Metabolic Chambers

Big Chamber @ VCU
Small Chamber
Small Chamber @ VCU

Our lab consists of two whole-room indirect calorimeters, a.k.a human metabolic chambers (some biologists may refer to them as “human metabolic cages”). These chambers may look similar to regular living rooms, but they are highly precise instruments for measuring metabolic rates, i.e. how many calories you burn.

Such instruments are essential tools for metabolic studies that require overnight stays, environmental control (e.g. ambient temperature, humidity, light and sound), and long duration resting. Dietitians use them to study the effects of food and diet-induced thermogenesis on human metabolism. Endocrinologists and physiologists use them to study the effects of environmental changes and medical interventions on human metabolism. Such studies often require long-term, continuous monitoring with environmental control to capture the response to intervention, and metabolic chambers are perfect tools for this.

The metabolic chambers were constructed and integrated by MEI Research (Edina, MN), are located in the North Hospital on the medical campus of Virginia Commonwealth University (VCU). One chamber is the size of a living room (3m x 4m x 2.4m, “big chamber”) and can house a treadmill, a bike, a small desk, a toilet, and a wash basin at the same time. The other chamber is smaller (1.2 x 2.1 x 2.3 m, “small chamber”), with its volume further reduced by fitting in a set of bed boxes and a mattress, for a faster and more accurate response in energy expenditure readings. Both chambers are sealed and maintain positive pressure during data collection. Blood ports are also installed in the glass doors for in vivo blood sampling without the subject leaving the chamber. The chambers also have climate control, with an air conditioning (HVAC) system utilizing chilled water pipelines and electric heating coils, equipping the chambers for temperature-sensitive metabolic studies.

Each calorimeter, used together with wearable sensors, provides continuous monitoring of physiological parameters (e.g. energy expenditure, electrocardiography, electromyography, skin temperature, core body temperature, and fine-grained motion) with high accuracy and precision. Examples of recent trials using this instrument range from studying the acute effects of a new thyroid hormone formulation to probing an underlying mechanism in cancer cachexia.

Currently, according to partial data, there are less than 50 such systems around the world, and less than 20 in the United States. The majority of the medical studies still use metabolic carts to measure metabolic rates instead of the metabolic chambers. However, metabolic carts are not suitable for metabolic studies that involve a prolonged time or more intricate activities.