Comparison of Calculated and Measured Energy Expenditure Determination Methods

Abstract

Objective:Indirect calorimetry (IC) is considered the gold standard in the accurate determination of energy consumption in intensive care patients. This study compared measured energy expenditure (MEE) with estimated energy expenditure (EEE), calculated from predictive equations, in mechanically ventilated patients.Materials and Methods:This study was conducted on 40 patients hospitalized in our medical/surgical intensive care unit. Twenty four-hour energy consumption measured by IC and energy consumption calculated by adding correction factors for actual and corrected weights using Harris-Benedict, Schofield, Ireton-Jones and Swinamer equations were compared.Results:MEE was 2697.9±606.0 kcal/day. All of the EEE values, calculated using equations were moderately correlated with MEE and correlations were stronger with adjusted body weights, however, Bland-Altman statistics represent wide limits of agreement. From another perspective, EEE corresponding to between 80% and 110% of MEE was considered an adequate feeding range and provided the best levels of proficiency using adjusted body weight and Long factors; however, at least, 20% of patients remained at under-or overfeeding risk.Conclusion:It was concluded that the estimation equations are unreliable in determining energy consumption in mechanically ventilated intensive care patients due to wide limits of agreement. Estimates falling in the range of 80-110% of MEE also indicate the possibility of malnutrition. Our study supports previous studies, which indicated that nutrition management requires an individual approach.

Keywords

• indirect calorimetry
• estimating energy expenditure
• mechanical ventilation
• nutrition
• intensive care unit