Purpose The diagnosis and severity of obstructive sleep apnea (OSA) are commonly based on the apnea hypopnea index (AHI). However, patients with similar severity AHIs may show widely varying comorbidities and risks for cardiovascular disease, which may be associated with different severities of nocturnal hypoxia. The percentage of cumulative time with oxygen saturation below 90% in total sleep time (T90) is receiving increasing attention in OSA research because it describes the duration and degree of hypoxia during the whole sleep. This study aimed to explore the distribution of T90 in OSA patients with similar severity and to evaluate the relationship between T90 and hypertension. Patients and Methods A total of 775 patients with OSA were enrolled in this study, all participants were divided into groups according to the T90 value: light hypoxia (T90≤5%), mild hypoxia (T90 accounted for 5–10%), moderate hypoxia (T90 accounted for 10–25%), and severe hypoxia (T90>25%). Multivariate logistic regression analysis was performed to assess the association between T90 and hypertension. Results Of the patients with mild OSA, 94.33% had light hypoxia, and 88.64% of moderate OSA patients had light hypoxia. The proportions of light, mild, moderate, and severe hypoxia among patients with severe OSA were 28.60%, 17.69%, 21.40%, and 32.31%, respectively. After adjustment for potential confounders, the risk of hypertension in patients with severe OSA increased according to the severity categories of T90. The odds ratio for T90 accounting for 10–25% relative to T90≤5% was 2.544 (95%confidence interval, 1.254–5.164; P=0.010) and as high as 2.692 (95%confidence interval, 1.403–5.166; P=0.003) in patients with T90>25%. Conclusion OSA patients with similar degree of AHI may have different T90 values, especially in severe OSA. A higher T90 was independently associated with the risk of hypertension after adjustment for traditional risk factors in patients with severe OSA. Our findings highlight the potential role for T90 in predicting hypertension in patients severe OSA.

Background Numerous predictive formulas based on different ethnics have been developed to determine continuous positive airway pressure (CPAP) for patients with obstructive sleep apnea (OSA) without laboratory-based manual titrations. However, few studies have focused on patients with OSA in China. Therefore, this study aimed to develop a predictive equation for determining the optimal value of CPAP for patients with OSA in China. Methods 526 pure moderate to severe OSA patients with attended CPAP titrations during overnight polysomnogram were spited into either formula derivation (419 patients) or validation (107 patients) group according to the treatment time. Predictive model was created in the derivation group, and the accuracy of the model was tested in the validation group. Results Apnea hypopnea index (AHI), body mass index (BMI), longest apnea time (LAT), and minimum percutaneous oxygen saturation (minSpO2) were considered as independent predictors of optimal CPAP through correlation analysis and multiple stepwise regression analysis. The best equation to predict the optimal value of CPAP was: CPAPpred = 7.581 + 0.020*AHI + 0.101*BMI + 0.015*LAT-0.028*minSpO2 (R2 = 27.2%, p < 0.05).The correlation between predictive CPAP and laboratory-determined manual optimal CPAP was significant in the validation group (r = 0.706, p = 0.000). And the pressure determined by the predictive formula did not significantly differ from the manually titrated pressure in the validation cohort (10 ± 1 cmH2O vs. 11 ± 3 cmH2O, p = 0.766). Conclusions The predictive formula based on AHI, BMI, LAT, and minSpO2 is useful in calculating the effective CPAP for patients with pure moderate to severe OSA in China to some extent.

Obstructive sleep apnea (OSA) plays an important role in the pathogenesis of hypertension. The aim of this cross-sectional study was to explore the clinical and polysomnographic characteristics of OSA patients with hypertension and to explore the gender differences in the relationship between rapid eye movement (REM) OSA and hypertension. Patients and Methods: A total of 808 patients with OSA at a tertiary hospital were enrolled in this study, and OSA patients were divided into groups presenting with or without hypertension. The clinical and polysomnographic characteristics were compared between the groups. Multivariate binary logistic analysis was performed to assess the association between REM OSA and hypertension.Results: After adjustment for potential confounders, the risk of hypertension in patients with OSA increased with severity categories of apnea hypopnea index during rapid eye movement sleep stage (REM AHI) (OR = 1.61 for REM AHI ≥58.87 events/h relative to REM AHI <30.50 events/h, 95% CI 1.07-2.42, P = 0.022). Consistent with this, when taken as a continuous variable, this association still remains significant (OR = 1.007, 95% CI 1.001-1.014, P < 0.05). This effect was more pronounced in women patients, the OR for REM AHI ≥57.24 events/h relative to REM AHI <30.36 events/h was 2.79 (95% CI, 1.16-6.73; P = 0.022); however, there was no significant difference in male patients. Conclusion: REM AHI was significantly and positively associated with hypertension in patients with OSA, and the effect was more pronounced in female patients.

Objective: Obstructive sleep apnea-hypopnea syndrome (OSA) is a disease of obstructive apnea or hypopnea caused by a repeated partial or complete collapse of the upper airway during sleep. The inspiratory part of the flow-volume curve (F-V curve) can be used as an auxiliary means to evaluate upper airway obstruction in adults. This study is to evaluate the ability of the F-V curve to predict the OSA and explore inspiratory indicators related to airway obstruction during sleep. Methods: There were 332 patients included in this crosssectional study, who were accompanied by snoring, daytime sleepiness and other symptoms, with suspicion of OSA. According to the nocturnal polysomnography, the subjects were distributed into mild to moderate OSA group, severe OSA group and non-OSA group. A pulmonary function test was used to collect the subjects' spirometry and F-V curves. Results: There was no significant difference in a variety of indices derived from the F-V curve between OSA and normal subjects, including 25% inspiratory flow rate, middle inspiratory flow rate, 75% inspiratory flow rate, peak flow rate, and forced inspiratory flow rate in the first second. The pulmonary function parameters were significantly correlated with the weight, age and sex of the subjects. Conclusion: These findings suggest that the inspiratory curve of pulmonary function cannot evaluate the upper airway abnormalities in patients with obstructive apnea-hypopnea syndrome.