VALIDATION OF A 5-MINUTE STEADY-STATE INDIRECT CALORIMETRY PROTOCOL FOR RESTING ENERGY-EXPENDITURE IN CRITICALLY ILL PATIENTS

Objective: Numerous protocols are used for indirect calorimetry in res earch and clinical settings. The objective of the current study was to validate in critically ill patients an abbreviated protocol that uses five consecutive stable 1-minute readings of oxygen consumption (VO2) , carbon dioxide production (VCO2), and minute ventilation (V-E) in a range of +/- 5%, versus a more standard protocol that uses 30 consecut ive stable one minute readings of VO2, VCO2, and V-E in a range of +/- 10%. Methods: Indirect calorimetry was performed on resting, mechanic ally ventilated, critically ill patients. The first 5-minute period in which coefficients of variation for VO2, VCO2 and V-E were less than or equal to 5% was compared to the first 30-minute period in which coe fficients of variation for these variables were less than or equal to 10%. Results: Thirty-four critically ill patients were studied. Twenty four patients (70%) successfully completed both protocols (Success Gr oup). Eighteen percent of subjects completed neither the abbreviated n or the 30 minute protocol, and 12% completed only one protocol (Fail G roup). The Success Group was marked by a higher incidence of sedation and/or medical paralysis. There were no significant differences in V-E , VO2, VCO2, respiratory quotient, or energy expenditure between the p rotocols in the Success Group or the Fail Group. Coefficients of deter mination (R(2)) for VO2 and VCO2 between the two methods in the Succes s Group were 0.99. In the Fail Group, R(2) values ranged from 0.75 for VCO2 to 0.91 for VO2. Conclusion: In sedated, mechanically ventilated patients, an indirect calorimetry test of five consecutive 1-minute p eriods with coefficient of variation less than or equal to 5% is equiv alent to a longer test consisting of 30 consecutive 1-minute periods w ith coefficient of variation less than or equal to 10%.