Zhu F, Kuhlmann M K, Kaysen G A, Sarkar S, Kaitwatcharachai C, Khilnani R, Stevens L, Leonard E F, Wang J, Heymsfield S, Levin N W
Renal Research Institute, Yorkville Dialysis Center, 1555 3rd Ave. #218, New York, NY 10128, USA.
J Appl Physiol (1985). 2006 Feb;100(2):717-24. doi: 10.1152/japplphysiol.00669.2005. Epub 2005 Oct 27.
Discrepancies in body fluid estimates between segmental bioimpedance spectroscopy (SBIS) and gold-standard methods may be due to the use of a uniform value of tissue resistivity to compute extracellular fluid volume (ECV) and intracellular fluid volume (ICV). Discrepancies may also arise from the exclusion of fluid volumes of hands, feet, neck, and head from measurements due to electrode positions. The aim of this study was to define the specific resistivity of various body segments and to use those values for computation of ECV and ICV along with a correction for unmeasured fluid volumes. Twenty-nine maintenance hemodialysis patients (16 men) underwent body composition analysis including whole body MRI, whole body potassium (40K) content, deuterium, and sodium bromide dilution, and segmental and wrist-to-ankle bioimpedance spectroscopy, all performed on the same day before a hemodialysis. Segment-specific resistivity was determined from segmental fat-free mass (FFM; by MRI), hydration status of FFM (by deuterium and sodium bromide), tissue resistance (by SBIS), and segment length. Segmental FFM was higher and extracellular hydration of FFM was lower in men compared with women. Segment-specific resistivity values for arm, trunk, and leg all differed from the uniform resistivity used in traditional SBIS algorithms. Estimates for whole body ECV, ICV, and total body water from SBIS using segmental instead of uniform resistivity values and after adjustment for unmeasured fluid volumes of the body did not differ significantly from gold-standard measures. The uniform tissue resistivity values used in traditional SBIS algorithms result in underestimation of ECV, ICV, and total body water. Use of segmental resistivity values combined with adjustment for body volumes that are neglected by traditional SBIS technique significantly improves estimations of body fluid volume in hemodialysis patients.
节段生物电阻抗光谱法（SBIS）与金标准方法在体液估计方面的差异可能是由于使用统一的组织电阻率值来计算细胞外液体积（ECV）和细胞内液体积（ICV）。差异也可能源于因电极位置而在测量中排除了手、脚、颈部和头部的液体体积。本研究的目的是确定身体各节段的比电阻率，并使用这些值计算ECV和ICV，同时对未测量的液体体积进行校正。29名维持性血液透析患者（16名男性）接受了身体成分分析，包括全身MRI、全身钾（40K）含量、氘和溴化钠稀释，以及节段和腕踝生物电阻抗光谱法，所有这些均在血液透析前同一天进行。节段比电阻率由节段无脂肪质量（FFM；通过MRI）、FFM的水合状态（通过氘和溴化钠）、组织电阻（通过SBIS）和节段长度确定。与女性相比，男性的节段FFM更高，FFM的细胞外水合更低。手臂、躯干和腿部的节段比电阻率值均与传统SBIS算法中使用的统一电阻率不同。使用节段而非统一电阻率值并对身体未测量的液体体积进行调整后，通过SBIS对全身ECV、ICV和总体水的估计与金标准测量值无显著差异。传统SBIS算法中使用的统一组织电阻率值会导致ECV、ICV和总体水的估计值偏低。使用节段电阻率值并结合对传统SBIS技术忽略的身体体积进行调整，可显著改善血液透析患者体液体积的估计。
