Obesity-hypoventilation syndrome and associated factors

Obesity causes important alterations in the respiratory physiology like sleep obstructive apnoea (SOA) and obesity-hypoventilation syndrome (OHS), both associated with high morbidity and mortality. Also, these entities are clearly infradiagnosed and in the case of OHS the prevalence is unknown in the general obese population. To determine the prevalence of OHS in the population of patients with morbid obesity and to know the comorbidity related with OHS, the associated respiratory symptoms and the pulse oximetry alterations.

Descriptive study. Selection of 136 adult patients with morbid obesity (BMI >40). Collected were, anthropometric data, toxic habits, concomitant disease, symptom data, analytic data, dyspnoea grade, sleepiness scale (Epworth Test), electrocardiogram, chest X-ray, spirometry, nocturne ambulatory pulse oximetry and arterial gasometry.

136 were studied, mean age 60 years old (SD 12.9 years), 73% (98) were women; 6.6% of patients presented diurnal hypercapnia indicative of OHS; 72% presented high blood pressure, 44% dyslipidaemia, 18% presented cardiovascular disease, 83% snored and 46% had apnoea; 30% presented stageII dyspnoea and 10% stageIII. The desaturation/hour index was above 3% ≥30 of occasions in 28.6% of patients and the percentage of patients with saturations <90% more than 30% of the time was 23.5%. The results were worse in patients with OHS.

The prevalence of OHS was lower than expected. Noteworthy was the high comorbidity of cardiovascular disease and the high frequency of respiratory symptoms associated with important alterations of pulse oximetry.