Coward W A, Roberts S B, Cole T J
Medical Research Council, Dunn Nutrition Laboratory, Cambridge, UK.
Eur J Clin Nutr. 1988 Mar;42(3):207-12.
In the doubly-labelled water (2H2(18)O) method for the measurement of carbon dioxide production rate in man, single exponential disappearance curves for 2H2O and H2(18)O in body water are used; the precision with which the slopes and intercepts of the curves are estimated determines the precision of the estimate of carbon dioxide production rate. In studies with infants, and in computer simulations, the effect of different experimental regimes on the overall precision of the carbon dioxide production estimate was investigated. When the number of data points used was progressively reduced by shortening the total observation period from 7 d (about 3 biological half-lives for the isotopes) to 1 d there was a deleterious effect on precision and in the infants there was an upward bias in the values for carbon dioxide production. When the number of data points was reduced by removing points from the middle of the exponential curves with the maintenance of the 7-d experimental period, precision was also reduced but by less than in the former procedure and there were no consistent trends in the average values for carbon dioxide production.
在用于测量人体二氧化碳产生率的双标记水（2H2(18)O）法中，采用了体内水中2H2O和H2(18)O的单指数消失曲线；对曲线斜率和截距估计的精确程度决定了二氧化碳产生率估计值的精确程度。在针对婴儿的研究以及计算机模拟中，研究了不同实验方案对二氧化碳产生率总体估计精度的影响。当通过将总观察期从7天（约为同位素的3个生物半衰期）缩短至1天来逐步减少所使用的数据点数时，对精度产生了有害影响，并且在婴儿中二氧化碳产生值出现向上偏差。当通过从指数曲线中间去除数据点来减少数据点数同时保持7天的实验期时，精度也有所降低，但降低程度小于前一种方法，并且二氧化碳产生的平均值没有一致的趋势。
