It is known that lactic anions and hydrogen ions (H⁺) produced during intense exercise are partly transported or diffused from muscle to blood resulting in the production of non-metabolic CO₂ through the bicarbonate buffering system. The purpose of the present study was to examine the reliability of the estimation of non-metabolic CO₂ output using respiratory gas analysis during incremental exercise. Six healthy subjects underwent an incremental pedaling exercise test accompanied by respiratory gas and arterial blood sampling. The rate of non-metabolic CO₂ output (VCO₂-NM) was calculated by subtracting projected metabolic VCO₂ from actual VCO₂ after CO₂ threshold (CT) . CT was determined using a modified V-Slope method. Bicarbonate (HCO₃^-), pH, CO₂ partial pressure and lactate concentration were measured from arterial blood samples using automatic analyzers. The kinetics of VCO₂-NM and HCO₂^- were compared throughout the exercise test. VCO₂-NM was significantly correlated with HCO₃^-decrease after CT (r=0.976, p<0.001) and the kinetics of VCO₂-NM and HCO₃^- decrease were similar during exercise. Furthermore, the amount of non-metabolic CO₂ output (NM-CO₂) calculated integrating VCO₂-NM above CT was significantly correlated with the difference in HCO₃^-between CT and exhaustion (r=0.929, p<0.01) and with the difference in arterial blood pH between rest and exhaustion (r=0.863, p<0.05) . However, NM-CO₂ was not significantly related to maximum ventilation (r=0.111, ns) . These results suggest that the estimation of non-metabolic CO₂ output during incremental exercise proposed in the present study is reliable. It was also suggested that the primary factor which influenced nonmetabolic CO₂ output during incremental exercise was the addition of H⁺ into blood and not hyperventilation.

Pulmonary rehabilitation is a common therapy for improving both exercise tolerance and quality of life (QoL) in patients with chronic obstructive pulmonary disease (COPD) . Although exercise is an important rehabilitation strategy, walking, treadmill use, bicycling and respiratory muscle training can be monotonous. A comprehensive exercise program that includes recreational activities may be a more effective means to decrease the occurrence of dyspnea during daily activities and improve QoL in patients with COPD. The purpose of this study was to investigate the effects of our exercise therapy, including recreational activities and respiratory muscle training, on dyspnea and health related QoL (HRQL) in COPD patients. Thirty-eight male patients with COPD were randomly assigned to a control (C) (70.1±6.4yr) (n=12) . pulmonary rehabilitation (PR) (70.3±8.3yr) (n= 16), or exercise (EX) (68.7±4.6yr) (n=10) group. The following evaluations were performed at baseline and at 8 weeks: (1) cycle ergometer test ; (2) 6-min walking distance : (3) physical fitness (4) pulmonary function ; (5) dyspnea : and (6) HRQoL (SF-36) . The C group showed no significant changes in physical fitness, pulmonary function, dyspnea, and HRQoL scores throughout the observation period. There was a significant (P<0.05) improvement in 6-min walking distance. physical fit-ness, maximum rnspiratory pressure (MIP), and HRQoL for the PR group. The EX group demons-trated a significant (P<0.05) improvement in physical fitness, maximum expiratory pressure (MEP), dyspnea, and HRQoL. Moreover, the degree of improvement in each variable was greater for EX than for PR. There were significant (P<0.05) correlations between MIP and FEV_1.0 (r=0.65), and between MEP and FEV_1.0 (r=0.43) . Based on these results, it appears that our comprehensive exercise program, including recreational activities and respiratory muscle training, improves physical fitness, pulmonary function, dyspnea, and quality of life in COPD patients.