The Edge: Does First-Pass Intubation Success Matter?

The Edge is a monthly blog series developed by EMS World and FlightBridgeED that features top EMS medical directors exploring the intricacies of critical care in EMS practice. In this installment FlightBridgeED Chief Medical Director Jeffrey Jarvis, MD, discusses first-pass intubation success in cardiac arrest.  

Endotracheal intubation has long been considered the standard of care for airway management in cardiac arrest. This made perfect sense when the alternatives were “high-tech” devices such as the EGTA (esophageal gastric tube airway) and EOA (esophageal obturator airway). Fortunately we have seen the introduction of alternatives since those dark ages; the question now is whether any of these new devices, such as the King LT or laryngeal mask-type devices such as the i-gel, allow for improved outcomes in cardiac arrest. 

In the past few years, we’ve had two large, well-done randomized controlled trials that have compared patient outcomes between intubation and either the King LT or the i-gel. The PART study was a large multicenter U.S. trial that randomized patients to have either a King LT or endotracheal tube inserted as their initial airway management method. It found increased 72-hour survival of 2.9% in patients managed with the King LT.¹ The AIRWAYS-2 trial was a large multicenter U.K. trial that randomized paramedics to use either intubation or an i-gel as their initial airway device. It found no difference in neurologically intact survival 30 days after arrest.² 

These two trials provide strong evidence that a supraglottic airway (SGA) is at least no worse than intubation and perhaps better. This is important because training to a high degree of competence in intubation is difficult and requires large amounts of resources that might be better applied in other clinical areas. If outcomes are no better with intubation, using an SGA is a reasonable approach. However, a big question remains after these studies. 

More Attempts, Less Chance

Why? Why did we see better survival with the King LT? Why didn’t intubation lead to improved outcomes? After all, we had several observational studies leading up to these trials that suggested better outcomes with intubation.^3–5 

One potential explanation was the poor intubation success seen in both large trials. First-pass success (FPS) was 51% in the PART trial and similar in AIRWAYS-2. This is substantially below the 71% FPS in cardiac arrest reported in a recent national study.⁶ Could low FPS account for the difference in outcomes?

A recent paper from the Seattle Fire Department provides insight.⁷ Emergency physician David Murphy and colleagues analyzed all adult nontraumatic cardiac arrests with at least one intubation attempt made prior to ROSC between 2015 and mid-2019 to determine the association between the number of ETI attempts and neurologically intact survival. 

Overall survival, regardless of initial rhythm or presence of bystander CPR, was 8.1%. They then broke this group up into several buckets based on the number of attempts it took to intubate the patient. Overall, 97% of patients were successfully intubated within four attempts, 3% had an i-gel placed, and fewer than 1% needed a surgical airway. FPS was 63%—still low but higher than in the PART trial. 

Survival among those with FPS was 10.8%, compared with 4.3% with two attempts, 2.6% with three attempts, and 2.0% with four attempts. This demonstrates a very clear and rapid decrease in functional survival with even one missed ET attempt. The survival rate with FPS was 10.8% vs. 3.6% with success on any subsequent attempt.

Murphy and company also assessed the odds of survival with each additional ETI attempt after controlling for all the usual variables, including age, gender, witnessed arrest, bystander CPR and AED use, and initial rhythm. They determined each additional attempt was associated with a 59% decrease in the odds of functional survival (aOR: 0.41; 95% CI: 0.25–0.68). 

Conclusion

This was an observational study, not a randomized controlled trial. That means this information shows correlation only, not causation. It is important to recognize, however, that it would be unethical to intentionally miss an intubation attempt; therefore, we will never see a randomized trial on this question. 

The biggest limitation was that of resuscitation bias. Resuscitation bias is when we falsely attribute an effect to a variable—say, intubation attempts, when it was actually the length of time the patient was in cardiac arrest that made the difference. In this trial each additional attempt was also directly associated with being in arrest for a longer period. Resuscitation bias occurs in almost all observational studies in cardiac arrest. The only way to adequately control for it is with randomization, which we can’t do on this subject. Overall, though, I think we can safely say that additional attempts, at least in part, are driving the decrease in survival.

I think this paper goes a long way toward explaining why we saw improved survival with King LT over intubation in the PART study. First-pass success is important, and failure to achieve it is associated with decreased survival. 

How, then, should we put this information into action in our systems? I think the evidence suggests if your system doesn’t have a strong, documented track record of high first-pass success with intubation, you should stop intubating cardiac arrests and go straight to an SGA. If you do have high performance, you should include protocols that limit the number of ETI attempts before going to a rescue device. My system currently allows two intubation attempts before moving to an i-gel. I’m likely to reduce this to one based on this paper.  

References

1. Wang HE, Schmicker RH, Daya MR, et al. 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. JAMA, 2018; 320: 769–78.

2. Benger JR, Kirby K, Black S, et al. Effect of a strategy of a supraglottic airway device vs tracheal intubation during out-of-hospital cardiac arrest on functional outcome: The Airways-2 randomized clinical trial. JAMA, 2018; 320: 779–91.

3. Benoit JL, Gerecht RB, Steuerwald MT, McMullan JT. Endotracheal intubation versus supraglottic airway placement in out-of-hospital cardiac arrest: A meta-analysis. Resuscitation, 2015; 93: 20–6.

4. Carlson JN, Wang HE. Does Intubation Improve Outcomes Over Supraglottic Airways in Adult Out-of-Hospital Cardiac Arrest. Ann Emerg Med, 2016; 67: 396–8.

5. McMullan J, Gerecht R, Bonomo J, et al.; CARES Surveillance Group. Airway management and out-of-hospital cardiac arrest outcome in the CARES registry. Resuscitation, 2014; 85: 617–22.

6. Jarvis JL, Barton D, Wang H. Defining the plateau point: When are further attempts futile in out-of-hospital advanced airway management. Resuscitation, 2018; 130: 57–60.

7. Murphy DL, Bulger NE, Harrington BM, et al. Fewer Tracheal Intubation Attempts are Associated with Improved Neurologically Intact Survival Following Out-of-Hospital Cardiac Arrest. Resuscitation, 2021 Jul 14; S0300-9572(21)00248-3.

Jeffrey L. Jarvis, MD, MS, EMT-P, FACEP, FAEMS, is chief medical director for FlightBridgeED, LLC and cohost of the FlightBridgeED EMS Lighthouse Project Podcast.