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Cerebral blood flow velocity during passive heat stress in man: influence of stroke volume
Author(s) -
Nelson Michael D,
Haykowsky Mark J,
Stickland Michael K,
Smith Kurt J,
Willie Chris K,
AltamiranoDiaz Luis A,
Petersen Stewart R,
Rieger Mathew G,
Ainslie Philip N
Publication year - 2011
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.25.1_supplement.1053.1
Subject(s) - hypocapnia , cerebral blood flow , medicine , vasoconstriction , supine position , heat stress , cardiology , anesthesia , transcranial doppler , stroke volume , stroke (engine) , heart rate , blood pressure , atmospheric sciences , mechanical engineering , acidosis , engineering , hypercapnia , geology
Cerebral blood flow velocity is reduced during heat stress with 50% of this reduction due to hyperventilatory‐induced hypocapnia and subsequent cerebral vasoconstriction; it is unknown what other factors may also be important. We tested the hypothesis that stroke volume (SV) plays an important role in maintaining cerebral perfusion during heat stress. Cerebral blood flow velocity (CBFV; transcranial Doppler) and SV (2D‐echocardiography) were measured under conditions of normothermia and passive heat stress while supine and during 30° head‐down tilt (HDT) and 30° head‐up tilt (HUT). Core temperature was elevated ~0.8°C via a water perfused tube‐lined suit. Relative to baseline, SV decreased by 8.5% (P = 0.07) with passive heating, while CBFV was significantly reduced (−6.4%). HDT heat stress increased SV above supine heat stress (11.3%) and CBFV was returned to normothermic baseline levels. HUT heat stress reduced SV from baseline (−14.0%, P < 0.05) while CBFV was reduced (18.6%, P < 0.05). The changes in SV were related to changes in CBFV (r 2 = 0.83). These findings indicate that SV plays an important role in regulating CBFV during passive heat stress.