JAMA recently published two randomized control trial airway studies comparing endotracheal intubation (ETI) with either a laryngeal tube (LT) or supraglottic airway (SGA) device intubation during out of hospital cardiac arrest (OHCA). While each study came to a slightly different conclusion, both provide fodder for the ongoing debate around advanced airway management during a cardiac arrest in the prehospital setting.
Summary of the PART Trial
The first study, the PART Trial, was conducted from December 2015 to November 2017 by sites across North America in the Resuscitation Outcomes Consortium. It was a multicenter cluster-crossover randomized trial, meaning that entire sites were randomized to either ETI or LT for 3-5 month blocks and then switched to the alternative airway management type at least once during the study period.
The primary outcome was survival to 72 hours, a unique primary outcome that was chosen based on the demands of the trial’s funding source. Secondary outcomes included ROSC, survival to hospital discharge, and favorable neurological status at discharge. The trial was powered to detect a 4.5 percent survival difference in the study arms at 72 hours, resulting in a targeted sample size of 3,000 patients.
A total of 3,004 patients were included in the final analysis, 1,505 assigned to the LT group, 1,499 to the ETI group. Time from EMS arrival to airway start was faster for the LT group by almost 3 minutes and the first pass success rate with an LT was 90.4 percent vs. 51.6 percent for the ETI. Confirmation of tube placement was based solely on local protocols. Interestingly, patients in the ETI group were re-intubated at the receiving ED one-third of the time, while patients in the LT group were intubated upon ED arrival nearly two-thirds of the time.
Patients in the ETI group were more likely to:
- Receive three or more airway insertion attempts.
- Have an unrecognized airway misplacement or dislodgement.
- Suffer a pneumothorax or rib fractures.
The primary outcome, 72-hour survival, was 18.3 percent in the LT group, and 15.4 percent in the ETI group, a statistically significant difference. Patients in the LT group were also more likely to achieve ROSC, survive to hospital discharge, and be neurologically intact upon discharge.
Summary of the AIRWAYS-2 Trial
The second study, the AIRWAYS-2 Trial, was conducted from June 2015 to August 2017 within four agencies across England. This study was a clustered randomized control trial; however, the randomization was done at the provider level rather than the organization level and the airway management devices were either ETI using direct laryngoscopy or an SGA device.
Paramedics received additional training in their airway management device after randomization and did not cross over to a different study arm during the study period. The ETI group was encouraged to use bougies on all attempts and EtCO2 was used on all patients to confirm device placement.
The primary outcome was neurological status at hospital discharge or 30 days, whichever occurred first. The secondary outcomes focused on process measures relating to airway management as well as ROSC, chest compression fraction in a small subsample, and time to death.
The trial was powered to detect a 2 percent difference in the primary outcome, resulting in a targeted sample size of over 9,000 patients. A total of 4,410 patients were included in the ETI group, while 4,886 were in the SGA group.
The SGA group was more likely to achieve ventilations within two attempts (87.4 percent vs. 79.0 percent) as well as lose a previously established airway. Patients with an SGA also had ROSC more often than their ETI counterparts. No difference in chest compression fraction was found between groups in the small subsample.
Neurologically intact at hospital discharge, was 6.4 percent in the SGA group, and 6.8 percent in the ETI group, a non-statistically significant difference.
Memorable quotes from the PART Trial
- “Numerous studies have highlighted the challenges of paramedic ETI, including significant rates of unrecognized tube misplacement or dislodgement, the need for multiple ETI attempts and ETI insertion failure.”
- “Clinicians at receiving emergency departments converted 64.4 percent of EMS LT to ETI. Among patients receiving successful EMS ETI, emergency department clinicians performed repeat ETI in 33.1 percent.”
- “In this trial of 3,004 adults with OHCA, a strategy of initial LT was associated with modest but significantly greater 72-hour survival than a strategy of initial ETI.”
- “OHCA resuscitation requires the careful coordination of multiple interventions, including initiation and maintenance of chest compressions, controlled ventilation, vascular access, drug administration and defibrillation. The simpler LT technique may better integrate with and facilitate these other treatments.”
Memorable quotes from the AIRWAYS-2 Trial
- “Insertion of a supraglottic airway device is simpler and faster than tracheal intubation, and proficiency requires less training and ongoing practice.”
- “Patients with a short duration of cardiac arrest and who receive bystander resuscitation, defibrillation or both are considerably more likely to survive and are also less likely to require advanced airway management.”
- “This study found that 21.1 percent (360/1,704) of patients who did not receive advanced airway management achieved a good outcome compared with 3.3 percent (251/7,576) of patients who received advanced airway management.”
- “Among patients with out-of-hospital cardiac arrest, randomization to a strategy of advanced airway management with a supraglottic airway device compared with tracheal intubation did not result in a favorable functional outcome at 30 days.”
Key takeaways from PART and Airways-2 Trials
Here are the top three takeaways from the PART Trial and the Airways-2 Trial.
1. Basic study design differences matter
Both trials included non-traumatic OHCA patients over the age of 18. Both also followed a clustered randomization with the AIRWAYS-2 clustered at the provider level, while the PART trial clustered at the organization level and had organizations move back and forth multiple times during the study.
The provision of additional training on the part of the AIRWAYS-2 trial may have improved overall performance. Additionally, the decision to have organizations in the PART trial alternate between both interventions may have increased cognitive load and decreased muscle memory on the part of providers, and thereby potentially effected performance.
2. 72-hour survival does not equal 30 day neurologically intact survival
While survival at the 72-hour mark is necessary for neurologically intact survival at hospital discharge, the opposite is not true. This is particularly important in light of hospital-based interventions, such as targeted temperature management, in which patients may be in a drug-induced coma past the 72-hour mark.
3. Reported first pass success vs. realistic first pass success
Both studies reported a lower than previously published first pass success rate for ETI. Both suggested this was due to publication bias in which agencies that publish their results often do so after a successful intervention intended to increase first pass success.
This lower than published first pass success rate is likely reflective of the norms within the industry and shows just how much work is needed on improving performance of this potentially dangerous intervention.
Moving forward with airway management during OHCA
Some providers swear by their secret sauce for good airway management during a cardiac arrest. But the available evidence suggests there is no such construct. We know early identification, early defibrillation and uninterrupted chest compressions save lives. Everything else is lagniappe, except in some very unique circumstances.
This means focusing on consistency across the basics. The cognitive load during an OHCA is extremely high. Anything we can do to decrease that load is likely to increase performance and, thereby, survival. If we make things bulletproof at 3 a.m., we give patients the best chance possible.
Regardless of what type of tube, laryngoscope or other tools used to ventilate, all efforts should be made to ensure continuous chest compressions. Perhaps this even means not placing an advanced airway at all, but rather performing good bag-valve ventilations for the duration of the OHCA.
However, if an advanced airway device is to be used, it means creating an airway management protocol with limited opportunities for deviation that focuses on adequate pre-oxygenation, decreasing the number of intubation attempts, intubating during chest compressions, and using tools such as bougies and end tidal carbon dioxide to ensure success.
