Electronic vaporizer with active mesh nebulizer

Abstract

The invention provides an electronic vaporizer and corresponding method for delivering anaesthetic agent to a breathing patient, wherein such delivery, in the form of micron scale droplets, can be statically and dynamically controlled.

Description

[0001] ELECTRONIC VAPORIZER WITH ACTIVE MESH NEBULIZER

[0002] Technical field

[0003] The invention generally relates to the field of an anaesthesia delivery system and a method for delivering anaesthetic agent into a breathing air of a patient, in particular for example via the fresh gas supply of a patient. More particularly, the invention relates to anaesthetic vaporizers.

[0004] Background of the invention

[0005] Inhalational anaesthetic agents are usually liquids at room temperature and barometric pressure and need to be converted to vapor before being used. Such conversion is effected using a vaporizer. In general, modern vaporizers are designed to be used between the flow meter and the common gas outlet on an anaesthesia machine, and are controlled by a central processing unit provided herewith. In contrast to this, in-line anaesthetic vaporizers (used with a reflector) can be attached to the inspiratory limb of a ventilator.

[0006] Modern vaporizer are used to reliably deliver an accurate, adjustable concentration of anaesthetic vapor, being continuously monitored. In order to give clinically useful concentrations of the agent, the anaesthetic vapor has to be diluted with fresh gas in one of the following two ways. With variable bypass vaporizers, this can be done by splitting the fresh gas flow so that only a portion passes through the vaporizing chamber and the rest bypasses it. Alternatively, when using measured flow vaporizers, the adjustment occurs by injecting the vapor directly to the total fresh gas flow without any split. For any type of vaporizer being used, the outcome is that the anaesthetic agent will hence arrive (together with fresh gas) in the breathing circuit of a patient. The output of inhalational agents can be electronically and pneumatically controlled.

[0007] Nebulizers are commonly used to deliver aerosolized medications in the treatment of patients with pulmonary diseases. They transform liquid formulations and suspension into medical aerosol. Control of droplet size plays a crucial role in delivering of medication to the lungs and an optimum droplet size is for example in the range of 1 to 10 pm for efficient delivery and treatment. There are three types of nebulizers: jet nebulizers, ultrasonic nebulizers, and mesh nebulizers. Jet nebulizers require 2 to 10 L / min of pressurized gas to draw medication up through a capillary tube from the nebulizer reservoir in order to generate a wide range of particle sizes that are blasted into one or more baffles, which take larger particles out of suspension and return them to the reservoir. Ultrasonic nebulizers incorporate a piezoelectric crystal vibrating at high frequencies (1-3 MHz) and generating acoustic signal traveling through the liquid towards the liquid surface. This induces capillary waves at the liquid surface in order to produce aerosol. In general, ultrasonic nebulizers have many limitations compared to jet nebulizers.

[0008] More recently developed are mesh nebulizers, using micropump technology for aerosol production. Via multiple apertures in a mesh or aperture plate, they are forcing or "pushing" liquid medications, in order to generate aerosol. Mesh nebulizers are small and portable, and can be powered by either battery or electricity. Having an increased output efficiency as compared to other nebulizer types, mesh nebulizers are particularly characterized by a consistent and improved aerosol generation efficiency, and a predominantly fine-particle fraction reaching into the peripheral lung. Further advantages include low residual volume, and the ability to nebulize in low drug volumes. The size of the pore, the aerosol chamber, and the reservoir, as well as the output rate of mesh nebulizers, can be adjusted for different drugs in order to optimize aerosol drug delivery to patients. Mesh nebulizers can be classified into two categories: active and passive mesh nebulizers. Active mesh nebulizers are using a piezo element that contracts and expands on application of an electric current, and vibrates a precisely drilled mesh in contact with the medication in order to generate aerosol. Passive mesh nebulizers are using a transducer horn that induces passive vibrations in the perforated plate with thousands of tapered holes to produce aerosol. It is noted that, while comprising a piezo element or transducer, thus an ultrasonic component, mesh nebulizers may in fact also be interpreted as a kind of ultrasonic nebulizers. However, they are categorized differently because of their specific mesh feature.

[0009] Aim of the invention The aim of the invention is to provide an apparatus and corresponding method for delivering anaesthetic agent to a breathing patient, wherein such delivery, in the form of micron scale droplets, can be statically and dynamically controlled.

[0010] Summary of the invention

[0011] In a first aspect, the invention provides an apparatus for administering an anaesthetic agent for a patient breathing. The apparatus comprises a liquid reservoir for an anaesthetic agent, an airway tube for transferring or passing breathing gases, and an anaesthetic agent dosing unit in connection with the liquid reservoir and connected to the airway tube. The anaesthetic agent dosing unit comprises a plate provided with one or more transducers to produce and evaporate and / or nebulize anaesthetic agent droplets directly into the connected airway tube. The plate is possibly a removable plate, which means that for example it could be extended and retracted in order to change, replace, remove or add one or more of the transducers provided thereon. Hence, the transducers can also be removable and interchangeable depending on the needs and specific requirements of anaesthetic agent to be delivered to the patient. The transducers can be ultrasonic mesh transducers, for example comprising a thin metal disc and a ceramic piezo ring mounted thereon. Each of the transducers is at least partially perforated (e.g. in particular the centre of the metal disc) and thus comprises a plurality of pores, via which the anaesthetic liquid is pushed and hence droplets are formed by means of vibration of the transducers. In addition, because of the structure and / or geometry of the apparatus, wherein the liquid reservoir is mounted above the anaesthetic agent dosing unit with transducers, and the airway tube is below the anaesthetic agent dosing unit, the anaesthetic liquid is also automatically led or guided towards the pores of the transducers due to gravity. As a result, droplets are produced to be evaporated and / or nebulized directly in the airway tube wherein breathing gases are passing and just below the transducers where the droplets are formed. In other words, there is no intermediate stage (such as in the form of a vaporizing chamber) for delivering the produced and evaporated and / or nebulized droplets to the passing breathing gases. According to an embodiment, the orientation and / or building or mounting structure of the three main parts the apparatus, i.e. the liquid reservoir, the anaesthetic agent dosing unit and the airway tube, is configured such that the liquid reservoir is (entirely) mounted on top of the anaesthetic agent dosing unit while being (directly) connected therewith, whereas the anaesthetic agent dosing unit is mounted on top of (at least part of) the airway tube while being (directly) connected therewith. The liquid reservoir being entirely mounted on top of the anaesthetic agent dosing unit, means that this latter is for example not (partially) submerged into the liquid reservoir, but entirely separated therefrom as a separate unit although being directly connected therewith. The anaesthetic agent dosing unit being mounted on top of at least part of the airway tube, means that for at least some part of the airway tube, the airway tube is below the anaesthetic agent dosing unit, which e.g. middle part of the airway tube, whereas closer to its outer end (i.e. input and output) part of the airway tube may be mounted differently. According to an embodiment, the gravity aspect of the liquid in the liquid reservoir is taken into account such that it gets pushed against the transducers of the anaesthetic agent dosing unit mounted there below, and therefore less power is needed regarding the activation (i.e. vibration) of the transducers for the liquid to be pushed (due to vibration) through the pores of the transducers. In other words, due to apparatus set-up or construction and hence gravity aspect, the energy efficiency in activation of the apparatus may be improved. The pores are typically very small, and may have a diameter of 0,1- 500 pm, preferably 0,1-20 pm, more preferably 0,1-10 pm. As a result, very small (micron or submicron) droplets are produced. The small droplet or particle size may allow for an optimal vaporization in the fresh gas (flow) due to an increased contact surface with the environment. Because of the small droplets and hence their increased contact surface (as compared to larger particles), the evaporation and / or nebulization can occur directly, much easier and with less energy needed as compared to for example systems in the art where additional heating is required. Such additional heating for example goes along with providing a vaporizing chamber, determining and loading specific temperatures for this chamber, considering vaporizing and droplet (surface) characteristics, and performing calculations and / or computations regarding required droplet size etc. As a result, additional heating has a cumbersome effect and a significant impact of the execution and energy needed for the apparatus. As opposed to the art, and in accordance with the invention, providing transducers with small pore sizes to be chosen, as presented in current design or configuration, may lead to an improved energy efficiency. According to an embodiment, the pore sizes are optimally chosen, such that no or minimum additional heating is required for the produced droplets to evaporate and / or nebulise and hence directly can be mixed with passing breathing gases in directly connected (part of the) airway tube just below where the droplets are formed or released from the transducers. In this way, the activation of the transducers directly leads to an appropriate size of droplets generated to be directly evaporated and / or nebulised in passing breathing gases of the airway tube. The fact that no or only minimum additional heating is then needed, may further result in improved power management and power use of the apparatus, and hence may further improve the energy efficiency and energy use of the apparatus. Each of the transducers may have pores with different pore sizes (per transducer), and / or amongst the transducers, the pore sizes may vary. The airway tube comprises three main parts that merge into each other: a first part for receiving passing breathing gases, a second part for mixing the passing breathing gases with the anaesthetic agent droplets produced by the one or more transducers, and a third part for transferring the passing breathing gases having been mixed with the anaesthetic agent droplets, to be delivered to the patient breathing. The passing breathing gases that are received in the first part are typically delivered from a supply tank that is connected to the breathing circuit of the patient. Further connected to the breathing circuit, could be an anaesthesia system and / or an anaesthesia machine. The passing breathing gases may comprise for example fresh gas or air, oxygen i.e. O2 and possibly N2O. In the second part, these breathing gases are mixed with (sub)micron (liquid) droplets of anaesthetic agent that are evaporated and / or nebulized when the flow of breathing gases is passing by in this second part. The third part typically contains the breathing gases having been mixed with anaesthetics, and hence this mixture can now be further transferred towards the patient being connected to the breathing circuit. This process usually runs continuously, without any obstructions. The apparatus, which may be included in an anaesthesia system, could be an anaesthetic vaporizer, or else could be part of an anaesthetic vaporizer, or the apparatus could be assembled with or either incorporated in an anaesthetic vaporizer. According to an embodiment, the apparatus (for administering an anaesthetic agent for a patient breathing) has no additional heating. According to another embodiment, the apparatus is provided with minimum additional heating, for example by means of a heater being provided in the airway tube, in particular in the second part thereof where evaporated and / or nebulized anaesthetic agent droplets are mixed with passing breathing gases. With such heater, the ambient temperature within the airway tube (e.g. specifically in the area or part where mixing of droplets and passing breathing gases takes place) can be increased for instance to 35°-45° Celsius. According to an embodiment, the plate comprises at least two transducers. For example, the plate may comprise six or eight transducers. One or more of the transducers may have different sizes, for example they may differ in diameter, and / or in thickness. A difference in diameter may imply a smaller or larger perforated centre, and hence may lead to respectively a lower or higher production of anaesthetic agent droplets. The transducers comprising a plurality of pores may also have different pore sizes, and herewith produce anaesthetic agent droplets of different sizes. The transducers could be mounted directly on the plate, or else the plate may comprise two or more holes into which respective transducers can be mounted using a seating for each of the transducers. According to a preferred embodiment, these holes are identical, as well as the seating to be put in a hole, and used for mounting different types (e.g. in size, in pore size) of transducers. Hence, the transducers may vary in size, whereas any seating can have one size and format fitting into the identical holes of the plate, and wherein various types of mesh transducers may fit. The transducers may comprise a different number of pores, as well as the pores may differ in size from one disc to another. By using different types of mesh transducers (e.g. varying in size, number of pores, pore size etc.), more or less droplets can be produced, and / or different droplet sizes can be achieved. The transducers can be wired and electrically connected to be controlled. Such control may be dynamic and even real-time during operational use of the apparatus.

[0012] According to an embodiment, the apparatus further comprises a liquid level indicator, such as for example a floater, and / or a liquid level sensor be it either a relative or an absolute liquid level sensor.

[0013] According to an embodiment, the apparatus further comprises a flow sensor for measuring a gas flow, e.g. velocity of gas, in the airway tube. Such flow sensor may be connected with a processor or microprocessor to which the measuring is transferred, and subsequently interpreted by the processor or microprocessor, for controlling and / or monitoring the transducers, and hence not only following but also adapting the production, evaporation and / or nebulization of anaesthetic agent droplets depending on the measured gas flow. According to an embodiment, the apparatus further comprises a print board or PCB provided with electronics and electric wires to be connected to one or more parts of the apparatus, amongst which for example the transducers, the liquid level sensor and / or the flow sensor.

[0014] According to an embodiment, the apparatus further comprises a wire tray comprising multiple channels for guiding the electric wires and comprising recesses for fluid passage to the transducers. The wire tray may further comprise connectors for connecting the electric wires with the transducers, and hence connecting the transducers with the electronics, e.g. provided on the print board.

[0015] According to an embodiment, the apparatus further comprises a heater or heating tray comprising a heating element for heating (part of) the apparatus, in particular for example (part of) the airway tube, and more particular for example first part of the airway tube wherein received fresh gas is flowing. By means of heating the fresh gas, a resulting higher temperature of the fresh gas may allow further optimal vaporization of the anaesthetic agent droplets in the fresh gas (including e.g. better absorption of droplets).

[0016] In addition to the flow sensor for measuring the flow of the fresh gas, in order to know and possibly adjust the output of the transducers (open loop - relative control), the invention does not exclude the possible use of a gas sensor for measuring the gas concentration and to feedback this (gas concentration) information to the output of the transducers (closed loop - absolute control). Hence, according to an embodiment, the apparatus further comprises a gas sensor for measuring an amount of anaesthetic agent or anaesthetic agent concentration (mixed) in the airway tube. The gas sensor can be connected with a (micro)processor to which the measuring is transferred, and subsequently interpreted by the (micro)processor. Moreover, the gas sensor may be connected with the anaesthetic agent dosing unit for controlling an anaesthetic agent delivery based on the measuring of the amount of anaesthetic agent or anaesthetic agent concentration. Hence, the amount of anaesthetic agent droplets to be supplied can be adapted depending on the (real-time) (mixed) gas concentration measured. Controlling the anaesthetic agent delivery may be performed by means of activating or deactivating one or more of the transducers (voltage driven) in function of the chosen anaesthetic agent percentage setting, installed by the user, and / or by means of adding or removing one or more of the transducers, and / or by means of changing or replacing one or more of the transducers.

[0017] According to an embodiment, the provision of the flow sensor for measuring the gas flow, leads to an open loop control. Moreover, the measurements are relative measurements, resulting into a relative control. Delivering more or less power to the transducers is based on the measured gas flow. For example, this means that an increased gas flow (as measured) will require to deliver relatively more power to the transducers, whereas a lower gas flow will lead to less power needed for the transducers. When using the flow sensor, the more or less power to be delivered can be controlled or arranged by means of the time of activation the transducers. In other words, the time signal for activating the transducers can be adjusted. For example, a square wave is considered for the time signal, in particular defined by 1 second ON and 1 second OFF. Delivering more power can then simply be arranged by having or installing a longer ON time than 1 second for the time signal (e.g. while the OFF time remains the same). Another way of manipulating the amount of power to be delivered to the transducers, could be by adjusting the voltage (e.g. by means of a potentiometer, adjust between 0-5V) depending on the relative gas flow measurement. It is herewith noted that the setting frequency of the transducers is for instance about 100 kHz (depending on the electronics used), and generally remains unchanged during the operation thereof. It is herewith noted that there is a way to measure the natural frequency of the piezo crystal in order to adjust the frequency accordingly. Hence, the frequency can vary, though slightly, not in large jumps.

[0018] According to an embodiment, instead, the provision of the gas sensor for measuring the gas concentration, leads to a closed loop control. Moreover, the measurements are absolute measurements, resulting into an absolute control. Adjusting the transducers may now occur much more precisely and accurately than with the relative measurements and corresponding open loop control.

[0019] It is noted that using the transducers may be either statically or dynamically controlled, meaning that a certain number, and certain types, may be pre-selected for use (i.e. static control) but not all of those pre-selected transducers need to be activated during the entire operational use of the apparatus (i.e. dynamic and possibly real-time control). For example when having two types amongst the pre-selected transducers, it could be that only one type is active at a time.

[0020] According to an embodiment, the apparatus comprises one or more sensors being entirely integrated and / or incorporated therein. The sensors may be e.g. flow sensors and / or gas sensors as referred to above, but could also be for example pressure sensors, temperature sensors or any other sensor indicating a required parameter during operation of the apparatus.

[0021] In a second aspect, the invention provides a system for an anaesthesia machine, comprising an apparatus for administering an anaesthetic agent for a patient breathing, in accordance with the first aspect.

[0022] According to an embodiment, a gas sensor is provided or added, possibly in the anaesthesia machine, and thus not necessarily in the first aspect apparatus or in the anaesthetic vaporizer being or comprising such first aspect apparatus. The gas sensor can measure the concentration of the gas and then pass this gas concentration information on to the (micro)processor, which can then respond (in order to have a closed loop feedback).

[0023] According to an embodiment, the system comprises one or more (internal) sensors being entirely integrated and / or incorporated therein, whereas in addition, one or more additional sensors may be provided externally. The (internal) sensors may be part of the first aspect apparatus, or of the anaesthetic vaporizer comprising such apparatus. Alternatively, the (internal) sensors could also be part of the anaesthesia machine comprising the first aspect apparatus, and / or the anaesthetic vaporizer. In case of sensors being provided externally, or (internal) sensors not being part of the first aspect apparatus, or of the anaesthetic vaporizer comprising such apparatus, precautionary measures can be taken to enable the necessary connections of any internal and / or external parts.

[0024] In a third aspect, the invention provides a method for administering an anaesthetic agent for a patient breathing, comprising the following steps: (i) receiving passing breathing gases, e.g. including at least oxygen, for the patient breathing e.g. via a first part of an airway tube; (ii) providing a liquid containing the anaesthetic agent e.g. in a liquid reservoir; (iii) producing anaesthetic agent droplets from the liquid by means of an anaesthetic agent dosing unit comprising one or more transducers, wherein the transducers, possibly being removable and / or interchangeable, and for example of the ultrasonic mesh type, are provided on a plate, also possibly removable; (iv) delivering the anaesthetic agent droplets (directly) to the passing breathing gases e.g. in a second part of the airway tube; (v) evaporating and mixing, e.g. by nebulization the anaesthetic agent droplets with the passing breathing gases e.g. in the second part of the airway tube; and (vi) transferring the evaporated anaesthetic agent mixed with the passing breathing gases e.g. in a third part of the airway tube, and supplying it to the patient breathing. By means of gravitation of the liquid and activation (i.e. vibration) of the transducers comprising a plurality of pores, the liquid may penetrate through the anaesthetic dosing unit, in particular through the pores of the transducers. The first, second, and third parts of the airway tube are directly connected to each other, whereas the airway tube may be connected with an anaesthesia machine.

[0025] In a fourth aspect, the invention provides a method for controlling an anaesthetic vaporizer in an anaesthesia machine, comprising the following steps: (i) supplying (electric) power to one or more transducers, wherein the transducers, possibly being removable and / or interchangeable, and for example of the ultrasonic mesh type, are provided on a plate, also possibly removable, of the anaesthetic vaporizer; (ii) operating the transducers configured to evaporate and / or nebulize liquid anaesthetic agent and deliver the nebulized anaesthetic agent to an airway tube of the anaesthetic vaporizer for passing breathing gases e.g. including at least oxygen; (iii) measuring a (mixed) gas flow output by means of a flow sensor e.g. provided in the airway tube of the anaesthetic vaporizer; and (iv) controlling and possibly also monitoring the transducers based on the (mixed) gas flow measuring. According to an embodiment, the method further comprises the step of (v) measuring an amount of anaesthetic agent output by means of a gas sensor e.g. of the anaesthetic vaporizer or of the anaesthesia machine; and (vi) controlling an anaesthetic agent delivery based on this measuring e.g. by adapting the power supplied and / or the operating of the transducers. The method with the additional gas sensor describes a closed loop control, whereas with the flow sensor only an open loop control is described determined by a frequency setpoint. The gas flow(rate) determines the power (required or to be delivered) to the transducers and can possibly be adjusted based on gas flow measurements by means of the flow sensor. In a further aspect, the invention provides a method for controlling an anaesthetic vaporizer in an anaesthesia machine, comprising: (i) supplying power to one or more transducers provided on a plate of the anaesthetic vaporizer; (ii) operating the one or more transducers configured to deliver the evaporated and / or nebulized anaesthetic agent directly to an airway tube of the anaesthetic vaporizer; wherein (in order to minimize the required supplied power) the determining of the required supplied power for delivering the nebulized anaesthetic agent directly to an airway tube of the anaesthetic vaporizer takes into account explicitly the gravity acting on the liquid anaesthetic agent (in the liquid reservoir).

[0026] In a further aspect, the invention provides a method for controlling an anaesthetic vaporizer in an anaesthesia machine, comprising: (i) supplying power to one or more transducers provided on a plate of the anaesthetic vaporizer; (ii) operating the one or more transducers configured to produce anaesthetic agent droplets and to evaporate and / or nebulize liquid anaesthetic agent and deliver the evaporated and / or nebulized anaesthetic agent directly to an airway tube of the anaesthetic vaporizer; wherein (in order to minimize the required supplied power and eventually other possibly required power for e.g. further heating for evaporation purposes) the determining of the required supplied power takes into account its effect on the anaesthetic agent droplets size and subsequently the anaesthetic agent droplets size on the evaporation and / or nebulization of the liquid anaesthetic agent.

[0027] It is noted that the embodiments described above regarding a method for controlling an anaesthetic vaporizer in an anaesthesia machine can be combined, either entirely or at least in part certain features are combinable.

[0028] In a further aspect, the invention provides a method for operating an anaesthetic vaporizer in an anaesthesia machine, comprising the following steps: (i) receiving an anaesthetic agent concentration setpoint; (ii) receiving a fresh gas flow rate for breathing gases e.g. including at least oxygen, entering the anaesthetic vaporizer via an airway tube (via which the breathing gases may further pass); (iii) supplying (electric) power to one or more (removable) (interchangeable) (ultrasonic) (mesh) transducers provided on a (removable) plate of the anaesthetic vaporizer, wherein the to be supplied (electric) power being based on the anaesthetic agent concentration setpoint and the fresh gas flow rate, and wherein the transducers are configured to evaporate and / or nebulize liquid anaesthetic agent and deliver the nebulized anaesthetic agent to the airway tube with passing breathing gases, to herewith enable vaporized anaesthetic agent delivery to a patient; (iv) measuring a (mixed) gas flow supplied to the patient by means of a flow sensor e.g. provided in the airway tube of the anaesthetic vaporizer; (v) controlling and / or monitoring the transducers e.g. by adapting the power supplied to the transducers by modifying the to be supplied (electric) power based on the (mixed) gas flow measuring; (vi) determining a concentration of the anaesthetic agent supplied to the patient by means of a gas sensor e.g. of the anaesthetic vaporizer or of the anaesthesia machine; (vii) calculating an anaesthetic agent concentration error that represents a difference between the anaesthetic agent concentration setpoint and the determined anaesthetic agent concentration; and (viii) controlling e.g. by adapting the power supplied and / or the operating of the transducers, an amount of anaesthetic agent output by the anaesthetic vaporizer based at least in part on the calculated anaesthetic agent concentration error.

[0029] This disclosure provides various examples, embodiments, and features which, unless expressly stated or which would be mutually exclusive, should be understood to be combinable with other examples, embodiments, or features described herein.

[0030] Brief description of the drawings

[0031] Figure 1 illustrates an embodiment of an apparatus for administering an anaesthetic agent for a patient breathing, in accordance with the invention.

[0032] Figure 2 illustrates another embodiment of an apparatus for administering an anaesthetic agent for a patient breathing, in accordance with the invention.

[0033] Figure 3 illustrates further detail of lower modules of the embodiment of Figure 2.

[0034] Figure 4 illustrates further detail of upper modules of the embodiment of Figure 2.

[0035] Figure 5 illustrates enlarged cross sectional view of part of an apparatus for administering an anaesthetic agent for a patient breathing, in the particular in the area of a transducer where micro droplets are formed, in accordance with an embodiment of the invention. Figure 6 illustrates an embodiment of a system for an anaesthesia machine connected to a breathing circuit, in accordance with the invention.

[0036] Detailed description of the invention

[0037] The invention provides the advantage of providing an apparatus and corresponding method for delivering anaesthetic agent to a breathing patient, wherein such delivery, in the form of (sub)micron scale droplets being evaporated and / or nebulized, can be statically and dynamically controlled. For example by adjusting the speed, amount and / or size of the droplets being delivered, this (even real-time) control can be defined. The adjustment in output of anaesthetic agent is determined by the configuration and conceptual design of the anaesthetic vaporizing and / or nebulizing apparatus in accordance with the invention. Typical anaesthetic agents used are for example halothane, isoflurane, sevoflurane and desflurane, whereas typical percentages may vary between 1-10%, although higher percentages are not excluded. Desflurane for instance may be administered up to 18%.

[0038] According to an embodiment, the invention provides an electronic anaesthetic vaporizer with active mesh nebulizer, for forcing an anaesthetic agent in the form of liquid towards a suspension for delivering anaesthetic aerosol to fresh gas into the breathing circuit of a patient. The active mesh nebulizer may comprise an ultrasonic mesh transducer, comprising two discs on top of each other. According to an embodiment, one disc is made of a piezoelectric element, while the other is made of a metal (e.g. stainless steel or titanium, resistant to corrosion of the liquid used to be nebulized). In the centre of the metal disc, very small holes or apertures (typically of micrometre dimensions) are provided such that the liquid can be forced or "pushed" there through due to ultrasonic vibrations generated by the piezoelectric element. In particular, the nebulizer uses ultrasonic energy, as generated by the piezoelectric element, to create high-frequency vibrations, which are transferred to the metal (being in direct contact with the piezoelectric element via their respective disc surface). The vibrating mesh can move back and forth quickly, causing oscillation of the mesh, and creating a pressure wave. When liquid medicine comes into contact with the mesh, the liquid is forced through the small holes. When the liquid then passes through the mesh, it is broken into small droplets by the high-frequency vibrations. This atomization process of the liquid effectively atomizes the liquid and converts it into a fine aerosol nebulization. The resulting nebulization comprises extremely fine particles, which can then be mixed with fresh gas flow, herewith delivering the anaesthetic agent (in the form of (sub)micron scale droplets being mixed with breathing gases) directly into the lungs of a patient.

[0039] The vibrating mesh nebulizer in accordance with an embodiment of the invention, is capable of producing micro droplets for anaesthetic agent delivery. The core element of the nebulizer, i.e. the vibrating mesh, is for example made from metal, or fabricated using silicon process and comprises hundreds or thousands of tapered micro-sized apertures. During operation the mesh will vibrate at high frequency such as in the range of 1 kHz to 1 MHz (possibly to 3 MHz), particularly for example at 100 kHz. It is known from the art that, as regard to aerosol deposition and particle sizes, 5-10 pm particles deposit mostly in the conducting airways as they generally reach the proximal generations of the lower respiratory tract, whereas particles of 1-5 pm reach to the lung periphery. Hence, in order to have an optimal distribution and absorption of the anaesthetic agent in the lungs, the droplet diameter is for example in the range of 1 to 10 pm, in particular for example a few pm, whereas a typical output rate for instance is in the range of 0,1 to 1 ml / min, in particular e.g. 0,5 ml / min. These ranges may provide an optimal vaporization of the anaesthetic agent in the fresh gas flow.

[0040] A generic concept of vibrating mesh technology typically comprises a mechanically vibrating plate perforated with micro-size apertures. The mesh may be assembled with a metallic holder and piezoelectric ring actuator. Optionally, as proposed in an embodiment of the invention, a seating is included for mounting the metal disc and actuator ring. During operation the liquid is in contact with one side or surface of the mesh, which is excited into out-of-plane vibration by the laterally vibrating piezoelectric actuator. As regard to this latter, it is noted that, in fact, the vibrating has no specified direction. But because of the design of the ring, the vibrating can have a profound direction. For a small amount, vibrations in another direction may also occur. Although, in general, there is no preferred vibrating direction, it is noted that the nebulization will normally occur in a specific direction. Alternating vibration of the mesh builds up alternating pressure in the liquid in the vicinity of the mesh pushing the liquid through the apertures and ejecting aerosol droplets on the other side of the mesh. Vibrating mesh technology is advantageous over other technologies as it does not destroy the anaesthetic agent due to heat and high pressure, the nebulization process is fast and quiet, and the nebulizers are small and portable. Whereas typically, standard state-of-the-art mesh devices are made of metal alloys and are fabricated using electroforming and laser drilling techniques, an enhanced (e.g. in terms of reliability, minimum aperture size and functionality) and cheaper solution may be provided by employing MEMS (Micro-Electro-Mechanical Systems) fabrication techniques to develop a silicon-based vibrating mesh.

[0041] According to an embodiment of the invention, a mesh plate or tray (preferably removable or extendable) is provided comprising multiple (preferably identical) holes for mounting mesh devices (or transducers) or meshes, each possibly including a general (i.e. one size / format) seating, such that each transducer assembly (i.e. mesh + seating) has the same shape and can be easily incorporated into one of the (preferably identical) holes of the mesh plate, intended for multiple mesh transducers that are possibly statically and / or dynamically controlled. By statically controlled is meant that one or more meshes can for example be added, removed, replaced or interchanged (when removing / extending the mesh plate or tray). By dynamically controlled is meant that the one or more meshes, being electrically connected, can be activated or inactivated, or in particular e.g. amongst them a particular type (in size, amount of pores, pore size) is selected to be active or inactive.

[0042] The anaesthetic apparatus in accordance with embodiments of the invention comprises multiple separated modules, amongst which for example a liquid reservoir, an airway tube, and an anaesthetic agent dosing unit. Moreover, the anaesthetic agent dosing unit may comprise multiple components for providing anaesthetic dosage. Because of the modular configuration and the possibly multiple dosing components provided by the invention, a sustainable and environmental friendly solution (having a long lifetime) in electronic anaesthetic vaporizing systems is presented.

[0043] The invention is now further described by means of different embodiments, for which is also referred to Figures 1 to 6. Figure 1 illustrates an embodiment of an apparatus 100 for administering an anaesthetic agent 10 to a (breathing) patient, in accordance with the invention. As shown in Figure 1 (a), which is a cross- sectional side view of the apparatus, the anaesthetic apparatus 100 comprises three main parts: a liquid reservoir 110 for an anaesthetic agent 10, an airway tube 120 for gas flow 20 (all or not mixed), and an anaesthetic agent dosing unit 130 for delivering, i.e. evaporating and / or nebulizing anaesthetic agent droplets 30 to the (fresh) gas flow 20 passing by. The anaesthetic agent dosing unit 130, having two sides, is on one side in connection with the liquid reservoir 110. This connection can be referred to as a fluid connection, whereas the anaesthetic agent dosing unit 130 is in contact with a liquid, here the anaesthetic agent 10, to be comprised in the liquid reservoir 110 in case this latter is filled. On its other side, the anaesthetic agent dosing unit 130 is in connection with the airway tube 120, which could also be referred to as a fluid connection, whereas a gas flow or gas stream is passing the airway tube 120. It is noted that herewith stated fluid connection (on one side or the other of the anaesthetic agent dosing unit 130) can hence be a connection with either liquid or gas. The anaesthetic agent dosing unit 130 comprises a plate 131 with one or more (ultrasonic) (mesh) transducers 132 to produce and evaporate and / or nebulize anaesthetic agent droplets 30, which may have a diameter of 0,1-100 pm, preferably 0,1-20 pm, more preferably 0,1-10 pm. The plate 131 may be extendable or removable such that the one or more transducers 132 thereof can be easily removed or added, replaced and / or interchanged. The transducers 132 are typically ultrasonic transducers. In particular ultrasonic mesh transducers, for example in the form of disks are used. The airway tube 120 can also be divided into three parts: a first part 121 for receiving gas flow 20, here specifically in the form of passing breathing gases (for example fresh gas or air, O2 + N2O), a second part 122 for mixing such passing breathing gases 20 with the anaesthetic agent droplets 30 as being produced and evaporated and / or nebulized by the one or more transducers 132, and a third part (not shown) for transferring the passing breathing gases 20 having been mixed with the anaesthetic agent droplets 30, to be finally delivered to the patient breathing. Furthermore, the airway tube 120 has an input / output component 102, wherein an input port 124 and an output port 125 are provided as depicted in Figure 1 (b), showing a back view of the apparatus in accordance with an embodiment of the invention. The input port 124, intended for receiving incoming gas flow (FLOW IN indicated by arrow 103), is in direct connection with the first part 121 of the airway tube 120, whereas the output port 125, intended for delivering outcoming gas flow (FLOW OUT indicated by arrow 104), is in direct connection with the third part (not shown) of the airway tube 120. Hence, the input port 124 is the direct entry for receiving gas flow 20, here specifically in the form of passing breathing gases (for example fresh gas or air, O2 + N2O), while the output port 125 is the direct exit for delivering the passing breathing gases 20 having been mixed with the anaesthetic agent droplets 30.

[0044] By means of example, here three transducers 132 can be distinguished in the embodiment of Figure 1 (a). These transducers 132 are mounted in the plate 131 which may comprise for instance a maximum of six transducers in total, implying e.g. that six holes are provided in the plate 131 wherein transducers can be placed (all or not including a general seating). The provision of six holes does not necessarily mean that the maximum of six transducers has to be present or activated. It is fairly possible that one or more transducers are not present or inactive. In case of a transducers being not present, the holes may be filled with a full disk such that the liquid anaesthetic agent cannot pass through. The transducers may vary for example in size, in number of pores, and in pore sizes. As to size, they can vary in diameter, but they could also vary in thickness. Amongst the total amount of transducers provided in the plate, one or more may be of the same type (e.g. having same size, number of pores or pore sizes) and one or more may be of a different type (e.g. having different size, number of pores or pore sizes).

[0045] It is noted that the apparatus and corresponding method for delivering anaesthetic agent to a breathing patient as described in accordance with the invention, could also be used for delivering other products or medication applied during anaesthesia and administered typically in an intravenous manner such as for example propofol. Not only would this result in a further clinical advantage and more comfort for the patient, it would also turn out beneficial for the environment, by directly supplying such other anaesthetic products or medication via the electronic vaporizer.

[0046] In accordance with an embodiment of the invention, as indicated in Figure 1 (a), the liquid reservoir 110 comprises a tank 115 wherein the liquid can be contained, and which may be filled with anaesthetic liquid 10 via the input 101. Further, the liquid reservoir 110 may comprise a liquid level indicator 111 such as for example a floater using the principle of material buoyancy to follow fluid / liquid levels by means of a passive measurement. In addition, an active measurement of the fluid / liquid level may be performed by means of a liquid level sensor 112, amongst which for example an optical level sensor, an ultrasonic level sensor, or a capacitive liquid level sensor could be used. Liquid level can be measured using either relative or absolute sensors. A relative sensor continuously measures the liquid level, providing a gradual reading. In contrast, an absolute sensor detects whether the liquid has reached a specific threshold. By using multiple absolute sensors, it's possible to determine the range or interval in which the liquid level currently resides. In or onto the airway tube 120, in particular in the area of the third part (not shown) (for transferring the passing breathing gases 20 having been mixed with the anaesthetic agent droplets 30) thereof, a flow sensor 126 may be provided for measuring the (mixed) gas flow (e.g. velocity of gas) in this third part of the airway tube 120. Alternatively, such flow sensor 126 may also be provided in the first part 121 of the airway tube 120, as for example depicted in Figure 1 (a). According to an embodiment (not shown here), the flow sensor can also be provided in the first part or second part of the airway tube. In other words, it is not absolutely necessary that the mixed gas needs to be measured, as it will be in the same path as the incoming unmixed gas. In normal operation of the anaesthetic apparatus, it is expected that the mixed gas flow, of passing breathing gases with the anaesthetic agent droplets, can be measured by the flow sensor in the third part of the airway tube. However, according to an embodiment, at some time it might be possible to temporarily inactivate (or remove) all transducers (e.g. remove for cleaning purposes), and hence then a gas flow just containing the passing breathing gases is transferring the third part of the airway tube.

[0047] According to an embodiment, the flow sensor 126 will measure if the (mixed) gas is arriving at a certain velocity, e.g. the gas arrives at lL / min or at 15L / min. In case a constant output of anaesthetic agent in the (mixed) gas such as e.g. of 10% is required, there is a need to nebulize 15x more with a flow of 15L / min than with a flow of lL / min. The (mixed) gas flow is thus used as a parameter to control the amount of nebulization (however only as open loop, not a closed loop control, because the gas concentration is not particularly measured). If a concentration of 5% more anaesthetic agent is to be achieved, a faster nebulization will be required if the (mixed) gas has a flow of lOL / min, than if it has only 2L / min (5x less).

[0048] It is particularly noted that the liquid reservoir 110 and the airway tube 120 are different and separated modules of the apparatus 100. Hence, there is a physical separation between the anaesthetic liquid 10 contained in the tank 115 and the gas flow 20, here specifically in the form of passing breathing gases (for example fresh gas or air, O2 + N2O) being conveyed and mixed with (sub)micron scale anaesthetic agent droplets 30 being evaporated and / or nebulized in (the second part 122 of) the airway tube 120. Due to this physical separation, the inventive working principle is not pressure sensitive (i.e. not depending on the pressure) nor temperature sensitive. This is particularly advantageous compared to standard state-of-the-art vaporizing systems that are particularly using desflurane, being put under pressure and provided with heating in order to enable the evaporation at room temperature. The evaporation at room temperature is desirable as is naturally the case when using sevoflurane or isoflurane as anaesthetic agent. Related also to the pressure sensitiveness, it is further noted that amongst certain locations i.e. geographical regions on earth, the atmospheric pressure may vary a lot, which may have a significant impact on traditional vaporizers being used. In addition, a further advantage of the anaesthetic apparatus configuration in accordance with embodiments of the invention, is that, because of the separated modules (in particular the liquid reservoir 110 and the airway tube 120 being separated), the tank 115 for containing the anaesthetic liquid 10 can be filled during operation of the apparatus 100, which is not the case in standard state-of-the-art vaporizing systems.

[0049] Further as illustrated in Figure 1 (a), a print board or PCB 113 is for example provided for incorporating electronics, and such PCB 113 may be wire connected - using wires 114 - with other components, such as e.g. the liquid level sensor 112, the flow sensor 126 and the transducers 132. According to an embodiment, the electronics are provided for controlling the connected components. According to an embodiment, the flow sensor 126 is connected (e.g. by a wire 114) with a (micro)processor (e.g. mounted on the PCB 113) to which the measuring of the (mixed) gas flow (as measured by the flow sensor) can be transferred, and subsequently may be interpreted by the (micro)processor. This measuring, transfer and interpretation thereof by the (micro)processor can be used for controlling (e.g. adjusting) the one or more transducers 132, and hence adapting the production, and evaporation and / or nebulization of anaesthetic agent droplets 30 depending on the (mixed) gas flow measuring. The control of the one or more transducers in this case is typically a dynamic control, could even be real-time. A possible adjustment (in control) could be for example, activating or inactivating a certain amount of transducers (e.g. for changing amount of anaesthetic agent output in general), or a particular type of transducers (e.g. for changing anaesthetic agent droplet size). By means of the dynamic control, the strength activation and / or the concentration of anaesthetic liquid being administered can be controlled. Moreover, the droplet size can be controlled to optimize intake at particular parts of a patient's body, such as e.g. the lungs, the lung periphery etc. By means of controlling the electronics, e.g. in voltage or current, and / or controlling parameters related to time, e.g. flow rate or velocity, the amount of evaporation and / or nebulization to be applied can be adapted. As a result, the output in general of an anaesthetic agent to be delivered to a patient breathing can be controlled.

[0050] Figure 2 illustrates another embodiment of an apparatus 200 for administering an anaesthetic agent for a patient breathing, in accordance with the invention. In Figure 2 (a), a back perspective view of the anaesthetic apparatus 200 is shown, again comprising a liquid reservoir 210 for containing an anaesthetic agent, an airway tube 220 for guiding / conveying the (mixed) gas flow, and an anaesthetic agent dosing unit 230 for delivering, i.e. evaporating and / or nebulizing anaesthetic agent droplets to the (fresh) gas flow passing by. The liquid reservoir 210 is provided with a cover 217 and fixing screws 218 for closure. Onto the airway tube 220, onto its outer back surface 228 in particular, the input port 224 intended for receiving incoming (fresh) gas flow, as well as the output port 225 intended for delivering outcoming (mixed) gas flow, are indicated. Mounting screws 219 are indicated at the bottom of the airway tube 220. In between the liquid reservoir 210 on one hand, and the airway tube 220 and / or the anaesthetic agent dosing unit 230 on the other hand, a channel plate or wire tray 240 having multiple channels 241 for guiding wires is present. The wires are not shown here, and are intended to electrically connect the transducers that are mounted in the anaesthetic agent dosing unit 230 with the electronics provided elsewhere. The electronics are for example provided onto a PCB in a separate closed (and possibly sealed) chamber in or in the vicinity of the liquid reservoir 210. By means of the connected electronics, the transducers can be controlled such that for example the amount of anaesthetic agent, the dosage or the way of administering the anaesthetics to be delivered to the (fresh) gas flow can be adjusted dynamically, possibly even in real-time.

[0051] In Figure 2 (b), a front perspective view of the anaesthetic apparatus 200 is shown, in accordance with an embodiment of the invention. Again, here, the liquid reservoir 210, the airway tube 220, and the anaesthetic agent dosing unit 230 can be distinguished. The channel plate or wire tray 240 is also shown, provided onto the bottom surface 216 of the liquid reservoir 210. The liquid reservoir 210 is now illustrated in open status, meaning it is not provided with a cover 217 and fixing screws 218 as in Figure 2 (a). The anaesthetic agent dosing unit 230 is provided onto the upper part 229 of the airway tube 220, and comprises here, by means of example a plate 231 onto which six transducers 232 are mounted. The configuration of the plate 231 as illustrated here, i.e. having cutouts 233 at two sides, may allow the plate 231 to be removable or extendable and hence being able to removing, adding, replacing or interchanging one or more of the transducers 232. Onto the upper part 229 of the airway tube 220, a mounting rod 221 is shown for assembling the lower modules i.e. the airway tube 220 and the anaesthetic agent dosing unit 230, with the upper modules i.e. the liquid reservoir 210 and the wire tray 240, of the apparatus. In this particular embodiment, only one mounting rod 221 is shown whereas in total two are being used for the assembly. It is noted that the other one is hidden in the drawing here.

[0052] Figure 3 illustrates further detail of the lower modules i.e. the airway tube and the anaesthetic agent dosing unit of the 3D-representation embodiment of Figure 2. In particular, in Figure 3 (a) a disassembled front perspective view is shown of the airway tube 320 and the anaesthetic agent dosing unit 330 of an anaesthetic apparatus in accordance with an embodiment of the invention. The airway tube 320 is again indicated with input port 324 and output port 325 for respectively receiving and delivering gas flow. Two mounting rods 321 are now depicted for assembling lower with upper modules of the apparatus. The anaesthetic agent dosing unit 330 comprises a plate 331 provided with holes 334 for mounting the transducers 332. As an example, six holes 334 with respective edges 34 are provided here for mounting a maximum of six transducers 332. According to an embodiment, the transducers 332 comprise an assembled structure, clearly depicted in Figure 3 (b), comprising a seating 335, and an ultrasonic mesh transducer comprising two discs 336, 337 on top of each other. A first disc 336 is made of metal, such as e.g. stainless steel or titanium, in any case being resistant to corrosion of the anaesthetic liquid used to be evaporated and / or nebulized. A second disc 337 is made of piezoelectric material such as e.g. ceramics. In the centre 36 of the metal disc 336, very small holes or apertures (typically of micrometre dimensions) are provided such that the anaesthetic liquid can be forced or "pushed" there through due to ultrasonic vibrations generated by the piezoelectric disc 337. In order to do so, the piezoelectric disc 337 is electrically connected, and will contract and expand because of an electric current. As a result, piezoelectric disc 337 will vibrate the metal disc 336 provided with centre mesh 36 to be driven and controlled. Figure 3 (b) is showing a disassembled perspective view of the transducer 332, rather to be interpreted as a transducer assembly. In addition to the seating 335 and the ultrasonic mesh transducer discs 336, 337, O-rings 338, 339 may be further provided for helping to seal joins between the ultrasonic mesh transducer and other connecting parts and prevent fluid leakage. Determining for the transducer assembly 332 an upper surface 39 and a bottom surface 35, during operation of the apparatus, the upper surface 39 will be in connection with the fluid or anaesthetic liquid from the liquid reservoir, whereas the bottom surface 35 will be in connection with the edge 34 of one of the holes 334 provided in the plate 331.

[0053] In Figure 4, further detail is illustrated of the upper modules i.e. the liquid reservoir and the wire tray of the 3D-representation embodiment of Figure 2. Particularly, Figure 4 (a) is showing a bird's eye disassembled front perspective view of the liquid reservoir 410 and the wire tray 440 of an anaesthetic apparatus in accordance with an embodiment of the invention. The wire tray 440, also referred to as channel plate, comprises multiple channels 441 for laying wires and a number of recesses 442 for allowing anaesthetic fluid to pass through towards the upper surface of corresponding transducers mounted in the plate of the anaesthetic agent dosing unit. In the vicinity of the channels 441 and recesses 442, connectors 444 may be provided for connecting the transducers with wires, and hence connecting them with the electronics provided elsewhere. The electronics are for example provided onto a PCB in a separate closed (and possibly sealed) chamber in or in the vicinity of the liquid reservoir 410. Further, as shown in both Figure 4 (a) and Figure 4 (b), O-rings 443 are presented for sealing purposes, and screws 446 and mounting recesses 445, 447 are drawn for assembly and fixation of the configuration. In Figure 4 (b), also a disassembled front perspective view is shown of the liquid reservoir 410 and the wire tray 440 of an anaesthetic apparatus in accordance with an embodiment of the invention, however now in worm's eye view. Hence, the bottom surfaces of the upper modules now become visible. As a result, the mounting recess 445 is shown here for fixing a screw 446. In addition, the bottom surface 416 of the liquid reservoir 410 is clearly depicted, also having a number of recesses 16 for enabling passage of the anaesthetic fluid towards the transducers.

[0054] Figure 5 illustrates an enlarged cross sectional view of an embodiment of part of an apparatus for administering an anaesthetic agent for a patient breathing, in accordance with an embodiment of the invention. In the particular, the area is shown of a transducer 532, provided in an anaesthetic agent dosing unit 530, where micro droplets 30 of the anaesthetic agent are formed. The anaesthetic agent in bulk form, as a liquid 10 is indicated, and assumed to be in a tank 515 as part of a liquid reservoir. As shown, the transducer 532 is mounted into a seating 535 being provided in the anaesthetic agent dosing unit 530. On top of the anaesthetic agent dosing unit 530, a wire tray 540 is fixed by means of screws 546. The wire tray 540 typically comprises a plurality of wires of which one wire 514 is shown here, being connected to the transducer 532 by means of a connector 544, such as for example a pogo pin as illustrated here. The connector 544 comprises two (resilient) connecting rods 44 at its both ends respectively. One of the connecting rods 44 is connecting with the wire 514, whereas the other connecting rod 44 is connecting with the transducer 532 and making contact with both the piezo disc 537 and the metal disc 536 of the transducer 532. Another type of connector is however not excluded to be used instead. For example it may also be a fixed connector that is soldered to the wire and to the transducer respectively. Further, in this Figure 5, the incoming gas flow (of fresh breathing gas to be mixed with anaesthetic agent) is indicated by arrow 503.

[0055] As shown by the illustrations for the embodiments above, as depicted in Figures 1 to 5, there is a particular aspect represented by the design and configuration of the apparatus for administering an anaesthetic agent for a patient breathing, in accordance with the invention. This particular aspect is related to the way of assembly or structure of the three main parts of the apparatus, being the liquid reservoir, the airway tube, and the anaesthetic agent dosing unit. From the illustrations it is clear that the airway tube is provided at the bottom of the apparatus, just below the anaesthetic agent dosing unit. The liquid reservoir is mounted on top of the anaesthetic agent dosing unit comprising the transducers with pores. Hence, the liquid from the liquid reservoir is always in contact with the anaesthetic agent dosing unit and with the transducers thereof, because of the assembly of having the liquid reservoir on top and due to gravity of the liquid. When the apparatus is in operation, this gravitation may also play a role in the formation and delivery of droplets, and therefore the assembly of having the liquid reservoir on top is deliberately chosen. Apart from the fact that the liquid is always in contact with the transducers (as long as there is liquid provided in the liquid reservoir), the liquid is always pushed against the upper surface of the transducers, because of the vertical assembly of the liquid reservoir on top of the anaesthetic agent dosing unit comprising the transducers. By means of this gravitational aspect, and the activation, in particular vibration of the transducers, the liquid may penetrate through the anaesthetic dosing unit, in particular through the pores of the transducers. Using the aspect of gravitation due to the orientation of the three main parts of the apparatus, and hence its structural feature, may lead to less force or energy needed from the activation (or vibration) for pushing the liquid through the pores and herewith form small droplets. Therefore, current design or configuration may result in an improved energy efficiency as compared to the art.

[0056] Figure 6 illustrates an embodiment in accordance with the invention, of a system 600 for an anaesthesia machine connected to a breathing circuit 620, for delivering fresh breathing gas (such as air, oxygen etc.) supplied from a supply tank 610, and anaesthetic agents (e.g. halothane, isoflurane, sevoflurane and desflurane) to a patient 624. In particular, the system 600 comprises an anaesthetic vaporizer 611 or apparatus for administering an anaesthetic agent for a patient breathing. In accordance with embodiments of the invention, the delivery of the anaesthetic agent is in the form of (sub)micron scale liquid droplets being evaporated and / or nebulized by means of an ultrasonic mesh transducer technique, and can be statically and dynamically controlled. Together with the fresh gas supply, the anaesthetic agent can be delivered to the breathing circuit 620. Due to the apparatus configuration, the invention provides in an optimal composition and mixture of fresh gas and evaporated and / or nebulized anaesthetic agent therewith. A possible design of a breathing circuit 620 is illustrated here, comprising a CO2 absorber 621 for eliminating carbon dioxide and a reservoir bag 622. Via the patient connection 623, fresh gas and anaesthetics can be delivered to the patient 624. It is noted that the anaesthetic vaporizer 611 is not necessarily located as indicated here in Figure 6. The anaesthetic agent can also be provided or infused elsewhere in the breathing cycle 620, and thus not necessarily between the CO2 absorber 621 and the patient

Claims

Claims1. An apparatus (100) for administering an anaesthetic agent for a patient breathing comprising:— a liquid reservoir (110) for an anaesthetic agent;— an airway tube (120); and— an anaesthetic agent dosing unit (130) in connection with said liquid reservoir (110) and connected to said airway tube (120), said anaesthetic agent dosing unit (130) comprises a plate (131) with one or more transducers (132), each comprising a plurality of pores, to produce and evaporate and / or nebulize anaesthetic agent droplets directly in said connected airway tube (120); wherein said airway tube (120) comprises a first part (121) for receiving passing breathing gases, a second part (122) for mixing said passing breathing gases with said anaesthetic agent droplets produced by said one or more transducers, and a third part for transferring said passing breathing gases having been mixed with said anaesthetic agent droplets.

2. The apparatus according to claim 1, wherein said one or more transducers have different pore sizes per transducer and / or amongst said transducers.

3. The apparatus according to claim 1 or 2, wherein each of said plurality of pores have a diameter of 0,1-500 pm, preferably 0,1-20 pm, more preferably 0,1-10 pm.

4. The apparatus according to claim 1 to 3, further comprising a liquid level indicator (111) and / or liquid level sensor (112).

5. The apparatus according to claim 1 to 4, further comprising a flow sensor (126) for measuring a gas flow in the airway tube (120).

6. The apparatus according to claim 5, wherein said flow sensor being connected with a processor to which said measuring is transferred, and subsequently interpreted by said processor, for controlling and / or monitoring said one or more transducers.

7. The apparatus according to claim 1 to 6, further comprising a print board (113) provided with electronics and electric wires (114) to be connected to one or more parts of the apparatus.

8. The apparatus according to claim 7 and taking into account claim 4 to 6, wherein said one more parts comprise said one or more transducers (132), the liquid level sensor (112) and / or the flow sensor (126).

9. The apparatus according to claim 7 or 8, further comprising a wire tray comprising multiple channels for guiding said electric wires and comprising recesses for fluid passage to said one or more transducers.

10. The apparatus according to claim 9, wherein said wire tray further comprises connectors for connecting said electric wires with said one or more transducers.

11. The apparatus according to claim 1 to 10, being an anaesthetic vaporizer, or else being part of an anaesthetic vaporizer, or which can be assembled with or either incorporated in an anaesthetic vaporizer.

12. A system for an anaesthesia machine, comprising an apparatus according to any of claim 1 to 11.

13. A method for administering an anaesthetic agent for a patient breathing comprising:— receiving passing breathing gases;— providing a liquid containing the anaesthetic agent;— producing anaesthetic agent droplets from said liquid by means of an anaesthetic agent dosing unit comprising one or more transducers provided on a plate;— delivering said produced anaesthetic agent droplets directly to said passing breathing gases;— evaporating and mixing said delivered anaesthetic agent droplets directly with said passing breathing gases; and— transferring the evaporated anaesthetic agent mixed with said passing breathing gases.

14. A method for controlling an anaesthetic vaporizer in an anaesthesia machine, comprising:— supplying power to one or more transducers provided on a plate of the anaesthetic vaporizer;— operating the one or more transducers configured to evaporate and / or nebulize liquid anaesthetic agent and deliver the nebulized anaesthetic agent directly to an airway tube of the anaesthetic vaporizer;— measuring a gas flow output by means of a flow sensor; and — controlling and possibly also monitoring said one or more transducers based on said measuring.

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