Ventilatory and cardiovascular responses to hypoxic and hyperoxic static handgrip exercise in man

The purpose of this study was to evaluate the ventilatory and cardiovascular responses to static handgrip exercise at different levels of arterial chemoreceptor activation. The study was done on 10 healthy subjects. They performed handgrip of 50% of maximal voluntary contraction on a background of either hypoxia (PE'O2 approximately 47 mm Hg) or hyperoxia (PE'O2 approximately 216 mm Hg), i.e., enhanced or suppressed chemoreceptor activity. The subjects were able to sustain the handgrip for 50-60 sec, during which time no steady-state responses were attainable. Minute ventilation (VI), cardiac output (Q), heart rate (HR), and a number of other variables were recorded. Handgrip exercise resulted in a rapid initial VI rise followed by a subsequent slow increase. Hyperoxia diminished the VI response over the exercise range. The ventilatory response was associated with an HR acceleration, increased arterial pressure and peripheral vascular resistance. No appreciable changes in Q were noted, nor was there any particular relationship between ventilatory and circulatory changes. These results provide no support for the Q mediated ventilatory stimulus during static handgrip exercise in man. It is concluded that the ventilatory and cardiovascular responses are of independent nature.