US2553446A - Apparatus for mixing the vapor of a volatile anesthetic - Google Patents

Description

y 5, 1951 w. EDMONDSON ET AL 2,553,446

APPARATUS FOR MIXING THE VAPOR OF A VOLATILE ANESTHETIC Filed Nov. 30, 1949 3 Sheets-Sheet 1 May 15, 1951 w. EDMONDSON ET AL 2,553,446

APPARATUS FOR MIXING THE VAPOR OF A VOLATILE ANES'II-IETIC "May 15, 1951 w. EDMONDSON ET AL 2,553,446

APPARATUS FOR MIXING THE VAPOR OF A VOLATILE ANESTHETIC Filed Nov. 50, 1949 3 Sheets-Sheet 5 Inventor Patented May 15,1951 v T5.

APPARATUS FOR MIXING THE VAPOR OF A VOLATILE ANESTHETIC William Edmondson and Wilfred Jones, Oxenhope, Keighley, England Application November 30, 1949, Serial No. 130,293 In Great Britain October 27, 1948 3 Claims. 1

This invention relates to apparatus for mixing the vapour of a volatile anaesthetic such for example as trichlorethylene with air for inhalation purposes by a patient.

Existing apparatus for the purpose is open to the objection that the percentage of trichlorethylene in the trichlorethylene air mixture increases with increasing temperature owing to the increase in the vapour pressure of the liquid trichlorethylene with temperature.

The present invention has for its object to introduce a device which as the temperature of the apparatus rises, reduces the area of an orifice through which concentrated trichlorethylene air vapour issues while keeping constant, or increasing the area of an orifice through which the diluting air is drawn.

According to this invention the apparatus comprises a vessel in which a quantity of the liquid can be placed, the said vessel being provided with an air inlet for providing air for vapourizing the anaesthetic liquid, the apparatus being provided with a diluting air inlet and a temperature controlled device which as the temperature of the apparatus rises from any cause automatically reduces the orifice through which the concentrated volatile anaesthetic air vapour issues while keeping constant or increasing the area of the orifice through which the diluting air is drawn during inhalation through a suitably arranged inhalation outlet. The liquid may be absorbed by means of a wick or other absorbent contained in the vessel. The thermally operated device may be arranged to provide for automatically altering the relative areas of the orifice through which the concentrated volatile anaesthetic air vapour issues and the area of the orifice through which the diluting air is drawn during inhalation.

In order that the said invention may be clearly understood and readily carried into effect, the

same is described more fully with reference to the accompanying drawings, in which:

Fig. 1 is a section of one form of appliance for carrying out the invention.

Fig. 2 is a similar view showing a preferred form of appliance.

Fig. 3 is a section taken on line 33 of Fig. 2 looking in the direction of the arrow.

Fig. 4 is a front view of the appliance and Fig. 5 is a diagram showing the circuit flow.

A form of appliance for carrying out the invention comprises a casing A fitted at one end with a perforated annular plate B which forms .a centralizing device and holder for a wick tube C that is packed with a wick D or body of absorbent material that may extend from the bottom of the tube to within a short distance from the top say for example about an inch. The opening in the bottom of the wick tube may be contracted by a conical ferrule C which is fixed therein, and, fastened to the'perforated plate, which may be slightly larger in diameter than the casing is a cap E which may be formed with a circle of holes E in the bottom and with a ring of holes lilaround its periphery, and such cap may be fitted with an annular tray E which may be dished and formed with a flange E which extends around its opening and contacts with the end of the cap. Fixed to the upper end of the Wick tube is an annular plate C in which is centrally fixed a mixing tube F of smaller diameter than the wick tube that projects through an opening in the top of the casing. Situated within this tube is a small tube G fitted at the bottom with a plate G that rests on the top of the Wick and formed in the tube immediately above such plate is a lateral opening G above which is a circular baffle plate G Fixed on the upper end of the small tube G is a flanged collar G that rests on a shoulder F in the mixing tube and screwed into such collar is a nipple H that terminates at its upper end in a point H This nipple is formed with a central bore H with a lateral opening H which communicates with a dished recess G in the top of the flanged collar. The latter together with the pointed nipple forms the bottom of a chamber for a sealed glass phial J which may contain trichlorethylene.

The top of the casing is closed by a cover through which the phial containing portion of the tube passes and such cover is formed with a central recss to receive a nut K which screws onto a threaded portion of the tube F and clamps a plate L together with a portion of the cover A between itself and a shoulder or abutment on the tube. diametrically arranged lugs L L Pivoted in the lug L is a forked lever M which spans the mixing tube F and is provided at its free end with a cross bar M which extends through the prongs of the fork and forms an abutment for a very short arm N of a bell-crank lever that is formed with a long arm N which is situated between the casing A and the mixing tube F and is provided at its free end with a valve plate N which operates in conjunction with a seating F that is situated opposite to a lateral opening F in the tube and may form part of the wall of a cham This plate is provided with two this rod is also conical as shown at O or rounded and is supported in a bearing .0 which may form part of a screw that is screwed'into aztapped hole in the perforated annular plate B.

To utilise the apparatus a glass phial .of trichlorethylene may be placed in the chamber and the cap screwed down until the sharp .point breaks the glass. The liquid thus .rel'eased. runs down the small tube and is absorbed by the wick.

If the latter has already been saturated'excessliquid will drain out through the holes at the bottomof the casing.

.Alternatively the .filling may be effected by .usingthecap at the top .of the phial chamber. as

.a measuring device for measuring theliquid.

Having charged the apparatusxthe inhalation outlet A is connecteddirectlyto a mask which the-patient appliesto his face, or it is connected :to'oneend of. a flexible tube at the other end of .whichis anon-return valve and an exhalatory 'valveunit to which .is attached'the face .mask. Whenthe patient inhales, air is drawn through "the perforated annular plate and a portion of such air passes through the: perforations without .coming into contact with the liquid. Some of the air passes through the wick and picks up a highconcentration of the liquid vapour.

This

mixture enters the mixing tube and issues be- .tweenthe seating and the valve plate and then mixes withthe outer stream of clear air.

The relative areas of the air holes in the-per- -forated plate and of the annular area between the seating and the valve plate are so adjusted thatat a given temperature the desired mixture is obtained. 7

If now the temperature and therefore the vapour'pressure of the'liquid rises, the area of the annular orifice is reduced.

The casing which may be made of brass expands while the length of the rod remains approximately the same. Although the valve plate is tended to be pushed on to its seating by the spring, it ishowever held in a certain positionthrough theacti-on of 'the lever mechanism andthe practically nonexpanding rod but as the length of the casing increases the spring causes the valve plate to move towardsthe seating'thusreducing the annularor-ifice area until the levers are again pressing: upon the pivot of'therod.

This reduction of the area of the orifice passing strong trichlorethylene vapour will cause a 'reduction of the proportion passing into themix .ture: and will thus compensatefor the increased strength of this vapour .due .to the increased :vapour pressure of the trichlorethylene.

The preferred form of appliance shown .in Figs. 2 and for carrying out the invention .com-

:prises a.rectangular.case I to the base of which is "attachedat .0118 end a vapourizingchamber 2 .which'is packed with a wick 3 or thelike and :contains vbafiles '4 to prevent splashing of the liquid anaesthetic.

This vapourizing chamheris also-fitted with av tube 5at right angles or there- .abouts to the chamber for charging with the :anaesthetic.

The inlet-iof .:this::charging tube .is

-so arranged that when the instrument hori 4 zontal only a definite volume of liquid can be poured therein.

Passing through the centre of the vapourizing chamber is a tube 6 of a material which has a high coeflicient of thermal expansion such for example as brass. One end 6A of the tube is .opento' theatmosphereand theother end is ex- :en'diofthe brass'tube which is open to the atmosphere' this rod rests on an adjusting screw I0 and its iother endiprotrudes beyond the valve seat andnorm'ally tilts a valve I I slightly off the seat 1 so that it is kept clear or open in which position .it. is retained by means of a spring I2.

Also incorporated in the mixing chamber is an air inlet valve I3 which may be set in a more or less open position. For? this purpose it may consist of a flat disc heldon one side of aseatin I4 by means-of one or more screws I5 and clear of the seating onthe opposite side by meansof-a screw I6 which is adjustable so that the valve can be set to the desired opening.

Connected to the mixing chamber isa rubber or other flexible tube I! Fig. 5 to which is at,- tached a face: piece adaptor I8 incorporateclin which are two non-:return valves 19,29. This valve I9 acts as an inspi-ratory valve which al.- lows the patient to inhale airand vapourirom the flexible tube and prevents expiration down the tube. The other'non-z-return valve 2!] allows the patient to exhale to the atmosphere and prevents inspirationaof air'therefrom. .On the face piece adaptor between thesetwo valves isza' branch pipe 2I onto which is :plugged the face piecei22.

On inspiration 'air enters one commonv inlet :23 into the :casing. It then divided :and;a;portion isdrawn through the end 16A ofthe brass tube :beyond'thevapourizingchamber and-as it passes throughsuch tubeiit is deflected by apartition 63 therein .throughholes "60 in the tube, into the vapourizing chamber'where itzcomeszinmorr- .tact with theisoakedwick and consequently picks up the anaesthetic 'vapour. It then :returns through another set of :holes 613: in the 'brassitube ingof the: air inlet valve I3 and the anaesthetic inlet valve I I. As the atmospheric temperature. rises the trapour pressure of the anaesthetic "also rises and .tozprevent this resulting 'in an increased centage of anaesthetic-to the patientthe anaes. thetic controlling valve I I is' made -to;close slightly as the temperaturerises: andzto openias thecterrr- .peitature falls. This isrdue-sto-the .combined'action of the expansion of the brass tube -li and negligible expansion ofzthe'ro'd'il and in this'way the gap between the seating 1 .andth'e' valve II is reduced.

.fIhiszarrangement :results in? a .zconsistentzmixture: of anaesthetic vapour and/air to the patient irrespective of .ordinaryatmospheric temperature variations.

What we claim: as our." invention and? desire to secure by Letters Patent in the United States is:

1. Apparatus for mixing the vapour of a volatile anaesthetic with air for inhalation purposes by a patient, comprising a vessel in which a quantity of anaesthetic liquid can be placed, the said vessel being provided with an air inlet for providing air for vapourizing said anaesthetic liquid, a mixing chamber being provided with a diluting air inlet and an orifice communicating with said vessel, a temperature controlled de' vice which as the temperature rises from any 3. Apparatus according to claim 1 wherein a thermally operated device may be arranged to provide for automatically altering the relative areas of the orifice through which the concentrated volatile anaesthetic air vapour issues and of the diluting air inlet through which the diluting air is drawn during inhalation.

WILLIAM EDMONDSON. WILFRED JONES.

REFERENCES CITED The following references are of record in the file of this patent:

15 UNITED STATES PATENTS Number Name Date 294,047 Hurd Feb. 26, 1884 1,257,934 Rund Feb. 26, 1918 1,323,181 Goodfellow Nov. 25, 1919 1,358,838 Fulton Nov. 16, 1920

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