Patent GB-1498211-A (GB)
Title: Positive pressure breathing circuit
IPC: A61M16/08
Filed: 1975-02-05
Abstract: 1498211 Respiratory apparatus B R PALUCH 5 Feb 1975 [18 March 1974] 4896/75 Heading A5T [Also in Division B2] The exhalation tube 12 of a breathing circuit 10 is concentrically arranged about the inhalation tube 14 so that the temperature of gas flowing to the patient through tube 14 is stabilised without any extraneous source of heat, there being also an inflatable means 38 positioned between the tubes 12, 14 and in fluid communication with a source of pressurised fluid so that the means 38 is inflated during inspiration to block the expiratory tube and is deflated during expiration to permit passage of exhaled gas through the tube 12. The circuit 10 is connected to a positive pressure ventilator, the exhalation tube 12 including a tubular member 21 and the inhalation tube 14 including a tubular member 22. The means 38 comprises a cuff which is secured to member 22 and communicates with an inflation duct 36 in member 22, the duct being connected to a gas supply port of the ventilator so that the cuff is inflated and deflated as the ventilator cycles. A oneway valve 52 is provided within member 22 and comprises a ring 53 supporting a rib member 54 carrying a membrane 55 which seats against the ring 53 during exhalation and is unseated therefrom during inspiration. A membrane 50 located about member 22 provides a one-way valve in tubular member 21, cooperating with a valve seat 34 defined by a groove formed on member 21. Apertures 44 adjacent a connection 41 for a patient's face mask and downstream of valve 52 provide communication between the inhalation and exhalation tubes. A nebuliser (60) is detachably mounted on tubular member 21 with its outlet port 68 in register with a port 47 of tubular member 22. The nebuliser comprises a body (77) which floats on liquid, e.g. medicament, contained in the nebuliser, and has a channel 79 through which the liquid is aspirated by gas supplied through flexible hose 85 and atomising gas duct 90, 28 which is connected to a gas port of the ventilator so that atomising gas is supplied only during the inhalation phase of the ventilator. The aspirated liquid is atomised by striking a ball 83 positioned above channel 79. The ports 68, 47 are each controlled by shutters which are automatically moved as the nebuliser is mounted on the tubular member 21.  The end of the circuit distal from the patient may be connected to a humidifier 117 containing a water chamber 121 into which extends a tube 128 supplying breathing gas from the ventilator. A port 118 of the humidifier is coupled to inhalation tube 14 and a port 123 receives exhaled gases from tube 12 whereby heat from the exhaled gases warms the water and hence the inspiratory gas. The humidifier may be formed with heat-exchanging fins or contain metallic wool. A drain port 105 may be provided in the exhalation tube for drainage of condensed fluids therefrom.  The portion of the circuit upstream of members 21, 22 may comprise tubes having smooth or corrugated walls and the wall of the inspiratory tube may be provided with a helically wound wire to provide rigidity.