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 FEV₁ 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 FEV₁.

CONCLUSIONS: In our cohort of patients with bronchiectasis there was a progressive D_LCO decline.