Chest
Volume 103, Issue 3, March 1993, Pages 745-750
Journal home page for Chest

Clinical Investigations
Altered Exercise Gas Exchange and Cardiac Function in Patients with Mild Chronic Obstructive Pulmonary Disease

https://doi.org/10.1378/chest.103.3.745Get rights and content

Patients with advanced COPD have significantly reduced gas exchange and pulmonary function; however, little is known regarding physical work capacity and exercise gas exchange in patients with mild COPD. A total of 39 individuals (20 men and 19 women) without evidence of COPD (controls) and 51 individuals (29 men and 22 women) with mild COPD (FEV1 ≥60 percent of predicted; and ratio of FEV1 over forced vital capacity of 60 to 70 percent) were tested to determine resting pulmonary function and resting and peak exercise gas exchange in response to progressive maximal cycle ergometer testing. In general, those with mild COPD had similar smoking histories and essentially equivalent resting gas exchange studies as compared to the controls. Measured maximal oxygen consumption was less in both the male (p<0.003) and the female patients (p<0.001). This was due, in part, to a lower maximal ventilation in the men with obstruction (p<0.04), resulting from a significant reduction in tidal volume (p<0.05). Women presented with similar decreases in maximal ventilation (p<0.04) and maximal tidal volume (p<0.01), while no difference in maximal respiratory rate was noted in either group (p>0.05). Breathing reserve was 32 percent and 53 percent less for the male and female patients with obstruction than for controls. Maximal heart rates were less in the individuals with obstruction, where they reached 93 percent (p<0.02) and 96 percent (p<0.003) of the age- and sex-specific maximal heart rates for men and women as compared to 101 percent and 99 percent obtained in the controls. Achieved absolute work loads for men and women (in kilogram·meters per minute) were lower in the groups with obstruction (p<0.002 and 0.0003) as well. These results demonstrate that work capacity and gas exchange are significantly decreased in individuals with even mild COPD. The reduction in functional work capacity is secondary to a loss of pulmonary function, as well as chronic deconditioning. Increased dyspnea may be responsible for the premature cessation of exercise observed in patients with mild COPD. Thus, early intervention with exercise training may be warranted to counter the deleterious effects of deconditioning and declining pulmonary function in patients with mild COPD.

Section snippets

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 V˙o2 and work performance may be reversible if progression of lung

References (0)

Cited by (0)

Supported in part by a grant from the Ray and Ipha Morrow Research Fund.

Manuscript received April 13; revision accepted July 6.

View full text