• Ahmed S BaHammam.
• University Sleep Disorders Center, College of Medicine, King Saud University, PO Box 225503, Riyadh 11324, Kingdom of Saudi Arabia. Tel. +966 (11) 4679179. Fax. +966 (11) 4679495. E-mail. ashammam2@gmail.com.
• Saudi Med J. 2015 Feb 1; 36 (2): 181189181-9.

ObjectivesTo assess the prevalence, clinical characteristics, and predictors of obesity hypoventilation syndrome (OHS) in a large sample of Saudi patients with obstructive sleep apnea (OSA).MethodsThis prospective observational study consisted of 1693 patients who were diagnosed to have sleep-disordered breathing using type I attended polysomnography (PSG) between January 2002 and December 2012 in the University Sleep Disorders Center (USDC) at King Saud University Hospital, Riyadh, Kingdom of Saudi Arabia.ResultsOut of 1693 OSA patients, OHS was identified in 144 (8.5%) (women 66.7%). Compared with the pure OSA patients, the OHS patients were significantly older (57.4±13.4 years versus 46.8±13.7 years), had a higher body mass index (44.6±10.8 versus 35.7±9.2 kg/m²), a higher daytime partial pressure of carbon dioxide (PaCO2) (56.5±12.7 versus 41.6±6.7 mmHg), a longer duration of nocturnal oxygen saturation (nSaO2) <90% (71.0±34.3 versus 10.5±20.5 minutes), and a higher apnea hypopnea index (68.2±47.1 versus 46.5±34.1 events/hour). A multivariate logistic regression analysis showed that serum bicarbonate (odds ratio [OR]=1.17, p=0.0001, confidence interval [CI]=1.10-1.25), and duration of nSaO2 <90% (OR=1.05, p=0.0001, CI=1.04-1.06) were predictors of OHS.ConclusionObesity hypoventilation syndrome is common among Saudi OSA patients referred to the Sleep Disorders Center. Serum bicarbonate and duration of nSaO2 <90% are independent predictors of OHS among patients with OSA.

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