The effect of body temperature on the accuracy of arterial and end-tidal carbon dioxide measurement

Measurement of carbon dioxide has great clinical significance during mechanical ventilation, in the adjustment of ventilatory parameters and detection of respiratory complications. The main objective is to investigate the correlation between end-tidal carbon dioxide pressure (PetCO₂) and partial pressure of arterial carbon dioxide (PaCO₂) measured at 37 °C and corrected for body temperature in patients with thermal instability. Altogether, 110 measurements were analyzed, and the correlation was statistically more significant for corrected temperature than measured PaCO₂. The difference between corrected and uncorrected PaCO₂ varies from 3% per °C for hypothermic patients and 6.5% per °C for hiperthermic patients. The difference between PaCO₂ measured and PetCO₂ (Pa-etCO₂) resulted in an increase for all temperature degree, reaching a maximum difference of 9 torr. In contrast, Pa-etCO₂ has little variation when corrected PaCO₂ was used for calculation around −2.1 to 3.1 torr for hypo and hiperthermic patients. Thus, PetCO₂ reflects temperature corrected PaCO₂ more adequately than measured PaCO₂.