Elsevier

Resuscitation

Volume 93, August 2015, Pages 124-127
Resuscitation

Commentary and concepts
Mechanisms linking advanced airway management and cardiac arrest outcomes

https://doi.org/10.1016/j.resuscitation.2015.06.005Get rights and content

Abstract

Advanced airway management – such as endotracheal intubation (ETI) or supraglottic airway (SGA) insertion – is one of the most prominent interventions in out-of-hospital cardiac arrest (OHCA) resuscitation. While randomized controlled trials are currently in progress to identify the best advanced airway technique in OHCA, the mechanisms by which airway management may influence OHCA outcomes remain unknown. We provide a conceptual model describing potential mechanisms linking advanced airway management with OHCA outcomes.

Introduction

Advanced airway management – such as endotracheal intubation (ETI) or supraglottic airway (SGA) insertion – is one of the most prominent interventions in out-of-hospital cardiac arrest (OHCA) resuscitation. In the United States, paramedics have performed ETI in OHCA for over 30 years [1]. However, many studies highlight the pitfalls of ETI, including unrecognized misplacement and dislodgement, multiple or failed ETI attempts, and impairment of cardiopulmonary resuscitation (CPR) chest compression continuity [2], [3].

To help expedite advanced airway management, minimize chest compression interruptions, and improve outcomes, many prehospital practitioners substitute ETI with SGA insertion, which generally involves simpler techniques. Ironically, observational studies suggest that OHCA outcomes may be worse with SGA than ETI [21]. Other studies suggest that a bag-valve mask (BVM) alone may be associated with better OHCA outcomes than either ETI or SGA [4]. Randomized controlled trials are currently in progress to better clarify the influence of advanced airway technique on OHCA outcomes. Yet, a critical question remains unanswered: what are the underlying mechanisms by which advanced airway management influences outcomes? The answer to this question could help us to better understand the results of past and future research and to identify potential solutions.

In this concepts paper, we describe potential mechanisms linking advanced airway management with OHCA outcomes.

Section snippets

Benefits of advanced airway management

Cardiopulmonary arrest involves sudden ischemia to all organ systems, including the heart and brain. Delivery of oxygen to these organs is vital to (1) restore normal cardiac function, and (2) preserve organ function until spontaneous circulation is achieved. Preservation of organ function likely involves optimization of cellular metabolism by decreasing hypercapnia, normalizing intracellular pH, and reducing damage from ongoing cellular hypoxia [5]. In this context, advanced airway management

Potential harmful mechanisms of advanced airway management

We propose that advanced airway management may encompass (1) technical errors, (2) cognitive errors, and (3) adverse anatomic effects. These errors or events may individually or synergistically cause harm in OHCA by causing (1) loss of chest compression control, (2) loss of ventilation and oxygenation control, or (3) loss of normal anatomy (Fig. 2):

Timing of resuscitation interventions

An additional consideration is the timing and sequence of advanced airway interventions. Airway interventions represent only a fraction of numerous time-dependent interventions necessary during OHCA resuscitation, including delivery of chest compressions, defibrillation, obtaining intravenous or intraosseous access, and administering antiarrhythmic and vasoactive medications. An interaction may exist between the relative timing of advanced airway management and other interventions that could

Scientific and clinical implications

This conceptual model has important scientific and clinical implications. Our current understanding of the connection between advanced airway management and OHCA outcomes is based upon observational data, which have inherent limitations because the fundamental study design does not control for confounding variables. Even after statistical adjustment, the potential for unknown and unmeasured confounders remains. Investigators in the United Kingdom and United States are currently planning large

Conclusions

We provide a conceptual model identifying potential mechanisms linking advanced airway management with OHCA outcomes. Prospective study is required to evaluate and validate these postulated mechanisms. Scientists and clinicians must strive to understand these processes to best guide scientific research and clinical care.

Funding

Benoit: RF2015-001 from the Society for Academic Emergency Medicine Foundation (SAEMF). Prince: UH2-HL125163 from the National Heart, Lung and Blood Institute (NHLBI). Wang: UH2-HL125163 from the National Heart, Lung and Blood Institute (NHLBI).

Conflict of interest statement

The authors have no conflict of interest to disclose.

References (21)

There are more references available in the full text version of this article.

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    Cardiopulmonary resuscitation (CPR) has been the cornerstone of treatment for out-of-hospital cardiac arrest (OHCA) since first described in the 1950s.1 Optimal ventilation during CPR facilitates gas exchange in the lungs, which improves cellular metabolism by decreasing hypercapnia, normalizing intracellular pH, and reducing cellular hypoxia.2 However, ventilation may also cause harm, as respiratory alkalosis causes cerebral vasoconstriction, and increased intrathoracic pressure reduces coronary and cerebral perfusion by decreasing venous return.3–7

  • Duration of exposure to a prehospital advanced airway and neurological outcome for out-of-hospital cardiac arrest: A retrospective cohort study

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    However, the prehospital setting is a tumultuous environment where airway patency, oxygenation, and ventilation are frequently managed manually. As such, potential harms exist including hyperventilation leading to increased intrathoracic pressure and subsequent decreased coronary and cerebral perfusion pressure, unrecognized dislodgment of the advanced airway leading to hypoventilation and hypoxia, and injury to soft tissue structures.6,9,15–18 In the United States, EMS advanced airways are frequently managed without mechanical ventilators, so the more time EMS spends in the prehospital environment, the more the patient may be exposed to these potential harms, which may increase the chance of unintentional secondary injury.

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A Spanish translated version of the abstract of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2015.06.005.

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