The development of inhalation anaesthesia : with special reference to the years 1846-1900... / [Barbara M. Duncum].

Duncum, Barbara M.

Date:: 1947

Credit: The development of inhalation anaesthesia : with special reference to the years 1846-1900... / [Barbara M. Duncum]. Source: Wellcome Collection.

504/664 page 484

$averages, owing to the variations in pressure which must to some extent occur in the bags during the administration. All that I can say is that when both bags are kept partially distended, [Hewitt admitted that ' considerable practice is necessary to keep both bags equal in size throughout '] and one hole is Fig. 129.—REGULATING STOPCOCK OF HEWITT'S NITROUS OXIDE AND OXYGEN APPARATUS (c. 1893) O. oxygen bag. ON2 nitrous oxide bag. v and v'. flap-valves in the tubes, T and T. H. handle controlling the proportions of oxygen and nitrous oxide in the mixture, i. indicator on H, passing over D, dial. H'. handle of two-way stopcock allowing either air or the anaesthetic mixture to reach the facepiece. IV and EV. inspiratory and expiratory valves. open, a very small percentage (something between 3J and 6^ per cent.) of oxygen will come through, and that each additional hole turned on represents something like an additional 1 per cent, or i\ per cent, of oxygen. . . . The apparatus here described allows (1) air, (2) nitrous oxide, or (3) nitrous oxide mixed with a proportion of oxygen, to be freely respired through valves at the will of the administrator.' 1$