van Kreel B K, Cox-Reyven N, Soeters P
Department of Clinical Chemistry, University Hospital Maastricht, The Netherlands.
Med Biol Eng Comput. 1998 May;36(3):337-45. doi: 10.1007/BF02522480.
Multifrequency bio-electronic impedance analysis (MF BIA) measurements are taken from a heterogeneous group of patients, varying in size between obese and slim. The measuring system uses four electrodes: two current and two potential electrodes. Three new models are developed to calculate total body water (TBW) from the BIA data, and the resulting TBW values are compared with TBW determined by D2O dilution. The results demonstrate that the most simple model provides the best TBW values. For individual patients, TBW can be determined by means of bioimpedance measurement with an accuracy of 3 litres. In the most simple model (model 1), the body is electrically represented by a cylinder, and corrections are made for the amount of fat. This is an extension of the model used by Xitron. In the more advanced models (2 and 3), the body is represented by a cylinder for the trunk, and truncated cones represent the arms and legs. In model 2, delta TBW amounts to 3 litres. It is shown that the resistance of the trunk is proportional to the square root of the length. In model 3, it is assumed that subcutaneous fat is a poor conductor of electric current. An equation is developed that describes the partition of subcutaneous fat, and the fat layer is then removed from the cones representing arms and legs and from the cylinder that models the trunk.
多频生物电阻抗分析（MF BIA）测量针对的是一组异质性患者，其体型从肥胖到消瘦各不相同。测量系统使用四个电极：两个电流电极和两个电位电极。开发了三种新模型，用于根据生物电阻抗分析数据计算总体水（TBW），并将所得的TBW值与通过重水（D2O）稀释法测定的TBW进行比较。结果表明，最简单的模型提供了最佳的TBW值。对于个体患者，可通过生物电阻抗测量来确定TBW，其准确度为3升。在最简单的模型（模型1）中，人体用电学方式表示为一个圆柱体，并对脂肪量进行校正。这是对Xitron所使用模型的扩展。在更先进的模型（2和3）中，人体的躯干用电学方式表示为一个圆柱体，而截断的圆锥体表示手臂和腿部。在模型2中，TBW的差值为3升。结果表明，躯干的电阻与长度的平方根成正比。在模型3中，假定皮下脂肪是电流的不良导体。推导了一个描述皮下脂肪分布的方程，然后从代表手臂和腿部的圆锥体以及模拟躯干的圆柱体中去除脂肪层。
