A computer-controlled indirect calorimeter for the measurement of energy expenditure in one or two subjects simultaneously.

An indirect calorimeter is described with which it is possible to make recordings of oxygen uptake, carbon dioxide production and respiratory quotient in one or two subjects simultaneously. The gas analysers sample expired air from the two patients and room air in a continuous cycle which lasts 15 min; a microcomputer is used to switch solenoid valves, read the gas analysers and output the results to a printer. A butane lamp is described which is made from components of a camping cooker. This can be used to simulate two patients, and enables the operator to check the function of the calorimeter quickly and inexpensively. If there is an error in the system the printout indicates whether the fault is likely to be a leak or an error in a gas analyser.