By Christopher T. Boyer
The American Heart Association 2015 guidelines for CPR and Emergency Cardiac Care are somewhat inconclusive about advanced airway management for patients in cardiac arrest. The guidelines stipulate that “there is no high-quality evidence favoring the use of endotracheal intubation compared with bag-mask ventilation or an advanced airway device in relation to overall survival or favorable neurologic outcome [1].”
The available research studies are often skewed due to a perceived selection bias. The AHA guidelines recommend either a BVM or an advanced airway for oxygenation and ventilation during CPR, which is a change from the 2010 guidelines that urged for ventilation via a BVM unless the BVM was not considered effective.
What, then, does the data say about intubating out-of-hospital cardiac arrest patients? Three research studies attempted to answer this question. Reviewing those articles will help understand how the AHA arrived at its recommendation for advanced airway management.
Association with neurological outcome?
The first article, “Association of Prehospital Advanced Airway Management with Neurologic Outcome and Survival in Patients with Out-Of-Hospital Cardiac Arrest,” was published in 2013 [2]. The study objective was to test a hypothesis that the intubation of cardiac arrest patients in the prehospital setting is associated with a favorable neurological outcome. The outcome the authors attempted to investigate is an important one, for while we often focus on obtaining ROSC on scene survival to hospital discharge neurologically intact should be our primary goal.
This study enrolled 281,522 patients in the advanced airway management only group, of which 41,972 received an endotracheal tube and 239,550 received a supraglottic airway and 367,837 patients in the BVM only group. While the authors do discuss the incidence of cardiac arrest in the United States at the beginning of the article, it is important to note this data was gathered retrospectively from a database in Japan. The EMS system described by the authors is vastly different from the U.S. EMS system. Advanced airway management requires an optional 62-hour training session that emergency lifesaving technicians began to participate in 2004. The training culminates with 30 required intubations in the OR under the guidance of an anesthesiologist. Most U.S. paramedic programs require just five OR patient intubations.
The statistical analysis of the data gathered in this study found that CPR with advanced airway management was a significant predictor of poor neurological outcome. This outcome is not easily generalizable for it is focused on data (and providers) in Japan. The authors of this study note several limitations, including patients that were not successfully intubated and thus managed with a BVM being grouped with the BVM only patients.
Impact on OHCA survival?
The second article, “Assessing the Impact of Prehospital Intubation on Survival in Out-Of-Hospital Cardiac Arrest,” was published in Prehospital Emergency Care in 2011, but the data gathered was from Jan. 1, 1995, to Dec. 31, 2006, which pre-dates the 2005 AHA guidelines that recommend a focus on CPR [3]. The data for this study was drawn from an analysis of patients who were transported to a single urban U.S. trauma center, with only adult patients who suffered a non-traumatic arrest included.
Of the 1,515 patients included in this study 183 did not receive an endotracheal tube in the field. The study concludes that being intubated in a VF/VT cardiac arrest results in a decrease in admission to the hospital as well as a decrease in survival to discharge while an increase in hospital admission was noted in a non-VF/VT arrest with no difference in survival to discharge.
The authors note several important limitations to this study. While the authors differentiated between patients who received prehospital intubation and those that did not, the reason why patients did not receive intubation was not included in the analysis. This could potentially skew the data since patients who were resuscitated prior to an intubation attempt even being required (such as ROSC following a single defibrillation) were placed in the same grouping as patient who required extensive resuscitation efforts. The authors also do not know at what point during the arrest the patients were intubated and how the endotracheal tube was confirmed and monitored throughout the call. The results of this study are also not easily generalized as it only covers patients transported to a single urban U.S. trauma center.
Survival to discharge?
“Assessing the Impact of Prehospital Intubation on Survival in Out-of-Hospital Cardiac Arrest,” the third article, was published in the Academic Emergency Medicine journal in 2010. The study investigated the intubation of out-of-hospital cardiac arrest patients and survival to hospital discharge [4]. This study was a retrospective analysis, with the data gathered from a single EMS system in North Carolina.
Researchers enrolled 1,142 cardiac arrest patients, with 203 patients receiving no intubation attempt with the remaining receiving at least one intubation attempt. The authors of this study, like the previous studies, found a significant increase in the likelihood to survive to hospital discharge with no intubation attempts. Like the previously mentioned studies this study is also limited by the percentage of participants who did not receive at least one intubation attempt.
The three studies seem to conclude that the intubation of the prehospital cardiac arrest patient is associated with negative outcomes. Each article is cited in the 2015 AHA guidelines. The studies also have a number of shared limitations, resulting in the guidelines allowing for airway management by either advanced management or BVM.
None of these studies included patients who received no ventilation and thus do not control for the increase in intrathoracic pressure that is caused by BVM ventilations. We therefore cannot conclude if factors surrounding intubation, such as interruptions in chest compressions, are causing these patients to have non-favorable outcomes, if the intubation procedure itself is causing the outcomes noted, or if it is actually the effect of positive pressure ventilation. Future research is needed to answer these important questions.
About the author
Chris Boyer, NRP, FP-C., M.P.A. is a lead paramedic instructor at Delaware Technical Community College. He has been involved in EMS since 1999, and has worked in the prehospital and air medical environments. He is a 2003 graduate of the Pennsylvania College of Technology’s Paramedic Program and is currently pursuing the Doctor of Business Administration degree at Wilmington University.
References
- Link, Mark S., Lauren C. Berkow, Peter J. Kudenchuk, Henry R. Halperin, Erik P. Hess, Vivek K. Moitra, Robert W. Neumar, Brian J. O’Neil, James H. Paxton, Scott M. Silvers, Roger D. White, Demetris Yannopoulos, and Michael W. Donnino. “Part 7: Adult Advanced Cardiovascular Life Support 2015. American Heart Association Guidelines Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care.” Circulation, 2015, S446-47. Accessed December 10, 2015.
- Hasegawa, Kohei, Atsushi Hiraide, Yuchiao Chang, and David F. M. Brown. “Association of Prehospital Advanced Airway Management With Neurologic Outcome and Survival in Patients With Out-of-Hospital Cardiac Arrest.” JAMA, 2013, 257.
- Egly, Joshua, Don Custodio, Nathan Bishop, Michael Prescott, Victoria Lucia, Raymond E. Jackson, and Robert A. Swor. “Assessing the Impact of Prehospital Intubation on Survival in Out-of-Hospital Cardiac Arrest.” Prehospital Emergency Care Prehosp Emerg Care, 2011, 44-49.
- Egly, Joshua, Don Custodio, Nathan Bishop, Michael Prescott, Victoria Lucia, Raymond E. Jackson, and Robert A. Swor. “Assessing the Impact of Prehospital Intubation on Survival in Out-of-Hospital Cardiac Arrest.” Prehospital Emergency Care Prehosp Emerg Care, 2011, 44-49.