Patent GB-851997-A (GB)
Title: Improvements in apparatus for supplying and exhausting or exchanging a controlled volume of gas
IPC: A61M16/00
Filed: 1957-01-18
Abstract: 851,997. Artificial respiration apparatus. STEPHENSON CORPORATION. Jan. 18, 1957 [Jan. 18, 1956; Jan. 8, 1957], No. 1980/57. Class 81(2) Artificial respiration apparatus comprises a gas container which is expansible and collapsible by means including fluid pressure, is connected by conduits to the patient and a gas supply, respectively, and has first and second valves respectively, for venting the container when the pressure exceeds a predetermined amount and permitting a supplementary gas supply when the container pressure falls below a predetermined amount there being stops between which means on the container move to determine the volume of gas supplied by and withdrawn by the container, contact between these means and the stops causing reversal in the. direction of movement of the container. Anaesthetic or oxygen is supplied continuously to two interconnected collapsible and expansible containers 10, 1 1 through a conduit 18, the chambers 10,11 being connected to a face mask, endotracheal tube or tracheotomy tube by a second conduit 12. The lower container 10 is fixed at the top to a cross member 22 mounted on hollow columns 26 carried by a base 24. Pistons 27 in the columns 26 are attached by rods 25 to a movable platform 28 which is fixed to the lower end of the container 10. Compressed gas flowing through a conduit 40, controlled by an adjustable needle valve 32, when a valve member 44 is unseated causes the pistons 27 and the movable platform 28 to rise thus collapsing the container 10. When the valve member 44 in the compressed air conduit is seated the container 10 expands due to the weight of the movable platform 28 which. may be aided in an alternative construction by air pressure applied on the top of the pistons, air beneath the pistons 27 being exhausted through a conduit 42 controlled by a needle valve 34. As the container 10 expands the platform 28 strikes, a plunger 60 of a spring urged piston 58, air in the piston chamber 50 being expelled through a conduit 52 controlled by a needle valve 36, the expansion of the container 10 thus being resisted according to the adjustment of the needle valve 36 so that the pressure in the container 10 is substantially constant for a period to effect a pause between exhalation and inhalation in the breathing cycle. A similar device (not shown) may be disposed on top of the platform 28 which device on engaging the cross member 22 produces an interval between inhalation and exhalation in the breathing cycle. A valve v which includes the valve member 44 is controlled by a toggle mechanism connected with a control rod 64. Collapse of the container 10 is limited by engagement between a lip 74, which is attached to the platform 28 and is slidable on the control rod 64, and an adjustable stop 80 on the control rod 64, such engagement raising the control rod 64 to reverse the toggle mechanism and operate the valve v so that the compressed air supplied to the columns 26 beneath the pistons 27 is cut off by seating the valve member 44. The inhalation phase of the breathing cycle is thus terminated. Expansion of the container is similarly limited by engagement between the lip 74 and a fixed stop 78 which causes lowering of the control rod 64 so that the valve member 44 is unseated to permit supply of compressed air to the hollow columns 26 and terminate the exhalation phase of the breathing cycle. The control rod 64 may be locked in raised or lowered position by moving a dial 82 to end automatic operation of the device. The upper container I is connected to the lower container 10 by a tube 90 having a safety valve assembly 91, an upwardly opening valve 98 and a downwardly opening valve 100. The opening pressures of valves 98, 100 are controlled by counterweights w movable along arms 114 associated with them to determine the positive and negative pressures which may be created in the lower container 10 during the inhalation phase. The valves 98, 100 may be locked in open position if the device is to be operated manually by alternately expanding and collapsing the upper container. The container 11 remains stationary when the apparatus is operating satisfactorily, any collapse or expansion of the container 11 indicating the need for adjustment of the valves 98, 100. If the upper container expands or collapses by more than a predetermined amount a valve 170 is opened for the escape or admission of gas respectively. A bleed valve (not shown) which opens during expansion of the lower container 10 may be provided for the passage of exhaled gas to the upper container 11 or to the atmosphere so that the amount of gas supplied to and received from the patient is maintained substantially constant.