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Cerebrovascular sensitivity to reductions in carbon dioxide tension during heat stress does not predict tolerance to a simulate hemorrhage
Author(s) -
Lee Joshua F.,
Christmas Kevin M.,
Hurr Chansol,
Harrison Michelle L.,
Kim Kiyoung,
Brothers R. Matthew
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.1201.18
Subject(s) - hypocapnia , hyperventilation , anesthesia , carbon dioxide , hypercapnia , medicine , vasomotor , ventilation (architecture) , cerebral perfusion pressure , cardiology , cerebral blood flow , chemistry , acidosis , meteorology , organic chemistry , physics
Heat stress (HS) reduces arterial carbon dioxide (PaCO2), as indexed by end‐tidal carbon dioxide (PETCO2), which contributes to the decreased cerebral perfusion (MCAVmean) and cerebral vascular conductance (CVC) in this thermal condition. Intra‐individual variability in cerebrovascular sensitivity to this HS induced hypocapnia may a key factor underlying variability in tolerance to a simulated hemorrhage during HS. This study tested the hypothesis that cerebral sensitivity to reductions in PETCO2 during HS would be related to tolerance to a simulated hemorrhage challenge during this thermal condition. Cerebral vascular sensitivity to HS driven reductions in PETCO2 was indexed as the change in cerebral vascular conductance (CVC) during hypocanpia induced by 30 s of hyperventilation during HS. The difference in cumulative stress index (CSI Diff) between NT and HS conditions was used to assess the effect of HS on tolerance to the simulated hemorrhage challenge. CVCi was reduced by 1.4±0.8 cm/s/mmHg/Torr during hyperventilation induced hypocapnia. However, there was no relationship between CSI Diff and cerebral vasomotor sensitivity to reductions in PETCO2 during HS (R=0.12, P=0.69). These data suggest that individual differences in cerebral vasomotor sensitivity in the hypocapnic range do not predict tolerance to a simulated hemorrhage challenge in heat stressed individuals.