A comparison of carbon dioxide monitoring and oxygenation between facemaskand divided nasal cannula

The divided nasal cannula is a device recently released in Australia that c ouples oxygen delivery and end-tidal carbon dioxide (PETCO2) monitoring Thi s study compares the accuracy of PETCO2 measurements by the divided nasal c annula and those measured by a modified facemask (as currently used in this institution), with arterial partial pressure of carbon dioxide (PaCO2). In this crossover study, 30 patients who had arterial lines as part of their routine monitoring were given oxygen via nasal cannula and facemask preoper atively. The PETCO2 was measured with each device and a simultaneous PaCO2 and PaO2 measured after equilibration. The results demonstrate a significan t difference between the PETCO2 as measured by each technique. The divided nasal cannula more accurately reflects PaCO2 (mean arterial to end expired gradient of 5 mmHg) and provides a more representative trace when compared to a traditional facemask system. Both methods provided adequate oxygenatio n.