intervention description {11a}

Preparation before operation

All patients will receive a preoperative visit the day before surgery. All patients will be fasted for 8 h and abstained from drinking for 2 h preoperatively. Patients will be routinely monitored after admission to the operating room, including electrocardiography, pulse oximetry, and non-invasive blood pressure. We will perform blood gas analysis by proper radial artery puncture placement under local anaesthesia with lidocaine. All patients will be monitored train of four (TOF) neuromuscular. Following preoxygenation with 100% oxygen for 3 min, anaesthesia was induced with midazolam 0.02 mg/kg, propofol 1.5–2 mg/kg, and sufentanil 0.3 μg/kg. The patients will be calibrated for muscle relaxation monitoring after loss of consciousness and subsequently given rocuronium bromide 0.6 mg/kg. When TOF is zero, the appropriate airway device will be inserted using standard methods.

Group L

Based on the manufacturer’s weight-based recommendations, the appropriate size of LMA-S will be chosen. After the device is initially placed, observe if the placement is successful.

Definition of successful placement

The following points must be achieved in two groups: normal tidal volume (difference between actual tidal volume and set tidal volume < 10% of set tidal volume); EtCO₂ (square, regular waveforms); airway pressure waveforms (PIP < 30cmH₂O, waveform is smooth and regular); no air leakage; and symmetrical breath sounds in both lungs. Failure to meet any of the above is considered clinically unsuccessful.

Furthermore, as for LMA-S, after meeting clinical success, exposure grading will be observed with fibreoptic.

Grade I, the glottis is visible; Grade II, the glottis and epiglottic laryngeal surface are visible; Grade III, the glottis, tip of the epiglottis, or epiglottic tongue is visible, with less than 50% of the field of view from the epiglottis to the glottis obscured; Grade IV, the epiglottis is collapsed downward, the tongue is visible, and more than 50% of the field of view from the epiglottis to the glottis is obscured; Grade V, the epiglottis is collapsed downward, with the glottis inaccessible to the direct view. Grade I, II, and III are considered successful in position. Both clinical success and positional success should be met for LMA-S.

After successful placement, measure the oropharyngeal leakage pressure (OLP), inflate the laryngeal mask balloon by 15–30 ml in order to achieve a balloon pressure of 50 cmH₂O, set the anaesthesia machine’s APL valve to 40 cmH₂O in the manual ventilation mode, close the expiratory valve, set the fresh gas flow rate of 3 L/min, and wait for the leakage of the oropharynx to occur when the pressure is airway sealing pressure. If the airway pressure is ≥ 40 cmH₂O, stop the pressure measurement, and record the airway seal pressure as 40 cmH₂O. After pneumoperitoneum and up-head position, the leakage pressure will be measured in the same way.

Group T

ETT size will be selected based on gender and patient anatomy: 7.0–7.5 mm internal diameter for females and 7.5–8.0 mm for males. Following induction of anaesthesia and muscle relaxation, endotracheal intubation will be performed under direct laryngoscopy with Macintosh blade size 3 or 4 by experienced anaesthesiologists (> 5 years of practice). The ETT cuff will be inflated to maintain a pressure of 20–25 cmH₂O, monitored using a standard cuff pressure manometer. Correct tube placement will be confirmed by bilateral chest auscultation, capnography showing square-waveform end-tidal CO₂ tracing, and visualization of the tube passing through the vocal cords. The ETT depth will be set at 21–23 cm at the incisors for adult patients, with final positioning confirmed by bilateral equal breath sounds.

Similar to the LMA-S group, fibreoptic bronchoscopic verification will be performed to document tube position relative to the carina, with ideal positioning defined as the ETT tip located 3–5 cm above the carina. The same criteria for clinical success will apply: normal tidal volume (difference between actual and set tidal volume < 10%), square regular capnography waveform, peak inspiratory pressure < 30 cmH₂O with smooth waveform, no air leak, and symmetrical bilateral breath sounds.

Maintenance of general anaesthesia

Anaesthesia will be maintained with propofol infusion at 6–8 mg/kg/h, combined with remifentanil infusion at 0.1–0.3 μg/kg/min with the depth of anaesthesia between Bispectral index (BIS) 40–60. Neuromuscular monitoring will be used in all patients during the procedure. During the operation, the dose of the drug will be maintained to adjust the mean arterial pressure within the baseline value ± 20%. Phenylephrine will be pumped intravenously if mean arterial blood pressure (MAP) is 20% lower than baseline blood pressure. If heart rate (HR) is below 50 bpm, 0.3–0.5 mg of atropine will be administered intravenously. Based on the results of inotropic monitoring, additional rocuronium bromide 0.2 mg/kg was added to maintain inotropy when T4 was present, and the expected remaining operative time exceeded 30 min. Before the end of the operation, flurbiprofen axetil 50 mg and ondansetron 8 mg will be given. The pneumoperitoneum pressure is uniformly set at 12 mmHg, and the CO₂ flow rate during pneumoperitoneum is 1 L/min.

Lung protection ventilation management

All patients will be ventilated in volume-controlled mode, with VT 6 ml/kg ideal body weight (IBW), inhaled oxygen concentration (FiO₂) 60%, inhalation/exhalation ratio (I: E) = 1:2, PEEP 5cmH₂O, respiratory rate (RR) 12–20 breaths/minute, to maintain a suitable end-expiratory carbon dioxide partial pressure of 35–45 mmHg. Recruitment manoeuvers will not be performed during the surgical phase prior to the primary outcome measurement at T4 (15 min after pneumoperitoneum) to avoid transient changes in compliance. A single RM will be administered before airway device removal at the end of surgery to address postoperative atelectasis.

Postoperative management

Before the end of the surgery, RMs will be performed before removing the airway device, the anaesthesia machine is set to manual mode, the reservoir bag was inflated to a peak inspiratory pressure of 30 cmH₂O for 20–30 s and repeat this procedure three times. At the end of surgery, atropine 0.5 mg compounded with neostigmine 1 mg will be given to antagonize muscle relaxation. When the TOFR is > 0.9 and consciousness recovers, the airway device will be withdrawn, and the patient will be transferred to the postanaesthesia care unit (PACU) for observation. The patients will receive mask oxygen during PACU. After the patient’s vital signs are stable and off mask oxygen for 15 min, arterial blood will be collected for blood gas analysis. If there are no other complications or accidents, the patient will be sent back to the ward.

Criteria for discontinuing or modifying allocated interventions {11b}

Patients can leave the study at any time for any reason if they wish to do so without any consequences. The patient’s participation in this study can also be ended by the investigator if the patient is uncooperative and/or does not attend study visits. In case of excessive missing data (e.g. missing patients from baseline and postoperative follow-up, intraoperative anaesthesia machine malfunction issues), patients will be replaced by new patients. If an intraoperative adverse event occurs, such as a serious adverse event (SAE) based on an allergic reaction, the study is terminated early.

If these events occur intraoperatively, they will be dealt with promptly as follows:

• Failure of laryngeal mask placement

  Patients with LMA-S can be switched to endotracheal intubation if three attempts are unsuccessful. Such patients will remain in the LMA-S group for the primary intention-to-treat (ITT) analysis. A per-protocol (PP) sensitivity analysis will exclude these patients to assess the impact of protocol deviations.

• Treatment of severe hypercapnia (blood gas analysis PaCO2 > 50 mmHg): Gradually increase RR to 20 bpm.

• The presence of any of the following may be managed at the anaesthetist’s discretion.

• AWhen systolic blood pressure is < 90 mmHg or falls more than 30% of the baseline, it may be raised to 90 mmHg and above using fluid therapy and/or vasoactive drugs.
• BDuring induction of anaesthesia, if the MAP was 20% lower than the baseline, ephedrine 6 mg was administered intravenously. If the HR was less than 50 beats per minute, 0.3–0.5 mg atropine was administered intravenously.

Strategies to improve adherence to interventions {11c}

Since there is only one study intervention, ETT or LMA-S, there were no strategies to improve adherence.

Relevant concomitant care permitted or prohibited during the trial {11d}

Patients will be encouraged to perform activities and deep breathing exercises early after surgery.

Provisions for post-trial care {30}

Participants will have access to study clinics for post-trial care through the routine health system.

Outcomes {12}

Primary outcome

Cdyn at T4

Secondary outcomes

• aOI
• bPIP, EtCO₂ at T1–T6
• cRASS score during PACU
• dAdverse respiratory events (e.g. hypoxemia, laryngospasm, bronchospasm, aspiration) occurring within 24 h postoperatively. Detailed operational definitions with specific diagnostic thresholds for all respiratory adverse events are provided in Supplementary Table 1. For example, hypoxemia is defined as peripheral oxygen saturation (SpO₂) < 90% for > 30 s, requiring clinical intervention
• eHoarseness, dysphagia, sore throat (VAS score 0–10), and other major complications occurring within 24 h postoperatively
• fQoR-15 score at 24 h postoperatively

Security indicators

• Blood pressure (BP), heart rate (HR), and mean arterial pressure (MAP)

Data collections will be done during the following time points

• Baseline, before induction of anaesthesia (T1)

• 5 min after successful airway device placement (T2)

• Post pneumoperitoneum up-head position 5 min (T3), 15 min (T4), and 30 min (T5)

• Pneumoperitoneum stop (T6)

The primary outcome (Cdyn) and secondary outcomes (PIP, EtCO₂) are automatically recorded by the anaesthesia machine. A blinded research assistant will extract these parameters from the machine’s digital output and document them in the case report form. To ensure blinding, the airway device type is not displayed during data extraction.

The data collected or calculated will be the following:

• Cdyn, PIP, and EtCO₂ will be measured on the ventilator and recorded at T2–T6 respectively

• OI will be calculated as PaO₂/FiO₂ and recorded at T1, T4, and PACU

• Hemodynamic indices will be recorded at T1–T6 and PACU

Participant timeline {13}

Recorded time points are shown in Table 1.

Table 1.

Schedule of assessments

Time point	Enrollment −1d	Allocation 0	Primary study periods							Follow-up
			T1	T2	T3	T4	T5	T6	PACU	POD1
Enrolments
Informed consent	✖
Allocation		✖
interventions
Airway device			✖
Assessments
Baseline	✖
Respiratory parameters				✖	✖	✖	✖	✖
Oxygenation index			✖			✖			✖
Hemodynamics			✖	✖	✖	✖	✖	✖	✖
RASS score									✖
Respiratory adverse events									✖	✖
QoR-15 score										✖

Sample size {14}

SPSS 27.0 statistical software was used to calculate the sample size. Based on a pilot study, the Cdyn in the LMA-S group was 32.75 ± 5.18 mL/cmH₂O at 15 min after pneumoperitoneum, and 33.25 ± 6.87 mL/cmH₂O in the endotracheal tube group. The non-inferiority margin (Δ) was set at 4 mL/cmH₂O. This margin was justified clinically and statistically: (1) it represents a conservative estimate relative to the pooled standard deviation (approximately 6 mL/cmH₂O), corresponding to 0.6–0.8 times the SD, which is within the common range for non-inferiority trials; (2) while no established minimal clinically important difference for Cdyn exists in laparoscopic cholecystectomy, a change of 4 mL/cmH₂O is considered meaningful as it may reflect alterations in respiratory mechanics linked to postoperative complications. With a one-sided α of 0.025 and power (1–β) of 0.8, at least 48 patients per group were required. Accounting for a potential 5% dropout rate, the total sample size was increased to 100 patients (50 per group).

Recruitment {15}

Patients will be recruited at the Department of General Surgery, Beijing Tongren Hospital, Capital Medical University.

Assignment of interventions: allocation

Sequence generation {16a}

The participants will be randomly allocated into one of two groups in a 1:1 ratio, the LMA-S group (group L, n = 50) and the ETT group (group T, n = 50), based on numbers generated from a random number table by SPSS 27.0.

Concealment mechanism {16b}

The random numbers will be kept in opaque, sequentially numbered, sealed envelopes that will be opened in the operating room by the anaesthesiologist, just before the induction of general anaesthesia.

Implementation {16c}

Allocation sequence will be performed by a researcher not involved in the anaesthesia. Before the induction of general anaesthesia, the anaesthesiologist will assign participants to interventions according to the random numbers that are kept in sealed envelopes.

Assignment of interventions: blinding

Who will be blinded {17a}

Patients, outcome assessors, data analysts, and surgeons will be blinded. Anaesthesiologists will not be blinded, as the intervention will be performed by anaesthesiologists. A dedicated research assistant, who is not involved in anaesthesia management and is blinded to group allocation, will be responsible for extracting and recording the primary outcome data (Cdyn, PIP, EtCO₂) directly from the anaesthesia machine at predefined time points. This ensures that the outcome assessor remains blinded throughout the data collection process.

Procedure for unblinding if needed {17b}

There are no special criteria for unblinding. The Principal investigator (PI) and Institutional Review Board (IRB) will be notified immediately if any serious adverse event occurs (such as reflux and aspiration, allergic reactions) intraoperatively, postoperatively, and during follow-up. The IRB and PI have the right to unblind if necessary.

Data collection and management

Plans for assessment and collection of outcomes {18a}

All patient information, including preoperative consultation, anaesthesia records, hospitalization records, and postoperative follow-up, will be followed up continuously during the study. All data for the patient will be recorded on the case report form (CRF) and kept by a dedicated person. Preoperative baseline data will be derived from the electronic medical record. All intraoperative data will be collected from the anaesthesia machine. Blood gas analysis will be tested and recorded in the central operating theatre. One investigator will be responsible for intraoperative data collection, following the patient throughout the procedure, entering the operating theatre and PACU, recording the relevant data into a paper CRF, conducting postoperative follow-up and recording the follow-up data into a CRF. All patients’ data will be anonymized and saved in a study folder on our protected research server. Only the study team has access to this specific study folder.

Plans to promote participant retention and complete follow-up {18b}

The patients will receive extensive information about the study set-up and requirements during the preoperative visit. The importance of completing the follow-up will be stressed. Patients are allowed to stop at any time during the study and are not obliged to give a reason to discontinue. Follow-up will be completed in time by the follower. If the patient is discharged from the hospital, he or she will be followed up by telephone. Throughout the follow-up period, the researchers will check for responses.

Data management {19}

The data entry and management should be carried out by the investigator of the research group. The investigators will record the data in the paper CRF during intraoperative and postoperative follow-ups, and later enter them into a spreadsheet. Another investigator will check the data. To avoid input errors, data entry will be performed using the two-person double-entry principle, whereby two data-entry personnel enter data independently and synchronously. Data will be managed using an electronic data collection management system. Individual participant data will be uploaded to Research Manager. All the data is available after obtaining permission from the corresponding author, and researchers can have access rights to enable international prospective meta-analyses.

Confidentiality {27}

Research data will be stored using a study identification code for each participant. The key to the identification code list will only be available to the research team during the study and will be documented and safeguarded by the Principal investigator according to research guidelines after completion of the study. No patient identification details will be reported in publications.

Plans for collection, laboratory evaluation and storage of biological specimens for genetic or molecular analysis in this trial/future use {33}

N/A. Patient arterial blood will be destroyed immediately after blood gas analysis.

Statistical methods

Statistical methods for primary and secondary outcomes {20a}

The primary outcome indicator of this study is pulmonary dynamic compliance, a quantitative indicator. Secondary outcome indicators include the oxygenation index, RASS score, haemodynamic, and QoR-15 score, which are quantitative indicators. The quantitative indicator is expressed as mean ± standard deviation or median (interquartile range, IQR). Categorical data will be expressed as numbers (percentages). Quantitative indicators are tested by independent samples t-test or Mann–Whitney U-test depending on the distribution of the data.

In this non-inferiority trial, the primary outcome indicator was a high superiority indicator, meaning that larger values are better. The upper or lower limit of the 95% confidence interval will be used to assess whether the experimental group qualifies as non-inferiority compared to the cut-off value. Non-inferiority is established if the lower limit of the 95% confidence interval is greater than the margin of non-inferiority and the 95% interval includes zero [18]. A hierarchical testing procedure will be allowed, with a test for superiority following the test for non-inferiority, if the p for non-inferiority is < 0.025.

Adverse respiratory events on admission to the PACU and in the 24 h postoperative period will be analysed as rate ratio (%) descriptors. All SAEs will be summarised and recorded including the nature, date and time of onset, date of resolution, determination of seriousness, severity, action taken, outcome, and possible causality to study treatment. SAE data will be presented in a descriptive manner. Data will be analysed using IBM SPSS 27.0.

The primary analysis will follow the intention-to-treat (ITT) principle, including all randomized participants in their originally assigned groups. A per-protocol (PP) analysis will be conducted as a sensitivity measure, excluding participants with major protocol deviations (e.g. crossover from LMA-S to ETT due to insertion failure, violation of ventilation strategy, or use of prohibited interventions). The ITT analysis preserves randomization and provides a conservative estimate of non-inferiority under real-world conditions, while the PP analysis evaluates the efficacy under perfect adherence. The results from both analyses will be reported, and any discrepancies will be discussed in the context of potential confounding.

Interim analyses {21b}

N/A. There are no interim analyses planned.

Methods for additional analyses (e.g. subgroup analyses) {20b}

N/A. There is no subgroup analyses planned.

Methods in analysis to handle protocol non-adherence and any statistical methods to handle missing data {20c}

In this study, the primary outcome will be assessed using an ITT analysis. In the ITT analysis, participants who cross over from LMA-S to ETT will be retained in the LMA-S group. While this may dilute the treatment effect if the outcomes are measured under ETT ventilation, it reflects a pragmatic clinical scenario. The PP analysis will provide a complementary perspective by restricting the analysis to participants who fully adhered to the protocol. This dual approach is consistent with recommendations for non-inferiority trials. We expect very few patients to be lost to follow-up during the hospital stay. As a result, the missing data will be minimized when analyzing primary outcomes. Multiple imputation will be used to handle missing data if needed.

Plans to give access to the full protocol, participant level data, and statistical code {31c}

The datasets used and/or analysed during the current study can be made available by the corresponding author upon reasonable request.

Oversight and monitoring

Composition of the coordinating centre and trial steering committee {5d}

Coordinating centre: This is a single-centre study designed, performed, and coordinated in the Beijing Tongren Hospital, Capital Medical University. There is no trial steering committee or stakeholder and public involvement group.

Day-to-day support for the trial is provided by the following:

• Principal investigator: take supervision of the trial and medical responsibility for the patients.

• Data manager: organise data capture, safeguard quality and data, analyse the data.

• Study coordinator: take responsibility for ethics registration, trial registration, and safety reports.

• Study physicians: identify potential recruits, take informed consent, ensure intervention, and follow-up according to protocol.

The study team meets biweekly.

Composition of the data monitoring committee, its role and reporting structure {21a}

The Data Monitoring Committee (DMC) consists of an anaesthesiologist, an ethics expert, and a clinical trial management expert. All DMC members are independent of the study team and have no conflicts of interest with the trial investigators or sponsor. The DMC will meet quarterly to review accruing data on study progress, participant safety, protocol adherence, and preliminary outcomes. Prespecified stopping rules include the following: (1) occurrence of ≥ 3 serious adverse events (SAEs) definitively related to the airway management intervention; (2) protocol violations exceeding 15% of enrolled participants. The DMC will provide recommendations to the Principal investigator regarding study continuation, modification, or termination based on their review.

Adverse event reporting and harms {22}

When SAEs occur, the investigator will immediately report them to the DMC and the ethics committee. The researcher will record in the CRF the symptoms, signs, severity, duration, active management measures taken, results of the management, and the relevance of this experimental intervention and submit the complete SAEs report form to the research panel within 24 h. Patients who experience SAEs will be followed by the researchers until the adverse events are resolved and return to baseline levels.

Frequency and plans for auditing trial conduct {23}

This study is not a clinical drug study; there are no safety risk issues associated with new or unlisted drugs. LMA-S is now fully marketed and widely used in the clinic, so there is no specific monitor established for this study.

Plans for communicating important protocol amendments to relevant parties (e.g. trial participants, ethical committees) {25}

The protocol, the informed consent document, and relevant supporting information must be submitted to the Ethics Committee (EC) for review and must be approved before the study is initiated. The Principal investigator is responsible for keeping the EC informed of the progress of the study and any appropriate changes to the protocol.

Dissemination plans {31a}

Publication in a peer-reviewed journal is also planned.

Discussion

This trial is designed to determine whether LMA-S is non-inferior to ETT on maintaining pulmonary dynamic compliance under LPVS and to assess metrics related to oxygenation, airway complications, and postoperative agitation.

Few research has examined respiratory mechanics, even though numerous investigations on airway management in laparoscopic surgery have demonstrated that laryngeal mask safety can be ensured during laparoscopic surgery. Lee JE et al. found SAD is a safe alternative for tracheal intubation in laparoscopic renal donor resection, reducing airway resistance and increasing pulmonary compliance [19]. A study comparing laryngeal masks and tracheal intubation showed that effective lung ventilation was achieved with the LMA-S during laparoscopic cholecystectomy [20]. But this study only focused on the quality of the laryngeal mask seal (the difference between inhaled and exhaled tidal volumes) and PIP. In our study, we aim to further explore the difference of Cdyn and OI between LMA-S and tracheal intubation.

Firstly, Cdyn is an important index for assessing the effectiveness of ventilation that strongly correlates with postoperative lung function [21]. Pulmonary compliance, defined as the change in lung volume with pressure change, means the effect of a change in thoracic pressure on lung volume. Reduced dynamic compliance is clinically linked to lung damage, which is typified by non-specific hypoxemia and decreased lung volumes. Studies have shown that pulmonary compliance decreases with prolonged pneumoperitoneum time [22]. Therefore, we observe compliance in a short-time cholecystectomy, and the primary outcome time point is set at 15 min after pneumoperitoneum, which excludes interference due to prolonged pneumoperitoneum.

Secondly, we will measure the oxygenation index to explore the effects of both airway devices on ventilation and oxygenation. The oxygenation index may indicate atelectasis. In patients undergoing general anaesthesia with mechanical ventilation, local alveolar non-ventilation occurs in about 75% of patients during surgery. The establishment of pneumoperitoneum in LC causes serious interference with pulmonary function. It affects diaphragm elevation, increasing the ventilation pressure, which may damage the lungs and increase the occurrence of postoperative pulmonary dysfunction. It also decreases lung residual air volume and pulmonary compliance, results in local atelectasis, which can lead to ventilation/blood flow imbalance and intrapulmonary shunting, and even induce hypoxemia, increasing the possibility of hypoxemia after the surgery. Therefore, perioperative pulmonary protection anaesthetic management is essential to rapid postoperative recovery. There is evidence to support the assertion that LPVS can lower the frequency of postoperative pulmonary problems and hypoxemia. A randomized controlled trial showed that intraoperative oxygenation and Cdyn were significantly higher in the LPVS group than in the conventional ventilation group for abdominal laparoscopic surgeries [23]. A systematic review also found that intraoperative use of lung-protective ventilation can reduce the incidence of postoperative pulmonary complications [24]. Pulmonary protective ventilation is now considered beneficial in patients with healthy lung under general anaesthesia in ETT. Low tidal volume can significantly reduce the incidence of ventilator-associated lung injury and reduce mortality. RMs are beneficial in reopening collapsed alveoli. A reasonable PEEP should maintain and prevent alveolar collapse, improving hypoxia. Our LPVS protocol prioritized the maintenance of low Vt and PEEP during the critical phase of pneumoperitoneum, with RMs deferred until surgery conclusion. This design ensured that the primary outcome measurement at T4 was not influenced by the transient effects of RMs, allowing a valid comparison of pulmonary compliance between the LMA-S and ETT groups under consistent ventilatory conditions. This approach is aligned with methodologies used in comparable trials. Moreover, it has been shown that there is a correlation between intra-abdominal pressure and patient pulmonary compliance during laparoscopic surgery [25]. Pneumoperitoneum can increase intrathoracic pressure, which is associated with dead space ventilation. This is due to the compression of pulmonary capillary vessels, which also leads to decreased PaO₂. The pneumoperitoneum pressure will be uniformly set at 12 mmHg, and a CO₂ flow rate of 1 L/min in this trial. Lastly, we will ensure LMA-S placement meets both clinical and positional success criteria. Clinical success ensures effective ventilation, and a fibreoptic scope will verify positional success.

In conclusion, the results of this study will be published in an international peer-reviewed journal. The results may provide clinical evidence to optimize perioperative airway management protocols for laparoscopic surgery.

Trial status

Protocol version number V2.0/20 November 2023.

Date recruitment started, 8 January 2024.

Date of anticipated completion, 31 December 2024.

Abbreviations

ASA

American Society of Anaesthesiologists Classification

BIS

Bispectral index

CRF

Case report form

Cdyn

Dynamic compliance

DMC

Data Monitoring Committee

EC

Ethics Committee

ETT

Endotracheal intubation

EtCO₂

End-expiratory carbon dioxide

FiO₂

Fraction of inspired oxygen

HR

Heart rate

IBW

Ideal body weight

I: E

Inhalation/exhalation ratio

IRB

Institutional Review Board

IQR

Interquartile range

ITT

Intention-to-treat

LC

Laparoscopic cholecystectomy

LPV

Lung-protective mechanical ventilation

LMA-S

Laryngeal Mask Airway Supreme™

MAP

Mean arterial blood pressure

OI

Oxygenation index

OLP

Oropharyngeal leakage pressure

PACU

Postanaesthesia care unit

PEEP

Positive end-expiratory pressure

PIP

Peak inspiratory pressure

PI

Principal investigator

QoR-15

Quality of Recovery-15

RASS

Richmond Agitation-Sedation Scale

RR

Respiratory rate

RMs

Regular recruitment manoeuvres

SAEs

Serious adverse events

SAD

Supraglottic airway device

TOF

Train of four

Vt

Tidal volumes

Authors’ contributions {31b}

GY W is the Principal investigator for this trial. WJ S drafted the manuscript. GY W, CH X, and X L contributed to the study design. GY W and CH X revised and edited the manuscript. WJ S, X L, and JY Z collected and interpreted the data. CH X and X L are the statisticians responsible for the sample size calculation and the statistical design of the study. All the authors have read and approved the final manuscript.

Funding {4}

This study is supported by Beijing Hospitals Authority’s Ascent Plan (Code: DFL20220203). The funding agents have no influence on the design of the study, data collection, results, or publication.

Data availability {29}

The datasets analysed during the current study and statistical code are available from the corresponding author upon reasonable request, as is the full protocol and any data needed to support the protocol can be supplied upon request.

Declarations

Ethics approval and consent to participate {24}

The study protocol version 2.0 was approved by the Ethics Committee of Beijing Tongren Hospital (TREC2023-KY122). Informed consent will be obtained from each patient.

Consent for publication {32}

Not applicable.

Competing interests {28}

The authors declare that they have no competing interests.