The Rate of Elimination of Dissolved Nitrogen in Man in Relation to the Fat and Water Content of the Body1

Quantitative studies of the dissolved nitrogen in man have been previously made only for short periods of time, chiefly in determinations of cardiac output (Bornstein, 1919). Measurements of nitrogen absorption and elimination not only give an approximation of cardiac output, but also a’fford a representation of the absorption and elimination of all chemically inert gases, specifically the inhalation anesthetics. In connection with the decompression of divers studies of the dissolved nitrogen are of immediate practical importance. This paper presents the application of certain principles from studies of the dissolved nitrogen in dogs (Shaw, Behnke, Messer, Thomson and Motley, 1935) to measurements of nitrogen in man. METHOD. Inhalation of pure oxygen results in elimination of the gaseous nitrogen dissolved in the tissues of the body. Oxygen can be breathed for a period of 4 hours in a closed system consisting of a helmet, cooling coil, spirometer, and soda lime cannister. Analysis of periodic samples of the circulating oxygen supplies the data for calculations of nitrogen elimination. The volume of the system was 40 liters so that the oxygen percentage at the end of an experiment did not fall below 96 per cent. The term %itrogen” is applied to the residual gas in the Van Slyke apparatus after oxygen absorption with hyposulphite. The nitrogen measurements were made on 3 healthy men of medium build who interrupted their usual activities to breathe oxygen at weekly intervals while resting on a cot. RESULTS. Figure I-A is typical of the results from 25 experiments on the 3 men. The solid line represents the actual measurements of nitrogen elimination over a period of 4 hours on subject A. The broken line, drawn from calculations based on the experimental results, represents the nitrogen eliminated during the first 5 minutes (when oxygen replaced the air in the lungs and in the apparatus) and during the period following