U.S. patent application number 16/887417 was filed with the patent office on 2020-09-17 for adaptive patient circuit compensation with pressure sensor at mask apparatus.
The applicant listed for this patent is KONINKLIJKE PHILIPS N.V.. Invention is credited to Christopher Scott Lucci, Nathan Francis O'Connor.
Application Number | 20200289772 16/887417 |
Document ID | / |
Family ID | 1000004857394 |
Filed Date | 2020-09-17 |
United States Patent
Application |
20200289772 |
Kind Code |
A1 |
O'Connor; Nathan Francis ;
et al. |
September 17, 2020 |
ADAPTIVE PATIENT CIRCUIT COMPENSATION WITH PRESSURE SENSOR AT MASK
APPARATUS
Abstract
In certain embodiments, a system for providing respiratory
therapy is provided. The system comprises a pressure generator for
generating a pressurized flow of breathable gas; a subject
interface for guiding the pressurized flow of breathable gas to a
point of delivery at or near the airway of the subject, wherein the
subject interface causes a pressure drop between an output of the
pressure generator and the point of delivery; one or more sensors
for generating output signals conveying information related to gas
parameters of the pressurized flow of breathable gas; one or more
processors configured to adjust one or more model parameters of a
parameter-based model that models the subject interface; estimate
the pressure drop between the output of the pressure generator and
the point of delivery based on the adjusted model parameters; and
adjust levels of the gas parameters based on the estimated pressure
drop.
Inventors: |
O'Connor; Nathan Francis;
(Monroeville, PA) ; Lucci; Christopher Scott;
(Murrysville, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KONINKLIJKE PHILIPS N.V. |
Eindhoven |
|
NL |
|
|
Family ID: |
1000004857394 |
Appl. No.: |
16/887417 |
Filed: |
May 29, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14434626 |
Apr 9, 2015 |
10668236 |
|
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PCT/IB2013/059276 |
Oct 10, 2013 |
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16887417 |
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61711791 |
Oct 10, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 16/0069 20140204;
A61M 16/026 20170801; A61M 2205/3303 20130101; A61M 16/0051
20130101; A61M 2205/505 20130101; A61M 16/161 20140204; A61M
16/0875 20130101; A61M 2205/3592 20130101; A61M 16/0003 20140204;
A61M 2205/3584 20130101; A61M 2016/0039 20130101; A61M 2205/50
20130101; A61M 2205/52 20130101; A61M 2205/3344 20130101; A61M
16/06 20130101; A61M 2016/0027 20130101; A61M 2205/3365 20130101;
A61M 2016/102 20130101 |
International
Class: |
A61M 16/00 20060101
A61M016/00; A61M 16/06 20060101 A61M016/06; A61M 16/08 20060101
A61M016/08 |
Claims
1. A system for providing respiratory therapy during a therapy
session to a subject, the system comprising: a pressure generator
configured to generate a pressurized flow of breathable gas for
delivery to the airway of the subject, the pressure generator
having an output configured to expel the pressurized flow of
breathable gas; a subject interface configured to guide the
pressurized flow of breathable gas from the output of the pressure
generator to a point of delivery at or near the airway of the
subject, wherein the subject interface causes a pressure drop
between the output of the pressure generator and the point of
delivery during delivery of the pressurized flow of breathable gas;
one or more sensors configured to generate output signals conveying
information related to one or more gas parameters of the
pressurized flow of breathable gas; one or more processors
configured to execute processing modules, the processing modules
comprising: a model module configured to adjust one or more model
parameters of a parameter-based model that models the subject
interface, the one or more model parameters being different than
the one or more gas parameters, and wherein the parameter-based
model includes one or more model parameters related to pneumatic
impedance of the subject interface; an estimation module configured
to estimate the pressure drop between the output of the pressure
generator and the point of delivery during delivery of the
pressurized flow of breathable gas based on the generated output
signal and based on the one or more adjusted model parameters of
the parameter-based models; and a control module configured to
adjust levels of one or more gas parameters of the pressurized flow
of breathable gas based on the estimated pressure drop.
2. The system of claim 1, further comprising: wherein adjustments
by the control module are further based on the parameter-based
model.
3. The system of claim 1, further comprising: a target module
configured to determine a target pressure for the pressurized flow
of breathable gas that compensates for or one or more effects of a
transport delay of a pressure wave propagating through the subject
interface during the therapy session, and wherein the control
module is further configured to adjust levels of one or more gas
parameters of the pressurized flow of breathable gas based on the
target pressure.
4. The system of claim 3, further comprising: a device pressure
module configured to determine a device pressure at or near the
output of the pressure generator; an error module configured to
determine a pressure error based on a difference between the target
pressure and the determined device pressure; and wherein the
adjustments by the model module are further based on the device
pressure, and wherein adjustments by the control module are further
based on the pressure error.
5. The system of claim 4, wherein one of the one or more sensors is
disposed at or near the output of the pressure generator, and
wherein determination of the device pressure is based on output
signals generated by the sensor disposed at or near the output of
the pressure generator.
6. The system of claim 1, wherein operations of one or more sensors
and the one or more processors are performed in an ongoing manner
during the therapy session.
7. A method for providing respiratory therapy during a therapy
session to a subject implemented in a system including a pressure
generator, a subject interface, and one or more sensors, the method
comprising: generating a pressurized flow of breathable gas for
delivery to the airway of the subject via an output of the pressure
generator; guiding the pressurized flow of breathable gas from the
output of the pressure generator to a point of delivery at or near
the airway of the subject via the subject interface, wherein the
subject interface causes a pressure drop between the output of the
pressure generator and the point of delivery during delivery of the
pressurized flow of breathable gas; generating output signals
conveying information related to one or more gas parameters of the
pressurized flow of breathable gas; adjusting one or more model
parameters of a parameter-based model that models the subject
interface, the one or more model parameters being different than
the one or more gas parameters, and wherein the parameter-based
model includes one or more model parameters related to pneumatic
impedance of the subject interface; estimating the pressure drop
between the output of the pressure generator and the point of
delivery during delivery of the pressurized flow of breathable gas
based on the generated output signal and based on the one or more
adjusted model parameters of the parameter-based models; and
adjusting levels of one or more gas parameters of the pressurized
flow of breathable gas based on the estimated pressure drop.
8. The method of claim 7, wherein adjusting levels of one or more
gas parameters of the pressurized flow of breathable gas is further
based on the parameter-based model.
9. The method of claim 7, further comprising: determining a target
pressure for the pressurized flow of breathable gas that
compensates for or one or more effects of a transport delay of a
pressure wave propagating through the subject interface during the
therapy session, and wherein adjusting levels of one or more gas
parameters of the pressurized flow of breathable gas is further
based on the target pressure.
10. The method of claim 9, further comprising: determining a device
pressure at or near the output of the pressure generator;
determining a pressure error based on a difference between the
target pressure and the determined device pressure; and wherein
adjusting one or more model parameters of the parameter-based model
is further based on the device pressure, and wherein adjusting
levels of one or more gas parameters of the pressurized flow of
breathable gas is further based on the pressure error.
11. The method of claim 10, determining the device pressure is
based on output signals generated by a sensor disposed at or near
the output of the pressure generator.
12. The method of claim 7, wherein operations of the method are
performed in an ongoing manner during the therapy session.
13. A system configured providing respiratory therapy during a
therapy session to a subject, the system comprising: pressure means
for generating a pressurized flow of breathable gas for delivery to
the airway of the subject; guiding means for guiding the
pressurized flow of breathable gas from an output of the pressure
means to a point of delivery at or near the airway of the subject,
wherein the guiding means causes a pressure drop between the output
of the pressure means and the point of delivery during delivery of
the pressurized flow of breathable gas; means for generating output
signals conveying information related to one or more gas parameters
of the pressurized flow of breathable gas, wherein the output
signals are generated in an ongoing manner during the therapy
session; means for adjusting one or more model parameters of a
parameter-based model that models the subject interface, the one or
more model parameters being different than the one or more gas
parameters, and wherein the parameter-based model includes one or
more model parameters related to pneumatic impedance of the subject
interface; means for estimating the pressure drop between the
output of the pressure generator and the point of delivery during
delivery of the pressurized flow of breathable gas based on the
generated output signal and based on the one or more adjusted model
parameters of the parameter-based models; and means for adjusting
levels of one or more gas parameters of the pressurized flow of
breathable gas based on the estimated pressure drop.
14. The system of claim 13, wherein adjusting levels of one or more
gas parameters of the pressurized flow of breathable gas is further
based on the parameter-based model.
15. The system of claim 13, further comprising: means for
determining a target pressure for the pressurized flow of
breathable gas that compensates for or one or more effects of a
transport delay of a pressure wave propagating through the guiding
means during the therapy session, and wherein adjusting levels of
one or more gas parameters of the pressurized flow of breathable
gas is further based on the target pressure.
16. The method of claim 15, further comprising: means for
determining a device pressure at or near the output of the pressure
means; means for determining a pressure error based on a difference
between the target pressure and the determined device pressure; and
wherein adjusting one or more model parameters of the
parameter-based model is further based on the device pressure, and
wherein adjusting levels of one or more gas parameters of the
pressurized flow of breathable gas is further based on the pressure
error.
17. The system of claim 16, wherein determining the device pressure
is based on output signals generated by a means for generating
output signals disposed at or near the output of the pressure
means.
18. The system of claim 13, wherein operations of the system are
performed in an ongoing manner during the therapy session.
Description
RELATED APPLICATION(S)
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/434,626, filed Apr. 9, 2015, which is the
U.S. National Phase application under 35 U.S.C. .sctn. 371 of
International Application No. PCT/1B2013/059276, filed on Oct. 10,
2013, which claims the benefit of U.S. Provisional Patent
Application No. 61/711,791, filed on Oct. 10, 2012. These
applications are hereby incorporated by reference herein in their
entirety.
FIELD OF THE INVENTION
[0002] The present disclosure pertains to a system and method for
providing respiratory therapy through a pressure support device,
and, in particular, to modeling, estimating, and compensating for
one or more effects of transport delay through tubing within the
pressure support device, including but not limited to a pressure
drop between the output of a pressure generator and the point of
delivery of a pressurized flow of breathable gas.
BACKGROUND
[0003] It is well known that some types of respiratory therapy
involve the delivery of a flow of breathable gas to the airway of a
subject. It is known that a flow of breathable gas may be
pressurized at varying levels of pressure, even during a single
therapy session. It is known that one or more algorithms may
operate to control and/or adjust the pressure level or flow used in
respiratory therapy. It is known that measurements or estimations
of various gas parameters can be used in a feedback or feedforward
manner to control and/or adjust the pressure level used in
respiratory therapy. It is known that there are practical
limitations to the responsiveness and/or stability of a respiratory
therapy device, due, in part, to the transport delay of a pressure
wave propagating through the respiratory therapy device on its way
to the point of delivery, such as the tubing and mask of a
patient.
SUMMARY
[0004] Accordingly, it is an object of one or more embodiments of
the present invention to provide a system for providing respiratory
therapy during a therapy session to a subject. The system comprises
a pressure generator configured to generate a pressurized flow of
breathable gas for delivery to the airway of the subject, the
pressure generator having an output configured to expel the
pressurized flow of breathable gas; a subject interface configured
to guide the pressurized flow of breathable gas from the output of
the pressure generator to a point of delivery at or near the airway
of the subject, wherein the subject interface causes a pressure
drop between the output of the pressure generator and the point of
delivery during delivery of the pressurized flow of breathable gas;
one or more sensors configured to generate output signals conveying
information related to one or more gas parameters of the
pressurized flow of breathable gas; one or more processors
configured to execute processing modules, the processing modules
comprising: a model module configured to adjust one or more model
parameters of a parameter-based model that models the subject
interface, the one or more model parameters being different than
the one or more gas parameters, and wherein the parameter-based
model includes one or more model parameters related to pneumatic
impedance of the subject interface; an estimation module configured
to estimate the pressure drop between the output of the pressure
generator and the point of delivery during delivery of the
pressurized flow of breathable gas based on the generated output
signal and based on the one or more adjusted model parameters of
the parameter-based models; and a control module configured to
adjust levels of one or more gas parameters of the pressurized flow
of breathable gas based on the estimated pressure drop.
[0005] It is yet another aspect of one or more embodiments of the
present invention to provide a method for providing respiratory
therapy during a therapy session to a subject implemented in a
system including a pressure generator, a subject interface, and one
or more sensors, the method comprising: generating a pressurized
flow of breathable gas for delivery to the airway of the subject
via an output of the pressure generator; guiding the pressurized
flow of breathable gas from the output of the pressure generator to
a point of delivery at or near the airway of the subject via the
subject interface, wherein the subject interface causes a pressure
drop between the output of the pressure generator and the point of
delivery during delivery of the pressurized flow of breathable gas;
generating output signals conveying information related to one or
more gas parameters of the pressurized flow of breathable gas;
adjusting one or more model parameters of a parameter-based model
that models the subject interface, the one or more model parameters
being different than the one or more gas parameters, and wherein
the parameter-based model includes one or more model parameters
related to pneumatic impedance of the subject interface; estimating
the pressure drop between the output of the pressure generator and
the point of delivery during delivery of the pressurized flow of
breathable gas based on the generated output signal and based on
the one or more adjusted model parameters of the parameter-based
models; and adjusting levels of one or more gas parameters of the
pressurized flow of breathable gas based on the estimated pressure
drop.
[0006] It is yet another aspect of one or more embodiments to
provide a system configured to providing respiratory therapy during
a therapy session to a subject. The system comprises pressure means
for generating a pressurized flow of breathable gas for delivery to
the airway of the subject; guiding means for guiding the
pressurized flow of breathable gas from an output of the pressure
means to a point of delivery at or near the airway of the subject,
wherein the guiding means causes a pressure drop between the output
of the pressure means and the point of delivery during delivery of
the pressurized flow of breathable gas; means for generating output
signals conveying information related to one or more gas parameters
of the pressurized flow of breathable gas, wherein the output
signals are generated in an ongoing manner during the therapy
session; means for adjusting one or more model parameters of a
parameter-based model that models the subject interface, the one or
more model parameters being different than the one or more gas
parameters, and wherein the parameter-based model includes one or
more model parameters related to pneumatic impedance of the subject
interface; means for estimating the pressure drop between the
output of the pressure generator and the point of delivery during
delivery of the pressurized flow of breathable gas based on the
generated output signal and based on the one or more adjusted model
parameters of the parameter-based models; and means for adjusting
levels of one or more gas parameters of the pressurized flow of
breathable gas based on the estimated pressure drop.
[0007] These and other objects, features, and characteristics of
the present invention, as well as the methods of operation and
functions of the related elements of structure and the combination
of parts and economies of manufacture, will become more apparent
upon consideration of the following description and the appended
claims with reference to the accompanying drawings, all of which
form a part of this specification, wherein like reference numerals
designate corresponding parts in the various figures. It is to be
expressly understood, however, that the drawings are for the
purpose of illustration and description only and are not intended
as a definition of the limits of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 schematically illustrates a system for providing
respiratory therapy to a subject in accordance with one or more
embodiments;
[0009] FIG. 2 schematically illustrates an exemplary system for
providing respiratory therapy to a subject;
[0010] FIG. 3 illustrates a method for providing respiratory
therapy to a subject; and
[0011] FIG. 4 schematically illustrates an electrical circuit
representation of a system for providing respiratory therapy to a
subject in accordance with one or more embodiments.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0012] As used herein, the singular form of "a", "an", and "the"
include plural references unless the context clearly dictates
otherwise. As used herein, the statement that two or more parts or
components are "coupled" shall mean that the parts are joined or
operate together either directly or indirectly, i.e., through one
or more intermediate parts or components, so long as a link occurs.
As used herein, "directly coupled" means that two elements are
directly in contact with each other. As used herein, "fixedly
coupled" or "fixed" means that two components are coupled so as to
move as one while maintaining a constant orientation relative to
each other. As used herein, the word "unitary" means a component is
created as a single piece or unit. That is, a component that
includes pieces that are created separately and then coupled
together as a unit is not a "unitary" component or body. As
employed herein, the statement that two or more parts or components
"engage" one another shall mean that the parts exert a force
against one another either directly or through one or more
intermediate parts or components. As employed herein, the term
"number" shall mean one or an integer greater than one (i.e., a
plurality). Directional phrases used herein, such as, for example
and without limitation, top, bottom, left, right, upper, lower,
front, back, and derivatives thereof, relate to the orientation of
the elements shown in the drawings and are not limiting upon the
claims unless expressly recited therein.
[0013] FIG. 1 schematically illustrates a system 100 for providing
respiratory therapy to a subject 106. System 100 may be implemented
as, integrated with, and/or operating in conjunction with a
respiratory therapy device. System 100 dynamically models,
measures, determines, and/or estimates one or more effects of
transport delay through tubing and/or other pneumatic system
parameters within a respiratory therapy device, including but not
limited to a pressure drop dynamically during a therapy session and
compensates for one or more effects in order to improve the
quality, responsiveness, and/or stability of the respiratory
therapy device and/or the provided respiratory therapy.
[0014] Quality of a respiratory therapy device and/or the provided
respiratory therapy may pertain to the precision of the level
and/or timing of one or more gas parameters of a delivered
pressurized flow of breathable gas, in particular in response to
load-side disturbances such as flow changes from the subject and/or
components of system 100. Alternatively, and/or simultaneously,
quality may pertain to the bandwidth of the respiratory therapy
device. Alternatively, and/or simultaneously, quality may pertain
to the amount of noise or the signal-to-noise ratio within a
respiratory therapy device. Responsiveness of a respiratory therapy
device may pertain to how well and/or how rapidly the device
handles load disturbances (and/or other flow changes) and/or
set-point changes within the system. Such changes may include,
without limitation, breathing, sneezing, coughing and/or other
actions by subject 106, as well as changes due to hardware
components, such as a tube moving, bending, etc. In some cases,
responsiveness may be characterized by a response rate. Stability
of a respiratory therapy device may pertain to the likelihood of
introducing oscillations within the device during a therapy
session. Alternatively, and/or simultaneously, stability may be
characterized by a gain margin and a phase margin.
[0015] A therapy "session" of using system 100 may be defined as a
period of substantially uninterrupted therapeutic usage of system
100, not to exceed some upper threshold of (consecutive) hours. The
upper threshold may be, for example, about 6 hours, about 8 hours,
about 10 hours, about 12 hours, about 16 hours, about 24 hours
and/or other time periods. If the respiratory therapy is used to
treat sleeping disorders the related session length may correspond
to the sleeping pattern of a subject. A typical session length may
thus be about eight hours. Alternatively, and/or simultaneously, a
therapy session may be defined as a period of substantially
uninterrupted therapeutic usage of system 100, not to span less
than some lower threshold of (consecutive) units of time, and/or at
least a minimum period of time apart from a previous session. The
lower threshold may be, for example, about 15 minutes, about 30
minutes, about 1 hour, about 2 hours, about 3 hours, about 4 hours,
about 5 hours and/or other time periods. For example, a minute of
usage may be too short to be regarded as a session. For example,
two 3-hour periods of usage separated by a 10-minute gap may be
regarded as one session rather than two sessions. Individual
therapy sessions may have a beginning and an end.
[0016] In some embodiments, one or more operative levels (e.g.
pressure, volume, etc.) are adjusted on a relatively ongoing manner
(e.g., between individual breaths, every few breaths, every few
seconds, every minute, etc.) during an individual therapy session
to titrate the therapy and/or to compensate for other changes in
the patient circuit.
[0017] System 100 includes one or more of a pressure generator 140,
a delivery circuit 180, one or more sensors 142, an electronic
storage 130, a user interface 120, a processor 110, an estimation
module 111, a target module 112, a control module 113, a patient
pressure module 114, a device pressure module 115, an error module
116, a parameter determination module 117, and/or other
components.
[0018] Pressure generator 140 of system 100 in FIG. 1 may be
integrated, combined, coupled, and/or connected with a (positive)
airway pressure device (PAP/CPAP/BiPAP.RTM.etc.). Pressure
generator 140 may be configured to provide a pressurized flow of
breathable gas for delivery to the airway of subject 106, e.g. via
an output 141 of pressure generator 140, and/or via a delivery
circuit 180. Delivery circuit 180 may sometimes be referred to as
subject interface 180. Subject 106 may initiate one or more phases
of respiration. Respiratory therapy may be implemented as pressure
control, pressure support, volume control, and/or other types of
support and/or control. For example, to support inspiration, the
pressure of the pressurized flow of breathable gas may be adjusted
to an inspiratory pressure. Alternatively, and/or simultaneously,
to support expiration, the pressure and/or flow of the pressurized
flow of breathable gas may be adjusted to an expiratory pressure.
Adjustments may be made numerous times in implementations using
auto-titrating for providing respiratory support through the
delivery of the pressurized flow of breathable gas. In addition to
alternating between multiple levels, the inhalation pressure level
may ramp up or down according to a predetermined slope (absolute
and/or relative, e.g. dependent on breathing rate) for any
specified section of a phase. Similar features may be available for
exhalation phases. The pressure levels may be either predetermined
and fixed, follow a predetermined dynamic characteristic, or they
may dynamically change breath-to-breath or night-to-night depending
on sensed breathing, breathing disorder, or other physiological
characteristics. Pressure generator 140 is configured to adjust one
or more of pressure levels, flow, humidity, velocity, acceleration,
and/or other parameters of the pressurized flow of breathable gas,
e.g. in substantial synchronization with the breathing cycle of the
subject.
[0019] An airway pressure device may be configured such that one or
more gas parameters of the pressurized flow of breathable gas are
controlled in accordance with a therapeutic respiratory regimen for
subject 106. The one or more gas parameters include one or more of
flow, volume, retrograde volume, pressure, humidity, velocity,
acceleration, (intentional) gas leak, and/or other parameters.
System 100 may be configured to provide types of therapy including
types of therapy where a subject performs inspiration and/or
expiration of his own accord or where the device provides negative
airway pressure.
[0020] The functional relation between the pressure level at output
141 of pressure generator 140 and the pressure level at the point
of delivery to subject 106 may be referred to as a transfer
function. A parameter-based model that models one or more of
subject interface 180, interaction between subject interface 180
and subject 106, and/or other components within system 100 may be
used to analyze the transfer function in the context of a
closed-loop feedback/feedforward system. The parameter-based model
may contain a patient model as well as a patient interface circuit
pneumatic model. The parameter-based model may be dynamic, e.g. the
parameters may change in value dynamically, or model elements may
be added, removed, and/or reconfigured dynamically to better
estimate the patient model or patient interface circuit pneumatic
model. Usage and/or analysis of the parameter-based model, e.g.
pertaining to the transfer function, may pertain to the effects of
a time delay, such as the transport delay of a pressure wave
propagating through subject interface 180, on, e.g., system
responsiveness and stability. An example of a transfer function for
an input X.sub.set versus an output X.sub.Actual is given by the
equation below:
X Actual X Set = KG ( s ) 1 + KG ( s ) = K s 3 + 2 s 2 + s + K ,
for a gain K ##EQU00001##
[0021] Note that a time delay in may contribute a linearly
increasing phase lag in which the degree of negative phase
contribution is proportional to frequency. Adding a small time
delay may affect only the phase, thereby decreasing the stability
margins. If the time delay is large enough, a reduction in gain may
be needed to maintain stability and/or limit other undesirable
effects, effectively limiting the response speed.
[0022] A pressurized flow of breathable gas is delivered from
pressure generator 140 to the airway of subject 106 via delivery
circuit 180. Delivery circuit 180 may include a conduit 182 and/or
a subject interface appliance 184. Conduit 182 may include a
flexible length of hose, or other conduit, either in single-limb or
dual-limb configuration that places subject interface appliance 184
in fluid communication with pressure generator 140. Conduit 182
forms a flow path through which the pressurized flow of breathable
gas is communicated between subject interface appliance 184 and
pressure generator 140. Conduit 182 may comprise a standard 22 mm
diameter hose (other common diameters range between 3/4'' and 1'')
or, in certain embodiments, a much smaller diameter hose that is in
the range of 1/3 of a standard size hose. Such a hose, which may be
referred to as a restricted flow hose or limited flow hose, (for
example, having a diameter ranging between 1/4'' and 1/3'', or
alternatively between 6 mm and 9 mm) may have a greater resistance
to gas flow and/or may be smaller and/or less obtrusive.
[0023] Subject interface appliance 184 of system 100 in FIG. 1 is
configured to deliver the pressurized flow of breathable gas to the
airway of subject 106. As such, subject interface appliance 184 may
include any appliance suitable for this function. In some
embodiments, pressure generator 140 is a dedicated ventilation
device and subject interface appliance 184 is configured to be
removably coupled with another interface appliance being used to
deliver respiratory therapy to subject 106. For example, subject
interface appliance 184 may be configured to engage with and/or be
inserted into an endotracheal tube, a tracheotomy portal, and/or
other interface appliances. In one embodiment, subject interface
appliance 184 is configured to engage the airway of subject 106
without an intervening appliance. In this embodiment, subject
interface appliance 184 may include one or more of an endotracheal
tube, a nasal cannula, a tracheotomy tube, a nasal mask, a
nasal/oral mask, a full-face mask, a total facemask, and/or other
interface appliances that communicate a flow of gas with an airway
of a subject. The present disclosure is not limited to these
examples, and contemplates delivery of the pressurized flow of
breathable gas to subject 106 using any subject interface.
[0024] Electronic storage 130 of system 100 in FIG. 1 comprises
electronic storage media that electronically stores information.
The electronic storage media of electronic storage 130 may include
one or both of system storage that is provided integrally (i.e.,
substantially non-removable) with system 100 and/or removable
storage that is removably connectable to system 100 via, for
example, a port (e.g., a USB port, a FireWire port, etc.) or a
drive (e.g., a disk drive, etc.). Electronic storage 130 may
include one or more of optically readable storage media (e.g.,
optical disks, etc.), magnetically readable storage media (e.g.,
magnetic tape, magnetic hard drive, floppy drive, etc.), electrical
charge-based storage media (e.g., EPROM, EEPROM, RAM, FRAM, etc.),
solid-state storage media (e.g., flash drive, etc.), and/or other
electronically readable storage media. Electronic storage 130 may
store software algorithms, information determined by processor 110,
information received via user interface 120, and/or other
information that enables system 100 to function properly. For
example, electronic storage 130 may record or store timing
information (including duration of inhalation phases and exhalation
phases as well as transitional moments), one or more (breathing)
parameters and/or other parameters (as discussed elsewhere herein),
pressure levels, pressure drop estimated at various moments,
information indicating whether the subject adequately complied with
a prescribed respiratory therapy regimen, information indicating
whether a respiratory event (including Cheyne-Stokes respiration,
central sleep apnea, obstructive sleep apnea, hypopnea, snoring,
hyperventilation, and/or other respiratory events) occurred,
information indicating adequacy of treatment, and/or other
information. Electronic storage 130 may be a separate component
within system 100, or electronic storage 130 may be provided
integrally with one or more other components of system 100 (e.g.,
processor 110).
[0025] User interface 120 of system 100 in FIG. 1 is configured to
provide an interface between system 100 and a user (e.g., user 108,
subject 106, a caregiver, a therapy decision-maker, etc.) through
which the user can provide information to and receive information
from system 100. This enables data, results, and/or instructions
and any other communicable items, collectively referred to as
"information," to be communicated between the user and system 100.
An example of information that may be conveyed to user 108 is a
report detailing occurrences of respiratory events throughout a
period during which the subject is receiving therapy. Examples of
interface devices suitable for inclusion in user interface 120
include a keypad, buttons, switches, a keyboard, knobs, levers, a
display screen, a touch screen, speakers, a microphone, an
indicator light, an audible alarm, and a printer. Information may
be provided to user 108 or subject 106 by user interface 120 in the
form of auditory signals, visual signals, tactile signals, and/or
other sensory signals.
[0026] It is to be understood that other communication techniques,
either hard-wired or wireless, are also contemplated herein as user
interface 120. For example, in one embodiment, user interface 120
may be integrated with a removable storage interface provided by
electronic storage 130. In this example, information is loaded into
system 100 from removable storage (e.g., a smart card, a flash
drive, a removable disk, etc.) that enables the user(s) to
customize system 100. Other exemplary input devices and techniques
adapted for use with system 100 as user interface 120 include, but
are not limited to, an RS-232 port, RF link, an IR link, modem
(telephone, cable, Ethernet, internet or other). In short, any
technique for communicating information with system 100 is
contemplated as user interface 120.
[0027] One or more sensors 142 of system 100 in FIG. 1 are
configured to generate output signals conveying measurements
related to gas parameters of respiratory airflow, parameters
related to airway mechanics, and/or other parameters. Gas
parameters may include flow, (airway) pressure, humidity, velocity,
acceleration, and/or other gas parameters. Output signals may
convey measurements related to respiratory parameters. Sensor 142
may be in fluid communication with conduit 182 and/or subject
interface appliance 184. Sensor 142 may generate output signals
related to physiological parameters pertaining to subject 106.
Parameters may be associated with the state and/or condition of an
airway of subject 106, the breathing of subject 106, the gas
breathed by subject 106, the composition of the gas breathed by
subject 106, the delivery of the gas to the airway of subject 106,
and/or a respiratory effort by the subject. For example, a
parameter may be related to a mechanical unit of measurement of a
component of pressure generator 140 (or of a device that pressure
generator 140 is integrated, combined, or connected with) such as
valve drive current, rotor speed, motor speed, blower speed, fan
speed, or a related measurement and/or unit that may serve as a
proxy for any of the parameters listed herein through a previously
known and/or calibrated mathematical relationship. Sensed signals
may include any information obtained by or extracted from
fundamental relationships involving control parameters or
surrogates.
[0028] The illustration of sensor 142 including two members in FIG.
1 is not intended to be limiting. In some hardware configurations,
system 100 may use only one sensor 142. The individual sensor 142
may be located at or near subject interface appliance 184, or at
other locations. In some hardware configurations, system may
include a sensor 142 at or near output 141 of pressure generator
140. The illustration of a sensor 142 at or near subject interface
appliance 184 and a sensor 142 at or near output 141 of pressure
generator 140 is not intended to be limiting. Resulting signals or
information from one or more sensors 142 may be transmitted to
processor 110, user interface 120, electronic storage 130, and/or
other components of system 100. This transmission may be wired
and/or wireless.
[0029] The one or more sensors 142 may be configured to generate
output signals in an ongoing manner during a therapy session. This
may include generating signals intermittently, periodically (e.g.
at a sampling rate), continuously, continually, at varying
intervals, and/or in other ways that are ongoing during at least a
portion of the therapy session. For example, in some embodiments,
the generated output signals may be considered as a vector of
output signals, such that a vector includes multiple samples of
information conveyed related to one or more gas parameters and/or
other parameters. Different parameters may be related to different
vectors. A particular parameter determined in an ongoing manner
from a vector of output signals may be considered as a vector of
that particular parameter.
[0030] Processor 110 of system 100 in FIG. 1 is configured to
provide information processing capabilities in system 100. As such,
processor 110 includes one or more of a digital processor, an
analog processor, a digital circuit designed to process
information, an analog circuit designed to process information, a
state machine, and/or other mechanisms for electronically
processing information. Although processor 110 is shown in FIG. 1
as a single entity, this is for illustrative purposes only. In some
embodiments, processor 110 includes a plurality of processing
units.
[0031] As is shown in FIG. 1, processor 110 is configured to
execute one or more computer program modules. The one or more
computer program modules include one or more of estimation module
111, target module 112, control module 113, patient pressure module
114, device pressure module 115, error module 116, parameter
determination module 117, model module 118, and/or other modules.
Processor 110 may be configured to execute modules 111-118 by
software; hardware; firmware; some combination of software,
hardware, and/or firmware; and/or other mechanisms for configuring
processing capabilities on processor 110.
[0032] It should be appreciated that although modules 111-118 are
illustrated in FIG. 1 as being co-located within a single
processing unit, in embodiments in which processor 110 includes
multiple processing units, one or more of modules 111-118 may be
located remotely from the other modules. The description of the
functionality provided by the different modules 111-118 described
herein is for illustrative purposes, and is not intended to be
limiting, as any of modules 111-118 may provide more or less
functionality than is described. For example, one or more of
modules 111-118 may be eliminated, and some or all of its
functionality may be incorporated, shared, integrated into, and/or
otherwise provided by other ones of modules 111-118. Note that
processor 110 may be configured to execute one or more additional
modules that may perform some or all of the functionality
attributed below to one of modules 111-118.
[0033] Parameter determination module 117 of system 100 in FIG. 1
is configured to determine one or more gas parameters, breathing
parameters, and/or other parameters based on one or more of output
signals generated by sensor(s) 142 and/or other information
sources. Determinations may be based on measurements, calculations,
estimations, approximations, previously known and/or calibrated
mathematical relationships, and/or other ways to determine a
parameter. The other information sources may include motor
currents, motor voltage, motor parameters, valve parameters, and/or
other sources. The determined parameters may include system
parameters and/or controlled parameters, i.e. not just sensed
signals.
[0034] Operation of parameter determination module 117 may be
performed in an ongoing manner.
[0035] The one or more gas parameter may include and/or be related
to one or more of (peak) flow rate, flow rate, (tidal) volume,
pressure, temperature, humidity, velocity, acceleration, gas
composition (e.g. concentration(s) of one or more constituents such
as, e.g., CO.sub.2), thermal energy dissipated, (intentional) gas
leak, and/or other measurements related to the (pressurized) flow
of breathable gas. One or more gas parameters may be determined at
different locations and/or positions within system 100, including
within pressure generator 140, at or near output 141 of pressure
generator 140, within subject interface 180, at or near the point
of engagement between pressure generator 140 and subject interface
180, within conduit 182, at or near an input of conduit 182, at or
near an output of conduit 182, within subject interface appliance
184, at or near an input of subject interface appliance 184, at or
near an output of subject interface appliance 184, and/or at other
locations and/or positions within system 100.
[0036] Parameter determination module 117 may derive one or more
breathing parameters from one or more determined gas parameters
and/or generated output signals. The one or more breathing
parameters may include one or more of respiratory rate, breathing
period, inhalation time or period, exhalation time or period,
respiration flow curve shape, transition time from inhalation to
exhalation and/or vice versa, transition time from peak inhalation
flow rate to peak exhalation flow rate and/or vice versa,
respiration pressure curve shape, maximum proximal pressure drop
(per breathing cycle and/or phase), and/or other breathing
parameters.
[0037] Parameter determination module 117 may derive vectors of
parameters in an ongoing manner during a therapy session from
vectors of generated output signals and/or other (vectors of)
determined parameters.
[0038] Model module 118 is configured to dynamically manage a
parameter-based system model that models one or more of subject
interface 180, interaction between subject interface 180 and
subject 106, subject 106, and/or other components within system
100. The parameter-based model may be derived using electrical
circuit representation of system 100. The parameter-based model
includes one or more model parameters related to one or more of
pneumatic impedance, resistance, inertance/inductance, capacitance,
and/or other characteristics. The parameter-based model may
separately represent resistive, compliance, inertance, and/or other
(pneumatic) components of the patient pneumatic model. Model module
118 may be configured to adjust one or more model parameters
described herein in an ongoing manner during a therapy session. As
used herein, "adjusting" a model parameter may include correcting a
model parameter. Adjustments by model module 118 may be based on
one or more of information from parameter determination module 117
and/or the output signals generated by one or more sensors 142.
[0039] By way of illustration, FIG. 4 schematically illustrates
model 100b, an electrical circuit representation of system 100 as
shown in FIG. 1. Note that in FIG. 4 "hose" may refer to conduit
182 as shown in FIG. 1, or subject interface 180 as shown in FIG.
1, without subject interface appliance 184 as shown in FIG. 1. Note
that in FIG. 4 "mask" refers to subject interface appliance 184 as
shown in FIG. 1. As depicted in FIG. 4, P.sub.device is the
pressure level at the output of the pressure generator, R.sub.hose
is the "hose" resistance, L.sub.hose, is the "hose" inertance,
R.sub.mask is the resistance of the subject interface appliance,
P.sub.patient is the patient pressure or subject pressure,
R.sub.leak is the leak resistance, R.sub.patient is the resistance
of the patient airways and lungs, L.sub.patient is the inertance of
the patient airways, C.sub.patient is the compliance of the patient
airway and lungs, P.sub.mus is the pressure generated by the
patient diaphragm, Q.sub.total is the total flow measured by the
device, Q.sub.leak is the leak flow, and Q.sub.patient is the
patient flow. Variations of model 100b in which inertance and/or
compliance of subject interface appliance 184 are included are
contemplated within the scope of this disclosure.
[0040] Through circuit analysis of model 100b in FIG. 4, the
following equations representing relations within the system may be
derived:
P device - P patient = R hose Q + L hose dQ dt + R mask Q
##EQU00002## P device - P patient = ( R hose + R mask ) Q + L hose
dQ dt ##EQU00002.2## R circuit = R hose + R mask ##EQU00002.3## P
device - P patient = R circuit Q + L hose dQ dt ##EQU00002.4##
[0041] Additional specificity using a more detailed or more complex
parameter-based model is contemplated and would be implemented in
these equations by additional terms. In some embodiments, these
equations may be solved using a least-squared error solution:
[ Q Q . ] T [ Q Q . ] [ R circuit L hose ] = [ Q Q . ] T [ P device
- P patient ] [ n = 1 N Q [ n ] 2 n = 1 N Q [ n ] Q . [ n ] n = 1 N
Q . [ n ] 2 n = 1 N Q . [ n ] Q [ n ] ] [ R circuit L hose ] = [ Q
Q . ] T [ P device - P patient ] [ R circuit L hose ] = [ n = 0 N Q
[ n ] 2 n = 0 N Q [ n ] Q . [ n ] n = 0 N Q . [ n ] 2 n = 0 N Q . [
n ] Q [ n ] ] - 1 [ Q Q . ] T [ P device - P patient ]
##EQU00003##
[0042] In some embodiments, other solutions (and/or other data
fitting techniques) may be implemented and/or contemplated that may
be used to determine and/or estimate one or more model parameters
of the parameter-based model, such as, e.g., R.sub.circuit and
L.sub.hose, based on one or more output signals generated by one or
more sensors 142 as depicted in FIG. 1.
[0043] Estimation module 111 is configured to estimate a pressure
drop over at least part of subject interface 180. For example, the
estimated pressure drop may be between output 141 of pressure
generator 140 (and/or a point near output 141) and the point of
delivery of the pressurized flow of breathable gas (and/or a point
near the point of delivery) during delivery of the pressurized flow
of breathable gas. Pressure drop may be related to pneumatic
impedance of subject interface 180 and/or other components of
system 100. In some embodiments, estimations by estimation module
111 may be based on one or more model parameters of the
parameter-based model of model module 111, such that adjustments of
the one or more model parameters of the parameter-based model are
dynamically reflected in corresponding adjustments by estimation
module 111.
[0044] Pressure drop may vary with differences in hose length (e.g.
the length of conduit 182), conduit diameter, bends in a hose or
tube, and/or other factors, including dynamic factors that change
during a therapy session. Estimation by estimation module 111 may
be based on the generated output signals. Estimation by estimation
module 111 may be performed in an ongoing manner during a therapy
session. Alternatively, and/or simultaneously, estimations by
estimation module 111 may be triggered when a particular error
within system 100 breaches a predetermined threshold. For example,
when the difference between a particular measured parameter is
greater than an estimation of the same parameter, this occurrence
may trigger operations from one or more modules within system
100.
[0045] In some embodiments, the estimated pressure drop {circumflex
over (P)}.sub.drop may be based on a function (e.g. a differential
function) of the flow Q measured within subject interface 180
and/or elsewhere in the patient circuit, the pressure P.sub.patient
measured at or near the point of delivery of the pressurized flow
of breathable gas, the pressure measured or estimated at or near
output 141 of pressure generator 140, and/or other information. The
function may use current and past samples of the listed (vectors
of) parameters.
[0046] In some embodiments, the functions used may be based on a
particular model used to represent system 100 during use. Examples
include electrical circuit representations of the pneumatic
characteristics of system 100. Through circuit analysis, the
relations between, e.g., patient pressure and device pressure may
be represented as differential equations that may be solved in
various ways, including by way of a least-squared error solution.
Other patient circuit models are contemplated, as well as other
data fitting techniques to solve such models.
[0047] If one of the one or more sensors 142 is located at or near
output 141, the estimated pressure drop may be based on a measured
pressure at or near output 141 referred to as P.sub.device or
device pressure. Alternatively, and/or simultaneously, the
estimated pressure drop may be based on an estimated pressure at or
near output 141 referred to as {circumflex over (P)}.sub.device.
Such an estimated pressure may e.g. be based on flow Q and a priori
information including, but limited to, blower speed, valve drive
current, and/or any other mechanical unit of measurement of a
component of pressure generator 140 or of a device that pressure
generator 140 is integrated, combined, or connected with, and/or a
proxy of such a measurement.
[0048] In other words, when using {circumflex over
(P)}.sub.device:
{circumflex over (P)}.sub.drop[k]=f({right arrow over
(P)}.sub.patient, {right arrow over (Q)}, {circumflex over ({right
arrow over (P)})}.sub.device), for the k.sup.th sample in a
vector
[0049] Target module 112 is configured to determine a target
pressure P.sub.target for the pressurized flow of breathable gas
that compensates for the estimated pressure drop. The target
pressure may interchangeably be referred to as P.sub.set. The
target pressure may be in accordance with a therapy regimen, and
may dynamically change and/or titrate during one or more therapy
sessions. For example, the therapy regimen may prescribe a
particular pressure referred to as P.sub.prescription.
Determination by target module 112 may be performed in an ongoing
manner during the therapy session. The target pressure may be
adjusted as either the prescribed pressure and/or the estimated
pressure drop change.
[0050] In other words (and by way of non-limiting example):
P.sub.set[k]=P.sub.prescription[k]+{circumflex over
(P)}.sub.drop[k], for the k.sup.th sample in a vector
[0051] Control module 113 is configured to control operation of
system 100 during a therapy session. Control module 113 may be
configured to control the pressure generator to adjust one or more
levels of gas parameters of the pressurized flow of breathable gas
in accordance with one or more of a (respiratory) therapy regimen,
based on target pressures determined by target module 112, based on
one or more algorithms that control adjustments and/or changes in
the pressurized flow of breathable gas, and/or based on other
factors. Control module 113 may be configured to control pressure
generator 140 to provide the pressurized flow of breathable gas.
Control module 113 may be configured to control pressure generator
140 such that one or more gas parameters of the pressurized flow of
breathable gas are varied over time in accordance with a
respiratory therapy regimen.
[0052] Parameters determined by parameter determination module 117,
and/or received through sensors 142 may be used by control module
113 and/or other modules, e.g. in a feedback manner, to adjust one
or more therapy modes/settings/operations of system 100.
Alternatively, and/or simultaneously, signals and/or information
received through user interface 120 may be used by control module
113 and/or other modules, e.g. in a feedback manner, to adjust one
or more therapy modes/settings/operations of system 100. Control
module 113 may be configured to time its operations relative to
transitional moments in the breathing cycle of a subject, over
multiple breath cycles, and/or in any other timing relation. For
example, estimation module 111 may be configured to estimate the
pressure drop based, at least in part, on a flow rate within
subject interface 180 as determined by parameter determination
module 117.
[0053] Some respiratory therapy devices that measure P.sub.patient
may determine a pressure error P.sub.error (commonly to be used in
a feedback manner to adjust the pressure level of a pressurized
flow of breathable gas) based on the difference between either
P.sub.prescription or P.sub.target and P.sub.patient. Some
respiratory therapy devices that measure P.sub.device may determine
a pressure error P.sub.error based on the difference between either
P.sub.prescription or P.sub.target and P.sub.device. In either of
these cases the quality, stability, and/or responsiveness of the
respiratory therapy device may be negatively and/or non-negligibly
affected by the transport delay of a pressure wave propagating
through the subject interface (and/or any other tube or component
of these respiratory therapy devices). By way of non-limiting
example, transport delay may contribute to (linearly increasing)
phase lag, and/or a reduced gain margin.
[0054] System 100 accounts and/or compensates for all or most of
the negative effects of such transport delay by virtue of, in part,
basing adjustments by control module 113 on the estimated and/or
measured pressure at or near output 141 of pressure generator
140.
[0055] Error module 116 is configured to determine a pressure error
P.sub.error based on a difference between (and/or other
mathematical operations involving) the target pressure P.sub.set
(as e.g. determined by target module 112) and the measured pressure
(P.sub.device) or estimated pressure ({circumflex over
(P)}.sub.device) at or near output 141 of pressure generator 140
(as e.g. determined by parameter determination module 117 and/or
device pressure module 115). The pressure error may be determined
in an ongoing manner during (at least part of) a therapy session.
For example, a vector of the pressure error may be updated
intermittently using samples of generate output signals, estimated
pressure drop, and/or other (vectors of) parameters or information
such that subsequent determinations of the pressure error are less
than about 1 second apart, less than about 10 seconds apart, less
than about 30 seconds apart, less than about 1 minute apart, less
than about 10 minutes apart, and/or less than other time periods
apart. The pressure error may subsequently be used elsewhere in
system 100, for example by control module 113, e.g. in a feedback
manner, to adjust levels of one or more gas parameters of the
pressurized flow of breathable gas.
[0056] In other words (and by way of non-limiting example using the
estimated device pressure):
P.sub.error[k]=P.sub.set[k-1]-{circumflex over
(P)}.sub.device[k-1], for the k.sup.th sample in a vector
[0057] Rapid, ongoing, adaptive, and/or dynamic determination of
pressure drop during a therapy session facilitates both improved
quality, stability, and/or responsiveness of system 100, as well as
the ability for a patient to test more interface equipment in a
shorter amount of time.
[0058] Patient pressure module 114 is configured to determine
patient pressure P.sub.patient at or near the point of delivery of
the pressurized flow of breathable gas to the airway of subject
106. Determination by patient pressure module 114 may be based on
the generated output signals from one or more sensors 142, in
particular a sensor 142 located at or near the point of delivery,
e.g. in subject interface appliance 184.
[0059] Device pressure module 115 is configured to determine a
device pressure at or near output 141 of pressure generator 140.
Determination may be based on measurements and/or estimations. If
one of the one or more sensors 142 is located at or near output
141, determination by device pressure module 115 may be based on
the measured pressure P.sub.device. Alternatively, and/or
simultaneously, determinations by device pressure module 115 may be
based on an estimated pressure {circumflex over (P)}.sub.device.
Such an estimated pressure may e.g. be based on flow Q and a priori
information including, but limited to, blower speed, valve drive
current, and/or any other mechanical unit of measurement of a
component of pressure generator 140 or of a device that pressure
generator 140 is integrated, combined, or connected with, and/or a
proxy of such a measurement.
[0060] By way of illustration, FIG. 2 schematically illustrates an
exemplary system 100a for providing respiratory therapy to a
subject in substantially the same or similar manner as system 100
of FIG. 1. Referring to FIG. 2, pressure generator 140 provides a
pressurized flow of breathable gas, having a pressure of
P.sub.device, to subject interface 180. The output of subject
interface 180 is in fluid communication with subject 106, such that
the provided pressure is P.sub.patient. The difference between
P.sub.device and P.sub.patient is the pressure drop P.sub.drop.
Through a sensor 142 depicted above subject 106, a flow Q may be
measured. Load disturbances within system 100a may be fed back, by
way of non-limiting example to control module 113 as depicted, such
that the operation of pressure generator 140 may be adjusted to
compensate for load disturbances. Control of pressure generator may
be performed by control module 113. Through a sensor 142 depicted
below subject 106, patient pressure P.sub.patient may be
determined. The pressure drop {circumflex over (P)}.sub.drop may be
estimated by estimation module 111 based on the patient pressure,
flow Q (as determined by a sensor 142 depicted above subject 106),
and one or both of measured device pressure P.sub.device and/or
estimated device pressure {circumflex over (P)}.sub.device,
depending on the hardware configuration used for system 100a. The
device pressure may be determined by device pressure module 115.
Target module 112 may determine pressure target P.sub.target (also
referred to as P.sub.set) based on prescription pressure
P.sub.prescription and the estimated pressure drop. Error module
116 may determine pressure error P.sub.error based on the target
pressure from target module 112 and one or both of measured device
pressure P.sub.device and/or estimated device pressure {circumflex
over (P)}.sub.device. Pressure error P.sub.error, target pressure
P.sub.target, and/or the device pressure may be used by control
module 113, in addition to information about flow Q and/or the load
disturbances, to control pressure generator 140. Note that system
100a and its depicted components and interconnections in FIG. 2 are
merely exemplary, and not intended to be limiting in any way.
[0061] FIG. 3 illustrates a method 300 for providing respiratory
therapy to a subject. The operations of method 300 presented below
are intended to be illustrative. In certain embodiments, method 300
may be accomplished with one or more additional operations not
described, and/or without one or more of the operations discussed.
Additionally, the order in which the operations of method 300 are
illustrated in FIG. 3 and described below is not intended to be
limiting.
[0062] In certain embodiments, method 300 may be implemented in one
or more processing devices (e.g., a digital processor, an analog
processor, a digital circuit designed to process information, an
analog circuit designed to process information, a state machine,
and/or other mechanisms for electronically processing information).
The one or more processing devices may include one or more devices
executing some or all of the operations of method 300 in response
to instructions stored electronically on an electronic storage
medium. The one or more processing devices may include one or more
devices configured through hardware, firmware, and/or software to
be specifically designed for execution of one or more of the
operations of method 300.
[0063] At an operation 302, a pressurized flow of breathable gas is
generated for delivery to the airway of the subject via an output
of the pressure generator. In some embodiments, operation 302 is
performed by a pressure generator similar to or substantially the
same as pressure generator 140 (shown in FIG. 1 and described
herein).
[0064] At an operation 304, the pressurized flow of breathable gas
is guided from the output of the pressure generator to a point of
delivery at or near the airway of the subject via a subject
interface. The subject interface causes a pressure drop between the
output of the pressure generator and the point of delivery during
delivery of the pressurized flow of breathable gas. In some
embodiments, operation 304 is performed by a subject interface the
same as or similar to subject interface 180 (shown in FIG. 1 and
described herein).
[0065] At an operation 306, output signals conveying information
related to one or more gas parameters of the pressurized flow of
breathable gas are generated. The output signals are generated in
an ongoing manner during the therapy session. In some embodiments,
operation 306 is performed by one or more sensors the same as or
similar to sensors 142 (shown in FIG. 1 and described herein).
[0066] At an operation 308, the pressure drop between the output of
the pressure generator and the point of delivery of the pressurized
flow of breathable gas is estimated based on the generated output
signals. The estimation is performed in an ongoing manner during
the therapy session. In some embodiments, operation 308 is
performed by an estimation module the same as or similar to
estimation module 111 (shown in FIG. 1 and described herein).
[0067] At an operation 310, a target pressure for the pressurized
flow of breathable gas is determined that compensates for the
estimated pressure drop. The target pressure is in accordance with
a therapy regimen. The determination is performed in an ongoing
manner during the therapy session. In some embodiments, operation
310 is performed by a target module the same as or similar to
target module 112 (shown in FIG. 1 and described herein).
[0068] At an operation 312, levels of one or more gas parameters of
the pressurized flow of breathable gas are adjusted based on the
determined target pressure. In some embodiments, operation 312 is
performed by a control module the same as or similar to control
module 113 (shown in FIG. 1 and described herein).
[0069] In the claims, any reference signs placed between
parentheses shall not be construed as limiting the claim. The word
"comprising" or "including" does not exclude the presence of
elements or steps other than those listed in a claim. In a device
claim enumerating several means, several of these means may be
embodied by one and the same item of hardware. The word "a" or "an"
preceding an element does not exclude the presence of a plurality
of such elements. In any device claim enumerating several means,
several of these means may be embodied by one and the same item of
hardware. The mere fact that certain elements are recited in
mutually different dependent claims does not indicate that these
elements cannot be used in combination.
[0070] Although the invention has been described in detail for the
purpose of illustration based on what is currently considered to be
the most practical and preferred embodiments, it is to be
understood that such detail is solely for that purpose and that the
invention is not limited to the disclosed embodiments, but, on the
contrary, is intended to cover modifications and equivalent
arrangements that are within the spirit and scope of the appended
claims. For example, it is to be understood that the present
invention contemplates that, to the extent possible, one or more
features of any embodiment can be combined with one or more
features of any other embodiment.
* * * * *