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 various 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 16 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 (controlled) and B (assisted) depending on the ventilation mode. All patients in group A, but only 48.8% of those in group B, received some form of analgosedation, and the doses were significantly higher in group A. The 30-min steady 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 between 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 very well with the 30-min steady state test in both mechanically ventilated and 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 acceptable to spontaneously breathing patients.