Skeletal muscle ergoreflex overactivity is not related to exercise ventilatory inefficiency in non-hypoxaemic patients with COPD.
Increased ventilatory response to the metabolic demand ("ventilatory inefficiency") is commonly found during dynamic exercise in patients with chronic obstructive pulmonary disease (COPD). However, the role of enhanced muscle ergoreflex activity on this phenomenon is yet unknown. Ten non-hypoxaemic patients with varying degrees of disease severity (median and range of post-bronchodilator FEV(1) = 37.5 (27 to 70%) predicted) and 7 age- and gender-matched controls were studied. Subjects were submitted to wrist flexion tests to the limit of tolerance (Tlim) with and without post-exercise regional circulatory occlusion (PE-RCO) for 3 min. The muscle ergoreflex activity was quantified as the difference in ventilation between PE-RCO and control recovery periods corrected for the resting values (ergoreflex Delta). In addition, the area under the ventilatory curve in the recovery period was calculated in both conditions. We found that Tlim and the physiological stress associated with localized exercise did not differ between patients and controls. However, patients had increased ventilatory response to a given metabolic demand (VCO(2)), either at rest or during exercise (P < 0.05). There were no significant differences in ergoreflex Delta in patients and controls (-2.2 to 2.4 (0.2) vs. -0.6 to 1.8 (0.3) l/min, respectively). In addition, the area under the ventilatory curve in the recovery period did not differ between control and PE-RCO tests in patients and healthy subjects (P > 0.05). We conclude that increased muscle ergoreflex activity did not contribute to an excessive ventilatory response to exercise in patients with COPD-at least in non-hypoxaemic and non-cachetic subjects.
Nakamoto
Fernanda Patti
FP
Respiratory and Exercise Physiology Laboratory (LAFIREX), Neurophysiology and Exercise Physiology Division, Department of Physiology, Federal University of Sao Paulo (UNIFESP), Sao Paulo, SP, Brazil.
Neder
J Alberto
JA
Maia
Joyce
J
Andrade
Marília S
MS
Silva
Antônio Carlos
AC
D000368:Aged; D015308:Anaerobic Threshold / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood; D016552:Ergometry; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010100:Oxygen / Q000097:blood; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012018:Reflex / Q000502:physiology*; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology*; D013990:Tidal Volume / Q000502:physiology; D014953:Wrist / Q000502:physiology
D002245:Carbon Dioxide; D010100:Oxygen