Small airways dysfunction in patients with AIDS and Pneumocystis carinii pneumonia

Abnormalities of small airways function may have clinical relevance in AIDS patients with Pneumocystis carinii pneumonia (PCP) since obstructive dysfunction at alveolar levels may impede delivery of aerosolized medication. This study was designed to determine if small airways dysfunction is present in AIDS patients with PCP despite normal standard spirometric results.

Ten AIDS patients with documented PCP and no other identifiable pulmonary infection without respiratory failure and with a normal FEV1/FVC ratio were evaluated.

Small airways function was assessed by the FEF75 and the change in maximum expiratory flow while breathing a helium-oxygen mixture compared to room air (delta Vmax50%) with and without bronchodilator administration. Testing was done before and after completion of intravenous therapy for PCP.

Despite absence of cough or wheezing at the time of evaluation and a normal FEV1/FVC ratio, significant obstructive dysfunction of the small airways was demonstrated in 6 of 10 patients, which improved with bronchodilators. Three weeks of intravenous therapy for PCP had no effect on these abnormalities. The degree of small airways dysfunction was greater than could be explained by smoking history alone.

Small airways dysfunction, which can be improved with bronchodilator administration, may be present in AIDS patients with PCP despite normal spirometry and absence of cough or wheezing. Screening for small airways dysfunction may identify patients who might benefit from bronchodilator administration prior to inhalation of aerosolized medications.