Oldroyd Brian, Robinson Martin, Lindley Elizabeth, Rhodes Laura, Hind Karen
Carnegie Research Institute, Leeds Beckett University, Headingley Campus, Leeds, LS6 3QS, UK.
Physiol Meas. 2015 Dec;36(12):2503-17. doi: 10.1088/0967-3334/36/12/2503. Epub 2015 Nov 4.
The accurate measurement of total body water (TBW) in children has important clinical and nutritional applications. Resonant cavity perturbation (RCP) is a new method for estimating TBW. This method measures the dielectric properties of the body which are related to body water. For RCP measurements, each subject lay supine on a bed inside a screened room which acts as a resonant cavity. A network analyser measures the frequencies of two low-order cavity resonances of the room, with electric-field vectors that were respectively vertical and horizontal, the resonant frequency shifts relative to the empty room are then derived. These frequency shifts correlates with TBW. The aims of this present study were to (a) develop TBW(RCP) predictive equations for children using TBWdil as the criterion method, (b) cross-validate the derived equations, (c) determine precision of the TBW(RCP) method, and (d) compare the criterion method TBWdil with three methods of estimating TBW: RCP, MFBIS and anthropometry.Predictive equations, independent of sex, were developed with linear regression in a group of 36 children. The relationship between combined RCP frequency shifts and TBWdilution had an r2 = 0.90 and standard error of the estimate (SEE) =1.42 kg. Multiple regression analysis, that included a term for body mass index, only had a small effect on r2 = 0.93 and SEE = 1.25 kg. In vivo TBW precision for the vertical, horizontal and combined frequency modes ranged from 0.7 to 3.4%. Bland-Altman analysis indicated close agreement between the criterion method TBWdil and the three other methods of TBW estimation. Mean differences were TBW(RCP(2)) = 0.01 ± /- 1.34 kg, TBW(MFBIS) = 0.45 ± /- 1.35 kg, TBWAnthropometry = 0.29 ± /- 1.29 kg.Currently the RCP method does not significantly improve the prediction of TBW compared to MFBIS and anthropometry in this initial study. However the derived equation was independent of sex and body size had only a small effect.
准确测量儿童的总体水（TBW）具有重要的临床和营养应用价值。共振腔微扰法（RCP）是一种估算TBW的新方法。该方法通过测量与身体水分相关的身体介电特性来实现。在进行RCP测量时，每个受试者仰卧在一个屏蔽室内的床上，该屏蔽室充当一个共振腔。一台网络分析仪测量该房间两个低阶腔共振的频率，电场矢量分别为垂直和水平方向，然后得出相对于空房间的共振频率偏移。这些频率偏移与TBW相关。本研究的目的是：（a）以TBW稀释法作为标准方法，为儿童建立TBW（RCP）预测方程；（b）对推导的方程进行交叉验证；（c）确定TBW（RCP）方法的精密度；（d）将标准方法TBW稀释法与三种估算TBW的方法进行比较：RCP、多频生物电阻抗光谱法（MFBIS）和人体测量法。在一组36名儿童中，通过线性回归建立了与性别无关的预测方程。RCP频率偏移组合与TBW稀释之间的关系，决定系数（r2）=0.90，估计标准误差（SEE）=1.42 kg。包含体重指数项的多元回归分析，对r2=0.93和SEE=1.25 kg的影响较小。垂直、水平和组合频率模式下的体内TBW精密度范围为0.7%至3.4%。布兰德-奥特曼分析表明，标准方法TBW稀释法与其他三种TBW估算方法之间具有密切一致性。平均差异为：TBW（RCP（2））=0.01±/-1.34 kg，TBW（MFBIS）=0.45±/-1.35 kg，TBW人体测量法=0.29±/-1.29 kg。在这项初步研究中，目前与MFBIS和人体测量法相比，RCP方法在TBW预测方面没有显著改善。然而推导的方程与性别无关，且身体大小的影响较小。
