Matthews D E, Gilker C D
Department of Medicine, Cornell University Medical College, New York, NY 10021, USA.
Obes Res. 1995 Mar;3 Suppl 1:21-9.
Measurement of total energy expenditure using [2H,18O] water requires both accurate and precise determination of the rates of disappearance of 2H and 18O from body water over time and determination of the 2H and 18O pool sizes. However, the impact of the isotopic determination of body water upon the determination of energy expenditure is often overlooked. For measurement of total body water per se, the delay after administration before sampling body fluids becomes important, and saliva sampling can be used to resolve the timing of early samples for body water determination. For energy expenditure measurement per se, linear regression can be used to define the initial dilution. Because the hydrogen tracer dilutes into a pool significantly larger than body water pool per se due to the presence of labile hydrogens, a correction to the isotope pool size must be applied. The theoretical calculations of the exchangeable hydrogen pool presented here suggest that the hydrogen pool size is < 3% greater than the body water pool and data are provided to support this idea. Finally, the two approaches used to define the body water pool space contribution to the calculation of energy expenditure using 2H2(18)O are reviewed. Using a pool size based upon the average of the two pool spaces limits the effect of pool size error in the calculation of energy expenditure.
使用[2H,18O]水测量总能量消耗需要准确且精确地测定2H和18O随时间从身体水分中消失的速率以及2H和18O的池大小。然而，身体水分的同位素测定对能量消耗测定的影响常常被忽视。对于本身测量总体水而言，给药后到采集体液样本之间的延迟很重要，唾液采样可用于解决早期样本用于身体水分测定的时间问题。对于本身的能量消耗测量，线性回归可用于定义初始稀释。由于存在不稳定氢，氢示踪剂稀释到的池比身体水分池本身大得多，因此必须对同位素池大小进行校正。此处给出的可交换氢池的理论计算表明，氢池大小比身体水分池大不到3%，并提供了数据支持这一观点。最后，回顾了用于定义身体水分池空间对使用2H2(18)O计算能量消耗的贡献的两种方法。使用基于两个池空间平均值的池大小可限制池大小误差在能量消耗计算中的影响。
