[Correlations between the duration and frequency of sleep apnea episode and hypoxemia in patients with obstructive sleep apnea syndrome].

OBJECTIVE: To evaluate the relationship between the duration of apnea episodes and the severity of hypoxemia of obstructive sleep apnea-hypopnea syndrome (OSAHS) patients and explore the possible causes of the disassociation between the severity of hypoxemia and AHI in some OSAHS subjects. METHODS: Polysomnography data of eighty-two OSAHS patients was analyzed. Firstly, apnea and hypopnea events were classified into 4 groups respectively according to it's lengths, i.e., longer or equals to 10 s, 15 s, 20 s, 25 s, AHI10, AHI15, AHI20, AHI25 were obtained by calculating apnea hypopnea events per hour with respective lengths. Secondly, total apnea time per hour was calculated in all cases. Thirdly Spearman correlation coefficient and Linear regression analysis were used to measure the associations between numerical parameters referred above and three parameters of hypoxia: the lowest oxygen saturation level (LSaO2), the mean oxygen saturation level during sleep time (MeanSaO2), the percent of the total recorded time spent below 0.90 oxygen saturation level (TS90). RESULTS: The apnea-hypopnea index (AHI10, AHI15, AHI20, AHI25) correlated negatively with the LSaO2 (r was -0.636, -0.634, -0.649, -0.657), P < 0.01. The apnea-hypopnea index (AHI10, AHI15, AHI20, AHI25) correlated negatively with the MeanSaO2 (r was -0.659, -0.647, -0.648, -0.629), P < 0.01. The apnea-hypopnea index (AHI10, AHI15, AHI20, AHI25) correlated positively with the TS90 (r was 0.810, 0.806, 0.806, 0.770), P < 0.01. Further linear regression analysis all showed significant clinical value with r(2) > 0.50. The amount time of apnea events per hour of total sleep time (T) showed high correlations with LSaO2, MeanSaO2, TS90 (r was -0.650, -0.628, 0.776), while P < 0.01. CONCLUSIONS: The duration of apnea episodes has a significant clinical value in accessing the degree of hypoxia of the OSAHS patients. The TS90 combined with the LSaO2 reflects the severity of hypoxia of the OSAHS patients objectively.