Construction and set-up of a whole-room indirect calorimeter for measurement of human energy metabolism

By measuring oxygen consumption and carbon dioxide production, indirect calorimetry is the most commonly used method to assess human energy metabolism as it provides minute-by-minute measurements of whole-body energy expenditure and substrate oxidation. Whole-room indirect calorimeters (also known as respiratory or metabolic chambers) are comfortable, air-tight room that allow for continuous measurements of energy metabolism from few hours up to several days with meals delivered to volunteers inside the chamber through an airlock, thus permitting the assessment of each component of daily energy expenditure (sleeping metabolic rate, the thermic effect of food, and the cost of physical activity detected by radar system based on the Doppler Effect). Metabolic chambers are very complex systems to build, set-up, validate, and maintain over time to ensure accurate measurements of human energy metabolism. Herein, we provide a detailed description of a state-of-the-art metabolic chamber system recently built at the University Hospital in Pisa, Italy, including the set-up and integration of several environmental sensors and equipment into a unique system to ensure accuracy, reproducibility, and reliability of metabolic measurements.