Ventilation strategies in cardiac arrest

Long-term survival for adult out-of-hospital cardiac arrest victims remains dismal and is typically less than 10%. Historically, many resuscitation guidelines have had little evidence to support their recommendations but research in this field has been burgeoning, with advanced life support guidelines undergoing substantial recent changes to reflect new findings. One of these changes has been to emphasize chest compression continuity at the earliest stages of resuscitation with a much reduced prominence being given to advanced airway interventions such as endotracheal intubation. Consequently, in Arizona, where the authors of this study are based, emergency medical teams now provide initial airway management with passive ventilation or standard bag-valve-mask ventilation.

In this retrospective analysis of 1019 patients with out of hospital arrest between 2005 and 2008 who had minimally interrupted chest compressions, the authors compare rates of neurologically intact survival between these two strategies. 459 individuals were found to have had passive ventilation with 560 having bag-valve-mask ventilation. Overall rates of neurologically intact survival are poor with either strategy with 10% and 9.5% respectively surviving to discharge, with no difference between groups. This falls to a particularly sobering 1.3 and 3.7% when a non-shockable rhythm was found, again with no difference between groups. However in the best case scenario, where a witnessed arrest was found to have VF or VT there did appear to be a difference between the two strategies with 38.2% surviving intact with the passive ventilation approach and 25.8% surviving with the bag-valve mask ventilation(OR 2.5 (95% CI 1.3-4.6)).

Conclusions:
This study suggests that, following cardiac arrest, even the minimal disruption provided by bag-valve mask ventilation may be detrimental to patients and should ideally be avoided. Prospective randomised trials, while undoubtedly difficult, will be needed to bring further clarity to this issue.

• Bobrow BJ, Ewy GA, Clark L, Chikani V, Berg RA, Sanders AB, Vadeboncoeur TF, Hilwig RW and Kern KB. Passive oxygen insufflation is superior to bag-valve-mask ventilation for witnessed ventricular fibrillation out-of-hospital cardiac arrest. Ann Emerg Med. 2009 Nov;54(5):656-662.

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