Lack of benefit of continuous positive airway pressure on lung function in patients with overlap syndrome

Obstructive sleep apnea (OSA) has been shown to be an inflammatory stimulus and may potentially result in a deterioration in the respiratory status of patients with coexistent chronic obstructive pulmonary disease (COPD) (overlap syndrome). We hypothesized that with treatment of OSA, there would be an improvement in coexistent COPD in overlap patients. We also sought to characterize overlap patients by comparing them with patients with either OSA or COPD alone. We performed a retrospective study of patients who attended a university-affiliated Veterans Affairs hospital. Demographic and clinical data were obtained from the medical charts and pharmacy records for the preceding two years and for the two years following the initiation of continuous positive airway pressure (CPAP) therapy. Overlap patients had moderately severe sleep apnea (AHI 28.6 +/- 4.2) and moderately severe COPD (FEV1 = 1.94 +/- 0.10 L). The prevalence of overlap syndrome in COPD patients was 11.9%, and 41% in OSA patients. Overlap patients who were compliant with CPAP therapy experienced a greater decrease in FEV1, percent predicted FEV1, percent decrease in FEV1, FVC, percent predicted FVC, and percent decrease in FVC when compared with noncompliant patients. A very strong correlation was found between the average hours of CPAP use per day and the percent decrease in FEV1 (r = 0.69, p = 0.003). There was a similar strong correlation for the decrease in FEV1 and percent predicted FEV1. OSA is common in COPD patients; similarly, COPD is common in OSA patients. Treatment of OSA with CPAP therapy in patients with overlap syndrome may not lead to an improvement in the coexistent COPD.