GB898114A - Improvements in or relating to respiratory apparatus - Google Patents

Abstract

898,114. Respiratory apparatus. DRAGER, O. H., [trading as DRAGERWERK, H. & B. DRAGER]. Jan. 11, 1961 [Jan. 11, 1960], No. 1258/61. Class 81 (2). In a closed circuit respirator the supply of nutrient gas to an inhalation mixture is determined by comparison of the oxygen content of the mixture with that of a standard. The functioning of the apparatus is dependent on the fact that, after carbon dioxide and moisture have been removed, the density of exhaled gas depends on its oxygen content. A breathing-bag 1 supplies inhalation gas through a connection 3 to a face mask, and exhaled gas is returned through a connection 4 to a carbon dioxide and moisture absorber 2 and thence passed back into the bag 1. Additional oxygen is admitted to the bag 1, from a pressurized source, through a control valve 15 and pipe 16. The contents of the breathing-bag 1 are continuously circulated, by a diaphragm pump 6 driven by a motor 7, through a duct 9 and constriction 11 while air of standard oxygen content is circulated from an auxiliary container 17 by a similar pump 5 through a duct 8 and identical constriction 10. Since the rate of flow of the gases through the constrictions depends on their densities, the pressures built up in the passages 8, 9 also depend on their densities and thus on their relative oxygen contents. These pressures are accordingly communicated through pipes 12, 13 to opposite sides of a diaphragm 14 and the system is so set that the valve 15 is opened by the diaphragm 14 as soon as the proportion of oxygen in the bag 1 falls below that in the container 17. In a suggested modification the equipment shown in the upper part of the Figure is replaced by means whereby the pressure applied to the upper face of the diaphragm 14 is dependent wholly or partly on the ambient pressure.