A single, accurate measurement of resting metabolic expenditure.

Indirect calorimetry is widely used in estimating nutritional requirements for severely ill patients. However, because the accuracy of a single measurement is dependent on many factors, the authors have sought to find the optimal single measurement. It is shown here that a more accurate resting metabolic expenditure (RME) can be obtained by studying a fasted, rested patient in relaxing surroundings after acclimatizing him or her to the calorimetric hood. Using this altered protocol, a significantly lower RME (by a mean of 125 kcal/d, p less than 0.0001) is achieved. This RME compares well with most of the various predictive equations. A predictive equation, based on the normal patients in this study and relating the RME to TBK (a measure of the body cell mass), allows calculation of a predicted RME, and subsequently a Stress Index as a measure of metabolic stress, ie, Predicted RME = TBK X 0.34 + 4.94. Stress Index = Measured RME/Predicted RME.