Humidification of respiratory gases

A tub is configured to contain a supply of water and be inserted into a chamber of a humidifier. The tub includes a tub base configured to contain a supply of water and a tub lid connected to the tub base. The tub lid includes an inlet configured to receive a flow of breathable gas to be humidified and an outlet for the humidified flow of breathable gas. The tub further includes a water level indicator configured to indicate a level of the supply of water in the tub base. The water level indicator includes an inclined portion configured to direct the flow of breathable gas from the inlet away from the outlet. The water level indicator may be visible through the inlet.

FIELD OF THE TECHNOLOGY

The present technology relates to systems and method to control the humidity of breathable gases used in all forms of respiratory apparatus ventilation systems including invasive and non-invasive ventilation. Continuous Positive Airway Pressure (CPAP), Bi-Level therapy and treatment for sleep disordered breathing (SDB) conditions such as Obstructive Sleep Apnea (OSA), and for various other respiratory disorders and diseases.

BACKGROUND OF THE TECHNOLOGY

Respiratory apparatuses commonly have the ability to alter the humidity of the breathable gas in order to reduce drying of the patient's airway and consequent patient discomfort and associated complications. The use of a humidifier placed between the flow generator and the patient mask produces humidified gas that minimizes drying of the nasal mucosa and increases patient airway comfort. In addition in cooler climates, warm air applied generally to the face area in and about the mask is more comfortable than cold air.

Many humidifier types are available, although the most convenient form is one that is either integrated with or configured to be coupled to the relevant respiratory apparatus. While passive humidifiers can provide some relief, generally a heated humidifier is required to provide sufficient humidity and temperature to the air so that the patient will be comfortable. Humidifiers typically comprise a water tub having a capacity of several hundred milliliters, a heating element for heating the water in the tub, a control to enable the level of humidification to be varied, a gas inlet to receive gas from the flow generator, and a gas outlet adapted to be connected to a patient conduit that delivers the humidified gas to the patient's mask.

Typically, the heating element is incorporated in a heater plate which sits under, and is in thermal contact with, the water tub.

SUMMARY OF THE TECHNOLOGY

One aspect of the technology is a humidifier for a respiratory apparatus that includes a chamber that is pressurisable to reduce the pressure on joints of the humidifier tub (which is placed within the pressurised chamber) to reduce leaks.

A further aspect of the technology is a humidifier for a respiratory apparatus that includes a chamber that is pressurisable to reduce tolerances for insertion of a tub with respect to seals on an inlet and an outlet tube of the humidifier chamber.

A still further aspect of the technology is a humidifier for a respiratory apparatus that directs air over the surface of a supply of water contained in a tub to humidify a flow of breathable gas regardless of the water level.

Another aspect of the technology is a humidifier for a respiratory apparatus that includes seals that are not under the supply of water, thus reducing a risk of water leakage.

Yet another aspect of the technology is a humidifier for a respiratory apparatus that includes a tub that is disposable.

Another aspect of the technology is a humidifier for a respiratory apparatus that includes a tub that is cleanable and/or reusable by disinfection and/or sterilisation methods.

Still another aspect of the technology is a humidifier for a respiratory apparatus that includes a tub that comprises a water level indicator, for example a water level indicator that indicates a maximum fill level, working, indicia and/or a marking, etc, e.g., arranged in a way (e.g., on an incline) that allows visual discrimination of water level.

A still further aspect of the technology relates to a water level indicator in a tub that may be viewed through a window of the humidifier. An even further aspect of the technology relates to a water level indicator that appears to change colour as the water level changes, for example appears to be a darker colour or mixture of colours, in order to enhance visual discrimination of the water level.

A further aspect of the technology relates to a tub that is removable from the humidifier and is configured to prevent any water flowing out of the tub from flowing back into the flow generator.

A still further aspect of the technology is a humidifier for a respiratory apparatus that prevents water from spilling back into a flow generator, or blower, that generates a flow of breathable gas.

According to an example, a tub configured to contain a supply of water and to be inserted into a chamber of a humidifier comprises a tub base configured to contain a supply of water; a tub lid connected to the tub base, the tub lid including an inlet configured to receive a flow of breathable gas to be humidified and an outlet for the humidified flow of breathable gas; and a water level indicator configured to indicate a level of the supply of water in the tub base, the water level indicator comprising an inclined portion configured to direct the flow of breathable gas from the inlet away from the outlet, and to improve the efficiency of moisture pick-up in to the air. This is achieved by the geometry of the inclined portion to promote swirl of the air above the water level.

According to another example, a tub configured to contain a supply of water and to be inserted into a chamber of a humidifier comprises a tub base configured to contain a supply of water; a tub lid connected to the tub base, the tub lid including an inlet configured to receive a flow of breathable gas to be humidified and an outlet for the humidified flow of breathable gas; and a water level indicator configured to indicate a level of the supply of water in the tub base. The water level indicator comprises an inclined portion, and the water level indicator is visible through the tub air inlet.

According to still another example, a humidifier for humidifying a flow of breathable gas to be delivered to a patient comprises a chamber configured to receive the flow of breathable gas; a lid provided on the chamber and being movable between an open position and a closed position; a seal provided on the lid, the seal being configured to seal the chamber such that the flow of breathable gas pressurizes the chamber; and a tub as disclosed herein.

According to a further example, a respiratory apparatus for providing a humidified flow of breathable gas to a patient comprises a flow generator to generate a flow of breathable gas and a humidifier and/or a tub as disclosed herein.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

PAP System

As schematically shown inFIG. 1, a Positive Airway Pressure (PAP) system, for example a Continuous Positive Airway Pressure (CPAP) system, generally includes a PAP device10, an air delivery conduit20(also referred to as a tube or tubing), and a patient interface50. In use, the PAP device10generates a supply of pressurized air that is delivered to the patient via an air delivery conduit20that includes one end coupled to the outlet of the PAP device10and an opposite end coupled to the inlet of the patient interface50. The patient interface comfortably engages the patient's face and provides a seal. The patient interface or mask may have any suitable configuration as is known in the art, e.g., full-face mask, nasal mask, oro-nasal mask, mouth mask, nasal prongs, etc. Also, headgear may be utilized to comfortably support the patient interface in a desired position on the patient's face.

In embodiments, a humidifier may be incorporated or integrated into the PAP device or otherwise provided downstream of the PAP device. In such embodiments, the air delivery conduit20may be provided between the patient interface50and the outlet of the humidifier15as schematically shown inFIG. 2.

It should be appreciated that the air delivery conduit may be provided along the air delivery path in other suitable manners. For example, as schematically shown inFIG. 3, the humidifier15may be a separate component from the PAP device10so that an air delivery conduit20(1) is placed between the PAP device10and the humidifier15and another air delivery conduit20(2) is placed between the humidifier15and the patient interface50.

Generally, a heated humidifier is used to provide sufficient humidity and temperature to the air so that the patient will be comfortable. In such embodiment, the air delivery conduit may be heated to heat the gas and prevent “rain-out” or condensation forming on the inside of the conduit as the gas is supplied to the patient. In this arrangement, the air delivery conduit may include one or more wires or sensors associated with heating.

Referring toFIGS. 4-6, a PAP system10according to a sample embodiment comprises a flow generator, or blower,12and a humidifier15. The flow generator12is configured to generate a flow of breathable gas having a pressure of, for example, about 2-30 cm H2O. The flow generator comprises a power button2to turn the PAP system on and off. A display4is provided to display interactive menus and information regarding the operation of the PAP system to the user or operator. The user or operator may select menus and/or information through inputs6, which may be, for example, buttons or keys. A push button dial8may also allow the user or operator to select information and/or menus. The inputs6and the push button dial8may be used together to select information and/or menus.

The humidifier15comprises a humidifier chamber16and a lid18which is pivotable between an open and a closed position. A humidifier water chamber, or tub,14is provided in the humidifier chamber16and is covered by the lid18when the lid18is in the closed position. A seal19is provided to the lid18. The lid18includes a window30to allow visual inspection of the contents of the humidifier tub14. The seal19includes an aperture31that corresponds to the position of the window30of the lid18. In the closed position of the lid18, the seal19contacts the tub14to ensure good thermal contact between a bottom of the tub14and a heating plate (not shown) provided in the bottom of the humidifier chamber16as disclosed, for example, in WO 2010/031126 A1

As shown inFIGS. 4 and 5, the humidifier15is connectable to the flow generator12by connectors, or latches,24that engage corresponding recesses (not shown) in the flow generator12. An electrical connector26is provided to electrically connect the flow generator12to the humidifier15.

As shown inFIG. 4, the tub14comprises a tub lid86that is configured to direct a flow of breathable gas generated by the flow generator12into a channel90(best shown inFIG. 7) in the tub lid86from a channel inlet through to a channel outlet91(FIG. 18) of the channel90into the tub14. The humidifier chamber16includes an air inlet22configured to receive the flow of breathable gas generated by the flow generator12when the humidifier15is connected to the flow generator12. The inlet22directs the flow into the channel90in the tub lid86of the tub14. The flow is directed by the channel90to the inlet93into the tub14. The tub14includes an outlet88for the humidified flow of breathable gas. A tube connector (not shown) may be provided at a rear portion of the humidifier15in communication with the outlet88and configured for connection to a hose, tube, or conduit that is configured to deliver the humidified flow to patient interface, e.g., a mask. It should be appreciated that the outlet88may be provided separately from the tub lid86, for example it may be part of the tub base or provided as a separate element.

The humidifier15may include a control system, or controller, for example, a microprocessor provided on a printed circuit board (PCB). The PCB may be located in the wall of the humidifier chamber16and may include a light, e.g., a Light Emitting Diode (LED), to illuminate the contents of the tub14to permit visual inspection of the water level. Referring toFIG. 6, an aperture35may be provided in the wall of the humidifier chamber16to allow the light on the PCB to illuminate the humidifier chamber16. The aperture35may be covered with a cover (not shown) to prevent access to the PCB and the light (e.g. LED) from the humidifier chamber16. The cover may be transparent or colored to provide a colored light, such as a green light to appear within the humidifier chamber16. The light is provided to shine into the humidifier chamber16to allow the water level in the water tub14to be seen.

It should also be appreciated that the flow generator12comprises a control system, or controller, that communicates with the controller of the humidifier15when the flow generator12and the humidifier15are electrically connected. The PAP system10may be operated according to various control algorithms stored in the controller(s) of the flow generator12and/or the humidifier15. Such control algorithms are disclosed in, for example, U.S. Patent Application Publication 2009/0223514 A1, the entire contents of which are incorporated by reference.

The humidifier15comprises the humidifier chamber16and the lid18which is pivotally connected to the humidifier chamber16. As shown inFIGS. 4 and 6, the lid18comprises a hinge portion17that is hinged to hinge portions47provided on the humidifier chamber16. An opening member28is provided for releasing the lid18to allow the lid to be pivoted to the open position shown inFIGS. 4 and 6as described in WO 2010/031126 A1. Referring toFIGS. 4 and 5, the lid18comprises catches (not shown) that are configured to be engaged by latches44to maintain the lid18in the closed position. The seal19is configured to engage the water tub14, for example the tub lid86, when the lid18is in the closed position to push the tub14toward an outlet34of the humidifier chamber16to assist in forming a seal between the water tub outlet88and the humidifier chamber outlet34. The seal19is also configured to push the water tub14against a heating plate (not shown) when the lid18is in the closed position. The seal19is also configured to seal, when the lid18is in the closed position, the tub emptying aperture89provided in the tub lid86.

As shown inFIG. 6, the humidifier chamber16comprises a humidifier cradle32that includes the air inlet22. The humidifier cradle32also includes the humidifier chamber outlet34to allow the humidified flow to be delivered to a delivery hose, tube, or conduit that is configured to be connected to the humidifier to deliver the humidified flow to a patient. The outlet34is provided in a back side of the humidifier cradle32. It should be appreciated that the outlet34may be provided on a side of the humidifier cradle32. Such a modification would also entail modifying the tub14to align the outlet88of the tub14with the outlet34of the humidifier cradle32.

As also shown inFIG. 6, the humidifier cradle32is supported by a chamber bottom54of the humidifier chamber16, as disclosed in WO 2010/031126 A1

Referring toFIGS. 7-27, the humidifier tub14comprises a tub base82configured to contain a supply of water and a tub lid86that includes a channel90that receives the flow of breathable gas generated by the flow generator12that enters the humidifier15through the air inlet22. The outlet91of the channel90is configured to direct the flow into the inlet93of the tub lid86when the tub lid86is secured to the tub base82as described in more detail below. The tub lid86includes an opening300and a sump region340that surrounds the inlet93of the tub lid86to direct the flow of air from the flow generator to the water contained in the tub14. The sump region340also facilitates filling the tub14by providing a larger area for entry of water than the inlet93of the tub lid86. A tub emptying aperture89may also be provided in the tub lid86.

FIGS. 29-38show another example of the present technology, wherein like elements have been identified by like parts, but with a “prime”, e.g.,100′, added.

Referring toFIGS. 7, 10, 11, 14, 15, 18-21, the opening300of the sump region340may be as shown, e.g. generally rectangular with D-shaped ends, or may be any other shape, for example oval, elliptical, or round. The opening300and the sump region340may be large enough to reduce the amount of water that misses the inlet93during filling and to buffer the water when poured in a rate that exceeds the filling capacity of the inlet93. The inlet93may be provided in the bottom of the sump region340, as shown inFIGS. 4, 7, 10, 11, 14, 15, 18 and 19, at a position that prevents water from exiting the tub14through the inlet93when the tub14is tilted, for example 90°, toward the flow generator12. As shown inFIG. 21, the outlet91of the channel90is above the inlet93to reduce the possibility of water entering the channel90during filling or due to splashing.

The tub lid86also comprises a cover portion301that covers the section of the flow channel90from the flow generator12to the outlet91of the channel90that is angled down towards the flow generator12. The cover portion301prevents any water from flowing back into the flow generator12if the tub14was filled with water while still connected to the flow generator12as water may only be poured into the tub in the region provided by the opening300which is designed to channel the water down towards the inlet93of the tub lid86.

As shown inFIGS. 7-9, the tub lid86may be secured to the tub base82by a plurality of clips106,108provided on a latching plate100, although it should be appreciated that the clips106,108may be provided on the tub base82. The clip108may have an aperture110configured to accommodate the outlet88of the tub14. The tub lid86may include projections128that are received in apertures129in the clips106. The tub lid86may also include projections152that are received in apertures151provided in the clip108.

As also shown inFIGS. 7-9, the tub lid86may include recesses330to accommodate the fingers of a user of the tub or a clinician to provide a space between the tub lid86and the clips106as the user inserts the tub lid86on to the tub base82so that the projections128are received in the apertures129. The recesses330may also accommodate the fingers during removal of the lid86from the base82, for example to allow the parts of the tub14to be disassembled and cleaned.

Referring toFIGS. 22-25, the latching plate100comprises the clips106,108that may be integrally formed with the latching plate100by, for example, living hinges125. The latching plate100may be formed of, for example, polypropylene (PP) which will allow the living hinges125to be open and closed a large number of times without breaking. Polypropylene is also inexpensive and has good chemical resistance and is a sturdy and tough material that is not brittle.

FIG. 22shows the latching plate100with the clips106,108in a “closed” position or configuration that retains the tub lid86to the tub base82andFIG. 23depicts the latching plate100in an “open” configuration with the clips106,108folded downwardly to permit insertion of the tub base82into the latching plate100as described in more detail below.

As shown inFIGS. 22 and 23, the latching plate100includes corner flanges111,115that extend from a rim123of the latching plate100. As shown inFIG. 24, the tub base82comprises corresponding corners131,135that facilitate alignment and assembly of the tub base82with the latching plate100, as shown inFIG. 25. The latching plate100is slid into place from the bottom of the tub base82so that the rim123of the latching plate100engages with, i.e. overlies, the rim118of the tub base82. The latching plate100is engaged with the tub base82by a friction fit (and this fit can be enhanced, e.g., by heating the plate to an elevated temperature and assembling these parts at that time) so that the latching plate100is retained when the clips106,108are in the open configuration shown inFIG. 25. The tub lid86is connected to the tub base82and secured in position by folding the clips106,108from the open position shown inFIG. 25to the closed position shown inFIG. 7. The humidifier tub14may then be inserted into the humidifier15as shown inFIG. 4.

Water Level Indicator

Referring toFIGS. 10-21, a water level indicator320may be provided to the tub lid86of the humidifier tub14that is visible through the window30of the lid18of the humidifier15. The light emitted from the PCB through the aperture35may improve the visibility of the water level on the water level indicator320. The water level indicator320may comprise a base portion307that extends from the tub lid86around the inlet93and an angled or inclined portion303extending from the base portion307. The inclined portion303may include markings304to indicate various water levels. The inclined portion303may also include indicia311(e.g. “MAX”) to indicate a maximum water fill level.

In the case ofFIG. 38, the indicator320′ may include a marking304′ (e.g., indicating the maximum fill level), and the indicia (e.g., wording such as “MAX”) may be written in a vertical orientation such that the indicator becomes progressively covered with water as the tub base is filled, e.g., the “X” in “MAX” is first covered then the “A”, then the “M” before reaching the fill line. Further, the lettering in the indicia may be dimensioned so that the individual letters increase (or decrease) in size in a direction towards the bottom of the tub. One or more of these measures should help the user better anticipate when the water level is approaching the maximum fill level, to prevent water from inadvertently overflowing. To this end, a vertically oriented line including an arrow304.1′ at its top end also indicates the direction of filling. The marking, indicia and/or wording may be placed and formed so that it is depressed into, projects from and/or is in-plane with its support surface.

As shown inFIGS. 19-21, the water level indicator320may be integrally formed with the tub lid86, e.g., the base portion307may be formed in one piece with the tub lid86via a molding process. Optionally the base portion303may extend half way around the inlet. This provides ease of manufacturing and assembly and reduces costs by reducing the number of components of the humidifier tub14. For example, the flow plate disclosed in WO 2010/031126 A1 may be eliminated from the tub. It should be appreciated, however, that the water level indicator320may be formed separately from the tub lid86and be attachable to, and detachable from, the tub lid86.

As the water level indicator320is located adjacent the water and airflow inlet93, a user can immediately see from the top, while pouring water into the sump region340, when the water level has reached a desired level, and/or the maximum level. This improves usability compared to, for example, a water level indicator that is located at a position distant from the water inlet93that must be looked at and checked separately from the filling process, or as a water line on the side of the tub as a user would have to tilt his or her head to determine the water level or look lower down at the side to see if water has filled to the desired or maximum level. In addition, when the tub14is placed inside the humidifier15and the lid18is closed to form a pressurised chamber, the window30allows a user or clinician to look from the top through the window30to see the tub14inside the humidifier15. The location of the inlet93and the water level indicator320is beneath the window30so the user or clinician can easily and immediately check the water level without having to open the lid18and/or take out the tub4. A user or clinician who suspects that the water has run out can visually check without stopping or disturbing the operation of the system. Reducing the need to remove the tub14from the humidifier15also allows the user or clinician to check water level without risking spillage of the water from the tub14and/or into the flow generator12.

The inclined portion303of the water level indicator320baffle is located generally in front of the outlet88of the tub14. This helps to deflect water away from the outlet88while filling the tub14by pouring water into the sump region340. Also, as the water inlet93is also the air inlet, when the airflow enters the interior of the tub14, it is deflected generally away from the outlet88, thus directing the airflow across the water surface before exiting the outlet88. As the pressurized air inflow is initially directed away from the outlet88there is less chance of splashing or spitting of water out of the outlet88. The shape, angle of incline, and location of the inclined portion303of the water level indicator320may be designed to provide a desired airflow profile to improve water vapour pickup by the airflow and to reduce the likelihood of water spitting or splashing out of the outlet88. The outlet conduit88may be angled upwards and the inclined portion303of the water level indicator320may be inclined to direct the pressurised airflow to not hit the water surface directly. A wall335may also be provided in the tub lid86to direct the airflow.

The water level indicator320, for example, the inclined portion303, may be formed of a colored plastic material, for example yellow. The water level indicator320may be, for example, translucent. When the tub20is filled with water, the water level indicator320may appear to change color, for example appearing slightly darker or a greenish-yellowish color as the water level rises.

As shown inFIG. 21, the inclined portion303may be at an angle α to a bottom plane of the tub lid86. The value of the angle α may depend on a combination of factors, including the size of the inlet93, the length of the inclined portion303, the depth of the tub base82, and/or the distance the inclined portion303extends into the tub base82and/or water. The angle α may be from just over 90° to just under 180°. The angle α should be sufficient to permit the inclined portion303, including the indicia, to be visible from generally above the tub, while not causing the inclined portion320to extend further than the radial length of the inlet93. That is, the inclined portion303should not extend under the portion of the sump region340surrounding the inlet93as such an overlapping of material (i.e. the inclined portion303and the sump region340) increases the moulding and tooling complexities associated with forming the tub lid86as a single piece. The angle may be, for example, about 115°-135°, for example about 125°. The angle α should improve the visibility of the indicia, for example by increasing the contrast of the colour of the indicia with the water level when viewed from above. The angle α should also allow the inclined portion303to extend deep enough into the tub base82to allow indication of the water level until it is quite low. The combination of the angle α and the length of the inclined portion303may be chosen to provide these results.

The angle α may also be designed so that the change in the air flow direction causes only a small increase in total pressure loss through the tub and so that a swirling action is created in the air flow due to the inclined portion303in combination with other internal tub features, e.g., wall335. The swirling versus pressure loss determination may be made using, for example, computational fluid dynamics (CFD) simulation.

As also shown inFIG. 21, the base portion307of the water level indicator320may be provided at an angle γ to a vertical axis of the tub. The angle γ may be, for example about 1°-10°, for example about 5°. The angle γ may improve water flow from the inlet93and swirl of the air flow over the surface of the water.

The outlet88has an axis at a downward angle β to the plane of the top of the humidifier lid86. The angle β may be, for example, about 25°-35°, for example about 29.5°. The top of the outlet88is also displaced a distance d from the top of the humidifier lid86that may be, for example, about 1 mm-10 mm, for example about 5.6 mm. The downward angle and displacement of the outlet88helps to prevent spill back of water from the tub.

As shown in the figures, the water level indicator320may be a rounded D-shape, although it should be appreciated that other shapes such as rectangular, square, triangular, oval or any other shape may be used.

The tub base82may be formed of, for example, metal. For the cleanable and reusable tub14, the tub base82may be formed of stainless steel. For a cleanable and disposable tub, the tub base may be formed of a lower cost conductive material such as aluminium or conductive polymers. It should be appreciated that the tub base82may be formed of other metals or alloys, or of other materials.

The tub lid86may be formed of, for example, a plastic material, such as polycarbonate. For example, the tub lid86may be formed of Makrolon 2458, manufactured by Bayer. For a cleanable and reusable tub, the tub lid may be formed of a dishwasher and/or disinfection safe material, such as polycarbonate. For a disposable tub, the tub lid may be formed from a lower cost material, such as ABS (acrylonitrile butadiene styrene). The tub lid86may be transparent, e.g. water clear, or may be translucent, including any colour of translucent material.

Referring toFIG. 28, a humidifier tub according to another sample embodiment and that is configured to be disposable is illustrated. The humidifier tub14may comprise a tub base82and a tub lid86having a channel90. The tub lid86may be the same as the tub lid of the cleanable humidifier tub discussed with respect toFIGS. 7-25. The tub lid86may be secured to the tub base82by, for example, welding, adhesive, and/or one or more clips.

The disposable tub base82may be formed of, for example, a metal, such as aluminium. It should also be appreciated that the disposable tub base82may be formed of other metals or alloys, or from a plastic material.

Referring toFIGS. 26 and 27, a seal112may be provided on the rim120of the tub lid86. The rim120includes a recess, or receptacle,121extending around the periphery of the tub lid86to receive the seal112. The recess121includes a projection122that is configured to be received in a recess113of the seal112. The seal112includes a sealing projection, or sealing edge,114that is configured to be deformed when the tub lid86and the tub base82are connected together, for example when the clips106,108of the tub base82are connected to the projections128,152of the tub lid86, or when the tub lid86is adhered or welded to the tub base82. As seen inFIGS. 33 and 37, the base82′ includes a surface82.1that engages the projection or edge114′. The deformation of the sealing projection, or edge,114creates a watertight seal between the tub base82and the tub lid86. The projection122of the receptacle121of the rim120of the tub lid86directs a force to the sealing projection114when the tub base82and tub lid86are connected to facilitate deformation of the sealing projection114. It should be appreciated that the tub lid86and the seal112may be formed of the same material, for example silicone or Thermoplastic elastomer (TPE), and the tub lid86and the seal112may be integrally formed in one piece. It should also be appreciated that the seal112may be formed of, for example, silicone or TPE, and molded on to the tub lid86.

The humidifier14does not include any seals that are provided under the water supply of the tub base82. The humidifier lid18comprises the seal19to allow for pressurizing of the humidifier chamber16with the flow provided by the flow generator12to reduce the pressure on the tub joints, including the disposable tub and the reusable, cleanable tub, thus reducing leaks. Pressurizing the humidifier chamber also reduces tolerances for insertion of the water tub with respect to seals on the inlet of the humidifier and the outlet tube of the humidifier14.

The seal for the cleanable and reusable tub and the seal for the disposable tub may be formed of different materials and/or different colours. For example, the seal112of the cleanable and reusable tub may be formed of silicone. The seal112of the disposable tub may be formed of, for example, TPE material, such as Dynaflex G6713-0001—Yellow [PMS 107C], manufactured by GLS Thermoplastic Elastomers (yellow colour pigment by PolyOne Corporation). It should be appreciated that the seals for the reusable and cleanable tub and for the disposable tub may be the same material and/or the same colour. It should also be appreciated that the material of the seal112may be moulded onto at least a portion of the water level indicator320, for example on the indicia304and/or311and/or on the inclined portion303, to improve the visibility of the water level indicator.

While the invention has been described in connection with what are presently considered to be the most practical and preferred examples, it is to be understood that the invention is not to be limited to the disclosed examples, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the technology. Also, the various examples described above may be implemented in conjunction with other embodiments, e.g., an aspect of one example may be combined with an aspect of another example to realize yet other examples. Further, each independent feature or component of any given assembly may constitute an additional example. Furthermore, each individual component of any given assembly, one or more portions of an individual component of any given assembly, and various combinations of components from one or more examples may include one or more ornamental design features. In addition, while the technology has particular application to patients who suffer from OSA, it is to be appreciated that patients who suffer from other illnesses (e.g., congestive heart failure, diabetes, morbid obesity, stroke, barriatric surgery, etc.) can derive benefit from the above teachings. Moreover, the above teachings have applicability with patients and non-patients alike in non-medical applications.

It will further be understood that any reference herein to known prior art does not, unless the contrary indication appears, constitute an admission that such prior art is commonly known by those skilled in the art to which the technology relates.