GB1299311A - Method and apparatus for producing a mixture of gas and anaesthetic vapour - Google Patents

Abstract

1299311 Anesthetic apparatus CHEMETRON CORP 23 Jan 1970 [27 Jan 1969] 3478/70 Heading A5T [Also in Division F2] A mixture of a gas and the vapour of a liquid anesthetic is formed by passing a stream of gas through a vapourising region which communicates via a conduit with a liquid anesthetic reservoir, said gas stream not being passed through the reservoir, and by admitting pressurised gas to the reservoir at a point below the liquid surface to force the liquid anesthetic through the conduit, which also has one end below the liquid surface. The conduit preferably includes a section of capillary size with an internal diameter of about 0.007 inch. In a first mixture producing apparatus, Fig. 1, pressurised gas passes via a diaphragm type regulator 24 into an anesthetic reservoir 14 sealingly engaging a member 68. Further pressurised gas from the same or a different source, passes via a conduit 16 into a vapourising chamber 12 to a region therein below a porous metal divider plate 64. Liquid anesthetic passes via a conduit 20 and drip guide 58 onto the upper surface of plate 64 becoming vapourised and mixed with gas passing through plate 64, the mixture passing via a back pressure regulator 26 to a closed or open-circuit anesthetic mixture utilizing apparatus. A bleed conduit 54 between reservoir 14 and chamber 12 relieves excess pressure in reservoir 14 due, for example, -to a temperature rise. A conduit 53 between chamber 12 and regulator 24 compensates for minor pressure changes in chamber 12. A metering valve (96), Fig. 2 (not shown), may be introduced in the liquid flow conduit between the reservoir and vapourising chamber for controlling liquid flow rate, and the back pressure regulator may be omitted if the utilising apparatus is of a type which will maintain a constant pressure in chamber 12. In alternative apparatus, Figs. 4-7 (not shown) and Fig. 3, pressurised gas passes via a regulator 228, valve. 230 and conduit 182 into a reservoir 144, liquid anesthetic passing therefrom via a filter (192), Fig. 6, and a capillary tube (184) located within a tube 190, onto a porous plate 172 in a vapourising chamber 142. Gas from the same source passes via a valve 232 into the chamber 142, a gas/ vapour mixture passing via a conduit 150 and back pressure regulator 248 to utilisation apparatus. A differential pressure meter 252 indicates liquid anesthetic flow rate through tube (148). The valve 230 is a shut-off valve and valve 232 is a throttling valve, both valves being controlled by a single rotary member 244 in a dual valve 234, a member 240 being pre-adjusted so that both valves close simultaneously.