Partial pressure of end‐tidal CO2sampled via an intranasal catheter as a substitute for partial pressure of arterial CO2in dogs

Abstract

AbstractObjective:To demonstrate correlation and clinical usefulness of the partial pressure of end‐tidal CO2(ETCO2) measurement by nasal catheter placement in sedated dogs with and without concurrent nasal oxygen administration as a substitute for partial pressure of arterial CO2(PaCO2).Design:Prospective, cross‐over trial.Setting:University of Saskatchewan veterinary research laboratory.Animals:Six cross‐breed dogs with a mean (±SD) weight of 29.1±4.03 kg.Interventions:All dogs were sedated with 5 μg/kg medetomidine intravenously (IV) and an arterial catheter was placed in a dorsal pedal artery for removal of blood for gas analysis. A nasal catheter was placed in the ventral meatus and connected to a capnometer for ETCO2measurements in all dogs. Dogs receiving supplemental nasal oxygen had a second nasal catheter placed in the contralateral naris.Measurements and main results:In the group without nasal oxygen supplementation, the ETCO2measurement underestimated (negative bias) the PaCO2by −2.20 mmHg with limits of agreement (95% confidence interval) of −5.79, 1.39 mmHg. In the group receiving oxygen supplementation, ETCO2measurement underestimated (negative bias) the PaCO2by −2.46 mmHg with limits of agreement (95% confidence interval) of −8.42, 3.50 mmHg.Conclusions:The results of this study demonstrate that ETCO2monitoring via a nasal catheter provides a clinically acceptable substitute to arterial blood gas analysis as a means of monitoring ventilation in healthy, sedated dogs. The limits of agreement were within acceptable limits with and without concurrent insufflation of oxygen.