GB2611097A

GB2611097A - Gas delivery device

Info

Publication number: GB2611097A
Application number: GB2113853.2A
Authority: GB
Inventors: David Whalley Robert; Mark Avery Adam
Original assignee: VET TECH SOLUTIONS Ltd
Current assignee: VET TECH SOLUTIONS Ltd
Priority date: 2021-09-28
Filing date: 2021-09-28
Publication date: 2023-03-29
Anticipated expiration: 2041-09-28
Also published as: GB202113853D0; GB2611097B

Abstract

A gas delivery device 200 and method for delivering an active compound 211 to a target comprises a vaporizer 210 for vaporizing the active compound; a gas circuit 220 arranged to recirculate a carrier gas through the vaporizer for enriching said carrier gas in said active compound; a pump 230 arranged in the gas circuit for impelling said carrier gas around the gas circuit; a gas output 240 for delivering said active compound in said carrier gas to a target; and a gas output valve 241 arranged to selectively open and close the gas circuit to the gas output. The gas circuit may further comprise a plenum tank 221, wherein the gas output valve is connected to the plenum tank. The device may further comprise a gas delivery chamber 250 connected to the gas output via first gas chamber inlet 251 for receiving the enriched carrier gas, and may also comprise a first gas chamber outlet 252 for circuiting gas back into the gas circuit, and a second gas chamber outlet 258 for venting gas into the atmosphere outside the chamber.

Description

Gas Delivery Device

Field

The present invention relates to a gas delivery device and to a method of delivering an active compound in a carrier gas to a target. In particular, the present invention relates to an anaesthetic gas delivery device and method, for example for use on small animals.

Background

Small animals are typically anaesthetised using apparatus that includes a flow meter to regulate carrier gas flow, a medical/veterinary vaporizer and a non-rebreathing system such as a mask. A carrier gas, usually oxygen, is passed over the vaporizer at a maximum rate of 10 litres a minute.

The vaporizer vaporises an anaesthetic agent into the carrier gas which is then administered to the animal's nose via a non-rebreathing circuit through the mask. Common vaporizers can be adjusted to vaporize anaesthetic agents into a carrier gas at a concentration in the range of 0-8 vol%.

For small animals, a concentration of 4-5 vol% of anaesthetic agent in the carrier gas is required to initially induce anaesthesia and a concentration of 1-2 vol% of anaesthetic agent in the carrier gas is subsequently required for maintenance of an anaesthetised state. Using a conventional set up, these levels can be rapidly administered directly to an animal's nose via a mask.

In some instances, it is desirable to anaesthetise multiple animals simultaneously in a larger animal chamber or home cage. Most anaesthetic chambers used for mice typically have a volume of approximately 3-4 litres and are used with carrier gas flows of 2 l/min and a vaporizer set to produce a concentration of anaesthetic agent in the carrier gas of around 5 vol%. When used this way, it takes around 5-6 minutes for the atmosphere in the chamber to reach the vaporizer set concentration of 5 vol% and therefore effectively anaesthetise the animals.

Summary of the Invention

Due to the 8 vol% concentration of anaesthetic agent and 10 l/min flow rate limitations of a typical vaporizer, when a larger chamber sizes is used the rate of increase of the concentration of anaesthetic agent within the chamber is slower. This slow rise in the concentration of the anaesthetic vapour within the chamber causes stress to both the animals and the operators overseeing the procedure.

To avoid pressurisation of the animal chamber as the anaesthetic agent in the carrier gas is delivered to the chamber, a vent is required which vents a volume of gas from the chamber equal to that of the anaesthetic agent and carrier gas delivered. This is wasteful of both carrier gas and anaesthetic agent.

Therefore there is a need for an improved anaesthetic gas delivery device which can address these problems with known vaporizers and associated gas delivery apparatus.

It is one aim of the present invention, amongst others, to provide a gas delivery device and a method of delivering an active compound in a carrier gas to a target, that addresses at least one disadvantage of the prior art, whether identified here or elsewhere, or to provide an alternative to existing gas delivery devices and methods. For instance, it may be an aim of the present invention to provide a gas delivery device which can deliver a desired concentration of an active compound to a target faster than is possible with known gas delivery systems, in particular wherein the active compound is an anaesthetic agent and the desired concentration of active compound is sufficient to anaesthetise the target, such as a small animal.

According to aspects of the present invention, there is provided a gas delivery system and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and from the description which follows.

According to a first aspect of the present invention, there is provided a gas delivery device comprising a vaporizer for vaporizing an active compound; a gas circuit arranged to recirculate a carrier gas through the vaporizer for enriching said carrier gas in said active compound; a pump arranged in the gas circuit for impelling said carrier gas around the gas circuit; a gas output for delivering said active compound in said carrier gas to a target; and a gas output valve arranged to selectively open and close the gas circuit to the gas output.

Suitable vaporizers for use in the gas delivery device are known in the art. Such vaporizers are charged with a volatile active compound in liquid form and function by directing an incoming carrier gas stream over the active compound to cause evaporation of the active compound into the carrier gas. The carrier gas stream is then directed out of the vaporizer towards a target. The carrier gas flow rate, pressure and temperature of the vaporizer are adjustable to provide a desired concentration of active compound in the carrier, typically in the range of 0-8 voP/0 for an anaesthetic agent as the active compound.

The gas circuit is provided by suitable piping for accommodating and transferring a carrier gas and active compound. The gas circuit provides fluid communication between the vaporizer and the gas output valve suitable for the passage of gas around the circuit. The gas circuit is sealed when the gas output valve is closed to continuously circulate the carrier gas around the gas circuit. Suitably no air is admitted into the gas circuit in use.

Said carrier gas which the gas delivery device of this first aspect is suitable for use with is suitably air. Therefore in use the gas circuit is initially filled with air before operation of the device which enriches said carrier gas in said active compound.

The gas output for delivering said active compound in said carrier gas to a target suitably comprises piping suitable for accommodating and transferring said carrier gas enriched in said active compound from the gas circuit to said target, when the gas output valve is open. The gas output therefore directs gas flow from the gas circuit to the target.

The target can be any target which a user intends to provide a vaporized active compound to in a stream of carrier gas. In some embodiments the target is a subject, suitably a human or animal subject. Suitably the subject is an animal such as a small animal, for example a rodent.

In use, the gas delivery device functions by the pump continuously circulating (i.e. recirculating) said carrier gas, for example air, around the gas circuit and through the vaporizer which continuously enriches the carrier gas in the active compound being vaporized by the vaporizer. This phase of operation may be referred to as a recirculation phase or an enrichment phase. Once a desired concentration of active compound in the carrier gas has been achieved in the recirculation phase, the gas delivery device can be operated to open the gas output valve so that the carrier gas enriched in active compound is supplied to a target via the gas output. This phase of operation may be referred to as a vapor induction phase or a vapor delivery phase. The gas output is suitably a conduit for delivering the carrier gas enriched in active compound to a chamber containing a subject, such as a small animal.

The inventors have found that the gas delivery device of this first aspect can produce a carrier gas containing a higher concentration of active compound than is obtainable using known gas delivery devices comprising vaporizers. This higher concentration of active compound allows the user to supply the target with sufficient active compound for a purpose in a shorter time than known gas delivery devices.

This may be particularly advantageous when the gas delivery device is an anaesthetic gas delivery device, wherein the active compound is an anaesthetic agent and the gas output is arranged to supply a chamber containing a subject, such as a small animal. Such an anaesthetic gas delivery device of the first aspect can produce concentrations of anaesthetic agent in the carrier gas of around 20 vol% or greater which can then be delivered to the chamber to provide a sufficient concentration of anaesthetic agent in the atmosphere of the chamber to anaesthetise a subject (4-5 vol%) in a shorter time than would be possible using known anaesthetic gas delivery devices, for example in around two minutes or less.

This shortening of the time to reach an anaesthetic induction concentration in a chamber may advantageously reduce the usage of anaesthetic agent overall, reduce the stress of the subject animal caused by prolonged exposure to low concentrations of anaesthetic agent and consequently also reduce the stress of operators of the device who may be affected by any stress caused to the subject animals. Furthermore, the gas delivery system of this first aspect can advantageously operate using air as the carrier gas rather than a more expensive pressurised carrier gas such as oxygen. This is due to the gas delivery system preferably operating under ambient pressure or close to ambient pressure and utilising the pump in the gas circuit to impel the carrier gas (suitably air) around the gas circuit, rather than the pressure of a carrier gas source such as a pressurised oxygen tank.

Suitably the gas delivery device of this first aspect comprises a plenum tank arranged in the gas circuit for accommodating a volume of said carrier gas. To connect the plenum tank in fluid communication with the gas circuit, the plenum tank suitably comprises a plenum tank gas inlet connected to the gas circuit and a plenum tank gas outlet connected to the gas circuit. The plenum tank is suitable for retaining gas and has a volume which significantly increases the total volume of gas circuit. In use, the carrier gas flows through the plenum tank as it circulates around the gas circuit. The plenum tank may be constructed from any suitable gas impermeable material which is resistant to the carrier gas and active compound selected for use with the gas delivery device. For example, the plenum tank may be constructed from stainless steel. The plenum tank is considered to be part of the gas circuit for the following description of the invention.

The incorporation of the plenum tank into the gas delivery device significantly increases the volume of the gas circuit and therefore increases the volume of said carrier gas enriched in said active compound which can be produced in the gas circuit by the gas delivery device in the recirculation mode. This in turn means that the gas delivery device can supply an increased volume of carrier gas enriched in active compound to the target during the vapor induction phase than would otherwise be possible.

Suitably the plenum tank provides at least 80% of the volume of the gas circuit, suitably at least 90%.

Suitably the gas circuit comprises a plenum tank inlet valve for selectively opening and closing the plenum tank inlet to the gas circuit. Suitably the gas circuit comprises a plenum tank outlet valve for selectively opening and closing the plenum tank outlet to the gas circuit. Suitably the gas circuit comprises both the plenum tank inlet valve and the plenum tank outlet valve. The plenum tank inlet valve and the plenum tank outlet valve suitably allow the plenum tank to be isolated from the rest of the gas circuit in use, for example during a vapor induction phase, so that only the gas in plenum tank is supplied to said target through the gas output. Isolating the plenum tank from the gas circuit in this manner may also facilitate the change of the plenum tank for a plenum tank of a different size, according to the needs of the user for supplying a certain active compound to a certain target.

Suitably the plenum tank has a volume of at least 3 litres, suitably at least 5 litres. In some embodiments, the plenum tank may have a volume of at least 10 litres. The volume of the plenum tank may be proportional to the volume of a chamber in which the target is located. Suitably the plenum tank has a volume of at least 20% of the volume of the chamber, suitably at least 30% of the chamber. In some embodiments, the volume of the plenum tank is from 20 to 50% of the volume of the chamber.

Suitably the gas output is connected to the plenum tank and the gas output valve is arranged between the plenum tank and the gas output. With this arrangement, the carrier gas enriched in active compound supplied to said target in the vapor induction phase comes directly from the plenum tank, which may be isolated from the rest of the gas circuit by the plenum tank inlet valve and the plenum tank outlet valve, as discussed above.

Suitably a gas output pump or blower is arranged in the gas output. The gas output pump or blower is configured to impel gas out of the gas circuit and through the gas output to said target. Suitably the gas output pump or blower is arranged in-line in pipework of the gas output. Suitable pumps or blowers for use as the gas output pump or blower are known in the art.

Suitably the gas delivery device comprises a gas return arranged between said target and the gas circuit. The gas return is suitably pipework connecting said target to the gas circuit in fluid communication. Suitably the gas return comprises a valve for selectively opening and closing the gas return to the gas circuit, in order to isolate the gas circuit from the target during the recirculation phase. Therefore the gas delivery device suitably comprises a gas delivery circuit comprising the gas output, the gas output valve, at least a part of the gas circuit and the gas return. Suitably said target is arranged in the gas delivery circuit such that said carrier gas enriched in said active compound is delivered to said target and then flows through the gas return to the at least a part of the gas circuit. Suitably the gas delivery circuit can be isolated from the gas circuit and isolated from the ambient atmosphere surrounding the gas delivery device.

Suitably the gas delivery device comprises a chamber connected to the gas output for delivery of said active compound in said carrier gas into the chamber. Suitably the gas output is connected to the chamber through a first chamber gas inlet. Suitably the chamber is sealed or sealable, apart from an opening to the gas output. Suitably the chamber is for housing a subject for supplying said carrier gas enriched in active compound to. The chamber may be configured and sized to accommodate a subject, such as a small animal or a plurality of small animals. Such suitable sizes and configurations of chambers to accommodate such subjects are known in the art. In some embodiments the chamber may have a volume of at least 10 litres, suitably at least 15 litres. The larger the chamber, the greater the benefit of the gas delivery device of this first aspect may be in reducing the time to reach a desired concentration of active compound in the chamber, for example an anaesthetic induction concentration.

Suitably the gas delivery device comprises a first chamber gas outlet connecting the chamber and the gas circuit to allow gas to pass from the chamber to the gas circuit, suitably through a gas return as described above. Suitably the gas return comprises a valve, referred to herein as a first chamber gas outlet valve, in order to isolate the chamber and the gas delivery circuit from the gas circuit during the recirculation phase. Suitably the chamber is comprised within a gas delivery circuit as described above. Therefore the gas delivery circuit suitably comprises at least a part of the gas circuit, the gas output valve, the gas output, the first chamber gas inlet, the chamber, the first chamber gas outlet the first chamber gas outlet valve and the gas return. The gas delivery circuit is suitably configured to circulate carrier gas enriched in active compound continuously around these parts of the gas delivery device, between the chamber (which in use would comprise said target) and the at least a part of the gas circuit.

Suitably the at least a part of the gas circuit included in the gas delivery circuit comprises the plenum tank. Suitably the at least a part of the gas circuit included in the gas delivery circuit is the plenum tank. Therefore the gas delivery circuit suitably comprises the plenum tank, the gas output valve, the gas output, the first chamber gas inlet, the chamber, the first chamber gas outlet, the first chamber gas outlet valve and the gas return, and suitably the gas output pump or blower. This arrangement is suitably configured to circulate carrier gas enriched in active compound from the plenum tank to the chamber and back to the plenum tank, continuously. The gas delivery circuit may be particularly suitable for continuously circulating an anaesthetic gas (i.e. an anaesthetic agent in a carrier gas) through the chamber to anaesthetise a subject, such as small animal.

Suitably the chamber comprises an air inlet for allowing air into the chamber and an air inlet valve for selectively allowing or preventing said air into the chamber through the air inlet.

Suitably the chamber comprises a second chamber gas outlet for allowing gas to pass out of the chamber to the surrounding atmosphere and a second chamber gas outlet valve for selectively allowing or preventing said gas to pass out of the chamber through the second chamber gas outlet.

Suitably the gas delivery device comprises an exhaust connected in fluid communication to the second chamber gas outlet, for expelling gas from the gas delivery device into the surrounding atmosphere, for example.

Suitably the second chamber gas outlet is connected to a chamber gas outlet pump or blower for impelling gas from the chamber to outside of the gas delivery device, suitably through an exhaust of the gas delivery device.

The air inlet, air inlet valve, second chamber gas outlet, second chamber gas outlet valve and chamber gas outlet pump or blower suitably allow said carrier gas enriched in said active compound to be flushed out of the chamber by air to clear the chamber of active compound, for example after the purpose of supplying said active compound to said target has been completed. Such a flushing operation may be carried out when the gas output valve and the first chamber gas outlet valve are closed, therefore isolating the plenum tank and the gas circuit from the chamber so that these parts of the gas delivery device are not flushed by said air.

In some embodiments, the gas delivery device comprises: a vaporizer for vaporizing an active compound; a gas circuit arranged to recirculate a carrier gas through the vaporizer for enriching said carrier gas in said active compound a plenum tank arranged in the gas circuit for accommodating a volume of said carrier gas; a pump arranged in the gas circuit for impelling said carrier gas around the gas circuit; a chamber for housing a subject; a gas output for delivering said active compound in said carrier gas to the chamber, wherein the chamber is connected to the gas output for delivery of said active compound in said carrier gas into the chamber; a gas output valve arranged to selectively open and close the gas circuit to the gas output; a gas return connecting the chamber and the gas circuit to allow carrier gas to pass from the chamber back to the gas circuit; and a first chamber gas outlet valve arranged in the gas return to selectively open and close the gas circuit to the gas output.

In some embodiments, the gas delivery device is an anaesthetic gas delivery device. In such embodiments, the gas delivery device is suitably configured for anaesthetising a small animal or a plurality of small animals simultaneously, for example a small mammal such as a rodent or a plurality of small mammals / rodents.

In some embodiments the gas delivery device comprising a chamber comprises a second chamber gas inlet for connecting the chamber to a source of a second gas. The second chamber gas inlet is configured to allow a second gas to pass into the chamber. Said second gas may be a pressurized gas. Therefore the gas delivery device of such embodiments suitably comprises a second gas tank and suitably a gas flow regulator for said second gas for selectively allowing or preventing said second gas from flowing into the chamber. This arrangement is suitably configured to allow the chamber to be flushed with said second gas. Said second gas may be a gas capable of euthanising an animal subject, for example nitrogen or carbon dioxide. Therefore in such embodiments, the gas

B

delivery device may be an anaesthetic and euthanising gas delivery device for use with animals, suitably small animals.

In such embodiments, the gas delivery device suitably comprises: a vaporizer for vaporizing an active compound; a gas circuit arranged to recirculate a carrier gas through the vaporizer for enriching said carrier gas in said active compound a plenum tank arranged in the gas circuit for accommodating a volume of said carrier gas; a pump arranged in the gas circuit for impelling said carrier gas around the gas circuit; a chamber for housing an animal subject; a gas output for delivering said active compound in said carrier gas to the chamber, wherein the chamber is connected to the gas output for delivery of said active compound in said carrier gas into the chamber; a gas output valve arranged to selectively open and close the gas circuit to the gas output; a gas return connecting the chamber and the gas circuit to allow carrier gas to pass from the chamber back to the gas circuit; and a first chamber gas outlet valve arranged in the gas return to selectively open and close the gas circuit to the gas output; wherein the chamber comprises a second gas inlet for connecting the chamber to a source of a second gas and a gas outlet for said second gas, suitably wherein the second gas is a gas capable of euthanising said animal subject.

Suitably the gas delivery device comprises the source of said second gas.

According to a second aspect of the present invention, there is provided a method of delivering an active compound in a carrier gas to a target, the method comprising the steps of: a) vaporizing the active compound in a vaporizer into the carrier gas; b) recirculating the carrier gas through a closed gas circuit comprising the vaporizer to enrich the carrier gas in the active compound, until the concentration of the active compound in the carrier gas has reached a set value; and c) selectively opening the closed gas circuit to deliver the active compound in the carrier gas to the target.

Suitably the steps of the method of this second aspect are carried out in the order step a) simultaneously with b) followed by step c).

Suitably the method of this second aspect is carried out using a gas delivery device according to the first aspect and may have any of the suitable features and advantages discussed in relation to the first aspect.

Suitably steps a) and b) are carried out until a concentration of at least 10 vol% of active compound in the carrier gas is obtained, suitably a concentration of at least 15 vol%, suitably a concentration of at least 20 vol% Suitably step c) is carried out for a sufficient time to achieve a purpose, for example anaesthetic induction of a subject such as a small animal or a plurality of small animals.

Suitably the active compound is an anaesthetic agent and the target is a small animal or a plurality of small animals, suitably a small mammal such as rodent of a plurality of small mammals / rodents.

In some embodiments, the method comprises a step d) of closing the gas circuit and supplying a second gas to the target. In such embodiments, the active compound is suitably an anaesthetic agent and the target is suitably an animal or plurality of animals and step c) is suitably carried out for a sufficient time to induce anaesthesia in the animal or animals. In such embodiments, the second gas of step d) is a gas capable of euthanising the animal or animals, for example nitrogen or carbon dioxide and step d) is carried out for a sufficient time to euthanise the animal or animals.

Brief Description Of The Drawings

Figure 1 shows a schematic of a prior art anaesthetic gas delivery device 100.

Figure 2 shows a schematic of an anaesthetic gas delivery device 200 according to the first aspect of the present invention.

Figure 2A shows a schematic of the recirculation mode of operation of the gas delivery device 200.

Figure 2B shows a schematic of the anaesthetic induction mode of operation of the gas delivery device 200 Figure 2C shows a schematic of the scavenge mode of operation of the gas delivery device 200 Figure 3 shows a schematic of an anaesthetic gas delivery device 300 according to the first aspect of the present invention which is configured to additionally euthanise a subject.

Detailed Description Of The Example Embodiments

The known anaesthetic gas delivery device 100 shown in Figure 1 comprises a vaporizer 110 connected to a carrier gas supply 120 and a chamber 150 by gas pipes configured to flow gas from the carrier gas supply 120 through the vaporizer 110 and to the chamber 150. The carrier gas supply 120 consists of a pressurised carrier gas tank 121 comprising a pressurized carrier gas, for example nitrogen, connected to a gas supply pipe 120. A flow regulator 122 and a pressure regulator 123 are arranged in the gas supply pipe. The flow regulator can be operated to allow pressurized carrier gas to flow from the pressurised carrier gas tank 121 to the vaporizer 110. The flow regulator 122 may be an 02 flowmeter with a range of 0-12 Ipm. The pressure regulator 123 may be a single stage 010 bar regulator pre-set to a 4 bar threshold.

The vaporizer 110 comprises a liquid anaesthetic agent and is configured to direct incoming carrier gas flow over and in contact with liquid anaesthetic agent. The liquid anaesthetic agent evaporates into the carrier gas as it flows through the vaporizer 110. The vaporizer 110 is connected to the chamber 150 by gas output pipe 140. The vaporizer performance can be adjusted by a user to set the concentration of anaesthetic agent which is vaporized into the carrier gas flow, typically between 0 and S vol%.

The chamber 150 has an internal volume sufficient to house at least one small animal, for example an internal volume of 3 to 5 litres, and a chamber gas outlet 151. In use, the chamber 150 is initially full of ambient air and as carrier gas flows from the vaporizer 110 (comprising the vaporized anaesthetic agent) through the gas output 140 and passes into the chamber 150, the air contained within the chamber 150 is displaced and passes out of the chamber 150 through the chamber gas outlet 151. Therefore the concentration of anaesthetic agent in the chamber 150 gradually increases to reach a concentration which anaesthetises an animal in the chamber 150. This process can take 5-6 minutes using a typical carrier gas flow of 2 Um and a vaporizer setting of 5 vol% of anaesthetic agent.

The recirculating anaesthetic gas delivery device 200 of Figure 2 comprises vaporizer 210, gas circuit 220, pump 230, gas output 240, gas output valve 241 and chamber 250.

The gas output valve 241 may be provided by an SMC 2/2 Solenoid -1" bore. Valves 224, 225, 254, 257, 260 and 392 may also be provided by the SMC 2/2 Solenoids.

The vaporizer 210 is as described above for vaporizer 110 in gas delivery device 100 and contains a liquid anaesthetic agent. For example, the vaporizer 210 may be a Fluotec Vaporiser and the liquid anaesthetic agent may be Isoflurane. The vaporizer 210 comprises a vaporizer gas inlet 212 and a vaporizer gas outlet 213. The vaporizer 210 additionally comprises a heater 211 for maintaining a set temperature of the liquid anaesthetic agent to counteract the cooling effect of the evaporation of the liquid anaesthetic agent into the carrier gas. The heater 211 may be provided by a 10W silicone heat mat. The gas circuit 220 comprises pipework which connects the vaporizer gas outlet 213 to the vaporizer gas inlet 212 to form a closed loop around which gas can continuously flow, in effect recirculating the gas through the vaporizer. The pump 230 is arranged in the gas circuit 220 for impelling said carrier gas around the gas circuit and through the vaporizer. Pump 230 may be provided by a membrane pump model 1620VDP/2,2/F/DC.

The gas circuit also comprises plenum tank 221 which is a stainless steel tank having a volume of approximately 5 litres. The plenum tank 221 is connected to the gas circuit 220 through plenum tank inlet 222 and plenum tank outlet 223, which are openings in the tank connected to the pipework of gas circuit 220, so as to form part of the gas circuit 220. The plenum tank 221 is present to increase the capacity of the gas circuit 220 and to provide a storage volume for carrier gas comprising the anaesthetic agent. The gas circuit 220 comprises plenum tank inlet valve 224 and plenum tank outlet valve 225 which can be selectively opened and closed to either open the plenum tank 221 to the gas circuit 220 or to isolate the plenum tank 221 from the gas circuit 220. The plenum tank 221 also comprises a pressure relief outlet 228 connected to a pressure relief valve 229 which is set to release gas from the plenum tank 221, and therefore the gas circuit 220, when the pressure inside the plenum tank 221 reaches a threshold value. The pressure relief valve 229 may be provided by a Norgren pressure relief valve.

The gas output 240 is provided by pipework connecting the gas circuit 220 to the chamber 250 through the plenum tank 221. The plenum tank 221 comprises a second plenum tank outlet 226 which is an opening in the plenum tank 221 connected to the pipework of the gas output 240. The gas output 240 comprises a gas output valve 241 for selectively opening and closing the plenum tank 221 to the gas output 240. The gas output 240 also comprises a gas output blower 242 for impelling gas from the plenum tank 221 to the chamber 250 through the gas output 240. Gas output blower 242 may be provided by an Emb Papst RG100 centrifugal fan.

The chamber 250 has an internal volume sufficient to house at least one small animal, for example an internal volume of 3 to 5 litres. In use, a small animal or multiple small animals are placed in the chamber 250 in order to receive the anaesthetic gas from the gas output 240. The chamber is constructed from clear Perspex and has a sealable lid for allowing the placement of small animals in the chamber 250. The chamber 250 comprises a first chamber gas inlet 251 which is connected to the gas output 240 to receive anaesthetic gas from the plenum tank 221. The chamber 250 comprises a first chamber gas outlet 252 which is connected through pipework of a first chamber gas outlet line 253 (or gas return) to a second plenum tank inlet 227 in order to allow anaesthetic gas to pass from the chamber 250 back to the plenum tank 221. A first chamber gas outlet valve 254 is arranged in the first chamber gas outlet line 253 to selectively allow or prevent gas flow from the chamber 250 to the plenum tank 221 through the chamber gas outlet line 253.

The chamber 250 also comprises air inlet 255 connected to pipework of an air supply line 256 which is open to the atmosphere surrounding the anaesthetic gas delivery device 200. The air supply line 256 comprises an air inlet valve 257 for selectively opening and closing the chamber 250 to the air supply line 256.

The chamber 250 also comprises a second chamber gas outlet 258 connected to pipework of a second chamber gas outlet line 259 which provides an exhaust 270 to outside of the anaesthetic gas delivery device 200. The second chamber gas outlet line 259 comprises a second chamber gas outlet valve 260 for selectively opening and closing the chamber 250 to the exhaust 270. The second chamber gas outlet line 259 also comprises a chamber gas outlet blower 261 for impelling gas from the chamber 250 to the exhaust 270, through the second chamber gas outlet line 259. Chamber gas outlet blower 261 may be provided by an Emb Papst RG100 centrifugal fan.

The vaporizer, valves and pumps of the anaesthetic delivery device 200 are connected to a control module (not shown) for controlling the operation of the device and specifically the settings of the vaporizer, the status of the valves and the operation of the pumps. The control module comprises appropriate hardware and software for carrying out these operations. The operation of the anaesthetic gas delivery device 200 may be carried out as follows.

The anaesthetic delivery device 200 has three modes of operation: 1) a recirculation mode, 2) an anaesthetic induction mode and 3) a scavenge mode. These three modes of operation are carried out in sequence in order to carry out a process of anaesthetising a subject, such as one or more small animals.

In the recirculation mode, the gas output valve 241 and the first chamber gas outlet valve 254 are closed and the plenum tank inlet valve 222 and the plenum tank outlet valve 223 are open.

Additionally, air inlet valve 257 and second chamber gas outlet valve 260 are closed.

This provides a closed loop gas recirculation pathway through the vaporizer 210, the gas circuit 220, the pump 230 and the plenum tank 221, as shown by the arrows of gas flow in Figure 2A. The vaporizer is charged with anaesthetic agent and the pump 230 is activated so that the carrier gas contained in the gas circuit 220 and plenum tank 221 (i.e. air already present in the device) is continuously circulated through the vaporizer to enrich the carrier gas in the anaesthetic agent. The cooling effect the evaporation of the anaesthetic agent has on the vaporizer is counteracted by operation of the heater 211 which is controlled to provide a consistent set temperature of the vaporizer and the anaesthetic agent. The vaporization of anaesthetic agent into the carrier gas also causes an increase in pressure in the gas circuit 220. Pressure relief valve 229 on plenum tank 221 is configured to vent carrier gas to the exhaust 270 in order to relieve this increase in pressure and maintain a constant pressure in the gas circuit 220 in the recirculation mode. The time that the anaesthetic gas delivery device 200 operates in the recirculation mode as described above may be referred to as a "recirculation phase". Usually, a volume of carrier gas in the plenum tank 221 / gas circuit 220 approximately equal to the volume of the anaesthetic agent vaporized into the carrier gas needs to be vented through pressure relief valve 229 to maintain constant pressure in the plenum tank 221 / gas circuit 220. For example, to reach a concentration of anaesthetic agent in the carrier gas of 20 vol% in the recirculation mode then approximately 20 vol°/0 of the carrier gas will need to be vented from the gas circuit 220.

Once a sufficient concentration of anaesthetic agent in the carrier gas has been reached in the recirculation mode, for example 20 vol%, the anaesthetic gas delivery device can move to the anaesthetic induction mode of operation. Three to six cycles of carrier gas through the vaporizer may be required to obtain this concentration of anaesthetic agent in the carrier gas, in the recirculation mode To operate in the anaesthetic induction mode, the gas output valve 241 and the first chamber gas outlet valve 254 are opened and air inlet valve 257 and second chamber gas outlet valve 260 remain closed. The gas output blower 242 is activated and therefore the carrier gas enriched in anaesthetic agent is circulated continuously from the plenum tank 221 to the chamber 250 through the gas output 240 and the first chamber gas outlet line 253, as shown by the arrows of gas flow in Figure 2B. This may be referred to as a gas delivery circuit which comprises the plenum tank 221, the second plenum tank outlet 226, the gas output 240, the gas output valve 241, gas output blower 242, the first chamber gas inlet 251, the chamber 250, the first chamber gas outlet 252, the first chamber gas outlet valve 254, the first chamber gas outlet line 253 (gas return) and second plenum tank inlet 227. This mode provides anaesthetic gas to the chamber 250 in sufficient quantities to anaesthetise a subject in the chamber 250, such as one or more small animals. Therefore prior to the anaesthetic induction mode, the subject is placed in the chamber 250. The recirculation mode may have already been carried out by the time the subject is placed in the chamber 250. The period which the anaesthetic gas delivery device 200 operates in the anaesthetic induction mode may be referred to as an "anaesthetic induction phase".

In the anaesthetic induction mode, the plenum tank inlet valve 222 and the plenum tank outlet valve 223 may remain open and the pump 230 and vaporizer 210 remain activated to continue to provide additional anaesthetic agent to the carrier gas. Alternatively, plenum tank inlet valve 222 and the plenum tank outlet valve 223 may be closed so that only the carrier gas enriched in anaesthetic agent present in the plenum tank 221 is circulated through the chamber 250. In that case, the vaporizer 210 and the pump 230 may be deactivated.

This combination of recirculation mode and anaesthetic induction mode of the gas delivery device can provide a concentration of anaesthetic gas sufficient to anaesthetise a subject in a shorter time from placing the subject in the chamber 250 than known anaesthetic gas delivery devices. The capacity of the plenum tank 221, the capacity of the chamber 250, the settings of the vaporizer 210, the duration of operation in the recirculation mode and the flow rate of carrier gas produced by pump 230 and/or gas output pump 242 may be adjusted to achieve a desired anaesthetic effect in a certain time to a certain subject. For example, a larger subject may require a higher capacity chamber 250 and therefore a higher capacity plenum tank 221 and a higher flow rate in order anaesthetise the subject in a desired time period.

Once the subject has been anaesthetised, the gas delivery device 200 can be operated in the scavenge mode in order to remove the carrier gas enriched with anaesthetic agent from the chamber 250. To operate in the scavenge mode, the air inlet valve 257 and the second chamber gas outlet valve 260 are opened, the chamber gas outlet blower 261 activated. This causes air to be drawn into the chamber 250 through the air supply line 256 to displace the carrier gas enriched in anaesthetic agent to the exhaust 270 through the second chamber gas outlet line 259, as shown by the arrows of gas flow in Figure 2C. Preferably the gas output valve 241 and the first chamber gas outlet valve 254 are closed in order to isolate the plenum tank 221 and the vaporizer 210 from the flow of air. The carrier gas enriched in anaesthetic agent exiting the anaesthetic gas delivery device 200 through the exhaust 270 may be released to the atmosphere or passed through a filtration system before being released to the atmosphere. The period which the anaesthetic gas delivery device 200 operates in the scavenge mode may be referred to as a "scavenge phase".

The anaesthetic gas delivery device of the present invention may be adapted to also euthanise an animal subject. Anaesthetic gas delivery device 300 shown in Figure 3 is adapted to carry out euthanasia of one or more animal subjects after anaesthetic induction. Anaesthetic gas delivery device 300 is as described above for the anaesthetic gas delivery device 200 of Figure 2 with the addition of a euthanasia gas supply 380 and a third chamber gas outlet 390. The euthanasia gas supply 380 consists of a pressurised euthanasia gas tank 381 comprising a pressurized euthanasia gas, for example nitrogen or carbon dioxide, connected to a euthanasia gas supply pipe 382. A flow regulator 383 and a pressure regulator 384 are arranged in the euthanasia gas supply line 382. The flow regulator 383 may be provided by a pre-set CO2 flow control valve. The pressure regulator 384 may be provided by a single stage CO2 Regulator having a range of 0-10 bar -pre-set to 4 bar.

The flow regulator can be operated to allow pressurized euthanasia gas to flow from the pressurised euthanasia gas tank 381 to the chamber 250 through a third chamber gas inlet 262. The gas present in the chamber 250 is displaced by the euthanasia gas and moved out of the chamber through the third chamber gas outlet 390, along third chamber gas outlet line 391 and through third chamber gas outlet valve 391, as shown by the arrows of gas flow in Figure 3.

The anaesthetic gas delivery device 300 can be operated in a euthanasia mode by appropriate control of the euthanasia gas supply 380 and the valves described above. The euthanasia mode is carried out after the anaesthetic induction mode described above, therefore whilst an animal subject is anaesthetised. To operate in the euthanasia mode, the gas output valve 241, plenum tank inlet valve 224, plenum tank outlet valve 225, first chamber gas outlet valve 254, air inlet valve 257, second chamber gas outlet valve 260, gas output valve 241, are all closed and pumps 230 and blowers 242 and 261 are deactivated. The flow regulator 383 is then operated to allow a flow of pressurized euthanasia gas, such as carbon dioxide or nitrogen, into the chamber 250 to displace the gas present in the chamber 250 with the euthanasia gas for a sufficient time to cull the animal subject. This may be referred to as a euthanasia phase. The reduction in the time of the anaesthetic induction phase discussed above can contribute to a faster and more humane animal euthanasia method.

Afterwards, the scavenge mode is suitably carried out as described above in relation to Figure 2 to clear the chamber 250 of euthanasia gas.

In summary, the present invention provides a gas delivery device for delivering an active compound to a target. The gas delivery device comprises a vaporizer for vaporizing the active compound; a gas circuit arranged to recirculate a carrier gas through the vaporizer for enriching said carrier gas in said active compound; a pump arranged in the gas circuit for impelling said carrier gas around the gas circuit; a gas output for delivering said active compound in said carrier gas to a target; and a gas output valve arranged to selectively open and close the gas circuit to the gas output. The gas delivery device enriches the carrier gas in the active compound by circulating the carrier gas through a vaporizer multiple times in a closed gas circuit and then delivering the carrier gas enriched in an active compound to a target. This advantageously allows a higher concentration of active compound to be achieved than is possible with known gas delivery devices such as the device 100 shown in Figure 1. This higher concentration allows an increased rate of delivery of the active compound to the target which may be particularly advantageous in the delivery of anaesthetic gas to a subject such as a small animal or multiple small animals. A method of delivering an active compound in a carrier gas to a target is also provided.

Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

Throughout this specification, the term "comprising" or "comprises" means including the component(s) specified but not to the exclusion of the presence of other components. The term "consisting essentially of' or "consists essentially of' means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention. Typically, when referring to compositions, a composition consisting essentially of a set of components will comprise less than 5% by weight, typically less than 3% by weight, more typically less than 1% by weight of non-specified components.

The term "consisting of" or "consists of" means including the components specified but excluding addition of other components.

Whenever appropriate, depending upon the context, the use of the term "comprises" or "comprising" may also be taken to encompass or include the meaning "consists essentially or or "consisting essentially of', and may also be taken to include the meaning "consists of" or "consisting of".

The optional features set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional features for each aspect or exemplary embodiment of the invention as set out herein are also to be read as applicable to any other aspect or exemplary embodiments of the invention, where appropriate. In other words, the skilled person reading this specification should consider the optional features for each exemplary embodiment of the invention as interchangeable and combinable between different exemplary embodiments.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

Claims 1. A gas delivery device comprising: a vaporizer for vaporizing an active compound; a gas circuit arranged to recirculate a carrier gas through the vaporizer for enriching said carrier gas in said active compound; a pump arranged in the gas circuit for impelling said carrier gas around the gas circuit; a gas output for delivering said active compound in said carrier gas to a target; and a gas output valve arranged to selectively open and close the gas circuit to the gas output.
2. The gas delivery device according to claim 1, comprising a plenum tank arranged in the gas circuit for accommodating a volume of said carrier gas, the plenum tank having a plenum tank gas inlet connected to the gas circuit and a plenum tank gas outlet connected to the gas circuit.
3. The gas delivery device according to claim 2, wherein the gas circuit comprises a plenum tank inlet valve for selectively opening and closing the plenum tank inlet to the gas circuit, and a plenum tank outlet valve for selectively opening and closing the plenum tank outlet to the gas circuit.
4. The gas delivery device according to claim 2 or claim 3, wherein the plenum tank has a volume of at least 3 litres.
5. The gas delivery device according to any one of claims 2 to 4, wherein the gas output is connected to the plenum tank and the gas output valve is arranged between the plenum tank and the gas output.
6. The gas delivery device according to any one of the preceding claims, wherein a gas output pump is arranged in the gas output.
7. The gas delivery device according to any one of the preceding claims, comprising a chamber connected to the gas output for delivery of said active compound in said carrier gas into the chamber.
8. The gas delivery device according to claim 7, comprising a first chamber gas output connecting the chamber and the gas circuit to allow gas to pass from the chamber to the gas circuit.
9. The gas delivery device according to claim 7 or claim 8, wherein the chamber comprises an air inlet for allowing air into the chamber and an air inlet valve for selectively allowing or preventing said air into the chamber through the air inlet.
10. The gas delivery device according to any one of claims 7 to 9, wherein the chamber comprises a second chamber gas outlet for allowing gas to pass out of the chamber to the surrounding atmosphere and a second chamber gas outlet valve for selectively allowing or preventing said gas to pass out of the chamber through the second chamber gas outlet.
11. The gas delivery device according to claim 10, wherein the second chamber gas outlet is connected to a chamber gas outlet pump.
12. The gas delivery device according to any preceding claim, wherein the device is an anaesthetic gas delivery device for a small mammal.
13. The gas delivery device according to claim 12, wherein the chamber comprises a second gas inlet for connecting the chamber to a source of a second gas
14. A method of delivering an active compound in a carrier gas to a target, the method comprising the steps of: a) vaporizing the active compound in a vaporizer into the carrier gas; b) recirculating the carrier gas through a closed gas circuit comprising the vaporizer to enrich the carrier gas in the active compound, until the concentration of the active compound in the carrier gas has reached a set value; and c) selectively opening the closed gas circuit to deliver the active compound in the carrier gas to the target.
15. The method of claim 14 wherein the active compound is an anaesthetic agent and the target is a small mammal.