Validity of an abbreviated indirect calorimetry protocol for measurement of resting energy expenditure in mechanically ventilated and spontaneously breathing critically ill patients

Objective: To test a short indirect calorimetry protocol with five stable 1 -min readings (5-min steady state) against the commonly used protocol of 30 1-min readings (30-min steady state) in critically ill patients with vario us modes of ventilation. Design: A prospective clinical study. Setting: A medical ICU of a university hospital. Subjects: Forty-six mechanically ventilated patients (group A and B), and 1 6 spontaneously breathing patients (group C). Intervention: Indirect calorimetry with the Deltatrac II MBM-200 Metabolic Monitor. Results: Mechanically ventilated patients were classified into group A (con trolled) and B (assisted) depending on the ventilation mode. All patients i n group A, but only 48.8% of those in group B, received some form of analgo sedation, and the doses were significantly higher in group A. The 30-min st eady state test was 100.0%, 83.7%, and 75.0% successful in group A, B, and C, respectively. The corresponding rate for the 5-min steady state test was 100.0%, 81.4%, and 100.0%, respectively. The coefficient of determination (r(2)) for resting, energy expenditure between the two protocols ranged bet ween 0.972 and 0.994. The time required to collect the, 5-min steady state data was 5.5 +/- 1.1, 9.9 +/- 5.7, and 6.5 +/- 3.3 min for group A, B, and C, respectively. Conclusion: Indirect calorimetry with 5-min steady state test correlated ve ry well with the 30-min steady state test in both mechanically ventilated a nd spontaneously breathing patients. The time required varies de-pending on the mode of ventilation, and it is influenced by the level of sedation in mechanically ventilated patients. The abbreviated protocol may be more acce ptable to spontaneously breathing patients.