Which statement about nutrient infusion stability prior to indirect calorimetry is true?

Which statement about nutrient infusion stability prior to indirect calorimetry is true?

• A. The rate and composition should be stable for at least 12 hours
• B. The rate should be adjusted every hour during measurement
• C. Stability is not necessary
• D. Infusion must be stopped during measurement

Answer: (A)

Indirect calorimetry relies on a steady, resting metabolic state so that oxygen use and carbon dioxide production reflect true energy expenditure rather than responses to changing substrate availability. If the nutrient infusion rate or its macronutrient makeup changes, the body’s substrate oxidation shifts, which can alter the respiratory quotient and gas exchange readings, producing inaccurate measurements. Maintaining a stable infusion rate and composition for a sufficient period before testing allows the metabolism to reach a steady state with respect to feeding, giving a reliable calorimetry result. Stopping the infusion or adjusting it during measurement would disrupt this steady state and confound the results.

Indirect calorimetry relies on a steady, resting metabolic state so that oxygen use and carbon dioxide production reflect true energy expenditure rather than responses to changing substrate availability. If the nutrient infusion rate or its macronutrient makeup changes, the body’s substrate oxidation shifts, which can alter the respiratory quotient and gas exchange readings, producing inaccurate measurements. Maintaining a stable infusion rate and composition for a sufficient period before testing allows the metabolism to reach a steady state with respect to feeding, giving a reliable calorimetry result. Stopping the infusion or adjusting it during measurement would disrupt this steady state and confound the results.