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Dynamic cerebral autoregulation during passive heat stress
Author(s) -
Low David A,
Wingo Jonathan E.,
Keller David M.,
Davis Scott L.,
Zhang Rong,
Crandall Craig G
Publication year - 2008
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.22.1_supplement.956.8
Subject(s) - autoregulation , chemistry , blood pressure , medicine , middle cerebral artery , cerebral autoregulation , analytical chemistry (journal) , chromatography , ischemia
This study tested the hypothesis that passive heating impairs cerebral autoregulation. Transfer function analysis of resting arterial blood pressure (BP) and middle cerebral artery blood velocity (MCAV mean ) were conducted on 9 healthy subjects, dressed in a water‐perfused suit, under normothermic (NT) and passive heat stress (HS, Δ core temperature 1.1 ± 0.2 °C, P<0.001) conditions. Passive heating reduced MCAV mean (8 ± 8 cm•s −1 , P=0.01), whilst mean arterial BP was maintained (2 ± 5 mm Hg, P=0.36). In the very low frequency range (<0.07 Hz) coherence was lower during HS compared to NT conditions (0.26 ± 0.10 vs 0.57 ± 0.13, respectively, P<0.001). Coherence was >0.5 and similar between NT and HS in the low (0.07–0.20 Hz, 0.64 ± 0.19 vs 0.59 ± 0.10, respectively, P=0.40) and high (0.20–0.35 Hz, 0.63 ± 0.19 vs 0.72 ± 0.14, respectively, P=0.12) frequency ranges. Phase was higher during HS in the low frequency range (NT: 0.55 ± 0.31 vs HS: 0.82 ± 0.17°, P=0.01), whereas it was unchanged by HS in the high frequency range (NT: −0.10 ± 0.20 vs HS: 0.12 ± 0.71°, P=0.14). Transfer gain was higher during HS in the low (NT: 1.53 ± 0.41 vs HS: 1.73 ± 0.38 cm•s −1 •mmHg −1 , P=0.03) and high (NT: 1.55 ± 0.55 vs HS: 2.06 ± 0.37 cm•s −1 •mmHg −1 , P=0.03) frequency ranges. Higher transfer function estimates of gain suggest that dynamic cerebral autoregulation is impaired during HS. Supported by NIH Grant HL‐61388 & HL‐84072