The practical induction of nitrous oxid-oxygen anesthesia by the methods now universally practiced still leaves undetermined the question of adequacy of the supply of oxygen to the patient.
The question as to availability of oxygen is rendered the more important by recent work which tends to establish the minimum requirements of oxygen in respiratory airs for efficiency in the normal individual. The experimental data of the United States Army School of Aviation Medicine prove that a normal man cannot long retain consciousness unless he breathes air of at least 6 per cent. oxygen.1 In the tests, it is assumed that the individual is exerting a minimum of muscular activity. He is not far from the normal basal metabolic level. By the least additional work, as by any sudden muscular acts, he quickly consumes the oxygen below the level necessary to retain consciousness. For less resistant individuals, either normal or pathologic,
GREENE CW, CURREY HM. THE RESPIRATORY GAS PERCENTAGES DURING NITROUS OXID ANESTHESIA IN DOGS. Arch Intern Med (Chic). 1925;35(3):371-378. doi:10.1001/archinte.1925.00120090084007