Ventilatory Response at the Onset of Passive Exercise during Sleep in Man

Abstract

Although the mechanisms of exercise hyperpnea especially in phase I has been obscure, central and/or peripheral neurogenic drive is thought to be the cause for rapid increase in ventilation at the onset of voluntary exercise. Many previous investigations proved that passive exercise also produced a rapid increase in ventilation. These results may suggest that peripheral neurogenic components should be the main cause for exercise hyperpnea. However, this passive exercise was performed in an awake condition when the higher center is still active. It is considered that the higher center may influence the respiratory center in that case. So it is necessary to clarify the ventilatory response in passive exercise while the higher center is not active, for example, during sleep conditions. On the other hand, Wasserman et al.¹ proposed cardiodynamic hypotheses that ventilatory response is linked to changes in cardiac output. To confirm this theory especially in phase I, cardiac output must be measured correctly within a short time at the onset of exercise. Moreover, in a supine position, the hemodynamic response is rather different from the upright position, which affects the cardiac output. Thus, it is required to reveal the relationships between the ventilatory and cardiac response to passive exercise during sleep in a supine position. The purpose of this study is, therefore, to elucidate whether or not 1) an abrupt increase in ventilation would be observed at the onset of passive exercise during sleep in man and 2) whether these changes in ventilation are linked with concomitant changes in cardiac output in a supine position.