Skin cooling maintains cerebral blood flow velocity and orthostatic tolerance during tilting in heated humans

• Published in: Journal of applied physiology (1985) Vol. 93; no. 1; pp. 85 - 91
• Main Authors: Wilson, Thad E, Cui, Jian, Zhang, Rong, Witkowski, Sarah, Crandall, Craig G
• Format: Journal Article
• Language: English
• Published: Legacy CDMS Am Physiological Soc 01.07.2002; American Physiological Society
• Subjects: Adult; Aerospace Medicine; Biological and medical sciences; Blood Pressure - physiology; Blood vessels; Body Temperature - physiology; Cardiac Output - physiology; Cerebral circulation. Blood-brain barrier. Choroid plexus. Cerebrospinal fluid. Circumventricular organ. Meninges; Cerebrovascular Circulation - physiology; Cooling; Female; Fundamental and applied biological sciences. Psychology; Galvanic Skin Response; Heart Rate - physiology; Heat; Hemodynamics - physiology; Hot Temperature; Humans; Hypotension, Orthostatic - physiopathology; Laser-Doppler Flowmetry; Male; Posture - physiology; Skin; Skin Physiological Phenomena; Skin Temperature - physiology; Sweating - physiology; Ultrasonography, Doppler, Transcranial; Vascular Resistance - physiology; Vertebrates: nervous system and sense organs; Heart Rate/physiology; Support, U.s. Gov't, P.h.s; Skin Temperature/physiology; Non-Nasa Center; Male; Hemodynamic Processes/physiology; Posture/physiology; Sweating/physiology; Galvanic Skin Response; Ultrasonography, Doppler, Transcranial; Vascular Resistance/physiology; Cerebrovascular Circulation/physiology; Female; Adult; Human; Support, U.s. Gov't, Non-P.h.s; Blood Pressure/physiology; Nasa Discipline Cardiopulmonary; Clinical Trial; Skin Physiology; Body Temperature/physiology; Laser-Doppler Flowmetry; Hypotension, Orthostatic/physiopathology; Heat; Cardiac Output/physiology; Regional blood flow; Temperature; Cooling; Central nervous system; Environmental factor; Circulatory velocity; Stress; Skin; Hemodynamics; Orthostatic tolerance; Brain (vertebrata); NASA Discipline Cardiopulmonary; Non-NASA Center
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.01043.2001

1  Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas 75321; and 2  Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75235 Orthostatic tolerance is reduced in the heat-stressed human. The purpose of this project was to identify whether skin-surface cooling improves orthostatic tolerance. Nine subjects were exposed to 10 min of 60° head-up tilting in each of four conditions: normothermia (NT-tilt), heat stress (HT-tilt), normothermia plus skin-surface cooling 1 min before and throughout tilting (NT-tilt cool ), and heat stress plus skin-surface cooling 1 min before and throughout tilting (HT-tilt cool ). Heating and cooling were accomplished by perfusing 46 and 15°C water, respectively, though a tube-lined suit worn by each subject. During HT-tilt, four of nine subjects developed presyncopal symptoms resulting in the termination of the tilt test. In contrast, no subject experienced presyncopal symptoms during NT-tilt, NT-tilt cool , or HT-tilt cool . During the HT-tilt procedure, mean arterial blood pressure (MAP) and cerebral blood flow velocity (CBFV) decreased. However, during HT-tilt cool , MAP, total peripheral resistance, and CBFV were significantly greater relative to HT-tilt (all P  < 0.01). No differences were observed in calculated cerebral vascular resistance between the four conditions. These data suggest that skin-surface cooling prevents the fall in CBFV during upright tilting and improves orthostatic tolerance, presumably via maintenance of MAP. Hence, skin-surface cooling may be a potent countermeasure to protect against orthostatic intolerance observed in heat-stressed humans. hyperthermia; heat stress; syncope; transcranial Doppler