Phan Samson, Lissoway John, Lipman Grant S
Mechanical Engineering Department, Stanford University, Stanford, CA, USA.
Wilderness Environ Med. 2013 Mar;24(1):37-41. doi: 10.1016/j.wem.2012.10.004. Epub 2013 Jan 9.
Heat illness is a common ailment that, if left untreated, is associated with high morbidity and mortality. Chemical cold packs (CCPs) and ice packs are widely used in the pre-hospital setting and by those with limited resources, yet no controlled studies have compared the cooling of ice to that of CCPs. This study determined the theoretical cooling of CCPs on a benchtop model, comparing the results to similarly sized ice packs, and is the first known comparison of these hyperthermia treatments.
The CCPs used in Stanford University's Emergency Department were activated in an insulated volume of water (2 L), and temperature was recorded at 1-second intervals in a controlled environment (41°C at 20% humidity). The procedure was repeated with 1-quart ice packs.
The CCPs resulted in a 5.25°C degree temperature drop, with a time constant (time to 63% of initial temperature--a common engineering characterization metric) of 1.72 minutes for the test volume. Ice packs resulted on average in a 19.8°C temperature change, with a time constant of 26.8 minutes. The CCPs provide less overall temperature change and were shorter lived. Application of 6 CCPs on a 50th percentile male (weight 86.6 kg, height 1.7 m), assuming ideal heat transfer, would result in less than 0.5°C temperature change. Similarly configured ice packs would result in a 2.5°C change.
Experiments demonstrate that CCPs are inferior to similarly sized ice packs for thermal regulation, and lose their effectiveness more quickly. These findings support the consideration of ice packs as an alternative to chemical cold packs when cooling hyperthermic patients.
热相关疾病是一种常见病症，若不治疗，会导致高发病率和高死亡率。化学冷敷袋（CCP）和冰袋在院前急救环境以及资源有限的人群中被广泛使用，但尚无对照研究比较冰袋和化学冷敷袋的降温效果。本研究在台式模型上测定了化学冷敷袋的理论降温效果，并将结果与尺寸相同的冰袋进行比较，这是首次对这些用于治疗体温过高的方法进行比较。
在斯坦福大学急诊科使用的化学冷敷袋在2升隔热水中激活，并在受控环境（41°C，湿度20%）中每隔1秒记录一次温度。对1夸脱的冰袋重复该过程。
化学冷敷袋使温度下降了5.25°C，测试体积的时间常数（达到初始温度63%的时间——一种常见的工程特性指标）为1.72分钟。冰袋平均使温度变化了19.8°C，时间常数为26.8分钟。化学冷敷袋产生的总体温度变化较小，且持续时间较短。假设热传递理想，在第50百分位男性（体重86.6千克，身高1.7米）身上使用6个化学冷敷袋，温度变化将小于0.5°C。同样配置的冰袋会使温度变化2.5°C。
实验表明，在温度调节方面，化学冷敷袋不如尺寸相同的冰袋，且其效果消失得更快。这些发现支持在为体温过高的患者降温时考虑使用冰袋替代化学冷敷袋。
