U.S. patent application number 15/952988 was filed with the patent office on 2018-08-23 for mask and flow generator system.
The applicant listed for this patent is ResMed Limited. Invention is credited to Renee Frances FLOWER, Philip Rodney KWOK.
Application Number | 20180236197 15/952988 |
Document ID | / |
Family ID | 39156745 |
Filed Date | 2018-08-23 |
United States Patent
Application |
20180236197 |
Kind Code |
A1 |
FLOWER; Renee Frances ; et
al. |
August 23, 2018 |
MASK AND FLOW GENERATOR SYSTEM
Abstract
A system for delivering a pressurized flow of breathable gas to
a patient includes a patient interface configured to contact the
patient's head. The patient interface has a frame and a cushion
supported by the frame. The cushion is configured to sealingly
connect the patient interface to the patient's face and form a
chamber between the frame and the patient's face. The patient
interface also has an inlet port in the frame to receive the
pressurized flow of breathable gas. The system further includes a
flow generator mounted on the patient interface. The flow generator
is configured to generate the pressurized flow, capable of creating
a pressure of about 2-40 cm H.sub.2O in the chamber. A flow
generator housing houses the flow generator and is configured to
reduce a transmission of vibration and/or noise generated by the
flow generator to the patient interface. At least one support arm
extends from the flow generator housing to the frame of the patient
interface. The at least one support arm is connected to the frame
of the patient interface by a soft joint.
Inventors: |
FLOWER; Renee Frances;
(Sydney, AU) ; KWOK; Philip Rodney; (Sydney,
AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ResMed Limited |
Bella Vista |
|
AU |
|
|
Family ID: |
39156745 |
Appl. No.: |
15/952988 |
Filed: |
April 13, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12438899 |
Jun 1, 2009 |
|
|
|
PCT/AU2007/001325 |
Sep 6, 2007 |
|
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15952988 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 2205/42 20130101;
A61M 2205/8206 20130101; A61M 2209/088 20130101; A61M 2016/0027
20130101; A61M 2205/3592 20130101; A61M 16/06 20130101; A61M
16/0638 20140204; A61M 2205/3569 20130101; A61M 16/0069 20140204;
A61M 16/0066 20130101; A61M 2205/3368 20130101; A61M 16/0683
20130101; A61M 2016/0033 20130101; A61M 2205/0238 20130101; A61M
2205/502 20130101; A61M 16/0858 20140204 |
International
Class: |
A61M 16/06 20060101
A61M016/06; A61M 16/00 20060101 A61M016/00; A61M 16/08 20060101
A61M016/08 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 7, 2006 |
AU |
2006904900 |
Oct 27, 2006 |
AU |
2006905967 |
Claims
1. A system for delivering a pressurized flow of breathable gas to
a patient, the system comprising: a patient interface configured to
contact the patient's head, the patient interface comprising a
frame, a cushion supported by the frame and configured to sealingly
connect the patient interface to the patient's face and form a
chamber between the frame and the patient's face, and an inlet port
in the frame to receive the pressurized flow of breathable gas; a
flow generator mounted on the patient interface, the flow generator
being configured to generate the pressurized flow, capable of
creating a pressure of about 2-40 cm H.sub.2O in the chamber; a
flow generator housing to house the flow generator, the flow
generator housing being configured to reduce a transmission of
vibration and/or noise generated by the flow generator to the
patient interface; and at least one support arm extending from the
flow generator housing to the frame of the patient interface, the
at least one support arm being connected to the frame of the
patient interface by a soft joint.
2. A system according to claim 1, wherein at least a portion of the
flow generator housing is mounted on the frame of the patient
interface.
3. A system according to claim 1, wherein the patient interface
includes a headgear and the flow generator housing is mounted to
the headgear.
4. A system according to claim 1, wherein the flow generator
housing comprises a vibration dampening and/or absorbing
material.
5. A system according to claim 1, wherein the flow generator
housing and the frame of the patient interface comprise a vibration
dampening material.
6. A system according to claim 1, further comprising a user
interface to control the flow generator.
7. A system according to claim 6, wherein the user interface is
configured to supply power to the flow generator.
8. A system according to claim 6, wherein the user interface is
configured to control the flow generator through an electrical
connection.
9. A system according to claim 6, wherein the user interface is
configured to control the flow generator through a wireless
connection.
10. A system according to claim 1, wherein an outlet of the flow
generator housing and the inlet port of the frame are connected by
another soft joint.
11. A system according to claim 6, wherein the user interface is
configured to receive signals from a pressure sensor.
12. A system according to claim 11, wherein the pressure sensor is
provided at an outlet of the flow generator.
13. A system according to claim 11, wherein the pressure sensor is
provided in the frame of the patient interface.
14. A system according to claim 1, wherein the flow generator
comprises a brushless DC motor.
15. A system according to claim 1, wherein at least a portion of
the flow generator housing is integrally formed with the frame of
the patient interface.
16. A system according to claim 1, wherein a thickness of a wall of
the flow generator housing is about 0.5-2.5 mm.
17. A system according to claim 1, wherein a thickness of a wall of
the flow generator housing is about 1.0-2.0 mm.
18. A system according to claim 1, wherein a thickness of a wall of
the flow generator housing is about 1.5 mm.
19. A system according to claim 6, wherein the user interface
comprises an LCD, a keypad, a microcontroller, a motor controller,
a user interface control, an audible device, and/or an LED.
20. A system according to claim 1, wherein the frame of the patient
interface and the cushion are formed of the same material.
Description
[0001] This application is a continuation of U.S. application Ser.
No. 12/438,899, filed Feb. 25, 2009, which is the U.S. national
phase of International Application No. PCT/AUI2007/001325, filed
Sep. 6, 2007, which designated the U.S. and claims priority to
Australian Provisional Applications 2006904900 and 2006905967,
filed Sep. 7, 2006 and Oct. 27, 2006, respectively, the entire
contents of which are incorporated herein by reference. WO
2005/028009 is also incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present invention relates to respiratory therapies,
including but not limited to, Continuous Positive Airway Pressure
(CPAP), bi-level and ventilation therapies. The present invention
also relates to a mask and flow generator system that delivers a
flow of pressurized breathable gas, e.g. air, to a patient for
treatment of various breathing disorders. Tue present invention
further relates to a system in which the flow generator is
incorporated with the mask or a headgear that supports the
mask.
2. Description of the Related Art
[0003] Obstructive Sleep Apnea (OSA) is a sleep breathing disorder
(SBD). For those who have OSA when they sleep the soft tissue in
their throat and airway relax and collapse thus blocking the airway
and preventing airflow to the lungs. This cessation of breathing,
known as an apnea, can last for up to one minute before the blood
oxygen levels reach a critical point where the patient has an
arousal and their airway reopens. Most OSA suffers do not remember
these arousals however each arousal places extra strain on a
patient's heart and destroys the quality of their sleep.
[0004] OSA is as prevalent as diabetes or asthma but is an
extremely undiagnosed condition. Studies have shown it can lead to
significant health problems if left untreated.
[0005] The treatment for OSA may include CPAP. CPAP involves the
patient wearing a nasal or facemask that delivers positive pressure
into the patients airway. This acts as a pneumatic splint and holds
the patients airway open to prevent apneas.
2.1 Mechanical Ventilation
[0006] A mechanical ventilator is a machine that generates a
controlled flow of gas into a patient's airways and is configured
to assist patients who are unable to maintain self-sufficient
respiration.
[0007] Patients generally require mechanical ventilation for three
main reasons. These include
[0008] 1. Damaged or diseased lungs;
[0009] 2. Insufficient respiratory drive;
[0010] 3. Inadequate respiratory muscles.
[0011] A mechanical ventilator essentially perfornls the role of
the medulla in that it initiates respiration and the diaphragm by
expanding and contracting the lungs. A mechanical ventilator may
also assist the patient in respiration once the patient begins
respirating.
[0012] Mechanical ventilators can be sub-categorised into invasive
and non-invasive ventilators. Invasive ventilators actually enter
the body, whereas non-invasive ventilators perform the function
external to the body.
[0013] These two sub-categories can be further sub divided into
positive and negative pressure devices, referring to the type of
pressure that is used to expand the lungs.
[0014] In negative pressure devices, a negative gauge pressure is
created external to the chest, thus drawing the chest outwards and
dilating the lungs, for example as with an iron lung.
[0015] In positive pressure devices, a positive gauge pressure is
created inside the lungs thus drawing air into the lungs.
[0016] Clinical studies have illustrated the benefits that
Non-Invasive Positive Pressure Ventilation (NIPPV) has over the
other ventilation devices. This includes significantly reducing the
number of complications such as infection, no loss of the airway
defense mechanism, and reduced need for patient sedation.
[0017] NIPPV is a suitable treatment for a wide range of diseases
and conditions. These include:
[0018] 1. Spinal cord injury;
[0019] 2. COPD;
[0020] 3. Cystic fibrosis; and
[0021] 4. Muscular dystrophy.
SUMMARY OF THE INVENTION
[0022] One aspect of the invention relates to enhancing the
treatment delivery by a device that incorporates all, or most, of
the components of a NIPPV system into a single wearable device. For
example, the mask and flow generator may be integrated into a mask
system worn by the patient. The flow generator may be incorporated
into the mask or a headgear configured to support the mask. This
aspect provides several advantages over current NIPPV systems.
[0023] Another aspect of the invention relates to a patient
interface that incorporates a flow generator and provides effective
treatment while maintaining or improving patient comfort, including
the reduction of pressure points on the patient's face and the
reduction of vibration and noise transmittance to the patient,
without obstructing the patient's vision.
[0024] According to one sample embodiment of the present invention,
a system for delivering a pressurized flow of breathable gas to a
patient comprises a patient interface configured to contact a
wearer's head, the patient interface comprising a frame, a cushion
supported by the frame and configured to sealingly connect the
patient interface to the patient's face and form a chamber between
the frame and the wearer's face, and .about.n inlet port in the
frame to receive the pressurized flow of breathable gas. A flow
generator is configured to generate the pressurized flow and is
capable of creating a pressure of about 2-40 cm H.sub.2O in the
chamber. A flow generator housing is provided to house the flow
generator. The flow generator housing is mounted on the patient
interface and configured to reduce the transmission of vibration
and/or noise generated by the flow generator to the patient
interface.
3. Advantageous Features of the Present Invention
3.1 Reduction in Mask Leakage
[0025] One advantage is a reduction in mask leakages. Leaks between
the patient's face and the mask are a significant issue for NIPPV
and may be caused by the force of the air tube pulling on the
patient interface, e.g., mask. So by removing the tube this cause
of leaks is eliminated.
3.2 Improved Treatment Accuracy
[0026] Another advantage is the improvement of treatment accuracy.
The impedance and length of the tube imparts a lag in the response
and rise time in the pressurised air from the flow generator to the
mask. This can reduce treatment efficacy, but by removing the tube
this problem is eliminated.
3.3 Increased Useability
[0027] Still another advantage is that the system is easier to use
and also increases mobility of the patient while they are wearing
the device, making it suitable for many applications.
3.4 Reduction in Functional Dead Space
[0028] An even further advantage of the present invention
associated with the removal of the air tubing is a reduction in the
functional dead space of the mask. Functional dead space is defined
as the volume of exhaled air that is trapped within the system and
that the patient subsequently re-breathes. It is desirable that
functional dead space is kept within a safe range, or in the most
extreme cases this could lead to the eventual patient suffocation.
Current techniques to reduce functional dead space involve
minimizing internal volume of the mask to minimize the amount of
CO.sub.2 that is re-breathed and maximising the vent size and thus
air flow through the mask to flush out the trapped CO.sub.2. Part
of the CO.sub.2 that is re-breathed by the patient comes from the
exhaled air that is breathed back into the tube. By removing the
tube this reduces the physical volume that is available to trap
CO.sub.2 and hence reduces functional dead space. This has
implications for mask design. The first implication is that the
internal volume of the mask can be made larger to increase the
range of fit for each mask. The second implication is that this
could lead to reduced flow requirements. If less CO.sub.2 is
trapped in the mask, then the required flow rate to remove this
CO.sub.2 is less. Reducing the flow rate will lead to a reduction
in noise created as air rushes through the vents, reduce the power
requirements of the pump, and increase patient comfort.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Sample embodiments of the invention will be described below
with reference to the attached drawings, in which:
[0030] FIG. 1 schematically illustrates a ventilator mask and
system configuration according to the present invention;
[0031] FIG. 2 schematically illustrates a first sample embodiment
of a ventilator mask and system according to the present
invention;
[0032] FIG. 3 schematically illustrates a second sample embodiment
of a ventilator mask and system according to the present
invention;
[0033] FIG. 4 schematically illustrates a third sample embodiment
of a ventilator mask and system according to the present
invention;
[0034] FIG. 5 schematically illustrates a fourth sample embodiment
of a ventilator mask and system according to the present
invention;
[0035] FIG. 6 schematically illustrates a fifth sample embodiment
of a ventilator mask and system according to the present
invention;
[0036] FIG. 7 schematically illustrates a sixth sample embodiment
of a ventilator mask and system according to the present
invention;
[0037] FIGS. 8A and 8B schematically illustrate a seventh sample
embodiment of a ventilator mask and system according to the present
invention;
[0038] FIGS. 9-9I schematically illustrate a sample embodiment of a
mask having a flow generator incorporated therein, wherein
[0039] FIG. 9A schematically illustrates a front view of a sample
embodiment of a mask according to the present invention;
[0040] FIG. 9B schematically illustrates a bottom view of a sample
embodiment of a mask according to the present invention;
[0041] FIG. 9C schematically illustrates a rear view of a sample
embodiment of a mask according to the present invention;
[0042] FIG. 9D schematically illustrates a top view of a sample
embodiment of a mask according to the present invention;
[0043] FIG. 9E schematically illustrates a bottom view of a cover
for a flow generator of a mask according to FIGS. 9A-9D;
[0044] FIG. 9F schematically illustrates a side view of the cover
of FIG. 9E;
[0045] FIG. 9G schematically illustrates a front view of the cover
of FIGS. 9E and 9F;
[0046] FIG. 9H schematically illustrates a rear view of the cover
of FIGS. 9E-9G;
[0047] FIG. 9I schematically illustrates the sample embodiment of
the mask of FIGS. 9A-9D including the cover of FIGS. 9E-9H;
[0048] FIG. 10 schematically illustrates a mask and flow generator
according to a sample embodiment of the present invention;
[0049] FIG. 11 schematically illustrates the frequency output from
a single blade impeller;
[0050] FIG. 12 schematically illustrates the frequency output from
a three blade impeller;
[0051] FIG. 13 schematically illustrates broad band noise from a
centrifugal fan;
[0052] FIG. 14 schematically illustrates total noise produced by a
centrifugal fan;
[0053] FIG. 15 schematically illustrates a vibration model;
[0054] FIG. 16 schematically illustrates the loss coefficient
versus the Young's modulus for various materials;
[0055] FIG. 17 schematically illustrates a mask and flow generator
according to a sample embodiment of the present invention;
[0056] FIG. 18 schematically illustrates a pump of a flow generator
according to a sample embodiment of the present invention;
[0057] FIG. 19A illustrates an exemplary orifice plate for an
obtrusive-flow sensor usable with sample embodiments of the present
invention;
[0058] FIG. 19B schematically illustrates operation of an
obtrusive-flow sensor usable with sample embodiments of the present
invention;
[0059] FIGS. 20 and 21 schematically illustrate a mask and flow
generator according to a sample embodiment of the present
invention;
[0060] FIGS. 22-26 schematically illustrate a mask and flow
generator according to another sample embodiment of the present
invention; and
[0061] FIG. 27 schematically illustrates a flow generator housing
according to another embodiment of the present invention.
DETAILED DESCRIPTION
4. System Design
[0062] Referring to FIG. 1, a NIPPV system according to the present
invention can generally be divided into two components. The first
component is the user interface 8. The user interface 8 houses
electrical components and allows the user 1 to control the system.
The second component is the patient interface 2. The patient
interface 2 is configured to house a flow generator 6, e.g., a
pump, configured to generate a pressurised airflow in a mask 4 and
deliver the pressurized flow into the user's airways. It should be
appreciated that the mask 4 may be a nasal mask or a full face
mask.
[0063] A power supply connector 10 may be provided to the user
interface 8 to provide power to the user interface 8. The power
supply connector 10 may also be configured to charge a rechargeable
battery of the user interface 8.
[0064] The patient interface 2 may also include a headgear 12
configured to secure the mask 4 to the patient's face so that the
mask 4 forms a substantially leak proof seal with the patient's
face.
[0065] An electrical connector 14 may be provided between the user
interface 8 and the patient interface 2. Electrical signals may be
provided between the user interface 8 and the patient interface 2
by the electrical connector 14. As shown in FIG. 1, the user
interface 8 may be secured to the user's clothing, e.g., a belt. It
should be appreciated however that the user interface 8 may be
configured to be attached to the user 1 in any manner, for example,
by a strap or clip.
[0066] The user interface 8 may include a programmable logic
controller, or microcontroller, configured to control the operation
of the flow generator 6. User controls, such as buttons, dials,
etc., may be provided to allow the user to operate the user
interface 8. The user interface 8 may include, for example, a
display, such as a graphic LCD, a keypad, a motor control, a user
interface control, a power supply, an indicator or alarm, such as
an audible buzzer and/or LED's.
4.1 First System Configuration Sample Embodiment
[0067] Referring to FIG. 2, a NIPPV system according to one sample
embodiment of the present invention includes a user interface 8
connected to a flow generator 6 by an electrical connector 14. The
headgear 12 may include a headgear power supply support 20 that
incorporates a power supply for the flow generator 6. The power
supply may be, for example, a battery or batteries. The mask 4 is
connected to the flow generator 6 by a tube or conduit 16. A
pressure sensor 18 may be provided in the mask 4 to provide signals
to the user interface 8. The conduit 16 may include a wire or wires
for transmitting signals to and from the user interface 8 and the
mask 4.
4.2 Second System Configuration Sample Embodiment
[0068] As shown in FIG. 3, another sample embodiment of the present
invention includes a mask 4 configured to engage the face of the
patient 1. A headgear 12 is configured to support the mask 4 on the
patient's face. A flow generator 6 is incorporated into the mask 4,
as will be described in detail below. A user interface 8 is
configured to be attached to the patient 1, or the patient's
clothing. An electrical connector 14 may be provided between the
user interface 8 to provide signals to and from the flow generator
6 to control operation of the flow generator. A pressure sensor 18
may be provided in the mask 4 to provide signals to the user
interface 8. The user interface 8 may control operation of the flow
generator 6 using signals received from the pressure sensor 18. A
power supply connector 10 may be provided to connect the user
interface 8 to a power supply. It should be appreciated, however,
that the user interface 8 may operate on batteries, including
rechargeable batteries.
4.3 Third System Configuration Sample Embodiment
[0069] FIG. 4 illustrates another sample embodiment of the
invention. A flow generator 6 is incorporated into a mask 4. The
flow generator 6 and the mask 4 are supported by a headgear 12 for
sealing contact with the face of the patient 1. A pressure sensor
18 may be provided in the mask 4. A power supply connector 10 may
be provided to supply power to the flow generator 6 and the
pressure sensor 18. A wireless user interface 8 may be provided to
send and receive signals from the pressure sensor 18 and the flow
generator 6 to control operation of the flow generator 6. The
wireless user interface 8 may include an independent power
supply.
4.4 Fourth System Configuration Sample Embodiment
[0070] Referring to FIG. 5, a mask 4 is supported for sealing
contact with the face of a user 1 by a headgear 12. The headgear 12
may include a power supply support 20 that also may support a flow
generator 6. A tube or conduit 16 is configured to supply
pressurized air from the flow generator 6 to the mask 4. The
headgear power supply support 20 may support a power supply, e.g.,
a battery or batteries, for the flow generator 6. A pressure sensor
18 may be provided to provide signals indicative of the pressure of
the air delivered to the mask 4 to a wireless user interface 8. The
user interface 8 may use the signals from the pressure sensor 18 to
control the operation of the flow generator 6. The user interface 8
may include a power supply independent from the power supply for
the flow generator 6.
4.5 Fifth System Configuration Sample Embodiment
[0071] According to another sample embodiment shown in FIG. 6, a
mask 4 is supported for sealing contact with the face of a user 1
by a headgear 12. A flow generator 6 is configured to supply
pressurized breathable gas to the mask 4. A tube or conduit 16 is
configured to deliver the pressurized breathable gas from the flow
generator 6 to the mask 4. The flow generator 6 and electrical
connection 14 may be incorporated into a user interface 8. The user
interface 8 and flow generator 6 may be configured to be attached
to the user 1 or the user's clothing, such as a belt. The user
interface may receive signals from a pressure sensor 18 provided in
the mask 4 and use the signals to control the operation of the flow
generator 6. The user interface 8 may be connected to the mask 4
and the pressure sensor 18 by an electrical connector, which may be
incorporated into the conduit 16. The user interface 8 may also
receive signals from the pressure sensor 18 wirelessly.
4.6 Sixth System Configuration Sample Embodiment
[0072] As shown in FIG. 7, a user interface 8 may be supported on
an arm of a user 1, for example by a strap. The user interface 8 is
configured to receive signals from a pressure sensor 18 provided in
a mask 4 supported on the face of the user 1 by a headgear 12. A
flow generator 6 may be incorporated into the mask 4. The user
interface 8 may receive the signals from the pressure sensor 18
through an electrical connector 14, and control operation of the
flow generator 6 through the electrical connector 14. It should
also be appreciated that the user interface 8 may communicate with
the pressure sensor 18 and the flow generator 6 wirelessly. A power
supply connector 10 may be provided to supply power to the flow
generator 6.
4.7 Seventh System Configuration Sample Embodiment
[0073] Referring to FIGS. 8A and 8B, a mask 4 is supported for
sealing contact with the face of a user 1 by a headgear 12. A flow
generator 6 is incorporated into the mask 4 for delivery of
pressurized breathable gas to the mask 4. A pressure sensor 18 is
configured to provide signals indicative of the pressure at the
mask 14. The pressure sensor signals may be delivered to a user
interface 8 by an electrical connector 14. The user interface 8 is
configured to control the operation of flow generator 6 using the
pressure sensor signals. The user interface 8 may be provided in a
power supply 22. The power supply 22 may include batteries,
including, for example, rechargeable batteries. The power supply 22
may be configured to be carried by the user 1, for example in a
manner similar to a backpack. The power supply 22 may provide power
to the user interface 8 and the flow generator 6.
4.8 System Configuration Components
[0074] According to the sample embodiments described above, the
patient interface 2 may delivers the pressurised air flow into the
patient's airways and may include some or all of the following
components:
[0075] Mask, [0076] Headgear, cushion, etc.;
[0077] Flow generator housing;
[0078] Flow generator, [0079] Motor, impeller, volute;
[0080] Sensors, [0081] Pressure; [0082] Temperature; [0083] Flow;
and [0084] Volume.
[0085] The second component, i.e., the user interface 8 may be
configured to control the operation of the flow generator and may
include some or all of the following components:
[0086] Graphic LCD;
[0087] Keypad;
[0088] Micro controller;
[0089] Motor control;
[0090] User interface control;
[0091] Power supply;
[0092] Audible buzzer;
[0093] LEDs.
[0094] Referring to FIGS. 9-9I, a mask 4 according to a sample
embodiment of the invention may include a mask shell 4a and a
cushion 4b. The cushion 4b may be formed of a soft material, for
example a rubber material, such as a silicone elastomer. The
cushion is configured to sealingly contact the face of the user 1
to form an air chamber between the user's face and the mask 4. The
shell 4a may be formed of relatively hard plastic, although it
should be appreciated that the shell 4a may be formed of the same
material as the cushion 4b.
[0095] The mask shell 4a may include an extension 4c. A forehead
support may be attached to the mask extension 4c to stabilize the
mask 4 against the wearer's face once a comfortable, substantially
leak proof fit is obtained. The mask shell 4a may also include
headgear connectors 4e, including a headgear connector on the
extension 4c, to receive straps of the headgear 12 to secure the
system to the user's head.
[0096] As shown in FIGS. 9-9E, the flow generator 6 may be
incorporated into the mask 4. Referring to FIG. 9A, the flow
generator 6 may include a motor housing first part 6a and a volute
housing first part 6b. The motor housing first part 6a and the
volute housing first part 6b are configured to receive the motor
and volute of a pump of the flow generator, as discussed in more
detail below. The motor housing first part 6a and the volute
housing first part 6b may be integrally formed with the mask shell
4a. It should be appreciated, however, that the motor housing first
part 6a and the volute housing first part 6b may be formed
separately from the mask shell 4a and attached thereto, for example
by adhesive or with fasteners, as discussed in more detail
below.
[0097] Referring to FIGS. 9A and 9B, the volute housing first part
6b includes an outlet 6c that directs the airflow from the flow
generator 6 to an inlet 4d in the mask shell 4a. As shown in FIGS.
9A and 9C, the mask shell 4a may include a vent opening 4f that may
be covered by an insert (not shown) including apertures for
controllably exhausting CO.sub.2.
[0098] A motor and volute housing second part, or cover, 6f is
configured to cover the motor housing first part 6a (part of an
upper portion of a housing for the flow generator 6) and the volute
housing first part 6b (part of a lower portion of the housing for
the flow generator 6), as shown in FIGS. 9E-9H. The cover 6f
includes a volute cover part 6g (part of the lower portion of the
housing for the flow generator 6) and a motor cover part 6h (part
of the upper portion of the housing for the flow generator 6).
Apertures 6j may be provided in the volute cover part 6g, as shown
in FIGS. 9G-9H, and are configured to mate with apertures 6i formed
on the volute housing first part 6b. The cover 6f may be secured to
the motor housing first part 6a and the volute housing first part
6b by fasteners (not shown) extending through the apertures 6i and
6j formed in the motor housing first part 6a and the cover 6f,
respectively. In the fastened condition, shown in FIG. 9i, the
cover 6f and the motor housing first part 6a and the volute housing
first part 6b form a housing for the motor, the volute and the
impeller, i.e., a housing for the flow generator 6.
[0099] Although the motor housing first part 6a and the volute
housing first part 6b and the cover 6f have been described as
connected by fasteners, it should be appreciated that they may be
connected by other mechanisms, such as adhesive or by complementary
mating and locking (e.g. snapping) surfaces.
5 System Design Considerations and Approaches
5.1 User Interface
5.1.1 Design Consideration: Useability
[0100] The system of the present invention is configured to be
simple (e.g., intuitive) to use and communicate clearly with the
user, both for experienced and inexperienced users.
5.1.2 Design Approach: Useability
[0101] To provide a "user friendly system," a significant amount of
information may be required to be communicated to the user. This
functional requirement may influence the selection of mechanisms to
communicate with the user. The system of the present invention may
include at least one of the following forms of communication:
[0102] Audio, for example a piezo buzzer or some other device that
generates an audible signal; and/or
[0103] Visual, for example colored LEDs, graphical LCDs or some
other display screen.
[0104] To achieve clear communication, the communication devices
should located in logical and intuitive places. For example,
according to one sample embodiment, all of the visual communication
devices (e.g., LED's, LCD, etc.) are visible at all times while the
system is in use.
5.1.3 Design Consideration: Sanitization and Housing Durability
[0105] The user interface 8 may be worn on the patient's body.
Because the user interface may be exposed to bodily fluids it
should be void of cracks and groves that may harbor infectious
particles.
5.1.4 Design Approach: Sanitization and Housing Durability
[0106] The user interface may be designed to be void of cracks and
grooves that may harbor infectious particles. This can be achieved
using such manufacturing techniques, such as overmolding. The user
interface housing material should be resistant to oils, dusts, and
grease and the ingress of water. The user interface housing should
also be durable, with high levels of cut, fade and abrasion
resistance. All external connections of the user interface, such as
power connections and connections to the patient interface, should
be configured to withstand being cleaned.
5.1.5 Design Consideration: Safety
[0107] The system of the invention may be configured to communicate
with the user if an alarm has been triggered. The system of the
invention may also be configured to prevent accidental user input,
and to prevent accidental power supply disconnection.
5.1.6 Design Approach: Safety
[0108] In one sample embodiment, buttons or other forms of user
input of the user interface may be located at a position that they
cannot be activated accidentally. In addition, software control
could be implemented to ensure that a specific set of buttons must
be pushed in series to confirm a setting change. According to a
sample embodiment, the user interface may indicate when an alarm is
triggered using at least one of the following techniques:
[0109] Audible warning signal, such as a Piezo electric buzzer that
generates a clear audible tone,
[0110] LEDs to indicate an alarm has occurred; and
[0111] Backlight of graphical display illuminates.
[0112] To prevent the power supply from accidental disconnection,
the power supply connector may include a locking mechanism.
5.2 Mask and Flow Generator Incorporation
[0113] As discussed above, the patient interface 2 may include at
least one of the mask 4, the headgear 12, the flow generator 6, and
sensors (e.g., pressure, temperature, flow and/or volume). In the
sample embodiments in which the flow generator is incorporated into
the mask, the flow generator housing is configured to mount the
flow generator on the mask, secure the connection of the flow
generator to the power supply so that it cannot be accidentally
disconnected, protect the user from the flow generator inlet and
from objects that may enter the air path, and mount any sensor(s),
or other electrical devices, to the mask.
[0114] Incorporating the flow generator 6 into the mask 4, as
disclosed in some of the sample embodiments discussed above,
present several design considerations including, but not limited
to:
[0115] Weight;
[0116] Stability;
[0117] Noise and Vibration; and
[0118] Patient Comfort.
5.2.1 Design Consideration: Weight
[0119] The additional weight of a motor and an impeller of the flow
generator on the front of the mask may lead to patient discomfort
by increasing the forces that are applied to the patient's face
while wearing the mask.
5.2.2 Design Approach: Weight
[0120] One or some or all of the following techniques may be used
to minimize the weight of the patient interface:
[0121] Using a low density mask material;
[0122] Minimizing wall section thickness;
[0123] Hollowing thick sections where strength is not a
requirement; and
[0124] Minimizing the weight of the flow generator.
[0125] A first approach may be to minimize the mask and motor
housing thickness to minimize mask weight. For example, according
to one sample embodiment, the thickness of the motor housing first
part 6a may be 0.5-2.5 mm, for example 1.0-2.0 mm, or for example
0.5 mm. The thickness of the volute housing first part 6b may also
be 0.5-2.5 mm, for example 1.0-2.0 mm, or for example 1.5 mm. The
motor and volute housing second part, or cover, 6f may also have a
thickness of 0.5-2.5 mm, for example 1.0-2.0 mm, or for example 1.5
mm.
5.2.3 Design Consideration: Mask Stability
[0126] The additional weight of a motor and an impeller of the flow
generator on the front of the mask may also create instability of
the mask on the face of the patient, which may cause patient
discomfort and reduce the effectiveness of the therapy if the
instability prevents substantially leak proof contact between the
cushion and the patient's face.
5.2.4 Design Approach: Mask Stability
[0127] One approach to providing stability to a mask having an
incorporated flow generator is shown in FIGS. 9 and 9I. The flow
generator housing, including the motor housing first part 6a, the
volute housing first part 6b, and the cover 6f, are provided as
close to the mask 4 as possible. The flow generator housing may
also be inclined with respect to the mask 4 to reduce the moment of
the flow generator 6.
[0128] In determining the location of the flow generator 6 on the
mask 4, three factors may be considered. The first factor is that
as the distance between the patient's face and the center of
gravity of the motor and impeller increases, the moment between the
flow generator and the mask increases, thus creating greater mask
instability. The second factor is the location of the motor and the
impeller location should assist in reducing the number of
components of the system, such as connecting tubes or conduits, and
should not lead to decreased patient comfort, e.g,. such as
obstructing the patient's vision. The third factor is the weight of
the motor and impeller should be evenly distributed across the
surface area of the mask cushion that contacts the patient's face.
Any localized pressure points would greatly enhance the possibility
of patients developing pressure sores in these areas, and the mask
should be stabilized so as to reduce, or eliminate, such localized
pressure points.
[0129] According to sample embodiments of the invention, the
location of the flow generator on the mask was selected to be on
the front of the mask, located as to be out of the field of vision
of the patient to minimize the obtrusiveness of the system. The
flow generator was also rotated and positioned such that the centre
of gravity of the flow generator is located as close to the
patient's face as possible to minimize instability. The flow
generator was also located in a position to evenly distribute the
additional weight across the entire lower half of the patient's
face.
[0130] An analysis of the most common facial areas to suffer from
pressure sores highlights the areas of the face where bones and
other hard tissue are located close to the surface and covered by
only small thicknesses of soft facial tissue. This includes areas
such as across the bridge of the nose, on the forehead and on the
cheekbones. By locating the motor and the impeller in this
position, the additional pressure is isolated to areas of the face
that can withstand an increase in pressure. Referring to FIG. 9,
this position was determined by rotating the motor housing first
part 6a and the impeller housing second part 6b about the x and
z-axis to achieve the lowest profile possible.
5.2.5 Design Consideration: Noise and Vibration
[0131] As the flow generator operates it produces three outputs.
The first output is a pressurised airflow. The second and third
outputs are side effects of the production of the pressurised
airflow, noise and vibration. These side effects may cause patient
discomfort, and eventual patient harm if worn for extended
periods.
[0132] The motor 6d and impeller 6e create noise as they generate
the pressurised airflow. This is a consideration because of the
close proximity of the motor 6d and the impeller 6e to the
patient's face. The close proximity of the motor 6d and the
impeller 6e may cause patient discomfort and inhibit patient
recovery if it interferes with the patient's rest or sleep.
[0133] For a centrifugal fan system, as may be used in the sample
embodiments of the system of the invention, there are two primary
sources of noise: [0134] 1. Tonal or Harmonic Noise; and [0135] 2.
Blade broadband Noise.
[0136] The sound power produced by a centrifugal fan can be
estimated by using the following formula:
LW=KW+10 log10Q+20 log10 P+BPI+CN,
where: LW=sound power level (dB); KW=specific sound power level
depending on the type of fan; Q=volume flow rate (cfm); P=total
pressure (inches of H.sub.2O); BPI=blade frequency increment; and
CN=efficiency correction (because fans that are operated off their
optimum flow conditions get noisier).
5.2.5.1 Tone or Harmonic Noise
[0137] The first component of the noise emitted by the flow
generator is referred to as tone or harmonic noise and is due to
the rotation of the impeller blades past a fixed position. The
specific frequency of this noise is known as the blade pass
frequency (BPF). The BPF is equal to the number of blades N times
the Revolutions Per Minute (RPM) of the rotor, as defined by the
formula:
BPF=NRPM
[0138] The tone or harmonic noise is a problem for centrifugal fans
and influences their design. The frequency output of a single and a
three blade impeller are pictured in FIGS. 11 and 12, respectively,
where the period of one revolution is Tp.
5.2.5.2 Broadband Noise
[0139] The second component of the noise emitted by a centrifugal
fan system is broadband noise. Broadband noise is the random
non-periodic signal that is caused by the turbulent flow of air
over the blades. An example of a broadband noise that is typical of
a rotating impeller is shown in FIG. 13. As shown in the figure,
the envelop of the broadband noise varies periodically rather then
the actual signal.
5.2.5.3 Total Noise
[0140] The sum of the blade broadband and tone noise is shown in
FIG. 14.
5.2.6. Design Approach: Noise and Vibration
[0141] The majority of noise sources can be attributed to vibrating
surfaces. Therefore, vibration control is an aspect of noise
reduction.
5.2.6.1 Sound Control
[0142] To sound proof the mask and the motor housing there are two
different techniques that may be used, alone or in combination:
noise reduction and noise absorption. A third technique, including
the use of a soft joint, may also be used.
5.2.6.2 Noise Absorption
[0143] Noise absorption operates by transforming the sound wave
into another form of energy and acts to suppress the sound. As
shown in FIG. 10, to achieve this the motor housing, including the
motor housing first part 6a, the volute housing first part 6b and
the cover 6f, is designed to allow the insertion of a layer of
noise absorbing material 6m, such as open celled polyurethane (or
other suitable substance) foam, between the motor 6d and the volute
6c and the housing. Open cell foam is an effective sound barrier as
the sound is forced to travel through the different layers of the
material with different densities, thus dampening the sound.
5.2.6.3 Noise Reduction
[0144] The second technique that may be used is noise reduction.
Noise reduction includes placing a physical barrier to prevent the
transmission of sound. In this situation, the physical barrier is
the actual motor housing (i.e., the motor housing first part 6a,
the volute housing first part 6b and the cover 6f) and this
reflects the sound, for example back into the noise absorbing
material 6m. The amount of noise reduction that is possible can be
directly correlated to the mass of the physical barrier, hence
there will be a trade off between noise reduction and weight issues
as discussed previously. The depiction in FIG. 10 shows one sample
embodiment of the invention.
5.2.6.4 Soft Flexible Joint
[0145] Another approach is shown in FIG. 18. The outlet of the
volute housing first part 6b connects to the mask inlet 4d by a
soft and flexible joint 6k, for example a gusset or a grommet. The
soft and flexible joint 6k is configured to connect the air path
from the flow generator 6 to the mask 4. The soft and flexible
joint 6k also acts to isolate and dampen the vibration and prevent
the vibration form being transferred into the motor and impeller
housing and the mask.
5.2.6.5 Vibration Control
[0146] Vibration control can be achieved by using three different
techniques, isolation, damping and avoiding resonance.
5.2.6.6 Vibration Isolation
[0147] A proportion of the noise produced by a centrifugal fan
system, which may be used as a flow generator in system according
to the invention, can be attributed to vibration. Noise is produced
when vibration from one source is transferred to another system
that is a better noise radiator than the previous source. In a
centrifugal fan system this occurs when the vibration of the motor
and impeller is transferred to the flow generator housing and mask.
This transfer causes the system to act almost as a speaker.
Vibration isolation is thus useful in minimizing noise output.
[0148] It is possible to minimize the transmission of vibration
from one structure to the next structure by placing an elastic
material between the two structures. The elastic materials are
often referred to as vibration isolators and have material
properties that make them suitable for such a purpose.
[0149] According to Tandon N., Noise-reducing Designs of Machines
and Structures, Siidhanii, Vol. 25, Part 3, June 2000, pp 331-339,
vibration isolation can be understood from the analysis of an
ideal, linear, single degree of freedom system in which the
isolator is represented by the parallel combination of a massless
spring and a damper, as shown in FIG. 15.
The transmissibility of a substance is defined as the ratio of the
amplitude of the force transmitted to the supporting structure to
that of the exciting force, and can be expressed by the
formula:
T={[1+(2.zeta.r).sup.2]/[1-r.sup.2).sup.2+(2.zeta.r.sup.2).sup.2]}.sup.1-
/2,
[0150] where T is the transmissibility, .zeta. is the damping ratio
and r is the ratio of the excitation frequency to the natural
frequency of the spring mass system. When T is less then one then
the system is in isolation. Hence the system is in isolation when
r>2.sup.0.5. This means that for a substance to be an effective
isolator its stiffness must be such that the mounted resonance
frequency is less then 0.7 times the minimum forcing frequency. If
r is near 1 then this could lead to the vibration being amplified
rather then attenuated.
[0151] While this model provides an insight into vibration
isolation it is not a completely accurate description of vibration
in real world circumstances. Vibrating bodies rarely vibrate only
vertically and real springs are not massless. However, the model
shown in FIG. 15 is useful for understanding the dynamics of
vibration transfer.
[0152] Many vibration isolators are commercially available and are
generally metallic (coil springs or some other form of flexural
configuration) or elastomeric resilient elements. Elastomeric
elements are suitable for using is situations where vibrations are
caused by shear, torsion, compression modes or any combination of
these. The loss coefficient versus Young's modulus for various
elastomers and other materials is shown FIG. 16.
5.2.6.7 Vibration Dampening
[0153] Three general properties may be used to describe the noise
characteristics of a structure. These properties include mass,
stiffuess and damping. Mass and stiffuess are associated with the
storage of kinetic and shear energy, respectively, whereas damping
is associated with the dissipation of energy. Damping is the
process by which sonic vibrations are converted to heat over time
and distance. Damping results in the decay of unforced vibrations
and leads to the reduction in the amplitude of resonance frequency
for an object subjected to steady excitations. The damping
capacity, .psi., of an element is defined as the ratio of energy
dissipated per cycle to the energy present in the system. The term
used to specify material damping is the loss factor, .eta., which
may be determined according to the following formula:
.eta.=(.psi./2.pi.)=2.zeta..
Several methods may be used to dampen sound. A first method is to
use a high-density soft material, such as lead. The softness and
high density combine to dampen the noise rather then transmit
it.
[0154] Another method is to place material of different densities
in the path of the sound waves. The sound waves are forced to
travel through the different densities thus reflecting and
dampening the sound. This is why open cell foam is such an
effective sound dampener
5.2.6.8 A Voiding Resonance
[0155] Resonance is defined as the tendency for a system to
oscillate with high amplitude when excited by energy at a certain
frequency. Therefore, when designing a structure to minimize the
transmission of sound, it is desired that the resonant or natural
frequency does not correspond to the frequencies of the excitation
forces. This may be a consideration when selecting the final
production material and the effect should also be considered when
testing different prototype configurations. For an object of a
simple geometry, its resonant frequency F may be determined
according to the following formula:
F=0.5.pi.(stifness.sup.0.5/mass.sup.0.5).
[0156] In order for NIPPV therapy to be effective, the patient may
e required to use the system for several hours, during which time
the patient may be sleeping. In order to allow the patient to use
the system for such a time, user comfort should be a consideration.
One of the issues for patients wearing a respiratory mask is that
it does not inhibit their primary senses, for example sight. It is
therefore desirable that the location of the flow generator on the
front of the mask does not impinge the patient's field of
vision.
[0157] Another issue of patient comfort is the weight of the flow
generator and mask when these components are incorporated. This
consideration was previously discussed with respect to the mask and
flow generator weight and the stability of the mask and flow
generator when worn by the patient.
5.2.8 Design Approach: Patient Comfort
[0158] One sample method for preventing the pump from impinging on
the patient's field of vision is to locate the pump in such a way
that it is out of the patients field of vision. According to one
sample embodiment shown in FIG. 17, the flow generator is located
in relatively the same vertical position as the patient's nose.
5 6 Flow Generator
6.1 Pump
[0159] The flow generator 6 is configured to generate the
pressurized flow of respiratory gas. The flow generator 6 may
include a motor 6d, an impeller 6e and a volute 6c. The motor 6d,
the impeller 6e and the volute 6c may be referred to as a pump.
6.1.1 Motor
[0160] The motor 6d may be a brushless DC (BLDC) motor. A BLDC
motor has advantages over DC motors including brushes. One
advantage is that the BLDC motor does not require brushes. The BLDC
motor can operate at higher maximum speeds and is far less likely
to create sparks. This advantage assists in the safe delivery of
oxygen. As oxygen is extremely flammable, the creation of sparks is
a safety issue.
[0161] BLDC motors also require less maintenance because there is
reduced frictional contact. BLDC motors also typically operate at
cooler temperatures, increasing the lifespan of the internal
components. BLDC motors are also more efficient than DC motors with
brushes, with a typical efficiency of 85-90% compared to brushed
motors that at best deliver an efficiency of 80%. BLDC motors also
provide more precise speed control. This is a desirable advantage
for the system of the present invention because it enables the
system to deliver accurate and effective treatment.
6.1.2 Impeller and Volute
[0162] The impeller 6e is driven by the motor 6d to generate the
pressurized flow of respiratory gases. The impeller 6e may be a
rotating disk that has a set of veins that, when rotated, produce
centrifugal force within the volute 6c. The volute 6c is the
stationary housing that encompasses the impeller 6e and collects,
discharges and recirculates the air entering the pump. As shown in
FIG. 18, a soft joint 6k may be provided at the volute outlet 6n to
seal the connection between the volute outlet 6n and the mask inlet
4d. The soft joint 6k may be a silicone grommet or gusset.
6.2 Sensors
[0163] In the sample embodiments of the system of the present
invention, sensors may be incorporated into the patient interface 2
to measure at least one of the following:
[0164] Pressure;
[0165] Volume;
[0166] Flow; and
[0167] Temperature
[0168] To measure pressure, a pressure sensor(s) requires access to
space where the pressure is to be measured. In the sample
embodiments of the system of the present invention, this is in the
air path or inside the mask.
[0169] In one sample embodiment, an obtrusive flow sensor may be
used to measure flow. An obtrusive-flow sensor operates by placing
a small obstruction in the flow and measuring the pressure drop
across the obstruction. The obstruction is commonly known as an
orifice plate 28 (FIGS. 19A and 19B). According to the present
invention, an orifice plate 28 may be provided in an outlet 6n of
the volute 6c, prior to the joint 6k (FIG. 18). It should also be
appreciated that the flow sensor may be provided in the joint
6k.
[0170] FIGS. 19A and 19B demonstrate the implementation of an
obtrusive-flow sensor. When fluid flows through the system, a
pressure P1 is measured at a test port on one side of the orifice
plate 28. The fluid then flows through the orifice and a lower
pressure P2 is measured at a test port on the other side of the
orifice plate 8. The flow Q through the orifice plate 8 is directly
proportional to the square root of the drop in pressure, and may be
defined by the equation:
Q=k (P1-P2)
where: Q=flow in gallons/minute (gpm); k=is the constant that is
determined by the orifice plate; P1=is the higher pressure in front
of the orifice; and P2=is the lower pressure behind the
orifice.
[0171] Volume can then be determined by integrating flow with
respect to time.
[0172] An example of a pressure sensor that could be used in one
sample embodiment is the MPXV 5004G pressure sensor manufactured by
Freescale Semiconductors. An advantage of the MPXV5004G series is
that it is designed for a wide range of applications, including
those employing a microcontroller with analog to digital outputs.
The pressure range of this sensor also matches required pneumatic
performance for most NIPPY thereapies with a pressure range of 0 to
40 cm H.sub.2O.
[0173] The user interface 8 may be configured to receive signals
from pressure sensors at the test ports on the sides of the orifice
plate 28. The user interface 8 may be configured to calculate the
volume and flow of the pressurized gas. The user interface 8 may
also control the operation of the motor 6d to deliver the
pressurized gas flow at a desired pressure and volume. For example,
the NIPPV therapy may be a Continuous Positive Airway Pressure
(CPAP) therapy, a Variable Positive Airway Pressure (VP AP)
therapy, or a Bi-level Positive Pressure Airway Pressure (BiP AP)
therapy.
7 Patient Interface
7.1 First Patient Interface Sample Embodiment
[0174] Referring to FIGS. 20 and 21, a patient interface according
to a first sample embodiment of the invention includes a mask 4
having a mask shell 4a in which a portion of a pump housing is
integrated. The pump housing includes the motor housing first part
6a and the impeller housing first part 6b. The other portion of the
pump housing includes the cover 6f which is attached to the mask
shell 4a to enclose the pump. As shown in FIGS. 20 and 21, power to
the motor 6d may be provided by an electrical connector 14
connected between the user interface 8 and the mask 4, or from a
power supply connector 10 that may be connected to a power supply
separate from the user interface 8.
[0175] Noise absorbing material 6m may be provided in the pump
housing, both in the motor housing first part 6a and the impeller
housing first part 6b incorporated in the mask shell 4a and in the
cover 6f. The noise absorbing material 6m may be, for example, a 5
mm layer of polyethylene foam. The foam is configured to support
the pump, prevent vibration transmission 20 and dampen noise
emitted from the pump.
7.2 Second Patient Interface Sample Embodiment
[0176] Referring to FIGS. 22-25, a patient interface according to
another sample embodiment includes a pump housing 30 formed of two
parts 30a, 30b. As shown in FIG. 24, the first and second parts
30a, 30b of the pump housing 30 are connected together, for example
by fasteners 32, such as 4 mm plastic nut and bolt sets, to form
the pump housing 30.
[0177] Referring to FIGS. 22 and 23, the first and second parts
30a, 30b each include a support arm 30c. The support arms 30c
include apertures 30d configured to receive fasteners that attach
the pump housing 30 to the mask shell 4a. The pump housing 30 is
also attached to the mask shell 4a at the mask inlet 4d by a soft
joint 6k, e.g., a flexible gusset, that connects the outlet of the
pump housing 30 to the mask inlet. The soft joint 6k connecting the
pump housing outlet to the mask inlet may be configured to deliver
the required vibration isolation properties.
[0178] One part of the pump housing 30 houses a pressure sensor 40,
as shown in FIG. 25. Although the pressure sensor 40 is shown
housed in the second part 30b, it should be appreciated that the
pressure sensor 40 may be supported in the first part 30a.
[0179] The techniques of noise dampening and vibration isolation
used in the first sample embodiment of the patient interface may
also be used in the second sample embodiment of the patient
interface. In the second sample embodiment, however, the space
between the interior wall of the pump housing 30 and the motor and
impeller may be increased to allow the insertion of noise
absorption and reflection foam. This foam not only provides the
sound damping qualities used in the first sample embodiment of the
patient interface, but it also provides additional attenuation and
reflection due to the high density layer laminated onto the outer
wall.
[0180] Referring to FIG. 26, a soft joint 34 may be provided
between each support arm 30c and the mask shell. The soft joint 34
may be, for example, an elastomeric silicone rubber. As the pump
housing 30 of the second sample embodiment is not partially
integrated with the mask shell and is formed separately, the use of
the soft joints 34 provide an opportunity to isolate the vibrations
caused by the pump of the flow generator even further.
[0181] Another technique used to minimize the transmission of
vibration from the pump housing to the mask is the design of the
support arms 30c that attach the pump housing to the mask. In the
second sample embodiment, two support arms 30c are used to attach
the pump housing 30 to the mask. However, it should be appreciated
that more or less supporting arms 20c between the housing and the
mask may be provided. It should also be appreciated that the pump
housing 30 may be formed as a fully integrated structure, as shown
in FIG. 27. As the majority of vibrations for this system occur in
a horizontal plane, forming the pump housing as an integrated
structure allows the base of the pump housing the freedom to move
and not transmit this vibration directly into the mask.
[0182] The inlet 30f and the outlet 30e of the pump housing 30 may
require safety features to prevent harm to the patient. As shown in
FIG. 23, a protective screen 36, for example a fine aluminum mesh,
may be provided to cover the inlet 30f. The outlet 30e may also be
covered by a protective screen. The protective screen 36 over the
inlet 30f prevents the user from inserting a finger into the pump
housing 30 and contacting the impeller as it rotates. The
protective screen over the inlet 30f may also prevent debris from
being drawn into the pump housing 30. The protective screen over
the pump housing outlet 30e may prevent debris from being
introduced into the mask with the pressurized flow.
[0183] Another feature of the second patient interface sample
embodiment is the inclusion of a housing to hold a pressure sensor.
This is located on the flow generator housing.
[0184] As is shown in FIG. 26, the pressure sensor 40 is configured
to determine the pressure in the mask 4. A pressure port 42 is
formed in the mask 4 and a tube 44 connects the pressure sensor 40
to the pressure port 42. The pressure sensor 40 is thus configured
to determine the pressure of the flow received by the patient. This
configuration provides a more accurate pressure measurement than
current systems in which the pressure is read at up to 2 m away
from the mask at the flow generator.
[0185] One difference between the patient interface of the second
sample embodiment and the patient interface of the first sample
embodiment is that patient interface of the second sample
embodiment may be, with minor modifications, mounted on any mask,
whereas the patient interface of the first sample embodiment
requires a customized mask.
[0186] It should be appreciated that the design considerations
discussed above are not exhaustive. Other design considerations may
also be accounted for by the sample embodiments described above.
For example, the visual appearance of the mask and flow generator
system, humidification of the pressurized flow, the safety of the
oxygen delivery, sterilization of the system, fail safety
procedures and precautions, and ergonomic issues may all be
considered in the design of the system of the present
invention.
[0187] While the invention has been described in connection with
what are presently considered to be the most practical and
preferred embodiments, it is to be understood that the invention is
not to be limited to the disclosed embodiments, but on the
contrary, is intended to cover various modifications and equivalent
arrangements included within the spirit and scope of the invention.
Also, the various embodiments described above may be implemented in
conjunction with other embodiments, e.g., aspects of one embodiment
may be combined with aspects of another embodiment to realize yet
other embodiments. Further, each independent feature or component
of any given assembly may constitute an additional embodiment.
Furthermore, each individual component of any given assembly, one
or more portions of an individual component of any given assembly,
and various combinations of components from one or more embodiments
may include one or more ornamental design features. In addition,
while the invention has particular application to patients who
suffer from OSA, it is to be appreciated that patients who suffer
from other illnesses (e.g., congestive heart failure,
diabetes.about.morbid obesity, stroke, barriatric surgery, etc.)
can derive benefit from the above teachings. Moreover, the above
teachings have applicability with patients and non-patients alike
in non-medical applications.
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