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 (ETco₂) monitoring in obstructive sleep apnea (OSA) patients during sleep and to explore whether the ETco₂ value may explain a significant portion of the relationship between ETco₂ 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 ETco₂ 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 ETco₂ [(T − W) ETco₂]; one group, 20 patients with (T − W) ETco₂ less than 0, and the other group,18 patients with (T − W) ETco₂ greater than 0.

Results

Group with (T − W) ETco₂ 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 Sao₂, 67.85 ± 10.08 vs. 82.61% ± 6.07%; mean Sao₂, 91.29 ± 3.31 vs. 95.15% ± 1.88%) compared with the other group.

Conclusions

In summary, the study provides preliminary data showing that ETco₂ potentially can be used in continuous monitoring of OSA patients. And, (T − W) ETco₂ can indicate the severity of OSA.