Effects of Raised Barometric Pressures on Respiration in Man¹

Abstract

Abstract H esser , C. M. and B. H olmgren . Effects of raised barometric pressures on respiration in man. Acta physiol. scand . 1959. 47. 28—43. – The effects of raised barometric pressures (up to 4.0 atm) on various respiratory functions, hitherto largely neglected, were studied on 8 healthy subjects at rest in a recompression chamber. The independent effects of changes in inspired oxygen and nitrogen pressures were studied by comparing data obtained on air, 100 % oxygen, and 5 % oxygen in nitrogen at various ambient pressures. Breathing air with increasing ambient pressure, respiration became progressively slower and deeper, whereas at 4.0 atm the effective alveolar ventilation was slightly increased. Other observations at 4.0 atm were: Average increase of 33 % in tidal volume; average decreases in respiratory rate of 27 %, respiratory minute volume of 10 %, and functional dead space/tidal volume ratio of 9 %; no demonstrable changes in expiratory reserve volume, functional dead space and respiratory exchange ratio. Evidence is presented that the respiratory changes were caused by the combined effects of increased oxygen tension and of increased breathing resistance due to increased gas density. Thus, nitrogen at high pressures (up to 3.8 atm) exerted little, if any, depressant action on respiration.