TOTAL-BODY ELECTRICAL-CONDUCTIVITY MEASUREMENTS - AN EVALUATION OF CURRENT INSTRUMENTATION FOR INFANTS

Quantitation of the body's fat and lean masses is an important compone nt of nutritional assessment. Such measurements, however, are difficul t to conduct routinely in infants due to the numerous limitations of t raditional methods. The application of total body electrical conductiv ity measurements for quantitating fat-free mass (FFM) overcomes many o f these limitations. The instruments required to perform these measure ments in pediatric patients (HP-2) have recently become commercially a vailable, but their measurement performance has not been evaluated. In these studies, we compared the precision, day-to-day variability, and magnetic field profile of three HP-2 instruments. We also derived a n ew calibration equation that relates the FFM to the total body electri cal conductivity measurement in piglets, and compared it with an equat ion (provided currently by the manufacturer) derived on a prototype in strument. The performance of the instruments was generally similar, al though a significant difference in the magnetic field of one instrumen t was identified. The coefficient of variation of inanimate phantom me asurements varied from +/-0.2 to +/-0.5%, and the day-to-day variabili ty was generally similar. Such measurement error is significant (+/-0. 035 to +/-0.078 kg FFM) for small subjects. The new calibration equati on was similar to the original equation; therefore, all the data were pooled to generate a new equation that is linear at least to 10 kg. Th us, the HP-2 total body electrical conductivity instruments, which can be safely and easily used to measure FFM and fat in infants through 1 y of age, proved to be reliable and precise, and results obtained fro m different instruments can be confidently compared.