Patent GB-1532011-A (GB)
Title: Ventilator
IPC: A61M16/00
Filed: 1976-01-23
Abstract: 1532011 Ventilators F M BIRD 23 Jan 1976 [27 Jan 1975] 02692/76 Heading AST A ventilator comprises a sequencing cartridge 238 controlling cycling of the ventilator and including a diaphragm-controlled valve 247 controlling gas flow from an inlet 237 to an outlet 248, the inlet receiving gas from an oxygen-air blender 33 through a filter 61 and control switch 69. The blender also supplies gas to demand valve 103, a flow accelerator cartridge 258 and an apneustic plateau cartridge 317, each of which includes a valve member operated by a diaphragm. The outlet 248 of cartridge 238 is connected via an inspiratory flow rate control valve assembly 358 with the main passage 188 of a master venturi 181 communicating with a socket 227 connected in the patient's breathing circuit. Operation of the breathing circuit is triggered by inhalation of the patient at mouthpiece 484, which inhalation is sensed in a sensing venturi 216 and communicated to one side of diaphragm 240 of control cartridge 238 thereby opening valve 247 and permitting gas flow to central passage 188 of the master venturi. Additional gas may be drawn in through secondary jets 189 from a reservoir 174 and air may be drawn in through filter 156. Gases passing through the venturi passage 191 open valve 198 and pass through socket 227 and tube 476 to nebulizer 482 before passing to mouthpiece 484. Gas is also supplied via tee 362 to socket 378 connected to a tube 478 coupled via tee 491 and tube 492 to an exhalation valve 486 to maintain this valve closed during inhalation. Gas also flows to the secondary jets of the venturi via an apneustic flow time control valve assembly 333 and this gas is also supplied through tube 329 to one side of diaphragm 326 of the normally closed apneustic plateau cartridge 317. Simultaneously with gas flow to the main passage 188 of the master venturi gas is supplied to flow accelerator cartridge 258 through adjustable orifice 289 controlled by a needle valve which opens only if pressure within chamber 298 reaches a value sufficient to overcome the force of its loading spring. At a predetermined pressure in the breathing circuit sensed by venturi 216 and communicated to sequencing cartridge 238, valve 247 closes. A low "topping up" flow of gas to the breathing circuit continues during the period of apneustic hold. When inspiratory pressure is applied to diaphragm 326 of apneustic plateau cartridge 317 valve 322 opens to permit gas flow to a manifold 346 which holds a check valve 353 closed. If the apneustic plateau cartridge fails, valve 353 opens under the pressure of gases from the flow rate control valve 358. A similar check valve 373 opens only if there is insufficient apneustic flow. Apneustic flow gas in manifold 346 is supplied through expiratory time control valve 399 to expiration terminating cartridge 413 to hold this cartridge closed, and through expiratory flow gradient delay assembly 387 to expiratory flow gradient delay cartridge 447 to hold it closed. When valve 247 closes gas in chamber 327 of the apneustic plateau cartridge bleeds down through jets 189 and valve 322 closes. Until this happens gas flows to manifold 346 from which a gas flow via restricting orifice 368 to socket 378 is maintained to hold the exhalation valve closed. Flow accelerator cartridge 258 closes immediately after valve 247 of sequencing cartridge 238 closes thereby terminating the inhalation phase. When valve 322 closes gas supply to socket 378 ceases and the exhalation valve closes, gases being exhaled through vapour trap 487. Gas flow to chambers 413, 417 of cartridges 413, 417 ceases and gas in these chambers bleeds down slowly and, if an inspiratory attempt is not made by the patient, pressure falls sufficiently to allow spring 431 to open valve 434 whereby source gas flows via lines 421 and 429 to sensing venturi 216, this gas flow creating a sub ambient pressure which is communicated to the sequencing cartridge 238 to open valve 247 and recommence the breathing cycle.