Implications of Emphysema and Lung Function for the Development of Pneumonia in Patients with Chronic Obstructive Pulmonary Disease

Background: Chronic obstructive pulmonary disease (COPD) is sometimes complicated with pneumonia, but little is known about the risk factors that promote the development of pneumonia in COPD. These risk factors were evaluated in the present study. Methods: The data of 324 patients with COPD from a prospective multi-center observational cohort with obstructive lung disease were evaluated retrospectively. To identify risk factors for the development of pneumonia in COPD, the clinical and radiological data at enrollment and the time to the first episode of pneumonia were analyzed by Cox proportional hazard analysis. Results: The median follow-up time was 1,099 days and 28 patients (8.6%) developed pneumonia. The Cox analysis showed that post-bronchodilator forced expiratory volume in one second ($FEV_1$, % of predicted) and the computed tomography (CT) emphysema extent (inspiratory V950) were independent risk factors for the development of pneumonia (post-bronchodilator $FEV_1$: hazard ratio [HR], 0.97; 95% confidence interval [CI], 0.94-1.00; p=0.048 and inspiratory V950: HR, 1.04; 95% CI, 1.01-1.07; p=0.01). Conclusion: Emphysema severity measured by CT and post-bronchodilator $FEV_1$ are important risk factors for the development of pneumonia in COPD.