Abstract
To clarify the relationship between ventilation efficiency and autonomic nervous activity under microgravity condition induced by parabolic flight, ventilation efficiency, the ratio of abdominal-to-thoracic motion (Vabd/Vrib), the duration of expiratory phase of respiration (TE/TTot) and sympathetic nervous activity were measured in human subjects. Microgravity resulted in a reduction of the ventilation efficiency and increase of sympathetic nervous activity. Furthermore, Vabd/Vrib increased and TE/TTot decreased during microgravity. In addition, we observed using a video-recorder that subject’s trunk was extended during microgravity exposure. These results suggest that the change of subject’s posture might decrease abdominal motion and expiratory phase, and induce increase in sympathetic nervous activity. Thus, autonomic nervous activity does not always play key role to regulate ventilation efficiency in case of exposure to microgravity. Moreover, it is suggested that subject’s posture affects autonomic nervous activity under microgravity condition.
