An Early Study of the Oxygen Cost of Breathing

Norman Jones

Abstract


Dr Roy Shephards 1966 paper The oxygen cost of breathing during vigorous exercise (Shephard, 1966) is revisited. At the time of the study, modern understanding of the mechanical work of breathing had been established, but estimates of the associated oxygen cost were found to be variable. At least in part, the variability could be ascribed to differences in the method adopted to increase breathing (voluntary hyperventilation, carbon dioxide-driven, added instrumental dead space) and a lack of precision in the measurement of small inspired-expired oxygen concentration differences. An experimental design was adopted to minimize the effect of such factors. The results suggested that during heavy exercise, at ventilations less than 90 l/min, the oxygen cost of breathing was less than 2 mL/min/L minute ventilation, but at higher ventilation induced by hyperventilation at breathing frequencies of 50 and 100 breaths/min, the oxygen cost increased to 4 mL/min/L minute ventilation. The study remains a model of carefully conducted physiology. Even after several decades, controversy remains as to whether the oxygen cost of breathing contributes to exercise limitation in healthy subjects and patients with obstructive lung disorders (COPD).

Keywords


respiratory physiology, medicine

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ISSN: 19206216