The Correlation Between End-Tidal Carbon Dioxide Measured By Capnoxygen (trademark) Mask and Nasal Cannula

The use of capnography during general anesthesia has become a standard of care for all anesthesia providers and is considered an essential monitoring devise. The relationship of end-tidal carbon dioxide ETCO2 to arterial carbon dioxide in intubated patients has been well established by Saunders, and colleagues 1994. Attention has focused on capnography in sedated, nonintubated patients where ETCO2 was not monitored and patients had associated comorbidities. Studies also have documented a correlation between the accuracy of ETCO2 to arterial carbon dioxide during spontaneous ventilation using a carbon dioxide CO2 sampling device through a prong in an oxygen O2 nasal cannula. In this study, a single-use medium concentration O2 face mask designed to deliver oxygen while monitoring ETCO2 in spontaneously breathing patients was used. The accuracy of the measured ETCO2 was compared to a standard nasal cannula sampling port in 13 normal healthy volunteers. There was a positive correlation between the ETCO2 of both devices with and without the addition of oxygen. Mean ETCO2 measurements with the mask decreased in proportion to increasing oxygen flows, while mean ETCO2 with the nasal cannula remained consistent. Sixty one percent of volunteers stated the mask was more comfortable to wear during their testing experience, and half stated they would prefer to wear the mask over the cannula for a procedure lasting more than one hour.