US3221737A - Device for vaporization of volatile anesthetic liquids - Google Patents

Description

Dec. 7, 1965 I I J. A. FELTS 3,221,737

DEVICE FOR VAPOBIZATION 0F VOLA'IILE ARESI'HE'I'IO LIQUIDS Filed July 25, 196? 2 Sheets-Sheet 1 PRESSUR E FRO" FLOW" E YER Dec. 7, 1965 J. A. FEL'I'S 3,221,737

DEVICE FOR VAPORIZATIOII OP VOLATILB MIES'I'HETIO LIQUIDS F1106 July 25. 1962 2 ShOOMhIOl B INVENTOR JAMES A. FEU'S ATTORNEYS United States Patent Ofifice 3,221,737 DEVICE FOR VAPORIZATION F VOLATILE ANESTHETIC LIQUIDS James A. Felts, 517 Bainbridge Road, Marion, Ill. Filed July 25, 1962, Set. No. 212,409 Claims. (Cl. 128-188) This application is a continuation-in-part of my application entitled Device for vaporization of Volatile Anesthetic Liquids, Serial Number 82,043, filed January 11, 1961, now Patent No. 3,123,071.

This invention relates to an anesthetic vaporizing assembly which is designed to give a patient a constant percent concentration of a desired anesthetic. It is particularly well adapted for use in an absorption type closed circuit anesthesia system, but it may also be efiiciently utilized in other environments.

It is an object of this invention to provide a means of automatically metering a liquid anesthetic into an anesthesia circuit at a rate which is dependent upon the volume of metabolic oxygen or other gases injected into the patients breathing circuit.

Another object is to provide an easily operated, reliable, and etiicient means of metering an anesthetic to apatient receiving anesthesia from a closed circuit absorption type system.

A further object is to provide an anesthetic metering device which is capable of continuously producing a selected percent of anesthetic vapor in any desired volume of gas being led to the patient's breathing circuit.

Another object is to provide an anesthetic metering and vaporizing assembly which is so designed that it prevents extreme variations in the temperature of the assembly and thus prevents excessive fluctuations in th percent of anesthetic vapor'delivered.

A closed circuit anesthesia system is one in which the patients face mask has two conduits leading therefrom. One of these receives the air exhaled by the patient and the other supplies air to the patient upon inhalation. Suitable check valves in the face mask cause the flow as described.

The inhalation conduit and exhalation conduit are joined at some remote point and form a circuit which is closed to the outside atmosphere. Flow through the circult is caused by the breathing of the patient; Carbon dioxide and other impurities are removed by suitable means, and metabolic oxygen or other-gases are added to supply the needs of the patient. Likewise, an anesthetic is injected into the circuit.

An improved vaporizer for such a system wherein a liquid anesthetic is transformed into its gaseous state is the subject of my c0-pending application, Serial Number 82,043, filed January 11, 1961, and entitled Device for vaporization of Volatile Anesthetic Liquids," Patent No. 3,123,071. The instant invention is particularly well adapted for use with my vaporizer, but may find equally satisfactory applications with other closed circuit anesthetic vaporizer-s. i

As mentioned above, metabolic oxygen or other gases are added to the closed circuit anesthesia system. In the preferred embodiment of this invention, the influence of these gases to the system would provide the force which meters the liquid anesthetic into the'vaporizing chamber described in my above mentioned co-pending application. Using the novel system described hereafter, the amount of liquid anesthetic metered into the system will be dependent upon the amount of external gases added to the circuit and will maintain a constant percentage thereof.

My invention may best be understood by reference to the accompanying drawings wherein:

FIG. 1 is a view partially in section, of the improved metering device mounted on a vaporizing chamber; and

3,221,737 Patented Dec. 7, 1965 FIG. 2 is a view taken along line 2-2 in FIG. 1 and showing the general configuration of the vaporizer as sembly including the metering portion and the vuporiz ing portion; and

FIG. 3 is a view taken along line 3-3 in FIG. 1 of a dial and scale used for adjusting the anesthetic flow into the vaporizer chamber.

In the prior art, anesthetics have sometimes been manually inject-ed into the flow circuit of a closed circuit system by a syringe-like device. My invention provides a means to eliminate this tedious and inaccurate means of V injecting the liquid anesthetic and to produce a system which will automatically vary the amount of anesthetic vaporized as the flow of gases added to the system is varied.

Another prior art device is the "blow-over" system in which a. metered amount of gas is passed over a reservoir of liquid anesthetic. This device is calibrated to deliver a given percent of vapor. Still another system allows a metered amount of gas to bubble through a reservoir of anesthetic liquid. This gives a stated percent concentration which is dependent upon the temperature and vapor pressure.

In order to deliver a certain percent of vapor to the patient, the blow-over" and bubble systems require a specific flow of gas. Since the gas required by a patient varies from case to case, it is obvious that some of the gas and anesthetic vapor must be bled oil? before arriving in the patients breathing circuit. This is a breach of the air-tight integrity of the system and also results in unnecessary waste of the gas and anesthetic.

Both of these latter mentioned prior art systems vaporize the anesthetic on or within the surface of the reseryou: or liquid anesthetic. This vaporization lowers the temperature of the liquid in the reservoir, thus changing the vapor pressure of the liquid anesthetic which, of course, varies the percent concentration of vapor which passes to the patient.

In my improved apparatus there is no need for supplying an excessive amount of gas in order to achieve a desired percent vapor concentration. Also, the vaporization of'the anesthetic takes place in an area removed from the liquid reservoir, thus eliminating any variations due to temperature changes of the liquid anesthetic. Furthermore, the efiicient design of my vaporizing chamber with its improved thermal efliciency and abundant surface area eliminates substantial temperature variations. This is more fully discussed in my above-identified co-pending application.

Referring to FIG. I, a metering device generally designated 2 is secured atop a vaporizing chamber 4 which is in communication with the patient's breathing circuit, shown passing through a passage 12 having an inlet connection 6 and an outlet connection 8.

As described in my co-pending application, the gases flowing through the passage 12 in the base 14 of the vaporizing chamber 4 cause a reduced pressure at the throat of a venturi 16. Passage 17 connects this zone of reduced pressure with the vaporizing chamber. Likewise, a passage 18 leads from an enlarged portion 20 of the passage 12 to the vaporizing chamber 4. The pressure dilference between passages 17 and 18 causes some of the gas flowing through passage 12 to be diverted through the vaporizing chamber. These gases are drawn into the vaporizing chamber through passage 17; whereafter they mix with vaporized anesthetic and then pass from the vaporizing chamber through passage 18 back into passage 12. The vaporizing chamber 4 may therefore. be considered a portion of the breathing circuit, since some of the gases in the circuit are regularly circulated therethrough.

The liquid anesthetic is metered onto the hemispherical dome 21 in the vaporizing chamber by the metering device 2.

Before use, a liquid anesthetic is placed in a reservoir 22 in the metering device by removing the cap 24 and pouring it into a funnel opening 28. A drain cook is located at the lowermost point of the reservoir to facilitate cleaning and drainage.

The liquid anesthetic may flow through a small orifice 32 in the bottom of reservoir 22 into a pressure chamber 34. It is from this pressure chamber that the liquid anesthetic is forced into the vaporized chamber 4.

The anesthetic is maintained at a constant depth in the pressure chamber by a float valve assembly.

A float 38 is supported by arms 39 which are hinged by pins 40 to a lug on an upstanding sleeve 59 closed at its top. The float is free to rise and fall as the liquid depth varies. The free end of float 38 supports the shank of a needle valve 42 which seats in the orifice 32. Needle valve 42 has an enlargement 43 thereon to prevent it from falling through its supporting member 45. An aperture 47 allows the liquid to flow from within member 45 to the pressure chamber 34. A vent tube 49 passes from pressure chamber 34 to a point in reservoir 22 above the liquid level therein. This facilitates the flow of liquid anesthetic through aperture 32 by equalizing the pressure. It can be seen that as the liquid anesthetic u'n chamber 4 is depleted, the needle valve will open and restore the fluid to the desired level. The needle valve will close aperture 32 when the liquid reaches such level. Pressure chamber 34 also has a drain cock, located at 44.

Air or gas is delivered to the pressure chamber 34 through an inlet 46. In the preferred arrangement, the pressure source is from the fiowmeters of a standard anesthetic machine. Metabolic oxygen or oxygen and other gases are thus supplied to the closed circuit system. These flowmeters provide gases at a constant volumetric rate of flow.

Vent ducts, 48, 50 and 52 communicate between the pressure chamber 34 and the vaporizing chamber 4, allowing the oxygen or other gases to pass into the breathing circuit. A regulating valve 54 is located in the vent 48 and may partially impede the flow of gases therethrough, and thus may regulate the pressure within the pressure chamber 34. Regulating valve 54 is preferably a needle valve with a threaded shank and it is provided with an adjusting knob 60.

The liquid anesthetic passes from pressure chamber 34 to the vaporizing chamber 4 through a fluid passage or tube 58. One end of tube 58 is located beneath the surface of the liquid anesthetic and the other and discharges into a sleeve 59 closed at its upper end, directly above the dome inside the vaporizing chamber. The tube passes above the liquid level of the anesthetic in chamber 34, so there is no gravity flow of the fluid.

The pressure is chamber 34 is normally maintained at a higher level than that in vaporizing chamber 4. This naturally results in a flow of the liquid anesthetic through tube 58 to the vaporizing chamber.

A most significant feature of the instant invention is the use of the regulating valve 54 to control the amount of anesthetic which is dispensed. Since the amount of liquid anesthetic dispensed relies wholly upon the pressure ditferential between chambers 34 and 4 and since the valve 54 is located in a vent duct between these two chambers, any adjustment of the valve will result in a change in the pressure differential. Opening valve 54 fully would equalize these pressures and no fluid would flow. Similarly, by closing the valve 54 the maximum amount of anesthetic would flow.

The amount of metabolic oxygen or other gases required by a patient will vary from case to case. Sometimes the flow for small children will be as low as 50 cc. per minute.

Within the range of gas flow required for the closed circuit type anesthetic system, it has been found that for any setting of the regulating valve 54, the amount of anesthetic metered into the vaporizing chamber is directly proportional to the volume of gases being introduced through gas inlet 46. With a given valve setting, a change in the gas admitted through inlet 46 does not vary the percent of vapor delivered into the breathing circuit from the vaporizing chamber. This is because the amount of liquid delivered through tube 58 will chage in proportion to the change in gas flow.

With any given gas flow, the percent of vapor may readily be changed by adjusting the regulating valve 54, which will result in the admission of more or less liquid anesthetic into vaporizing chamber 4 into a constant volume of gas.

To enable the operator of the device to ascertain the ratio of liquid anesthetic to gas, the knob 60 of the regulating valve 54 may be imprinted with a pointer as shown at 62, see FIG. 3. The scale 56 is graduated in percentage of any desired anesthetic vapor, some of which are shown on the scale illustrated in FIG. 3.

In a metering device of this nature, it is important that the proper dosage is given to a patient, or severe physical harm may result. To prevent the knob 60 on the regulating valve from receiving more or less turns than desired, the knob is provided with a projection 64 on its edge which, when the pointer 62 is at its furthest position to the right, will abut against a stop 66 to prevent furthcr rotation.

In operation, the improved metering device is first filled with the desired anesthetic. The regulating valve knob is adjusted to the percent dosage which is needed for the particular patient and case. Then the fiowmeters are adjusted to provide the required flow of gases through the gas inlet 46.

As described above, the pressure in the pressure chamber 34 will increase as the regulating valve 54 is closed, and a greater flow of liquid anesthetic will result. When the regulating valve is kept at any given setting, and the flow of gases admitted through gas inlet 45 is increased, the pressure in chamber 34 will increase and a correspondingly increased flow of liquid anesthetic into vaporizing chamber 4 will ensue, resulting in the same percent of vapor being delivered from the device.

From the above description, one may readily see that my improved metering device overcomes many of the shortcomings of the prior art. First, it makes it possible to meter an anesthetic into small amounts of gas and eliminate the necessity of bleeding anesthetic vapor and gas from the system. This makes this device especially useful in administering an anesthetics to children and to certain other patients requiring small amounts of gas.

Another notable improvement is that the percent of vapor delivered in the gas stream may be easily varied by changing the regulating valve setting, and the percent will remain constant, regardless of the rate of gas flow to the patient.

It is understood that many modifications may become apparent and the scope of thisinvention is not limited only to the above-described embodiment but by the claims which are appended hereto.

I claim:

1. An anesthetic vaporizer assembly for use in a closed circuit anesthesia system comprising a vaporizing portion and an anesthetic metering portion, said vaporizing por tion having a vaporizing chamber formed by a housing with a central tower therein, said vaporizing chamber having an inlet conduit and an outlet conduit, a breathing line connected to each or said conduits, venturi means in said breathing line to create a pressure diiferential between said inlet and outlet conduits to create a gas flow through said vaporizing chamber; said anesthetic metering portion having a pressure chamber partially filled with liquid anesthetic, means to supply gas at a constant rate of flow to said pressure chamber, means regulating the pressure in said pressure chamber including a gas duct passing from said pressure chamber to said vaporizing chamber, said gas duct having a variable obstruction therein, a fluid conduit passing from a portion of said pressure chamber submerged by-liquid anesthetic to said vaporizing chamber.

2. In combination, a breathing circuit and a metering device for liquid anesthetics, said metering device having a pressure chamber partially filled with a liquid anesthetic, means for supplying gas at a constant rate of flow to said pressure chamber, means for regulating the pressure in said chamber including a gas duct with an adjustable obstruction therein passing from said pressure chamber to said breathing circuit, a fluid passage leading from a portion of said pressure chamber submerged by liquid anesthetic to said breathing circuit.

3. In combination, a breathing circuit and a metering device for liquid anesthetics, said metering device having a pressure chamber partially filled with a liquid anesthetic,

means for supplying gas at aconstant rate of flow to said pressure chamber, means for regulating the pressure in said chamber including a gas duct leading from said pressure chamber to said breathing circuit, a needle valve positioned in said duct, and a fluid passage leading from a portion of'said pressure chamber submerged by liquid anesthetic to said breathing circuit.

4. In combination, a breathing circuit and a metering device for liquid anesthetics, said metering device having a pressure chamber partially filled with a liquid anesthetic, a fluid passage leading from a portion of said pressure chamber submerged by liquid anesthetic to said breathing circuit, means for supplying gas at a constant rate of flow to said pressure chamber, means for regulating the pressure in said pressure chamber including a gas duct leading from said pressure chamber to said breathing circuit, a needle valve positioned in said duct, means for indicating the position of said needle valve, a scale associated with said indicating means, said scale graduated in ratios of anesthetic to gas.

5. In a device for metering liquid anesthetics into a breathing circuit, a reservoir chamber for a liquid anesthetic, a pressure chamber partially filled with ,liquid anesthetic, a breathing circuit, an orifice between said reservoir chamber and said pressure chamber allowing gravity flow of liquid anesthetic therethrough, a float inthe liquid in said pressure chamber, means associated with said float to obstruct said orifice when a desired liquid level is attained in said pressure chamber, means supplying gas at a constant rate of flow to said pressure chamber, means for regulating the pressure in said pressure chamber including a gas duct with an adjustable obstruction.

therein passing from said pressure chamber to said breathing circuit, a fluid passage leading from a portion of said 6 pressure chamber submerged by liquid anesthetic to said breathing circuit.

6. A system for administering a vaporized liquid anesthetic comprising, in combination, a breathing circuit leading to a patient, said circuit including an anesthetic vaporizing area, and a metering device for dispensing a liquid anesthetic into said vaporizing area; said metering device having a pressure chamber with a liquid level therein,

area of said breathing circuit.

9. The system of claim 6 wherein said venting means is a duct having a needle valve therein, said needle valve having means indicating the position thereof, a scale graduated in ratios of anesthctic-to-gas associated with said indicating means.

10. An anesthetic vaporizer assembly comprising a vaporizing chamber and an anesthetic metering portion, said anesthetic metering portion having a pressure chamber partially filled to a liquid level with liquid anesthetic, means for supplying gas at a constant rate of flow to said pressure chamber, means regulating the pressure in said pressure chnmber'including a gas duct passing from said pressure chamber to said vaporizing chamber, a variable obstruction in said gas duct, a fluid conduit passing from a portion of said pressure chamber below said liquid level to' said vaporizing chamber, and means adapted to connect said vaporizing chamber to a patient's breathing line.

References Cited by the Examiner UNITED STATES .PATENTS 1,738,757 12/1929 Bragdon 239--347 2,141,794 12/1938 King l28-188 2,243,435 5/ 1941 Mott et al 239-347 3,018,777 1/ 1962 Dietrich 128l88 3,021,840 2/1962 Hallamore et a1 128-183 I FOREIGN PATENTS 6,312 3/ 1903 Great Britain. 519,203 3/ 1940 Great Britain.

OTHER REFERENCES V. Mueller & COL, Catalog No. 65, Chicago, Ill., 1963 (p. 745 relied on).

RICHARD A. GAUDET, Primary Examiner. JORDAN FRANKLIN, Examiner.

Claims (1)

1. 2. IN COMBINATION, A BREATHING CIRCUIT AND A METERING DEVICE FOR LIQUID ANESTHETICS, SAID METERING DEVICE HAVING A PRESSURE CHAMBER PARTIALLY FILLED WITH A LIQUID ANESTHETIC, MEANS FOR SUPPLYING GAS AT A CONSTANT RATE OF FLOW TO SAID PRESSURE CHAMBER, MEANS FOR REGUALTING THE PRESSURE IN SAID CHAMBER INCLUDING A GAS DUCT WITH AN ADJUSTABLE OBSTRUCTION THEREIN PASSING FROM SAID PRESSURE CHAMBER TO SAID BREATHING CIRCUIT, A FLUID PASSAGE LEADING FROM A PORTION OF SAID PRESSURE CHAMBER SUBMERGED BY LIQUID ANESTHETIC TO SAID BREATHING CIRCUIT.

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