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

Abstract

Objective: To determine how accurately total daily energy expenditure can be estimated from measurement periods of less than 24 h in mechanically ventilated 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 weeks - 13 years) with a FiO(2)of less than 60% and tube leakage < 10% (the difference between inspiratory and expiratory tidal volume measured by the ventilator). Separately, in five patients with varying tube leakage (2-59%) the influence of tube leakage on measured energy expenditure was determined.

Measurement: Energy expenditure was measured by indirect calorimetry. Total daily energy expenditure measurements for 24 h were compared with 2 h energy expenditure measurements. The influence of body temperature on measured energy expenditure was determined.

Results: The mean coefficient of variation 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/ degrees C. An increased tube leakage influenced the energy expenditure measurements significantly (P<< 0. 001).

Conclusion: In a clinical situation in patients with a tube leakage << 10% total daily energy expenditure can be estimated from a 2 h measurement period.