PURPOSE: To assess the impact of pulmonary function as measured by spirometry on sleep disordered breathing and nocturnal hypoxemia in severely obese subjects.
METHODS: Data was obtained from 1156 subjects who participated in the Utah Obesity Study. A total of 656 of subjects underwent both spirometry and limited polysomnographic study (Embletta Portable Diagnostic System) at the time of enrollment. The interaction of Pulmonary function (Forced Expiratory Volume, FEV1, Forced Vital Capacity, FVC and FEV1/FVC ), sleep disordered breathing (Respiratory Disturbance Index, RDI), arterial oxygen saturation (SpO2), and percent of record spent below SpO2 of 90% was studied.
RESULTS: There were 544 females and 112 males. Mean age of the participants was 44.1 ± 11.3 years, Body Mass Index (BMI) 46.1 +/- 7.4, Mean FVC was 95% (± 14%) predicted, FEV1 was 96.9% and the mean FEV1/FVC was 79.3%. Restrictive chest disease (FVC < 80% predicted) was found in 86 of the 656 subjects (13.1%). Mean RDI was 21/hour and average SpO2 was 91.1%. Time spent with SpO2 below 90% averaged 25.1% of the recording duration. There were inverse correlations between FVC and RDI (r= -0.221, p< 0.0001), and time spent below SpO2 of 90% (r= -0.324, p=.0001) and there was a positive correlation between FVC and average SpO2 (r=0.324, p<.005).
CONCLUSIONS: Severe obesity was not associated with obstructive or restrictive chest disease as seen on spirometry except in a minority of subjects. FVC correlates inversely with RDI and time spent hypoxemic. Higher FVC was associated with higher mean SpO2.
CLINICAL IMPLICATIONS: Reduced lung volumes in patients with severe obesity may be responsible for severity of sleep disordered breathing and nocturnal hypoxemia. Future studies may be required to determine the effect of pulmonary function in the recumbent position.
DISCLOSURE: The following authors have nothing to disclose: Sandeep Chowdhary, Tom Cloward, Kevin Shilling, Wael Berjaoui, Robert Farney, Tom Nuttall, James Walker
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