GB1193522A - Improvements in Apparatus for Use in the Administration of Anaesthetics - Google Patents

Abstract

1,193,522. Anaesthetising apparatus. B. R. SUGG and J. PARKHOUSE. 19 June, 1968 [26 June, 1967], No. 29448/67. Heading AST. [Also in Division, F2] An apparatus for administrating anaesthetics comprises a first vaporizer 1 for use in both a draw-over system and a plenum open-circuit system, a second vaporizer 2 for use in a plenum closed-circuit system, said vaporizers being mounted in the main carrier gas flow path which begins at medical gas cylinders 3 and 4 and passes through flowmeters 5 to two-way valve 7 which is operated in concert with twoway valve 8, said valves 7 and 8 constituting a first valve means by which carier gas is selected to flow via either vaporizer 1 or 2. Gas line 9 leads from the atmosphere to the main gas flow path via one-way valve 10 and reservoir 11. Downstream of valve 8, the gas flow path continues as line 12 and has branches connecting with breathing bag 15 and bellows 13. Line 12 leads to breathing mask 18. Exhalation line 20 leads via non-return valve 21 tO a two-way valve 22, which is adjustable to direct exhalation either to the atmosphere via valve 23 or back into gas flow line 12 via line 24 and sodalime canister 25. Said valve 22 constitutes the second valve means of the apparatus, which is adjustable in a single action with the aforesaid first valve means, in such a manner that the apparatus may be operated as a draw-over system, a plenum open-circuit system or a plenum closed-circuit system. Emergency oxygen line 26 is connected between gas cylinder 4 and gas line 12 downstream of valve 8. In the draw-over system, the gas flow from cylinders 3 and 4 is shut off Air, to which a proportion of oxygen may be added, is drawn in through valve 10 and passes through vaporize 1, through gas line 12 to the patient and thence to the atmosphere through valve 22. In the plenum open-circuit system, pressurised carrier gas is fed from cylinder 3 and/or cylinder 4 through valve 7 to vaporizer 1 and thence as in the draw-over system. The back pressure of the carrier gas holds one-way valve 10 closed. If the carrier gas supply fails or its rate falls below the patient's minute volume, valve 10 automatically opens to admit air. An oxygen failure warning device is preferably incorporated in the apparatus. In the plenum closed circuit system., the flow of pressurised carrier gas flows through line 6 to valve 7 and vaporizer 2 and thence to face mask 18. The exhalation passes through valve 22 through canister 25 to gas line 12. Valve 23 enables the patient's lungs to be expanded by operating bellows 13 manually or by powered means, whereupon the small bellows in valve 23 expands and shuts the valve. When the bellows 13 is raised to refill with air, valve 23 opens and expiration from the patient's lungs occurs.