Oxygen Cost of Forced Breathing in the Submerged Resting Subject

¹ From the Laboratory of Physical Biology, National Institute of Arthritis and Metabolic Diseases, National Institutes of Health, Bethesda, Maryland

Oxygen cost of forced breathing in the resting subject ‘in air’ and submerged was determined. The oxygen cost of increased pulmonary ventilation was measured by determining the difference in total oxygen uptake in the resting subject during normal breathing, and during forced breathing produced by inserting a dead space between the subject and a conventional metabolimeter to produce a self-regulating CO₂ stimulus. The resting oxygen consumption was markedly affected by the degree of relaxation permitted by the resting position. Since even basal metabolism is known to vary with such factors as time of day, time from last meal, mental state, etc., appropriate pretesting procedures and control tests were used and are shown to be critical for correct interpretation of the data. The information thus obtained indicated that the oxygen cost of forced breathing submerged was approximately twice that measured ‘in air’ at increased pulmonary minute volumes of from 40 to 60 liters per minute greater than resting volumes.