Evaluation of the apnea-hypopnea index determined by the S8 auto-CPAP, a continuous positive airway pressure device, in patients with obstructive sleep apnea-hypopnea syndrome.

OBJECTIVE: Continuous positive airway pressure (CPAP) has been established as an effective treatment for obstructive sleep apnea-hypopnea syndrome (OSAHS). Recently, several auto-CPAP devices that can detect upper airway obstructive events and provide information about residual events while patients are on CPAP have come into clinical use. The purpose of this study was to compare the apnea-hypopnea index (AHI) determined by the S8 auto-CPAP device with the AHI derived by polysomnography in patients with OSAHS.

METHOD: Consecutive patients with OSAHS titrated on S8 auto-CPAP were included. The correlation between AHI determined by manual scoring (AHI-PSG) and by S8 (AHIS8) during an overnight in-hospital polysomnogram with the patient on CPAP was assessed. Furthermore, the apnea index (Al) and the hypopnea index (HI) were evaluated separately.

RESULTS: Seventy patients with OSAHS (94% men) were enrolled. The mean AHI on the diagnostic study was 51.9 +/- 2.4. During the titration, this device markedly suppressed the respiratory events (AHI-PSG, 4.2 +/- 0.4; AI, 1.9 +/- 0.3; HI, 2.3 +/- 0.3). On the other hand, the AHI-S8 was 9.9 +/- 0.6 (AI-S8, 2.4 +/- 0.3; HI-S8, 7.5 +/- 0.4). There was a strong correlation between the overall AHI-PSG and the AHI-S8 (r = 0.85, p < 0.001), with a stronger correlation in the apnea component AI-PSG and the AI-S8 (r = 0.93, p < 0.001), whereas there was a weaker correlation between the HI-PSG and the HI-S8 (r = 0.67, p <0.001).

CONCLUSIONS: Using the same airflow signals as those of the CPAP device, a strong correlation between the AHI-PSG and the AHI-S8 was observed. However, the correlation was weakened when the analysis was limited to the HI.