Comparison of Capnography and Blood Gas PaCO₂ Measurements

Capnography provides continuous, non-invasive assessment of ventilation by measuring end-tidal carbon dioxide (EtCO₂). Different capnographic technologies, including mainstream, sidestream, and microstream capnography, may produce different EtCO₂ measurements depending on their sampling and measurement techniques. This prospective, non-randomized observational study was designed to compare EtCO₂ values obtained using mainstream, sidestream, and microstream capnography with carbon dioxide partial pressure (PCO₂) values obtained from clinically indicated blood gas analysis in adult patients presenting to the emergency department. For each participant, EtCO₂ measurements were obtained using the three capnographic methods in close temporal proximity to blood gas sampling. The relationship and agreement between blood gas PCO₂ and EtCO₂ measurements were planned to be evaluated using correlation analyses and Bland-Altman analysis. Additional analyses were planned according to whether the blood gas sample was arterial or venous.