Metabolic Acidosis during Exercise in Patients with Chronic Obstructive Pulmonary Disease: 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 pbm a previous study of the cardiopulmonary responses of normal filen during cycle incremental exercise. These subjects had no Evidence of heart, lung, peripheral vascular or musculoskeletal disease and were not anemic. As previously reported, this group iticluded men with hypertension in whom an elevated blood pressure did not by itself limit exercise capacity cigarette smokers, ahd obese individuals; all subjects were referred as part of an evaluation for asbestos-related lung disease, but none, in this study hfed evidence of asbestos*related parenchymal lung disease.

Normal values for pulmonary function included those ofKnudson et al for vital capacity and FEV4, Goldman and Becldake for total lting capacity, and Cotes for diffusing capacity for carbon monoxide (Dsb). Normal values for maximum exercise Vo* were those of ftansen et al. All subjects exercised on an electrically braked cycle ergometer (Quinton or Lanooy). During exercise, they exhaled into a mouthpiece connected to a breathing valve. Expired gas flow was measured using a pneumotachograph (Hewlett-Packard); continuously collected samples of expired gas at the mouthpiece were directed to a respiratory mass spectrometer (Pferidn-Elmer) for determination of expired O* and CO*. The measurements made by the pneumotachograph and mass spectrometer were sent to a microcomputer system designed for breath-by-breath determination of Ve, Ot uptake Vo*), CO* output (VcOj), and gas exchange ratio (R) as previously described.10 Electrocardiograms were obtained for monitoring purposes and for determination of maximum exercise heart rate. All subjects in both groups had a brachial artery catheter placed percutaneously using the Seldinger technique. Arterial blood samples were drawn approximately every other minute for determination of Po2, Pco2, pH, bicarbonate, and standard bicarbonate.
All subjects underwent a 1-min incremental cycle exercise protocol during which the work rate on the cycle was increased in equal increments ranging between 5 and 30 W each minute, depending on the subjects* fitness. The work rate increment was selected to reach the estimated maximum work rate in about 8 to 10 min. The maximum Ve and Vo* were selected as the highest values reached during the incremental exercise period.

Category: Pulmonary Disease

Tags: lung disease, metabolic acidosis, Pulmonary function