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

Thad E. Wilson, Jian Cui, Rong Zhang, Sarah Witkowski, Craig G. Crandall

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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-tiltcool), and heat stress plus skin-surface cooling 1 min before and throughout tilting (HT-tiltcool). 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-tiltcool, or HT-tiltcool. During the HT-tilt procedure, mean arterial blood pressure (MAP) and cerebral blood flow velocity (CBFV) decreased. However, during HT-tiltcool, 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.

Original languageEnglish (US)
Pages (from-to)85-91
Number of pages7
JournalJournal of applied physiology
Issue number1
StatePublished - Jan 1 2002



  • Heat stress
  • Hyperthermia
  • Syncope
  • Transcranial Doppler

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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