Allison T G, Reger W E
Department of Internal Medicine and Cardiovascular Diseases, Mayo Clinic, Rochester, MN 55905, USA.
Aviat Space Environ Med. 1998 Sep;69(9):845-50.
The recommended maximum water temperature for public hot tubs has been set at 40.0 degrees C, but no research has been published on human immersion in hot water at higher temperatures.
We hypothesized that thermoregulatory and cardiovascular responses at two water temperatures would be proportional to the water:blood temperature gradients.
Six healthy men were immersed for 21 min in circulating hot water at 40.0 and 41.5 degrees C in separate trials in random order 1-3 wk apart. Measurements included heart rate, systolic BP, esophageal, rectal, and non-immersed skin temperatures, sweat rate, and perceived comfort.
The rise in all body temperatures, sweat rate, and heart rate were significantly greater in the 41.5 vs. 40.0 degrees C water. Peak esophageal temperatures were 38.3 +/- 0.2 degrees C vs. 37.8 +/- 0.03 degrees C, peak sweat rates were 0.48 +/- 0.05 vs. 0.32 +/- 0.03 kg x m(-2) x h(-1), and peak heart rates were 123 +/- 7 vs. 108 +/- 5 bpm, respectively. Systolic BPs followed different patterns of response in each trial, whereas diastolic pressures were not different between trials. Comfort at each level of immersion was reduced during the 41.5 degrees C trial compared with the 40.0 degrees C in excess of that predicted by difference in esophageal temperature between the trials.
These results suggest that risks of hyperthermia or adverse cardiovascular effects in hot tubs may not be greater in water above 40.0 degrees C unless perceptual judgment is impaired. Hypotension when standing to exit the tub occurred in both trials and may represent a potential hazard to hot tub use.
公共热水浴缸的推荐最高水温设定为40.0摄氏度，但尚无关于人体浸泡在更高温度热水中的研究发表。
我们假设在两种水温下的体温调节和心血管反应与水和血液的温度梯度成正比。
六名健康男性在相隔1 - 3周的不同试验中，分别随机顺序浸泡在40.0摄氏度和41.5摄氏度的循环热水中21分钟。测量指标包括心率、收缩压、食管温度、直肠温度、未浸泡皮肤温度、出汗率和舒适感。
在41.5摄氏度水中，所有体温升高、出汗率和心率均显著高于40.0摄氏度水。食管温度峰值分别为38.3±0.2摄氏度和37.8±0.03摄氏度，出汗率峰值分别为0.48±0.05和0.32±0.03千克·米-2·小时-1，心率峰值分别为123±7和108±5次/分钟。每次试验中收缩压呈现不同的反应模式，而各试验间舒张压无差异。与40.0摄氏度试验相比，41.5摄氏度试验中每个浸泡水平的舒适度降低幅度超过了根据试验间食管温度差异所预测的幅度。
这些结果表明，除非感知判断受损，否则在水温高于40.0摄氏度的热水浴缸中发生体温过高或心血管不良影响的风险可能不会更大。在两个试验中，站立起身离开浴缸时均出现低血压，这可能是使用热水浴缸的一个潜在危险。
