End-tidal carbon dioxide concentration monitoring in obstructive sleep apnea patients

Abstract Purpose The objective of this study was to investigate the end-tidal carbon dioxide concentration (ET co2 ) monitoring in obstructive sleep apnea (OSA) patients during sleep and to explore whether the ET co2 value may explain a significant portion of the relationship between ET co2 value and apnea/hypopnea index (AHI) and nocturnal oxygenation indices. Materials and methods Thirty-eight consecutive patients underwent overnight polysomnography and were synchronously monitored for ET co2 using an microstream capnometer. Mean and maximum values during wake time and different sleep stages were recorded. We grouped 38 OSA patients into 2 subgroups on the basis of their difference of mean total sleep time and wake time ET co2 [(T − W) ET co2 ]; one group, 20 patients with (T − W) ET co2 less than 0, and the other group,18 patients with (T − W) ET co2 greater than 0. Results Group with (T − W) ET co2 less than 0 patients exhibited higher AHI (mean ± SD, 68.58 ± 22.78 vs. 27.61 ± 19.44 events/h) and lower nocturnal oxygenation indices (minimum Sa o2 , 67.85 ± 10.08 vs. 82.61% ± 6.07%; mean Sa o2 , 91.29 ± 3.31 vs. 95.15% ± 1.88%) compared with the other group. Conclusions In summary, the study provides preliminary data showing that ET co2 potentially can be used in continuous monitoring of OSA patients. And, (T − W) ET co2 can indicate the severity of OSA.