title: Early cardiovascular adaptation to zero gravity simulated by head-down tilt.
abstract: The early cardiovascular adaptation to zero gravity, simulated by head-down tilt at 5 degrees, was studied in a series of 10 normal young men. The validity of the model was confirmed by comparing the results with data from Apollo and Skylab flights. Tilt produced a significant central fluid shift with a transient increase in central venous pressure, later followed by an increase in left ventricular size without changes in cardiac output, arterial pressure, or contractile state. The hemodynamic changes were transient with a nearly complete return to the control state within 6 hr. The adaptation included a diuresis and a decrease in blood volume, associated with ADH, renin and aldosterone inhibition.
authors.affiliation: Department of Internal Medicine, Southwestern Medical School, University of Texas Health Science Center, Dallas 75235, USA.
authors.forename: C G
authors.initials: CG
authors.lastname: Blomqvist
authors.forename: J V
authors.initials: JV
authors.lastname: Nixon
authors.forename: R L
authors.initials: RL
authors.lastname: Johnson
authors.forename: J H
authors.initials: JH
authors.lastname: Mitchell
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000337:Aerospace Medicine; D000450:Aldosterone / Q000097:blood / Q000378:metabolism; D002320:Cardiovascular Physiological Phenomena; D004231:Diuresis; D005069:Evaluation Studies as Topic; D015444:Exercise / Q000502:physiology; D018495:Fluid Shifts / Q000502:physiology*; D005440:Fluid Therapy; D018475:Head-Down Tilt / Q000502:physiology*; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D010953:Plasma Volume / Q000502:physiology; D012083:Renin / Q000097:blood / Q000378:metabolism; D014667:Vasopressins / Q000097:blood / Q000378:metabolism; D018474:Weightlessness Simulation / Q000379:methods*
chemical_list: D014667:Vasopressins; D000450:Aldosterone; D012083:Renin