Characteristics of community-acquired pneumonia in patients with chronic obstructive pulmonary disease.

Study Objectives: Community-acquired pneumonia is a frequent event in the course of chronic obstructive pulmonary disease (COPD). The aim of the present study was to provide information on clinical and microbiological characteristics and outcome of community-acquired pneumonia in these patients, in a comparative study with the non-COPD population.
Design: Prospective study of cases.
Setting: A university hospital in Lleida, Spain.
Patients: During a 6 year-period, we prospectively studied the clinical and radiological manifestations, microbiological data and outcome of all patients with community-acquired pneumonia. A comparative analysis of characteristics of pneumonia between 132 patients with a definitive diagnosis of COPD and 575 patients who did not have this underlying disease was performed.
Measurements and Results: COPD was associated with an older and predominantly male population. These patients frequently had concomitant comorbidities such as diabetes mellitus or chronic heart failure. Clinical presentation was more severe, manifested by septic shock, tachypnea, lower values of pH, pO(2) and oxygen saturation, and greater values of pCO(2). Purulent expectoration was also more frequent in this subset of patients. Admission was usually required for patients with COPD, and length of hospitalization was significantly increased; however, difference in the mortality rate was not observed. Although the spectrum of responsible microorganisms was very similar, the incidence of Pseudomonas aeruginosa and other Gram-negative bacilli was increased in COPD, particularly among patients with advanced situation and/or oral corticosteroid treatment.
Conclusions: Community-acquired pneumonia in patients with COPD was associated with epidemiological and clinical particularities mainly related to the underlying disease but showed only minor differences in outcome parameters. Gram-negative bacilli and P. aeruginosa are potential pathogens that need to be considered.