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Arch Hellen Med, 34(5), September-October 2017, 605-614


The role of carbon dioxide during cardiopulmonary resuscitation

G.G. Tsaousi
Department of Anesthesiology and Intensive Care Unit, Faculty of Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece

High quality cardiopulmonary resuscitation (CPR) is one of the most significant factors defining outcome after a cardiac arrest, with an abundance of evidence indicating that it is a pre-requisite for improving the survival rates. Despite the fact that the importance of monitoring the changes in carbon dioxide throughout a complete respiratory cycle (capnography) as a prognostic indicator of CPR success was underlined several decades ago, only recently has the use of capnographs been incorporated in advanced CPR. End-tidal carbon dioxide (EtCO2) levels have been identified as the most powerful clinical indicator of CPR success, as EtCO2 correlates strongly with cardiac output, myocardial blood flow, aortic diastolic pressure, coronary perfusion pressure, cardiac index, and cerebral perfusion pressure. Waveform capnography enables continuous real time end-tidal CO2 to be monitored during CPR. During CPR, low EtCO2 levels mirror the poor cardiac output state achieved by chest compressions. Higher-quality chest compressions lead to an increased EtCO2 value. An abrupt increase in EtCO2 provides the fastest indication of return of spontaneous circulation (ROSC) as enhanced pulmonary perfusion enables a higher amount of CO2 to be transported to the lungs and be eliminated by alveolar ventilation. The role of waveform capnography during CPR includes ensuring tracheal tube placement in the trachea, monitoring the quality of chest compressions, identifying ROSC during CPR and outcome prognostication of CPR. It should be noted, however, that many potential confounding factors may affect the levels of EtCO2 during cardiac arrest, such as the cause of the arrest, the initial heart rhythm, the early onset of CPR, the fatigue of the rescuer and the administration of drugs. Undoubtedly, the use of capnography during pre-hospital and in-hospital CPR can be expected to be established as a standard practice, in the near future.

Key words: Capnography, Capnometry, Cardiac arrest, Cardiopulmonary resuscitation (CPR), End-tidal carbon dioxide, Return of spontaneous circulation (ROSC).

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