Transcutaneous Versus Arterial Carbon Dioxide Monitoring in Adult Polysomnography Studies.

Study objectives: To determine the accuracy of transcutaneous carbon dioxide measurements using SenTec tcPCO2 during adult polysomnography compared to arterial PCO2.

Methods: In consecutive patients having polysomnography with transcutaneous CO2 (tcPCO2) monitoring using a SenTec monitor, arterial blood gas samples were taken at the beginning and at the end of each sleep study. tcPCO2 measurements recorded at 0, 60 and 120 seconds after arterial sampling was determined in 51 participants who underwent polysomnography with tcPCO2 monitoring at the Austin Health Sleep Laboratory (Heidelberg, Victoria, Australia) during the period 01/05/22 - 10/06/22. The mean of differences between arterial carbon dioxide tension (PaCO2) and the predicted value based on tcPCO2 measurements determined at each time point for evening and morning arterial samples.

Results: Data was obtained from 37 participants. A statistically significant difference in the tcPCO2 values at the point of arterial sampling was found, with tcPCO2 on average 2.2 - 2.8 mmHg less than PaCO2 at various timepoints after arterial sampling. The upper limit of measurement accuracy represented a moderate difference (2 - 4.9 mmHg), within the clinically acceptable range of -7.5 to +7.5 mmHg variation from PaCO2 values.

Conclusions: The SenTec tcPCO2 electrode was found to be an appropriate alternative to arterial sampling for assessment of arterial carbon dioxide in adult patients in the polysomnography setting, with no significant difference in tcPCO2 accuracy based on the timing of transcutaneous measurements (up to two minutes) following arterial sampling.