US3172405A

US3172405A - Anaesthetizing apparatus

Info

Publication number: US3172405A
Application number: US245130A
Authority: US
Inventors: Sugg Basil Raymond
Original assignee: Longworth Scientific Instrument Co Ltd
Current assignee: Longworth Scientific Instrument Co Ltd
Priority date: 1961-12-29
Filing date: 1962-12-17
Publication date: 1965-03-09
Anticipated expiration: 1982-03-09
Also published as: GB983870A

Description

March 9, 1965 B. R. sues ANAESTHETIZING APPARATUS 4 Sheets-Sheet 1 Filed Dec. 17, 1962 I noentor 545/4 Rhyme/v0 6066' A llorneys March 9, 1965 S 3,172,45

ANAES HETIZING APPARATUS Filed Dec. 17, 1862 I 4 Sheets-Sheet s Ax E m 60 A llorneys March 9, 1965 B. R. SUGG 3,172,405

ANAESTHETIZING APPARATUS Filed Dec. 17, 1962 4 Sheets-Sheet;

Inventor Baa/L QQYM 8,. www

Attorneys 3,172,405 ANAES'IHETIZING APPARATUS Basil Raymond Sngg, Ahingdon, England, assignor to Longworth Scientific Instrument Qompany Limited, Ahingdon, England, a British company Filed Dec. 17, 1962, Ser. No. 245,130 7 Claims priority, application Great Britain, Dec. 29, 19b1, 46,677/61 1% Claims. (Cl. 128-188) This invention relates to anaesthetizing apparatus and is particularly directed to the provision of a new or improved device for holding an anaesthetic drug or agent in the form of a volatile liquid prior to its use and for delivering the drug, in the form of a mixture of its vapour with air or other gases, into a passage leading to a face mask through which it is inhaled by the patient.

It is an object of the invention to provide a device which, once charged with a predetermined dose of volatile anaesthetic agent, can operate automatically to administer no more than such dose to the patient and which therefore incorporates means for ensuring that the dose made available for administration is limited to a desired amount. Such a device is intended to find particular utility in emergencies, for example, outside of a hospital at the scene of an accident, in an ambulance, on a battlefield, or in any other of a wide variety of circumstances in which the facilities of an operating theatre are not avail able and where, frequently, only a single doctor is present.

Thus, according to the invention there is provided apparatus for storing and delivering an anaesthetic agent, comprising a storage reservoir and a vapourising chamber interconnected by a dosage container, and valve means between the storage reservoir and the dosage container and the dosage container and the vapourising chamber respectively, such valve means being so arranged that only a dose first measured into the dosage container may subsequently be passed into the vapourising chamber.

Preferably, and in accordance with a further feature of the invention, further valve means will be provided between the dosage container and the vapourising chamber and the vapourising chamber and a passage for delivering anaesthetic vapour mixed with air or other gases to the patient, such further valve means being so arranged as to permit the said passage to be cut off from the vapourising chamber when the latter is open to the dosage container, and to permit the vapourising chamber to be cut off from the dosage container when such chamber is open to the said passage. Such an arrangement makes it possible for the dosage container to be recharged with anaesthetic whilst a previous charge is being administered to the patient, without any danger of the new charge passing into the vapourising chamber and thus being administered as well. Very conveniently, such further valve means may be adapted adjustably to control the rate of flow of anaesthetic vapour out of the vapourising chamber into the said passage, thus controlling the proportion of vapour in the mixture delivered to the patient.

Preferably, means are provided for releasably holding the said further valve means in an intermediate position in which the vapourising chamber is cut off from the dosage container. Such means may conveniently comprise a spring-urged ball. Conveniently, such intermediate position of the further valve means may be so arranged that the apparatus will, in operation in such intermediate position, deliver a clinically desirable concentration of anaesthetic to a patient, of less strength than that delivered when such valve means is fully open, but suitable for maintaining anaesthesia.

The said further valve means may comprise an axially rotatable disc forming one wall of said vapourising chamber and formed with a pair of apertures which in one posi- United States Patent Patented Mar. 9, 1965 tion of the disc are aligned with a pair of openings in the wall of said passage but one of which apertures, in another position of the disc, provides a passage between the said dosage container and vapourising chamber.

The first mentioned valve means preferably extends through the storage reservoir and the dosage container and is provided with actuating means whereby it may be moved between two positions in one of which it permits passage of anaesthetic agent from the storage reservoir to the dosage container and in the other of which it permits passage of the agent from the dosage container to the vapourising chamber. Such valve means may include at least two parts which are urged apart by spring means into their passage closing positions. In such circumstances said actuating means preferably acts, when moved in one direction, to move one such valve part against said spring means and, when moved in the opposite direction, so to move the other such valve part.

In another form, such valve means includes an axially rotatable stern mounted in a hollow shaft having apertures communicating with the storage reservoir and dosage container, the said stem being so formed as to interconmeet such apertures in one of the positions of rotation. Said hollow shaft may be formed with a further aperture communicating with said dosage container, said stem being formed to connect said aperture with a passage leading to the vapourising chamber when in a position of rotation remote from that in which it interconnects the storage reservoir and dosage container.

Preferably, adjustable means are also provided for restricting the flow of air or other gases in said passage for delivering anaesthetic agent to a patient. Said means is preferably connected to and controlled by said further valve means so that as the rate of flow of anaesthetic agent into said passage is increased the flow restricting efiect of such means is also increased.

The said passage is preferably formed with an interchangeable portion of Venturi formation, for causing anaesthetic vapour to be withdrawn from the vapourising chamber into such passage.

Although apparatus according to the. invention may in certain circumstances be used to administer the whole of the anaesthetic which a patient is to receive, for example in the case of a dental operation in which the patient is not intended to remain unconscious for more than a few minutes, it is primarily intended for use in the induction of anaesthesia, which requires a comparatively short but concentrated adminstration of anaesthetic. Thus the apparatus will usually be employed to administer a dose of anaesthetic agent sufiicient to render the patient unconscious and will then be replaced by some other means for maintaining anaesthesia by the continued administration of a comparatively weak concentration of the same or a difierent drug. I

In order that the invention may be more readily understood, two embodiments thereof will now be described by way of example and with reference to the accompanying drawings, in which:

FIG. 1 is a vertical medial cross-section through a first embodiment of apparatus according to the invention;

FIG. 2 is a section of the line IIII of FIG. 1 but showing the said further valve means in a different position;

FIG. 3 is a horizontal cross-section on the line IIIIII of FIG. 1;

FIG. 4 is a plan view of the apparatus of FIGS. 1 to 3;

FIG. 5 illustrates a second embodiment and is a vertical medial cross-section on the line V-V of FIG. 6, showing the said further valve means in an intermediate position;

FIG. 6 is a section on the line VIVI of FIG. 5; and

FIGS. 7 and 8 are top and underneath plan views, respectively, of the apparatus of FIGS. 5 and 6.

The apparatus illustrated in FIGS. 1 to 4 of the drawings includes an anaesthetic storage reservoir 1 having in its top surface 2 a filler opening 3 provided with a stopper 4. The reservoir is formed with a cylindrical wall 5 and a base 6 which is formed near to its forward edge with a circular aperture for the reception of a supporting plate 7 for a transparent cylindrical dosage container 8 which may be formed of glass or a suitably transparent synthetic plastic material. The dosage container is sealed at its top and bottom by sealing rings 9.

At its lower end the dosage container rests in a recess in an inverted cup-shaped member 10 to the bottom of which is secured, by means of bolts 11 and a ring 12, a saucer-shaped member 13 which may be formed of transparent material and which, together with the member 10, defines a vaporising chamber 14 of the apparatus. The rear part of the wall 5 of the storage reservoir 1 extends downwardly at 15 to meet the upper surface of the member 10.

A fixed hollow cylindrical tube 16 is fluid-tightly mounted in openings in the top surface 2 of the storage reservoir 1, the supporting plate 7, and the cup-shaped member 10, forming a passage extending from the top of the apparatus through to the vapourising chamber. The tube 16 is formed with openings 17 and 18 communicating with the storage reservoir 1, and oppositely facing

openings

19 and 20 communicating with the dosage container 8.

A cylindrical valve member 21 makes a tight sliding fit in the tube 16, and is formed at its upper end with an L-shaped passage 22 connecting its end face to an opening in its side wall and which, when the member 21 is rotated so that the lower orifice 23 of the passage is aligned with the opening 17 in the tube 16, connects the storage reservoir to the atmosphere. Approximately mid way of its length the valve member 21 is formed with a milled slot 24 which, when aligned with the openings 18 and 19 in the tube 16, connects the storage reservoir to the dosage container 8. It will be observed that, when the slot 24 is so aligned, the storage reservoir is also connected to the outside atmosphere by way of the passage 22 so that anaesthetic agent is able to flow through the opening 18, the slot 24 and the opening 19 into the dosage container 8.

At its lower end the valve member 21 is formed with an inverted L-shaped passage 25 joining its lower end face to an opening 26 in its side wall and this passage, when its orifice 26 is aligned with the opening 20 in the tube 16 by suitable adjustment of the valve member 21, connects the dosage container 8 to the vapourising chamber 14. It will be observed that, when the openings 18 and 19 in the tube 16 are connected by way of the slot 24 to allow anaesthetic to flow into the dosage container, the opening 20 in the tube is diametrically opposite the orifice 26 of the passage 25 and the anaesthetic agent entering the dosage chamber is therefore unable to flow into the vapourising chamber. On the other hand, if the valve member is now rotated through 180, the orifice 26 of the passage 25 will be moved into alignment with the opening 20 and anaesthetic agent in the dosage container will flow into the vapourising chamber whilst, as the openings 18 and 19 are now diametrically opposite the slot 24,no more anaesthetic agent will flow from the reservoir into the dosage container. The dosage container 8 is marked or otherwise provided with a suitable scale for measuring the volume of anaesthetic agent which it contains.

Further valve means are provided of which one function is to prevent the delivery of anaesthetic from the vapourising chamber to the patient whilst such chamber is connected to the dosage container, and comprises a disc 27 of any suitable material, preferably nylon, mounted on a spindle 28 in the inverted cup-shaped member 10 so as to be rotatable therein and making substantially fluidtight engagement with the walls thereof. The disc 27 is rotatable, by means of a handle 29 secured thereto and extending through a slot 31 cut in the front wall of the member 10, through an angle of approximately and is formed with two

cylindrical openings

31 and 32 equidistant from its axis. In the position shown in FIG. 1 the disc 27 is disposed at one limit of its movement and is in the position where the opening 31 therein lies beneath the lower orifice of the passage 25 so that when orifice 26 and opening 20 are in registry anaesthetic agent is able to flow into the vapourising chamber from the dosage container. In this position the opening 32 of the disc 27 is closed by the member 10.

In FIG. 2 the disc 27 has been rotated to the other limit of its movement and the passage 25 is closed by an unapertured part of the disc 27 so that no more anaesthetic agent can flow into the vapourising chamber from the dosage container. However, the

openings

31 and 32 in the disc are now aligned with

further openings

33 and 34 respectively in the member 16, which openings communicate directly with the interior of a tube 35 passing through the centre of the apparatus and leading to a breathing mask for the patient. The tube 35 is formed with a constriction 36 adjacent the opening 33 in the member 10 and the constricted portion of the tube wall is formed with a number of apertures 37 spaced evenly therearound so as to form a communication between the opening 34 and the interior of the tube; a further opening 38 in the tube wall is aligned with the opening 33 in the member 10. The venturi eifect of the constriction 36 causes air or oxygen flowing along the tube 35 in the direction of arrow A to be sucked down into the vapourising chamber by way of

openings

38, 33 and 31 where it entrains anaesthetic vapour and passes out again through

openings

32, 34 and 37 into the tube 35 for delivery to the patient. The arrows show the direction of flow through the apparatus.

The constriction 36 and the

apertures

37 and 38 together comprise a system providing a suction force to extract vapour from the vapourising chamber and a reslstance to the flow of such vapour, and may be suitably proportioned to provide the required concentration of vapour in the mixture delivered to the patient, and to ensure that such concentration is within the accepted safe limits for the particular drug used over the range of flow rates likely to occur in practice. In the illustrated embodiment an inner tube 39, formed with the constriction 36 and

apertures

37 and 38, is releasably mounted in the tube 35; by this means a series of tubes 39, having different characteristics and each suited to a particular drug, may be provided for selective mounting in the tube 35.

The mode of adjustment of the disc 27 may be clearly understood by reference to FIG. 3, which is a horizontal cross-section looking upwards through the disc and showing, in full lines, the disc in position for filling the vapour- 1s1ng chamber from the dosage container and, in dot-andpick lines, the disc in its other limiting position for permitting the passage of anaesthetic vapour into the tube 35 from the vapourising chamber.

The operation of the apparatus is as follows: assuming a suflicient quantity of liquid anaesthetic agent to be present in the storage reservoir 1, and the valve member 21 to be in its neutral position shown in FIG. 1' where the reservoir .1, container 8 and chamber 14 are all isolated from each other, the valve member is first rotated anticlockwise through 90 so as to bring the letter C (meanng charge) on its operating handle 39 (see FIG. 4) mto alignment with an index mark 40 on the upper surface 2 of the reservoir. This movement effects communication between reservoir 1 and container 8 and liquid anaesthetic agent then flows into the dosage container 8. When the required dose is present in the latter, the valve member is returned to its neutral position to cut ofi the reservoir from the dosage container. The valve member is then rotated clockwise through 90 to bring the letter F (meaning fill) on its operating handle into alignment with the index mark, to close the connection between the reservoir and the dosage container, and to permit the measured dose to flow through the passage 25 and opening 31 in the disc 27 into the vapourising chamber. The disc 27 is then rotated into the dotted line position of FIG. 3 to close the connection between the dosage container and the vapourising chamber and to open the

connections

33, 34 between the latter and the tube 35; anaesthetic vapour then commences to flow into the tube to be administered to the patient.

It will be understood that the rate of flow of anaesthetic vapour out of the vapourising chamber may be controlled by rotational adjustment of the disc 27 so as fully or partly to align the

openings

31 and 32 therein with the

openings

33 and 34 in the upper face of the member 10. Calibration marks will preferably be provided adjacent the path of movement of the operating handle 29 of the disc 27 (for example on the surface 41 of the part 10, see FIG. 1) to indicate the degree of opening of the passages through which the anaesthetic vapour flows in any position of adjustment of the disc.

Suitable stop means will preferably be associated with the valve member 21 to prevent its rotation beyond the charge and fill marks shown in FIG. 4, so as to guard against the possibility of the member being rotated from the neutral to the fill position by way of the charge position and thus feeding a small quantity of anaesthetic in excess of the required dose into the dosage container.

The apparatus illustrated in FIGS. to 8 is a preferred modification of that of FIGS. 1 to 4, and parts thereof which have the same function as in the apparatus already described are given the same reference numerals and will not be described in detail.

The modified apparatus difliers chiefly in the constructions of the valve mechanism for charging the dosage container 8 with a dose of anaesthetic agent and subsequently passing such dose into the vapourising chamber 14. This includes a tube 42 fixedly mounted between the upper surface 2 of the reservoir 1 and the base 6 thereof and formed with a pair of diametrically opposite openings 43 at its lower end. The tube 42 houses a further tube 44 flanged at its lower end 45, the upper surface of such flange being provided with a sealing ring 46. The tube 44 has a valve stem 47 slidably mounted therein, the lower end of which is screw-threadedly secured in a valve member 48 having a nose 49 and a flange 59 at its lower end, a compression spring 51 being mounted on the valve member between such flange and the flange 45 of the tube 44.

Where it passes through a bore 52 in the base 6 of the reservoir 1, the tube 44 is reduced in diameter at 53 to provide a passage between the reservoir 1 and dosage container 8. A further bore 54 is formed in the upper surface of the cup-shaped member 10, fitted with a sealing ring 55, which provides a passage between the dosage container 8 and the vapourising chamber 14 when the valve disc 27 is suitably orientated.

The flange 45 on the tube 44 provides a closure for the bore 52 whilst the nose 49 on the valve member 48 closes the bore 54, such parts normally being urged into their bore-closing positions by the spring 51.

The valve stem 47 is furnished with a top cap 56 having an enlarged head which overlies a valve operating knob 57 loosely mounted on such cap.

It will thus be seen that depression of the knob 57 will cause downward movement of the tube 44 against the spring 51 to open the passage between the reservoir and the dosage container, whilst the passage from the dosage container through the member remains closed. Lifting of the knob 57 will, however, bring it into engagement with the enlarged head of the cap 56 on the valve stem 47 to lift the nose 49 of the valve member 48 out of the bore 54 and thus open the latter to the dosage container.

The apparatus of FIGS. 5 to 8 also diifers from that of FIGS. 1 to 4 in certain other details; thus the vapourising chamber 14 is defined by an internally threaded ring 58 and has its base 59 formed of glass or other suitably transparent material so that an operator can see how much anaesthetic agent remains in such chamber at any stage. Also, the valve disc 27 is formed in two parts, namely a metal base 69 to which is screwed a nylon disc 51.

A further important modification lies in the provision of an adjustable flow restrictor in the tube 35, which comprises a disc 62 mounted on the upper end of spindle 28, which is extended upwardly for this purpose through the tube 35. The position of disc 62 is dependent on that of valve disc 27 and the arrangement is such that, as the valve disc is moved to bring the

openings

31 and 32 therein towards complete alignment with

openings

33 and 34 in tube 35, the disc 62 is moved into a position transverse to the axis of the tube to restrict the flow of oxygen or other gases and thus increase the concentration of the anaesthetic agent passed to the patient.

Means are also provided by which it will be apparent to an operator when he has rotated the valve disc 27 in such opening direction, by means of the handle 29, sufficiently for the bore 54 leading from the dosage container to be shut off from the vapourising chamber by the valve disc, at which point it is of course safe to re charge the dosage container. Such means comprises a spring-urged ball 63 adapted to engage in a depression in the metal part 66 of valve disc 27 at such point in its rotation, so as to provide a rest position for the valve disc at this point.

Furthermore, such position of the valve disc 27 can conveniently be selected so that the apparatus will deliver to the patient a clinically desirable concentration of drug, at which second and subsequent doses can be administered, which is considerably reduced in strength cornpared with that delivered when the valve disc 27 is in such a position that

openings

31 and 33, and 32 and 34, are coincident.

I claim:

1. Apparatus for storing and delivering anaesthetic agent, comprising: an anaesthetic agent storage reservoir; 21 vaporizing chamber; means defining a passage for delivering anaesthetic vapor mixed with a gas from said vaporizing chamber to a patient; a dosage container between said storage reservoir and said vaporizing chamber; first valve means operative between the storage reservoir and the dosage container and between the dosage container and the vaporizing chamber, respectively, such first valve means, comprising a valve actuating rod extending through the storage reservoir and the dosage container, and being movable between two positions in one of which it permits passage of anaesthetic agent only from the storage reservoir to the dosage container and in the other of which it permits passage of the agent only from the dosage container to the vaporizing chamber, whereby only a dose first measured into the dosage container may subsequently be passed to the vaporizing chamber; and further valve means between the dosage container and the vaporizing chamber and between the vaporizing chamber and said delivery passage respectively, such further valve means including an axially rotatable disc forming one wall of the vaporizing chamber and formed with a pair of apertures which, in a first position of rotation of said disc, may be partly or wholly aligned with a pair of openings in the wall of said deiivery passage to permit variation of the rate of flow of anaesthetic vapor from the vaporizing chamber into the deiivcry passage; one of said apertures, in a second position of rotation of the disc, providing a communicating passage between the dosage container and the vaporizing chamber, whereby such further valve means causes the delivery passage to be cut ofl from the vaporizing chamber when the latter is open to the dosage container, and

7 causes the vaporizing chamber to be cut oif from the dosage container when such chamber is open to the delivery passage.

2. Apparatus according to claim 1 wherein means are provided for releasably holding the said further valve means in an intermediate position in which the vapourising chamber is cut oil from the dosage container.

3. Apparatus according to claim 1, wherein said firstmentioned valve means includes at least two parts which are urged apart by spring means into passage closing positions.

4. Apparatus according to claim 3, wherein said actuating rod acts, when moved in one direction, to move one such valve part to open position against said spring means and, when moved in the opposite direction, so to move the other such valve part to open position.

5. Apparatus according to claim 1, wherein said valve actuating rod includes an axially rotatable stem mounted in a fixed tube having apertures communicating with the storage reservoir and dosage container, the said stem being so formed as to interconnect such apertures in one of its positions of rotation.

6. Apparatus according to claim 5, wherein said fixed tube is formed with a further aperture communicating with said dosage container, said stern being formed to connect said aperture with a passage leading to the vaporizing chamber when in a position of rotation remote from that in which it interconnects the storage reservoir and dosage container.

7. Apparatus according to claim 1 including adjustable means for restricting the flow of air or other gases in said passage for delivering anaesthetic agent to a patient.

8. Apparatus according to claim 7, wherein said flow restricting means is connected to and controlled by said further valve means so that as the rate of flow of anaesthetic agent into said passage is increased theflow restricting effect of such means is also increased.

9. Apparatus according to claim 8, wherein said fiow restricting means comprises a disc mounted for rotation about its diameter on a spindle which also carries said further valve means. i

10. Apparatus according to claim 1 wherein said passage for delivering anaesthetic vapour is formed with an interchangeable portion of Venturi formation, for causing anaesthetic vapour to be withdrawn from the vapourising chamber into such passage.

References Cited {y the Examiner UNITED STATES PATENTS Re. 17,512 12/29 McKesson 128203 80,852 8/ 68 Blake et a1. 222-452 X 301,377 7/84 Long 128-188 1,512,486 10/24 Rhames 128188 2,141,794 12/38 King 128188 2,866,455 12/58 De La Torre 128188 FOREIGN PATENTS 519,203 3/40 Great Britain. 537,073 6/41 Great Britain.

RICHARD A. GAUDET, Primary Examiner.

JORDAN FRANKLIN, Examiner.

Claims

1. APPARATUS FOR STORING AND DELIVERING ANAESTHETIC AGENT, COMPRISING: AN ANAESTHETIC AGENT STORAGE RESERVOIR; A VAPORIZING CHAMBER; MEANS DEFINING A PASSAGE FOR DELIVERING ANAESTHETIC VAPOR MIXED WITH A GAS FROM SAID VAPORIZING CHAMBER TO A PATIENT; A DOSAGE CONTAINER BETWEEN SAID STORAGE RESERVOIR AND SAID VAPORIZING CHAMBER; FIRST VALVE MEANS OPERATIVE BETWEEN THE STORAGE RESERVOIR AND THE DOSAGE CONTAINER AND BETWEEN THE DOSAGE CONTAINER AND THE VAPORIZING CHAMBER, RESPECTIVELY, SUCH FIRST VALVE MEANS, COMPRISING A VALVE ACTUATING ROD EXTENDING THROUGH THE STORAGE RESERVOIR AND THE DOSAGE CONTAINER, AND BEING MOVABLE BETWEEN TWO POSITIONS IN ONE OF WHICH IT PERMITS PASSAGE OF ANAESTHETIC AGENT ONLY FROM THE STORAGE RESERVOIR TO THE DOSAGE CONTAINER AND IN THE OTHER OF WHICH IT PERMITS PASSAGE OF THE AGENT ONLY FROM THE DOSAGE CONTAINER TO THE VAPORIZING CHAMBER, WHEREBY ONLY A DOSE FIRST MEASURED INTO THE DOSAGE CONTAINER MAY SUBSEQUENTLY BE PASSED TO THE VAPORIZING CHAMBER; AND FURTHER VALVE MEANS BETWEEN THE DOSAGE CONTAINER AND THE VAPORIZING CHAMBER AND BETWEEN THE VAPORIZING CHAMBER AND SAID DELIVERY PASSAGE RESPECTIVELY, SUCH FURTHER VALVE MEANS INCLUDING AN AXIALLY ROTATABLE DISC FORMING ONE WALL OF THE VAPORIZING CHAMBER AND FORMED WITH A PAIR OF APERTURES WHICH, IN A FIRST POSITION OF ROTATION OF SAID DISC, MAY BE PARTLY OR WHOLLY ALIGNED WITH A PAIR OF OPENINGS IN THE WALL OF SAID DELIVERY PASSAGE TO PERMIT VARIATION OF THE RATE OF FLOW OF ANAESTHETIC VAPOR FROM THE VAPORIZING CHAMBER INTO THE DELIVERY PASSAGE; ONE OF SAID APERTURES, IN A SECOND POSITION OF ROTATION OF THE DISC, PROVIDING A COMMUNICATING PASSAGE BETWEEN THE DOSAGE CONTAINER AND THE VAPORIZING CHAMBER, WHEREBY SUCH FURTHER VALVE MEANS CAUSES THE DELIVERY PASSAGE TO BE CUT OFF FROM THE VAPORIZING CHAMBER WHEN THE LATTER IS OPEN TO THE DOSAGE CONTAINER, AND CAUSES THE VAPORIZING CHAMBER TO BE CUT OFF FROM THE DOSAGE CONTAINER WHEN SUCH CHAMBER IS OPEN TO THE DELIVERY PASSAGE.