Energy Cost of Breathing Determined With a Simplified Technique

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

Data on the energy cost of breathing, determined with a simplified technique, are presented. The ventilatory volume was self-regulated at various levels by requiring the subject to rebreath through various dead space volumes at a predetermined breathing rate. The dead space was inserted between the subject and a Sanborn Metabulator by which the oxygen consumption was measured. With this very simple apparatus consistent results were easily and quickly obtained. The pulmonary minute volume and O₂ uptake at higher ventilatory volumes are expressed as increments over the resting levels, which appeared to reduce the scatter of the points on a two-dimensional plot, and therefore produced a simplification of the curve of best fit Extrapolation of such a visually fitted curve for a single subject showed the cost of resting ventilation to be .5 cc/l. The energy cost of breathing at 50 liters ventilation was .8 cc/l., and that at 80 liters 2.0 cc/l.