BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a gases supply and gases humidification apparatus that can
be disinfected and reused for different patients. The invention also relates to a method for
disinfecting apparatus parts that extend the life of these parts for use by a single patient.
Summary of the Prior Art
A number of methods are known in the art for assisting a patient's breathing.
Continuous Positive Airway Pressure (CPAP) involves the administration of air under
pressure to a patient, usually by a nasal mask. It 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 its collapse. Treatment of OSA with nasal CPAP has proven to be both
effective and safe, but CPAP is difficult to use and the majority of patients experience
significant side effects, particularly in the early stages of treatment.
CPAP is also commonly used for patients with a variety of respiratory illnesses,
including Chronic Obstructive Pulmonary Disease (COPD).
Upper airway symptoms adversely affect treatment with CPAP. Mucosal drying is
uncomfortable and may awaken patients during the night Rebound nasal congestion
commonly occurs during the following day, simulating a viral infection. If untreated,
upper airway symptoms adversely affect rates of CPAP use.
Increases in nasal resistance may affect the level of CPAP treatment delivered to
the pharynx, and reduce the effectiveness of treatment. An individual pressure is
determined tor each patient using CPAP and this pressure is set at the patient interface. '
Changes in nasal resistance affect pressure delivered to the pharynx and if the changes are
of sufficient magnitude there may be recurrence of snoring or airway collapse or reduce the
level of pressure applied to the lungs. Such symptoms can also occur in a hospital
environment where a patient is on a respirator. Typically in such situations the patient is
intubated. Therefore the throat tissue may become irritated and inflamed causing both
distress to the patient and possible further respiratory problems.

A number of methods may be employed to treat such upper airway symptoms,
including pharmacological agents to reduce nasal disease, or heating the bedroom. One
most commonly employed method is humidification of the inspired air using an in line
humidifier. Two types of humidifier are currently used. Cold pass-over humidifiers rely
on hurrudifying the air through exposure to a large surface area of water. While they are
cheap, the humidity output is low at high flows, typically 2 to 4 mg\L absolute humidity at
flows above 25L/min. The output is insufficient to prevent mucosal drying. Heated water
bath humidifiers are more efficient, and produce high levels of humidity even at high flow
rates. They are effective at preventing upper airway mucosal drying, prevent increases in
nasal resistance, and are the most reliable means of treating upper airway symptoms.
Oxygen is the most common drug prescribed to hospitalized patients. The delivery
of oxygen via nasal cannula or facemask is of benefit to a patient complaining of
breathlessness. By increasing the fraction of inspired oxygen, oxygen therapy reduces the
effort to breathe and can correct resulting hypoxia (a low level of oxygen in the tissues).
The duration of the therapy depends on the underlying illness. For example,
postoperative patients may only receive oxygen while recovering from surgery while
patients with COPD require oxygen 16 to 18 hours per day.
Currently greater than 16 million adults are afflicted with COPD, an umbrella term
that describes a group of lung diseases characterized by irreversible airflow limitation that
is associated mainly with emphysema and chronic bronchitis, most commonly caused by
smoking over several decades. When airway limitation is moderately advanced, it
manifests as perpetual breathlessness, without physical exertion. Situations such as a
tracheobronchial infection, heart failure and also environmental exposure can incite an
exacerbation of COPD that requires hospitalization until the acute breathlessness is under
control. During an acute exacerbation of COPD, the patient experiences an increase in
difficulty of breathing (dyspnea), hypoxia, and increase in sputum volume and purul.en.ce
and increased coughing.
Oxygen therapy provides enormous benefit to patients with an acute exacerbation
of COPD who are hypoxic, by decreasing the risk of vital organ failure and reducing
dyspnea. The major complication associated with oxygen therapy is hypercapnia (an
elevation in blood carbon dioxide levels) and subsequent respiratory failure. Therefore, the
dose of oxygen administered can be critical and must be precisely known.

To accurately control the oxygen dose given to a patient, the oxygen-enriched gas
must exceed the patient's peak inspiratory flow to prevent the entrainment of room air and
dilution of the oxygen. To achieve this, flows of greater than 20 L/min are common. Such
flows of dry gases cause dehydration and inflammation of the nasal passages and airways
if delivered by nasal cannula. To avoid this occurrence, a heated humidifier is used.
The majority of systems that are used for oxygen therapy or merely delivery of
gases to a patient consists of a gases supply, a humidifier and conduit. Interfaces include
facemasks, oral mouthpieces, tracheostomy inlets and nasal cannula, the latter having the
advantage of being more comfortable and acceptable than a facemask.
A group of patients who would benefit from humidification therapy are patients
who have mucociliary clearance deficiencies. These patients often have purulent mucus
and are susceptible to infections from pathogens.
Heated humidified air with an abundance of water particles is an ideal medium to
harbour disease carrying pathogens. Consequently, considerable design expertise has been
required to provide the market with active pass-over humidifiers that deliver water
molecules, in gas phase only, so that it is not possible for disease pathogens to be carried in
air to the patient. Water that condenses on the inner surfaces of the breathing circuit or
conduit at the end of a treatment session may harbour pathogens that would be delivered to
the patient next time they use the device. This is particularly the case with humidification
therapies where patients are receiving body temperature fully saturated air.
In hospital environments or similar it is often not possible for gases supply devices,
such as devices that deliver CPAP and include a humidifier, to be used by multiple
patients. If devices were to be used in this manner all parts, from the humidification
. chamber to and including the patient interface, must be disposed of or cleaned to a high
standard of disinfection in between use by different patients. Often CPAP devices and
humidifiers are provided in an integrated unit, such as the Sleepstyle™ 600 series CPAP
device of Fisher & Paykel Healthcare Limited. This CPAP device is predominantly used
for home use by an individual. This device has internal tubing from the outlet of the
humidification chamber that is difficult to disinfect. As these devices are difficult to
disinfect they are often not used in settings such as hospitals or clinics where multiple
patients will use the device.

In the home use situation when oxygen therapy and CPAP devices are used by a
single patient the lifespan of the breathing tube and patient interface is determined by the
mechanical lifespan of the parts and the build up of microbial pathogens on the breathing
gases path of these parts. Often it is hard to lower microbial contamination on the
breathing gas surfaces of these parts.
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 breathing assistance
apparatus adapted to deliver humidified gases to a patient comprising:
a housing,
a gases supply within said housing,
a gases outlet in said housing in fluid connection with said gases supply and
adapted to make fluid connection with an inlet of a humidifier in order to supply gases to
said humidifier,
an outlet in said humidifier,
a patient outlet on said housing,
a gases return in said housing, adapted to make fluid connection with said
humidifier outlet in order to receive humidified gases from said humidifier and provide
humidified gases to said patient outlet, said patient outlet being in fluid connection with or
adapted to make fluid connection with a breathing conduit for delivery of humidified gases
to a patient,
a heated gases conduit including a heating element adapted for connection between
said gases outlet and said patient outlet.
Preferably said gases return has a temperature sensor within that senses the
temperature of said gases flowing through said gases return.
Preferably said breathing assistance apparatus further comprises a filter connectable
to said gases return to filter gases exiting said gases return.
In a second aspect the present invention consists in a method of disinfecting a
breathing assistance apparatus, said breathing assistance apparatus including a gases
supply capable of supplying a flow of gases at a predetermined pressure to a patient and

capable of providing power to conduits supplying gases to said patient, said method
comprising the steps of:
connecting a heated gases conduit, including a heating element, between an outlet
of said gases supply and an outlet to said patient,
said gases supply providing a predetermined flow of gases to said disinfection
conduit over a predetermined period of time,
said gases supply including a controller to supply power to said heating element
and said controller causing the heating element to heat the heated gases conduit up to a
predetermined temperature.
Preferably said predetennined period of time is between 2 and 60 minutes.
Preferably said predetermined period of time is approximately 30 minutes.
Preferably said predetermined temperature is between 60 and 90 degrees Celsius.
Preferably said predetermined temperature is approximately 80 degrees Celsius.
Preferably said predetermined circulating flow is between 1 and 50 litres per
minute.
Preferably said predetermined circulating flow is approximately 10 litres per
minute.
In a third aspect the present invention consists in a method of disinfecting at least
one of a breathing conduit and patient interface, said breathing conduit and said patient
interface being connected to a breathing assistance apparatus including a gases supply
capable of supplying a flow of gases at a predetermined pressure or flow to a patient and
capable of providing power to said breathing conduit supplying gases to said patient, said
breathing assistance apparatus including a humidifying chamber and heater capable of
heating water within said chamber and said breathing conduit including a heating element,
said method comprising the steps of:
removing water from said chamber,
said gases supply providing a predetermined flow of gases to said chamber and at
least one of said breathing conduit and patient interface over a predetermined period of
time,
said gases supply including a controller to supply power to said heater and said
heating element, said controller causing the said heater and said heating element to heat
said gases supplied to said at least one of said breathing conduit and patient interface to a

predetermined temperature to dry and disinfect said at least one of said breathing conduit
and patient interface to prevent accumulation of bacteria in said at least one of said
breathing conduit and patient interface.
Preferably said predetermined period of time is between 30 and 120 minutes.
Preferably said predetermined period of time is approximately 90 minutes.
Preferably said predetermined temperature is between 40°C and 75°C.
Preferably said predetermined temperature is 40°C.
Preferably said method includes the step of placing a cap on the distal end of said
breathing conduit at a point where said patient interface is connected in normal use.
Preferably said method includes the step of placing said patient interface in an
enclosure.
To those skilled in the art to which the invention relates, many changes in
construction and widely differing embodiments 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.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
A preferred, form of the present invention will now be described with reference to
the accompanying drawings.
Figure 1 is an illustration of the breathing assistance apparatus that may utilise the
method of disinfecting of the present invention.
Figure 2 is an exploded view of an elbow connection conduit of the breathing
assistance apparatus of the present invention.
Figure 3 is a front view of a gases supply and humidifier apparatus with a hot gases
tube (disinfection conduit) and a filter connection of the present invention.

Figure 4 is a front view of the gases supply and humidifier apparatus of Figure 3
without the disinfection conduit and ready for use by a patient
Figure 5 is a perspective view of a breathing assistance apparatus with a filter over
a gases return of the breathing assistance apparatus.
Figure 6 is a close up view of the gases return with the filter, in particular, the filter
cover and a projection that extends within the gases return.
Figure 7 is a front view of the gases supply and humidifier apparatus showing the
gases return and the temperature sensor residing within it
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides a breathing assistance apparatus that has a
convenient and effective method of cleaning internal conduits inside the apparatus. As
shown in Figure 1, the flow of gases passes in sequence through a gases supply means or
flow driver (such as, a blower, fan or compressor), humidification chamber, heated
delivery circuit and patient interface.
Further the present invention also provides a method of disinfecting a heated
breathing conduit and a patient interface.
Gases are passed to the patient by way of a patient interface 2. The patient
interface used with the apparatus of the present invention may be a full-face mask, nasal
mask, nasal cannula, oral mouthpiece or tracheostomy connection,- but the description
below and figures disclose the use of a nasal cannula.
With reference to Figure 1 the breathing assistance apparatus of the present
invention is shown in which a patient 1 is receiving humidified and pressurised gases
through a nasal cannula 2. The cannula 2 is connected to a gases transportation pathway or
inspiratory conduit 3 that in turn is connected to an integrated gases supply (blower) and
humidifying device 4 (including a humidification chamber 5). In the preferred
embodiment of the blower-humidifying device 4, the gases supply or blower is combined
in one housing with the humidifier and humidification chamber. The humidification
chamber 5 extends out from the housing 10 and is capable in use of being removed and
replaced (by a slide on movement, such as that described in WO04024429 of Fisher &
Paykel Healthcare Limited, the contents of which are incorporated by reference) by the
patient or other user. Also, the gases supply outlet port 11 (see Figure 2) that feeds the
inlet to the humidification chamber 5 is internal within the housing 10. It must be

appreciated that the embodiment described above in relation to the housing and the figures
merely illustrates one form of the housing of the integrated gases' supply and humidifying
device.
The inspiratory conduit 3 (see Figure 1) is connected to the outlet 8 of a
humidification chamber 5 that contains a volume of water 6. Inspiratory conduit 3
preferably contains heating means or heater wires 7 that heat the walls of the conduit to
reduce condensation of humidified gases within the conduit and the patient interface (e.g.
nasal' cannula 2) such the conduit as described in WO04026382 of Fisher & Paykel
Healthcare Limited, the contents of which are incorporated by reference.
The humidification chamber 5 is preferably formed from a plastics material and
may have a highly heat conductive base (for example an duminiurn base) that is in direct
contact with a heater plate 25. The device 4 is provided with control means or an
electronic controller that may comprise a microprocessor based controller executing
computer software commands stored in associated memory. The controller receives input
from sources such as user input means or dial (not shown) through which a user of the
device 4 may, for example, set a predetermined required value (preset value) of humidity
or temperature of the gases supplied to patient 1.
In response to the user set humidity or temperature value input via dial (or burtons)
and other possible inputs such as internal sensors that sense gases flow or temperature, or
by parameters calculated in the controller, the controller determines when (or to what
level) to energise heater plate to heat the water 6 within humidification chamber 5. As the
volume of water 6 within humidification chamber 5 is heated, water vapour begins to fill
the volume of the chamber above the water's surface and is passed out of the
humidification chamber outlet 8 with the flow of gases (for example air) provided from a
blower part of the device that has entered the device 4 through an inlet 9 on the back of the
device 4.
The gases supply within the device 4 is preferably a variable speed pump or fan
that draws air or other gases through the blower inlet 9. The speed of variable speed pump
or fan is preferably controlled by the control means or electronic controller described
above in response to inputs entered into the device 4 by the user.

Disinfection of the Device
A partially exploded view of a gases supply and humidification device 4 is shown
in Figure 2. The device 4 has an elbowed connection conduit 12 that has an inlet end 13,
which is the gases return in the housing 4, and an outlet end 8, that is the patient outlet of
the housing 4. The conduit 12 is provided to receive humidified gases from the
humidification chamber 5 and as such the inlet end 13 is connected to the outlet 15 of the
humidification chamber. The humidified gases are directed from the conduit's outlet end 8
into the breathing conduit 3 (see Figure 1) for delivery to a patient. It is preferred that the
elbowed connection conduit 12 is permanently fixed in place in the housing 4.
There is a requirement for multiple users to use these devices as they will be used
in hospitals, sleep laboratories or leased by home care companies and hospitals for short
term home users.
To use such a gases supply and humidification device 4 on multiple patients the
elbow conduit 12 integrated into the device must have a high level disinfection process
carried out between different patients using it. For ease of use, even if the elbow conduit
12 can be removed, and to avoid dismantling and potential damage to the internal parts of
the device 4 it is preferred that the elbow is disinfected in situ. This is because it is often
impractical to remove the elbow, as it may have electrical connectors and the like, and
clean it and reconnect it. Furthermore, the high labour content and skill level required
would make removing the elbow an unreliable cleaning method and may make the device
more unreliable.
Other parts of the device 4, such as the gas supply outlet 11, may also need high
level disinfection between patients and could benefit from the present invention.
Currently high level disinfection is performed either by thermal or chemical
process. Thermal disinfection is normally carried out by submersion in hot water or steam
and chemical disinfection by submersion in instrument grade disinfectants. These
processes have disadvantages for high level disinfection of devices such as the gases
supply and humidification device 4 of the present invention as it cannot be submersed;
steam sterilized or easily chemically disinfected.
A further option for thermal disinfection is hot dry air. The present invention is the
supply of a heated gases tube (disinfection conduit) for use with a device 4 to allow in
particular for disinfection of the elbow conduit 12. A disinfection conduit 14 is shown in

Figure 3. To disinfect the elbow conduit 12 a first end 17 of the disinfection conduit 14 is
connected to the gases supply outlet 11 and a second end 18 to the outlet end 8 of the
elbow conduit 12. The disinfection conduit 14 preferably has a heating element 19 within,
through out or about the walls of the disinfection conduit 14. For example, the disinfection
conduit 14 may be a section of tubing as described in WO04026382 of Fisher & Paykel^
Healthcare Limited with appropriate connectors on both ends of the tube to enable
connection to the elbow conduit 12 and the gases supply outlet 11.
It is preferred that a removable exhaust gases filter 20 is placed on the inlet end 13
of the elbow conduit 12. This filter 20 is shown in more detail in Figures 5 and 6. In
Figure 5, a filter housing 21 can be placed about the inlet end 13. The filter housing 21 is
preferably made of a plastics material and can be simply removably attached to the inlet
end 13, and remains on the end 13 by a friction fit. A preferably circular piece of filter
material (not shown in this figure), sits inside the filter housing 21 and therefore occludes
the inlet end 13, such that when in use with the disinfection conduit as described and
shown with reference to Figure 3, gases exiting the inlet end 13 (patient return 13) are
filtered before they exit to the ambient surroundings.
Referring to Figure 6, the filter housing 21 is shown in further detail. Preferably a
projection 22 is provided with the filter 20 and housing 21. This tubular projection 22 sits
within the inlet end 13 and the filter housing 21 sits about the projection 22 and over the
end of the inlet 13. The projection 22 has the purpose of increasing the gases velocity at
the point where heated gases are exiting the inlet end 13 (when the disinfection conduit 14
is in place as described above and in use). This has the effect of maximising the exhaust
"temperature of the exiting gases and minimising the temperature drop at the exit point
This ensures there is a high level of disinfection throughout the entire elbow conduit 12. In
use; the heated gases flow around the spherical end 23 of the projection 22 down the sides
of the tubular inlet end (in the direction of arrows A) through apertures (not shown) in the
projection 22 through the filter material 20 and past the filter housing 21 into the ambient
surroundings.
When the disinfection conduit 14 is connected between the gases supply outlet 11
and the patient outlet 8 as described above, the device 4 may be put into a cleaning mode
whereby dry gases, such as air, are circulated through the disinfection conduit 14 and
elbow conduit 12. It is preferable that the circulated gases are heated by the disinfection

conduit to a temperature of 80°C. However, a temperature between 60°C and -90°C may be
suitable.
The connectors at both ends 17, 18 of the disinfection conduit 14 preferably have
pneumatic fittings. Preferably the second end 18 of the disinfection conduit 14 has an
electrical connection such that the heating element 19 within the conduit 14 can be
supplied from the device 4 with power. In other forms of the device both ends 17, 18 may
have electrical and pneumatic connections.
The device 4, and in particular, the controllers within the device 4 that control the
heating of the heater plate as described above, is capable of controlling the temperature of
the heating element 19.
The device 4 preferably has a setting that causes the controllers to provide a flow of
gases, for example, between 1 and 50 litres per minute, to the disinfection conduit 14 and
simultaneously provide, power to the heating element 19, such that the gases circulating
through the conduit 14 increase in temperature to 80°C. The controller then maintains the
power to the heating element 19 mamtaining a predetermined temperature inside the
conduit 12 for a period of time, preferably 20 minutes, in order for the heated dry gases to
disinfect the elbow conduit 12.
Therefore in use, after a patient has used the device 4 of the present invention, and
before the next patient uses it, the patient, hospital staff or home care supplier can connect
the disinfection conduit 14 to the device 4, as described above, and put the device 4 into a
cleaning mode. As an example, a person might put the device into a cleaning mode by
activating a button on the device that causes the controllers to provide power to the heating
element and gases to the disinfection conduit at a predetermined temperature over a set
period of time. In the preferred method of disinfecting the device, it is preferred that the
surface temperatures inside the elbow conduit reaches a minimum of 80°C for a time
period of 20 minutes and the flow provided for circulation through the elbow conduit is
approximately 10 litres per minute. However, other appropriate circulating flows between
1 and 50 litres per minute and other appropriate time periods and temperatures may be
used.
In the preferred form of the present invention the elbow conduit 12 preferably has a
temperature sensor 24 within it, for example, as shown in Figure 7. However, in other
forms of the invention, the elbow conduit may not have such a sensor.

In tibe preferred form this sensor measures the temperature of gases travelling
through the conduit 12. In particular, in the preferred form of the method of disinfecting,
at the start of the disinfection process, the controller or electronics within the device 4
performs some checks to ensure the disinfection conduit is correctly connected to the
device 4. • Firstly, a check is performed to determine that there is a heated gases flow
through the elbow conduit 12. When the gas flow supplied by the device 4 and heater
element 19 of the disinfection conduit 14 are both turned on, the heated gases flow is
measured by the internal temperature sensor 24 .inside the elbow conduit 12. After a
predetermined period the heater element 19 is turned off with the gases flow of the device
4 left on. After a further predetermined period, the temperature inside the elbow conduit
12 is again measured by the temperature sensor 24. It is expected that the temperature will
have dropped between measurements. This proves there is a fluid connection of gases
supply connecting the flow source to the elbow conduit 12.
If a rise in temperature and a fall in temperature between measurements is not
detected by the sensor 24 an error alarm will be indicated on or audibly relayed by the
device, indicating the disinfection conduit 14 is not connected to the device 4 correctly.
Knowing the gases flow, ambient temperature outside the device 4 (as the device 4
has an ambient air temperature sensor incorporated within it) and the time period, in which
the heating element 19 is powered, an expected temperature can be calculated for the
heating and non-heating periods described above. The expected temperature can then be
compared with the actual measured temperature from the temperature sensor. If these
match, then the checks are complete and the disinfection conduit 14 and heating element
19 are connected and working correctly. The disinfection method, cleaning mode, as
described above is then started.
In another embodiment of the present invention, the disinfection conduit may be
used on a blower and humidifying device that does not have an internal temperature sensor
inside the elbow conduit. In this embodiment a predeterrnined gases flow is caused to pass
through the disinfection conduit, and a predetermined power is applied to the heating
element within the disinfection conduit. The ambient conditions are known. The
predetermined gases flow and predetermined power applied are determined such that the
internal surface temperatures inside the elbow conduit will exceed the temperatures

required for high level disinfection for a range of ambient conditions. The predetermined
temperature and power are preferably determined from testing and the like.
The method of disinfection described above has been validated by an independent
laboratory, Toxikon Corporation of Bedford, MA, USA.
The method of disinfection as described above is automated so minimal training is
required to disinfect the elbow conduit aad it is not necessary to dismantie the gases supply
and humidification device, therefore, inadvertent damage to the internal parts of the device
is avoided.
Also, during the disinfection period the internal surface temperature of the elbow
conduit is continuously monitored so each disinfection cycle can be validated and a
disinfection completed symbol shown on the display at the completion of the process.
Alternatively, if the disinfection cycle was not validated a failed disinfection symbol can
be displayed to alert a user or operator.
Disinfection of Inspiratory Conduit and Patient Interface
In a second form of a blower-humidifying device 4 of the present invention a
method of disinfecting an inspiratory conduit 3 and/or patient interface 2 is disclosed.
Referring to Figure 1 and as detailed above, the inspiratory conduit 3 preferably has
a heating means or wires 7 within it. The wires 7 within the conduit 3 mean it can be
difficult or dangerous to clean and disinfect the conduit. Therefore, prolonged use of the
conduit by a patient results in high microbial contamination inside the conduit.
Consequently there is a danger of infection of the patient from continual use of the conduit
3. Therefore, for home use where patients are reusing the inspiratory conduit 3 and patient
interface 2 over a substantial period it is preferable to provide a method of cleaning and
disinfecting the conduit 3 and patient interface 2.
As shown in Figure 1, in the standard, configuration the blower and humidifying
device is used with a heated breathing conduit (inspiratory conduit 3) connected to the
patient outlet 8 of the device 4. The patient interface 2 is connected to the other end of the
conduit 3.
The method of disinfecting is to force dry heat through the conduit and optionally
the patient interface, to heat and dry the conduit and patient interface such that bacteria and
microbes are killed and cannot multiply in the dry conditions. After a patient has
completed their treatment (for example, each morning) the patient empties the

humidification chamber and presses a button, for example, on the device 4 thereby
activating a control sequence or algorithm. The control sequence or algorithm is preferably
stored in the controller (described above). A button on the device 4 may activate the
control sequence but other means of activating the sequence may be provided, for example,
the device may automatically activate the conduit disinfecting control sequence a
predetermined time after completion of treatment (removal of the patient interface, for
example) has been detected and the controller of the device has detected the humidification
chamber is empty. The controller then controls the heater plate 25 to maintain heat to the
humidifying chamber 5 and the blower 4 continues to supply gases to the chamber 5, such
that heated dry gases pass through the chamber 5 to the conduit 3. At the same time, the
power to the heating means or wires 7 is maintained to provide additional heat to the gases
within the conduit 3. The heating of the gases is preferably at approximately 40°C and the
exit temperature from the tube is between 40°C and 75°C. The disinfecting and heating
sequence preferably continues for between 30 and 120 minutes.
More particularly, the humidification chamber heater heats the gases until the
temperature of the gases in the return elbow (inlet end 13) reaches 40CC. The heating wires
in the heated breathing conduit heats the air passing down the conduit until a temperature
sensor at the patient end of the conduit reaches approx 50°C. .In other implementations it is
possible that this temperature may be raised to as high as 70°C.
In some forms of this method, a cap is placed on the patient end of the heated
breathing conduit 3 (in place of the patient interface 2). The cap allows the heated gases to
build up in the conduit thereby increasing the effectiveness of the disinfection process.
The purpose of the cap is to ensure that a patient is not wearing the patient interface. The
device 4 controller can deterrninethis by the different pressure and flow characteristic of
the gases when the cap is on the distal end of the conduit 3 compared to that characteristic
when the patient interface is attached to the end of the conduit 3. With a certainty that
there is no patient connected the air in the heated breathing conduit can be heated to
temperatures well above safe gas breathing temperatures which improves the efficacy of
the disinfection process.
In other forms of this method, the patient interface 2 is left in place at the distal end
of the conduit 3 and is exposed to the heated and dry gases. In further forms the patient
interface 2 during the disinfection process may be housed in a receptacle that allows

increased heat build up to occur in the patient interface, again, increasing the effectiveness
of disinfection. By putting the interface in a receptacle it can be ensured that a patient
cannot be using the interface for breathing, and the controlling device can detect there is no
patient connected, again because of the different pressure flow characteristic. The heated
breathing conduit can then be heated to temperatures well above safe gases breathing
temperatures. Again this improves the efficacy of the disinfection process.
The purpose of this disinfection process is to increase the useable life of the heated
breathing conduit by lowering microbial contamination on the inside surfaces the gases
pass over. If the heated breathing tube is not cleaned regularly, and this is difficult with an
internal heating wire, microbes can build to a level that the inside of the surfaces of the
conduit become colonised with bacteria, thereby lowering the useful life of the conduit,
making treatment more inconvenient for. the patient.
Tests were carried out on a heated breathing conduit in normal use for 2 months at
home "by patients with no disinfection process. The conduits were then tested for
contamination. The results were that contamination within the conduits had reached a
level of bacterial contamination that made the conduits unsafe for use.
Further tests were also carried out with identical heated breathing conduits used
under the same conditions for 2 months as described above. The conduits were then
processed with the dry heat disinfection method described above. The result was that
bacterial contamination was lowered (compared to the conduits that had not been treated)
to a level that the conduits could continue to be used safely.
This disinfection method by dry heat shows that bacterial contamination can be
effectively lowered to a level that the conduits could continue to be used by patients.

We Claim:
1. A breathing assistance apparatus (4) adapted to deliver humidified gases to a patient
(1) comprising:
a housing (10),
a gases supply within said housing (10),
a removable humidification chamber (5),
a gases supply oudet port (11) in said housing (10), said gases supply oudet port (11) in
fluid connection with said gases supply and adapted to in use make fluid connection with the
inlet of the humidification chamber (5) of the type that includes both an inlet and an oudet
(15), in order to supply gases to said humidification chamber (5) via said inlet,
a patient return (13) in said housing (10), adapted to make fluid connection with said
humdification chamber oudet (15) in use in order to receive humidified gases from said
humdification chamber (5),
a patient oudet (8) on said housing (10), in use in fluid connection with said patient
return (13) and also in fluid connection or adapted to make fluid connection with a breathing
conduit (3) for delivery of humidified gases to a patient (1),
an elbow conduit (12) in said housing (10) connecting said patient return (13) and said
patient oudet (8),
wherein said breathing apparatus (4) can be put in a cleaning mode, in which the
humidification chamber (5) is removed and
a controller is configured to:
control said gases supply to provide dry gases out said gases supply oudet port
(11) for transfer to said elbow conduit (12), and
provide power to heat dry gases from said gases supply output port (11) to
meet or exceed a temperature required for disinfecting said elbow conduit (12).
2. A breathing assistance apparatus (4) as claimed in claim 1 wherein said controller
provides power to heat dry gases by providing power to said patient oudet (8) to power a
heating element (19) of a conduit (14) when connected to said patient oudet (8).
3. A breathing assistance apparatus (4) as claimed in either claim 1 or claim 2 wherein the
dry gases out said gases supply oudet port (11) are transferred to the elbow conduit (12) when

a conduit (14) is connected between the gases supply oudet port (11) and said patient oudet
(8).
4. A breathing assistance apparatus (4) as claimed in any one of claims 1 to 3 wherein
said disinfection conduit (14) further includes a temperature sensor (24) adapted to sense the
temperature of gases flowing through said disinfection conduit (14) in use.
5. A breathing assistance apparatus (4) as claimed in any one of claims 1 to 4 wherein
said apparatus further includes a filter (20) connectable to said patient return (13) to filter
gases exiting said patient return (13).
6. A breadiing assistance apparatus (4) as claimed in any one of claims 1 to 5 wherein
said cleaning mode is for a predetermined period of time.
7. A breathing assistance apparatus (4) as claimed in claim 6 wherein said predetermined
period of time is between 2 and 60 minutes.
8. A breadiing assistance apparatus (4) as claimed in either claim 6 or claim 7 wherein
said predetermined period of time is approximately 30 minutes.
9. A breathing assistance apparatus (4) as claimed in any one of claims 1 to 8 wherein
said cleaning mode is adapted to heat the gases to a predetermined temperature.
10. A breathing assistance apparatus (4) as claimed in claim 9 wherein said predetermined
temperature is between 60 and 90 degrees Celsius.
11. A breadiing assistance apparatus (4) as claimed in either claim 9 or claim 10 wherein
said predetermined temperature is approximately 80 degrees Celsius.
12. A breathing assistance apparatus (4) as claimed in any one of claims 1 to 11 wherein
said cleaning mode is adapted to flow dry gases through the elbow conduit at a predetermined
flowrate.

13. A breathing assistance apparatus (4) as claimed in claim 12 wherein said predetermined
circulating flow is between 1 and 50 litres per minute.
14. A breathing assistance apparatus (4) as claimed in either claim 12 or claim 13 wherein
said predetermined circulating flow is approximately 10 litres per minute.