Supraglottic vs. Intubation
Taylor J, Black S, Brett SJ, et al. Design and implementation of the AIRWAYS-2 trial. A multi-centre cluster randomised controlled trial of the clinical and cost effectiveness of the i-gel supraglottic airway device versus tracheal intubation in the initial airway management of out of hospital cardiac arrest.Resuscitation. 2016;109:25–32.
As the debates about endotracheal intubation (ETI) continue in EMS crew quarters and medical director offices, South Western Ambulance Service National Health Service (NHS) Foundation Trust in Exeter, England, is taking the lead on a multicenter randomized controlled trial comparing the use of the i-gel supraglottic airway (SGA) device to ETI in out-of-hospital cardiac arrest.
Background: Current data show a 7–9% survival-to-discharge rate for out-of-hospital cardiac arrests. Researching cardiac arrest care is a complex endeavor. The causes and survival of arrests are multifactorial, the care provided is difficult to track accurately, and randomizing as well as obtaining patient consent can challenge even experienced researchers.
The AIRWAYS-2 trial is underway to compare the use of i-gel SGA vs. ETI and this study outlines the trial’s design. Researchers obtained ethics approval in September 2014 and starting collecting data in June 2015. They hope to enroll more than 9,000 cardiac arrest patients treated by 1,300 paramedics from four different ambulance services by July 2017 to complete the study.
Methods: The authors first conducted a feasibility study in 2013. REVIVE-Airways was a 12-month randomized trial to compare the i-gel and laryngeal mask airway (LMA) at a single ambulance service in the U.K. and researchers recruited paramedics to participate in a randomized trial. They concluded the trial was feasible and moved to implement a larger multicenter study.
Comparing two therapies in the complex and incredibly dynamic world of cardiac arrest research is complex, and powering the study correctly is essential. The authors calculated that a 2% improvement in survival to discharge by one device vs. another would be considered clinically significant. “Good neurological outcome” in this study means a modified Rankin Scale (mRS) score of 0–3. The mRS score is a widely used and validated scale that gives us a known comparison to other research. An mRS of 0 means the patient survives neurologically intact and a score of 6 means the patient didn’t survive.
To detect a 2% change in outcomes, the authors calculated that a total of 9,070 patients would need to be included in this study. Since U.K. paramedics see an average of 0–3 cardiac arrests a year, 1,300 paramedics would need to be recruited and followed for two years—that’s roughly 30% of the paramedics at these four participating services.
Researchers are using a computer to randomize providers into two clusters: i-gel or ETI. Providers are required to use the technique they’ve been assigned as their initial airway of choice for the duration of the two-year study.
The robust design includes keeping both the researchers and participants blinded to the results until the trial is over. This ensures providers don’t deviate from protocol and start self-selecting whom they prefer to intubate based on bias or early, non-definitive results.
This type of double-blind study requires someone to peek at the data to ensure neither intervention is harming patients. To achieve this, a separate committee meets at key points to analyze preliminary results.
Related study: The Resuscitation Outcomes Consortium’s (ROC) Pragmatic Airway Resuscitation Trial (PART) is a similar trial to AIRWAYS-2, comparing cardiac arrest survival using an SGA—the King LT—vs. ETI. Henry Wang, MD, MS, a prolific researcher based in Alabama, is leading this effort of more than 30 EMS services in six U.S. cities.
Unlike AIRWAYS-2, randomization is done in clusters by regions or stations, and PART will only follow patients to 72-hour survival. Nearly 10,000–20,000 cases will be needed to achieve significance, and the trial won’t provide additional training in order to focus on real-world contexts and clinically relevant outcomes. PART will wrap up in October 2017.
Conclusion: The design of AIRWAYS-2 indicates that a rigorous scientific process is being followed. We look forward to reading the results of both AIRWAYS-2 and PART, and will report on both as soon as results are available.
What we already know: Use of ETI in the context of out-of-hospital cardiac arrest has been controversial and its value questioned.
What this study adds: These studies will help compare ETI vs. SGAs.
The Journal Club of Prehospital Care Research Forum (PCRF) is hosting a live podcast to further discussion on this topic. PCRF will be joined by two special guests from the Airways 2 Research Project in the UK: Kim Kirby, lead research paramedic of the South Western Ambulance Service NHS Foundation Trust; and Professor Johnathan Benger, chief investigator and professor of emergency care at the University of West England, Bristol.
The podcast will be held Jan. 9, 2017 at 9am CST (GMT -06:00). Register here.
Learn more from David Page at the EMS Today Conference & Exposition, Feb. 23–25, in Salt Lake City. EMSToday.com