Hypoxia parameters, physical variables, and severity of obstructive sleep apnea

Abstract

Objective: To determine the relation between hypoxia and physical parameters in patients who had different levels of severity of obstructive sleep apnea (OSA).

Methods: This was a retrospective, cross-sectional study of 259 men who were evaluated with overnight polysomnography. Severity of OSA was graded based on the apnea-hypopnea index (AHI): normal/simple snoring (n=31); mild OSA (n=70); moderate OSA (n=63); severe OSA (n=95). Patients with different severity were divided into subgroups, based on having the lowest or highest values of the total sleep time with oxygen saturation <90% (ST90) or minimum oxygen saturation (min SaO(2)).

Results: Median AHI was 20.4 events/hour. Univariate analysis showed that ST90 was correlated with AHI (r=0.772; p <= 0.001) and Epworth sleepiness scale (ESS) (r=0.344; p <= 0.001), and min SaO(2) was inversely correlated with AHI (r=-0.748; p <= 0.001) and ESS (r=-0.319; p <= 0.001). Multivariate linear regression showed that ST90 was independently associated with AHI, ESS, and neck circumference, and min SaO(2) was independently inversely associated with AHI, ESS, and body mass index (BMI). In patients who had severe OSA, the subgroups which had lowest and highest min SaO(2) differed significantly in BMI, modified Mallampati score, neck and waist circumferences, and ret-roglossal Muller grade. In patients with percentage of sleep time with oxygen saturation below 90% (CT90) <10%, the upper limit of ST90 was 36 minutes and corresponded to 70% lower limit of min SaO(2).

Conclusion: Hypoxia parameters show significant variation in OSA severity categories. None of the physical parameters had clinically useful relations with hypoxia parameters in OSA patients except patients who had severe OSA.