Effects on diffusing capacity and ventilation--perfusion relationships of budesonide inhalations for 2 months in chronic obstructive pulmonary disease (COPD).

Forced expiratory volumes are reduced in chronic obstructive pulmonary disease (COPD), mainly as a result of inflammatory and morphological changes in the small airways (with a diameter < 2 mm) and in the alveoli. However, it is difficult to detect minor changes in small airways by spirometry measurements. To study the effects on small airways of inhaled corticosteroids (ICS), 19 stable COPD patients were investigated; 15 were evaluated by ventilation-perfusion (V(A)/Q) relationships, assessed by the multiple inert gas elimination technique, and by diffusing capacity for carbon monoxide (DL(CO)), assessed by the single breath technique. Measurements were repeated after 2 months of budesonide inhalations (800 microg) twice daily. Before ICS treatment: mean forced expiratory volume in 1 sec (FEV1) as a percentage of predicted (% P) was 40.1 (+/- 16.0)%, DL(CO)% P was 45.7 (+/- 25.0)% and 6.0 (+/- 6.4)% of the ventilation was directed at high V(A)/Q areas. The mean of the V(A)/Q ratio for ventilation (V-mean) was 2.7 times higher than normal. After 2 months of ICS: the mean of DL(CO)% P increased by 8.6 (+/- 19.4)%, and FEV1/vital capacity decreased by 6.9 (+/- 11.3)%. Basal morning and ACTH-stimulated S-cortisol levels were significantly reduced. All the V(A)/Q relationships remained unchanged. In conclusion, a significant increase in diffusion capacity for carbon monoxide levels after treatment with corticosteroid inhalations for 2 months was shown, but no significant improvements were found in forced expiratory airflow, lung volumes, or V(A)/Q relationships.