A closed circuit apparatus for measurement of oxygen consumption in small animals

A simple and reliable closed circuit apparatus for short term and long term measurements of oxygen consumption of small laboratory animals is described. Repeat measurements of oxygen consumption under resting conditions of six male albino rats using this apparatus shows a variability of less than 1.5%. Use of the set-up for continuous monitoring of oxygen consumption following subcutaneous injection of norepinephrine, for over 2.5 hr enables the measurement of energy expenditure in animals on a long term basis which is reproducible on several occasions.