Factors influencing sleep time with oxygen saturation below 90% in sleep-disordered breathing.

OBJECTIVES/HYPOTHESIS: To determine factors influencing sleep time with oxygen saturation below 90% (ST₉₀) in a population referred to a tertiary sleep center for assessment of possible sleep-disordered breathing (SDB).

STUDY

DESIGN

Retrospective review of demographic and polysomnographic data of 731 consecutive patients with suspected SDB.

METHODS

Bivariate correlation analyses were performed, and Spearman rho coefficients were calculated. Variables with a marginal association with ST₉₀ (P < .05) in the bivariate analysis were included into the multiple regression analysis.

RESULTS

The distributions of SDB were as follows: normal/simple snoring, 18.2%; mild obstructive sleep apnea (OSA), 25.6%; moderate OSA, 17.4%; and severe OSA, 38.9%. The univariate analysis revealed a significant correlation between ST₉₀ and age (r = 0.204), body mass index (BMI) (r = 0.440), arousal index (r = 0.754), apnea-hypopnea index (AHI) (r = 0.761), mean oxygen saturation (SaO₂) (r = -0.506), and mean O₂ desaturation (r = 0.858) (P < .001 for all parameters). In multiple regression analysis, age (P < .001), BMI (P = .040), male gender (P = .001), AHI (P < .001), mean SaO₂ (P < .001), and mean O₂ desaturation (P < .001) were found to be independent parameters influencing ST₉₀. Furthermore, these parameters explained a significant proportion of variance in ST₉₀ (R(2)  = 0.794, F (6, 729) = 464.65, P < .001). Although there was a strong correlation between AHI and ST₉₀ (r = 0.76, P < .001), a large variation of ST₉₀ values was observed, especially within the severe OSA group.

CONCLUSIONS

The study results provide supporting evidence that patients with similar AHI may have quite different values of ST₉₀, and thereby hypoxia. The stratification of patients with OSA according to AHI combined with ST₉₀ may allow better identification of prognostic information.