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 [D(LCO)]) is not well known.

Objective: To assess longitudinal decline in diffusing capacity of the lung for carbon monoxide (D(LCO)) 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 FEV(1) of 72% of predicted, mean forced vital capacity 87% of predicted, and normal D(LCO) (mean D(LCO) 88% of predicted, and mean D(LCO) adjusted for alveolar volume [D(LCO)/V(A)] 100% of predicted). There was an accelerated decline in D(LCO) and D(LCO)/V(A) over the 7-year period. The median D(LCO) decline was 2.9% of predicted per year (95% CI 2.3-4.1% of predicted per year). The median D(LCO)/V(A) decline was 2.4% of predicted per year (95% CI 2.1-4.0% of predicted per year). There was a significant relationship between D(LCO) decline and age and decline in FEV(1).

Conclusions: In our cohort of patients with bronchiectasis there was a progressive D(LCO) decline.