"High tech" metabolic measurements: useful in daily clinical practice?

Metabolic carts (MC) for indirect calorimetry are expensive, require the use of meticulous technique by trained personnel, and impose conditions that are difficult to maintain in critically ill patients. Of 822 nutrition teams surveyed, 101 of 420 respondents had MC, and 47 were considering purchase. Forty-one with MC never used them, and of the remaining 60 users, two-thirds performed fewer than 10 measurements per month, citing calibration difficulties and clinical problems as frequent limiting factors. Sixty-one% of users had no protocol for MC use. Although 95% of users would alter energy input, and 78% would modify nonprotein substrate based on MC results, 43% found O2 consumption and 33% found CO2 production significantly different from expected values. Five noted extremely inconsistent results with MC. Because of frequent dissatisfaction by MC owners due to expense, repairs, calibration difficulties, and technical limitations in critically ill patients most likely to benefit, and a 40% nonuse among teams with MC, MC do not seem to be a justifiable investment for most clinical nutrition practices, unless a suitable commitment is also made to provide skilled personnel, to institute protocols, and to implement frequent use.