WO2006065202A1

WO2006065202A1 - An anaesthetic liquid vaporizer

Info

Publication number: WO2006065202A1
Application number: PCT/SE2005/001867
Authority: WO
Inventors: Hans Lambert
Original assignee: Hans Lambert
Priority date: 2004-12-13
Filing date: 2005-12-08
Publication date: 2006-06-22
Also published as: SE0403017D0

Abstract

The invention relates to a vaporizer having a vaporizing chamber (1) which includes a liquid anaesthetic gas inlet (2) and a gas outlet (3). The vaporizing chamber (1) communicates with an anaesthetic liquid delivery device which communicates with an external liquid source (6) via a liquid supplier (7). Liquid to be vaporized is exposed to a heated surface (4) inside the chamber (1). The liquid supplier (7) is controllable. The vaporizer is intended for use in the treatment of patients, preferably for administering an anaesthetic. The present invention also relates to a vaporizing method applied with the aid of the inventive vaporizer.

Description

AN ANAESTHETIC LIQUID VAPORISER AND A METHOD OF VAPORIZING AN ANAESTHETIC LIQUID .

FIELD OF INVENTION

According to a first aspect, the present invention relates to a vaporizer of the kind defined in the preamble of Claim 1. According to a second aspect, the invention relates to the particular use of such a vaporizer, and in accordance with a third aspect the invention relates to a liquid vaporizing method of the kind defined in the preamble of Claim 18.

Although the invention can be applied in several different ways, it finds particular use in the anaesthesia of patients, in which case the inventive vaporizer is adapted for connection to a system of hoses and apparatus that deliver breathing gas to a patient and that supply vaporized anaesthetic to respective patients.

DESCRIPTION OF THE BACKGROUND ART

Anaesthetic vaporizers are well known in the art and a large number of different methods of application are described in the literature. For a better understanding of the known and used vaporizers, reference is made to Anaesthetic Equipment, C. S. Ward, publisher Bailliere Tindall, 2nd edition, 1987, pp. 78-103, and to Anesthesia Vaporizers by J. B. Eisenkraft in Anesthesia Equipment, principles and applications, authors Jan Ehrenwerth, James B. Eisenkraft, publisher Mosby 1993, pp. 57-58.

The earlier described vaporizers are based on the principle of storing the liquid anaesthetic in a container. A breathing gas is introduced into this container and caused to pass over the surface of the liquid or to percolate there through.

Some of the anaesthetic is vaporized during passage of the breathing gas and therewith delivered to the patient together with the gas. This method, however, is encumbered with a large number of problems as described in US patent 6 155 255.

US Patent 6275 650 describes a vaporizer with a gas inlet 3 and a gas outlet 4 with a third inlet 6 for liquid anaesthetic gas. It also describes that it can be placed in the breathing circuit in several different ways but allways with a breathing gas inlet and outlet. This breathing gas is either air, oxygen or a mixture of air and oxygen, sometimes with an extra anaesthetic gas as nitrous oxide. The patent also describes (figure 2 and 3) that the gas supplied from the apparatus can be used directly for treatment of a patient without further dilution. This means that the concentration of the vapourized anaesthetic gas has to be low and the actual concentration is depending on the anaestheic used, the clinical situation and if the breathing gas contains further anaesthics. Irrespective of all these factors, the concentration of the vaporized anaesthetic gas always has to be below 20 %. The drawback with such a device is that it would be possible to deliver unvaporized liquid directly to the breathing circuit which is connected to a patient and thus it would be possible to deliver liquid anaesthetic to the patient. This would be a risk for the patient. This patent also describes the need of a liquid emitting device 5 (usually a porous plastic or the like). This liquid emitting device constitutes an extra complicated part which need to be very carefully dimensioned and heated. This adds to the complexity and cost to the vaporizer. The extra complexity in the design adds further risks to the patient.

DESCRIPTION OF THE INVENTION

The object of the present invention is to eliminate several of the drawbacks of the afore described systems and to provide a method and a device which will enable uniform vaporization of a large number of liquid anaesthetics in a large number of different gas mixtures and gas flows to be achieved.

According to the invention, this object is achieved with a device of the kind defined in the preamble of Claim 1 and having the characteristic features set forth in the characterizing clause of said Claim, and also by virtue of a method of the kind defined in the preamble of Claim 18 and comprising the particular steps set forth in the characterizing clause of the method Claim.

Thus, the invention is based on actively supplying the liquid to be vaporized to the heated chamber, therewith eliminating the drawbacks associated with those types of systems in which the vaporizer is charged with an initial quantity of liquid that is consumed in the course of the process and thereby influences the vaporization process.

It also eliminates the need of a specific liquid emitting device and thus makes the vaporizer less complicated.

The invention is based on the liquid delivery principle that only as much liquid is delivered to the heated chamber that can be gasified momentarily. This means that there will be mostly gasified anaesthetic in the heated chamber and as this gas has a volume of about 200 times a liquid anaesthetic, the gas will be forced out of the chamber at a rate of 200 times the supply rate of the liquid anaesthetic. Thus it is possible to deliver gasified anaesthetics at a known rate to patient gas delivery system. One other important difference compared to known vaporizers is the the gas outlet of the device delivers vaporized anaesthetic gas concentrations which are very high and which needs further dilution with breathing gases before it can be used to treat a patient.

Because the liquid delivery devices can be regulated, the variation in requirement can be readily adapted, for instance in respect of different types of anaesthetics to be vaporized.

In the case of one preferred embodiment of the invention, the liquid is supplied by means of a pump, preferably a motor-driven pump such as to achieve a positive and uniform supply and also to enable the supply to be readily adjusted. In the case of another preferred embodiment, the concentration of vaporized gas in the outgoing patient gas supply system is determined, preferably by an optical sensor conveniently adapted to control adjustment to the amount of liquid supplied.

These embodiments and other preferred embodiments of the invention are set forth in the dependent Claims.

The invention will now be described in more detail with reference to preferred embodiments thereof and also with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 to 7 describes variations around different embodiments.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Shown in FIG. 1 is a vaporization chamber 1 formed as a container. The illustrated container is tubular, although it may have any desired shape. The vaporization chamber 1 has an inlet opening 2 connected to a liquid inlet tube 5 and an outlet opening 3 connected to a gas outlet tube. The gas outlet tube is intended for connection to patient respiratory devices and gas delivery systems, in the illustrated case for the delivery of a mixture of breathing gases and an anaesthetic gas to a patient or animal. The inside of the container is heated by one or more nonporous surfaces 4 which gasify the liquid anaesthetic. The heat supplied to the surface 4 is supplied from an external energy source 15. A liquid supplier comprising a quantity regulator 7 is regulating the supply of liquid from the anaesthetic liquid source 6. The liquid regulator can be made in several ways. If the liquid source is a container which feeds the liquid by gravity force to the container the regulator could be a pinch valve. The regulator can also be a pump which includes a valve to control the liquid supply to the container. If the pump is self sealing (it does not let any liquid through when the pump is not pumping) then there may not be any need for an extra valve in the regulator. The pump may be motor driven. The heat supplied by the surfaces inside the chamber can be achieved in several ways from an external heat source 15. It can e.g. be electrically heated or be a heat exchanger with a heated liquid. Also use of other energy sources like microwaves could be used. The invention is not limited by the kind of energy source used for transferring heat to the vaporizing chamber. The concentrated gas from the heating chamber is transported into a breathing system 8 where it mixes with other breathing gases like air, oxygen or mixtures of these. As the delivery of concentrated gas to the breathing system is only depending upon the delivery rate of the liquid to the vaporizing chamber there is no need for a valve or a regulating means in between the vaporizing chamber and the breathing system. The regulation is taken care of by regulating the flow of liquid anaesthetic to the vaporizing chamber.

Figure 2 describes almost the same setup as in figure 1 and the number in the figures refers to the same features. To facilitate the regulating function of the regulator 7 it is connected to a regulator controller 9. This controller could be an electromechanical controller but also any other device where a certain set of parameters are set to control the regulator 7. The controller 9 can e.g. be a microprocessor with an ability to calculate suitable parameters for the regulator, based on type of anaesthetic, gas supply parameters to the patient, concentration set by the user as well as physiological parameters of the patient like age, weight, sex etc. It is therefore possible for the user to communicate with the controller 9 and this transfer the commands into suitable parameters for the regulator 7 as e.g quantity of liquid anaesthetic to be vaporized per unit of time. Figure 3 describes almost the same setup as in figure 2 (the numbers in the figures corresponds to the same features) but includes a sensor 10 which has the ability to sense the anaesthetic gas concentration. Although it is placed in figure 3 where the gas delivery tube enters into the patient breathing system, this placement can be varied. Depending on where the sensor 10 is placed various effects on the control system is achieved. If placed at the end of the gas outlet tube the sensor senses the gas outlet concentration. If placed in the patient breathing system it can measure the gas concentration inside this. If placed close to the patient it can measure the gas concentration given to the patient. Any of these placements can be used by the controller 9 to control the regulator 7 to give the correct amount of anaesthetic as set by the user. The sensor can be of many different kinds. It can e.g. be an optical sensor such as an infrared sensor sensing the anaesthetic gas concentration by changes in the infrared absorption at specific electromagnetic wavelengths. Other types of gas sensors can of course be used.

As known by those skilled in the art, such sensors could be either mainstream (i.e. the sensing element is placed directly on the gas stream to be measured) or side-stream (where a sample of the gas is withdrawn in a separate tube from the gas stream to be measured and analysed in a separate apparatus). Even if the figure describes a placement as if it would be a mainstream sensor it could equally well describe the sampling place for a side-stream sensor. The sensor 10 does not have to be directly controlling the regulator. It can also just show the concentration to the user and he will use this information to set the regulator at a suitable setting. The sensor does not have to be a gas sensor specific for a certain gas. It can also be a sensor measuring the gas mass flow through the gas delivery tube. This could be especially good for regulating the gas delivery to the breathing system.

Although only one sensor is shown in the picture, several sensors could be used. These could be the same kind or different kinds. Figure 4 describes almost the same setup as in figure 3 (the numbers in the figures corresponds to the same features) but includes a separate gas supply system 11 which is not directly connected to a ventilator or the like . This gas supplied is usually oxygen, nitrogen, air or mixtures thereof. Other gases might be used if found suitable and not toxic to the patient. The amount of gas supplied might be varied but usually it is supplied at a rather low rate (compared to the rate of gas supplied to the patient). The rate is enough for transporting gasified anaesthetic out of the chamber 1 and the outlet tube to the breathing system 8. Of course will this gas supply reduce the gas concentration from 100% to something less depending on the supply of gas and the liquid anaesthetic. This supply of gas shall be kept at a very low rate in which way the volume of it will not particularly be an important part of the gas volume given to the patient. The gas supply could be kept at a rate suitable to reduce or eliminate the condensation of gas inside the gas outlet tube.

Figure 5 describes another way of reducing the condensation inside the outlet tube. The outlet tube has at least one heated surface along the entire tube. The temperature of this surface is kept at a value high enough to eliminate the condensation of the anaesthetic inside the tube. This heat could be supplied in many different ways like electricity, heated water or heated air from an external energy source 14. It could be supplied as a heat source inside the tube surrounded by the gas flow or it could be integrated into the walls of the tube. It could be electrical wires or electric conducting plastic material. Any of these heat sources could be controlled by a separate temperature controller and/or a temperature sensor (not shown). Even if this heated tube is only shown in this figure and the figures described below it does not mean that it could not be used together with any of the configurations described above.

Figure 6 describes another way of reducing the condensation inside the outlet tube. It includes a separate gas supply pump 13 which is controlled by a controller 9. In this way it may be possible for the user to set the pumping rate of 13 to a value suitable to reduce the condensation either alone or in combination with a suitable temperature on the surface 12 inside the outlet tube. This controlling action could be made automatic by the controller 9. The temperature of the inside of the outlet tube can of course be controlled by either the controller 9 or by a separate controller.

The controller 9 in these figures can of course be a mechanical, an electromechanical, an electronic or a microprocessor equipped controller.

Figure 7 describes another aspect of this invention. In this figure the inlet tube, the vaporization chamber and the outlet tube are all combined in one heated tube. This is particularly convenient as the number of parts needed is reduced to a minimum and the risk of leakage and disassembly of the components is almost eliminated. Of course could this be combined with a gas supply like number 11 in figures 4-6 even if it is not shown.

Claims

What is claimed is:

1. A vaporizer for an anaesthetic liquid, comprising a vaporizing chamber which includes a liquid inlet and a gas outlet and which accommodates at least one heated nonporous surface to which the anaesthetic liquid which is to be vaporized is exposed, the liquid inlet being connected to an anaesthetic liquid supplier that communicates with an anaesthetic liquid source, wherein said anaesthetic liquid supplier includes a liquid quantity regulator and the gas outlet being always open to a patient circuit which supplies gas to and from a patient.

2. The vaporizer according to claim 1 , wherein said gas outlet includes a gas outlet tube and an inspiration means connected to a breathing circuit for the treatment of human beings or animals.

3. The vaporizer according to claim 2, wherein said liquid supplier includes a pump.

4. The vaporizer according to claim 3, wherein said pump is controllable to thereby form a component in said liquid quantity regulator.

5. The vaporizer according to claim 3, wherein said pump is motor driven.

6. The vaporizer according to claim 5, wherein the liquid quantity regulator is adapted to deliver per unit of time a quantity of liquid that is at most equal to the quantity of liquid that is vaporized per unit of time in said vaporizing chamber.

7. The vaporizer according to claim 5, comprising a sensor adapted to sense the amount of vaporized liquid, said sensor being provided downstream of said chamber outlet.

8. The vaporizer according to claim 7, wherein the sensor includes an optical sensor.

9. The vaporizer according to claim 7, wherein said liquid quantity regulator is adapted to regulate the supply of liquid in response to signals from said sensor.

10. The vaporizer according to any of the claims 1 to 9, wherein said vaporizing chamber includes a gas supply supplying air or oxygen or mixtures thereof.

11. The vaporizer according to any of the claims 2 to 10 where at least part of the inside of the chamber outlet tube is heated with an external energy source.

12. The vaporizer according to claim 11 where the whole length of the inside of the chamber outlet tube is heated with an external energy source.

13.The vaporizer according to any of the forgoing claims in which the chamber and outlet tube is one continuous tube from the liquid supplier to the outlet.

14. The vaporizer according to any of the claims 10 to 13 where the gas supply is regulated to give an anaesthetic gas concentration in the chamber outlet tube of at least 20%.

15. The vaporizer according to claims 10 to 13 where the gas supply includes a gas pump.

16. The vaporizer according to claim 15 where the gas pump is controlled by external means to give a set concentration to the patient.

17. The vaporizer according to claim 16 where the gas pump controller and the liquid pump controller are regulated by external means to give a set concentration to the patient.

18. A method of vaporizing an anaesthetic liquid, which comprises the steps of: delivering an anaesthetic liquid from an external liquid source to a liquid delivery device; and exposing said liquid to a heated surface to vaporize the liquid completely and deliver the vaporized liquid to a breathing circuit without any gas regulating means in between the heated surface and the patient.