Lung Diffusing Capacity in Adult Bronchiectasis: A Longitudinal Study

BACKGROUND: Recent studies described a progressive decline in lung volumes in adult bronchiectasis. Interstitial lung disease is also a feature of bronchiectasis, but whether this is associated with a decline in lung diffusing capacity (measured as the diffusing capacity of the lung for carbon monoxide [DLCO]) is not well known. OBJECTIVE: To assess longitudinal decline in diffusing capacity of the lung for carbon monoxide (DLCO) in adult bronchiectasis. METHODS: Sixty-one subjects had a detailed baseline clinical and laboratory assessment, then were followed regularly with clinical and lung-function assessment for a median 7 years. RESULTS: Baseline spirometry demonstrated mild obstructive lung disease, with a mean FEV1 of 72% of predicted, mean forced vital capacity 87% of predicted, and normal DLCO (mean DLCO 88% of predicted, and mean DLCO adjusted for alveolar volume [DLCO/VA] 100% of predicted). There was an accelerated decline in DLCO and DLCO/VA over the 7-year period. The median DLCO decline was 2.9% of predicted per year (95% CI 2.3–4.1% of predicted per year). The median DLCO/VA decline was 2.4% of predicted per year (95% CI 2.1–4.0% of predicted per year). There was a significant relationship between DLCO decline and age and decline in FEV1. CONCLUSIONS: In our cohort of patients with bronchiectasis there was a progressive DLCO decline.