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The biochemical features of skeletal muscle and its contribution to exercise intolerance in patients with chronic obstructive pulmonary disease (COPD) is under active investigation. Near-infrared spectroscopy (NIRS) can non-invasively provide information on the oxidative capacity of muscle. To clarify whether oxygenation of peripheral muscle is one determinant of exercise tolerance, we simultaneously examined the oxygen uptake (V O 2off) kinetics and oxygen kinetics of peripheral skeletal muscle evaluated by NIRS during recovery from exercise in COPD patients. Fifteen patients with COPD and five normal control subjects performed a symptom-limited incremental exercise test. On the following day, all patients performed a constant work rate exercise test while being monitored using NIRS continuously for changes in concentration of oxygenated haemoglobin (HbO2) and during expired gas analysis. We found that the time constant of during recovery from constant work rate exercise (V O 2off) and the time constant of V O 2off during recovery (tau V O 2off) were significantly longer in COPD patients than in normal control subjects. was inversely correlated with absolute values of forced expiratory volume in 1 s (FEV1.0) and FEV1.0 (% predicted). However, no significant correlation was found between and FVC (forced vital capacity), FEV1.0/FVC, or diffusing capacity of the lung for CO (DLCO). Moreover, was inversely correlated with maximal V O 2off and maximal work rate. In contrast, exhibited a significant positive correlation with tau V O 2off. These results indicate that V O 2off kinetics during recovery is related to re-oxygenation of peripheral skeletal muscle evaluated by NIRS in patients with COPD. Therefore, NIRS may be a useful tool to estimate the impairment of cardiopulmonary responses and re-oxygenation of peripheral skeletal muscle during the immediate recovery phase after exercise in COPD patients.
Okamoto et al. (Mon,) studied this question.