U.S. patent application number 16/134790 was filed with the patent office on 2019-04-04 for system, apparatus and method for supplying gases.
The applicant listed for this patent is Fisher & Paykel Healthcare Limited. Invention is credited to Mark John Arrowsmith, Donald Roy Kuriger, David M. Rapoport.
Application Number | 20190099569 16/134790 |
Document ID | / |
Family ID | 45688962 |
Filed Date | 2019-04-04 |
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United States Patent
Application |
20190099569 |
Kind Code |
A1 |
Rapoport; David M. ; et
al. |
April 4, 2019 |
SYSTEM, APPARATUS AND METHOD FOR SUPPLYING GASES
Abstract
A system, apparatus and methods are provided for supplying gases
to a user. The supply includes a sub-therapeutic mode and a
pressure support mode for delivering therapy to a user. A flow
diversion device or valve switches from a first mode corresponding
with the sub-therapeutic mode of the system to a second mode
corresponding with the pressure support mode of the system. In the
first mode, the valve opens a larger flow path between the interior
of the user interface and ambient air than in the second mode.
Inventors: |
Rapoport; David M.; (New
York, NY) ; Kuriger; Donald Roy; (Auckland, NZ)
; Arrowsmith; Mark John; (Auckland, NZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Fisher & Paykel Healthcare Limited |
Auckland |
|
NZ |
|
|
Family ID: |
45688962 |
Appl. No.: |
16/134790 |
Filed: |
September 18, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13991131 |
Sep 17, 2013 |
10099026 |
|
|
PCT/US2011/063137 |
Dec 2, 2011 |
|
|
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16134790 |
|
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|
|
61419421 |
Dec 3, 2010 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 2016/0039 20130101;
A61M 16/0069 20140204; A61M 16/16 20130101; A61M 2016/0027
20130101; A61M 16/20 20130101; A61M 16/208 20130101; A61M 16/0066
20130101; A61M 16/0057 20130101; A61M 2205/502 20130101; A61M
2205/3653 20130101; A61M 16/109 20140204; A61M 16/0816
20130101 |
International
Class: |
A61M 16/00 20060101
A61M016/00; A61M 16/08 20060101 A61M016/08; A61M 16/20 20060101
A61M016/20; A61M 16/10 20060101 A61M016/10 |
Claims
1.-32. (canceled)
33. A flow diversion device comprising: an inlet portion comprising
an inlet connector portion, an outlet portion comprising an outlet
connector portion, a flow path provided through a body from an
inlet end of the inlet portion to an outlet end of the outlet
portion, a central portion comprising a flow port extending through
a wall of the flow diversion device, wherein the flow path through
the flow diversion device can communicate with ambient surroundings
through the flow port, a flexible valve member that extends into
the flow path at a location between the inlet end of the inlet
portion and the flow port, wherein the wall defines an inner
surface of the flow path, the inner surface comprising an internal
perimeter surface surrounding the flow port that acts as a valve
seat when the flow diversion device is in a closed condition,
wherein the flow diversion device is configured such that flow
through the flow diversion device from the inlet end of the inlet
portion to the outlet end of the outlet portion pushes against the
flexible valve member to urge the flexible valve member toward the
closed condition, wherein the flow diversion device is configured
such that flow through the flow diversion device from the outlet
portion to the inlet portion pushes against the flexible valve
member to urge it toward the inlet portion and an opened condition,
wherein a gap is provided between at least a portion of the
perimeter of the flexible valve member and the inner surface of the
wall, and wherein a substantial portion of the flow path is
unimpinged by the flexible valve member in the opened
condition.
34. The flow diversion device of claim 33, wherein the flexible
valve member comprises a matching but slightly smaller profile than
the flow path cross section in the region of the flexible valve
member.
35. The flow diversion device of claim 34, wherein the flow path
cross section in the region of the flexible valve member is
substantially rectangular.
36. The flow diversion device of claim 33, wherein the flow port is
located downstream of the flexible valve member.
37. The flow diversion device of claim 33, wherein the flexible
valve member is cantilevered from the inside surface of the wall
forming the flow path.
38. The flow diversion device of claim 33, wherein the flexible
valve member is able to flex toward or away from the closed
condition by bending adjacent its connection with the wall forming
the flow path or by bending along its length.
39. The flow diversion device of claim 33, wherein a secured end of
the flexible valve member is clamped between two portions of the
flow diversion device.
40. The flow diversion device of claim 33, wherein the flexible
valve member is formed as a single leaf.
41. The flow diversion device of claim 33, wherein the flexible
valve member is formed of a flexible polymeric material.
42. The flow diversion device of claim 33, wherein an area of the
flow port is between about 10% and about 50% of the flow path.
43. The flow diversion device of claim 33, wherein when in the
opened condition, the flexible valve member is configured to bend
toward a flow generator during exhalation.
44. The flow diversion device of claim 33, wherein the flexible
valve member comprises an embedded portion.
45. The flow diversion device of claim 44, wherein the valve seat
is disposed on or near a plane that is spaced away from the
embedded portion.
46. A system comprising: a flow generator, a user interface, a
supply conduit connecting the supply device and the user interface,
and the flow diversion device of claim 33.
47. The system of claim 46, wherein the flow diversion device is
located at or generally adjacent to the user interface.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority benefit under 35 U.S.C.
.sctn. 119(e) of U.S. Provisional Application No. 61/419,421, filed
on Dec. 3, 2010, which is hereby incorporated by reference in its
entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention generally relates to apparatus and
methods for supplying respiratory gas under positive pressure to a
sleeping user, such as in the treatment of obstructive sleep apnea
(OSA). More particularly, the present invention relates to such
apparatus and methods in which a condition of a user's body is
sensed. Even more particularly, the present invention relates to
such apparatus and methods featuring a gas supply that is
responsive to breathing and that includes a valve in the control
mechanism.
Description of the Related Art
[0003] A common method of treating obstructive sleep apnea (OSA)
involves a pressure device that provides breathing gases, typically
air, to a user (often referred to as the patient) while the user is
asleep. These machines fall into the broad classification of PAP
(positive airway pressure) devices or CPAP (continuous PAP)
devices.
[0004] Within this broad classification, there are wide variations.
For example, some machines provide different pressure during user
inspiration than during user expiration (Bi PAP), some machines
provide an auto-setting or autotitrating mode, wherein the supplied
pressure varies through the period of use in response to detected
events. In this context, detected events may include snoring,
hypopneas and obstructive breathing. Some machines respond to user
awakening and mask removal, for example, by reducing the delivered
pressure. Some machines deliver a predetermined set pressure, which
may be delivered at the same pressure night after night or which
may be varied night by night by physical adjustment or by automatic
adjustment by the unit. Some machines include a ramp function that
begins automatically or that begins by user selection. The ramp
function causes the machine to commence operation at a low
pressure, which is sometimes settable, and to gradually increase to
a higher pressure, which may be a predetermined treatment pressure
or which may be an intermediate pressure.
[0005] The machines typically provide controlled pressure delivery.
For example, the machines typically include a flow generator, a
pressure sensor that senses the pressure being delivered to the
user, and a feedback control that controls the output of the flow
generator based upon a sensor signal so that the sensed pressure is
maintained close to a demand pressure. Alternatively, the flow
generator may include a fan that generates a known pressure and
flow response. The output of the flow generator can be controlled
to deliver a desired pressure using feedback from a flow sensor in
a circuit that is connected to the flow generator. Alternatively,
the flow generator may include a fan that provides a substantially
uniform pressure at a given rotation speed across a useful range of
flow. Pressure then can be controlled by setting a constant motor
speed.
[0006] Even for the lower pressure at the start of a ramp cycle,
most of the machines supply a minimum pressure of 3 cmH2O or more.
The minimum pressure is more comfortable for the user than the full
treatment pressure and results in a sufficient flow of breathing
gases through a supply line to the user so that breathing gases
exit through a bias flow or a controlled leak port provided at or
near a user interface that is connected to the supply line.
SUMMARY OF THE INVENTION
[0007] An object of the present invention is to provide apparatus
or method for providing breathing gases to a user, which at least
go someway toward improving on prior systems, or which will at
least provide users with a useful choice.
[0008] In some configurations, an apparatus comprises a flow
generator and a controller connected to control the output of the
flow generator. A conduit extends from the flow generator to
connect with a user interface with the inside of the conduit and
the inside of the user interface defining a gases space. A valve
positioned at or adjacent the user interface. The valve being
switchable between a first mode in which the gases space is
significantly open to ambient through the valve and a second mode
in which the gases space is not significantly open to ambient
through the valve. The controller including one or more positive
airway pressure support modes in which the controller may cause the
flow generator to deliver pressure support to the airway of a user
with the valve in the second mode and the controller including one
or more sub-therapeutic modes in which the controller may cause the
flow generator to deliver flow of gases to the user with the valve
in the first mode.
[0009] The valve can include an aperture that communicates the
gases space with ambient and a valve member that, in a second
position, closes the aperture and is substantially out of the flow
path of gases through the conduit or interface and, in a first
position, leaves the aperture open for substantially unimpeded flow
from the interface to the ambient.
[0010] In the first position, the valve member may partially, but
not fully, occlude flow from the flow generator to the interface.
In some configurations, the first position of the valve comprises
the valve being bent towards the user when the user is inhaling. In
some configurations, the first position of the valve comprises the
valve being bent toward the flow generator when the user is
exhaling.
[0011] The valve member when in the first position preferably
occludes between about 50% and about 80% of a cross-sectional area
of a flow path from the flow generator to the user interface.
[0012] The positive airway pressure support modes can include a
supply of gases to a user such that, with the valve in the first
mode, the flow generator provides enough flow to the user interface
such that with the interface worn by a user a pressure greater than
about 3 cm H2O is produced.
[0013] A sensor can be included to derive a measure of pressure in
the gases space such that in a positive airway pressure mode the
controller controls output of the flow generator according to a
command pressure and feedback from the sensor for deriving the
measure of pressure in the gases space.
[0014] In some configurations, in the sub-therapeutic mode, the
controller provides a flow to the interface that is not sufficient
to force the valve into the closed position.
[0015] In the sub-therapeutic mode, the controller can cause the
flow generator to provide a flow greater than about 5 litres per
minute (most preferably greater than about 10 litres per
minute).
[0016] In some configurations, in the sub-therapeutic mode, the
controller causes the flow generator to provide a flow less than
about 20 litres per minute (most preferably less than 15 litres per
minute).
[0017] The valve can move from the first mode to the second mode
upon rising through a first threshold of flow/pressure, and from
the second mode to the first mode on falling through a second
threshold of flow/pressure, wherein the first threshold of
flow/pressure is higher than the second threshold of
flow/pressure.
[0018] In some configurations, with the valve in the first mode and
the controller operating in the sub-therapeutic mode, the valve can
remain stable for flows up to at least about 20 litres per minute,
with delivered pressures below about 2 cm H2O.
[0019] With the valve in the second mode, and the controller
operating in the pressure support mode, the valve can remain stable
at pressures down to about 3 cm H2O or lower.
[0020] In some configurations, the lowest pressure for which the
valve is stable in the second mode when the controller is in the
pressure support mode is less than about 1 cm H20 above the average
delivered pressure when the valve is in the first mode and the
controller is in the sub-therapeutic mode supplying about 15 litres
per minute.
[0021] In some configurations, in the sub-therapeutic mode, the
controller controls the flow generator to deliver an average flow
at a level that assures flushing of the user interface but which
does not trigger the valve to switch from the first mode to the
second mode.
[0022] In some configurations, the controller controls the flow
generator to provide an average flow over multiple breaths that is
substantially constant.
[0023] In some configurations, an apparatus comprises a flow
generator and a controller connected to control the output of the
flow generator. A conduit extends from the flow generator to
connect with a user interface. The inside of the user interface
defines a gases space. A valve at or adjacent the user interface is
switchable between a first mode, in which the gases space is open
to ambient through the valve, and a second mode, in which the gases
space generally is not open to ambient through the valve. Control
of the flow generator and the construction and arrangement of the
valve can be such that in a period of transition (in either
direction) between a pressure support delivery to the user and a
sub-therapeutic supply to the user, user breathing does not trigger
repeated cycling between the first mode and the second mode.
[0024] The controller can include one or more positive airway
pressure support modes in which the controller may cause the flow
generator to deliver pressure support to the airway of a user with
the valve in the second mode and one or more sub-therapeutic modes
in which the controller may cause the flow generator to deliver
flow of gases to the user with the valve in the first mode.
[0025] In some configurations, the one or more positive airway
pressure modes include supply of gases to the user such that, with
the valve in the closed position, the flow generator provides
enough flow to the user interface such that, with the interface
worn by a user, a pressure greater than about 3 cm H2O is
produced.
[0026] A sensor can be provided to derive a measure of pressure in
the gases space wherein, in a positive airway pressure mode, the
controller controls the output of the flow generator according to a
command pressure and feedback of the measure of pressure in the
gases space from the sensor.
[0027] In some configurations, in the sub-therapeutic mode, the
controller provides a flow to the interface that is not sufficient
to force the valve into the first mode.
[0028] In some configurations, in the sub-therapeutic mode, the
controller causes the flow generator to provide a flow greater than
about 5 litres per minute (most preferably greater than about 10
litres per minute).
[0029] In some configurations, in the sub-therapeutic mode, the
controller causes the flow generator to provide a flow less than
about 20 litres per minute (most preferably less than about 15
litres per minute).
[0030] In some configurations, in the sub-therapeutic mode, the
controller controls the flow generator to deliver an average flow
at a level that assures flushing of the user interface, but which
does not trigger the valve to switch from the first mode to the
second mode.
[0031] The controller can control the flow generator to provide an
average flow over multiple breaths that is substantially
constant.
[0032] The valve can include an aperture communicating the gases
space with ambient and a valve member that in a first position
closes the aperture and is out of the flow path of gases through
the conduit or interface and in a second position leaves the
aperture open for substantially unimpeded flow from the interface
to the ambient.
[0033] In some configurations, in the second position, the valve
member partially, but not fully, occludes flow from the flow
generator to the interface.
[0034] In some configurations, in the second position, the area
valve member occludes between about 50% and about 80% of a cross
sectional area of a flow path from the flow generator to the user
interface.
[0035] In some configurations, the valve moves from the first mode
to the second mode upon rising through a first threshold of
flow/pressure, and from the second mode to the first mode on
falling through a second threshold of flow/pressure, wherein the
first threshold of flow/pressure is higher than the second
threshold of flow/pressure.
[0036] In some configurations, with the valve in the first mode and
the controller operating in the sub-therapeutic mode, the valve
remains stable for flows up to at least about 20 litres per minute
with delivered pressures below about 2 cm H2O.
[0037] In some configurations, with the valve in the second mode
and the controller operating in the pressure support mode, the
valve remains stable at pressures down to about 3 cm H2O or
lower.
[0038] In some configurations, the lowest pressure for which the
valve is stable in the second mode when the controller is in the
pressure support mode is less than about 1 cm H2O above the average
delivered pressure when the valve is in the first mode and the
controller is in the sub-therapeutic mode supplying about 15 litres
per minute.
[0039] In some configurations, an apparatus comprises a flow
generator, a controller connected to control the output of the flow
generator, and a conduit extending from the flow generator to
connect with a user interface with the inside of the conduit and
the inside of the user interface defining a gases space. A valve
can be positioned at or adjacent the user interface and can include
an aperture communicating the gases space with ambient and a valve
member wherein, in a first position, the valve member leaves the
aperture substantially open for flow from the interface to the
ambient and, in a second position, the valve member closes the
aperture, and wherein the valve member moves from the first
position to the second position upon rising through a first
threshold of flow/pressure, and from the second position to the
first position on falling through a second threshold of
flow/pressure, wherein the first threshold of flow/pressure is
higher than the second threshold of flow/pressure.
[0040] The controller can include one or more positive airway
pressure support modes in which the controller causes the flow
generator to deliver pressure support to the airway of a user with
the valve in the second mode and one or more sub-therapeutic modes
in which the controller causes the flow generator to deliver flow
of gases to the user with the valve in the first mode.
[0041] The positive airway pressure modes can include supply of
gases to the user such that, with the valve in the closed position,
the flow generator provides enough flow to the user interface such
that, with the interface worn by a user, a pressure greater than
about 3 cm H2O is produced.
[0042] A sensor can be provided to obtain a measure of pressure in
the gases space such that, in a positive airway pressure mode, the
controller controls the output of the flow generator according to a
command pressure and feedback of the measure of pressure in the
gases space from the sensor.
[0043] In some configurations, in the sub-therapeutic mode, the
controller provides a flow to the interface that is not sufficient
to force the valve into the closed position.
[0044] In some configurations, in the sub-therapeutic mode, the
controller causes the flow generator to provide a flow greater than
about 5 litres per minute (most preferably greater than about 10
litres per minute).
[0045] In some configurations, in the sub-therapeutic mode, the
controller causes the flow generator to provide a flow less than
about 20 litres per minute (most preferably less than about 15
litres per minute).
[0046] In some configurations, in the sub-therapeutic mode, the
controller controls the flow generator to deliver an average flow
at a level that assures flushing of the user interface but which
does not trigger the valve to switch from the first position to the
second position.
[0047] In some configurations, the controller controls the flow
generator to provide an average flow over multiple breaths that is
substantially constant.
[0048] In some configurations, with the valve in the first position
and the controller operating in the sub-therapeutic mode, the valve
remains stable for flows up to at least about 20 litres per minute
with delivered pressures below about 2 cm H2O.
[0049] In some configurations, with the valve in the second
position and the controller operating in the pressure support mode,
the valve remains stable at pressures down to about 3 cm H2O or
lower.
[0050] In some configurations, the lowest pressure for which the
valve is stable in the second position when the controller is in
the pressure support mode is less than about 1 cm H2O above the
average delivered pressure when the valve is in the first position
and the controller is in the sub-therapeutic mode supplying about
15 litres per minute.
[0051] In some configurations, in the second position, the valve
member partially, but not fully, occludes flow from the flow
generator to the interface.
[0052] In some configurations, in the second position, the valve
member occludes between about 50% and about 80% of a cross
sectional area of a flow path from the flow generator to the user
interface.
[0053] In some configurations, an apparatus comprises a flow
generator, a controller connected to control the output of the flow
generator, and a nasal mask for covering nasal passages of a wearer
but leaving a mouth uncovered. A conduit extends from the flow
generator to connect with the nasal mask with the inside of the
conduit and the inside of the nasal mask defining a gases space. A
valve is positioned at or adjacent the nasal mask which is
switchable between a first mode, where the gases space is open to
ambient through the valve, and a second mode, where the gases space
is not open to ambient through the valve. The controller controls
the flow generator to deliver gases through the conduit with the
valve in the first mode and with the valve in the second mode.
[0054] The controller can include one or more positive airway
pressure support modes in which the controller may cause the flow
generator to deliver pressure support to the airway of a user with
the valve in the second mode, and one or more sub-therapeutic modes
in which the controller may cause the flow generator to deliver
flow of gases to the user with the valve in the first mode.
[0055] The positive airway pressure modes can include supply of
gases to the user such that, with the valve in the first mode, the
flow generator provides enough flow to the user interface such
that, with the interface worn by a user, a pressure greater than 3
cm H2O is produced.
[0056] A sensor can be provided for deriving a measure of pressure
in the gases space where, in a positive airway pressure mode, the
controller controls the output of the flow generator according to a
command pressure and feedback of the measure of pressure in the
gases space.
[0057] In some configurations, in the sub-therapeutic mode, the
controller provides a flow to the interface that is not sufficient
to force the valve into the second mode.
[0058] In some configurations, in the sub-therapeutic mode, the
controller causes the flow generator to provide a flow greater than
about 5 litres per minute (most preferably greater than about 10
litres per minute).
[0059] In some configurations, in the sub-therapeutic mode, the
controller causes the flow generator to provide a flow less than
about 20 litres per minute (most preferably less than about 15
litres per minute).
[0060] In some configurations, in the sub-therapeutic mode, the
controller controls the flow generator to deliver an average flow
at a level that assures flushing of the user interface but that
does not trigger the valve to switch from the first mode to the
second mode.
[0061] In some configurations, the controller controls the flow
generator to provide an average flow over multiple breaths that is
substantially constant.
[0062] In some configurations, the valve includes an aperture
communicating the gases space with ambient and a valve member that
is moveable between a first position corresponding to the second
mode and a second position corresponding to the first mode, the
valve member in the first position closing the aperture and being
positioned out of the flow path of gases between the valve inlet
and the valve outlet, and the valve member in a second position
leaving the aperture open for substantially unimpeded flow from the
valve inlet to ambient.
[0063] In some configurations, in the second position, the valve
member partially, but not fully, occludes flow from the valve inlet
to the valve outlet.
[0064] In some configurations, in the second position, the valve
member occludes between about 50% and about 80% of a cross
sectional area of a flow path from the valve inlet to the valve
outlet.
[0065] In some configurations, the valve moves from the first mode
to the second mode upon rising through a first threshold of
flow/pressure, and from the second mode to the first mode on
falling through a second threshold of flow/pressure, wherein the
first threshold of flow/pressure is higher than the second
threshold of flow/pressure.
[0066] In some configurations, with the valve in the first mode and
the controller operating in the sub-therapeutic mode, the valve
remains stable for flows up to at least about 20 litres per minute
with delivered pressures below 2 cm H2O.
[0067] In some configurations, with the valve in the second mode
and the controller operating in the pressure support mode, the
valve remains stable at pressures down to about 3 cm H2O or
lower.
[0068] In some configurations, the lowest pressure for which the
valve is stable in the second mode when the controller is in the
pressure support mode is less than about 1 cm H2O above the average
delivered pressure when the valve is in the first mode and the
controller is in the sub-therapeutic mode supplying about 15 litres
per minute.
[0069] A valve can be provided for use at or adjacent a user
interface. The valve comprises a flow passage defined by at least
one wall. The flow passage extends between a valve inlet and a
valve outlet configured to open toward the user interface. An
aperture through the at least one wall defines the flow passage.
The aperture is positioned between the valve inlet and the valve
outlet with a valve member being positioned between the valve inlet
and the aperture. The valve member is movable between a first
position and a second position. The valve member in the first
position leaving the aperture open for flow from the interface to
ambient and the valve member in the second position closing the
aperture. The valve member is adapted to move from the first
position to the second position upon rising through a first
threshold of flow/pressure in the flow passage, and the valve
member is adapted to move from the second position to the first
position on falling through a second threshold of flow/pressure in
the flow passage, wherein the first threshold of flow/pressure is
higher than the second threshold of flow/pressure.
[0070] In some configurations, in the second position, the valve
member partially, but not fully, occludes flow from the valve inlet
to the valve outlet.
[0071] In some configurations, in the second position, the valve
member occludes between 50% and 80% of a cross sectional area of a
flow path from the valve inlet to the valve outlet.
[0072] A valve can be provided for use at or adjacent a user
interface. The valve comprises a flow passage at least partially
defined by a wall. The flow passage extends between a valve inlet
and a valve outlet that is adapted to be fluidly connected to the
user interface. An aperture is defined through the wall. The
aperture is positioned between the valve inlet and the valve outlet
with a valve member being positioned between the valve inlet and
the aperture. The valve member is movable between a first position
and a second position. When the valve member is in the first
position, the aperture is left open for flow from the interface to
ambient. When the valve member is in the first position, flow is
partially but not fully occluded through the flow passage. When the
valve member is in the second position, the aperture is
substantially closed. The valve member in the first position
occludes between about 50% and about 80% of a cross section area of
a flow passage between the inlet and the outlet at the valve
member.
[0073] In some configurations, a cross-sectional area of the flow
passage through the valve at the valve member is between about 40
mm2 and about 250 mm2.
[0074] In some configurations, the area of the aperture is between
about 10% and about 50% of the cross sectional area of the flow
passage through the valve.
[0075] In some configurations, the area of the aperture is between
about 15% and about 25% of the cross sectional area of the flow
passage through the valve.
[0076] In some configurations, in the second position, the valve
member partially, but not fully, occludes flow from the flow
generator to the interface.
[0077] In some configurations, in the second position, the area
valve member occludes between about 50% and about 80% of the area
of the flow path from the flow generator to the user interface.
[0078] A valve can be provided for use at or adjacent a user
interface. The valve comprises a flow passage defined by a wall.
The flow passage extends between a valve inlet and a valve outlet.
An aperture is defined through the wall. The aperture is positioned
between the valve inlet and the valve outlet. A valve member is
positioned between the valve inlet and the aperture. The valve
member is movable between a first position and a second position,
wherein the valve member in the first position leaving the aperture
open for flow from the user interface to ambient, the valve member
in the second position at least partially closing the aperture, and
the valve member being stable in the first position under user
breathing for average flows over multiple breaths of up to 30
litres per minute, delivering a pressure below about 1.5 cm H2O,
and being stable in the second position under user breathing for
controlled pressures above about 1.7 cm H2O.
[0079] In some configurations, a cross-sectional area of the flow
passage through the valve from the inlet to the outlet is between
about 350 mm2 and about 600 mm2.
[0080] In some configurations, the area of the aperture is between
10% and 50% of a cross-sectional area of the flow passage through
the valve.
[0081] In some configurations, the area of the aperture is between
15% and 25% of the cross sectional area of the flow passage through
the valve.
[0082] In some configurations, in the second position, the valve
member partially, but not fully, occludes flow from the flow
generator to the interface.
[0083] In some configurations, in the second position, the valve
member occludes between about 50% and about 80% of a cross
sectional area of the flow path from the flow generator to the user
interface.
[0084] In some configurations, a system is provided for supplying
respiratory gases to a user wearing a user interface. The system
comprises a flow generator and a controller adapted to control
operation of the flow generator. The flow generator has a flow
control mode and a pressure control mode. The flow control mode
comprises generation of a sub-therapeutic flow of gases and the
pressure control mode comprises generation of a therapeutic flow of
gases. A flow diversion valve is positioned between the flow
generator and the user interface. The flow diversion valve
comprises a flow channel and an aperture. The aperture places the
flow channel in fluid communication with ambient. The flow
diversion valve further comprises a valve member that is
cantilevered from a wall and that extends toward the flow channel
in a first position. The valve member is moveable between the first
position and a second position. The valve member overlies at least
a portion of the aperture in the second position and the valve
member occludes only a portion of the flow channel in the first
position. The valve member is movable from the first position to
the second position when the flow generator transitions from the
flow control mode to the pressure control mode and movable from the
second position toward the first position when the flow generator
transitions from the pressure control mode to the flow control
mode.
[0085] In some configurations, the valve member does not abut a
valve seat in the first position.
[0086] In some configurations, the valve member is in the first
position when there is no flow through the flow channel and the
valve member does not abut a valve seat in the first position. In
some configurations, the first position of the valve comprises the
valve being bent towards the user when the user is inhaling. In
some configurations, the first position of the valve comprises the
valve being bent toward the flow generator when the user is
exhaling.
[0087] In some configurations, the valve member when in the first
position occludes between about 50% and about 80% of a
cross-sectional area of the flow channel.
[0088] In some configurations, the flow control mode comprises
delivering an average flow rate of between about 15 litres per
minute and about 17 litres per minute.
[0089] In some configurations, the flow control mode comprises
delivering a pressure of less than about 4 centimeters water.
[0090] In some configurations, the valve member abuts a land in the
second position.
[0091] In some configurations, the land is offset inwardly toward
the flow channel from a portion of the valve member that is secured
to a body of the valve.
[0092] In some configurations, the aperture defines an opening with
a cross-sectional area of about 90 mm2.
[0093] 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.
[0094] The term "comprising" is used in the specification and
claims, means "consisting at least in part of." When interpreting a
statement in this specification and claims that includes
"comprising," features other than that or those prefaced by the
term may also be present. Related terms such as "comprise" and
"comprises" are to be interpreted in the same manner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0095] These and other features, aspects and advantages of the
present invention will now be described with reference to the
drawings of preferred embodiments, which embodiments are intended
to illustrate and not to limit the invention, and in which
figures:
[0096] FIG. 1 is a flow diagram illustrating a control method that
is arranged and configured in accordance with certain features,
aspects and advantages of the present invention and that can be
implemented by a controller of a gas supply apparatus.
[0097] FIG. 2 is a block diagram illustrating a gases supply system
that is arranged and configured in accordance with certain
features, aspects and advantages of the present invention.
[0098] FIG. 3a and FIG. 3b are two non-limiting examples of plots
of pressure and flow against time for portions of a session using
an apparatus that is arranged and configured in accordance with
certain features, aspects and advantages of the present
invention.
[0099] FIG. 4 is a block diagram of an experimental setup used to
evaluate machines arranged and configured in accordance with
certain features, aspects and advantages of the present
invention.
[0100] FIGS. 5A to 5F are plots that show opening and closing
characteristics of a flow diversion device that is arranged and
configured in accordance with certain features, aspects and
advantages of the present invention.
[0101] FIGS. 6A to 6F are plots that show opening and closing
characteristics of a flow diversion device that is arranged and
configured in accordance with certain features, aspects and
advantages of the present invention.
[0102] FIGS. 7A and 7B are plots that show flow and pressure versus
time for each of two valves and illustrate differences in the valve
characteristic between the two valves.
[0103] FIGS. 8A and 8B are plots that show flow and pressure versus
time that illustrate differences between operating in a flow
control mode when the valves are on the verge of closing and
operating in a pressure control mode.
[0104] FIG. 9A is a cross-sectional side elevation of a flow
diverting valve that is arranged and configured in accordance with
certain features, aspects and advantages of the present
invention.
[0105] FIG. 9B is a perspective view of the valve of FIG. 9A.
[0106] FIG. 9C is a cross-section of the value of FIG. 9A showing a
profile of the valve.
[0107] FIG. 10A is a side perspective view of a flow diverting
valve that is arranged and configured in accordance with certain
features, aspects and advantages of the present invention.
[0108] FIG. 10B is cross-sectional top view of the valve of FIG.
10A.
[0109] FIG. 10C is a sectioned view of the valve of FIG. 10A taken
along the line C-C in FIG. 10B.
[0110] FIG. 10D is a perspective view of the sectioned valve of
FIG. 10C.
[0111] FIG. 11 is a graphical representation of an impact of valve
orifice sizes on flow rates.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0112] The following description presents a system, and elements of
that system, that can provide an alternative to a defined pressure
ramp at the commencement of a treatment session. The system, and
the elements of that system, also can provide an alternative to low
therapeutic pressures (i.e., awake pressures) at other times when a
user (i.e., user) is thought to be awake.
[0113] Certain features, aspects and advantages of the present
invention relate to a sub-therapeutic control mode in which the
user receives mask pressures that approach ambient or atmospheric
pressure, which is referred to herein as "zero pressure." The use
of zero pressure contrasts with traditional therapeutic CPAP, which
maintains a therapeutic level of pressure at all times when therapy
for obstructive sleep apnea is needed.
[0114] A sub-therapeutic control mode allows very low mask
pressures at times when therapy is not needed, desired or intended.
The very low mask pressures make using the system more pleasant for
the user by removing unnecessary or undesired pressure wherever
possible while reducing the likelihood of compromising other
functions of the system (e.g., external venting to reduce the
likelihood of CO2 rebreathing). Because of increased comfort
produced by reduced perceived pressure when therapeutic airway
support is not needed or not desired, the sub-therapeutic control
mode is believed to encourage increased compliance, which will
extend the time the user wears the system and receives therapeutic
CPAP treatment.
[0115] A limiting factor in the implementation of sub-therapeutic
gas delivery with existing CPAP machines is that substantially all
systems currently used with CPAP machines rely on non-zero mask and
circuit pressure to force air through a "leak port" throughout the
respiratory cycle. The air forced out through the leak port
provides venting of exhaled carbon dioxide, particularly during
exhalation, and reduces the likelihood of rebreathing of exhaled
gas during the next inspiration. When the mask and circuit pressure
falls below a certain low level (e.g., generally around 2 cm H2O to
5 cm H2O depending upon the size of the leak port), venting through
a fixed size leak port becomes generally ineffective.
[0116] Two types of valves that can be used in the system that is
arranged and configured in accordance with certain features,
aspects and advantages of the present invention are
"non-rebreathing" valves and "exhalation valves." Each of the two
types of valves creates a second port through which exhaled gas can
be directed to reduce the likelihood of rebreathing.
Non-rebreathing valves generally are passively opened when the
relevant pressure is substantially zero or zero (e.g., when a gas
supply apparatus has stopped functioning) or when flow reverses
within a circuit. Exhalation valves also can be used in non-CPAP
circuits and typically trigger from shut to open with rises in
pressure during exhalation. Exhalation valves are often driven by
an external triggering mechanism that detects expiration; however,
when used during CPAP, the exhalation valves cannot be dependent on
pressure at the valve alone because the pressure is high in both
therapeutic CPAP and during exhalation. In addition, the valve must
be actively triggered or driven by an outside controller. In some
embodiments, the system can be implemented with specifically
adapted valves having characteristics described later in this
specification.
[0117] Some implementations of the sub-therapeutic mode utilize an
external decision about which mode of the valve is active. At a
predetermined point, which could be predicated on the desired CPAP
pressure or on the state of arousal of a user, the controller
adjusts the characteristics of the flow and pressure in the circuit
to trigger an increase in the leak out of the circuit, such as, for
example but without limitation, opening an additional port or
otherwise creating an increase in leakage flow. In the therapeutic
CPAP mode, the controller delivers gases at a flow and pressure
such that the valve minimizes the size of the leak (e.g., by
closing the additional port). Preferably, the change in valve
behaviour occurs generally as a passive response of the valve but
in response to some signal generated by an algorithm controlling
CPAP delivery.
[0118] Preferably, the transition from the sub-therapeutic mode to
the conventional therapy mode of operation (i.e., CPAP) happens in
a substantially "smooth" fashion and does not significantly
oscillate with respiratory swings. Thus, the mode change may be
largely undetected or minimally intrusive to the user. One aspect
of making the transition generally transparent to the user is
minimizing the change in system conditions (e.g., pressure and
flow) that activates the change in mode of operation of the valve
while preserving the stability of the valve mode.
[0119] Certain features, aspects and advantages of the present
invention relate to a valve with two modes. Certain features,
aspects and advantages of the present invention relate to
activating control of the valve mode through changes in the
behaviour of the CPAP gas supply without other external control
signals to the valve. Preferably, despite minimal change in
pressure but at a desired time, the valve switches between an
"open" state, a state with minimal pressure in the circuit and low
but significant flow to the user, and a "closed" state, a state
with pressure that can be raised to therapeutic levels, and the
transition occurs with little or no change in the system conditions
perceived by the user. In other words, the "open" state refers to
the interior of the circuit being open to ambient surroundings
through the valve while the "closed" state refers to a state where
the valve does not allow the same substantial flow between inside
the circuit and ambient through the valve. However, some flow
between inside the circuit and ambient may be provided for in the
closed state. For example, the valve may incorporate a bias flow
vent to provide suitable leak during therapy.
[0120] With reference to FIG. 2, the system generally comprises a
gas supply device 200, a user interface 204, a supply conduit or
tube 202 for connecting between the supply device 200 and the user
interface 204 and a flow diversion device 250. The flow diversion
device preferably is located at or generally adjacent to the user
interface 204.
[0121] The flow diversion device 250 can operate in at least two
modes. In some configurations, the flow diversion device 250
operates in only two modes. In a first mode, the gases space inside
the user interface 204 is substantially open or open to ambient
surroundings through the flow diversion device 250. In a second
mode, the flow diversion device 250 allows the user to receive a
gases flow at a therapeutic treatment pressure from the gases
supply device 200.
[0122] Preferably, the flow diversion device 250 comprises a type
of valve in which the valve 250 is in the first mode or condition
at low pressure or flow conditions (i.e., sub-therapeutic supply
conditions). In this condition, the interior of the user interface
204 is substantially open to ambient surroundings through the valve
250. In the second mode or condition, the valve 250 is closed and
the gases space inside the user interface 204 is significantly less
open to ambient surroundings through the valve 250.
[0123] Typically, the gases space inside the user interface 204 may
be connected at all times with the ambient environment through a
vent 206, such as a bias flow vent or other controlled leak port.
For example, the vent 206 is illustrated in FIG. 2 on the user
interface 204. In some configurations, the vent 206 may be part of
the flow diversion device 250 itself.
[0124] Preferably, the flow path to ambient surroundings through
the flow diversion device 250, with the valve in the first mode, is
a path of much lower resistance than the flow path through the
controlled leak provided through the vent 206. Thus, with the flow
diversion device 250 in the first mode, the flow path between the
gases supply device 200 and the gases space inside the user
interface 204 is somewhat restricted but is not closed while a
comparatively open flow path is provided between the gases space
inside the user interface 204 and the surrounding ambient
conditions through the flow diversion device 250. In the second
mode, there is comparatively little or no flow between the gases
space inside the user interface 204 and the surrounding ambient
conditions through the flow diversion device 250 while the flow
diversion device 250 presents a comparatively low flow restriction
between the gases space inside the user interface 204 and the gases
supply device 200.
[0125] Preferably, the control of the gases supply device 200 and
the arrangement of the flow diversion device 250 (e.g., the valve)
are adapted so that, in a period of transition in either direction
between delivery of pressure support to the user and delivery of a
sub-therapeutic supply to the user, user breathing does not trigger
repeated cycling between the first mode and the second mode of the
flow diversion device 250. Accordingly, the valve 250 does not
flutter to any significant degree at this transition.
[0126] Preferably, the flow diversion device 250 switches from the
first mode to the second mode and from the second mode to the first
mode according to the prevailing flow and pressure conditions.
Typically, these flow and pressure conditions are generated by the
gases supply device 200 and user breathing. Thus, the gases supply
device 200 provides a base condition (e.g., flow and/or pressure)
and the user breathing superimposes a transient variation in flow
and/or pressure as the user inhalation and exhalation flow is
superimposed on the flow from the gas supply device 200.
[0127] The flow diversion device 250 preferably has no means of
control other than the prevailing flow and/or pressure conditions
acting on the valve 250 and an associated valve member. The valve
250 is not actively controlled except by the flow generator 200
varying the prevailing pressure and/or flow conditions.
[0128] When the system gradually moves between a sub-therapeutic
pressure and a therapeutic support pressure in the gases supply,
the flow diversion device 250 closes to be in the second mode.
Similarly, in moving from a therapeutic support pressure to a
sub-therapeutic level, the flow diversion device 250 opens to be in
the first mode.
[0129] The transition can be unstable for regular pressure or speed
control flow generators. In particular, as the conditions reach a
level at which the valve 250 will move from the first mode to the
second mode, the fluctuation in conditions caused by user breathing
can lead to the valve 250 opening and closing with each user
breath. A similar effect can be noted where the pressure support is
decreasing toward the sub-therapeutic level and approaches the
transition conditions for the flow diversion device 250.
[0130] Accordingly, the flow diversion device 250 in the
illustrated system switches from the first mode (i.e., the open
mode) to the second mode (i.e., the closed mode) at a first set of
conditions, and from the second mode (i.e., the closed mode) to the
first mode (i.e., the open mode) under a second set of conditions.
The first set of conditions is relatively higher than the second
set of conditions. Accordingly, with the average pressure and/or
flow increasing, when the flow diversion device 250 switches from
the first mode to the second mode, the minimum pressure and/or flow
is already above the pressure and/or flow at which it would switch
from the second mode to the first mode. Similarly, when the average
pressure and/or flow is decreasing, once the flow diversion device
250 switches from the second mode to the first mode, the minimum
pressure and/or flow is already below the pressure and/or flow at
which it would switch from the first mode to the second mode.
[0131] Preferably, the difference in the level of the conditions is
greater than the fluctuation in the conditions resulting merely
from user breathing. The fluctuation depends on system conditions.
For example, pressure fluctuation in the region of the valve 250
depends on resistance to flow exiting the system. With the flow
diversion device 250 open, the interior of the user interface 204
and flow diversion device 250 are more openly connected to the
surrounding ambient conditions and the fluctuating pressure creates
a smaller pressure swing than with the flow diversion device 250
closed. Furthermore, with a large bias vent 206, the pressure swing
caused by breathing is reduced.
[0132] Certain characteristics of the gas supply apparatus 200 can
exacerbate the pressure swing from user breathing. For example, a
pressure feedback control operating to control the output of the
flow generator can exaggerate the fluctuation in flow.
[0133] The valve 250 is biased toward the open condition. In the
sub-therapeutic mode, the delivered supply is intended to allow the
valve 250 to remain in the open condition. The pressure feedback
control can have an adverse impact as the delivered supply
approaches the condition that, in a steady state, would trigger the
valve 250 to switch to the closed condition. In particular, within
each breath cycle, the pressure control increases the output of the
flow generator during inhalation relative to exhalation. This
brings the flow passing the valve 250 to a critical point, thereby
priming the valve 250 for closure. During the next expiration by
the user, pressure rapidly increases in the circuit 202 and the
"primed" or partially closed valve 250 now fully closes.
[0134] In some embodiments, the gas supply device 200 operates with
a control method that reduces the occurrence of valve instability
(i.e., valve flutter) caused by the fluctuation of the flow from
user breathing. In particular, the control method for the gas
supply device 200, at least as the supply condition approaches the
transition conditions between the first mode and the second mode,
is adapted to not significantly exacerbate, and preferably to
alleviate, fluctuation in the particular system conditions that
cause switching of the valve 250. For example, the valve 250, which
will be described later, is sensitive to flow. In particular, the
valve 250 is sensitive to flow from the gas supply device 200 to
the user interface 204, to flow to ambient through the valve 250,
or both. As the supply conditions approach levels where the valve
250 might be unstable, the control method controls the output of
the gas supply device 200 according to an assessed average supply
flow and a desired average flow. For example, the control of the
gas supply 200 can implement a feedback control based upon average
gases flow. Preferably, during this period, the method does not
include a feedback control based upon pressure. This stabilises the
flow, or at least removes a destabilising influence on the flow
delivered by the flow generator or gas supply device 200. The flow
still fluctuates with user breathing, but the controller does not
take steps that exaggerate this fluctuation.
[0135] Accordingly, in some embodiments, the control results in a
substantially constant low flow generator speed and does not
respond to user breathing by changing the speed of the flow
generator during the breathing cycle. Because the flow is low and
does not increase as much when the user inspires as it would for a
pressure feedback control, the valve 250 is not "primed" for
closure, and thus does not close during expiration.
[0136] In therapeutic CPAP mode (e.g., at circuit pressures above a
low threshold of about 2-3 cm H20), the controller provides
feedback to the flow generator to maintain a "pressure control."
During inspiration, this causes an increase in the delivered flow
in order to maintain pressure, which brings the flow passing the
valve 250 to a level that primes the valve 250 for closure. During
the next expiration by the user, pressure rapidly increases in the
circuit 202 and the "primed" or partially closed valve 250 now
fully closes. Furthermore, the valve 250 is subsequently kept
closed by the now continuous positive pressure (e.g., CPAP).
[0137] In effect, the above described two modes result from tuning
the CPAP flow generator response to the oscillatory nature of a
user's breathing and from using the resulting interaction of the
pressure and flow to switch the valve mode without actually
actively interacting with the valve 250 with a separate
controller.
[0138] A benefit of this tuning between pressure control and flow
control of the gases supply device 200 and user breathing is that,
when the flow generator is switched between modes, the valve state
can be controlled with minimal change in either pressure or flow
alone to the user at the time of the switch.
[0139] When arranged and configured in accordance with certain
features, aspects and advantages of the present invention, the
system provides a sub-therapeutic pressure at the beginning of the
session or at times when the apparatus considers the user to be
awake. As used herein, sub-therapeutic pressures include pressures
below about 4 cm H2O, preferably below about 3 cm H2O and more
preferably pressures below about 1.5 cm H2O and most preferably
pressures about 1 cm H2O. The sub-therapeutic mode may be
selectable by a user, may be selectable by an overall control
algorithm of the apparatus, or may be an automatic function at the
beginning of every session of use of the apparatus. Once the user
is asleep, or after an initial time-set period of sub-therapeutic
delivery, the apparatus transitions and delivers a therapeutic
pressure.
[0140] Preferably, sub-therapeutic pressure is provided to the user
in conjunction with monitoring the flow delivered to the user. The
controller of the apparatus monitors the flow delivered to the user
and adjusts control of the flow generator to reduce the likelihood
or eliminate flow rates that may be insufficient to provide proper
flushing of the user interface. For example, the control may reduce
the likelihood of the average flow rate falling below about 10
litres per minute, preferably reduces the likelihood of the average
flow rate falling below about 12 litres per minute, most preferably
reduces the likelihood of the average flow rate falling below about
15 litres per minute.
[0141] For a given user interface, a particular flow rate may be
considered sufficient to provide appropriate flushing. Across most
user interfaces presently available, an average flow rate of about
15 litres per minute is thought to be sufficient. Whatever the
chosen flow rate, while in the sub-therapeutic mode, the apparatus
preferably adjusts operation of the flow generator to maintain an
average flow rate close to the chosen flow rate. For example, the
controller may maintain the average flow within about 5 litres per
minute of this amount, or most preferably within about 2 litres per
minute of this amount.
[0142] By way of example, the controller of the apparatus may
control the flow generator by controlling the power input to the
flow generator. In this case, in the sub-therapeutic mode, the
controller may decrease power input to the flow generator when the
measured average flow exceeds the desired flow range and may
increase flow generator power when the average flow is below the
desired range.
[0143] Alternatively or in addition, the controller may control
some other parameter of the flow generator, such as, for example
but without limitation, motor speed. In such a case, the controller
may command an increase in motor speed if the flow is below the
desired range and command a decrease in motor speed if the flow is
above the desired range.
[0144] Alternatively or in addition, the flow generator may include
a pressure source and a pressure regulator. In such a case, the
controller may reduce the set pressure of the pressure regulator
when the measured flow is above the desired range and may increase
the set pressure of the pressure regulator when the flow is below
the desired range.
[0145] Advantageously, the apparatus may operate in the
sub-therapeutic delivery mode during periods where the user is
awake but in a therapeutic delivery mode when the user is
asleep.
[0146] Accordingly, the controller may provide an initial period of
operation in the sub-therapeutic mode during each session of use.
This feature may also be used in an apparatus that includes
functions for determining that a user is awake during periods
within the session. For example, the Fisher & Paykel Healthcare
HC250 device with "Sensawake" function determines instances of user
arousal and reduces the delivered pressure to a pre-set awake
pressure once it determines that the user may be awake. By
implementing the above-described controls in such a device, the
device could, after reaching the awake pressure, enter the
sub-therapeutic mode.
[0147] In the sub-therapeutic mode, the control aims to maintain a
substantially steady flow at a flow level that is selected to be
sufficient to maintain appropriate flushing of the user interface
204. As used herein, substantially steady flow means that the
average flow over a period of multiple breaths (e.g., about 20
breaths) remains substantially constant or within a limited range
(e.g., a range of up to about 5 litres per minute) despite changing
system conditions. Changing system conditions includes, for example
but without limitation, changing leak conditions due to changes in
the efficiency of sealing of the user interface. By way of
clarification and comparison, changes in system conditions that
would see an increase in flow under a constant pressure controlled
system of greater than about 5 litres per minute are responded to
with a substantially steady flow in the sub-therapeutic mode.
[0148] In the therapeutic mode, the controller delivers a
substantially steady pressure. This may include a pressure feedback
control, or be the result of a flow generator with a steady
pressure output for a given operating speed. Like substantially
steady flow, substantially steady pressure refers to the average
pressure over multiple breaths.
[0149] One non-limiting example control method that is arranged and
configured in accordance with certain features, aspects and
advantages of the present invention is illustrated in FIG. 1. The
illustrated control method may be incorporated into an apparatus
that is arranged and configured in accordance with certain
features, aspects and advantages of the present invention. The
illustrated method for implementing the sub-therapeutic mode
commences at 100 and may be triggered by a conscious user choice,
such as, for example but without limitation, by selecting a control
mode using the electrical user control interface. In some
embodiments, the mode may be an initial starting mode for the
apparatus or may be commenced by the apparatus according to a wider
control strategy.
[0150] After starting, a control command issues to the flow
generator to cause the flow generator to operate at an initial
level. See 102. For example but without limitation, the controller
can supply a command motor speed as an input to the flow generator
and a motor of the flow generator can be speed-controlled to the
command motor speed. In some applications, the apparatus may
provide one or more of one or more command pressure values, one or
more command flow values or one or more motor power inputs as input
parameters. Preferably, the initial command input parameter for the
flow generator is at a level that would usually provide a
sub-therapeutic pressure between about 0.2 cm H2O and 2 cm H2O with
a user interface correctly fitted. In the illustrated example, the
motor speed is set to about 4000 rpm.
[0151] An evaluation then is made regarding whether the user is
asleep. See 104. Preferably, the controller maintains a value
representing the controller's belief that the user is asleep or
awake. This value may be a probability assessed by the controller
of whether the user is asleep or awake. The value can be assessed
against criteria to decide whether to proceed on the basis that the
user is asleep or to proceed on the basis that the user is
awake.
[0152] The value may be maintained by, for example but without
limitation, assessing recent breathing patterns of the user,
assessing recent history of apneaic events and/or obstructed
breathing of the user. This may be examined over a time period,
such as, for example but without limitation, the preceding few
minutes, ten minutes or other similar time period. Any suitable
methods of making a determination that the user is asleep or is
awake can be used. Some suitable methods are described in other
patent publications, for example U.S. Pat. No. 6,988,994 and US
2008/0092894, which are hereby incorporated by reference in their
entirety.
[0153] The "asleep" assessments, and the maintenance of a sleeping
value, may be made according to a separate control program running
in parallel with the control program described with reference to
FIG. 1. The separate control programs may be generally separate
subroutine routines that may be executed sequentially in a given
execution cycle but also may operate in parallel. If a separate
control program is used, the control program of FIG. 1 will
determine whether the user is asleep or awake based on an input
parameter maintained or output by the other control program.
[0154] If the program determines that the user is asleep, then a
therapeutic pressure is applied. See 106. The application of
therapeutic pressure application may begin, for example, by
immediately proceeding to a predetermined starting point pressure
(e.g., about 3 or 4 cm H2O or greater) for therapy. This pressure
may be a preset of the device or may be a variable pressure set by
a physician. In some configurations, the method may proceed
directly to a full treatment pressure, for example, a treatment
pressure prescribed by a physician and preconfigured in the device.
In some configurations, the control method may proceed to an
automatic titrating mode that commences at a starting therapeutic
pressure and that adjusts the supply pressure according to
breathing events, such as apneas, hypopneas, flow obstructions, and
periods of normal breathing.
[0155] In the therapeutic mode, the control method preferably seeks
to maintain a substantially steady pressure. For example, the
controller may control the flow generator based on input from a
pressure sensor that senses pressure in the user interface 204
using feedback from the pressure sensor to control the speed of, or
power input to, the flow generator, or to control the input
parameter of a pressure regulator. The pressure in the patent
interface 204 can be sensed in any suitable manner. For example,
the pressure can be sensed either by a sensor that is positioned
directly in the user interface 204 or by a sensor that interfaces
with a part of the flow path to the user interface 204 that is
downstream of the flow generator.
[0156] In some embodiments, the substantially steady pressure can
be generated using a fan having a substantially constant pressure
output for a given fan speed across a wide range of flow or from a
pressure regulator, such as a self-regulating pressure regulator
for example but without limitation, that may, for example but
without limitation, use a mechanically operative feedback control
to adjust the pressure output according to a particular input
parameter.
[0157] The therapeutic mode (e.g., positive pressure, CPAP or
autotitrating) may proceed according to any suitable treatment
program and/or method. Control of the particular applied pressure
in these methods may be by a separate control program or routine
running in parallel or otherwise in conjunction with the control
program described with reference to FIG. 1.
[0158] With reference again to FIG. 1, the illustrated control
method begins looping to determine when a user awakens so that the
machine can respond to the awakening of the user. See 108. For
example, the control loop depends upon the output of the separate
control loop that determines on a continuous basis an awakened
state of the user.
[0159] As shown at 110, if the user is still asleep, the method
continues to apply the therapeutic treatment pressure. See 106. The
control loop 106, 108, 110 continues until it is determined that
the user is awake. If it is determined that the user is awake, the
method commences the sub-therapeutic mode. For example but without
limitation, the sub-therapeutic mode can be commenced by changing
the input parameter to the flow generator so that the flow
generator provides gases at a sub-therapeutic pressure. See
102.
[0160] Once again, the method determines whether the user is awake.
See 104. If the user is awake, the method proceeds to measure the
flow. See 118. At 118, 120, 124, the measure of the flow is
compared against a preferred flow range and, at 124, 128, the input
parameter sent to the flow generator is adjusted accordingly.
Preferably, the method checks (see 118) an assessed flow against a
lower flow value. For example, the method checks whether the recent
average flow (e.g., the average flow over the preceding 5 breaths,
10 breaths, 10 seconds, 30 seconds or a similar period) is less
than a lower threshold (e.g., about 15 L/min).
[0161] The lower threshold may be a fixed predetermined value. For
example, the value may be chosen to be suitable for all suitable
user interfaces. In some embodiments, the lower threshold value may
be a settable value, for example, so that it can be set according
to a particular user interface used by the user. In some
embodiments, the lower threshold value may be taken from a table of
values based on a determined identity of the user interface or
might be assessed for a particular interface in a test mode
performed by the apparatus. In the simplest case, a fixed preset
flow value, such as a lower limit flow value of about 15 litres per
minute, is thought sufficient to provide a significant improvement
in comfort over prior art apparatus without compromising
safety.
[0162] If the assessed average flow is less than the lower
threshold level, the control method adjusts the input parameter to
the flow generator to increase the output of the flow generator.
For example, the controller may increase a demand motor speed. See
124.
[0163] An additional check may be provided after determining that
the average flow is below the lower control limit. See 122. The
additional check determines whether the pressure has reached a
therapeutic pressure level. While shown occurring after the lower
control limit check (see 118), the pressure level check can occur
at any suitable time. For example, in the illustrated method, the
additional check may be conducted between the lower threshold level
check and the output increase. See 122, 118, 124. Preferably, the
method checks an assessed pressure in the user supply against a
pressure threshold, for example but without limitation, 4 cm H2O.
See 122. Where the flow is assessed below the lower limit at 118
and the pressure is assessed above the threshold at 122, the method
preferably proceeds to leave the sub-therapeutic mode and switch
control to the therapeutic mode, as discussed above with reference
to 106.
[0164] The control method may also set a fault condition, for
example at 126. The controller may provide an indication of the
fault condition as an alert on the electrical user control
interface of the device or record the fault condition in a session
data log maintained by the device for later review by the user,
physician or other interested party.
[0165] Where the control method increases the flow generator output
at 124, this is, for example, by increasing the demand parameter
for the flow generator. The increase may be a fixed predetermined
incremental increase, an incremental increase that varies according
to the present value of the parameter, or an incremental increase
that varies according to the difference between the present value
of the average flow and the desired flow range. For example but
without limitation, the new input parameter (e.g., the new motor
speed in a control motor speed embodiment) may be a function of the
present motor speed, the present average flow value and a desired
average flow value.
[0166] Alternatively, if the average flow value is above the
minimum range value (see 118), the control method checks the
average flow value against an upper flow value threshold for the
range. See 120. Preferably, to maintain a low sub-therapeutic
pressure, the flow range between the minimum value and maximum
value is kept to a minimum. For example, the flow range may be
about 5 litres per minute or less, preferably about 3 litres per
minute or less, and most preferably about 2 litres per minute or
less.
[0167] Alternatively, both upward and downward adjustment of the
control parameter for the flow generator can be made based on a
single desired average flow value. This is particularly suitable if
an adjustment increment for the control parameter is a function of
the difference between the present average flow value and the
desired average flow value. In this method, the check against the
upper flow value threshold (see 120) can be removed with the method
proceeding directly from 118 to 128 in the case where the average
flow value is not less than the desired flow value. This
arrangement will lead to frequent adjustment of the motor input
parameter, but if the frequent adjustments are small, they may not
be significant. Similarly, a configuration can be used to does not
have a lower flow threshold being used.
[0168] If the average flow is determined to be above the preferred
range at 120 (or at 118 according to the modified method discussed
above), then at 128 the control method decreases the input
parameter to the flow generator. For example, the decrease may be a
predetermined increment, or an increment variable according to the
present average flow, the present value of the input parameter or
the difference between the present average flow and the desired
average flow range. The method then returns to 104. The method set
forth at 104, 118, 124, 120 and 128 broadly constitute a feedback
control controlling the output of the flow generator according to a
desired flow rate (or desired flow rate range) and based on an
assessed average flow rate value.
[0169] FIGS. 3A and 3B illustrate the effect of a control operating
in accordance with certain features, aspects and advantages of the
present invention. These plots are only intended to be
representative and have been simplified accordingly. Section A of
FIG. 3A shows normal breathing at the beginning of a session. The
pressure is low (e.g., approximately 0 cm H2O) however the flow is
averaging less than about 15 l/min.
[0170] Section B of FIG. 3A shows the device responding to the low
flow rate in Section A, which results in increased flow generator
speed (e.g., 118, 124 in FIG. 1), thereby causing the flow and
pressure to rise.
[0171] Section C of FIG. 3A shows a leak being introduced (e.g., a
mask leak occurs) and the level of flow increasing accordingly. The
pressure drops slightly due to the leak.
[0172] Section D of FIG. 3A shows the algorithm responding to the
increased level of flow by reducing the speed of the flow generator
until the flow is again averaging approximately 15 l/min (e.g.,
120, 128 in FIG. 1). The drop in speed further reduces the
pressure.
[0173] Section E of FIG. 3B shows normal breathing.
[0174] Section F of FIG. 3B shows a user having an apnoea. The
apnoea is shown by the flattening of the flow signal.
[0175] Section G of FIG. 3B shows that, in response to the event in
Section F of FIG. 3B, the device raises the pressure and normal
breathing resumes (e.g., 104, 106 in FIG. 1).
[0176] The chaotic flow signal at the end of Section G indicates
that the user has awoken and, at Section H, the pressure is reduced
accordingly until the approximately 15 l/min average flow is
maintained again (e.g., 108, 102 in FIG. 1).
[0177] With reference again to FIG. 2, FIG. 2 presents a block
diagram illustrating an embodiment of a breathing gases supply
system that is arranged and configured in accordance with certain
features, aspects and advantages of the present invention. The full
system includes the gas supply device 200, which is an apparatus
for delivering a supply of breathing gases, the supply conduit 202
and the user interface 204. As discussed above, the flow diversion
device 250 can be located at, on or adjacent the user interface
204. Preferably, the flow diversion device 250 is in one of these
locations because it allows venting to the atmosphere under certain
operating conditions, which limits carbon dioxide rebreathing and
provides oxygen. The supply conduit 202 extends from an outlet of
the gases supply device 200 to the user interface 204.
[0178] The user interface preferably includes the bias flow vent
206 that allows a controlled leak from the user interface 204. The
controlled leak allows the inside of the user interface 204 to be
continuously flushed by fresh gases supplied by the supply device
200. The user interface 204 may comprise any of the many types of
typical user interface for PAP delivery, including but not limited
to, for example but without limitation, nasal masks, full face
masks, oral masks, oral interfaces, nasal pillows, nasal seals or
nasal cannulas.
[0179] The vent 206 may be located directly on the user interface
204, the vent 206 may be located adjacent the user interface 204 on
a connector between the user interface 204 and the supply tube 202,
or the vent 206 may be located through the wall of the supply tube
202 at a location close to the user interface 204, for example but
without limitation.
[0180] The illustrated supply apparatus 200 includes a flow
generator, which can comprise a fan 210 driven by an electric motor
212. Air is drawn through an inlet 214 in the housing of the
apparatus by the fan 210. Pressurised air leaves the fan 210 and is
supplied to the user through the supply conduit 202, for example.
In some embodiments, controllable flow generators may draw on a
source of high pressure gas and regulate a flow of gas from the
high pressure source.
[0181] The apparatus 200 may include a humidifier 216. In some
embodiments, the humidifier 216 comprises a pass-over humidifier
where air passing through a humidifier chamber picks up a quantity
of water vapour from a water supply contained in a reservoir 218.
The water reservoir 218 may be heated by a heater 220. The
humidifier 216 may be integrated within the same housing as the
flow generator 210 or may be a separate component that can be used
as an option.
[0182] The heater 220 and the motor 212 are supplied with power
from a power supply 222. The amount of power to the motor 212 and
the amount of power to the heater 220 can be controlled by outputs
of a controller 224. The controller 224 is also supplied with power
from the power supply 222. The controller 224 receives input from
an electrical user control interface 226, for example but without
limitation. The controller 224 preferably includes an embedded
microcomputer with stored control programs or the like.
[0183] The controller 224 is also provided with an interface 228
that is used to connect with an external data source. For example
but without limitation, the external data source may be a
communication interface, such as a modem, or may be an interface to
an external memory, such as a smart card, disk drive, flash memory
or the like. For generic use, the interface 228 may be any suitable
data communication port that is arranged and configured in
accordance with any of the many available standards (e.g., a
universal serial bus (USB) port). The interface 228 can be used for
connecting a wide range of peripheral devices. In some
configurations, the interface 228 can be replaced by or augmented
with a wireless communication device (e.g., Bluetooth, wifi,
etc.).
[0184] The controller 224 preferably includes interfaces for
receiving input from the electrical user control interface 226 and
for receiving input from one or more sensors. The sensors can
include a flow sensor 230 and a pressure sensor 232. The pressure
sensor 232 can be positioned downstream of the fan 210. The flow
sensor 230 can be positioned upstream or downstream of the fan
210.
[0185] The apparatus preferably is configured to perform control
methods in the form of control programs executable by a
microcomputer of the controller 224, for example but without
limitation. In some embodiments, the controller 224 may comprise a
fixed electronic circuit implementing control programs, a
programmed logic circuit (e.g., an FPGA) implementing control
programs or the like. Any suitable Electronic circuits and logic
circuits implementing the control program may be used. In fact, all
of the methods and processes described herein may be embodied in,
and fully automated via, software code modules executed by one or
more general purpose computers or processors. The code modules may
be stored in any type of computer-readable medium or other computer
storage device. Some or all of the methods may be embodied in
specialized computer hardware. In addition, the components referred
to herein may be implemented in hardware, software, firmware, or a
combination thereof.
[0186] The illustrated apparatus, which preferably operates
according to the control methods described herein, provides a
sub-therapeutic mode of operation that is applied to the user while
the user is awake. Breathing at this lower pressure may be less
arduous than at the low therapeutic pressures applied at the
commencement of therapy by other devices. This may be more
comfortable and more pleasant for the end user, thereby improving
therapy acceptance and compliance. At the same time, a minimum flow
through the supply conduit 202 is provided to supply an adequate
flow of fresh breathing gases to the interface 204 to flush the
user interface 204 and reduce the likelihood of user
re-breathing.
[0187] As described above, upon the detection of sleep, or a
breathing disorder event, the apparatus will increase the delivered
pressure to a predetermined or automatically determined therapeutic
level at a comfortable and tolerable rate. When sleep or a
breathing disorder event occurs, the user can be assumed to be
asleep. Accordingly, the user should not be aware of or consciously
experience the required higher therapeutic pressures, again thereby
hopefully improving compliance.
[0188] Preferably, if the user wakes during the sleep session, the
apparatus will revert to the sub-therapeutic state. The now
conscious user will not experience, or will only experience for a
limited time, the higher therapeutic pressures that are supplied
while they are asleep because the apparatus returns to the
sub-therapeutic state. This should also increase user compliance,
particularly in the later stages of a sleep session, where
otherwise the user may remove and cast aside the user interface
before trying to return to sleep.
[0189] The method as described may be adapted by further
variations. A few of these variations have been described above and
several more will be described below. This is not an exhaustive
summary and many further variations and alternatives are possible
without departing from the scope of certain features, aspects and
advantages of the present invention.
[0190] According to one variation, the apparatus may monitor one or
more of the flow, the pressure, or other parameters that may
indicate user respiratory rate. From the user respiratory rate, the
controller may determine increased respiratory rate or increased
breath volume. In the presence of increased respiratory rate or
breath volume, or both, the controller 224 may increase the desired
flow level in the sub-therapeutic mode. Increased respiratory rate
or increased breath volume may be indicative of carbon dioxide
rebreathing. Increasing the desired flow level in the
sub-therapeutic mode may adapt the sub-therapeutic mode flow level
to account for prevailing system conditions. The controller 224 may
further filter this response according to the present user sleep
state, which may help to reduce the likelihood of false positives
due to dreaming, mask leaks and the like.
[0191] According to a further variation, one or more routines may
be provided to check for occurrences of negative pressure in the
user interface 204 during the sub-therapeutic supply mode. For
example, the control program of the controller 224 may measure,
derive or calculate a pressure in the mask or interface 204 on a
continuous basis, or at least at a point in time or points in time
during user inhalation. If the mask or interface pressure drops
below a predetermined threshold (e.g., about 0 cm H2O or slightly
below about 0 cm H20) during user inhalation, then the control
program adapts the delivered therapy in an effort to reduce or
eliminate these subzero pressures. These negative pressures may
otherwise be experienced by the user as an undesirable feeling of
being starved of air. The control program may apply the adaption
instantaneously (e.g., applied within a breath cycle) or over a
longer time period (e.g., adjusting an inhalation boost parameter
periodically).
[0192] The controller 224 may obtain the pressure in the interface
204 by providing a sensor at the interface 204 to receive direct
measurements of the internal pressure at the user interface. In
some embodiments, the controller 224 may predict the pressure at
the interface 204 from a measurement of the pressure of the
delivered flow leaving the flow generator 210 (e.g., before or
after the humidifier 216) and a predicted pressure drop between the
location of the measurement and the interface 204 (e.g., across the
length of the supply conduit). The control program can predict the
pressure drop on the basis of the instantaneous flow along the
conduit 202, for example. The control program can assume the
conduit 202 has a certain flow resistance or can calculate the
resistance of the conduit 202 or other assembly of components by
implementing a pre-therapy test comparing delivered pressure and
flow with no user interface connected to the conduit. The control
program may implement any suitable method.
[0193] The control program may adapt the sub-therapeutic supply in
a number of ways. One option would be to boost the target average
flow. However, boosting the target average flow may boost the peak
pressures during user exhalation and will boost the overall average
pressure, thereby reducing some of the comfort advantages
intended.
[0194] In some configurations, the controller can boost the
supplied flow on user inhalation, for example, by increasing the
output of the flow generator at the start of inhalation and
subsequently reducing the output of the flow generator back to a
lower level for exhalation. The control program may monitor user
respiration to determine the start and end of inhalation by
monitoring the variation in delivered flow or pressure on a
breath-by-breath basis. While the average flow over multiple
breaths is maintained substantially constant, the flow varies in an
essentially sinusoidal manner in time with the user breathing. The
flow is higher during inhalation than during exhalation. The
control program can determine the inhalation phase from this
variation.
[0195] According to another variation, the control program (e.g.,
the control program run by the controller) may provide a settable
parameter providing for a boosted inhalation flow. For example, a
settable parameter may be provided on a scale. A value of 0
indicates no boost to the input parameter for the flow generator
during inhalation relative to exhalation. A progressively higher
value indicates a progressively higher boost to the input parameter
of the flow generator used during inhalation relative to
exhalation. The user or the user's physician could set the
parameter according to measurement, according to a qualitative
assessment of total breathing volume of the user, or according to
reported instances of breathlessness during the sub-therapeutic
supply phase.
[0196] The controller 224, while implementing the sub-therapeutic
phase, may control a baseline input parameter to the flow generator
210 according to the average delivered flow and, during periods of
inhalation or periods of exhalation, may control the input
parameter to the flow generator 210 according to a combination of
the baseline parameter and the settable inhalation boost. According
to this, the baseline could be applied during inhalation or
exhalation. If the baseline is applied during exhalation, then the
inhalation parameter is a boost above the baseline. Where the
baseline is applied during inhalation, the exhalation pressure is a
reduction below the baseline according to the set parameter. By
boosting the flow (i.e., boosting beyond the normal fluctuation
provided by the user breathing alone) during inhalation relative to
exhalation, these variations reduce the likelihood of any feeling
of starvation at the interface 204.
[0197] According to a further variation, the control method may
include control of humidification of the breathing gases (e.g., by
varying a power input to a humidification heater 220) such that
humidification delivery in the sub-therapeutic mode is controlled
independently of humidification delivery in therapeutic modes. For
example, in the sub-therapeutic mode, the controller may reduce or
disable humidification (e.g., by reducing or turning off power to
the humidification heater 220).
[0198] According to a further variation, the apparatus may include
a user selectable, or automatically initiated, test sequence.
According to the test sequence, the control program causes the flow
generator 210, 212 to deliver a controlled therapeutic pressure for
a period of time. It is intended that the user will not consciously
experience high pressures at the interface 204. The test sequence
will provide an opportunity for the user to ensure that the mask is
fitted correctly. The control program may provide for a test
sequence selectable by a user at the electronic user control
interface, or may provide for the test sequence to automatically
commence at the beginning of the session, or both. The test
sequence may provide for a pressure delivery at a preset minimum
therapeutic pressure, a preset maximum therapeutic pressure, a
preset test pressure, or another pressure selected according to
previous use of the device (e.g., a 95th percentile pressure
established from previous sessions).
[0199] In some configurations of the apparatus, such as described
with reference to FIG. 2, the apparatus includes the flow sensor
230 and the pressure sensor 232. Each sensor, 230, 232 may be of
any suitable type. For example, the flow sensor 230 may be a
differential pressure sensor operating in conjunction with a flow
restriction. In that case, parts of the differential pressure
sensor may double as the pressure sensor. In some applications, an
assessed pressure may be derived independently by a discreet
pressure sensor. In some applications, the delivered pressure may
be inferred from blower speed, or calculated from a sensed flow and
blower speed, for example but without limitation. An assessment of
the delivered pressure may also account for an estimated pressure
drop between the PAP apparatus and the user, for example, by
accounting for a pressure drop along the conduit 202 according to a
measured flow. In addition, where the pressure sensor 232 is
present, flow can be inferred from blower speed and the output of a
pressure sensor rather than using a separate flow sensor.
Otherwise, any suitable flow sensor can be used.
[0200] FIG. 9A to FIG. 9C illustrate a flow diversion device 900
that can be used in an implementation of a system that is arranged
and configured in accordance with certain features, aspects and
advantages of the present invention. The flow diversion device 900
can be arranged as a connector for simplicity of assembly with
other pre-existing components.
[0201] The illustrated flow diversion device 900 includes an inlet
portion 902 and an outlet portion 904. In some embodiments, the
inlet portion 902 comprises an inlet connector portion 902 and the
outlet portion 904 comprises an outlet connector portion 904. The
inlet connector portion 902 includes an external tapered connecting
surface. The external tapered connecting surface can be a standard
taper. The outlet connector portion 904 includes an internal
tapered connecting surface. The internal tapered connecting surface
is used to secure a swivel connector, for example but without
limitation. Other configurations are possible.
[0202] A flow passage or bore is provided through a body of the
flow diversion device 900 from the inlet end of the inlet portion
902 to the outlet end of the outlet portion 904. A central portion
906 comprises a flow port 908 extending through a wall of the flow
diversion device 900. The flow path through the flow diversion
device 900 can communicate with the ambient surroundings through
the port 908.
[0203] A flexible valve member 910 extends into the flow path at a
location between the inlet to the inlet portion 902 and the port
908. An internal perimeter surface 920 surrounding the port 908 may
act as a land or valve seat for when the flow diversion device 900
is in the closed condition. In the closed condition, a valve flap
cuts off flow from inside the user interface 204 to ambient
surroundings through the port 908.
[0204] Flow through the flow diversion device 900 from the inlet of
the inlet portion 902 to the outlet of the outlet portion 904
pushes against the valve member 910, which urges the valve member
910 toward the closed condition. Flow passing from the outlet
portion 904 to the inlet portion 902 (e.g., in the case of user
exhalation) pushes against the valve member 910 to urge it toward
the inlet portion 902 and the opened condition.
[0205] The valve member 910 preferably is cantilevered from the
inside surface of the wall forming the flow passage. The valve
member 910 may be able to flex toward or away from the closed
condition by bending adjacent its connection with the wall or by
bending along its length. In some configurations, the valve member
910, when in the opened condition (i.e., extending into the flow
path between the inlet and the outlet), the valve member 910 can
bend toward the user during inhalation and/or toward the flow
generator during exhalation. In the illustrated flow diversion
device 900, the secured end of the valve member 910 is clamped
between two portions of the flow diversion device 900. For example,
a base of the valve member 910 may be clamped between an end
surface 914 of the inlet portion 902 and an end surface 916 of the
outlet portion 904.
[0206] With reference to FIG. 9C, the valve member 910 may be
formed integrally with a gasket 912. The gasket 912 can be a
perimeter gasket. In some configurations, the gasket 912 only
extends a portion of the full perimeter of the flow diversion
device 900. The gasket 912 may be sandwiched between the end
surfaces 914, 916 around the circumference of the connector 900. In
the illustrated configuration, the two parts containing the end
surfaces 914, 916 of the flow diversion device 900 are secured
together by a plurality of screws 930. In other configurations, the
two portions of the flow diversion device 900 can be secured by
snap fit connection, adhesives, over-moulding, ultrasonic welding
or the like. In some applications, the valve flap 910 is a
removable component.
[0207] Where the valve flap 910 displaces by bending along its
length, the land or valve seat 920 for the port 908 preferably is
disposed on or near a plane that is spaced away from the embedded
portion of the valve member. In other words, the land or valve seat
920 is offset in a transverse direction of the illustrated passage
such that, as the valve member 910 bends to cover the port 908, a
portion of the valve member 910 toward the free end of the valve
member 910 can sit against the land 920 and substantially close the
outlet port 908. The offset advantageously allows the valve member
910 to easily cover at least a portion of the outlet port 908 by
simply bending about one bending location. In some applications,
the offset allows the valve member 910 to substantially cover the
outlet port 908 without the valve member 910 having to adopt a
convoluted shape.
[0208] In a simple arrangement, the offset is provided by a
stepback or offset 918 displaced away from the land 920. Instead of
the stepback 918, a curved surface may be provided between the base
of the valve member 910 where it embeds in the wall of the flow
diversion device 900 and the port 908. The curved surface may match
the expected curvature of the valve member 910 when it is deflected
by prevailing conditions to substantially cover the outlet port
908.
[0209] In some configurations, the flow passage cross-section in
the region of the valve member 910 is a substantially square or
rectangular cross-section and the valve member 910 comprises a
matching but slightly smaller profile (e.g., square or rectangular
shape). Preferably, a significant gap or space is provided between
at least a portion of the perimeter of the valve member 910 and the
inner surface of the wall defining the flow passage. The gap or
space provides a significant flow path through the location of the
valve 910 with the valve 910 in the open condition, as illustrated
in FIG. 9A. By way of example, with reference to FIG. 9C, the
overall flow passage of the illustrated valve can have a
cross-sectional area of about 470 mm2. The valve flap can be about
16 mm wide and about 19 mm long such that it defines an area of
about 300 mm2. Thus, the opening between the perimeter of the valve
flap and the inner surface of the wall of the flow passage can be
about 165 mm2. According to such a configuration, with the valve
910 in the open position, a substantial portion (e.g., slightly
more than 1/3) of the flow path remains unimpinged by the valve. In
some embodiments, the valve 910 may occlude about 50%, about 60%,
about 70% or about 80% of the flow path. In other words, the valve
910 may occlude between about 50% and about 80% of the flow path.
Preferably, the valve 910 may occlude between about 50% and 70% of
the flow path. In some embodiments, the valve 910 may occlude
between about 60% and about 80% of the flow path. In some
embodiments, the valve 910 may occlude between about 60% and about
70% of the flow path. In some embodiments, the valve 910 may
occlude about 65% of the flow path.
[0210] The preferred valve flap 910 is very flexible and can be
formed as a single leaf of a suitable, flexible polymeric material.
For example, the valve flap 910 in the illustrated valve can be
made from LSR silicone with a Shore A hardness of about 40. The
illustrated valve flap 910 can be moulded with a thickness of about
0.45 mm. The 0.45 mm thickness provides a sufficiently thin valve
flap, wherein the valve flap 910 had a surface dimension of about
16 mm wide by about 19 mm long. Other sizes also can be used.
[0211] The valve port 908 is located downstream of the valve flap
910. The valve port 908 may be, for example, about 5 mm downstream
to about 10 mm downstream, and preferably about 7 mm downstream, of
the valve flap 910. The illustrated port 908 is approximately
trapezoidal in perimeter shape, with the shorter of the two
parallel sides being closer to the valve flap 910. In the
illustrated embodiment shown in FIGS. 9A-9C, the port 908 has an
area of about 86 mm2, a perimeter of about 36 mm2, an overall width
of about 11 mm and an overall length of 8 mm. Thus, the area of the
port 908 may be between about 10% and about 50% of the flow path,
and most preferably between about 15% and about 25% of the area of
the flow path.
[0212] With reference now to FIG. 10A to FIG. 10D, a further flow
diversion device 1000 is illustrated. As illustrated in FIG. 10A,
the flow diversion device comprises an inlet portion 1002 and an
outlet portion 1004. The inlet and outlet portions 1002, 1004 can
have any suitable configuration and can be configured similarly to
the inlet and outlet portions 902, 904 described above.
[0213] A flow passage or bore is defined a body 1005 of the flow
diversion device 1000 from the inlet portion 1002 to the outlet
portion 1004. A central portion 1006 of the body 1005 comprises a
flow port 1008 that extends through the wall of the body 1005 of
the flow diversion device 1000. The flow path through the flow
diversion device 1000 can communicate with the surroundings through
the port 1008.
[0214] A flexible valve member 1010 extends into the flow path at a
location between the inlet to the inlet portion 1002 and the port
1008. An inner surface 1020 surrounding the port 1008 may act as a
land or valve seat for when the flow diversion device 1000 is in
the closed condition. In the closed condition, the valve member
1010 generally cuts off flow from inside the user interface 204 to
the ambient surroundings through the port 1008.
[0215] The port 1008, similar to the port 908, preferably is large
enough to enable most of an exhalation flow to pass through the
port 1008 into the ambient atmosphere. If the port 1008 is too
small in area, the exhalation flow will take a path of least
resistance around the port 1008 and go through the flow diversion
device 1000 and the conduit instead. Because in such an instance,
at least a large portion of the exhalation flow remains within the
flow diversion device and the conduit, at least a portion of the
exhalation flow likely would be rebreathed in the next inhalation.
This is undesired.
[0216] On the other hand, if the port 1008 is too large in area,
all of the exhaled gases will flow through the port 1008 to the
ambient and there will be very little of the exhaled gases
impinging upon the valve member 1010. The valve member 1010, when
not positioned over the port 1008, creates a resistance to gases
flow from the flow generator 210, 212. If the port 1008 is too
large, the flow that urges the port 1008 into a
resistance-generating position will be too small and will not be
indicative of patient breathing.
[0217] Under normal breathing conditions (e.g., a flow of about 25
L/min) and with a blower operating in a flow control mode with a
flow rate of about 15-20 L/min, it has been found that the port
1008 preferably has a cross section of about 90 mm2. In some
applications, the port 1008 can have a cross section of between
about 40 mm2 and about 250 mm2. In some applications, the port 1008
can have a cross section of between about 85 mm2 and about 180 mm2.
FIG. 11 represents various sizes of ports 1008 and the impact on
flow rates.
[0218] With respect to the valve member 1010, for the valve member
1010 to function as a non-rebreathing valve, the size of the valve
member 1010 preferably is large enough to substantially occlude the
flow path from the outlet portion 1004 to the inlet portion 1002.
If the valve member 1010 is too small, the exhalation flow will
take the least resistance path and go down the conduit. If the
exhalation flow goes down the conduit, then the exhalation flow
likely will be rebreathed on the next inhalation.
[0219] With the valve member 1010 being generally perpendicular to
the gases flow, the resistance to flow from the flow generator can
be maximized. Thus, during exahation, a larger valve member 1010
can increase the resistance to flow from the flow generator. It
currently is believed that information regarding a user's breathing
can be amplified and the controller 224 thereby can receive data
having a better resolution with a larger valve member when compared
to a smaller valve member or with a valve member without a valve
seat when compared to a valve member with a valve seat. The valve
member 1010, however, desirably is small enough to allow
substantially free movement of the valve member 1010. In the
illustrated configuration, the valve member 1010 does not have a
seat in the flow path from the flow generator to the interface.
[0220] In the illustrated configuration, the port 1008 is covered
with a shroud 1040. The shroud 1040 extends around at least a
portion of the outer surface of the body 1005. In some
configurations, the body 1005 is generally cylindrical and the
shroud 1040 extends around a portion of the circumference of the
body 1005. In the illustrated configuration, the shroud 1040
extends around an outer surface of the central portion 1006 of the
body 1005. The shroud 1040 has a first end and a second end 1041
that define openings 1042. Gases passing out of the port 1008 pass
through a passage defined between the illustrated shroud 1040 and
the central portion 1006 of the body 1005 and are exhausted to the
ambient atmosphere through the openings 1042. Similarly, air can
pass through that same passage, into the port 1008 and into the
flow diversion device 900.
[0221] Other valve constructions also are possible without
departing from the general scope of the present invention. In some
configurations, valves can be used that are similar to those
described in U.S. Provisional Patent Application No. 61/504,295,
filed Jul. 4, 2011 with Attorney Docket No. FPHCR.270PR2, which is
hereby incorporated by reference in its entirety. In addition, the
Quattro anti-asphyxia valve by ResMed has suitable characteristics,
although not as good as the valve described with reference to FIGS.
9A to 9C. Other valve constructions may be devised that meet the
desired functional criteria for opening and closing with respect to
the prevailing conditions in a stable manner. These preferred
functional aspects will be apparent from the discussion below with
reference to FIGS. 5, 6, 7 and 8.
Example Tests of Values and Systems
[0222] Behaviour of systems that have been arranged and configured
in accordance with certain features, aspects and advantages of the
present invention (e.g., utilising the valve described with
reference to FIGS. 9A-9C and also an alternative commercially
available valve) are described below. The tests demonstrated
comparative performance of the valves and comparative performance
of different control methods when used with the valves. Tests were
conducted using a test setup as illustrated in FIG. 4.
[0223] The test setup illustrated in FIG. 4 comprises a CPAP flow
generator 402 that is connected to deliver flow to an artificial
lung 404. The CPAP flow generator 402 used in the experiments
described herein was a Fisher & Paykel ICON Auto available from
Fisher & Paykel Healthcare Limited, Auckland, New Zealand. The
CPAP flow generator 402 featured modified software that was
modified to remove lower limits. The artificial lung was an ASL5000
available from Ingmar Medical Ltd of Pittsburgh, USA.
[0224] The CPAP flow generator 402 was connected to the artificial
lung 404 via a delivery conduit 406. The delivery conduit 406 was
the 1.8 m supply hose supplied with the ICON Auto.
[0225] Between the user end of the delivery conduit 406 and the
inlet port of the artificial lung were, in series, the valve 408
being tested, a bias flow connector 410, and a connector 412
including a port 414 for measuring characteristics of the gases
stream. The bias flow connector 410 was an elbow from an HC407
nasal mask available from Fisher & Paykel Healthcare Limited.
In the illustrated setup, the port 414 of the connector 412 was
connected to a data acquisition unit 416 for measuring pressure at
the entrance to the artificial lung. Additional data collected by
the CPAP flow generator 402, including delivered flow, was supplied
to a data interface box 418 and on to data acquisition unit 416.
The collected data from data acquisition unit 416 was provided to a
computer 420 or other suitable processing unit. The computer 420
can be connected to the artificial lung 404 to provide control
signals to the artificial lung 404 and to the CPAP flow generator
402 to provide control signals to the CPAP flow generator 402.
Testing of Valve Characteristics Under Different Control Modes
[0226] In a first set of tests, the apparatus shown in FIG. 4 was
used to consider the characteristics of the valve shown in FIGS.
9A-9C and the characteristics of an existing anti-asphyxia valve.
These tests show both comparative performance of the valves and
comparative performance of the control methods. The existing
anti-asphyxia valve is supplied with the ResMed Quattro Full Face
User Interface (available from ResMed Pty Limited of Sydney,
Australia). The tests demonstrate some of the advantages of the
preferred control (i.e., the control as used with either valve) and
some of the advantages in this application of the valve of FIGS.
9A-9C over the ResMed anti-asphyxia valve.
[0227] For each valve, two series of tests were conducted. For each
test in each series, the artificial lung was set up to run through
a breath test sequence including: (1) four breaths at 250 ml tidal
volume; (2) pause; (3) four breaths at 500 ml tidal volume; (4)
pause; (5) four breaths at 750 ml tidal volume; (6) pause; (7) and
four breaths at 1000 ml tidal volume. All breaths were sinusoidal
at 15 breaths per minute with a 1:1 expiration to inspiration
ratio.
[0228] In the first test series, the CPAP flow generator 402 was
controlled to run at a constant motor speed for the duration of
each test. That is, the device ran without pressure or flow
feedback control. The device 402 was set to run at a speed at which
the delivered average flow was expected to be low and the valve 408
open. The breath sequence was played and the behaviour of the valve
408 was noted. The speed was increased by 1000 rpm and the process
was repeated. This cycle was continued, increasing the speed by
1000 rpm each time until the valve 408 reached a stable closed
state. Then the process was repeated, reducing the speed by 1000
rpm in each of the test sequences until the valve 408 reached a
stable open state. At each of the tests, the behaviour of the valve
408, the average mask pressure and the average flow rate were
recorded.
[0229] For the valve illustrated in FIGS. 9A-9C, the results of
this sequence of tests are illustrated in FIGS. 5A-5C. These
figures are discussed in more detail below. For the ResMed Quattro
valve, the results of this sequence of tests is illustrated in
FIGS. 6A-6C. These results are discussed in more detail below.
[0230] In the second sequence of tests on each valve 408, the CPAP
flow generator 402 was run in a pressure feedback mode. The first
test in the sequence had the set pressure for the flow generator at
1 cm H2O. Subsequent tests were conducted at increasing pressures,
increasing the set pressure by 0.5 cm H2O for each subsequent test.
Once the valve 408 reached a stable closed state, the process was
repeated in reverse, reducing the set pressure by 0.5 cm H2O for
each subsequent test. For each test, the state of the valve 408,
the average flow and the average pressure were recorded. The
results of this testing for the valve of FIGS. 9A-9C are
illustrated in FIGS. 5D-5F. The results of this testing for the
ResMed Quattro valve are illustrated in FIGS. 6D-6F.
Test Results for Valve of FIGS. 9A-9C
[0231] FIGS. 5A to 5C illustrate the behaviour of the valve 408
shown in FIGS. 9A-9C (i.e., the flow diversion device 900) under
constant flow generator speed conditions. This illustrates, for
example, the way the valve 408 will behave when the flow generator
402 is controlled with slow feedback based on average flow. The
flow generator 402 will not react to the breathing cycle changes in
flow or pressure and, over a sequence of breaths, will maintain
essentially a constant flow generator speed. The instantaneous flow
and pressure will fluctuate as the user breathes. FIG. 5B, which
indicates the measured pressure, and FIG. 5C, which indicates the
measured flow, both represent the average of the pressure or flow
over the breaths of the test. The valve state behaviour in FIG. 5A
was by observation. Either the valve 408 remained closed across all
of the sequence of breaths, the valve 408 remained open across all
of the sequence of breathes, or was instable and moved between the
open and closed states in response to the breathing cycle.
[0232] The sequence of tests is indicated by the sequence of data
points 501, 502, 504, 506, 508, 510, 512, 514, 516, 518. For
simplicity, this sequence of data points is indicated by the same
reference numerals in each of FIGS. 5A, 5B and 5C.
[0233] In FIG. 5A, it can be seen that the behaviour of the
illustrated valve, when commencing in the open state, remains
stable in the open state at blower speeds of 3000, 4000 and 5000
rpm (data points 501, 502 and 504 in FIG. 5A). At these blower
speeds, the pressure delivered to the artificial lung remains below
about 1.5 cm H2O (data points 501, 502 and 504 in FIG. 5B). Also
within this range, the delivered flow at 3000 rpm was above about
15 litres per minute and the delivered flow at 5000 rpm above about
30 litres per minute. Accordingly, the illustrated valve provides
for substantial adjustment of the delivered flow to compensate for
large bias flow vents or leaks at the mask without excessively
increasing the delivered sub-therapeutic pressure and with the
valve staying stable in the open position.
[0234] With the illustrated valve of FIGS. 9A-9C and the
illustrated flow generator, when reducing the output of the flow
generator in response to user awakening, and subsequently entering
the constant average flow (i.e., constant rotor speed) mode, the
initial flow generator speed should be at or below 4000 rpm so that
the valve exhibits the initial stable behaviour (see, for example,
the transition between data points 516 and 518 in FIG. 5A).
[0235] FIGS. 5D-5F illustrate the results of testing in the
pressure feedback mode. As discussed above, the pressure feedback
mode is entered to provide therapeutic pressures once the user is
asleep. One preferable characteristic of the valve illustrated in
FIGS. 9A-9C is to exhibit stable closed behaviour under pressure
feedback control at a set pressure that is close to the average
mask pressure delivered immediately prior, when the valve behaviour
was stable open under constant rotor speed control.
[0236] With reference to data points 520 and 524, the valve of
FIGS. 9A-9C exhibits unstable behaviour with the pressure feedback
control at 1 cm H2O set pressure whether commencing at this set
pressure or returning to this set pressure from higher set
pressure. However, as indicated by data point 522, at 1.5 cm H2O
set pressure, the valve exhibits stable behaviour. At this set
pressure, the system delivered an average pressure of about 1.7 cm
H2O and delivered an average flow of about 20 litres per
minute.
Performance of the Valve of FIGS. 9A-9C in Combination with
Preferred Control Modes
[0237] The delivered average mask pressure with the valve stable
and closed (e.g., about 1.7 cm H2O) is less than about 1 cm H2O
higher than the delivered average mask pressure under the constant
rotor speed control with the valve stable open (data points 501,
502 and 504 in FIG. 5B). The delivered average flow at this setting
is within the range of the delivered average flow indicated by data
points 501, 502 and 504 in FIG. 5C.
[0238] Data point 522 relates to the valve stable and closed (i.e.,
pressure mode) and generates a mask pressure of about 1.7 cm H2O.
Data point 518 relates to the valve stable and open (i.e., speed
mode) and generates a mask pressure of about 0.9 cm H2O. The
delivered average mask pressure with the valve stable and closed
(about 1.7 cm H2O) can be less than about 1 cm H2O higher than the
delivered average mask pressure under the constant rotor speed
control with the valve stable open (i.e., data points 501, 502 and
504 in FIG. 5B). The delivered average flow at this setting can be
within the range of the delivered average flow indicated by data
points 501, 502 and 504 in FIG. 5C.
[0239] Accordingly, using the illustrated valve and flow generator
control combination, the system may move from the sub-therapeutic
mode, with a flow generator speed of about 4000 rpm delivering
about 0.9 cm H2O, average mask pressure and about 25 litres per
minute average flow, to a therapeutic mode, with pressure feedback
control, delivering about 1.7 cm H2O average mask pressure and
about 20 litres per minute average flow.
[0240] When switching from the therapeutic delivery mode to the
sub-therapeutic delivery mode (e.g., in response to user
awakening), one could expect generally the same transition between
system conditions, but in reverse.
Test Results for ResMed Anti-Asphyxia Valve
[0241] FIGS. 6A to 6C illustrate the behaviour of the ResMed
Quattro valve under constant flow generator speed. This illustrates
the way the valve will behave where the flow generator is
controlled with slow feedback based on average flow, such as in the
preferred sub-therapeutic mode according to certain features,
aspects and advantages of the present invention. FIG. 6A
illustrates the observed valve state in each of the tests. FIG. 6B
indicates the average measured pressure in each of the tests and
FIG. 6C illustrates the average measured flow in each of the tests.
The sequence of the tests is indicated by the sequence of data
points 600, 602, 604, 606, 608, 610, 612, 614, 616. For simplicity,
this sequence of data points are indicated by the same reference
numerals in each of the FIGS. 6A, 6B and 6C.
[0242] From FIG. 6A, it can seen that the behaviour of the ResMed
Quattro valve when commencing in the open state remains stable in
the open state at blower speeds of 3000 rpm, 4000 rpm, 5000 rpm
(data points, 600, 602 and 604). At these blower speeds, the
pressure delivered to the artificial lung is approximately 1 cm H2O
(data points 600, 602 and 604 in FIG. 6B). The delivered flow at
4000 rpm is about 20 litres per minute and the delivered flow at
5000 rpm is about 30 litres per minute. However, the delivered flow
at 3000 rpm is only about 10 litres per minute, which is lower than
desirable. Accordingly, the average flow rate across the range of
flow generator speed at which the ResMed Quattro valve is stable is
approximately 10 litres per minute to 30 litres per minute compared
to approximately 15 litres per minute to 35 litres per minute for
the valve of FIGS. 9A-9C.
[0243] Referring to FIGS. 6D to 6F, these figures illustrate the
results of testing in the pressure feedback mode. With reference to
data points 620, 622, 624, 626, the ResMed Quattro valve exhibits
unstable behaviour with the pressure feedback control at a 1 cm H2O
set pressure whether commencing at this set pressure or returning
to this set pressure from a higher set pressure. The valve remains
unstable at 1.5 cm H2O set pressure (data points 622 and 626 in
FIG. 6A). The valve exhibits stable behaviour once the set pressure
reaches 2 cm H2O (data point 624 in FIG. 6A). With a set pressure
of 2 cm H2O, the delivered average pressure was about 2.2 cm H2O
(data point 624 in FIG. 6E). At 2 cm H2O, the delivered average
flow rate was about 15 litres per minute (data point 624 in FIG.
6F).
Performance of the ResMed Valve in Combination with the Preferred
Control Mode
[0244] The delivered average mask pressure with the ResMed Quattro
valve at the lowest set pressure for stable closed valve behaviour
is approximately 1.2 cm H2O above the delivered average mask
pressure under constant speed control with the valve open. The
delivered average flow rate is at the lower end of the average flow
rate range using motor speed control.
[0245] Using this valve and flow generator combination, one could
expect to transition from the sub-therapeutic mode (i.e., with a
flow generator speed of about 4000 rpm), delivering about 1 cm H2O
average mask pressure and about 20 litres per minute average flow,
to a therapeutic mode with pressure feedback control, delivering
about 2.2 cm H2O mask pressure and about 15 litres per minute
average flow. When switching from a therapeutic delivery to the
sub-therapeutic delivery, one could expect the same transition
between system conditions but in reverse.
Comparison of FIGS. 9A-9C Valve Performance with ResMed Valve
Performance
[0246] Both the valve of FIGS. 9A-9C and the ResMed valve provide
adequate performance in conjunction with the preferred
control--switching from an open loop control to a pressure feedback
control--at the transition from sub-therapeutic to therapeutic
modes. In each case, the delivered flows at the transition are
sufficient and the pressure step is reduced compared with the same
transition under pressure feedback only control. However, the valve
of FIGS. 9A-9C provided a lower step in mask pressure (e.g., about
0.8 cm H2O) when compared with the ResMed valve (e.g., about 1.2 cm
H2O) and provided a greater flow at both the sub-therapeutic and
the therapeutic pressures around the transition.
Comparison Using the Example Control Method in a Sequence of
Simulated Breaths
[0247] The effect of particular valve behaviour can be seen in the
results of the additional test sequence executed on each of the
ResMed Quattro valve and the valve of FIGS. 9A-9C. According to the
second test sequence, the artificial lung was set up to simulate
continuous breathing at 1000 ml tidal volume, with all breaths
sinusoidal at 15 breaths per minute with a one-to-one expiration to
inspiration ratio. The flow generator was controlled to commence
with a constant speed of 3000 rpm. After a period of time, the flow
generator was switched to a pressure feedback mode with a set
pressure of 1.5 cm H2O. Throughout the test, the valve behaviour
was observed and the delivered flow (i.e., the flow leaving the
flow generator) and the pressure at the artificial lung were
recorded.
[0248] FIG. 7A plots the pressure and flow versus time for the
ResMed Quattro valve. FIG. 7B plots the pressure and flow versus
time for the valve of FIGS. 9A-9C.
[0249] Referring in particular to FIG. 7A, the pressure plot shows
a first portion 708 while the flow generator is in constant speed
mode and a second portion 714 after the flow generator transitions
to pressure feedback mode with a set pressure of 1.5 cm H2O at time
702. With the flow generator in constant speed mode at portion 708,
the pressure fluctuates with the sinusoidal breathing pattern
imposed by the artificial lung. After the transition to pressure
feedback mode, the pressure feedback control is trying to assert
control over the pressure and reduces the influence of the imposed
breathing.
[0250] In the flow plot, portion 710 precedes the transition 702
and portion 712 is after the transition 702. In portion 710, the
flow fluctuates with user breathing approximately opposing the
fluctuation of pressure. As the artificial lung exhales, the
pressure rises and the delivered flow reduces. As the artificial
lung inhales, the pressure drops and the delivered flow
increases.
[0251] After the transition 702, the delivered flow 712 remains in
phase with the user breathing. The delivered pressure 714 is more
complex, as the feedback control tries to respond to the
instantaneous pressure.
[0252] One feature of these plots is that the set pressure of 1.5
cm H2O has not been sufficient to bring this valve into a stable,
closed condition. This is illustrated by the highlighted spikes 704
in the pressure plot and the highlighted irregularity 706 in the
flow plot. The spike 704 and the irregularity 706 occur in each
breath in the sequence after entering the pressure feedback mode.
The spikes and irregularities indicate that the valve is unstable
at 1.5 cm H2O and correspond with the valve snapping shut. The
valve then reopens at some point in the cycle and snaps shut again
at the start of the next exhalation.
[0253] FIG. 7B shows similar plots for the valve illustrated in
FIGS. 9A-9C. Again, the plots include portions 720, 722 prior to a
transition 724 to the pressure feedback control with a set pressure
of about 1.5 cm H2O. For this valve, the difference in average
pressure between the period 720 prior to the transition 724 and the
period 726 after the transition 724 is lower than the difference in
average pressure during the period 708 and average pressure in
period 714 for the ResMed Quattro valve. Despite this, the valve of
FIGS. 9A-9C has entered a stable closed condition at moment 728
and, as indicated at 730, there are no conspicuous spikes in the
pressure plot and no significant discontinuity peaks or
irregularities of the flow curve. This corresponds with the
observation that the valve had entered a stable, closed
condition.
[0254] Thus, the valve of FIGS. 9A-9C outperforms the ResMed
anti-asphyxia valve by achieving stable closed behaviour at a lower
delivered pressure and with a smaller increase in system conditions
from a stable open condition.
[0255] FIGS. 8A and 8B illustrate different characteristics under
open loop control and under pressure feedback control for the valve
of FIGS. 9A-9C. FIG. 8A illustrates features that correspond to
valve instability. FIG. 8B illustrates the effect of pressure
feedback on flow fluctuation. Both FIG. 8A and FIG. 8B relate to
the valve in the closed state. The sequence was run firstly with
the flow generator controlled to have a constant rotor speed of
5000 rpm. In the second test, the flow generator was operated in a
pressure feedback mode with a set pressure of 1.5 cm H2O.
[0256] The behaviour of the valve of FIGS. 9A-9C was observed in
the two modes. Furthermore, the flow and pressure were recorded
throughout the tests.
[0257] FIG. 8A provides flow and pressure versus time plots for the
test conducted with open loop control and with the CPAP speed
controlled at 5000 rpm. FIG. 8B shows the pressure and flow versus
time plots with pressure feedback control and with the CPAP flow
generator pressure set to about 1.5 cm H2O.
[0258] FIG. 8A illustrates that the illustrated valve is becoming
unstable with a blower speed at 5000 rpm having previously been
higher. Instability in FIG. 8A is indicated by the pressure spike
802 becoming apparent in the early part of expiration in each
breath.
[0259] This can be compared with the performance of the valve
recorded in FIG. 8B in the pressure control mode. In the pressure
control mode, with a set pressure of 1.5 cm H2O, there are no large
transient peaks in the pressure curve, indicating that the valve is
stable. However, the peak to peak flow fluctuation is much greater
than the flow fluctuation in the open loop control mode illustrated
in FIG. 8A.
Overview of Operating Characteristics of Flow Diversion Device and
Control Techniques
[0260] Desirably, the flow diversion device and the control of the
flow generator work in cooperation with one another. In some
configurations, with the flow generator not generating flow, the
user will inhale ambient air through the port of the flow diversion
device and exhale air mostly out to ambient through the port.
During exhalation, some small portion of the exhaled gases may push
the valve member to bend the valve member downward toward the flow
generator and a small portion of the exhaled gases may travel down
the conduit beyond the valve member.
[0261] In some configurations, with the flow generator generating a
sub-therapeutic flow of gases (i.e., flow control mode), the user
will inhale mostly ambient air through the port while the flow from
the flow generator bends the valve slightly toward the user and, as
such, provides a small portion of flow to the user. During
exhalation, most of the exhalation passes through the port with
some portion of the exhalation moving the valve member back toward
the flow generator, which slows the flow from the flow generator.
Dependent upon the exhalation flow from the user, the flow rate
from the user may vary. Thus, the varying flow rate may be
indicative of the user breathing, which enables the controller 224
to monitor breathing patterns and identify events (e.g.,
apnea).
[0262] In some configurations, with the flow generator generating a
therapeutic flow of gases (i.e., pressure control mode), during
inhalation, the valve member overlies the port and the user
breathes gases from the flow generator. During exhalation, the user
breathes against the flow from the flow generator and the valve
member overlies the port.
[0263] Although certain features, aspects and advantages of the
present invention have been described in terms of a certain
embodiments, other embodiments apparent to those of ordinary skill
in the art also are within the scope of this invention. Thus,
various changes and modifications may be made without departing
from the spirit and scope of the invention. For instance, various
components may be repositioned as desired. In addition, certain
features, aspects and advantages of the invention have been
described with reference to breathing gases supply devices
particularly for use in the treatment of obstructive sleep apnea.
PAP devices also are used in the treatment of other conditions,
such as COPD, and may be used for the supply of mixed gases other
than air, for example, a mixture of air and oxygen, or a mixture of
nitrogen and oxygen or the like. The method and apparatus of the
present invention may be equally applied to gas supply apparatus
for use in these other treatments. Moreover, not all of the
features, aspects and advantages are necessarily required to
practice the present invention. Accordingly, the scope of the
present invention is intended to be defined only by the claims that
follow.
* * * * *