Arterial to end tidal carbon dioxide difference during general anesthesia for neurosurgical procedures: a prospective observational study

ETCo2 measures partial pressure of carbon dioxide at the end of expiration with the help of non-invasive capnography.PaCo2 is defined as the partial pressure of arterial Co2 and measured by using a blood gas analyzer. In all neurosurgical procedures, anesthetist need to continuously monitor PaCo2 which is both invasive and cumbersome. Hence it was proposed whether ETCo2 measurement could be a reliable alternative instead of PaCo2 during general anesthesia and prospective observational study was done in 62 patients in our institution. The results showed there was correlation between ETCo2 and PaCo2 with P(a-ET) Co2 to be between 2-6 but the difference was more pronounced in surgery lasting for more than 2 hours.