Department of Human Physiology, University of Oregon, Eugene, Oregon 97403-1240, USA.
J Appl Physiol (1985). 2010 Apr;108(4):788-92. doi: 10.1152/japplphysiol.01221.2009. Epub 2010 Feb 18.
Hypoxia decreases core body temperature in animals and humans during cold exposure. In addition, hypoxia increases skin blood flow in thermoneutral conditions, but the impact of hypoxic vasodilation on vasoconstriction during cold exposure is unknown. In this study, skin blood flow was assessed using laser-Doppler flowmetry, and cutaneous vascular conductance (CVC) was calculated as red blood cell flux/mean arterial pressure and normalized to baseline (n = 7). Subjects were exposed to four different conditions in the steady state (normoxia and poikilocapnic, isocapnic, and hypercapnic hypoxia) and were cooled for 10 min using a water-perfused suit in each condition. CVC increased during all three hypoxic exposures (all P < 0.05 vs. baseline), and the magnitude of these steady-state responses was not affected by changes in end-tidal CO(2) levels. During poikilocapnic and hypercapnic hypoxia, cold exposure reduced CVC to the same levels observed during normoxic cooling (P > 0.05 vs. normoxia), whereas CVC remained elevated throughout cold exposure during isocapnic hypoxia (P < 0.05 vs. normoxia). The magnitude of vasoconstriction during cold stress was similar in all conditions (P > 0.05). Thus the magnitude of cutaneous vasodilation during steady-state hypoxia is not affected by CO(2) responses. In addition, the magnitude of reflex vasoconstriction is not altered by hypoxia, such that the upward shift in skin blood flow (hypoxic vasodilation) is maintained during whole body cooling.
在暴露于寒冷环境中时，缺氧会降低动物和人类的核心体温。此外，在体温中性条件下，缺氧会增加皮肤血流量，但缺氧扩张对寒冷暴露期间血管收缩的影响尚不清楚。在这项研究中，使用激光多普勒流量仪评估皮肤血流量，并将皮肤血管传导率（CVC）计算为红细胞通量/平均动脉压，并与基线归一化（n = 7）。在稳定状态下，受试者暴露于四种不同的条件（常氧和变温性、等碳酸血症和高碳酸血症缺氧），并在每种条件下使用水灌注服冷却 10 分钟。在所有三种缺氧暴露期间，CVC 均增加（均 P < 0.05 与基线相比），这些稳态反应的幅度不受终末 CO2 水平变化的影响。在变温性和高碳酸血症缺氧期间，寒冷暴露将 CVC 降低至与常氧冷却期间观察到的相同水平（P > 0.05 与常氧相比），而在等碳酸血症缺氧期间，CVC 在整个寒冷暴露期间保持升高（P < 0.05 与常氧相比）。在所有条件下，冷应激期间的血管收缩幅度相似（P > 0.05）。因此，稳态缺氧期间皮肤血管扩张的幅度不受 CO2 反应的影响。此外，反射性血管收缩的幅度不受缺氧的影响，因此全身冷却期间向上移动的皮肤血流量（缺氧扩张）得以维持。
