Cardiorespiratory consequences of sleep apnoea syndrome in patients with massive obesity

Assessment of cardiorespiratory consequences of sleep apnoea syndrome (SAS) is difficult owing to confounding factors, especially obesity, that are strongly associated with SAS. This study was designed to assess the cardiorespiratory consequences of SAS by comparing the results of a comprehensive cardiorespiratory evaluation in apnoeic and nonapnoeic patients with massive obesity. In a retrospective chart-review study, we studied 60 patients with massive obesity defined by a body mass index (BMI) >40 kg.m(-2), presenting no chronic respiratory disease, who underwent an extensive assessment of cardiorespiratory consequences of obesity, including overnight polysomnography, lung function tests, arterial blood gas analysis, evaluation of vascular risk factors, myocardial scintigraphy with dipyridamole stress-test, isotopic ventriculography, Doppler echocardiography and Holter electrocardiogram recording. SAS defined by an apnoea + hypopnoea index (AHI) > or = 10 was diagnosed in 42% of patients (25 out of 60). Mean+/-SD AHI of SAS-positive (SAS+) patients was 38+/-24. Age, BMI, ventilatory function parameters, prevalence of smoking history and diabetes mellitus did not differ significantly in SAS+ versus SAS-negative (SAS-) groups. The following complications were observed more frequently in SAS+ than in SAS- patients: daytime hypoxaemia (35 vs 9%, p<0.02), pulmonary arterial hypertension (36 vs 7%, p<0.05) and increased interventricular septal thickness (50 vs 15%, p<0.03). No association was found between SAS on the one hand and systemic arterial hypertension, coronary artery disease, left ventricular dysfunction and nocturnal cardiac arrhythmias on the other. Nocturnal apnoeas in massive obesity may thus be associated with moderate daytime hypoxaemia, mild pulmonary arterial hypertension and moderate left ventricular hypertrophy, but not with severe cardiorespiratory complications.