The effect of Pseudomonas aeruginosa on pulmonary function in patients with bronchiectasis

Bronchiectasis patients are susceptible to infection with Pseudomonas aeruginosa. Isolation is associated with increased severity of disease, greater airflow obstruction and poorer quality of life. It is not known whether infection by P. aeruginosa is a marker of disease severity or contributes to disease progression. Consecutive non-cystic fibrosis adult bronchiectasis outpatients (n=163) with multiple sputum cultures and follow-up pulmonary function tests were designated, according to isolation of P. aeruginosa, as "never infected" (group 1; n=67), "intermittently isolated" (group 2; n=82) and "chronically infected" (group 3; n=14). Based upon change in forced expiratory volume in one second (FEV1) % predicted levels at >= 2 yrs after presentation, longitudinal behaviour was characterised as "improvement" (>= 10% rise), "decline" (>= 10% fall) or "stability". Baseline pulmonary-function tests and longitudinal behaviour were examined in relation to pseudomonas status. There was no difference between the groups in age, sex, smoking habit or length of follow-up. Baseline FEV1 levels were highest in group 1 (mean +/- SD: 77.4 +/- 24.3) and higher in group 2 (67.3 +/- 25.7) than in group 3 (55.2 +/- 18.5). The same significant trends were seen for baseline FEV1/forced vital capacity ratios and diffusing capacity of the lung for carbon monoxide levels. Subsequent longitudinal behaviour was linked to baseline FEV1 levels, which were lowest in patients with improvement and lower in association with decline than with stability. However, longitudinal behaviour did not differ between groups 1, 2 and 3, either before or after adjustment for baseline FEV1 levels.