Patent Application
20220273903
The present disclosure relates to humidifiers for providing a flow of humidified gas to a patient.
Humidifiers (when used for medical purposes (such as respiratory humidifiers or surgical humidifiers for example)) provide a flow of humidified gas to a patient. The humidification provided by the humidifier may in itself be used for providing treatment. Alternatively, the respiratory humidifier may be a supplementary add-on that humidifies a flow of gas produced by another medical device (e.g. positive airway pressure therapy, high flow therapy, or the like) used to provide respiratory treatment to the patient.
One type of humidifier is the heated humidifier, which humidifies a flow of gas passed over a heated volume of water, as shown in
It is an object of the present disclosure to provide an apparatus and/or method for humidifying a flow of gas to a patient.
In one aspect, the present disclosure includes a humidifier, comprising: a gas flow path, a heater in the gas flow path, the heater comprising: a heater element, and a heat conductor in thermal contact with the heating element, wherein the heat conductor is foraminous.
The foraminous heat conductor may have voids in a solid structure.
This foraminous heat conductor may be foam.
The foam may be open cell foam.
The foam may be formed from metal or ceramic.
The foraminous heat conductor may comprise metal foam or ceramic foam.
The foraminous heat conductor may be for ameliorating the Leidenfrost effect.
The heat conductor may be for increasing the heat transfer rate.
The heater element may comprise PTC material.
The heater may be located within a conduit.
The humidifier may have an overflow drain.
The humidifier may further comprise a fluid delivery apparatus.
The fluid delivery apparatus may comprise a fluid reservoir.
The fluid delivery apparatus may be directly coupled to the heat conductor.
The fluid delivery apparatus may be adapted to drip fluid onto the heat conductor.
The heater may be in a humidifier tub.
The humidifier may be configured to operate at an operating temperature above about 20° C.
The humidifier may be configured to operate in a temperature range between about 60° C. and about 200° C., preferably between about 120° C. and about 150° C.
The heater element may comprise PTC material, and the foraminous heat conductor may comprise one or more of:
The humidifier may be configured to operate in a temperature range from about 100° C. to about 300° C.
The humidifier may comprise a PTC heater and/or PTC heater element configured to operate in a temperature range from about 20° C. to about 300° C.
The PTC heater and/or PTC heater element may be configured to operate in a first and/or second configuration:
The humidifier may comprise a non-PTC heater and/or non-PTC heater element configured to operate in a temperature range from about 20° C. to about 500° C.
The non-PTC heater and/or non-PTC heater element may be configured to operate in a first and/or second configuration:
If the operating temperature of the heater element (or heater more generally) is at a lower temperature range (such as from about 20° C. to about 100° C. for example), then a greater amount of the foraminous material in the heat conductor may be preferred in order to achieve the desired heat transfer rate. Using lower temperatures might be preferable from an energy and safety perspective. On the other hand, if the operating temperature range of the heater element (or heater more generally) is at a higher temperature range (for example, from about 100° C. to about 300° C. for PTC heater elements in thermal contact with a heat conductor, or from about 100° C. to about 500° C. for non-PTC heater elements), then less foraminous material may be required to achieve the desired heater transfer rate. Therefore, if a more compact humidifier is desired, then a higher operating temperature may be preferable.
The humidifier may further comprise a water sensor coupled to the heater.
The heater element may be a coil.
The heat conductor may be wrapped cylindrically around the heater element.
The humidifier may be configured to warm up in less than about 1 minute.
The humidifier may be configured to warm up in less than about 30 seconds.
The heater element may be temperature controlled via feedback loop.
In another aspect, the present disclosure includes a humidifier, comprising: a gas flow path, a heater in the gas flow path, the heater comprising: a heater element, and a heat conductor in thermal contact with the heating element, wherein the heater element comprises a PTC material.
The PTC material may be ceramic.
The PTC material may be located within an encapsulation structure.
The encapsulation structure may comprise, electrodes, electrically insulating tape, and an aluminium housing.
The heat conductor may be foraminous.
The foraminous heat conductor may have voids in a solid structure
The foraminous heat conductor may be foam.
The foam may be open cell foam.
The foam may be formed from metal or ceramic.
The heater element may self-regulate the upper limit of its temperature.
The heater may be located within a conduit.
The humidifier may have an overflow drain.
The humidifier may further comprise a fluid delivery apparatus.
The fluid delivery apparatus may comprise a fluid reservoir.
The fluid delivery apparatus may be directly coupled to the heat conductor.
The fluid delivery apparatus may drip fluid onto the heat conductor.
The heater may be in a humidifier tub.
The humidifier may be configured to operate at an operating temperature above about 20° C.
The humidifier may be configured to operate in a temperature range between about 60° C. and about 200° C., preferably between about 120° C. and about 150° C.
The heat conductor may comprise one or more of:
The humidifier may be configured to operate in a temperature range from about 100° C. to about 300° C.
The humidifier may comprise a PTC heater and/or PTC heater element configured to operate in a temperature range from about 20° C. to about 300° C.
The PTC heater and/or PTC heater element may be configured to operate in a first and/or second configuration:
The humidifier may comprise a non-PTC heater and/or non-PTC heater element configured to operate in a temperature range from about 20° C. to about 500° C.
The non-PTC heater and/or non-PTC heater element may be configured to operate in a first and/or second configuration:
If the operating temperature of the heater element (or heater more generally) is at a lower temperature range (such as from about 20° C. to about 100° C. for example), then it a greater amount of the foraminous material in the heat conductor may be preferred in order to achieve the desired heat transfer rate. Using lower temperatures might be preferable from an energy and safety perspective. On the other hand, if the operating temperature range of the heater element (or heater more generally) is at a higher temperature range (for example, from about 100° C. to about 300° C. for PTC heater elements in thermal contact with a heat conductor, or from about 100° C. to about 500° C. for non-PTC heater elements), then less foraminous material may be required to achieve the desired heater transfer rate. Therefore, if a more compact humidifier is desired, then a higher operating temperature may be preferable.
The humidifier may be configured to warm up in less than about 1 minute.
The humidifier may be configured to warm up in less than about 30 seconds.
In another aspect, the present disclosure includes a humidifier, comprising:
a gas flow path, a heater in the gas flow path, wherein the heater comprises a PTC material and a foraminous material.
The foraminous material may have voids in a solid structure.
The foraminous material may be foam.
The foam may be open cell foam.
The foam may be formed from metal or ceramic.
The PTC material may be ceramic.
The foraminous material may be metal foam or ceramic foam.
The heater may be located within a conduit.
The humidifier may have an overflow drain.
The humidifier may further comprise a fluid delivery apparatus.
The fluid delivery apparatus may comprise a fluid reservoir.
The fluid delivery apparatus may be directly coupled to the heat conductor.
The fluid delivery apparatus may drip fluid onto the heat conductor.
The heater may be in a humidifier tub.
The humidifier may be configured to operate at an operating temperature above about 20° C.
The humidifier may be configured to operate in a temperature range between about 60° C. and about 200° C., preferably between about 120° C. and about 150° C.
The foraminous material may be one or more of:
The humidifier may be configured to operate in a temperature range from about 100° C. to about 300° C.
The humidifier may comprise a PTC heater and/or PTC heater element configured to operate in a temperature range from about 20° C. to about 300° C.
The PTC heater and/or PTC heater element may be configured to operate in a first and/or second configuration:
The humidifier may comprise a non-PTC heater and/or non-PTC heater element configured to operate in a temperature range from about 20° C. to about 500° C.
The non-PTC heater and/or non-PTC heater element may be configured to operate in a first and/or second configuration:
If the operating temperature of the heater element (or heater more generally) is at a lower temperature range (such as from about 20° C. to about 100° C. for example), then a greater amount of the foraminous material in the heat conductor may be preferred in order to achieve the desired heat transfer rate. Using lower temperatures might be preferable from an energy and safety perspective. On the other hand, if the operating temperature range of the heater element (or heater more generally) is at a higher temperature range (for example, from about 100° C. to about 300° C. for PTC heater elements in thermal contact with a heat conductor, or from about 100° C. to about 500° C. for non-PTC heater elements), then less foraminous material may be required to achieve the desired heater transfer rate. Therefore, if a more compact humidifier is desired, then a higher operating temperature may be preferable.
The heater may comprise a heater element, and a heat conductor.
The heater element may comprise the PTC material.
The heater element may self-regulate the upper limit of its temperature.
The heat conductor may comprise the foraminous material.
The foraminous material may have voids in a solid structure.
The foraminous material may be foam.
The foam may be open cell foam.
The foam may be formed from metal or ceramic.
The heat conductor may be for ameliorating the Leidenfrost effect.
The heat conductor may be for increasing the heat transfer rate.
The humidifier may be configured to warm up in less than about 1 minute.
The humidifier may be configured to warm up in less than about 30 seconds.
Described herein is a humidifier for humidifying a flow of gas, comprising: a gas flow path, and a foraminous heater in the gas flow path for heating fluid to humidify gas flowing through the gas flow path.
The foraminous heater may have voids in a solid structure
The foraminous heater may be foam.
The foam may be open cell foam.
The foam may be formed from metal or ceramic.
The humidifier may comprise a fluid delivery apparatus for delivering fluid to the foraminous heater.
The fluid delivery apparatus may comprise fluid reservoir for holding a fluid.
The foraminous heater may comprise a heater element and a foraminous heat conductor.
The heater element and the foraminous heat conductor may be disposed within the tub.
The heater element may comprise a positive temperature coefficient (PTC) material.
The heater element may self-regulate the upper limit of its temperature.
The foraminous heat conductor may have voids in a solid structure.
The foraminous heat conductor may be formed from foam.
The foam may be open cell foam.
The foam may be formed from metal or ceramic.
The foraminous heat conductor may be a metal foam.
The humidifier may be:
In another aspect, the present disclosure includes a tub for a humidifier, comprising: a body for humidification, a first heat conductor and a second heat conductor arranged to form a humidification region and/or gas flow path in the body between the first heat conductor and the second heat conductor, and wherein the second heat conductor is foraminous to allow gas to pass to and from the humidification region and/or gas flow path.
The second heat conductor may have voids in a solid structure.
The second heat conductor may be foam.
The foam may be open cell foam.
The foam may be formed from metal or ceramic.
The tub may be adapted to receive an injection of water.
The tub may be adapted to receive the injection of water from a fluid delivery apparatus.
The tub may be adapted to be installed in a humidifier with a heater element to heat the first and/or second heat conductor.
The heating element may comprise a positive temperature coefficient (PTC) material.
The humidifier may be:
In another aspect, the present disclosure includes a humidifier for humidifying a gas, comprising: a body for humidification, a first heat conductor and a second heat conductor arranged to form a humidification region and/or gas flow path in the body between the first heat conductor and the second heat conductor, and a heating element for heating the first and/or second heat conductor, wherein the second heat conductor is foraminous to allow gas to pass to and from the humidification region.
The second heat conductor may have voids in a solid structure.
The second heat conductor may be foam.
The foam may be open cell foam.
The foam may be formed from metal or ceramic.
The humidifier may further comprise a fluid delivery apparatus for injecting fluid onto the first and/or second heat conductor.
The first and/or second heat conductor may be adapted to substantially vaporise fluid injected by the fluid delivery apparatus when fluid contacts the first and/or second heat conductor.
The humidifier may be:
The second heat conductor may be adapted to vaporise aerosolised fluid when aerosolised fluid contacts the second heat conductor.
The humidifier may further comprise a tub.
The first and second heat conductors may be disposed within the tub.
The first and/or second heat conductor may be foraminous.
The foraminous first and/or second heat conductor may have voids in a solid structure.
The foraminous first and/or second heat conductor may be foam.
The foam may be open cell foam.
The foam may be formed from metal or ceramic.
The first and/or second heat conductor may be a metal foam.
The first heat conductor may be thermally connectable to the heating element.
The heating element may comprise a positive temperature coefficient (PTC) material.
The heating element may self-regulate the upper limit of its temperature.
The humidifier may be:
Described herein is a medical gases delivery system with a humidifier according to any one or more of the statements or embodiments described herein.
The medical gases delivery system may further comprise a patient interface.
The patient interface may be one or more of:
Also described herein is a medical gases delivery system with a humidifier coupled to or for coupling to a gas source, wherein the gas source is one or more of:
Also described herein is a medical gases delivery system with a humidifier coupled to or for coupling to a flow source.
The flow source may provide one or more of:
The flow source may comprise a flow generator, insufflator or other gas source.
The medical gases delivery system may further comprise or be used with a gas source, wherein the gas source is one or more of: a ventilator, a flow generator, a wall source of gas, a gas bottle, or a blender, and is coupled to or can be coupled to the flow source and/or humidifier.
Also described herein is a medical gases delivery system with a flow source and humidifier that are integrated to form an integrated flow source.
The humidifier may be a modular component that couples to the flow source to provide the integrated flow source, optionally removably.
The humidifier and the flow source may be formed in a single housing to form an integrated flow source.
Also described herein is a flow source with a humidifier according to any of the previous statements, wherein the humidifier comprises: a gas flow path, and a heater in the gas flow path.
The heater may comprise: a heater element, and a heat conductor in thermal contact with the heating element, wherein the heat conductor is foraminous.
The heater may comprise: a heater element, and a heat conductor in thermal contact with the heating element, wherein the heater element comprises a PTC material.
The heater may comprise a PTC material and a foraminous material.
The foraminous material may have voids in a solid structure.
The foraminous material may be foam.
The foam may have open cell foam.
The foam may be formed from metal or ceramic.
Also described herein is a method of humidifying a flow of gases using a humidifier comprising a heater, wherein the method comprises the steps of: heating the heater, feeding a flow of gases into the humidifier, and feeding fluid to the heater such that fluid vaporises upon contact with the heater.
The method may further comprise the step of pumping fluid from a fluid reservoir to the heater.
The step of feeding fluid to the heater may comprise dripping fluid onto the heater.
The humidifier may comprise a controller configured to perform the method steps.
The heater may comprise a heat conductor, and fluid is dripped onto the heat conductor.
The heat conductor may be foraminous.
The foraminous material may have voids in a solid structure.
The foraminous material may be foam.
The foam may be open cell foam.
The foam may be formed from metal or ceramic.
The humidifier may operate as part of a medical gases delivery system according to any previous statement.
The method may further comprise the step of feeding water onto a heater of a humidifier comprises using: a fluid reservoir, a pump, and a feed-line, wherein the method comprises the steps of: operating the pump to pump fluid from a fluid reservoir through a feed-line, and feeding fluid to the heater.
Fluid fed to the heater may be provided at an adjustable flow rate determined based on desired humidity and/or flow of gas through the humidifier.
The step of feeding fluid to the heater may comprise dripping fluid onto the heater.
The humidifier may comprise a controller configured to perform the method steps.
One or more of the fluid reservoir, pump and feed-line may operate as part of a fluid delivery apparatus.
The humidifier may operate as part of a medical gases delivery system according to any previous statement.
Also described herein is a method of heating a heater for a humidifier according to any of the previous statements, the heater comprising a heater element, and a heat conductor, wherein the method comprises the steps of operating the heater element, and conducting heat to the heat conductor.
The heater element may comprise PTC material.
The heat conductor may be foraminous.
The foraminous material may have voids in a solid structure.
The foraminous material may be foam.
The foam may be open cell foam.
The foam may be formed from metal or ceramic.
The heater element may be operable by a controller, such that the controller is configured to regulate operating temperature of the heater element.
The humidifier may operate as part of a medical gases delivery system according to any previous statement.
In this specification, the terms “foraminous” and “porous” are intended to have the same meaning and these terms are interchangeable. The terms “foraminous” and “porous” refer to a structure with void spaces (which may be referred to as “pores”). The void spaces within a foras thminous/porous material may be randomly distributed or uniformly distributed. A foraminous/porous object refers to an object comprising a foraminous/porous material.
The terms “foam”, “open cell foam”, “closed cell foam”, “metal foam”, and “ceramic foam” are used throughout this specification. These terms are well understood in the art.
In this specification the term “flow source” refers to an apparatus that generates a flow of gas, e.g. by rotation of an impeller or similar via a motor or similar. By way of non-limiting examples, the flow source could be or comprise one or more of: a flow generator (as used in respiratory systems), a flow controller (such as an insufflator (used in surgical humidification systems) for example), other flow source, or a gas source (which might be the same as or different to and/or combined with or separate to a gas source (as described herein)).
In this specification, “high flow” means, without limitation, any gas flow with a flow rate that is higher than usual/normal, such as higher than the normal inspiration flow rate of a healthy patient. It can be provided by a non-sealing respiratory system with substantial leak happening at the entrance of the patient's airways due to non-sealing patient interface prongs. It is also provided with humidification to improve patient comfort, compliance and safety. Alternatively or additionally, it can be higher than some other threshold flow rate that is relevant to the context—for example, where providing a gas flow to a patient at a flow rate to meet inspiratory demand, that flow rate might be deemed “high flow” as it is higher than a nominal flow rate that might have otherwise been provided. “High flow” is therefore context dependent, and what constitutes “high flow” depends on many factors such as the health state of the patient, type of procedure/therapy/support being provided, the nature of the patient (big, small, adult child) and the like. Those skilled in the art know from context what constitutes “high flow”. It is a magnitude of flow rate that is over and above a flow rate that might otherwise be provided.
But, without limitation, some indicative values of high flow can be as follows.
In “high flow” the gas delivered will be chosen depending on for example the intended use of a therapy. Gases delivered may comprise a percentage of oxygen. In some configurations, the percentage of oxygen in the gases delivered may be about 15% to about 100%, 20% to about 100%, or about 30% to about 100%, or about 40% to about 100%, or about 50% to about 100%, or about 60% to about 100%, or about 70% to about 100%, or about 80% to about 100%, or about 90% to about 100%, or about 100%, or 100%.
Flow rates for “High flow” for premature/infants/paediatrics (with body mass in the range of about 1 to about 30 kg) can be different. The therapeutic flow can be set to 0.4-8 L/min/kg with a minimum of about 0.5 L/min and a maximum of about 25 L/min. For patients under 2 kg maximum flow is set to 8 L/min.
The term “comprising” as used in this specification and claims means “consisting at least in part of”. When interpreting each statement in this specification and claims that includes the term “comprising”, features other than that or those prefaced by the term may also be present. Related terms such as “comprise” and “comprises” are to be interpreted in the same manner.
It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7).
This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.
Embodiments of a medical gases delivery system 11 and the humidifier 10 will first be discussed at a general level with reference to
The humidifier 10 has a heater 40 (located in the gas flow path 41) and a fluid injector 42 (a term that is interchangeable with the terms “fluid feeder” or “fluid delivery apparatus”). In use, the fluid feeder 42 feeds fluid to the heater 40, and the heater 40 (including body and/or surfaces) is heated to vaporise the fluid provided by the fluid feeder 42. The fluid may be provided at any suitable rate or form (droplets, steady stream, injected from within the heater etc.) from any suitable location (above the heater 40, from within the heater, etc.). When the fluid either contacts and/or is close enough to the heater 40, the heater vaporises the fluid. The vaporised fluid mixes with the incoming flow of gas to humidify the gas for delivery to the patient 18. It is preferable that liquid water is used as the fluid, and for the rest of the specification, it is assumed that the fluid feeder 42 is for feeding small quantities of liquid water onto the heater 40, although a skilled person would realise that other fluids may be suitable, for instance a medicament.
The heater 40 may comprise a heater element 44, and one or more heat conductors 46 (which can also be termed “conductive heater”). The heater element 44 is a heat source, in which thermal energy is converted from another energy type. For example, the heater element 44 is configured to convert electrical energy into thermal energy to generate a heat source. The heater element 44 is configured to achieve a rapid start up shortly after the humidifier 10 is switched on. The heater element 44 may comprise a positive temperature coefficient (PTC) material (can be termed “PTC heater element”, and termed “PTC heater” more generally), such as ceramic for example, although this is not essential in some embodiments (i.e. these embodiments have non-PTC heater and/or non-PTC heater element). The properties of a PTC material will be discussed later. The heat conductor 46 is thermally connected to the heater element 44, and therefore conducts heat away from the heater element 44. The heater element 44 heats up the surface of the heat conductor 46 to a high enough temperature to rapidly vaporise a controlled quantity of water. The heat conductor 46 may comprise a foraminous/porous material (i.e. foraminous heat conductor) capable of conducting thermal energy, such as a metal foam for example. It is appreciated that the heater 40 may also be described as a heater that comprises a PTC material, and a foraminous/porous material. The foraminous/porous material can be any material that can be fabricated to be foraminous/porous (i.e. have a foraminous/porous structure) via a manufacturing method/process. In some embodiments, the foraminous/porous material is a metal or ceramic made (via a manufacturing method/process) into a foam structure. That is, the foam is formed from metal or ceramic. The foam structure can optionally be formed from voids in a solid structure. The foam structure can optionally be open cell foam. It is desirable that the (foraminous/porous) material selected for the heat conductor 46 does not oxidise well, or if it does, it oxidises to a stable and tenacious oxide, “sealing” the underlying (foraminous/porous) material from further oxidation. This is to address longer term usage and concerns about metal salts and the effect of those on the metal. Water constituents may affect the longevity of the heat conductor material. It is acceptable having small quantities of salt deposits in the water, as long as they do not deposit in sufficient quantities to block the pores in the (foraminous/porous) material. It is also desirable when selecting a (foraminous/porous) material for the heat conductor that the pore size of the material is sufficient to enable the foraminous/porous material to get wet.
In some embodiments, such as those shown in
It is envisioned that the humidifier 10 may be a) a standalone “box” unit, which can be used on its own or coupled to a flow source (such as a blower), b) incorporated as part of an integrated “box” unit comprising a humidifier and flow source, or c) incorporated as part of any other component of the medical gases delivery system 11 (for example, the humidifier 10 may be incorporated as part of a removable connection 26, in the patient conduit 21, or the like).
The humidifiers 10 as described above may be removable or portable. They may be battery powered, mains powered, or both. The humidifier 10, or any component of the humidifier 10 may be battery powered 350, 450 (AC, DC, or both).
Embodiments of the humidifier 10 described above, which has a heater 40 comprising a heater element 44 and at least one heat conductor 46, may provide one or more of these advantages:
Combinations of the advantages described above can result in a “fast acting” humidifier 110 that can be capable of providing a “quick response”—for example, in one or more of the following ways:
Combinations of the advantages described above might also facilitate a construction which results in a small/portable humidifier.
Referring to
A skilled person will appreciate that any of the embodiments of humidifier 10 can be used in any situation where humidification is desired, including specific embodiments of humidifier 10 which will be described later.
Discussion now turns to specific embodiments of the humidifier 10.
The foraminous heater 120 comprises a heater element 122, and a foraminous heat conductor 124. The foraminous heat conductor 124 encapsulates the heater element 122. This is done by wrapping the foraminous heat conductor over the outer surface of the heater element 122, thus creating thermal contact between the heater element 122 and the foraminous heat conductor 124. The heater element 122 and foraminous heat conductor 124 are supported by a thermal insulator 125 that is located at the base of the tub 118.
The fluid feeder 121 is used to drip water onto the surface of the foraminous heat conductor 124 in this embodiment. The fluid feeder 121 comprises at least the feed-line 130, but may also additionally comprise a water pump 126 and/or water reservoir 128. The water pump 126 draws water up from the water reservoir 128 along feed-line 130. The water pump 126 then pumps water out along the feed-line 130, through the fluid feeder 121. As a result, fluid is dripped onto the foraminous heat conductor 124. The water reservoir 128 is used for storing a body of water to be used for humidifying the flow of gas. The water reservoir 128 may be sealed off with the use of a sealant 132. The tub 118 may have a tub overflow drain 134, and a mixing cavity overflow drain 135, such that any excess water not vaporised by the foraminous heat conductor 124, or excess water formed by condensation, is drained from the tub 118, and is returned back to the water reservoir 128 for later use.
The humidifier 110 may also have a controller 129 for controlling the operation of the humidifier 110. The controller 129 can refer to one or more controllers configured to operate any functions described in this embodiment herein.
Discussion now turns to the features described in this embodiment in more detail.
2.1 Heater Element
The heater element 122 provides a heat source for the foraminous heat conductor 124 to vaporise water for humidification. Preferably the heater element 122 acts as a heat source by converting electrical energy into thermal energy.
In the embodiment shown in
The heater element 122 is preferably a heating element comprising positive temperature coefficient (PTC) material 136 (a term interchangeable with the term “PTC heater element”). PTC materials are produced from ceramics or polymers that are doped. Preferably, the heater element 122 is the embodiment as illustrated in
Selection of a PTC material as the material for inclusion in the heater element 136 assists with temperature control of the heater element 136. A PTC material is defined as a material that can self-regulate its temperature. This happens because a temperature increase in the PTC material (when current is passed through the PTC material for heating) causes an increase in electrical resistance, preventing thermal runaway. PTC material used in the heater element 136 should preferably exhibit a highly non-linear/exponential thermal response, so that above a composition-dependent threshold temperature, the resistance of the PTC material in the heater element 136 increases rapidly/exponentially, causing the PTC material in the heater element 136 to act as its own temperature controller. The graph shown in
Alternatively, a heater element that does not comprise PTC material (i.e. a non-PTC heater element with a linear thermal response) may be used instead of a PTC heater element. If a non-PTC heater element is used, a method of temperature control (e.g. using the controller) can be implemented to limit temperature and ensure safe operating temperatures on the heater element 136. In a non-PTC heater element, the heater element may have an electrical resistance that does not increase exponentially with an increase in operating temperature. Consequently, a feedback loop is used for temperature control of the heater element, and for maintaining safe operating temperature limits. This also means sensors are used to monitor the temperature of the non-PTC heater element, whether sensing directly or indirectly. It should be apparent to a skilled person that they can implement a feedback loop (including sensor/s) when implementing any (other) humidifier embodiment with a non-PTC heater element.
The controller 129 (i.e. a voltage controller) can be configured to control the voltage and/or current supplied to the heater element 122 to convert electrical energy into thermal energy. If the heater element 122 comprises a PTC heater element 136, it is preferable that the controller is configured to control the voltage applied across the PTC heater element 136. The amount of electrical energy converted to the thermal energy is determined by the difference between the operating temperature of the PTC heater and the actual temperature of the PTC heater. This is dependent on the water feed rate and gas flow rate.
The heater element 136 can operate in a temperature range from about 20° C. to about 500° C. More preferably the heater element 136 can operate in a temperature range of about 60° C. to 200° C. Even more preferably the heater element 136 can operate in a temperature range of about 120° C. to 150° C. If the heater element 136 is a PTC heater element, the heater element 136 can operate in a temperature range from about 20° C. to about 300° C., and if the heater element 136 is a non-PTC heater element, the heater element 136 can operate in a temperature range from about 20° C. to about 500° C. If the operating temperature of the heater element (or heater more generally) is at a lower temperature range (such as from about 20° C. to about 100° C. for example), then it has been found that a greater amount of the foraminous material in the heat conductor is preferred to achieve the desired heat transfer rate. Using lower temperatures might be preferable from an energy and safety perspective. On the other hand, if the operating temperature range of the heater element (or heater more generally) is at a higher temperature range (for example, from about 100° C. to about 300° C. for PTC heater elements in thermal contact with a heat conductor, or from about 100° C. to about 500° C. for non-PTC heater elements), then less foraminous material is required to achieve the desired heat transfer rate. Therefore, if a more compact humidifier is desired, then a higher operating temperature is preferable. A skilled person would recognise that the heater element 136 may operate at a different temperature, or different temperature range not specified above.
2.2 Foraminous Heat Conductor
The foraminous heat conductor 124 is used to vaporise water (from the fluid feeder 121) for humidification.
The foraminous heat conductor 124 preferably comprises an open cell metal foam. The metal foam 124 helps minimise the Leidenfrost effect, which increases the speed of vaporisation and assists in preventing aerosolization of water. The metal foam 124 helps to break water surface tension, which improves the extent that the dripped water spreads over the metal foam 124, or improves the extent that the dripped water “wets” the metal foam. This, combined with the large surface area that the porosity of the metal foam 124 provides relative to the water droplet provides an improved rate of heat transfer to the water, resulting in faster vaporisation of the water. The metal foam 124 has an additional effect of providing a distributed heating surface above the heating element 122, improving the vaporisation of any aerosols to the extent that aerosolization may occur. Preferably, the material selected in the metal foam 124 is a foam with a thickness of about 1.5 mm. However more generally, the metal foam should be thick enough to carry enough water such that bubbles in the water can be contained in the foam. This is because when water contacts a hot surface and boils, bubbles form. In order to reduce the likelihood of aerosols being formed under all operating conditions, the foam should be thick enough that these bubbles are wholly contained within the foam. A thickness in the range of 1-6 mm could be suitable, but other thickness ranges could be suitable as long as thickness of the foraminous heat conductor 124 is thick enough to carry the water/contain bubbles, yet thin enough to reduce thermal mass and cost.
The foraminous heat conductor 124 can operate in a temperature range from about 20° C. to about 500° C. More preferably the foraminous heat conductor 124 and/or heater 122 can operate in a temperature range of about 60° C. to 200° C. Even more preferably the foraminous heat conductor 124 and/or heater 122 can operate in a temperature range of about 120° C. to 150° C. If the foraminous heat conductor 124 is in thermal contact with a PTC heater element, the foraminous heat conductor 124 can operate in a temperature range from about 20° C. to about 300° C., and if the foraminous heat conductor 124 is in thermal contact with a non-PTC heater element, the foraminous heat conductor 124 can operate in a temperature range from about 20° C. to about 500° C. If the operating temperature of the heat conductor (or heater more generally) is at a lower temperature range (such as from about 20° C. to about 100° C. for example), then it has been found that a greater amount of the foraminous material in the heat conductor is preferred in order to achieve the desired heat transfer rate. Using lower temperatures might be preferable from an energy and safety perspective. On the other hand, if the operating temperature range of the heat conductor (or heater more generally) is at a higher temperature range (for example, from about 100° C. to about 300° C. for PTC heater elements in thermal contact with a heat conductor, or from about 100° C. to about 500° C. for non-PTC heater elements), then less foraminous material is required to achieve the desired heat transfer rate. Therefore, if a more compact humidifier is desired, then a higher operating temperature is preferable. A skilled person would recognise that the foraminous heat conductor 124 and/or heater 122 may operate at a different temperature, or different temperature range not specified above.
2.3 Fluid Feeder
The fluid feeder 121 refers to the means for supplying water to the foraminous heater 120 for humidification.
Preferably the fluid feeder 121 comprises a pump 126 that supplies water to the foraminous heater 120 through the fluid feeder 121. The pump 126 can be considered separate to the fluid feeder 121, or alternatively the pump 126 can be considered a component that the fluid feeder 121 comprises, as context allows. The pump 126 is controllable by a controller 129 that can accurately control the amount of water delivered to the foraminous heater 120. The controller 129 can receive the ambient humidity and current gas flow as an input to determine the water flow that the pump 126 should actuate at to achieve the desired humidity. The controller 129 can be configured to determine and control the appropriate amount of water that the pump 126 delivers to the foraminous heater 120 based on the flow rate of gas being delivered to the patient 18. The pump 126 injects water through an aperture 146 of the fluid feeder 121. The water drips onto the foraminous heat conductor 124, by falling under gravity. Alternatively, the tip of the fluid feeder 121 can be closer to, or in contact with the foraminous heat conductor 124, and water can be fed directly onto the foraminous heat conductor 124. The fluid feeder 121 is configured such that if the desired humidity is known, and if the current flow of gas is known, the fluid feeder (preferably by using the controller 129 to control the pump 126) can adjust the flow of water rapidly such that the desired humidity is achieved within seconds of inputting the desired humidity into the controller 129.
2.4 Overflow Drains
If the water reservoir 128 is located below the tub 118, a tub overflow drain 134 can be provided at the base of the tub 118. If there is a fault with the rate that water is fed by the fluid feeder 121 onto the foraminous heater 120, the tub overflow drain 134 can drain excess water into the water reservoir 128. The provision of a tub overflow drain 134 may be used to manage any vaporise water condensed on the walls of the mixing chamber 112 or tub 118, when conditions result in the relative humidity in the mixing cavity to exceed 100% (e.g. the relative humidity within the mixing chamber 112, (including in the tub 118) exceeds 100%). Over time, this condensation will agglomerate into droplets which will flow down the sides of the chamber, and ultimately down the drain when there is a large enough volume of condensed water. This is one way to lower the risk of liquid water travelling to the patient.
Similarly, if the water reservoir 128 is located below the mixing cavity 112, a mixing cavity overflow drain 135 can be provided at the base of the mixing cavity 112. The provision of a mixing cavity overflow drain 135 may be used to manage any vaporise water condensed on the walls of the mixing chamber 112 or tub 118, when conditions result in the relative humidity in the mixing cavity to exceed 100% (e.g. the relative humidity within the mixing chamber 112, (including in the tub 118) exceeds 100%). Over time, this condensation will agglomerate into droplets which will flow down the sides of the chamber, and ultimately down the drain when there is a large enough volume of condensed water. This is another way to lower the risk of liquid water travelling to the patient.
One difference is that the humidifier 210 comprises a tub 218 which inside contains the foraminous heat conductor 224, but not the heater element 222. The heater element 222 is instead placed underneath the base of the tub 218. The heater element 222 may be a separate component, may be fixed to the base of the tub 218, or may be fixed to the base of the mixing chamber 212 (but thermally insulated therefrom). The foraminous heater 220 (shown nominally in dotted lines) is formed when the heater element 222 and the foraminous heat conductor 224 are placed such that they are in thermal contact with each other. Preferably, this means positioning the tub 218 in the appropriate location (which could be a thermally isolated location from the mixing chamber) within the mixing chamber 212.
Another difference is that both the heater element 222 and the foraminous heat conductor are oriented horizontally, as opposed to vertically in the first humidifier embodiment 110.
Another difference is that the humidifier 210 comprises a fluid feeder 221 that feeds (as opposed to dripping) water into the bottom of the tub 218 (preferably by injection of water), and therefore feeds water into the bottom of the foraminous heat conductor 224. The pump 226 supplies water to the base of the tub 218. In operation, the pump 226 supplies water at a low flow rate. Feeding water from underneath the foraminous heat conductor 224 provides sufficient local pressure to wet the foam 224, overcoming variability in foam-water contact angle due to temperature, water mineral deposits, and organic compounds adsorbed from the air, and any other variables. Further, supplying water to the base of the foam 224 in this manner may help to further reduce any spatters and aerosol that may be generated if water is dropped onto the foam 224.
Another difference is that a lip 248 may be provided on top of the tub overflow drain 234 so that a layer of water formed along the bottom of the tub 218 can still “wet” the foraminous heat conductor, while allowing excess water to drain back into the reservoir.
This humidifier 310 is an in-conduit embodiment that allows for use inside the conduit. The humidifier 310 may be independently positioned anywhere within a conduit, including positioning the humidifier 310 proximal to the patient 18. The components described in this embodiment allow for a humidifier 310 that is smaller than the earlier described humidifiers 110, 210. The in-line humidifier 310 may be easier to manufacture.
The humidifier 310 has a mixing chamber 312 that is shaped as a conduit portion, or be placed in a conduit-shaped housing. The conduit portion 312 houses a foraminous heater 320, in which the foraminous heater 320 houses a heater element 322 and a foraminous heat conductor 324. The foraminous heater element 320 is a spiral that forms a coil, and the foraminous heat conductor 324 is an outer cylindrical body of ceramic or metallic foam 324 that wraps around the heater element 322. Gas flows in from the inlet portion 314 of the conduit 312, through the heater element 322 and around the metal foam 324. Gas then flows to the outlet portion 316 of the conduit 312. As part of a fluid feeder 321, a pump 126 pumps water from a water reservoir and can feed water directly (rather than dripping, to avoid any water spatter and droplets forming) onto the foam 324 wrapped around the heater element 322.
The heater element 322 may be battery powered 350 (AC, DC, or both). The heater element 322 may comprise of PTC material, but alternatively, the heater element 322 may not comprise of PTC material. Discussion will first turn to a variant where the heater element 322 comprises a PTC material.
The heater element 322 can comprise PTC material, including a PTC ceramic material. As explained earlier, the PTC material in the heater element 322 allows the operating temperature of the heater element 322 to be self-regulated. The heater element 322 does not require a temperature feedback loop controller in this instance. However, a skilled person would also recognise that other control mechanisms (of which controller 329 can be a component of for example) may optionally be implemented in addition to the inherent temperature and power control provided by the PTC material of the PTC heater element, although this is not essential. For example, there may optionally be feedback loops that monitor and/or control electrical resistance or humidity if the appropriate sensor/s and circuitry is provided.
Discussion now turns to another variant of the heater element 322 in which the heater element does not comprise PTC material (i.e. a non-PTC heater element). In a non-PTC heater element, the heater element 322 will have an electrical resistance that does not increase exponentially with an increase in operating temperature. Consequently, a feedback loop is required for temperature control of the heater element 322, and for maintaining safe operating temperature limits. This also means sensors are used to monitor the temperature of the non-PTC heater element, whether sensing directly or indirectly. As an example, a feedback loop for ensuring safe operation of the heater element 322 could come in the form of controlling the rate that water is supplied to the foam 324. The electrical potential across the heater element 322 can be sensed and measured by a voltage sensor 327, which in this example is an uninsulated wire that wraps around the foraminous heater 320 like a voltage sensing ring for example. If an insufficient amount of water is pumped to the foam 324, the heater element 322 (that the foam 324 is thermally connected to) will be excessively hot, causing an increase in electrical potential across the foam 324, and will be sensed by the voltage sensor 327. A relatively high voltage reading from the voltage sensor 327 causes the controller 329 to control the pump 326 to pump a greater flow of water to the foam 324. The additional flow of water delivered to the foam 324 helps in cooling the temperature of the heater element 322. Another example of a feedback loop could be to control the relative humidity output as a result of a direct measurement of humidity output. Another example of a feedback loop could be to control the gas flow rate. Another example of a feedback loop could be to control the power provided to the heater element 322, based on the proportional relationship between the power provided and the temperature of the heater element 322. A skilled person would recognise that there are other ways of implementing a feedback loop to regulate the operating temperature of the heater element 322. A skilled person would also recognise that feedback loops (including sensor/s) as discussed are to be taken into account when implementing any (other) humidifier embodiment with a non-PTC heater element. Although the feedback loops as described are used as part of a non-PTC heater element, a skilled person would appreciate that the feedback loops as described may optionally be used with a PTC heater element, but not essential as the PTC material of the PTC heater element provides inherent temperature and power control.
The humidifier 410 can be configured in the same way as what has been described for humidifier 310. However, one difference between humidifier 310 and humidifier 410 is the difference in the fluid feeder 421, which has no pump. Instead the supply of water is inherently controlled using one of: a pressurised cartridge of water, differential capillary action, or by using differential osmotic potential to draw water out from the water reservoir 428 to the foraminous heat conductor 424 (which may be a metal foam).
Discussion below now turns to alternative embodiments that the inventors have envisioned. The embodiments that will be described below can exist as an embodiment separate to the embodiments already discussed, or they can be seen as additional modifications to the embodiments already discussed. The alternative embodiments below are discussed by way of example only, however a skilled person would understand that other embodiments may also exist by making the appropriate modifications commonly known in the art.
6.1 Heater Element
The heater element can be mounted vertically (as shown in
There can be more than one heating element, either in parallel tubs, or there can be multiple heater elements in the same tub. The heater elements can be connected to the same, continuous contact heater. Alternatively, the heater elements can all operate independently of each other.
If the heater element is a PTC heater element, temperature of the PTC heating element can be varied, for example, from about 20° C. to about 300° C. The PTC heating element can be a ceramic, or another type of PTC material, such as a polymer. The power supply to the PTC heating element can be low voltage, e.g. from about 6V to about 48V DC, or mains voltage, e.g. from about 100V AC to about 230V AC.
Components of the heater element can be molded into the base of the tub. Alternatively, the tub can be overmolded onto the heater element and/or overmolded onto the thermal insulator (if present). Alternatively, the heater can be permanently or removably connected to the tub, using a snap-fit, friction fit or interference fit, or the like, to connect the components. The heater element can be connected to the tub via the thermal insulator.
6.2 Foraminous Heat Conductor
The foraminous heat conductor can be a nickel, copper or stainless steel metal foam, an alloy of any of those metals, or be any other relatively inert metal. Alternatively, it could be a non-metallic high temperature open cell foam or sponge, such as a thermally conductive plastic or a porous ceramic for example.
As opposed to an open cell metal foam, the foraminous heat conductor can be extruded with a foaming agent, deep pressed, machined, sintered, or fabricated by another manufacturing method to create a foraminous heat conductor with a relatively high surface area. The surface of the foraminous heat conductor can be treated or coated. The surface of the foraminous heat conductor can be treated or coated with a hydrophilic material to encourage the spread of water over a large surface area. The foraminous heat conductor may be treated or coated to prevent or reduce oxidation.
The foraminous heat conductor can be wire wrapped, glued, clipped, clamped, bonded to a frame, or otherwise affixed to the heater element.
As an alternative to the metal foam, the foraminous heat conductor can be, or further comprise a high density metal mesh.
The foraminous heat conductor can be an interchangeable, replaceable component.
6.3 Foraminous Aerosol Filter
In a situation where aerosolised water droplets might be formed, a foraminous aerosol filter can be used to prevent aerosols from escaping from the tub. One example is illustrated in
6.4 Fluid Feeder
The fluid feeder used in the embodiments can be an active system, or a passive system. For example, it can be driven by an electric pump, an electro-osmotic pump, a gravity feed system (including at least one control valve for example), breathing circuit pressure, suction pressure (generated by a venturi located along the gas flow path), or capillary pressure.
Water flow can be measured by a thermal mass flow sensor, or inferred indirectly (for example the overfeeding of water can be inferred by reading the temperature of the heater element, or by reading the humidity within the tub). Additionally, the water flow actuated by the pump may be controlled by calling up running speed, either automatically and/or manually. These measures prevent water from accumulating and overflowing out of the tub.
As shown in
There could be a liquid water sensor (not shown) in the tub. When activated, the liquid water sensor would prompt the controller to reduce the water pump rate. Alternatively, an algorithm can be programmed into the controller, taking input variables such as available power, flow rate, temperature inputs, and the like.
6.5 Tub
Some alternative embodiments of the tub are envisioned (as alternative to the configuration shown in earlier embodiments, where gas passes into the top of the tub and out of the top):
To minimise environmental heat loss and condensation build-up inside the humidifier, the tub and/or the mixing chamber may be double walled or otherwise insulated. Additionally, the air could be pre-heated prior to reaching the humidifier to reduce condensation build-up. The tub and mixing chamber may be combined into a single chamber.
6.6 Method of Humidifying Gases
There can be a method of humidifying a flow of gases using a humidifier comprising a heater. This involves heating the heater, feeding a flow of gases into the humidifier, and feeding fluid to the heater such that fluid vaporises upon contact with the heater. The heater can have a heat conductor, preferably comprising foraminous material, and fluid can be dripped onto the heat conductor.
One or more of a fluid reservoir, a pump, and a feed-line can be used to feed water onto a heater of a humidifier. This involves operating a pump to pump fluid from a fluid reservoir through a feed-line, and feeding fluid to the heater. The flow of fluid fed to the heater is fed at an adjustable flow rate, in which the flow rate is determined based on desired humidity and/or flow of gas through the humidifier. In some embodiments, the act of feeding fluid to the heat conductor (or heater) involves dripping fluid onto the heat conductor (or heater).
There can be a method of heating a humidifier comprising a heater element, and a heat conductor. This involves operating the heater element, which generating heat, as well as conducting heat from the heater element to the heat conductor. The heater element can comprise PTC material, and the heat conductor can be foraminous.
A controller can also be implemented to perform any one of the method steps described in this method embodiment, unless context dictates otherwise.
Any of the earlier described medical gases delivery system embodiments and/or earlier described humidifiers embodiments can be used for a method of humidifying a flow of gas and/or for a method of heating a humidifier. This can also include any combination of preferred/optional features that can be added onto any of the earlier described medical gases delivery system embodiments and/or earlier described humidifiers embodiments.
6.7 Application of the Embodiments
Any of the earlier described medical gases delivery system embodiments and/or earlier described humidifiers embodiments can be used in any situation where humidification is desired. This can also include any combination of preferred/optional features that can be added onto any of the earlier described medical gases delivery system embodiments and/or earlier described humidifiers embodiments.
1. A tub for a humidifier, comprising:
2. A tub according to clause 1, wherein the second heat conductor has voids in a solid structure.
3. A tub according to clause 1 or 2, wherein the foraminous heat conductor is foam.
4. A tub according to clause 3, wherein the foam is open cell foam.
5. A tub according to clause 3 or 4, wherein the foam is formed from metal or ceramic.
6. A tub according to any one of clauses 1 to 5, wherein the tub is adapted to receive an injection of water.
7. A tub according to clause 6, wherein the tub is adapted to receive the injection of water from a fluid delivery apparatus.
8. A tub according to any one of clauses 1 to 7, wherein the tub is adapted to be installed in a humidifier with a heater element to heat the first and/or second heat conductor.
9. A tub according to clause 8, wherein the heating element comprises a positive temperature coefficient (PTC) material.
10. A tub for a humidifier according to any of clauses 1 to 9, wherein the humidifier is:
11. A humidifier for humidifying a gas, comprising:
12. A humidifier according to clause 11, wherein the second heat conductor has voids in a solid structure.
13. A humidifier according to clause 11 or 12, wherein the foraminous heat conductor is foam.
14. A humidifier according to clause 13, wherein the foam is open cell foam.
15. A humidifier according to clause 13 or 14, wherein the foam is formed from metal or ceramic.
16. A humidifier according to any one of clauses 11 to 15 further comprising a fluid delivery apparatus for injecting fluid onto the first and/or second heat conductor.
17. A humidifier according to clause 16, wherein the first and/or second heat conductor is adapted to substantially vaporise fluid injected by the fluid delivery apparatus when fluid contacts the first and/or second heat conductor.
18. A humidifier according to any of clauses 11 to 17, wherein the humidifier is:
19. A humidifier according to any of clauses 11 to 18, wherein the second heat conductor is adapted to vaporise aerosolised fluid when aerosolised fluid contacts the second heat conductor.
20. A humidifier according to any one of clauses 11 to 19, further comprising a tub.
21. A humidifier according to clause 20, wherein the first and second heat conductors are disposed within the tub.
22. A humidifier according to any one of clauses 11 to 21, wherein the first and/or second heat conductor is foraminous.
23. A humidifier according to clause 22, wherein the first and/or second heat conductor has voids in a solid structure.
24. A humidifier according to clause 22 or 23, wherein the first and/or second heat conductor is foam.
25. A humidifier according to clause 23, wherein the foam is open cell foam.
26. A humidifier according to clause 24 or 25, wherein the foam is formed from metal or ceramic.
27. A humidifier according to any one of clauses 22 to 26, wherein the first and/or second heat conductor is a metal foam.
28. A humidifier according to claim any one of clauses 11 to 27, wherein the first heat conductor is thermally connectable to the heating element.
29. A humidifier according to any one of clauses 11 to 28, wherein the heating element comprises a positive temperature coefficient (PTC) material.
30. A humidifier according to any one of clauses 11 to 29, wherein the heating element self-regulates the upper limit of its temperature.
31. A humidifier according to any one of clauses 11 to 30, wherein the humidifier is:
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2020/057376 | 8/5/2020 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 62882985 | Aug 2019 | US |
