Chest
Clinical InvestigationsMetabolic Acidosis during Exercise in Patients with Chronic Obstructive Pulmonary Disease: Use of the V-slope Method for Anaerobic Threshold Determination
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MATERIAL AND METHODS
A group of 22 patients with moderately severe to severe COPD was studied. For comparison, a group of 56 subjects was identified from a previous study of the cardiopulmonary responses of normal men during cycle incremental exercise.6 These subjects had no evidence of heart, lung, peripheral vascular, or musculoskeletal disease and were not anemic. As previously reported, this group included men with hypertension in whom an elevated blood pressure did not by itself limit exercise capacity,
Normal Subjects
The mean values for age, size, and pulmonary function of the 56 normal subjects are shown in Table 1. As described above, all had normal pulmonary function. Exercise capacity expressed as maximum oxygen uptake as percent predicted value6 and AT as determined by both the modified V-slope method and from changes in standard bicarbonate are shown for individual subjects in Table 2. In 43 normal subjects, the AT could be determined by both methods; in the other 13, an AT could be clearly selected
DISCUSSION
During an incremental exercise test, about two thirds of our patients with chronic airflow obstruction developed metabolic acidosis. This finding may be surprising in view of the understanding that many of these patients with COPD are limited in their exercise capacity by exertional dyspnea, presumably due to reduced ventilatory capacity. In fact, it may have been thought that these patients would have such low exercise capacity that they would be unable to develop metabolic acidosis during
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Supported by Public Health Service grant HL-11907.
Manuscript received January 12; revision accepted April 26.