The Trip Report: Laryngeal vs. Endotracheal Tubes After OHCA

Reviewed This Month

Effect of a Strategy of Initial Laryngeal Tube Insertion vs. Endotracheal Intubation on 72-Hour Survival in Adults With Out-of-Hospital Cardiac Arrest: A Randomized Clinical Trial

Authors: Wang HE, Schmicker RH, Daya MR, et al.

Published in: JAMA, 2018; 320(8): 769–78. 

It’s not often we see articles dedicated to EMS in the top medical journals. When one of them publishes a manuscript discussing prehospital care, we should all know about it. This month we discuss a JAMA manuscript that’s not only interesting but has the potential to change the way we care for victims of out-of-hospital cardiac arrest. 

This study compared laryngeal tube insertion to endotracheal tube insertion. The outcome of interest was 72-hour survival following out-of-hospital cardiac arrest (OHCA).  Past studies have compared alternatives to endotracheal intubation (ETI), and many have reported better outcomes with ETI. However, many of these were also observational studies. Randomized trials represent a higher level of evidence than observational studies. The study we review this month is a randomized trial. In fact, it’s a multicenter cluster-crossover randomized trial. This means they used multiple EMS agencies in their study (multicenter). Typically randomization is done at the patient level; however, for this study the agencies were randomized in groups (clusters) to use either laryngeal tubes (LT) or ETI during OHCA. After a predetermined amount of time, the agencies would switch from one intervention to the other (crossover). 

There were 27 EMS agencies included. These were associated with U.S. Resuscitation Outcomes Consortium (ROC) sites. The ROC is a multicenter network established to conduct OHCA clinical trials. This study was the ROC Pragmatic Airway Resuscitation Outcome Trial (PART). These 27 agencies were split into 13 groups that were randomized to initially use laryngeal tubes or ETI during OHCA. They switched interventions after either 3 or 5 months, and crossover could be assigned more than once. The authors did not indicate which specific laryngeal tube was evaluated in this study; however, they noted they only evaluated the LT “because it is the most commonly used supraglottic airway in the United States.”

The study protocol allowed agencies to use neuromuscular blocking agents or video laryngoscopy, but agencies were only permitted to use either LT or ETI for the initial intubation efforts. If the initial effort was unsuccessful, they were then permitted to use any available airway technique, including the other study intervention, other supraglottic airways, cricothyroidotomy, etc. 

It is important to note that the study did not prescribe what clinical care was delivered at the receiving hospitals. In situations where more than just the EMS agency participating in the study was present on scene, providers from the first-arriving unit determined what treatment was assigned. 

Besides survival to 72 hours after OHCA, the authors also evaluated secondary outcomes such as return of spontaneous circulation, survival to hospital discharge, and favorable neurologic status at discharge.

Last month we discussed an intention-to-treat analysis, and the authors here utilized this same method for their main data analysis. In short, intention-to-treat analyses evaluate data based on what intervention was supposed to be delivered under the initial randomization, rather than evaluating what intervention was actually delivered. The authors also conducted a per-protocol analysis, which removed cases that were out of compliance with their assigned airway group. Cases where only BVM was utilized were considered compliant. They also conducted an as-treated analysis that looked specifically at LT vs. ETI. 

Results

Patients were enrolled in the trial from December 1, 2015 to November 4, 2017. There were 3,004 patients enrolled: 1,505 in the initial LT group and 1,499 in the initial ETI group. Among the LT group the authors found 95% protocol compliance. In other words, 95% utilized LT (or BVM) for their initial attempt. The ETI group had 90.7% compliance. 

With respect to the study’s main outcome of interest, 72-hour survival was higher in the LT group than the ETI group in the intent-to-treat analysis, and the result was statistically significant (18.3% vs. 15.4%, p=0.04). This result was similar in the per-protocol analysis (18.3% vs. 15.4%, p=0.045). In the as-treated analysis, LT seemed to perform better compared to ETI; however, the finding was not statistically significant (16.0% vs. 13.5%, p=0.07). 

The LT group also performed better when evaluating the time from EMS arrival to starting airway management (median 9.8 minutes vs. 12.5 minutes), initial success (90.3% vs. 51.6%), and overall success (94.2% vs. 91.5%). P-values were not reported for time to airway management, initial success, or overall success. There were 352 patients who received BVM only. 

When evaluating the secondary outcomes, the LT group had a higher percentage of ROSC (27.9% vs. 24.3%, p=0.03), hospital survival (10.8% vs. 8.1%, p=0.01), and favorable neurological discharge (7.1% vs. 5.0%, p=0.02).

The results show that LT performed better than ETI in every measure reported in this study. We often discuss the difference between clinical importance and statistical significance. The difference in the main outcome of interest here was about 3%, and it was statistically significant. Now, in some studies a 3% difference may not be clinically important. However, in this study we’re talking about 72-hour survival post-OHCA. “Small” improvements in survival are huge wins! This is a case where the result is not only statistically significant but clinically important as well. 

It is important to note that the main analysis, intent to treat, dictates that the conclusion has to be that an LT-based strategy of advanced airway management is effective. 

Limitations

One limitation to this study is its type. A pragmatic study attempts to evaluate interventions in real-world conditions. Therefore, this study did not provide additional ETI or LT training but rather evaluated these strategies under existing practices and protocols. Randomized controlled trials are expensive to conduct, and there were also some limitations to the number of patients they could enroll, due primarily to limited funding. The authors also noted they could not assess the influence of chest compressions or ventilation quality. They also stated that many aspects of the study were not blinded, meaning bias could have been introduced. 

As always, I hope you can read the manuscript. There are a lot of informative figures and tables as well as a post-hoc analysis we were unable to review.

Antonio R. Fernandez, PhD, NRP, FAHA, is research director at the EMS Performance Improvement Center and an assistant professor in the Department of Emergency Medicine at the University of North Carolina–Chapel Hill.