Piantadosi C A, Thalmann E D, Spaur W H
J Appl Physiol Respir Environ Exerc Physiol. 1981 Apr;50(4):829-34. doi: 10.1152/jappl.1981.50.4.829.
To study the phenomenon of isolated core cooling, four resting men breathed cooled helium-oxygen (T in = 14 +/- 2 degrees C, 40-60% relative humidity) in a warm hyperbaric chamber at pressures equivalent to 640, 1,000, and 1,400, and 1,800 ft seawater (fsw). Rectal temperature (T re) fell by 0.43 +/- 0.13 degrees C at 640 fsw to 0.98 +/- 0.15 degrees C at 1,800 fsw after 60 min. The rate at which T re fell was linearly related to the product of inspired gas density times specific heat. The metabolic response (VO2) to this isolated core cooling was more closely related to the rate of fall in T re than to the magnitude of this fall. A distinct threshold temperature, below which a rise in VO2 would occur, was not demonstrable. However, when the rate of fall of T re exceeded 0.70 degrees C . h-1, VO2 increased above base line, in spite of high skin temperatures that may have blunted the VO2 response. When VO2 did increase, its net benefit on thermal homeostasis was negated by the associated rise in pulmonary ventilation and its attendant increase in respiratory heat loss. Breathing cool helium-oxygen under hyperbaric conditions can rapidly lower deep body temperature, even in the presence of a warm body surface.
为研究孤立性核心降温现象，四名静息男性在一个温暖的高压舱内呼吸冷却的氦氧混合气（吸入温度=14±2℃，相对湿度40 - 60%），压力相当于640、1000、1400和1800英尺海水深度（fsw）。60分钟后，直肠温度（Tre）在640 fsw时下降了0.43±0.13℃，在1800 fsw时下降到0.98±0.15℃。Tre下降的速率与吸入气体密度乘以比热的乘积呈线性相关。这种孤立性核心降温引起的代谢反应（VO2）与Tre下降的速率比与Tre下降的幅度关系更密切。未发现低于该温度VO2会升高的明显阈值温度。然而，当Tre下降速率超过0.70℃·h-1时，尽管皮肤温度较高可能削弱了VO2反应，但VO2仍高于基线水平升高。当VO2确实升高时，其对热稳态的净益处被随之而来的肺通气增加及其伴随的呼吸热损失增加所抵消。即使体表温暖，在高压条件下呼吸冷却的氦氧混合气也能迅速降低深部体温。
