Journal Watch: First-Pass Airway Success and OHCA Outcomes

Reviewed This Month

Airway Insertion First Pass Success and Patient Outcomes in Adult Out-of-Hospital Cardiac Arrest: The Pragmatic Airway Resuscitation Trial 

Authors: Lesnick JA, Moore JX, Zhang Y, et al.

Published in: Resuscitation, 2021 Jan; 158: 151–6. 

This month we review a study that performed a secondary post hoc analysis of data from the Pragmatic Airway Resuscitation Trial (PART). The PART study was a cluster-randomized clinical trial with crossover. 

There’s a lot to unpack in just those two sentences. Let’s start with the study design for PART: The “clusters” were EMS agencies that were divided, by chance, into separate groups to compare different advanced airway management strategies. At defined intervals (3–5 months) there was “crossover,” which means EMS agencies switched airway interventions. PART found that out-of-hospital cardiac arrest (OHCA) patient outcomes were better with a strategy of initial airway management with the King laryngeal tube (KLT) than with initial endotracheal intubation (ETI). 

The secondary post hoc analysis occurred after the data were collected and analyzed. The PART study was designed to evaluate the effect of airway management with initial KLT vs. initial ETI. The study we review this month analyzed data from PART to determine if there was an association between first-pass success (FPS) and OHCA patient outcomes. 

The PART Study 

The PART study enrolled patients from December 1, 2015 to November 4, 2017. There were 27 EMS agencies included from Birmingham (Ala.), Dallas-Fort Worth, Milwaukee, Pittsburgh, and Portland (Ore.). These sites were part of the Resuscitation Outcomes Consortium, which, as we’ve discussed in previous Journal Watch articles, conducted experimental and observational studies of out-of-hospital treatments of cardiac arrest and trauma. The annual 9-1-1 response volumes ranged from 1,200 to 125,000. Agencies operated ALS-only units, both ALS and BLS units, and BLS-only units and provided care in urban, suburban, rural, and combined urban/suburban areas. 

Patients 18 or older who required advanced airway management or BVM were included. Those who were less than 18, pregnant, incarcerated, or victims of traumatic cardiac arrests were excluded. All aspects of airway management and resuscitation care followed local protocol other than the study intervention. Overall airway success was 98% for the KLT and 95% for ETI. 

For the secondary post hoc analysis, the authors included all patients enrolled in PART and sought to determine if there was an association between FPS and OHCA patient outcomes. The relationship between FPS and OHCA outcomes has not been widely studied. However, FPS is emphasized in ETI clinical guidelines, and multiple ETI attempts have been associated with increased rates of adverse events. 

The authors defined an airway attempt for ETI as “a single insertion of the laryngoscope blade into the patient’s mouth” and “passage of the tube past the patient’s teeth” for the KLT. FPS was defined as “cases with successful airway placement and one reported attempt.” 

The primary outcome of interest was 72-hour survival. Secondary outcomes evaluated included ROSC, hospital survival, and hospital survival with favorable neurologic status. The authors performed statistical modeling to evaluate the association between FSP and the primary and secondary outcomes of interest, controlling for airway type (KLT vs. ETI), age, sex, whether the arrest was witnessed by EMS, if bystander CPR was performed, and initial ECG rhythm. 

Results

There were 2,642 patients included in this secondary post hoc analysis. There was no statistically significant difference noted when evaluating FPS and 72-hour survival (AOR 1.22; 95% CI: 0.94–1.58). Furthermore, FPS was not associated with hospital survival to discharge (AOR 0.90; 95% CI: 0.68–1.19) or hospital survival to discharge with favorable neurologic status (AOR 0.66; 95% CI: 0.37–1.19). However, FPS was associated with ROSC (AOR 1.23; 95% CI: 1.07–1.41).

Now, these were certainly surprising results, but the authors did a fantastic job putting them into context. They note that patient outcomes in PART were better with the LT, and it has been suggested this result may be due to the large difference in FPS described in PART (87% for KLT and 48% for ETI). However, the result of this secondary analysis focused on FPS while controlling for airway type, and no association was found, contradicting this theory. 

Again, the secondary post hoc analysis is important to consider. This study evaluated FPS using data that were not originally collected to evaluate FPS. The study was designed to determine if the KLT or ETI led to better patient outcomes. This is extremely important. The sample size calculations, data collection plans, crossover, etc. were all used to evaluate differences in patient outcomes based on airway management technique. Addressing other questions with this data source provides a useful addition to the literature but not a definitive answer to the relationship between FPS and patient outcomes because the study was not designed to evaluate that specific relationship. 

Conclusion

What’s great about this study is that we now understand that among patients enrolled in PART, there are other factors we should examine to fully understand the study results. The authors of this secondary analysis note that chest compressions and ventilation patterns have not been assessed. They were also not able to evaluate airway management protocols, training, or practice patterns among the participating agencies. Further, information regarding whether EMS personnel were intubating during ongoing CPR, the skill levels of providers, and the number of providers on scene was unavailable. All of these are good areas to focus future research. 

This is a manuscript I hope you have an opportunity to read. I commend the authors not only for publishing their work but for doing such a great job contextualizing their results. Like all the best studies, this one leads to more questions.   

First-Pass Success in the PART Study

• Laryngeal tube                                       86.2%

• Endotracheal intubation                         46.7%

• Association with ROSC                          Yes

• Association w/72-hour survival              No

• Association w/hospital survival              No

• Association w/favorable neuro status    No

Antonio R. Fernandez, PhD, NRP, FAHA, is a research scientist at ESO and a member of the board of advisors of the Prehospital Care Research Forum at UCLA.