Supraglottic airway device versus tracheal intubation in the initial airway management of out-of-hospital cardiac arrest: the AIRWAYS-2 cluster RCT
Authors: Benger Jonathan R , Kirby Kim , Black Sarah , Brett Stephen J , Clout Madeleine , Lazaroo Michelle J , Nolan Jerry P , Reeves Barnaby C , Robinson Maria , Scott Lauren J , Smartt Helena , South Adrian , Stokes Elizabeth A , Taylor Jodi , Thomas Matthew , Voss Sarah , Wordsworth Sarah , Rogers Chris A 
Published: April 2022

Background
When a cardiac arrest occurs, cardiopulmonary resuscitation should be started immediately. However, there is limited evidence about the best approach to airway management during cardiac arrest.

Objective
The objective was to determine whether or not the i-gel® (Intersurgical Ltd, Wokingham, UK) supraglottic airway is superior to tracheal intubation as the initial advanced airway management strategy in adults with non-traumatic out-of-hospital cardiac arrest.

Design
This was a pragmatic, open, parallel, two-group, multicentre, cluster randomised controlled trial. A cost-effectiveness analysis accompanied the trial.

Setting
The setting was four ambulance services in England.

Participants
Patients aged ≥ 18 years who had a non-traumatic out-of-hospital cardiac arrest and were attended by a participating paramedic were enrolled automatically under a waiver of consent between June 2015 and August 2017. Follow-up ended in February 2018.

Intervention
Paramedics were randomised 1 : 1 to use tracheal intubation (764 paramedics) or i-gel (759 paramedics) for their initial advanced airway management and were unblinded.

Main outcome measures
The primary outcome was modified Rankin Scale score at hospital discharge or 30 days after out-of-hospital cardiac arrest, whichever occurred earlier, collected by assessors blinded to allocation. The modified Rankin Scale, a measure of neurological disability, was dichotomised: a score of 0–3 (good outcome) or 4–6 (poor outcome/death). The primary outcome for the economic evaluation was quality-adjusted life-years, estimated using the EuroQol-5 Dimensions, five-level version.

Results
A total of 9296 patients (supraglottic airway group, 4886; tracheal intubation group, 4410) were enrolled [median age 73 years; 3373 (36.3%) women]; modified Rankin Scale score was known for 9289 patients. Characteristics were similar between groups. A total of 6.4% (311/4882) of patients in the supraglottic airway group and 6.8% (300/4407) of patients in the tracheal intubation group had a good outcome (adjusted difference in proportions of patients experiencing a good outcome: –0.6%, 95% confidence interval –1.6% to 0.4%). The supraglottic airway group had a higher initial ventilation success rate than the tracheal intubation group [87.4% (4255/4868) vs. 79.0% (3473/4397), respectively; adjusted difference in proportions of patients: 8.3%, 95% confidence interval 6.3% to 10.2%]; however, patients in the tracheal intubation group were less likely to receive advanced airway management than patients in the supraglottic airway group [77.6% (3419/4404) vs. 85.2% (4161/4883), respectively]. Regurgitation rate was similar between the groups [supraglottic airway group, 26.1% (1268/4865); tracheal intubation group, 24.5% (1072/4372); adjusted difference in proportions of patients: 1.4%, 95% confidence interval –0.6% to 3.4%], as was aspiration rate [supraglottic airway group, 15.1% (729/4824); tracheal intubation group, 14.9% (647/4337); adjusted difference in proportions of patients: 0.1%, 95% confidence interval –1.5% to 1.8%]. The longer-term outcomes were also similar between the groups (modified Rankin Scale: at 3 months, odds ratio 0.89, 95% confidence interval 0.69 to 1.14; at 6 months, odds ratio 0.91, 95% confidence interval 0.71 to 1.16). Sensitivity analyses did not alter the overall findings. There were no unexpected serious adverse events. Mean quality-adjusted life-years to 6 months were 0.03 in both groups (supraglottic airway group minus tracheal intubation group difference –0.0015, 95% confidence interval –0.0059 to 0.0028), and total costs were £157 (95% confidence interval –£270 to £583) lower in the tracheal intubation group. Although the point estimate of the incremental cost-effectiveness ratio suggested that tracheal intubation may be cost-effective, the huge uncertainty around this result indicates no evidence of a difference between groups.

Limitations
Limitations included imbalance in the number of patients in each group, caused by unequal distribution of high-enrolling paramedics; crossover between groups; and the fact that participating paramedics, who were volunteers, might not be representative of all paramedics in the UK. Findings may not be applicable to other countries.

Conclusion
Among patients with out-of-hospital cardiac arrest, randomisation to the supraglottic airway group compared with the tracheal intubation group did not result in a difference in outcome at 30 days. There were no notable differences in costs, outcomes and overall cost-effectiveness between the groups.

Future work
Future work could compare alternative supraglottic airway types with tracheal intubation; include a randomised trial of bag mask ventilation versus supraglottic airways; and involve other patient populations, including children, people with trauma and people in hospital.

Trial registration
This trial is registered as ISRCTN08256118.

Funding
This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and supported by the NIHR Comprehensive Research Networks and will be published in full in Health Technology Assessment; Vol. 26, No. 21. See the NIHR Journals Library website for further project information.