An assessment of hypercapnia-induced elevations in regional cerebral perfusion during combined orthostatic and heat stresses

Manabu Shibasaki, Kohei Sato, Ai Hirasawa, Tomoko Sadamoto, Craig G. Crandall, Shigehiko Ogoh

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

We investigated that the effects of hypercapnia-induced elevations in cerebral perfusion during a heat stress on global cerebrovascular responses to an orthostatic challenge. Seven volunteers completed a progressive lower-body negative pressure (LBNP) challenge to presyncope during heat stress, with or without breathing a hypercapnic gas mixture. Administration of the hypercapnic gas mixture increased the partial pressure of end-tidal CO2 greater than pre-heat stress alone, and increased both internal carotid artery (ICA) and vertebral artery (VA) blood flows (P < 0.05). During LBNP, both ICA and VA blood flows with the hypercapnic gas mixture remained elevated relative to the control trial (P < 0.05). However, at the end of LBNP due to pre-syncopal symptoms, both ICA and VA blood flows decreased to similar levels between trials. These findings suggest that hypercapnia-induced cerebral vasodilation is insufficient to maintain cerebral perfusion at the end of LBNP due to pre-syncope in either the anterior or posterior vascular beds.

Original languageEnglish (US)
Article number25
JournalJournal of Physiological Sciences
Volume70
Issue number1
DOIs
StatePublished - May 4 2020
Externally publishedYes

Keywords

  • CO reactivity
  • Cerebral blood flow
  • Hyperthermia
  • Orthostatic tolerance
  • Presyncope

ASJC Scopus subject areas

  • Physiology

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