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

Abstract

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-rain steady slate test was 100.0%, 81.4 %, and 100.0%, respectively. The coefficient of determination (r2) 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 depending 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.