S E T T I N G : Eleven referring hospitals in South Korea. O B J E C T I V E :To compare therapeutic responses in chronic obstructive pulmonary disease (COPD) subgroups, classifi ed by diffusing capacity of the lung for carbon monoxide (DL CO ) and lung volume. D E S I G N : A total of 130 stable male COPD patients were classifi ed 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. CHRONIC obstructive pulmonary disease (COPD) is characterised by chronic airfl ow limitation that is not fully reversible. 1 COPD is not a single disease but rather a group of conditions with variable clinical, physiological and radiographic manifestations. 2
S U M M A R YThe Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines recommend different treatment strategies based on the severity of airfl ow limitation, as assessed by post-bronchodilator forced expiratory volume in 1 second (FEV 1 ) values. 1 Although FEV 1 is useful in the diagnosis and physiological staging of COPD, arbitrary stratifi cations of SDL and YMO contributed equally to this article.
THE DEVELOPMENT of pulmonary hypertension (PH) is often observed in advanced chronic obstructive pulmonary disease (COPD) and indicates a poor prognosis, with a 5-year survival rate of 20-36%. 1,2 PH primarily occurs in COPD patients with severe hypoxaemia; fortunately, however, the PH is typically mild. 3 Hypoxaemia increases pulmonary artery pres-
S U M M A R Ysure (PAP) through hypoxic pulmonary vasoconstriction and vascular remodelling. 4 However, there is a poor correlation between lung function parameters and PAP, suggesting that factors other than airway obstruction and/or loss of alveolar surface may play a role in its aetiology.Recent studies have shown that a proportion of patients with only moderate airway obstruction have severe PH. 5,6 Disproportionate PH in COPD patients seems best defi ned as at least moderate elevation in SDL and YMO contributed equally to this article.
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