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Thermoregulatory responses to heat stress and hypoxia (1104.19)
Author(s) -
Low David,
Bailey Thomas,
Jones Helen
Publication year - 2014
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.28.1_supplement.1104.19
Subject(s) - heart rate , thermoregulation , medicine , hypoxia (environmental) , blood pressure , chemistry , forearm , heat stress , endocrinology , anesthesia , oxygen , zoology , surgery , organic chemistry , biology
The aim of this study was to examine the thermoregulatory responses to combined heat stress and hypoxia. Seven healthy male subjects (22±3 yr, 80±11 kg, 180±7 cm), dressed in a water‐perfused suit, underwent moderate passive heating (Δ core temperature ~0.8 °C) on 2 separate occasions. In 1 trial subjects breathed normoxic air (NORMOXIA) and in the other subjects breathed balanced 13% O 2 air (HYPOXIA). Skin blood flow (SkBF; laser Doppler flowmetry), expressed as cutaneous vascular conductance (CVC; flux/blood pressure), and local sweat rate (SR; capacitance hygrometry) were recorded on the forearm. Core (Tcore; intestinal pill) and local skin temperatures (Tsk), as well as blood pressure (BP; automated sphygmomanometry and digital photoplethysmography), heart rate (HR; ECG) oxygen saturation (SpO 2 ; pulse oximetry) were also monitored. Tcore and mean body temperature (Tbody) thresholds for heat stress‐induced elevations in SkBF and SR, as well as the SkBF/SR: Tcore/Tbody slopes were calculated. At normothermic baseline HYPOXIA reduced SpO 2 (98±1 vs 90±6 %, P<0.01) and slightly elevated forearm SkBF (9±6 vs 13±12 % CVC max, P=0.10) and HR (67±10 vs 74±7 beats.min ‐1 , P<0.01). Tcore (37.0±0.3 vs 37.0±0.3 °C, P=0.30) was unchanged. During heating the forearm SkBF Tcore threshold (36.9±0.3 vs 37.0±0.2 °C, P=0.30) and the forearm SR Tbody threshold (36.7±0.3 vs 36.7±0.2 °C, P=0.90) were not different between trials. The forearm SkBF:Tcore slope was slightly reduced during HYPOXIA (1.04±1.17 vs 0.59±1.19 CVC units·°C, P=0.07) whereas the forearm SR:Tbody slope (0.17±0.09 vs 0.22±0.11 ml.cm 2 .min ‐1 ·°C, P=0.04) was increased by HYPOXIA. These results indicate that moderate hypoxia does not affect central thermoregulatory function but alters peripheral thermoregulatory effector function via blunted skin blood flow and accentuated sweating slopes possibly via baseline hypoxia‐induced cutaneous vasodilation. Grant Funding Source : European Commission FP7