A low-cost modular oxygen-consumption device for small animals.

This paper describes a simple apparatus enabling the O2 consumption of small animals to be monitored. The system consists of a sensitive solid-state pressure transducer linked via a relay to a small peristaltic pump. While the animal breathes air in its closed chamber the CO2 expired is removed by an absorber; hence the pressure falls. The signal is sensed by the transducer triggering the pump to deliver a set volume of O2 to the chamber. The number of pump operations per unit time necessary to keep the system equilibrated is a measure of the O2 consumption rate. Each device is built as a module, up to four being mounted in one assembly controlled by a microcomputer. A balance control, priming switch, pump-volume setting, and electromagnetic counter are built into each front panel. Calibration is achieved be removing a known volume of air from the system with no animal present and counting the number of operations to return the chamber to equilibrium.