| Human cardiorespiratory and cerebrovascular function during severe passive hyperthermia: effects of mild hypohydration. | |
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MedLine Citation:
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PMID: 18483173 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The influence of severe passive heat stress and hypohydration (Hypo) on cardiorespiratory and cerebrovascular function is not known. We hypothesized that 1) heating-induced hypocapnia and peripheral redistribution of cardiac output (Q) would compromise blood flow velocity in the middle cerebral artery (MCAv) and cerebral oxygenation; 2) Hypo would exacerbate the hyperthermic-induced hypocapnia, further decreasing MCAv; and 3) heating would reduce MCAv-CO2 reactivity, thereby altering ventilation. Ten men, resting supine in a water-perfused suit, underwent progressive hyperthermia [0.5 degrees C increments in core (esophageal) temperature (TC) to +2 degrees C] while euhydrated (Euh) or Hypo by 1.5% body mass (attained previous evening). Time-control (i.e., non-heat stressed) data were obtained on six of these subjects. Cerebral oxygenation (near-infrared spectroscopy), MCAv, end-tidal carbon dioxide (PetCO2) and arterial blood pressure, Q (flow model), and brachial and carotid blood flows (CCA) were measured continuously each 0.5 degrees C change in TC. At each level, hypercapnia was achieved through 3-min administrations of 5% CO2, and hypocapnia was achieved with controlled hyperventilation. At baseline in Hypo, heart rate, MCAv and CCA were elevated (P<0.05 vs. Euh). MCAv-CO2 reactivity was unchanged in both groups at all TC levels. Independent of hydration, hyperthermic-induced hyperventilation caused a severe drop in PetCO2 (-8+/-1 mmHg/ degrees C), which was related to lower MCAv (-15+/-3%/ degrees C; R2=0.98; P<0.001). Elevations in Q were related to increases in brachial blood flow (R2=0.65; P<0.01) and reductions in MCAv (R2=0.70; P<0.01), reflecting peripheral distribution of Q. Cerebral oxygenation was maintained, presumably via enhanced O2-extraction or regional differences in cerebral perfusion. |
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Authors:
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Jui-Lin Fan; James D Cotter; Rebekah A I Lucas; Kate Thomas; Luke Wilson; Philip N Ainslie |
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Publication Detail:
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Type: Journal Article Date: 2008-05-15 |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 105 ISSN: 8750-7587 ISO Abbreviation: J. Appl. Physiol. Publication Date: 2008 Aug |
Date Detail:
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Created Date: 2008-08-05 Completed Date: 2008-10-10 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: United States |
Other Details:
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Languages: eng Pagination: 433-45 Citation Subset: IM |
Affiliation:
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Department of Physiology, Otago School of Medical Science, University of Otago, Dunedin, New Zealand. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Adult Body Temperature / physiology Carbon Dioxide / pharmacology Cerebrovascular Circulation / physiology* Dehydration / physiopathology* Esophagus / physiology Fever / physiopathology* Humans Hyperventilation / physiopathology Hypocapnia / metabolism Laser-Doppler Flowmetry Male Middle Cerebral Artery / physiopathology Oxygen Consumption / physiology Pulmonary Gas Exchange / physiology Regional Blood Flow / physiology Skin / blood supply Supine Position / physiology |
| Chemical | |
Reg. No./Substance:
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124-38-9/Carbon Dioxide |
| Comments/Corrections | |
Comment In:
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J Appl Physiol. 2008 Aug;105(2):400-1
[PMID:
18535132
]
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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