End-Tidal Carbon Dioxide and Outcome of Out-of-Hospital Cardiac Arrest

To the Editor: Levine and colleagues (July 31 issue)¹ claim that an end-tidal carbon dioxide level of 10 mm Hg or less, measured 20 minutes after the initiation of advanced cardiac life support, accurately predicted death in patients with cardiac arrest who had electrical activity but no pulse. Although not explicitly stated, it appears that all 35 survivors in their study had spontaneous circulation at the time of the measurement of end-tidal carbon dioxide (at 20 minutes) and, conversely, that none of the nonsurvivors had regained spontaneous circulation at this time. This point should be clarified, because if the distinction . . .