It has long been recognized that at the onset of a dynamic muscular exercise the ventilatory and the circulatory (blood flow) responses appear to be matched, thereby maintaining arterial blood gas homeostasis. Such a coupling has recently been suggested to rely upon ventilatory reflex triggered by mechanoreceptors encoding changes in muscle blood flow or, more likely, blood volume. The aim of this study was to investigate whether patients with severe peripheral blood flow limitation to the lower extremities have a normal ventilatory response during a light intensity exercise. The ventilatory and gas exchange temporal response characteristics were studied during a 6 min walking test in seven patients with severe ischemic peripheral vascular disease and in six normal age-matched subjects. The magnitude of the overall ventilatory and V̇(O2) increment at the end of the tests was similar in both groups. However, in contrast to the control subjects, who presented an almost rectangular response, the patients had a considerably slowed response dynamics (t50 = 33 ± 4 vs. 9 ± 3 sec for V̇(O2) and 37 ± 5 vs. 10 ± 8 sec for V̇E) with a dramatic reduction in the magnitude of the initial 20 sec of the responses. Although the slow V̇(O2) dynamics in patients presumably reflected the impeded perfusion of the working muscles, the accompanying sluggishness of the V̇(E course) implies that either muscular ischemia actually inhibits ventilatory response to exercise or, more likely, that this response is strongly linked to the magnitude of the hyperemia in the exercising muscles.
All Science Journal Classification (ASJC) codes
- Pulmonary and Respiratory Medicine