VOLUNTARY BREATHHOLDING. I. PULMONARY GAS EXCHANGE DURING BREATHHOLDING 1

Abstract

While weighing subjects completely submerged under water, with the breath held, the authors found that the subjects gained wt. (lost buoyancy) at a constant rate throughout the period of breathholding. The underwater wt. change amounted to from 200-500 gs. per minute, depending upon size of the individual and the tension of O2 inhaled preliminary to underwater breathholding. It was demonstrated that the wt. change is due to a decrease in the vol. of gas in the lungs during breathholding which, after 100% O2 inhalation, is only 20-25 ml./min. less than the total O2 consumption of the body. By studying serial changes in the arterial blood gases and pH, it was found that during breathholding oxygen moves readily from the lungs to the blood while only small amts. of CO2 move into the lungs, the greater portion remaining dissolved in the blood and tissue fluids. Since during breathholding the major portion of the change in lung volume is due to movement of O2 from the lungs into the blood and tissues, it was possible to follow the rate of exchange of O2 between the lungs and blood by means of underwater weighing. It was found that the rate of diffusion of O2 during breathholding is closely related to the oxygen tension of initially inspired air. After inhalation of 100% O2, the rate of diffusion of O2 approximated the O2 consumption of the body and maintained a normal O2 saturation of arterial blood throughout breathholding. With 10% O2 inhalation, O2 diffusion lagged behind O2 consumption and the arterial O2 saturation fell rapidly.