Indirect calorimetry in mechanically ventilated infants and children: accuracy of total daily energy expenditure with 2 hour measurements

Objective: To determine how accurately total daily energy expenditure can b e estimated from measurement periods of less than 24 h in mechanically vent ilated infants and children. Design: Prospective study to validate a method to determine energy expenditure. Setting: Pediatric intensive care unit of an university hospital. Patients: Nineteen ventilated patients (age 3 week s - 13 years) with a FiO(2) of less than 60% and tube leakage < 10% (the di fference between inspiratory and expiratory tidal volume measured by the ve ntilator). Separately, in five patients with varying tube leakage (2-59%) t he influence of tube leakage on measured energy expenditure was determined, Measurements: Energy expenditure was measured by indirect calorimetry. Tot al daily energy expenditure measurements for 24 h were compared with 2 h en ergy expenditure measurements. The influence of body temperature on measure d energy expenditure was determined. Results: The mean coefficient of varia tion among 2 hour periods of measured energy expenditure was 6% (range 2-11 %) compared with total daily energy expenditure measurements. The influence of body temperature revealed an increase of 6% of energy expenditure/degre es C. An increased tube leakage influenced the energy expenditure measureme nts significantly (P < 0.001). Conclusion: In a clinical situation in patie nts with a tube leakage < 10% total daily energy expenditure can be estimat ed from a 2 h measurement period.