A Method of Measuring Oxygen Consumption and Minute Ventilation in Semi-Closed Circuit Underwater Breathing Apparatus

Abstract

A method of measuring both oxygen uptake (~~,) and ventilation (~') when breathing from a double counterlung semi-closed circuit underwater breathing apparatus is presented. The analysis requires a knowledge of the gas concentrations of oxygen and carbon dioxide in the inspired and expired counterlungs of the breathing set as well as the mass flow rate of gas injected into the apparatus. Values for~Ol and (' were obtained at pressures between 100 kPa and 1·1 MPa in moderate temperature (22-25"C) and very cold (about 4"C) water. The reliability and accuracy of the devised techniques were validated at 100 kPa by comparison to an open circuit measurement of VOl and Jiunder the same conditions of rest and work. Further confirmation of the accuracy or the method was established at depth by measuring the ventilation equivalent for oxygen (~)~01) during intermittent rest and work.