Engine 32 and Rescue 4 respond to a person not breathing at a youth sports complex. They arrive to see bystanders performing CPR and applying the facility’s automated external defibrillator (AED). While exiting the vehicle, paramedics hear the AED deliver a shock.
Because of the large crowd gathered around the patient, paramedics and EMTs quickly load the patient into the back of the ambulance. En route, one medic starts an IV line while the other attempts intubation.
The patient’s short neck and small mouth make the intubation effort very difficult. The medic attempts laryngoscopy three times, each time with a 45 second break in chest compressions as he attempts to visualize the vocal cords.
His partner steps in and inserts a laryngeal tube airway. Resuscitation is continued in the local ED for 30 minutes until the patient is declared dead. The two paramedics and the ED physician then debate the best airway management strategy for patients in cardiac arrest.
Out-of-hospital cardiac arrest (OHCA) is a major public health problem affecting more than 424,000 persons annually in the United States, with only 10.4% surviving to discharge from the hospital.1
Endotracheal intubation (ETI) is one of most common procedures performed by paramedics during cardiac resuscitation; however, several research studies have highlighted the pitfalls of prehospital ETI, including misplacement of ET tubes and multiple failed intubation attempts.2
Intubation attempts may also interfere with other key resuscitation tasks resulting in frequent and prolonged interruption in CPR.3
Because of these numerous factors, new strategies for OHCA airway management, including the use of supraglottic airway (SGA) devices have gained popularity. Some field providers and EMS medical directors believe that SGAs are easier to insert, and can be inserted without sacrificing the quality of chest compressions. However, prior observational studies comparing SGA vs. ETI in OHCA outcomes suggested similar or better overall survival with ETI than SGA.4—8
To date, there have been few randomized trials directly comparing ETI with other airway techniques in OHCA, and none comparing the King LT airway.9,10
Pragmatic Airway Resuscitation Trial (PART)
Twenty-seven EMS agencies from five metropolitan areas in the U.S. participated in a randomized clinical trial comparing the King Laryngeal Tube (King LT) airway vs. ETI in adult OHCA patients.11
The Pragmatic Airway Resuscitation Trial (PART) included adults with non-traumatic OHCA requiring ventilatory support or advanced airway management. The trial randomized patients to one of two initial advanced airway management strategies:
- Initial insertion of the King LT, or
- Initial insertion of an endotracheal tube. (See Figure 1.)
Although no other airway devices were allowed for the initial attempt, EMS personnel were allowed to perform “rescue” airway management using any available airway technique including King LT, ETI, bag-valve mask (BVM) and cricothyroidotomy.
EMS personnel followed their local protocols for confirmation of airway placement and management of OHCA including termination of resuscitation.
Each agency periodically switched from one airway as their first strategy to the other option based on a research method called cluster randomization. Each agency would use one airway as their primary airway for a fixed time period (approximately 3—6 months), and would then switch to the other treatment arm. This process helped to assure balance in the allocation of cases between the two treatments and account for different resuscitation rates across agencies.
The primary outcome was survival to 72-hours after the arrest. Secondary outcomes included: return of spontaneous circulation (ROSC), defined as pulses present on arrival at the hospital; survival to hospital discharge; and neurologically favorable survival to hospital discharge. We also identified key EMS airway management issues and hospital adverse events.
The trial began enrollment on Dec. 1, 2015, and completed enrollment on Nov. 4, 2017. A total of 3,004 subjects were enrolled, with 1,505 assigned to initial King LT and 1,499 assigned to initial ETI. Patient demographics and arrest characteristics were similar in both groups. (See Figure 2.)
Elapsed time from first EMS arrival to airway start was shorter for King LT than ETI (mean 11.0 mins. vs. 13.6 mins.). Initial airway success rate was 89.9% in the King LT group and 51.3% in the ETI group. Overall, the King LT and ETI airway success rates (initial plus rescue airway attempts) were 94.2% and 91.5%, respectively. The ETI group was more likely to require more than three insertion attempts (18.9% vs. 4.5%).
The main outcome of the study, 72-hour survival, was significantly higher for King LT than ETI (18.3% vs. 15.4%), a difference of 2.9%. Secondary outcomes were also better for King LT than ETI including: ROSC (27.9% vs. 24.3%), hospital survival (10.8% vs. 8.1%), and favorable neurological status at discharge (7.1% vs. 5.0%).
The ETI group had higher rates of multiple airway insertion attempts, unsuccessful airway insertion, and unrecognized airway misplacement or dislodgement. Other in-hospital adverse events were similar between treatment groups.
What It Means
In this trial of 3,004 adults, we found that a strategy of initial King LT resulted in better 72-hour survival than initial ETI. Initial King LT also had better outcomes including ROSC, survival to hospital discharge, and favorable neurologic status at hospital discharge. Although these differences seem small, they’re important.
If all EMS systems across the country were to shift to King LT as the primary advanced airway for OHCA patients and saw a similar 2.7% increase in hospital survival rate, more than 10,000 extra lives would be saved each year.
Why was the King LT better than ETI?
OHCA resuscitation requires the coordination of multiple interventions, including initiation and maintenance of uninterrupted chest compressions, ventilations, vascular access, drug administration and defibrillation.
The simpler King LT may be easier to insert during the resuscitation, allowing the paramedic to focus on other important treatments. In this study, we noted that the elapsed time from EMS arrival to first airway attempt was almost 2.5 minutes shorter in the King LT vs. ETI, and the King LT required fewer insertion attempts than ETI.
Unfortunately, due to limited funding, we couldn’t assess the effects of the airway device used and how it impacts CPR quality, in particular limiting the number and duration of chest compression interruptions.
What about the low intubation success rate?
An important observation was an intubation success rate of 51%, a figure much lower than that reported by many EMS agencies. We believe that this observation reflects current trends in EMS practice, as many systems are encouraging earlier use of SGAs to prevent chest compression interuptions.12
In this study, only a few EMS agencies had protocols limiting the number of intubation attempts, and therefore the low ETI success rate was not directly driven by the constraints of clinical protocols. Although the study contained a range of EMS agencies, it’s possible that agencies with providers more skilled at intubation may have achieved different results.
Why are these results different than prior studies?
There are important differences to highlight from our trial vs. prior studies of OHCA airway management. Although numerous observational studies including those from the Resuscitation Outcomes Consortium (ROC) and the Cardiac Arrest Registry to Enhance Survival (CARES) have reported higher survival with ETI than SGA insertion, these data were non-randomized and included a range of SGA types (e.g., Combitube, LMA, King LT).
In a trial of 830 children, no difference was found in survival or neurologic outcomes between patients randomized to BVM only vs. BVM+ETI, but the study included several different medical conditions–not just OHCA.13
A recent trial of 2,043 adult OHCA patients in France and Belgium found no survival differences between BVM and ETI, but unlike EMS systems in the U.S., the EMS units were staffed with physicians.10
Are there limitations with the study?
This study had several important limitations. The EMS agencies that participated in this trial have many years of experience in OHCA research, including additional training on CPR quality performance.
As previously noted, due to limitations in funding, we couldn’t assess the influence of CPR quality. We studied a relatively limited number of out-of-hospital and in-hospital adverse events. It also wasn’t possible to blind EMS providers to treatment assignment.
Although randomization was uneven in two sites, the overall characteristics of the study groups were similar. We observed a lower than expected ETI success rate; the potential for different outcomes with a higher ETI success rate remains a possibility.
Many EMS agencies have recently switched to an alternative SGA, the i-gel. A similar trial called “The Airways-2 Randomized Clinical Trial” in the United Kingdom compared i-gel with intubation in OHCA.9 Their findings suggest that there are no significant differences at hospital discharge or 30 days after arrest for all trial patients.15
The Bottom Line
PART found that initial airway management with the King LT was associated with significantly better clinical outcomes than initial ETI in adult OHCA. The authors recommend that EMS providers review the full results of the study, published in the Journal of the American Medical Assocation, with their medical director and strongly consider a strategy of initial King LT when treating adult OHCA.14
1. CARES. (2017). Cardiac arrest registry to enhance survival (CARES) website, 2017. Retrieved from www.scopus.com.
2. Silvestri S, Ladde JG, Brown JF, et al. Endotracheal tube placement confirmation: 100% sensitivity and specificity with sustained four-phase capnographic waveforms in a cadaveric experimental model. Resuscitation. 2017;115:192-198.
3. Wang HE, Simeone SJ, Weaver MD, et al. Interruptions in Cardiopulmonary Resuscitation From Paramedic Endotracheal Intubation. Ann Emerg Med. 2009;54(5):645-652.
4. Wang HE, Szydlo D, Stouffer JA, et al. Endotracheal intubation versus supraglottic airway insertion in out-of-hospital cardiac arrest. Resuscitation. 2012;83(9):1061-1066.
5. Hasegawa K, Hiraide A, Chang Y, et al. Association of prehospital advanced airway management with neurologic outcome and survival in patients with out-of-hospital cardiac arrest. JAMA. 2013;309(3):257-266.
6. Studnek JR, Thestrup L, Vandeventer S, et al. The association between prehospital endotracheal intubation attempts and survival to hospital discharge among out-of-hospital cardiac arrest patients. Acad Emerg Med. 2010;17(9):918-925.
7. Benoit JL, Gerecht RB, Steuerwald MT, et al. Endotracheal intubation versus supraglottic airway placement in out-of-hospital cardiac arrest: A meta-analysis. Resuscitation. 2015;93:20-26.
8. Kajino K, Iwami T, Kitamura et al. Comparison of supraglottic airway versus endotracheal intubation for the pre-hospital treatment of out-of-hospital cardiac arrest. Crit Care. 2011;15(5):R236.
9. Benger JR, Voss S, Coates D, et al. Randomised comparison of the effectiveness of the laryngeal mask airway supreme, i-gel and current practice in the initial air-way management of prehospital cardiac arrest (REVIVE-Airways): A feasibility study research protocol. BMJ Open. 2013:3(2):e002467.
10. Jabre P, Penaloza A, Pinero D, et al. Effect of Bag-Mask Ventilation vs Endotracheal Intubation During Cardiopulmonary Resuscitation on Neurological Outcome After Out-of-Hospital Cardiorespiratory Arrest: A Randomized Clinical Trial. JAMA. 2018;319(8):779-787.
11. Wang HE, Prince DK, Stephens SW, et al. Design and implementation of the Resuscitation Outcomes Consortium Pragmatic Airway Resuscitation Trial (PART). Resuscitation. 2016;101:57-64.
12. Crewdson K, Lockey DJ, Roislien J, et al. The success of pre-hospital tracheal intubation by different pre-hospital providers: a systematic literature review and meta-analysis. Crit Care. 2017;21(1):31.
13. Gausche M, Lewis RJ, Stratton SJ, et al. Effect of out-of-hospital pediatric endotracheal intubation on survival and neurological outcome: A controlled clinical trial. JAMA. 2000;283(6):783-790.
14. 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(8):769—778.
15. 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(8):779—791.