Clinical Predictors of Obesity Hypoventilation Syndrome in Obese Subjects With Obstructive Sleep Apnea

Abstract

BACKGROUND: Arterial blood gas (ABG) analysis is not a routine test in sleep laboratories due to its invasive nature. Therefore, the diagnosis of obesity hypoventilation syndrome (OHS) is underestimated. We aimed to evaluate the differences in subjects with OHS and pure obstructive sleep apnea (OSA) and to determine clinical predictors of OHS in obese subjects. METHODS: Demographics, body mass index (BMI), Epworth Sleepiness Scale score, polysomnographic data, ABG, spirometric measurements, and serum bicarbonate levels were recorded. RESULTS: Of 152 obese subjects with OSA (79 females/73 males, mean age of 50.3 +/- 10.6 y, BMI of 40.1 +/- 5.6 kg/m(2), 51.9% with severe OSA), 42.1% (n = 64) had OHS. Subjects with OHS had higher BMI (P = .02), neck circumference (P 27 mmol/L as the cutoff gives a satisfactory discrimination for the diagnosis of OHS (sensitivity of 76.6%, specificity of 74.6%, positive predictive value of 54.5%, negative predictive value of 88.9%). A nadir S-pO2 of = 27 mmol/L and/or a nadir S-pO2 of < 80% as a screening measure, only 3 of 64 subjects with OHS were missed. CONCLUSIONS: Serum bicarbonate level and nadir saturation were independent predictive factors for the diagnosis of OHS. (C) 2015 Daedalus Enterprises