In their report on 737 patients who sustained out-of-hospital cardiac arrest, collected over an interval of 9 years in a well-organized emergency medical system, Kolar and colleagues confirmed that the measurement of end-tidal carbon dioxide tension (PetCO₂) is predictive of the outcomes of cardiopulmonary resuscitation 1. The authors provide impressive data supporting the conclusion that, in their population, failure to increase PetCO₂ to levels exceeding 14 mmHg (1.5 kPa) after 20 minutes of attempted resuscitation served as a reliable guide for terminating unsuccessful cardiopulmonary resuscitation. The population studied, however, differed in some respects from the majority of earlier demographic reports that the authors cited with hospital survival <3%. More than 53% survived. The majority of instances of cardiac arrest reported by them was witnessed, and as many as one-third of victims received bystander cardiopulmonary resuscitation – favoring improved outcomes. Fatal outcomes, as anticipated, were associated with a doubling of the response time of professional rescuers, presumably in the absence of bystander utilization of automated external defibrillators, especially since a majority of survivors had shockable ventricular fibrillation or ventricular tachycardia.

As the authors pinpoint, PetCO₂ has evolved into a technically facile and singularly useful monitor to guide cardiopulmonary resuscitation. PetCO₂ provides an indirect measurement of the cardiac output generated by chest compression and thereby guides the effectiveness of the procedure, including chest compression, to achieve better outcomes. It also allows uninterrupted chest compression because it promptly signals the return of spontaneous circulation 2. PetCO₂ is likely to promptly identify asphyxia, in contrast to primary cardiac causes of arrest as previously reported by one of the present authors 3. PetCO₂ measurement during cardiopulmonary resuscitation may not require routine endotracheal intubation, which usually interrupts chest compression and under crisis conditions has a high failure rate and disproportionate airway injury. The alternatives of a laryngeal mask airway or even a facial mask incorporating a mainstream carbon dioxide sensor may be utilized. Because injection of bolus epinephrine produces a sharp although transient reduction in PetCO₂ when injected intravenously 4, clinicians would best be alerted to this potential error.

These considerations notwithstanding, Kolar and colleagues contribute an additional and important incentive for rescuers to utilize PetCO₂ as a routine monitor to guide management and decision-making during cardiopulmonary resuscitation.

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Competing interests