Patent GB-882365-A (GB)
Title: Improvements in lung ventilating apparatus
IPC: A61M16/00
Filed: 1959-12-01
Abstract: 882,365. Respiratory apparatus. AIR-SHIELDS Inc. Dec. 1, 1959 [Dec. 5, 1958], No. 40735/59. Class 81 (2). In forced breathing artificial respiration apparatus having automatic timing means, provision is made for immediately setting the apparatus to the positive pressure phase when the patient attempts to inhale. The timing device is shown in Fig. 2 and comprises a chamber 59 into which air or gas is fed from the main supply pipe 42, through a choke 55 and adjustable needle valve 68. When the internal pressure reaches a predetermined maximum its action on a diaphragm 58 opens a ball valve 61 so that the feed duct 54 is vented to atmosphere through an outlet 67. The chamber 59 is also vented through the duct 54 and its internal pressure leaks away past valve 68 until the spring 63 can again close valve 61, whereupon the cycle is repeated. The variations in pressure in the duct 54 are imposed on a diaphragm 51 and, during the time that valve 61 is closed, the diaphragm 51 is held down to close a ball valve 44 against its seating 46. However, while the duct 54 is vented to atmosphere, the diaphragm 51, and the ball 44, are raised by a spring 48 and the supply pipe 42 is connected to a further pipe 40 which communicates the pressurized supply to the breathing-equipment. In the closed position of the valve 44 the pipe 40 is vented to atmosphere through the upper seating 47 and an outlet 50. The pipe 40, Fig. 1, is connected to a cylinder 38 so that, when pressure is applied, a piston 39 is raised, causing compression of a bellows 24 and, by raising the pressure in a closed chamber 20, causes compression of the pumping bellows 21. The interior of this bellows is connected to the breathing-mask 5 through oppositely directed non-return valves 32, 36. Thus gas is forced into the patient's lungs when the bellows 21 is compressed and withdrawn when the bellows is expanded by a weight 26 on bellows 24. The device for assisting the patient, on spontaneous inhalation, comprises a diaphragm 81, the upper and lower sides of which are connected respectively upstream and downstream of the one-way valve 36. During exhalation, under artificial respiration conditions, the pressure in connecting duct 82 is lower than that in duct 83 and the diaphragm 81 is held in its lowermost position. However, if the patient makes a spontaneous effort at inhalation during this phase there is an additional rarefaction in the tube 17 and, owing to the resistance of valve 36, the pressure above diaphragm 81 becomes lower than that below it. The diaphragm is consequently raised and opens a valve 78 which vents a pipe 71 to atmosphere through duct 77. The further end of this pipe is connected to the duct 54, Fig. 2, and the venting of the latter duct immediately opens valve 44 and initiates an inhalation phase. Other features of the apparatus described include a stop valve 73, for providing entirely automatic timing of the respiration cycle, and the provision of a carbon dioxide absorber 9. Anaesthetic or other gases may be connected through a pipe 86 so as to feed into the delivery duct through a connecting pipe 85 but, when a turncock 14 is turned clockwise through 90 degrees, to isolate the patient from the forced respiration apparatus, the patient is then connected to a normal breathing-bag 91 and the gas supply pipe 86 is connected into the system through a duct 90. Reference has been directed by the Comptroller to Specification 781,747.