A Respirometer for Use in the Field for the Measurement of Oxygen Consumption. ‘ The Miser ’, a Miniature, Indicating and Sampling Electronic Respirometer

Abstract

A respirometer system for the measurement of oxygen consumption in the field is described. The design is based on well-tried principles. The system consists of three parts: a photoelectric version of the Wright gasmeter, a control unit incorporating volume counter, timer and display, and a vacuum sampler. The instrument is compact, weighing about 600 g, and robust. It is powered by rechargeable cells and has an endurance of about 8 h of continuous running. The sampler consists of an evacuated aluminium container and flow regulator carried on the control unit. Sub-samples of any desired volume are taken at isovolumetric intervals, ensuring that the whole sample is representative of the total expired air. The operating of the instrument is simple, sampling rate and sub-sample volume are set on the basis of expected minute ventilation and the desired duration of the measurement. There was little difference between [Vdot] _{o 2} measured with the MISER and that using the conventional Douglas bag method. In experiments in which the [Vdot] _{o 2} was measured using the MISER in series with a conventional Douglas bag, there were no significant differences in the F_{E 0 2} between the two, and the MISER's gasmeter was calibrated in similar experiments at [Vdot] _E between 15-30 1 min₋₁