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

¹ Host Defence Unit
² Interstitial Lung Disease Unit Royal Brompton Hospital, London

^* To whom correspondence should be addressed. E-mail: r.wilson{at}rbh.nthames.nhs.uk.

	Abstract

Bronchiectasis patients are susceptible to infection with Pseudomonas aeruginosa. Isolation is associated with more severe disease, greater airflow obstruction and worse 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 percentage predicted FEV₁ levels at least two years 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, gender, smoking habit or length of follow up. Baseline FEV₁ levels were highest in Group 1 (77.4 (24.3)) (mean (SD)) and higher in Group 2 (67.3 (25.7)) than in Group 3 (55.2 (18.5)), p<0.005. The same significant trends were seen for baseline FEV₁/FVC ratios and DLCO 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, p<0.00005. However, longitudinal behaviour did not differ between groups I, 2 and 3, either before or after adjustment for baseline FEV₁ levels.

Infection by P. aeruginosa occurs in bronchiectasis patients with more severe impairment of pulmonary function but does not influence rate of decline in pulmonary function either before or after adjustment for baseline disease severity. Thus P. aeruginosa is a marker of severity but is not linked to accelerated decline in pulmonary function.

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