Setting: Eleven referring hospitals in South Korea.
Objective: To compare therapeutic responses in chronic obstructive pulmonary disease (COPD) subgroups, classified by diffusing capacity of the lung for carbon monoxide (DL(CO)) and lung volume.
Design: A total of 130 stable male COPD patients were classified into four subgroups according to baseline DL(CO) and residual volume/total lung capacity (RV/TLC) ratio. We compared therapeutic responses to short acting β(2)-agonist (SABA) and 3-month combined inhalation of long-acting β(2)-agonist (LABA) and corticosteroid among patients with these subgroups.
Results: Among the 130 COPD patients, 41 (31.5%) had normal DL(CO) and RV/TLC, 28 (21.5%) low DL(CO) and normal RV/TLC, 31 (23.8%) normal DL(CO) and high RV/TLC, and 30 (23.1%) low DL(CO) and high RV/TLC. The normal DL(CO)/high RV/TLC subgroup showed a significantly larger flow response (changes in forced expiratory volume in 1 s) to salbutamol than the normal DL(CO)/RV/TLC subgroups, and a larger volume response (changes in forced vital capacity) than the two normal RV/TLC subgroups. The normal DL(CO)/high RV/TLC subgroup also showed significantly larger flow and volume response to 3-month combined inhalation of LABA and corticosteroid than the two normal RV/TLC subgroups.
Conclusion: COPD subgroups classified by DL(CO) and RV/TLC may have different pulmonary function responses to pharmacological treatment.