Chest
Clinical InvestigationsAltered Exercise Gas Exchange and Cardiac Function in Patients with Mild Chronic Obstructive Pulmonary Disease
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Subjects
Fifty-one men and women with mild COPD were studied. An additional 39 men and women without evidence of COPD or an acute or chronic disease process served as controls. No individual entered into this study was less than 55 years of age, and no subject was actively engaged in an aerobic training program at the time of testing. All patients entered into this study met the following criteria: (1) ratio of FEV1 to forced vital capacity (FVC) less than 70 percent; (2) total lung capacity (TLC)
RESULTS
Physical characteristics and the results of pulmonary function testing in patients with mild COPD and those without COPD are presented in Table 1. All patients had mild obstructive airway disease (mean FEV1 /FVC = 65.7 ± 2.7) with less than a 15 percent increase in pulmonary function following bronchodilator therapy. As noted, patients of each sex with mild COPD were slightly older than the corresponding controls (p<0.05). Physical attributes were similar for the sexes (p>0.05). Smoking
DISCUSSION
Exercise performance is decreased in patients with advanced COPD.1, 4, 5, 6, 13, 24, 25, 26, 27, 2, 29, 30, 31, 32 This decrease has been attributed to the degree of airflow limitation, alveolar ventilation-perfusion inequality, or chronic deconditioning,2, 33 yet little information is presently available describing physical work capacity in patients with mild nonreversible obstructive airway disease. Classically, a cardiovascular, rather than a ventilatory, limitation to exercise can be
CONCLUSION
We have demonstrated that physical work capacity is significantly reduced in patients with mild COPD, even though only mild airway obstruction is present. Although the reduced work capacity is related to the reduction in pulmonary function as assessed by the FEV1, there is an unexplained component which appears to be due to clinically signficant muscle deconditioning. Thus, a significant percentage of the reduction in and work performance may be reversible if progression of lung
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Supported in part by a grant from the Ray and Ipha Morrow Research Fund.
Manuscript received April 13; revision accepted July 6.