Airway has been paramount to the management of cardiac arrest since the earliest endeavors in resuscitation. The use of tobacco smoke enemas to resuscitate drowning victims on the banks of the Thames was documented as far back as 17461. Such efforts while anatomically misplaced, were in principle well intended. Although, we have since discovered alternative preferred orifices through which to ventilate our victims of cardiac arrest, the exact conduit to deliver these artificial breaths is still unclear.
There is a growing body of evidence suggesting a strategy that deemphasizing early definitive airway management may lead to improved outcomes. The majority of this data was observational and prone to the biases associated with such analyses2. With the publication of two major trials in JAMA, we now have high quality data examining the the role of a definitive airway in the management of patients with OHCA.
The first of these studies, the Pragmatic Airway Resuscitation Trial (PART), was a multicenter cluster-crossover randomized trial3. Wang et al randomized 27 EMS agencies across the US to one of two initial advanced airway strategies, laryngeal tube (LT) or endotracheal tube (ETI) insertion. The trial protocol did not limit the number of attempts permitted by paramedics, nor did they dictate the rescue strategies used in the case of a failed airway. The participating EMS personnel followed local protocol for confirmation of airway placement and management of OHCA, including field termination of resuscitation efforts.
Over a two-year period, 3004 patients were enrolled, 1505 assigned to LT group and 1499 to ETI group. Compliance with the intended treatment strategy (defined as the initial attempt with assigned airway or use of BVM only) was high in both groups, 95.5% and 90.7%, respectively. Success of the initial strategy utilized was significantly higher in the LT group at 90.3% compared to only 51.6% in the ETI group. The authors reported a statistically significant difference in their primary outcome, survival at 72-hours, 18.3% in the LT group vs 15.4% in the ETI group. This survival benefit in favor the LT group remained consistent when the authors examined survival to hospital discharge (10.8% vs 8.1%), and survival with a good neurological outcome, defined as an mRS of 0-3, (7.1% vs 5.0%). The authors also reported higher rates of airway insertion attempts (18.9% vs 4.5%), unsuccessful initial airway insertions (44.1% vs 11.8%), unrecognized airway misplacement or dislodgement (1.8% vs 0.7%), pneumothoraces (7.0% vs 3.5%) and rib fractures (7.0% vs 3.3%) in the ETI group compared to the LT group. These outcomes remained consistent when the authors examined subgroups based on initial rhythm, and whether the event was witnessed.
For those of us who have advocated for a supraglottic approach to airway management in cardiac arrest, these results seem to vindicate our assertions. The lower rates of neurologically intact survival may very well represent the logistical burdens associated with definitive airway management in patients in cardiac arrest. But as with any study these small differences are also likely to represent statistical noise, and a larger sample size may very well demonstrate a regression to the true mean.
It seems that the results of PART represent the later, as demonstrated by the AIRWAY-2 trial published alongside PART in JAMA4. Benger et al, conducted a multicenter, cluster RCT that randomized pre-hospital providers at 4 large EMS agencies to a second-generation supraglottic airway device or endotracheal intubation using direct laryngoscopy.
Over a two-year period, a much larger cohort of 9296 patients experiencing OHCA was enrolled. The authors found no difference in their primary outcome, survival with a good neurological outcome (mRS 0-3), 6.4% in the supraglottic group vs 6.8% in the tracheal intubation group.
In the subset of patients who received advanced airway management (80% of the entire cohort), more patients in the supraglottic airway device group had a favorable outcome, 3.9%, compared to only 2.6% in the endotracheal group. They also noted a supraglottic airway device treatment strategy was significantly more successful in achieving ventilation after up to 2 attempts (87.4% vs 79.0%), without noting any difference in regurgitation or aspiration.
Some would argue that the results of these trials compare a strategy which utilizes a supraglottic device to a strategy that employs subpar use of an endotracheal tube. After all, the first pass success rate reported by the authors in the PART trial was only 51.6%. This imperfection itself may be responsible for the inferior outcomes observed in this cohort. And while this is a valid criticism, the assumption that this failure in airway management was due to a poorly trained group of prehospital providers is unjust. The results may simply be due to the acuity of the patients and environment in which these providers find themselves operating. But let’s say for arguments sake this was due to a lack of training and could be solved by intense remediation. To what end? The AIRWAY-2 trial reported a higher rate of initial ventilation success, demonstrating at best ETT was no better than a supraglottic approach. It is a zero sum game. One could invest in intensive mandatory airway training and video laryngoscopy devices on every ambulance throughout your system to drive up the first pass success rate closer. And yet survival would remain unchanged, diverting logistical and financial resources away from the things that actually matter.
These are two well done large cluster-randomized trials examining broad swaths of the population. And while a substantial portion of the population did not ultimately receive the intended management strategy, the pragmatic design of these trials represent the realities of the prehospital environment. These trials examine the logistical complexities and subsequent consequences of an intended airway strategy. And while statistically incongruent, they likely represent the same underlying truth. In the large portion of patients experiencing OHCA, the management of the airway is of minimal clinical consequence. For the most part it is an unnecessary distraction, and the most logistically simple management strategy should be undertaken. In most cases this is a supraglottic airway. The question this data has left unanswered, how does a supraglottic strategy compare to more minimalistic approaches such as a simple nasal cannula and a jaw thrust? Or even the insufflation of more noxious fumes, like tobacco smoke perchance…