Patent GB-1489562-A (GB)
Title: Respirator systems
IPC: A61M16/00
Filed: 1974-10-01
Abstract: 1489562 Respiratory apparatus CHEMETRON CORP 1 Oct 1974 [2 Oct 1973] 42473/74 Heading AST [Also in Division G3] A lung ventilator comprises a breathing gas delivery cylinder 10 divided by a piston 24, which is mounted for displacement under gravity, into a control chamber 26 and a delivery chamber 28, vacuum producing means in the control chamber 26 for lifting the piston to expand the delivery chamber 28, vacuum releasing means to enable the piston 24 to contact the delivery chamber and a control system operable to control the vac uum producing means and the vacuum releasing means whereby periodically and alternately to draw gas into the delivery chamber and to discharge the gas so drawn in. The piston 24 is secured to a rolling diaphragm 18 which is peripherally clamped between upper and lower portions 12, 14 of the cylinder to seal the chambers 26, 28 from each other. The piston 24 is annular and surrounds a guide shaft which is open through the top and bottom of the cylinder and accomodates a chain 30 secured between the weight 24 and a pulley 32. The chain 30 follows the motion of the piston 24 and, in association with a cable 38 and a potentiometer 40, gives mechanical and electrical indications of the weight and thus the volume of the delivery chamber upper and lower bellows 42, 44 surround the guide shaft and are sealed to the piston 24 and the top and bottom of the cylinder respectively to isolate the chambers from the shaft. The control chamber is evacuated by a vacuum pump 104 under the control of a solenoid-operated lift valve 98 to raise the weight and permit gas e.g. air, anaesthetic and/or oxygen to enter the delivery chamber through an inlet 46, the solenoid 100 of the lift valve 98 being energized by a logic control circuit according to a preset programme. Similarly a solenoidoperated lowering valve 108 connects the control chamber 26 to atmosphere through a bleed valve 118 to release the vacuum and allows the piston 24 to fall to discharge gas through an outlet 50 from the delivery chamber 28 to the inspiration chamber 136, figure 2, of a breathing manifold 138 connected with the patient for inspiration. The gas discharged may be passed through a nebuliser by a pump 156 under the control of a solenoid-operated nebuliser valve 162, the operation of which is synchronised by the logic control circuit with the lowering valve solenoid 110. The gas entering the delivery chamber may be supplemented with oxygen in a percentage controlled by a metering valve 88 on operation of a switch 92 through a solenoid-operated valve 70 which only opens when the weight is lifted. An inspiration lockout valve 124 is closed by atmospheric pressure entering its operator 146 under the control of a solenoid-operated lockout control valve 144 in response to a below ambient pressure created in the gas delivery conduit 126 caused by a patients spontaneous inhalation demand during an exhalation or inhalation hold part of the breathing cycle. Exhalation is controlled by a balloon valve 182 which is inflated during inhalation to close an inhalation passage 174 in the manifold 138, under the control of a solenoid operated expiration control valve 184 which supplies air from the vacuum pump 104 via a duct 190. The vacuum pump also supplies air via a duct 204 to a venturi 198 under the control of a solenoid-operated valve 202 to assist exhalation by reducing pressure in the exhalation chamber 176 of the manifold. Switches 218, 220, 222, 224 and 226 sensitive to pressure in the inhalation chamber 136 of the manifold provide monitoring override or audible or visual alarm signals if the maximum delivery pressure during inhalation is insufficient, if the pressure generated by the patients spontaneous inhalation is sufficient to override automatic cycling or if the maximum pressure generated in normal breathing cycles or a sigh breathing cycle is exceeded. The device mav be operated manually by operating a switch 366. The ventilator is controlled by logic circuits (see Divisions C3).