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If one were so inclined to start a war either on a social media page or in an EMS day room, they would simply have to reignite the debate of endotracheal intubation (ETI) versus supraglottic airway (SGA) placement during cardiac arrest. The rounds that are traded back and forth in these engagements ranges from “outcomes are better with….” or “it is so much easier to use…” Each with their own demonstrable benefit and each with their own limitations.1-3
But, and this is a big but, these arguments are often rooted in the belief that prehospital arrests are either traumatic or medical in origin, and that those that are medical in nature are the result of an arrhythmic sudden cardiac arrest. But this is not always the case. The “medical arrest” category can be further sub-divided into two more categories: arrhythmic sudden cardiac arrest and asphyxial cardiac arrest.4
In keeping with the CAB (circulation, airway, breathing) vernacular of cardiac arrest management, prehospital teams can be presented with those patients who have a primary “C” problem, such as a shockable rhythm; and those who have a primary “A” problem necessitating an aggressive airway management approach.
‘C’ Problems – Arrhythmic Sudden Cardiac Arrest
ACLS, and many courses like it, teach us algorithms that directly address the arrythmia or electrolyte abnormality that has led to a shockable (VF/VT) or non-shockable (PEA, asystole) rhythm. (Note: I acknowledge that this is an oversimplification of ACLS). It focuses on the heart and restoring normal electrical activity and perfusion. In the world of ABC’s (or CAB as it is known now), that is a “C” problem.
Medications, compressions, and defibrillations are what is needed to restore the cardiovascular system. In this context, the ETI vs. SGA debate is really a dead-end debate. There is no clear winner or loser. Some studies have shown that ETI over SGA matters and that there are better outcomes, while others have found it difficult to replicate those same outcomes.
Perhaps what the data says is that in the setting of an arrhythmic sudden cardiac arrest, the airway choice exerts little influence over the outcome if the compressions and defibrillations (as long as it does not interrupt or delay those compressions and defibrillations) work well enough to restore spontaneous circulation…quickly.
‘A’ Problems – Loss of Airway Patency and Asphyxiation
Sometimes the arrest is secondary to an “A” problem. Some data indicate that 20%-40% of out-of-hospital cardiac arrests (OHCA) are not of a primary cardiac origin.4 Typically, a sudden cardiac arrest is exactly like it sounds… sudden. For example, a person suffers from what appears to be a syncopal episode while standing in line at a coffee shop. They are found to be pulseless and apneic, so CPR is performed to keep blood circulating to the brain. EMS crews arrive and find the patient in V-fib and things move along from there.
With an asphyxial cause of cardiac arrest, the onset can be quite prolonged. Consider the end stage COPD patient who suffers a cardiac arrest secondary to hypoxic/hypercapnic respiratory failure. It takes time for hypoxia and hypercapnia to exert their influence on the patient’s cardiovascular system to the degree that the heart eventually stops.4 The arrest is not usually sudden but typically a gradual progression of brady-arrhythmias to PEA to asystole as hypoxia and acidosis negatively affect the cardiac conduction system and pacemakers.4 This is contrast to arrhythmic sudden cardiac arrest in which there is immediate cessation of forward blood flow.4
Sometimes the concept of asphyxiation is mis-conceptualized to thinking that it it only involves a person being physically choked or suffocated to death, which is still correct, but it only accounts for a portion of asphyxial arrests. There are other mechanisms of asphyxial arrest, such as; alveolar hypoventilation secondary to pulmonary disease, airway obstructions, neuromuscular disease, and hypoxic respiratory failure.4
It does warrant mentioning direct airway trauma such as hangings, penetrating trauma, and tracheal fractures which result in the air passage to the lungs no longer being patent. The patient asphyxiates and goes into cardiac arrest as a result. These injuries require an advanced airway placed in order to restore airway patency.
Successful reliance on an SGA in this case is predicated on the notion that the airway passages distal to the tube are intact and can support ventilation without the extravasation of air into the subcutaneous or thoracic spaces. In this context, the airway passages have been damaged and no longer offer a pathway for oxygen to reach the lungs for gas exchange to occur.
In an arrest caused by asphyxiation, it makes sense to replace what was lost… the airway and ventilation (to quote Dr. Mark Piehl). The state of the evidence being what it is makes it difficult to take a this or that position… until we consider what that patient’s likely clinical course will be.
The Next Echelon of Care
The “definitive” airway management method seems like a nebulous topic with cryptic unconvincing answers. But what if we considered these interventions as part of a broader resuscitation strategy? Does the solution become a little clearer? Instead of ETI or SGA being THE thing that does or does not improve outcomes, what if they were evaluated on their influence at the next level of care or advanced therapy?
When compared to standard ACLS, ECMO CPR (or eCPR) has demonstrated a survival benefit.5-6 The ARREST trial was even stopped early because of the significant survival benefit for those in refractory shock.6 What does this have to do with ETI vs. SGA in cardiac arrest management?
Certain parameters must be met for candidacy for ECMO. Simply arriving at an ECMO center does not mean that the therapy is indicated and appropriate for that patient. In the ARREST trial, if the patient’s EtCO2 was <10mmHg; PaO2 < 50mmHg; or oxygen saturation (arterial blood gas sampled) was <85% then they were excluded from the intervention and all resuscitative measures were discontinued.6 Of course, these criteria can be complicated or confounded in the presence of an unfavorable hemodynamic situation. As is often the case in the post arrest or intra-arrest situation.
Bartos et al showed that ETI was significantly associated with favorable blood gas results. In this trial the average PaO2 was 71mmHG in the ETI group versus 58mmHG in the SGA group; PaCO2 was lower at 55mmHg; and the pH was higher in the ETI group at 7.03 vs. 6.93 in the SGA group.5
Notably, 94% of the patients that were not eligible were deemed so due to their PaO2 being <50mmHg.5 Strengthening the argument for intubation versus SGA… if the intent is to transport to an ECMO center for cannulation. In this study, patients who were intubated were more likely to be eligible for ECMO and thus the increased chance of survival that accompanies that therapy.5
Even if they are cannulated for ECMO, their clinical course is far from over and uncomplicated. But now there is time to identify the underlying cause of the arrest; potentially reverse it; and allow for the body to heal from the ordeal.
Conclusion
This piece is not about a “this or that” approach to airway management in cardiac arrest. Instead, the aim is to break that type of thinking and decide, based on the physiologic problem presented to the clinician, which is the most effective intervention to perform to promote the best possible outcome.
Further, it is important to distinguish cardiac arrest secondary to asphyxial causes from those that are sudden arrhythmic cardiac arrests. Although not spelled out in the algorithms, the approach to their management is distinctly different and warrants a deeper thought process in order to get to the heart of the matter (see what I did there).
More from the Author
References
1. Kill C, Manegold RK, Fistera D, Risse J. Airway management and ventilation techniques in resuscitation during advanced life support: an update. J Anesth Analg Crit Care. 2024 Aug 24;4(1):58. doi: 10.1186/s44158-024-00195-x. PMID: 39182146; PMCID: PMC11344389.
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 Aug 28;320(8):779-791. doi: 10.1001/jama.2018.11597. PMID: 30167701; PMCID: PMC6142999.
3. Andersen LW, Granfeldt A, Callaway CW, et al; American Heart Association’s Get With The Guidelines–Resuscitation Investigators. Association Between Tracheal Intubation During Adult In-Hospital Cardiac Arrest and Survival. JAMA. 2017 Feb 7;317(5):494-506. doi: 10.1001/jama.2016.20165. PMID: 28118660; PMCID: PMC6056890.
4. Varvarousis, D., Varvarousi, G., Iacovidou, N., et al (2015). The pathophysiologies of asphyxial vs dysrhythmic cardiac arrest: implications for resuscitation and post-event management. The American Journal of Emergency Medicine, 33(9), 1297–1304. https://doi.org/10.1016/j.ajem.2015.06.066
5. Bartos JA, Clare Agdamag A, Kalra R,et al. Supraglottic airway devices are associated with asphyxial physiology after prolonged CPR in patients with refractory Out-of-Hospital cardiac arrest presenting for extracorporeal cardiopulmonary resuscitation. Resuscitation. 2023 May;186:109769. doi: 10.1016/j.resuscitation.2023.109769. Epub 2023 Mar 17. PMID: 36933882.
6. Yannopoulos D, Bartos J, Raveendran G, et al. Advanced reperfusion strategies for patients with out-of-hospital cardiac arrest and refractory ventricular fibrillation (ARREST): a phase 2, single centre, open-label, randomised controlled trial. Lancet. 2020 Dec 5;396(10265):1807-1816. doi: 10.1016/S0140-6736(20)32338-2. Epub 2020 Nov 13. PMID: 33197396; PMCID: PMC7856571.
Cody Winniford is a flight paramedic and base manager in Baltimore, MD. He has a passion for sharing his professional experience in EMS and management. Cody’s clinical and leadership development background spans both military and civilian settings and has served in several capacities as a leader and prehospital clinician. He specializes in air medical and critical care transport, as well as organizational development and leadership development. He is an active speaker on various leadership and clinical topics and is an established and successful educator for prehospital clinicians of all levels. He has a passion for human performance improvement and the mental health and performance aspects of prehospital care.
