Effects of spaceflight on human calf hemodynamics

• Published in: Journal of applied physiology (1985) Vol. 90; no. 4; pp. 1552 - 1558
• Main Authors: Watenpaugh, Donald E, Buckey, Jay C, Lane, Lynda D, Gaffney, F. Andrew, Levine, Benjamin D, Moore, Willie E, Wright, Sheryl J, Blomqvist, C. Gunnar
• Format: Journal Article
• Language: English
• Published: Legacy CDMS Am Physiological Soc 01.04.2001; American Physiological Society
• Subjects: Adult; Biological and medical sciences; Blood Pressure - physiology; Blood vessels; Effects; Female; Gravity; Heart Rate - physiology; Hemodynamics - physiology; Humans; Leg - blood supply; Legs; Life Sciences (General); Male; Medical sciences; Metabolic diseases; Middle Aged; Obesity; Regional Blood Flow - physiology; Space Flight; Space life sciences; Supine Position - physiology; Vascular Resistance - physiology; Weightlessness; Sts-58 Shuttle Project; Nasa Discipline Cardiopulmonary; Nasa Experiment Number 178294 2/2; Nasa Experiment Number 178294 1/2; Sts-40 Shuttle Project; Non-Nasa Center; Manned; Short Duration; Flight Experiment; Human; Lower limb; Environmental factor; Weightlessness; Space flight; Compliance(volume pressure); Resistance; Vascular resistance; Blood vessel; Calf(anatomy); Circulatory system; Hemodynamics; Orthostatic tolerance; Microgravity; Adaptation; NASA Discipline Cardiopulmonary; NASA Experiment Number 178294 1/2; NASA Experiment Number 178294 2/2; Non-NASA Center
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.2001.90.4.1552

Departments of Physiology and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75235 Chronic microgravity may modify adaptations of the leg circulation to gravitational pressures. We measured resting calf compliance and blood flow with venous occlusion plethysmography, and arterial blood pressure with sphygmomanometry, in seven subjects before, during, and after spaceflight. Calf vascular resistance equaled mean arterial pressure divided by calf flow. Compliance equaled the slope of the calf volume change and venous occlusion pressure relationship for thigh cuff pressures of 20, 40, 60, and 80 mmHg held for 1, 2, 3, and 4 min, respectively, with 1-min breaks between occlusions. Calf blood flow decreased 41% in microgravity (to 1.15 ± 0.16 ml · 100 ml 1 · min 1 ) relative to 1-G supine conditions (1.94 ± 0.19 ml · 100 ml 1 · min 1 , P  = 0.01), and arterial pressure tended to increase ( P  = 0.05), such that calf vascular resistance doubled in microgravity (preflight: 43 ± 4 units; in-flight: 83 ± 13 units; P  < 0.001) yet returned to preflight levels after flight. Calf compliance remained unchanged in microgravity but tended to increase during the first week postflight ( P  > 0.2). Calf vasoconstriction in microgravity qualitatively agrees with the "upright set-point" hypothesis: the circulation seeks conditions approximating upright posture on Earth. No calf hemodynamic result exhibited obvious mechanistic implications for postflight orthostatic intolerance. weightlessness; gravity; leg; vascular resistance; blood flow; venous compliance