[Significance and relationship between apnea and subsequent hypoxemia of OSAHS patients in a waking state].

OBJECTIVE: To explore the clinical significance and relationship between apnea and subsequent hypoxemia in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) in a waking state.

METHOD: Fifty patients with snoring at night and suspected sleep breathing disorders were selected. Each patient was asked to stop breathing at the end of normal expiration level in a waking state and then hold their breath till the decline of the arterial oxygen saturation. The duration from the beginning of stopping breathing to the beginning of the following desaturation were recorded and defined as single delay period of desaturation. The subjects were asked to complete a Chinese version of Epworth Sleepiness Scale and tested by polysomnography all night long. Then the subjects were divided into four groups according to the apnea-hypopnea index (AHI): group 1, AHI < or = 5; group 2, AHI > 5-15; group 3, AHI > 15-30; group four AHI > 30.

RESULT: The single delay period of desaturation in group 3 was shorter than that in group 1 (P < 0.05). And it in group 4 was shorter significantly than the other three groups (P < 0.01). AHI, the percentage of the total recorded time spent below 90% oxygen saturation level (TS90%), the time of sleep apnea-hypopnea per hour, heart rate and body mass index (BMI) had a negative relationship with the single delay period of desaturation (r = -0.709, -0.769, -0. 682, - 0.403, - 0.480, P < 0.01). Lowest arterial oxygen saturation (LSaO2 ) and mean arterial oxygen saturation (MSaO2) had a positive relationship with the single delay period of desaturation (r = 0.702, 0.610, P < 0.01). Age had no relationship with it. The single delay period of desaturation, AHI and LSaO2 had a linear relationship with ESS7 (r = -0.688, 0.568, -0.576, P < 0.01).

CONCLUSION: The single delay period of desaturation in OSAHS patients get shorter with the degree of severity, especially in the severe ones. The shortening of the single delay period of desaturation maybe a protective mechanism for OSAHS patients so as to reduce the severity of apnea. AHI, LSaO2, TS90% and the sleep apnea-hypopnea time per hour have a close relationship with the single delay period of desaturation and it may provide valuable information for evaluating the severity of OSAHS patients, especially to the serious one. The single delay period of desaturation has a close relationship with ESS7 and may contribute to evaluate the severity of daytime sleepiness.