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 co 2) monitoring in obstructive sleep apnea (OSA) patients during sleep and to explore whether the ET co 2 value may explain a significant portion of the relationship between ET co 2 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 co 2 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 co 2 [(T − W) ET co 2]; one group, 20 patients with (T − W) ET co 2 less than 0, and the other group,18 patients with (T − W) ET co 2 greater than 0. Results Group with (T − W) ET co 2 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 o 2, 67.85 ± 10.08 vs. 82.61% ± 6.07%; mean Sa o 2, 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 co 2 potentially can be used in continuous monitoring of OSA patients. And, (T − W) ET co 2 can indicate the severity of OSA.