Out-of-hospital quantitative monitoring of end-tidal carbon dioxide pressure during CPR

Abstract

To assess the feasibility and potential usefulness of quantitative measurement of end-tidal carbon dioxide pressure (PETCO2) during out-of-hospital cardiac arrest. Emergency medical technician-paramedics (EMT-Ps) were instructed in the operation of a portable battery-powered capnograph, the sensor for which was attached to the endotracheal tube following intubation. This was a preliminary pilot study limited to defining feasibility and potential utility in a small group of patients. City with population of 70,745 served by an advanced life support emergency medical services system. Initial group of four patients who experienced out-of-hospital cardiac arrest and who were treated by EMT-Ps trained in operation of the capnograph. As soon as possible following endotracheal intubation a mainstream sensor was connected to the endotracheal tube and digital and capnographic waveform data obtained for the remainder of the resuscitation. Data were stored in memory and subsequently retrieved for the entire event, with digital readings at eight-second intervals. Capnographic measurements were obtained immediately after endotracheal intubation in all four patients. The capnograph was operated without difficulty throughout the resuscitations. Changes in performance of chest compression or changes in cardiac rhythm were reflected immediately in changes in (PETCO2). Persistent excretion of carbon dioxide during pulselessness was observed in two patients, consistent with "pseudo-electromechanical dissociation." These preliminary pilot observations confirm the feasibility of quantitative capnography during out-of-hospital cardiac arrest and indicate that early institution of this noninvasive procedure may provide insight into pathophysiologic mechanisms such as pseudo-electromechanical dissociation and may also track changes in pulmonary blood flow during chest compressions or during spontaneous circulation.