Whole-body calorimeter

The term macrocalorimeter is not used very often but will usually imply a vessel volume of 0.1-1 1 and a power sensitivity significantly lower than what is typical for microcalorimeters. A whole body calorimeter is a term used for large, up to room-size, calorimeters employed for direct measurement of heat produced by humans and large animals, sometimes under conditions where the objects are conducting some sort of physical exercise. 

Figure 14. Schematic picture of a whole body calorimeter with its ventilatory system, a, Fan b, steam c, saturator d, heater e, respiratory heater f, condenser g, respiratory condenser h, gradient layer. Adapted from J6quier et al. (1975).

Such calorimeters have been used to investigate the metabolism of animals (Lamprecht, 1985) and human beings (Tschegg et al, 1981) under different conditions (see also McLean and Tobin, 1987). To our knowledge, there is no commercial manufacturer of this type of device all presently existing whole-body calorimeters are unique constmctions of the respective research group. 

Third Example Adiabatic Whole-Body Calorimeter... 

Snellen, Chang, and Smith (1983) described a special adiabatic whole-body calorimeter for humans. The calorimeter consists of three metal cylinders inside one another. The iimermost cylinder (157 cm high, 152 cm in diameter) serves as a radiation shield. The other two cylinders (183 and 193 cm high, 168 and 193 cm in diameter) form the adiabatic shield against the environment. The calorimeter works as follows. A continuous air flow (26m min ) with exactly controlled temperature and humidity is injected into the calorimeter, and half of the flow rate between the first and the second cylinder and via the proper inlet slots goes into the... 

Technical description and performance characteristics of a human whole-body calorimeter. Med. Biol. Eng. Comput., 21,9-20. 

Modern equipment to measure HR limit the impairment to the subject. There are electrocardiograph tape recorders or telemetry systems to store the results of measurements. Finger clips with optical sensors for the blood pulse and some kinds of cuffs (like used to monitor the blood pressure) may be used to sense the heart rate over long periods. The individual relation between heart rate and EE measurements can be calibrated in whole body calorimeters as well as with mask calorimeters, performing different levels of activity. This calibration can later be used to estimate EE of free living subjects and/or over relatively long periods (up to some days). 

Whole body calorimetry is an important tool for physicians, physiologists and nutritionists. The application of calorimetry started about 200 years ago. Its theoretical base was established in the last 100 years. The technique of calorimeters and calorimetric methods have been largely improved until nowadays. Modern whole body calorimeters are very accurate and fast responding instruments. They reach recovery rates of about 100 3 % and a delay of measurement of as short as 3 min. Two calorimetric techniques are established, direct and indirect calorimetry. The former is the measurement of the heat loss of a subject the latter determines the heat production by metabolic processes. This gives a deeper insight into the metabolic status of the subjects. So indirect calorimetry is nowadays more frequently used than direct one. 

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