Overnight Changes in Lung Function of Obese Patients with Obstructive Sleep Apnoea.

PURPOSE: Obstructive sleep apnoea (OSA) is a prevalent disorder, characterised by collapse of the upper airways during sleep. The impact of sleep-disordered breathing on pulmonary function indices is however currently not well described. The aim of the study was to evaluate diurnal change in lung function indices in a cohort of patients with OSA and relate pulmonary function changes to disease severity.

METHODS

42 patients with OSA and 73 healthy control subjects participated in the study. Asthma and COPD were excluded in all volunteers following a clinical and spirometric assessment. Spirometry was then performed in all subjects in the evening and the morning following a polysomnography study.

RESULTS

There was no difference in evening or morning FEV1 or FVC between patients and control subjects (p > 0.05). Neither FEV1 nor FVC changed in control subjects overnight (p > 0.05). In contrast, FEV1 significantly increased from evening (2.18/1.54-4.46/L) to morning measurement (2.26/1.42-4.63/L) in OSA without any change in FVC. The FEV1 increase in OSA was related to male gender, obesity and the lack of treatment with statins or β-blockers (all p < 0.05). A tendency for a direct correlation was apparent between overnight FEV1 change and RDI (p = 0.05, r = 0.30).

CONCLUSIONS

Diurnal variations in spirometric indices occur in patients with OSA and FEV1 appears to increase in subjects with OSA overnight. These changes occur in the absence of change in FVC and are directly related to the severity of OSA. These findings dictate a need to consider time of lung function measurement.