Frankenfield D C, Cooney R N, Smith J S, Rowe W A
Department of Clinical Nutrition, The Milton S Hershey Medical Center, Pennsylvania State University, Hershey, PA 17033, USA.
Am J Clin Nutr. 1999 Mar;69(3):426-31. doi: 10.1093/ajcn/69.3.426.
Determination of body composition during critical illness is complex because of various patient-related and technical factors. Bioelectrical impedance is a promising technique for the analysis of body composition; however, its clinical utility in critically injured patients is unknown.
The purpose of this study was to compare bioelectrical impedance with metabolic activity in healthy and critically injured patients. If bioelectrical impedance accurately determines body composition during critical illness, the slope between body-composition variables and oxygen consumption would be the same in critically injured and healthy subjects.
There is a strong linear relation between body composition and metabolic activity. In the present study, body composition (fat-free mass and body cell mass) was determined by using bioelectrical impedance and resting metabolic activity (metabolic rate and oxygen consumption) by using gas exchange analysis in a group of healthy and critically injured subjects. The relation between these variables was compared by using linear regression to a similar relation established by hydrostatic weighing in a large historical control group.
The slope of the line relating fat-free mass to resting metabolic rate was the same in the healthy and critically ill groups (P = 0.62) and each was similar to the slope of the line for the control group. However, in 37% of the critically injured group, overhydration contributed to an increase in fat-free mass, disturbing the relation with resting metabolic rate. The slope of the line relating body cell mass to oxygen consumption in our healthy and critically ill groups was almost identical.
These results support the use of bioelectrical impedance to determine body cell mass in healthy and critically ill subjects.
由于各种与患者相关的因素和技术因素，危重症期间身体成分的测定较为复杂。生物电阻抗是一种很有前景的身体成分分析技术；然而，其在危重伤员中的临床实用性尚不清楚。
本研究旨在比较健康受试者和危重伤员的生物电阻抗与代谢活性。如果生物电阻抗能准确测定危重症期间的身体成分，那么危重伤员和健康受试者身体成分变量与耗氧量之间的斜率将相同。
身体成分与代谢活性之间存在很强的线性关系。在本研究中，通过生物电阻抗测定一组健康受试者和危重伤员的身体成分（去脂体重和体细胞质量），并通过气体交换分析测定静息代谢活性（代谢率和耗氧量）。通过线性回归将这些变量之间的关系与一个大型历史对照组通过水下称重建立的类似关系进行比较。
健康组和危重症组中去脂体重与静息代谢率之间直线的斜率相同（P = 0.62），且每组均与对照组直线的斜率相似。然而，在37%的危重伤员组中，水合过度导致去脂体重增加，扰乱了与静息代谢率的关系。我们的健康组和危重症组中体细胞质量与耗氧量之间直线的斜率几乎相同。
这些结果支持使用生物电阻抗来测定健康受试者和危重症患者的体细胞质量。
