Calibration and performance of a small animal gradient layer calorimeter box

Calorimetry, using the gradient layer technique, has become well established in the study of energy metabolism. The use of a commercially constructed gradient layer box within a calorimetry system designed to measure directly and indirectly the metabolic sequelae of thermal injury in rats, is described. Variations in the signal output were discovered. These were found to be dependent upon:

1. stability of the ambient temperature
2. stability of the gradient layer box water jacket temperature
3. position and size of the calibrating heat source.

Calibration with heat sources which simulate the heat emission from a rat, established that a measurement accuracy of ±2% can be achieved by controlling (a) and (b)