Effect of whole body heat stress on peripheral vasoconstriction during leg dependency

R. Matthew Brothers, Jonathan E. Wingo, Kimberly A. Hubing, Juan Del Coso, Craig G. Crandall

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

The venoarteriolar response (VAR) increases vascular resistance upon increases in venous transmural pressure in cutaneous, subcutaneous, and muscle vascular beds. During orthostasis, it has been proposed that up to 45% of the increase in systemic vascular tone is due to VAR-related local mechanism(s). The objective of this project was to test the hypothesis that heat stress attenuates VAR-mediated cutaneous and whole leg vasoconstriction. During normothermic conditions, measurements of cutaneous blood flow (laser-Doppler flowmetry) and femoral artery blood flow (Doppler ultrasound) were obtained from both legs during supine and leg-dependent conditions. These measurements were repeated following a whole body heat stress (increase in internal temperature of 1.4 ± 0.2°C). Before leg dependency, cutaneous (CVC) and femoral vascular conductances (FVC) were significantly elevated in both legs during heat stress relative to normothermia (P < 0.001). During leg dependency the absolute decrease in CVC was attenuated during heat stress (P < 0.01) while the absolute decrease in FVC was unaffected (P = 0.90). When CVC and FVC data were analyzed as a relative change from their respective baseline values, heat stress significantly attenuated the magnitude of vasoconstriction due to leg dependency in the cutaneous and femoral circulations (P < 0.001 for both variables). These data suggest that an attenuated local vasoconstriction, evoked via the venoarteriolar response, may contribute to reduced blood pressure control and thus reduced orthostatic tolerance that occurs in heat-stressed individuals.

Original languageEnglish (US)
Pages (from-to)1704-1709
Number of pages6
JournalJournal of applied physiology
Volume107
Issue number6
DOIs
StatePublished - Dec 2009

Keywords

  • Blood pressure
  • Hyperthermia
  • Orthostatic tolerance

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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