Bräuer A, English M J M, Lorenz N, Steinmetz N, Perl T, Braun U, Weyland W
Department of Anesthesiology, Emergency and Intensive Care Medicine, University of Göttingen, Germany.
Acta Anaesthesiol Scand. 2003 Jan;47(1):58-64. doi: 10.1034/j.1399-6576.2003.470110.x.
BACKGROUND: Forced-air warming has gained high acceptance as a measure for the prevention of intraoperative hypothermia. However, data on heat transfer with lower body blankets are not yet available. This study was conducted to determine the heat transfer efficacy of six complete lower body warming systems. METHODS: Heat transfer of forced-air warmers can be described as follows:[1]Qdot;=h.DeltaT.A where Qdot; = heat transfer [W], h = heat exchange coefficient [W m-2 degrees C-1], DeltaT = temperature gradient between blanket and surface [ degrees C], A = covered area [m2]. We tested the following forced-air warmers in a previously validated copper manikin of the human body: (1) Bair Hugger and lower body blanket (Augustine Medical Inc., Eden Prairie, MN); (2) Thermacare and lower body blanket (Gaymar Industries, Orchard Park, NY); (3) WarmAir and lower body blanket (Cincinnati Sub-Zero Products, Cincinnati, OH); (4) Warm-Gard(R) and lower body blanket (Luis Gibeck AB, Upplands Väsby, Sweden); (5) Warm-Gard and reusable lower body blanket (Luis Gibeck AB); and (6) WarmTouch and lower body blanket (Mallinckrodt Medical Inc., St. Luis, MO). Heat flux and surface temperature were measured with 16 calibrated heat flux transducers. Blanket temperature was measured using 16 thermocouples. DeltaT was varied between -10 and +10 degrees C and h was determined by a linear regression analysis as the slope of DeltaT vs. heat flux. Mean DeltaT was determined for surface temperatures between 36 and 38 degrees C, because similar mean skin temperatures have been found in volunteers. The area covered by the blankets was estimated to be 0.54 m2. RESULTS: Heat transfer from the blanket to the manikin was different for surface temperatures between 36 degrees C and 38 degrees C. At a surface temperature of 36 degrees C the heat transfer was higher (between 13.4 W to 18.3 W) than at surface temperatures of 38 degrees C (8-11.5 W). The highest heat transfer was delivered by the Thermacare system (8.3-18.3 W), the lowest heat transfer was delivered by the Warm-Gard system with the single use blanket (8-13.4 W). The heat exchange coefficient varied between 12.5 W m-2 degrees C-1 and 30.8 W m-2 degrees C-1, mean DeltaT varied between 1.04 degrees C and 2.48 degrees C for surface temperatures of 36 degrees C and between 0.50 degrees C and 1.63 degrees C for surface temperatures of 38 degrees C. CONCLUSION: No relevant differences in heat transfer of lower body blankets were found between the different forced-air warming systems tested. Heat transfer was lower than heat transfer by upper body blankets tested in a previous study. However, forced-air warming systems with lower body blankets are still more effective than forced-air warming systems with upper body blankets in the prevention of perioperative hypothermia, because they cover a larger area of the body surface.
背景：强制空气加温作为预防术中低体温的一种措施已获得高度认可。然而，关于下身毯热传递的数据尚不可得。本研究旨在确定六种完整下身加温系统的热传递效果。 方法：强制空气加温器的热传递可描述如下：[1]Qdot;=h.DeltaT.A，其中Qdot; = 热传递[瓦]，h = 热交换系数[瓦·米-2·摄氏度-1]，DeltaT = 毯子与体表之间的温度梯度[摄氏度]，A = 覆盖面积[平方米]。我们在先前验证过的人体铜质模型中测试了以下强制空气加温器：(1) Bair Hugger及下身毯（奥古斯汀医疗公司，明尼苏达州伊甸草原）；(2) Thermacare及下身毯（盖马尔工业公司，纽约州果园公园）；(3) WarmAir及下身毯（辛辛那提零下产品公司，俄亥俄州辛辛那提）；(4) Warm-Gard(R)及下身毯（瑞典乌普兰德瓦斯比的路易斯·吉贝克公司）；(5) Warm-Gard及可重复使用的下身毯（路易斯·吉贝克公司）；以及(6) WarmTouch及下身毯（马林克罗特医疗公司，密苏里州圣路易斯）。使用16个校准过的热通量传感器测量热通量和体表温度。使用16个热电偶测量毯子温度。DeltaT在-10至+10摄氏度之间变化，h通过线性回归分析确定为DeltaT与热通量关系曲线的斜率。对于体表温度在36至38摄氏度之间的情况确定平均DeltaT，因为在志愿者中发现了类似的平均皮肤温度。毯子覆盖的面积估计为0.54平方米。 结果：对于体表温度在36摄氏度至38摄氏度之间的情况，毯子向模型的热传递有所不同。在体表温度为36摄氏度时，热传递（在13.4瓦至18.3瓦之间）高于体表温度为38摄氏度时（8 - 11.5瓦）。Thermacare系统的热传递最高（8.3 - 18.3瓦），使用一次性毯子的Warm-Gard系统的热传递最低（8 - 13.4瓦）。热交换系数在12.5瓦·米-2·摄氏度-1至30.8瓦·米-2·摄氏度-1之间变化，对于体表温度为36摄氏度时平均DeltaT在1.04摄氏度至2.48摄氏度之间变化，对于体表温度为38摄氏度时平均DeltaT在0.50摄氏度至1.63摄氏度之间变化。 结论：在所测试的不同强制空气加温系统之间，下身毯的热传递未发现显著差异。热传递低于先前研究中测试的上身毯的热传递。然而，带有下身毯的强制空气加温系统在预防围手术期低体温方面仍比带有上身毯的强制空气加温系统更有效，因为它们覆盖了更大面积的体表。
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