Capnography during cardiac resuscitation: a clue on mechanisms and a guide to interventions

Measurement of the end-tidal partial pressure of carbon dioxide (P(ET)CO(2)) during cardiac arrest has been shown to reflect the blood flow being generated by external means and to prognosticate outcome. In the present issue of Critical Care, Grmec and colleagues compared the initial and subsequent P(ET)CO(2 )in patients who had cardiac arrest precipitated by either asphyxia or ventricular arrhythmia. A much higher P(ET)CO(2 )was found immediately after intubation in instances of asphyxial arrest. Yet, after 1 min of closed-chest resuscitation, both groups had essentially the same P(ET)CO(2), with higher levels in patients who eventually regained spontaneous circulation. The Grmec and colleagues' study serves to remind us that capnography can be used during cardiac resuscitation to assess the mechanism of arrest and to help optimize the forward blood flow generated by external means.