Analytical refinements in animal calorimetry.

An analysis is presented of a system for indirect calorimetric measurement. Emphasis has been placed upon problems associated with the use of large climate-controlled chambers. The dynamics of gas exchange and the influence of ambient conditions on various parameters have been subjected to physical analysis which has led to the following conclusions: 1) Fast-response measurement of heat production can be achieved even if the size and hence washout time of the chamber is large. 2) Accurate continuous measurement of heat production over long periods, without correction for changes in barometric pressure, is possible if suitable instrumentation is chosen. 3) A method for calibration of a paramagnetic oxygen analyzer achieved high accuracy at low cost. 4) The entire system has been checked by simulation of gas exchange in the chamber, by injection of nitrogen at a known rate.