Humidifier with Internal Heating Element and Heater Plate
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a gases supply and gases humidification apparatus, particularly,
but not solely, for providing respiratory assistance to patients or users who require a supply of
gas at positive pressure for the treatment of diseases such as Obstructive Sleep Apnea (OSA),
snoring or Chronic Obstructive Pulmonary Disease (COPD) and the like. In particular, this
invention relates to a humidifier chamber for use in a gases supply apparatus.
Summary of the Prior Art
A number of methods are known in the art for supplying humidified gases to a patient to
assist a patient's breathing. Continuous Positive Airway Pressure (CPAP) involves the
administration of air under pressure to a patient, usually by passing gases to the patient or user
through a nasal mask. CPAP therapy is used in the treatment of snoring and Obstructive Sleep
Apnoea (OSA), a condition characterised by repetitive collapse of the upper airway during
inspiration. Positive pressure splints the upper airway open, preventing collapse. Treatment of
OSA with CPAP has proven generally to be both effective and safe.
CPAP is also commonly used for patients with a variety of respiratory illnesses, including
COPD (Chronic Obstructive Pulmonary Disease).
One of the side effects of CPAP therapy is that the stream of air can dry the nasal
membranes, or the mouth and throat membranes of a user. This can lead to these areas
becoming inflamed and uncomfortable. In order to counteract this side effect, it is usual for the
air that is provided to a user to be humidified, by adding a humidification chamber or similar into
the gases stream before the gas is provided to the patient. The gases enter the humidifier
chamber, and are humidified as they pass over a volume of heated water contained in the
chamber.
An ideal system is one that can deliver gas at the required pressure and temperature, with
a maximum amount or maximum volume of water vapour contained in the gas. That is, gas at
substantially 100% saturation or absolute humidity, delivered to a user at a relatively high
temperature (the higher the temperature of the gas, the greater the volume of water vapour that it
can contain). An ideal delivery temperature is one that is either the same as or slightly higher
than the body temperature of the user.

Although systems exist that locate the humidifier close to the user, this arrangement tends
to add weight close to the patient, and can increase their discomfort and decrease the usability of
the system. Therefore, it is usual to locate the humidifier chamber remotely from the patient,
with the heated humidified gases transported to the patient via a heated conduit
A known (prior art) example of a system where the humidifier chamber is located
remotely from the user is shown in Figure 1. Gases are passed to the patient by way of a patient
interface 2. In the system shown in Figure 1, the interface 2 is a nasal cannula. However, full-
face masks, nasal masks, nasal cannulas, oral mouthpieces, tracheostomy connections, or any
other suitable interface can be used with these systems.
The cannula 2 is connected to a gases transportation pathway or inspiratory conduit 3
that in turn is connected to a humidifier chamber 5. A flow of gases is provided through the
chamber 5 by an integrated blower unit contained within the housing 10.
Atmospheric air enters the housing 10 through an inlet 9 on the back of the casing 10,
and is pressurised by a blower or fan assembly. The air is then passed into the humidification
chamber 5 through an inlet 11. The humidification chamber 5 extends out from the housing 10
and can be removed and replaced by the patient or other user. The chamber 5 contains a volume
of water that is heated via the base 13 of the chamber 5. The base 13 is heated by contact with
an adjacent heated plate (not shown) that forms part of the system contained within the casing
10. The inspiratory conduit 3 is connected to the outlet 8 of the humidification chamber 5. It is
usual for the walls of inspiratory conduit 3 to contain heating means or heater wires 7 that heat
the walls of the conduit to reduce or eliminate the formation of condensation.
The gases supply and humidifying device contained within the housing 10 can be
provided with a control means or an electronic controller such as a microprocessor that executes
computer software commands stored in an associated memory. The user of the device may set a
predetermined required value (preset value) of humidity or temperature of the gases supplied to
patient 1, via a control interface such as a dial or buttons on a control pad or paneL
In response to the user set humidity or temperature value input, and other possible inputs
such as system sensors that sense gases flow or temperature, the controller determines when (or
to what level) to energise the heater plate. This in turn heats the volume of water 6 within
humidification chamber 5 (via the conductive base 13). Water vapour fills the volume of the
chamber above the surface of the water 6, rising from the surface of the water 6. Gases from the
blower or fan pass into the chamber- 5 through inlet 11 and become humidified as they pass
across the top half of the chamber 5, that is, that part of the chamber 5 not filled with water 6.

The heated and humidified gas then passes out of the humidification chamber 5 via outlet
8 as fresh gases from the blower enter the chamber and displace the humidified, saturated gases.
The supply of gases through the inlet 11 is varied by a variable speed pump or fan 19 that
draws air or other gases through the inlet 9. The speed of the variable speed pump or fan is
preferably controlled by the control means or electronic controller described above.
Typically, humidification chambers such as chamber 5 are formed as a hollow shell with
an open base. The shell is typically formed from a plastics material. A highly heat conductive
metal plate 13 is added to close the open base, closing and sealing the chamber 5, except for the
inlet 11 and oudet 8. In use, the base 13 is in direct contact with the heater plate. When the
chamber 5 is in position substantially the entire surface area of the base 13 contacts the heater
plate.
It should be noted that Figure 1 merely illustrates one form of a suitable integrated gases
supply and humidifying device. Other suitable gases supply systems, for example those that use
fully separate or independent blowers and humidifiers connected in series, can also be used.
There are several disadvantages when using prior art systems of the type described above
where the humidification chamber is located remotely from the patient Some of these
disadvantages are outlined below:
• It is normally assumed that gases leaving the humidifier chamber are in a state of
absolute humidity (100% saturated with water vapour). As described above, this
saturated condition is desirable as it delivers a maximum amount of water vapour to
the end user, and minimises any drying out of nasal or throat membranes. However,
there is no guarantee that the gases leaving such humidifiers are in fact 100%
saturated. This is because the saturation state of the gas leaving the chamber depends
on a number of factors, including the temperature of the gas as it enters the chamber,
the temperature of the water in the chamber, and the rate at which the gas passes
through the chamber. Typically, humidification systems are only controlled to
achieve a desired outlet gas temperature (not humidity).
• Intermittent or varying flow rates (caused for example by fluctuating demand from
the user's breathing) will cause the humidity of the gas passing out from the humidity
chamber to be uneven. Air that passes through the humidifier at a high flow rate has
had little time to be heated and humidified, while low flow rate gas lingers in the
chamber longer, and therefore absorbs more water vapour, leaving the chamber at a
higher absolute humidity. Varying flow rates caused by fluctuating user demand

cause the flow rate of the gas through the chamber to vary at a greater rate than it is
possible to compensate for using a control/feedback loop. It is not possible to
compensate for varying flow rates by varying the inputs, eg. varying heater power.
• It is usual for humidifiers of the prior art type to be heated from the base. That is, the
base of the humidifier chamber is made of a conducting material, with the volume of
water in the chamber heated via this base. Air from the respirator or blower enters
the chamber at or towards one side, above the level of the water within the chamber.
The air passes over the heated water and becomes humidified, and then exits the
chambet at the far side. This arrangement can be inefficient. If air or gas enters the
chamber at a lower temperature than the water and the saturated vapour in the
chamber, it is likely that the gas will exit the chamber in a state where it is not fully
saturated (not in a state of absolute humidity).
In an attempt to overcome or minimise these difficulties, some priot art systems preheat
gases before they enter the humidification chamber. However, these gases can lose heat energy
as they travel from the pre-heater to the humidification chamber. It is usually not possible to
retrofit a pre-heater in an existing blower unit. Therefore, in a gases supply and gases
humidification system if a pre-heater is to be added, the blower unit most often needs to be
replaced. This can be expensive.
United States Patent Number 6,918,389 discloses a humidifier and sensor for use with a
breathing assistance apparatus. A number of different configurations of humidification chambers
are disclosed. Also disclosed are a number of methods and apparatus for heating the gases
passing through the humidifier chambers. In particular, this patent discloses chambers that
include an internal hearing element such as a metal scroll element, a porous material element, or a
semipermeable membrane. These elements provide both wet and dry heating of the gases
passing through the chamber. This patent also discloses using heaters to preheat gases entering
the chamber.
United States Patent Number 4,753,758 discloses a respiratory humidifier with an internal
partition wall, dividing the humidifier into a water reservoir and a humidification enclosure. The
partition wall allows water vapour or humidified gas to pass through from the water reservoir to
the humidification enclosure, but does not allow liquid water or water in droplet form to pass
through. A second heater, having the form of a conical finned heater, can be located in the
humidification enclosure to provide additional hearing. The finned heater as described is
centrally located and there is no direct heating of the gases passing through the inlet or outlet

ports of the humidifier. The partition wall described includes a filter element Several different
alternative filter constructions are described. A certain amount of system pressure is required to
force the water and gas through filters of this type.
DISCLOSURE OF THE INVENTION
It is an object of the present invention.to provide a breathing assistance apparatus which
goes some way to overcoming the abovementioned disadvantages or which at least provides the
public or industry with a useful choice.
Accordingly in a first aspect the present invention consists in a respiratory humidifier
chamber for use with a breathing assistance apparatus, said chamber comprising:
a watertight vessel having an inlet adapted for receiving gases from said breathing
assistance apparatus, and an outlet through which heated humidified gases exit said vessel for
delivery to a patient,
a partition, dividing said vessel into an upstream sub-chamber and a downstream sub-
chamber, said sub-chambers sealed from each other by said partition except for an aperture, said
aperture passing through said partition and allowing gaseous communication between said sub-
chambers,
said downstream sub-chamber including a beater base, adapted to heat a volume of water
contained within said downstream sub-chamber in use, said aperture located above said volume
of water in use,
said upstream sub-chamber containing an internal heater, adapted to heat gases passing
through said upstream sub-chamber from said inlet to said aperture3 at least part of said internal
heater located immediately adjacent said aperture.
Preferably said internal heater is configured so as to provide a tortuous path for said gases
as they pass through said upstream sub-chamber.
Preferably said internal heater is a fin heater having a plurality of fins.
Preferably the fins of said fin heater are aligned substantially perpendicular to a direct
flow path between said inlet and said aperture.
Preferably said tortuous path is formed by offsetting adjacent ones of said fins.
Preferably said heater base and said internal heater are separate.
Alternatively said heater base and said internal heater are a single heater, controEed and
powered from a single source.
In a second aspect the present invention consists in a breathing assistance apparatus for
delivery of respiratory gases to a patient comprising:

a gases supply device, adapted to provide a flow of pressurised gases through said system,
a humidifier chamber, having an inlet and an outlet, said chamber adapted to receive said
flow of gases from said breathing assistance apparatus via said inlet, and provide a supply of
heated humidified gases through said oudet,
a delivery conduit, adapted to connect to said outlet and receive said heated humidified
gases,
a patient delivery interface, adapted to receive said gases from said delivery conduit and
deliver these to said patient,
said humidifier chamber comprising a watertight vessel having an inlet adapted for
receiving gases from said breathing assistance apparatus, and an outlet for delivering heated
humidified gases to a patient via said conduit and said interface,
a partition, dividing said vessel into an upstream sub-chamber and a downstream sub-
chamber, said sub-chambers sealed from each other except for an aperture passing through said
partition, said aperture allowing gaseous communication between said sub-chambers,
said downstream sub-chamber including a heater base, adapted to heat a volume of water
contained within said downstream sub-chamber in use, said aperture located above said volume
of water in use,
said upstream sub-chamber containing an internal heater, adapted to heat gases passing
through said upstream sub-chamber from said inlet to said aperture, at least part of said internal
heater located immediately adjacent said aperture.
To those skilled in the art to which the invention relates, many changes in construction
and widely differing embothments and applications of the invention will suggest themselves
without departing from the scope of the invention as defined in the appended claims. The
disclosures and the descriptions herein are purely illustrative and are not intended to be in any
sense limiting.
In this specification where reference has been made to patent specifications, other
external documents, or other sources of information, this is generally for the purpose of
providing a context for discussing the features of the invention. Unless specifically stated
otherwise, reference to such external documents is not to be construed as an admission that such
documents, or such sources of information, in any jurisdiction, are prior art, or form part of the
common general knowledge in the art
The invention consists in the foregoing and also envisages constructions of which the
following gives examples.

BRIEF DESCRIPTION OF THE DRAWINGS
Preferred forms of the present invention will now be described with reference to the
accompanying drawings.
Figure 1 shows a schematic view of a prior art breathing assistance apparatus for delivery
of heated and humidified gases to a user or patient, the apparatus including a humidifier chamber.
Figure 2a shows a sectional side view of the humidifier chamber of the present invention
that can be used with the breathing assistance apparatus of Figure 1 in place of the prior art
humidifier chamber, the humidifier chamber of the present invention having a fin heater
occupying the upstream half of the chamber and forming a tortuous path through the chamber,
and a separate heater base in the downstream half of the chamber.
Figure 2b shows the humidifier chamber of Figure 2a, where the fin heater and the base
are a single unit. ^
Figure 3 shows a sectional side view of an alternative humidifier chamber layout that can
be used with the breathing assistance apparatus of Figure 1 in place of the prior art humidifier
chamber, with the inlet located on the side wall of the chamber.
Figure 4 shows a schematic perspective view of the chamber of Figure 2, connected to a
separate heater base unit and showing how the fins of the heater can form the tortuous path
through the upstream half of the chamber.
Figure 5 shows a schematic plan view of the chamber of Figures 2 and 4, with one
possible form of the tortuous path shown in the upstream part of the chamber.
Figure 6 shows a perspective view-of the chamber of Figure 5.
Figure 7 shows a perspective view of an alternative humidifier chamber layout, with co-
located inlet and outlet parts.
DETAILED DESCRIPTION OF THE PREFERRED EMbothMENTS
The present invention provides a humidification chamber for use with a breathing
assistance apparatus where the flow of gases to a user passes in sequence through a gases supply
device or flow driver (a blower, fan or compressor unit), the humidification chamber, a heated
delivery conduit and a patient interface, similar to that outlined in the prior art section above.
The present invention also provides a breathing assistance apparatus that includes the
humidification chamber.
The preferred form of the humidifier chamber of the present invention can be used with
the system described above, in place of the chamber 5, or the chamber could be used with any
other suitable breathing assistance apparatus.

The preferred form of the humidifier chamber will now be described with reference to
Figures 2 to 5.
Figure 2a shows a humidifier chamber 5a with an inlet port 11a and an outlet port 8a.
The chamber 5a has a base 13a and in use is connected to a bousing such as housing 10 so that a
heater plate 25 on the housing 10 heats a volume of water 6a in the chamber 5a. In the
embothment shown in Figure 2, chamber 5a has both the inlet 11a and oudet 8a located in the
roof of the chamber. However, the present invention is not limited to this configuration, and the
inlet and oudet ports 11a and 8a can be located wherever is convenient on. the chamber 5a. For
example, the inlet port can be located passing generally horizontally in through the side wall of
the chamber 5a, as shown in Figure 3. Alternatively, both the inlet and the outlet ports can be
located next to each other, as shown in Figure 7 in the side wall of the chamber. These
configurations can-be advantageous in certain circumstances. For example, they lend themselves
more readily to a slide-on system. It should also be noted that in one of the embothments
shown, the base 13a is a separate unit fiom the finned heater 12a. This potentially allows the
finned heater and fh.e base 13a to be separately heated. However, as shown in figure 2b, the base
13a and the heater 12a can be single unit if required. This second configuration (single base) can
be preferable if the chamber 5a. is being used with an existing heater or base unit, as it allows both
the heater 12a and the base 13a to be heated by the same heater plate 25. However, as noted
above, the internal heater 12a and the base 13a can be separate items, heated separately in other
configurations. For example, the chamber 5a can be used with a gases supply device that has a
split heater plate».with each part of the.split heater plate separately powered to separately heat the
separate internal heater 12a and base 13a. Alternatively, one or both of the internal heater 12a
and the base 13a could be configured as resistance heaters, connected to an electrical circuit ot
circuits to heat them either together, or separately.
In the preferred embothment, the chamber 5a is circular when viewed from above (plan
view), as shown in Figure 5. The chamber 5a is divided into two parts or halves, the two halves
appearing semicircular when viewed from above. The two halves can be characterised as an
'upstream' half or upstream sub-chamber 20, and a 'downstream' half or downstream sub-
chamber 21. In use, gas fiom the blower enters the upstream sub-chamber 20 via inlet port 11a,
passes through the upstream sub-chamber 20 and the downstream sub-chamber 21, exiting the
chamber 5a via outlet port 8a, which is located in the downstream half. The structure of the two
sub-chambers 20, 21 of the preferred embothment will now be described.

Referring to Figures 3,4 and 5, the downstream sub-chamber 21 is defined by the outer
wall of the chamber 5a, a semi-circular heater base 13a, and a substantially vertical separating
partition or wall 22 between the upstream and downstream sub-chambers. The wall 22 includes
an aperture 15 that allows gases to pass from the upstream sub-chamber 20 into the downstream
sub-chamber 21. In the preferred embothment, the aperture 15 is located in the wall above the
upper level of the water 6a, so that only gases can pass from the upstream sub-chamber 20 to the
downstream chamber 21 in use. In use, the downstream sub-chamber 21 contains the volume of
water 6a that is heated by the heater base 13a to humidify gases passing through the downstream
sub-chamber 21. The aperture 15 is shown as a notch-shaped opening in the upper portion of
the partition 22, but can be sized and positioned according to a users requirements. For example,
the aperture could run the full width of the humidifier chamber if required, and be formed by
making the partition 22 the same width as the chamber, but having less height than the chamber,
so that when in position, there is a gap between the internal upper surface and the upper portion
of the sides of the chamber, and the top edge ofthe partition, this gap defining the aperture 15.
Alternatively, the partition or wall 22 could fit exacdy in the chamber, but have an aperture
machined through it, of a suitable size and at a suitable location.
The upstream sub-chamber 20 is defined by the separating wall 22, the wall of the
chamber 5a, and a semicircular base 23. The upstream sub-chamber 20 contains an internal
heater or finned heater 12a, which in the preferred embothment is formed as one item with the
base 23. The heater 12a is located in the chamber 5a so diat part of the heater is immediately
adjacent the inlet port 1 la, so that gases entering the chamber immediately contact the heater
12a. The preferred embothment of the heater 12a is configured and shaped so that gases
entering the chamber must pass over, between, and around the fins 24. That is, the fins 24 act as
a tortuous path that runs between the inlet 11a and the downstream sub-chamber 21. This
ensures that gases passing through the upstream half of the chamber 5a have maximum exposure
to the fins 24 of the heater 12a and substantially the entire volume of gases passing into the
chamber 5a becomes heated. The preferred embothment of the heater 12a is a series of parallel
vertical fins 24 aligned perpendicular to the shortest or most direct path between the inlet 11a
and the outlet 8a or aperture 15. However, in other embothments the fins may have other
orientations, such as horizontal depending on the location of the inlet to the chamber. In the
preferred embothment, each of the fins 24 is offset from adjacent or neighbouring fins to create a
series of spaces on alternating sides of the fins 24, these spaces forming a path for the gases
between the inlet 11a and the aperture 15. This arrangement is shown schematically in Figures 4

and 5. In older to inctease efficiency, the fins 24 ate sized and shaped so that they contact the
wall and roof of the chamber 5a, except for the side spaces. This ensures that the majority of the
gases will pass along the tortuous path, and will not follow a direct route between inlet and
aperture. If requited, the contact between fins and wall can be reinforced by using a sealant or
such as silicone or similars t Alternatively, the spaces can be formed both on alternating sides and
also at the top and at the base of the fins 24. The tortuous path ensures that there is no direct
path that the gases can take between the inlet 11a and the aperture 15, and ensures that
substantially the entice volume of gases passing through the upstream sub-chamber 20 is heated
to an optimal temperature.
The upstream sub-chamber 20 is separated from the downstream sub-chamber 21 by the
partition or wall 22, which in the preferred embothment is an integral part of the heater 12a, and
forms a final fin of the heater 12a. It should be noted that the partition wall 22 could be a
separate item to the heater 12a if required. The final fin or wall 22 is sealed to the sides and base
of the chamber 5a, ensuring that the volume of water in the downstream sub-chamber 21
remains in the downstream half of the chamber 5a, and has no contact with the heater 12a
(except for the wall or final fin 22). Therefore, the gases remain dry as they pass through the
upstream sub-chamber 20.
It should be noted that the spacing between the fins 24 in the preferred embothment is
such tihat the gases can pass freely over and around the fins 24 without the system requiring
significant additional pressure fiom the blower to force the gases through the chamber 5a. The
aperture. 15 is also sized so that, it does not create a bottleneck or cause back pressure in the
system.
The heated gases enter the downstream half of the chamber 5a via the aperture 15 in the
wall 22. As outlined above, the downstream sub-chamber 21 contains a volume of water 6a,
which is heated by contact with the heater base 13a. As the heated gases pass through the space
above the volume of water 6a, they become humidified- The heated humidified gases then pass
out of the humidifier chamber 5a via the outlet port 8a into a delivery conduit, such as delivery
conduit 3 previously described. It is preferred that the chamber 5a is used with a heated delivery
conduit, so as to prevent the water vapour in the heated humidified gases from condensing-
In the preferred embothment, and as described above, the heater base 13a is separate
heater from the finned heater 12a, with the two units connected to form a sealed base for the
chamber 5a. Keeping the heaters 12a and 13a as separate units has the advantage as they can be
independently controlled. However, if required, the heater 12a and the heater base 13a can be

manufactured as a single item, allowing it to be powered and controlled from a single power
source.
By heating the gases within the chamber immediately before they contact the humidified
water vapour in the downstream sub-chamber 21, the gases are heated to an optimum
temperature. This allows them to become fully saturated when they contact the water vapour.
The gases do not have an opportunity to cool before exposure to the water vapour.
By using a tortuous path when heating the gases, substantially the whole of the gas
volume becomes heated. The tortuous path layout makes it difficult for the gases to form an
insulating cushion, e.g. next to a heated conduit wall, which can occur in linear flow due to gases
shearing effects. This gases shearing effect allows the greater part of the gas volume to pass
through the heated area without being heated to the required temperature.
Preheating the air immediately prior to humidification also ensures that the humidified
gases exiting the chamber via outlet 8a remains at the optimum required temperature. This helps
ensure that the gases are delivered to the patient at the required temperature.
The heater plate or heater plates (as described above) are controlled by a control unit
{generally indicated as 26 in Figure 1) in the humidification unit 25. The control unit is generally
a microcontroller, which is connected to at least one sensor, and can potentially be connected to
a number of sensors. For example, a chamber exit sensor 27 may be provided, or a patient
sensor 28 which is located at the patient end of tube/conduit 7 or located on or in the interface
2. Alternatively, both a chamber exit sensor 27 and a patient end sensor 28 may be provided. A
chamber inlet sensor 29 could also be provided. Any combination of these sensors 27, 28, 29
could also be provided, each one connected to the control unit 26. It should be noted that the
three locations specified above ate the preferred locations. However, other locations for the
sensors can be used as necessary. For example, it might be advantageous to measure the
temperature or humidity at the aperture 15.
The sensor or sensors measure parameters at their location. The data from the sensor or
sensors is fed back into the control unit, so that heater plate temperatures can be controlled and
constantly changed in a real time manner to provide predetermined ot maximum temperature or
humidity of the gases at these various points in the whole system. Therefore, any or all of the
sensors 27, 28 and 29 may be either or both of temperature sensors or humidity sensors (either
absolute humidity or relative humidity sensors).
Tests were conducted to determine whether a humidification chamber with internal
heating of the present invention would provide a higher absolute humidity to patients compared

to a standard chamber. The hutnidification chamber with internal heating ("heating chamber")
used in the test was of the type described in Figure 2b. A standard chamber such as the Fisher &
Paykel Healthcare Limited HC345 chamber was used.
Test results are shown in Tables 1 to 3. These results indicate that the heated chamber of
the present invention provided a higher chamber exit temperature compared to the standard
chamber (Table 1, below). In general, the heated chamber provided an exit temperature of
approximately 10°C greater then the standard chamber at the same gases pressure and heater
plate setting. Heater plate settings of either 3 or 4 were used. Each of these settings related to a
particular controEed temperature o£ the heater plate. The end of tube temperature, that is, at the
patient end 2 of the conduit 3, was higher for the heated chamber.

Table 2 (below) shows absolute humidity outputs. The absolute humidity output of the
heated chamber was about 10% above the standard chamber. Table 2 shows that the heated
chamber allows the user of a higher heater plate setting (4 as opposed to 3) without the
introduction of condensation in the conduit Therefore, the absolute humidity of the gases
supplied to the patient was higher for the heated chamber.

CLAIMS:
1. A respiratory humidifier chamber for use with a breathing assistance apparatus,
comprising:
a watertight vessel having an inlet adapted for receiving gases from said breathing
assistance apparatus, and a separate oudet through which heated humidified gases exit said vessel
for delivery to a patient,
a partition, dividing said vessel into an upstream sub-chamber and a downstream sub-
chamber, said sub-chambers sealed from each other by said partition except for an aperture, said
aperture passing through said partition and allowing gaseous communication between said sub-
chambers,
said downstream sub-chamber including a heater base, adapted to heat a volume of water
contained within said downstream sub-chamber in use, said aperture, said inlet and said outlet
located above said volume of water in use,
said upstream sub-chamber containing an internal heater, adapted to heat gases passing
through said upstream sub-chamber from said inlet to said aperture, at least part of said internal
heater located immediately adjacent said aperture.
2. A respiratory humidifier chamber as claimed in claim 1 wherein said internal heater is
configured so as to provide a tortuous path for said gases as they pass through said upstream
sub-chamber.
3. A respiratory humidifier chamber as claimed in claim 1 or 2 wherein said internal heater is
a fin heater having a plurality of fins.
4. A respiratory humidifier chamber as claimed in claim 3 wherein the fins of said fin heater
are aligned substantially perpendicular to a direct flow path between said inlet and said aperture.
5. A respiratory humidifier chamber as claimed in claim 3 or 4 wherein said tortuous path is
formed by offsetting adjacent ones of said fins.
6. A respiratory humidifier chamber as claimed in any one of claims 1 to 5 wherein said
heater base and said internal heater are separate.

7. A respiratory humidifier chamber as claimed in any one of claims 1 to 5 wherein said
heater base and said internal heater are formed as a single heater, adapted to be heated from a
single source.
8. A respiratory humidifier chamber as claimed in claim 6 or 7 wherein said chamber
includes at least one sensor, adapted to provide data to a remotely located controller.
9. A respiratory humidifier chamber as claimed in claim 8 wherein said at least one sensor is
located at said oudet.
10. A respiratory humidifier chamber as claimed in claim 8 wherein said at least one sensor is
located at said inlet.
11. A respiratory humidifier chamber as claimed in claim 8 wherein said chamber includes a
first sensor located at said inlet and a second sensor located at said oudet.
12. A respiratory humidifier chamber as claimed in any one of claims 8 to 11 wherein said
sensors are either temperature sensors or humidity sensors, or both.
13. A respiratory humidifier chamber as claimed in claim 12 wherein said sensors are at least
humidity sensors adapted to sense either relative or absolute humidity sensors.
14. A breathing assistance apparatus for delivery of respiratory gases to a patient comprising:
a gases supply device, adapted to provide a flow of pressurised gases through said system,
a humidifier chamber, having an inlet and a separate oudet, said chamber adapted to
receive said flow of gases from said gases supply device via said inlet, and provide a supply of
heated humidified gases through said oudet,
a delivery conduit, adapted to connect to said oudet and receive said heated humidified
gases,
a patient delivery interface, adapted to receive said gases from said delivery conduit and
deliver these to said patient,

said humidifier chamber comprising a watertight vessel that includes a partition, dividing
said vessel into an upstream sub-chamber and a downstream sub-chamber, said sub-chambers
sealed from each other except for an aperture passing through said partition, said aperture
allowing gaseous communication between said sub-chambers,
said downstream sub-chamber including a heater base, adapted to heat a volume of water
contained within said downstream sub-chamber in use, said aperture, said inlet and said outlet
located above said volume of water in use,
said upstream sub-chamber containing an internal heater, adapted to heat gases passing
through said upstream sub-chamber from said inlet to said aperture, at least part of said internal
heater located immediately adjacent said aperture.
15. A breathing assistance apparatus as claimed in claim 14 wherein said internal heater is
configured so as to provide a tortuous path for said gases as they pass through said upstream
sub-chamber.
16. A breathing assistance apparatus as claimed in claim 14 or 15 wherein said internal heater
is a fin heater having a plurality of fins.
17. A breathing assistance apparatus as claimed in claim 16 wherein the fins of said fin heater
are aligned substantially perpendicular to a direct flow path between said inlet and said aperture.
18. A breathing assistance apparatus as claimed in claim 16 or 17 wherein said tortuous path
is formed by offsetting adjacent ones of said fins.
19. A breathing assistance apparatus as claimed in any one of claims 14 to 18 wherein said
heater base and said internal heater are separate.
20. A breathing assistance apparatus as claimed in any one of claims 14 to 18 wherein said
heater base and said internal heater are formed as a single heater, adapted to be heated from a
single source.
21. A breathing assistance apparatus as claimed in any one of claims 14 to 20 wherein said
breathing assistance apparatus also includes a sensor located near said outlet to said chamber.

22. A breathing assistance apparatus as claimed in any one of claims 14 to 20 wherein said
breathing assistance apparatus also includes a sensor located near said inlet to said chamber.
23. A breathing assistance apparatus as claimed in any one of claims 14 to 20 wherein said
breathing assistance apparatus also includes a first sensor located at or near said inlet to said
chamber and a second sensor located at or near said oudet to said chamber.
24. A breathing assistance apparatus as claimed in any one of claims 21 to 23 wherein said
sensors are either temperature sensors or humidity sensors, or both.
25. A breathing assistance apparatus as claimed in claim 24 wherein said sensors are at least
humidity sensors adapted to sense either relative or absolute humidity.
26. A breathing assistance apparatus as claimed in any one of claims 21 to 25 -wherein said
breathing assistance apparatus also includes a heater plate adapted to heat said heater base and
said internal heater, said breathing assistance apparatus also including a control unit adapted to
receive data from said sensors and to adjust the power to said heater plate so that the
temperature of said heater plate is constandy changed in a real time manner to provide
predetermined or maximum temperature or humidity of the gases at various points in the
breathing assistance apparatus.
27. A breathing assistance apparatus as claimed in claim 26 wherein said heater plate is a
single heat source and heats said heater base and said internal heater together.
28. A breathing assistance apparatus as claimed in claim 26 wherein said heater plate is
adapted to heat said heater base and said internal heater separately.

A respiratory humidifier chamber for use with a breathing assistance apparatus is
described. The chamber comprises a watertight vessel having an inlet for receiving gases from
the breathing assistance apparatus, and an outlet through which heated humidified gases exit the
vessel for delivery to a patient. The chamber has a partition which divides the chamber into
upstream and downstream sub-chambers. The sub-chambers are separated by the partition
except for an aperture which passes through the partition and allows gaseous communication
between the sub-chambers. The downstream sub-chamber includes a heater base which heats a
volume of water contained within it. The aperture is located above the volume of water. The
upstream sub-chamber contains an internal heater which heats gases passing through it from the
inlet to the aperture. At least part of the internal heater is located immediately adjacent the
aperture.