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Abstract Rationale Impaired exercise ventilatory efficiency (high ventilatory requirements for CO2 V̇e/V̇co2) provides an indication of pulmonary gas exchange abnormalities in chronic obstructive pulmonary disease (COPD). Objectives To determine 1) the association between high V̇e/V̇co2 and clinical outcomes (dyspnea and exercise capacity) and its relationship to lung function and structural radiographic abnormalities; and 2) its prevalence in a large population-based cohort. Methods Participants were recruited randomly from the population and underwent clinical evaluation, pulmonary function, cardiopulmonary exercise testing, and chest computed tomography. Impaired exercise ventilatory efficiency was defined by a nadir V̇e/V̇co2 above the upper limit of normal (ULN), using population-based normative values. Measurements and Main Results Participants included 445 never-smokers, 381 ever-smokers without airflow obstruction, 224 with Global Initiative for Chronic Obstructive Lung Disease (GOLD) 1 COPD, and 200 with GOLD 2–4 COPD. Participants with V̇e/V̇co2 above the ULN were more likely to have activity-related dyspnea (Medical Research Council dyspnea scale ⩾ 2; odds ratio 5–95% confidence intervals, 1.77 1.31 to 2.39) and abnormally low peak V̇ o 2 (V̇ o 2peak below the lower limit of normal; odds ratio, 4.58 3.06 to 6.86). The Kco had a stronger correlation with nadir V̇e/V̇co2 (r = −0.38; P 0.001) than other relevant lung function and computed tomography metrics. The prevalence of V̇e/V̇co2 above the ULN was 24% in COPD (similar in GOLD 1 and 2 through 4), which was greater than in never-smokers (13%) and ever-smokers (12%). Conclusions V̇e/V̇co2 above the ULN was associated with greater dyspnea and low V̇o2peak and was present in 24% of all participants with COPD, regardless of GOLD stage. The results show the importance of recognizing impaired exercise ventilatory efficiency as a potential contributor to dyspnea and exercise limitation, even in mild COPD.
Phillips et al. (Fri,) studied this question.