Patent GB-813438-A (GB)
Title: Devices for facilitating breathing and producing artificial respiration
IPC: A61M16/00
Filed: 1956-05-23
Abstract: 813,438. Respiratory apparatus. STEPHENSON CORPORATION. May 23, 1956 [May 27, 1955], No. 15946/56. Class 81 (2). A resuscitator comprises a gas-administering chamber connected with a second chamber by a venturi passage but divided from the second chamber by a diaphragm carrying a valve housing having a valve chamber connected with a gas supply, first and second jets directed into the venturi passage being connected with the valve chamber by first and second passages respectively, and valve closure means mounted independently of the diaphragm to close either the first or second passage when the valve housing is moved in response to a predetermined positive pressure or a predetermined negative or zero pressure, respectively, in the gas-administering chamber, so that either the second jet drives gas from the gas-administering chamber to the second chamber or the first jet drives gas from the second chamber to the gasadministering chamber there being adjusting means for selecting the predetermined positive, negative or zero pressures. A casing, comprising a tube 10 and domed ends 12, 13, is divided by diaphragms 27, 28 into a top chamber 29 open to the atmosphere, a second chamber 30 provided with an air-escape valve 79 and a gasadministering chamber 31 which is connected with a face mask 16. A floating valve housing 36 is carried by the diaphragms 27, 28 and has a valve chamber 37 connected by upper and lower apertures 60, 56a with passages 63a, 63b and 56b, 56c, respectively, which are formed in the valve housing 36. One passage 56b, 56c is connected with chamber 57 in a nut 46 at the top of the valve housing 36 and thence to an upper jet 71 and the other passage 63a, 63b is connected with a lower jet 72, the jets 71, 72 being directed towards a venturi passage 39 connecting the second chamber 30 and the gasadministering chamber 31. Gas is supplied through a coupling assembly 11 and a flexible conduit 50 to the valve chamber 37. A valve closure 38 is supported by a resilient arm 51 which is secured at one end to the coupling assembly 11 and passes through the flexible conduit 50. In operation, with valve closure 38 closing the upper aperture 60 and the passage 63a, 63b leading to the lower jet 72, gas passes from the valve chamber 37 to the upper jet 71 and through the venturi passage 39 thus driving gas from the second chamber 30 to the gasadministering chamber 31 and causing the patient to inhale. The diaphragms 27, 28 rise and move the valve housing 36 axially so that the valve closure 38 opens the upper aperture 60 and closes the lower aperture 56a. Gas is then supplied only to the lower jet 72 and the venturi passage 39 thus driving gas from the gas-administering chamber 31 to the second chamber 30 and causing the patient to exhale. The diaphragms move downwards reversing the valve and the cycle is repeated. The closure 38 does not move relative to the valve chamber 37 until movement of the housing 36 is sufficient to build up a restoring force in the resilient arm equal to the gas pressure, the valve closure 38 then snapping over from one end of the valve chamber 37 to the other. Atmospheric air enters or leaves the second chamber 30 through an adjustable slot 75. The gas-administering chamber 31 has safety valves 25, 26. Adjustable spring means control the movement of the diaphragms 27, 28 and the valve housing 36 and thus permit the adjustment of the maximum and minimum pressures attained relative to one another and enable the apparatus to operate over different ranges of gas pressures.