Physiological Response to Moderate Exercise Workloads in a Pulmonary Rehabilitation Program in Patients With Airflow Obstruction
Patients with COPD are limited in their exercise tolerance by dyspnea, peripheral muscle weakness, and lactic acidosis at low levels of exercise. The factors that contribute to dyspnea in these patients are related to a combination of high ventilatory requirement coupled with low ventilatory capacity. There is now a considerable body of evidence that rehabilitative exercise strategies in patients with COPD result in significant improvement in measures of exercise tolerance in contrast to those of pulmonary function. For example, Casaburi and colleagues reported that high-intensity exercise training performed 5 days per week for 8 weeks in 11 patients with moderate airflow limitation (mean FEV1, 56% predicted) lowered the ventilatory requirement at a given level of exercise, thus increasing exercise tolerance. In contrast, a concurrent group of eight patients who exercised at a lower intensity failed to achieve comparable responses. The possibility of inducing training effects in patients with more severe COPD was originally investigated by Maltais et al, who exercised 11 patients (mean FEV1, 36% predicted) three times a week for 12 weeks at moderate intensity. Again, this resulted in a reduced exercise ventilatory requirement accompanied by improved exercise tolerance. comments
These results were recently confirmed by Casaburi et al, who applied a training program of rigorous exercise three times a week for 6 weeks in 25 patients with severe airflow limitation (mean FEV1, 36% predicted), While the above studies provide substantial evidence of physiologic training effects over a wide objective spectrum of airflow limitation, these were achieved in small groups of patients. Recent studies have clarified previous uncertainty that twice-weekly pulmonary rehabilitation sessions were adequate to produce significant gains in exercise performance, as assessed simplistically by walking tests. However, the possibility of inducing training effects on measured objective physiologic exercise responses by the implementation of an exercise program featuring fewer than three sessions per week remains uncertain. In view of the cost and resource effort involved in conducting a rehabilitation program, we were particularly interested in designing and implementing an exercise regimen of moderate frequency and intensity that could be sufficient to induce measurable physiologic exercise responses and improvements in exercise tolerance. We therefore undertook a trial of pulmonary rehabilitation in 60 patients with a wide spectrum of airflow limitation who participated in a 12-week outpatient program that featured twice-weekly moderately intense exercise training sessions. While our primary outcome measure was the evaluation of physiologic training effects in these patients, by comparison we also report data in a smaller control group of 15 patients who did not participate in any training sessions.
Category: Airflow Obstruction
Tags: COPD, exercise training, pulmonary rehabilitation