Capnography: Principles and application in critical care medicine

Capnography has become an essential monitoring tool in perioperative and critical care setting. It helps monitor dynamic physiological processes more precisely and promptly, compared to other monitoring modalities. Methods to measure and display carbon dioxide concentrations in respired gases include infrared spectrography, mass spectrography, Raman spectrography, photoacoustic analysers or colorimetry. It is used to confirm correct endotracheal tube placement, ensure effective and consistent chest compression, detect return of spontaneous circulation and diagnose alterations in haemodynamics and ventilation of critically ill patient. It helps to optimise fluid resuscitation and monitor shock progression by providing insight into adequacy of tissue perfusion. Thus, a detailed study and interpretation of capnographic waveform is essential.