The aim of the study was to determine anthropometric and arterial blood gas parameters predictors of obesity-hypoventilation syndrome(OHS) among obese patients with obstructive sleep apnea syndrome (OSAS).

Methods:prospective,descriptive and analytic study which concerned 108 obese patients who hadanthropometric measurements (weight,size,BMI,waist size,neck circumference), polysomnographic recording ,according to the recommendations of the AASM and arterial blood gasanalysis.
Correlations and regressions were performed, alsothe odds ratio and relative risk were determined.
Results: The mean ageinpatients with OHS was59±15 yearsvs56±11 years for control patients (OSAS group),mean body mass index (BMI) was (44,9± 7,53 kg/m2vs 43,7 ± 6,65 kg/m2,respectively), the waist size was (125,01± 18,9 vs 122,6 ± 17.2, respectively),neck circumference was (46.10±3.79cm vs44.03±5.03cm,respectively, p=0.03).

and arterial blood gas data:Pa02of obese people with OHS 59± 11 vs 77±11 for control patients,PaCO2 was of( 51± 9 mmhgvs36 ±3 mmhg,respectively) and HCO3 (29± 4 mmol/L vs  23± 4 mmol/L, respectively,p<0.0001).
The odds ratio for neck circumference is1.1063>1with sensitivity of 50%, specificity of 72%.

The odds ratio of HCO3 was2. 177>1 with sensitivity of 88.1%, specificity of 73.1%.

Conclusion:Bicarbonates and neck circumferenceare independent predictive factors for OHS in the obese patients with obstructivesleep apnea syndrome.