Chest
Volume 128, Issue 4, October 2005, Pages 2025-2034
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Clinical Investigations
Exercise Training Decreases Ventilatory Requirements and Exercise-Induced Hyperinflation at Submaximal Intensities in Patients With COPD

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Study objectives

We hypothesized that endurance exercise training would reduce the degree of hyperinflation for a given level of exercise and thereby improve submaximal exercise endurance.

Methods

Twenty-four patients with COPD (mean FEV1, 36.4 ± 8.5% of predicted [± SD]) undertook a high-intensity cycle ergometer exercise training program for 45 min, three times a week for 7 weeks. Before and after training, the patients performed both an incremental exercise test to maximum and a constant work rate (CWR) test on a cycle ergometer at 75% of the peak work rate obtained in the pretraining incremental test. Ventilatory variables were measured breath-by-breath, and inspiratory capacity (IC) was measured every 2 min to assess changes in end-expiratory lung volume.

Results

After training, the increase in peak oxygen uptake was not statistically significant; however, the peak work rate increased by 12.9 ± 10.3 W (p < 0.01). For the CWR test performed at the same work rate both before and after training, ventilation and breathing frequency (f) were lower after training (average, 1.97 L/min and 3.2 breaths/min, respectively; p < 0.01) and IC was greater (by an average of 133 mL, p < 0.05), signifying decreased hyperinflation. The increase in IC at the point of termination in the shortest CWR test for each individual (defined as isotime) correlated well with both the decreased f (r = 0.63, p = 0.001) and with the increase in CWR exercise endurance (average, 13.1 min, r = 0.46, p = 0.023).

Conclusions

Exercise training in patients with severe COPD dramatically improves submaximal exercise endurance. Decreased dynamic hyperinflation may, in part, mediate the improvement in exercise endurance by delaying the attainment of a critically high inspiratory lung volume.

Section snippets

Subjects

The 24 subjects participating in this study are a subgroup of the subjects previously described by Emtner et al.10 This subgroup had had satisfactory EELV assessments that allowed us to focus, for what we believe is the first time, on the specific effects of endurance exercise training on EELV and its potential contribution to exercise intolerance in patients with COPD. These patients did not differ in any of their pulmonary function data from the rest of the original population. The original

Results

Twenty-four subjects were involved in this study. Six of the 30 subjects in the report of Emtner et al10 were excluded because adequate IC measurements were not obtained. As there was no significant difference between the groups (ie, those receiving supplemental oxygen or air during the training) in terms of baseline pulmonary function, exercise tolerance, or ventilatory response, the groups were combined for further analysis (Table 1), although we utilized different symbols for the groups in

Discussion

In this article, we demonstrate that after exercise training, there is a marked increase in constant work endurance (almost 300% longer than pretraining; Table 2). This is associated with reduced dynamic hyperinflation during CWR exercise in the majority of subjects. Further, the reduction in dynamic hyperinflation was shown to be correlated with the reduced f. This is not surprising, as an acute effect of oxygen inhalation has been shown to reduce f and also to reduce dynamic hyperinflation.6

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