Autonomic Activity and Water Immersion

Principal Investigator: Blair Johnson, PhD

Funding Agency: Office of Naval Research

Abstract: The autonomic nervous system reflexively controls many physiological systems, including the cardiovascular and ventilatory systems. Water immersion causes fluid shifts within the body that increase central blood volume and intravascular fluid volume. These increases are thought to cause changes in autonomic activity, however it is not known if sympathetic nerve activity is reduced during water immersion. Because the autonomic nervous system controls the cardiovascular and ventilatory systems, it is imperative to understand changes in autonomic activity during water immersion in order to develop countermeasures to protect Navy and recreational divers from potentially adverse physiological responses to the environmental conditions that they are exposed to. This project will examine how changes in both water temperature and breathing gases influence autonomic activity during head out water immersion.