U.S. patent application number 15/596378 was filed with the patent office on 2017-09-28 for methods and apparatus for adaptable pressure treatment of sleep disordered breathing.
The applicant listed for this patent is ResMed Limited. Invention is credited to Jeffrey Peter Armitstead, Dion Charles Chewe Martin, Dinesh Ramanan.
Application Number | 20170274165 15/596378 |
Document ID | / |
Family ID | 43991106 |
Filed Date | 2017-09-28 |
United States Patent
Application |
20170274165 |
Kind Code |
A1 |
Ramanan; Dinesh ; et
al. |
September 28, 2017 |
METHODS AND APPARATUS FOR ADAPTABLE PRESSURE TREATMENT OF SLEEP
DISORDERED BREATHING
Abstract
Respiratory pressure treatment apparatus include automated
methodologies for controlling changes to pressure in the presence
of sleep disordered breathing events. In an example apparatus,
various levels of expiratory pressure relief can provide different
pressure reductions for patient comfort during expiration (333-A,
333-B, 333-C). The control parameters for these levels may be
automatically modified based on the detection of an open airway.
Similarly, in some embodiments, the levels may be automatically
adjusted based on a detection of persistent obstruction. In still
further embodiments, control parameters associated with a rise time
of an early portion of an inspiratory pressure treatment may be
automatically adjusted upon detection of flow limitation to permit
a change to more aggressive waveforms from more comfortable
waveforms for the treatment of sleep disordered breathing
events.
Inventors: |
Ramanan; Dinesh; (Sydney,
AU) ; Armitstead; Jeffrey Peter; (Sydney, AU)
; Martin; Dion Charles Chewe; (Sydney, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ResMed Limited |
Bella Vista |
|
AU |
|
|
Family ID: |
43991106 |
Appl. No.: |
15/596378 |
Filed: |
May 16, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13509880 |
May 15, 2012 |
9682208 |
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PCT/AU2010/001536 |
Nov 16, 2010 |
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15596378 |
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61261562 |
Nov 16, 2009 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61M 2205/502 20130101;
A61M 16/0006 20140204; A61M 2230/00 20130101; A61M 16/024 20170801;
A61M 2016/003 20130101; A61M 2205/3334 20130101; A61M 2016/0027
20130101; A61M 2016/0039 20130101; A61M 16/0069 20140204; A61M
2205/50 20130101 |
International
Class: |
A61M 16/00 20060101
A61M016/00 |
Claims
1. A respiratory pressure treatment apparatus comprising: a flow
generator to generate a flow of breathable gas to a patient
interface; and a controller to control the flow generator to
deliver a flow of breathable gas at a patient interface, the flow
of breathable gas being synchronized with a respiratory cycle, the
flow of breathable gas comprising expiratory pressure portions and
inspiratory pressure portions wherein at least one of the
expiratory pressure portions is at a pressure lower than at least
one of the inspiratory pressure portions, the controller to control
an activation of a pre-termination pressure treatment protocol
during a pre-termination period wherein a change to control
parameters for setting pressure of the inspiratory pressure
portions or the expiratory pressure portion is initiated.
2. The apparatus of claim 1 wherein the change to control
parameters for setting pressure of the expiratory pressure portion
comprises an increase in a reduction in expiratory pressure.
3. The apparatus of claim 1 wherein the change to control
parameters for setting pressure of the inspiratory pressure portion
comprises a decrease in a rise time for an early portion of the
inspiratory pressure.
4. The apparatus of claim 1 wherein the change to control
parameters for setting pressure comprises a ramping down of a peak
inspiratory pressure, the ramping down being over a range from a
peak inspiratory pressure in treatment before the pre-termination
period to a pressure level of an expiratory pressure portion in the
treatment before the pre-termination period, the ramping down
comprising a gradual reduction of peak inspiratory pressure
extending over the pre-termination period.
5. The apparatus of claim 1 wherein the controller initiates the
pre-termination period as a function of a preset termination
time.
6. The apparatus of claim 1 wherein the controller initiates the
pre-termination period as a function of detection by the controller
of a lapsed time in a sleep state attributable to sleep.
7. The apparatus of claim 1 wherein the controller initiates the
pre-termination period as a function a detection by the controller
of a sleep state attributable to wakefulness.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 13/509,880, filed May 15, 2012 which is a
National Phase of PCT/AU2010/001536, filed Nov. 16, 2010, which
claims the benefit of U.S. Provisional Application No. 61/261,562,
filed Nov. 16, 2009, the disclosure of which is incorporated herein
by reference.
FIELD OF THE TECHNOLOGY
[0002] The present technology relates to methods and apparatus for
controlling treatment of sleep disordered breathing. More
particularly, it relates to methods and apparatus for pressure
control in the treatment of sleep disordered breathing.
BACKGROUND OF THE TECHNOLOGY
[0003] As described by Sullivan & Lynch in U.S. Pat. No.
5,199,424, issued on Apr. 6, 1993, the application of continuous
positive airway pressure (CPAP) has been used as a means of
treating the occurrence of obstructive sleep apnea. The patient is
connected to a positive pressure air supply by means of a nose mask
or nasal prongs. The air supply breathed by the patient is slightly
greater than atmospheric pressure. It has been found that the
application of continuous positive airway pressure provides what
can be described as a "pneumatic splint", supporting and
stabilizing the upper airway and thus eliminating the occurrence of
upper airway occlusions. It is effective in eliminating both
snoring and obstructive sleep apnea and in many cases, is effective
in treating central and mixed apnea.
[0004] In U.S. Pat. No. 5,549,106 to Gruenke, issued on Aug. 27,
1996; an apparatus is disclosed that is intended for facilitating
the respiration of a patient for treating mixed and obstructive
sleep apnea. The device is said to increase nasal air pressure
delivered to the patient's respiratory passages just prior to
inhalation and by subsequently decreasing the pressure is said to
ease exhalation effort.
[0005] In U.S. Pat. No. 5,245,995 Sullivan discusses how snoring
and abnormal breathing patterns can be detected by inspiration and
expiration pressure measurements while sleeping, thereby leading to
early indication of preobstructive episodes or other forms of
breathing disorder. Particularly, patterns of respiratory
parameters are monitored, and CPAP pressure is raised on the
detection of pre-defined patterns to provide increased airway
pressure to, ideally, subvert the occurrence of the obstructive
episodes and the other forms of breathing disorder.
[0006] As described by Berthon-Jones in U.S. Pat. No. 5,704,345,
issued on Jan. 6, 1998, various techniques are known for sensing
and detecting abnormal breathing patterns indicative of obstructed
breathing, the disclosures of which are incorporated herein by
reference. Berthon-Jones describes methods based on detecting
events such as apnea, snoring, and respiratory flow limitation,
e.g. flattening of the inspiratory portion of a flow curve.
Treatment pressure may be automatically adjusted in response to the
detected conditions. Berthon-Jones also describes methods for
detecting central apneas.
[0007] Other methods for detecting obstruction have also been used.
For example, in U.S. Pat. Nos. 5,490,502 and 5,803,066, Rapoport is
said to disclose a method and apparatus for optimizing the
controlled positive pressure to minimize the flow of air from a
flow generator while attempting to ensure that flow limitation in
the patient's airway does not occur. Controlled positive pressure
to the airway of a patient is said to be adjusted by detecting flow
limitation from the shape of an inspiratory flow waveform. The CPAP
pressure setting is raised, lowered or maintained depending on
whether flow limitation has been detected and on the previous
actions taken by the system.
[0008] In U.S. Pat. No. 5,645,053, Remmers is said to describe a
system for automatically and continuously regulating the level of
nasal pressure to an optimal value during OSA (Obstructive Sleep
Apnea) treatment. Parameters related to the shape of a time profile
of inspiratory flow are determined including a degree of roundness
and flatness of the inspiratory profile. OSA therapy is then
implemented by automatically re-evaluating an applied pressure and
continually searching for a minimum pressure required to adequately
distend a patient's pharyngeal airway.
[0009] Another type of device for treating sleep disordered
breathing is the device disclosed by Farrugia and Alder in
International Patent Application No. PCT/US2004019598 (Publ. No. WO
2004/112680) and corresponding U.S. Pat. No. 7,128,069, the
disclosure of which is incorporated herein by reference. A CPAP
pressure that is delivered to the patient may be adjusted to treat
sleep disordered breathing events such as detected partial or
complete obstruction. The delivered pressure may be slightly
reduced from the set CPAP pressure upon detection of patient
expiration. This expiratory pressure relief (EPR) can provide
comfort for the patient while the patient exhales since it may be
easier to exhale at the reduced pressure when compared to the
higher CPAP pressure. The delivered pressure is then returned to
the set CPAP pressure upon detection of patient inspiration.
[0010] Despite the availability of such devices for treating OSA,
some sleep disordered breathing events may still go untreated with
the use of some devices. Thus, it will be appreciated that there
may be a need for improved techniques and devices for addressing
the conditions of sleep disordered breathing while balancing the
desire for patient comfort.
BRIEF SUMMARY OF THE TECHNOLOGY
[0011] An aspect of certain example embodiments of the present
technology relates to automated control methodologies for
respiratory pressure treatment apparatus implemented to treat sleep
disordered breathing.
[0012] Another aspect of some embodiments the present technology is
the automated control of adjustments to pressure settings or
pressure control parameters upon a detection of sleep disordered
breathing events.
[0013] In some embodiments, automated control of various levels or
magnitudes of expiratory pressure relief can provide different
pressure reductions for patient comfort during expiration. In some
embodiments, the control parameters for these levels may be
automatically modified based on the detection of an open airway,
such as a detection of an open airway that may be contemporaneous
with a detection of an apnea and/or a reduction in a measure of
patient airflow or patient ventilation. Similarly, in some
embodiments, the levels may be automatically adjusted based on a
detection of persistent obstruction. In still further embodiments,
control parameters associated with a rise time of an early portion
of an inspiratory pressure treatment may be automatically adjusted
upon detection of flow limitation. This can change the delivered
pressure to more aggressive waveforms from more comfortable
waveforms for the treatment of sleep disordered breathing.
[0014] In accordance with one aspect of the present technology, an
adaptive form of positive airway pressure treatment is provided,
for example, in treatment of sleep disordered breathing.
Preferably, the shape of a pressure-time curve is modified based on
detection of respiratory conditions. More preferably, in response
to detection of flow limitation, or partial obstruction of the
airway, a pressure-time curve may be more aggressive, or with a
larger or steeper gradient compared to those occasions when flow
limitation, or partial obstruction is not detected, when the shape
of the pressure time curve may be more gentle, or with a smaller,
or more shallow gradient. More preferably, an initial rise of
pressure is modified based on detection of respiratory conditions.
More preferably, a pressure-time curve during an expiratory portion
of a breathing cycle of the patient is modified. In an additional
or alternative form, a magnitude of a change in pressure during an
expiratory portion of a breathing cycle of a patient is modified
based on detection of respiratory conditions. In one form, upon
detection of a first group of respiratory events, a magnitude of
change of pressure during exhalation is decreased, and upon
detection of a third group of respiratory events, the magnitude of
change of pressure during exhalation is left unchanged. Preferably,
the first group includes the absence of detection of flow
limitation. Preferably the second group includes detection of
persistent obstruction a CPAP pressure may be increased, while
leaving a magnitude of change of pressure during an expiratory
portion of the breathing cycle unchanged.
[0015] In an example embodiment, a respiratory pressure treatment
apparatus includes a flow generator to generate a flow of
breathable gas to a patient interface. Optionally, the apparatus
may include a sensor to measure the flow of breathable gas. A
controller of the apparatus is configured to control the flow
generator to deliver a flow of breathable gas with inspiratory
pressure portions and expiratory pressure portions that are
synchronized with expiration and inspiration. In this delivered
flow, an expiratory pressure portion may be at a pressure lower
than an inspiratory pressure portion. The controller may also be
configured to control a detection of an open airway apnea (e.g., b
detecting an absence of a breath or a flow limited breath) from the
measure of flow and to modify control parameters of an expiratory
pressure portion based on the detection of the open airway to
decrease a reduction in expiratory pressure while still permitting
a reduction in expiratory pressure for the expiratory pressure
portion.
[0016] Additionally or alternatively, the presence of absence of
flow limitation and/or open airway is detected using a pressure
sensor. Additionally or alternatively, an effort sensor is used to
detect and or distinguish a respiratory condition of a person.
Additionally or alternatively, a movement sensor is used to detect
and or distinguish a respiratory condition of the person.
[0017] In some embodiments of the apparatus, the detection of open
airway comprises a detection of central apnea and/or a detection of
central hypopnea. Optionally, the controller may be further
configured to discontinue the modification of the expiratory
pressure portion in response to a detection of an absence of
central apneas over a period of time.
[0018] In still further embodiments, the respiratory pressure
treatment apparatus may have a controller to control the flow
generator to deliver a synchronized flow of breathable gas with
expiratory pressure portion or portions and inspiratory pressure
portion or portions such that at least one of the expiratory
pressure portions is at a pressure lower than at least one of the
inspiratory pressure portions. The controller may also be
configured to control a detection of persistent obstruction to flow
from a measure of flow and to modify control parameters of an
expiratory pressure portion to change a pressure delivered during
the expiratory pressure portion based on the detection of the
persistent obstruction.
[0019] In some such embodiments, the controller is configured to
modify the expiratory pressure portion as a decrease in a reduction
of expiratory pressure for an expiratory phase. Optionally, the
controller may also be configured to modify the expiratory pressure
portion subsequent to one or more automated increases in a pressure
of the expiratory pressure portion made in response to a detection
of flow limitation. Optionally, the controller may be configured to
detect flow limitation by a detection of partial obstruction or
obstructive apnea. In some embodiments, controlled modifications of
the expiratory pressure portion may include disabling expiratory
pressure relief during an expiratory phase. In still other
embodiments, the controller may be configured to discontinue the
modification of the expiratory pressure portion in a response to a
detection of an absence of obstruction over a period of time.
[0020] In some embodiments of the respiratory pressure treatment
apparatus, the controller may be configured to control the flow
generator to deliver a synchronized flow of breathable gas at a
patient interface with an inspiratory pressure portion and an
expiratory pressure portion such that the inspiratory pressure
portion peaks at a first pressure higher than the expiratory
pressure. The controller may then be further configured to control
a detection of flow limitation from the measure of flow and to
modify a pressure rise time of an early part of the inspiratory
pressure portion based on the detection of flow limitation. The
controller may then control a generation of a further flow of
breathable gas at the patient interface having an inspiratory
pressure portion that peaks at the first pressure and rises in
accordance with the modified pressure rise time. For example, in
some versions, the modified pressure rise time is decreased so as
to form a more aggressive inspiratory pressure portion with the
further flow than the inspiratory pressure portion of the prior
flow when the detection of flow limitation represents a presence of
obstruction.
[0021] In some such embodiments, the controlled modification
increases the pressure rise time so as to form a more gentle
inspiratory pressure portion with the further flow than the
inspiratory pressure portion of the prior flow when the detection
of flow limitation represents an absence of obstruction.
[0022] In some embodiments, the modification of the pressure rise
time of the early part may be implemented by a selection of a set
of values from a look-up table as a function of the determined flow
limitation. Optionally, the look-up table may include scaling
factors representative of a plurality of inspiratory pressure
waveforms with different rise times.
[0023] In some embodiments of the technology, a respiratory
pressure treatment apparatus includes a flow generator to generate
a flow of breathable gas to a patient interface A controller of the
apparatus controls the flow generator to deliver a flow of
breathable gas at a patient interface. The flow of breathable gas
is synchronized with a respiratory cycle. The flow of breathable
gas also comprises expiratory pressure portions and inspiratory
pressure portions wherein at least one of the expiratory pressure
portions is at a pressure lower than at least one of the
inspiratory pressure portions. In the apparatus, the controller may
also be configured to control a detection of sleep state. It may be
further configured to change a control parameter for a rise time of
said inspiratory pressure portions based on a detection of the
sleep state.
[0024] For example, the controller may adjust the control parameter
to decrease a rise time in response to a detection of a sleep state
indicative of sleep. Moreover, the controller may ramp the control
parameter to gradually decrease a rise time in response to a
detection of a sleep state indicative of sleep. Optionally, the
controller adjusts the control parameter to increase a rise time in
response to a detection of a sleep state indicative of wakefulness.
Still further, the controller may ramp the control parameter to
gradually increase a rise time in response to a detection of a
sleep state indicative of wakefulness. Optionally, in response to a
detection of a sleep state indicative of sleep, the controller may
initiate a control protocol for adjusting the control parameter for
the rise time based on detection of a sleep disordered breathing
event. Furthermore, in response to a detection of a sleep state,
indicative of wakefulness, the controller may disengage a control
protocol for adjusting the control parameter for the rise time
based on detection of a sleep disordered breathing event.
[0025] In still further embodiments of the technology, a
respiratory pressure treatment apparatus includes a flow generator
to generate a flow of breathable gas to a patient interface. A
controller of the apparatus controls the flow generator to deliver
a flow of breathable gas at a patient interface. A controller of
the apparatus controls the flow generator to deliver a flow of
breathable gas at a patient interface. The flow of breathable gas
is synchronized with a respiratory cycle. The flow of breathable
gas also comprises expiratory pressure portions and inspiratory
pressure portions wherein at least one of the expiratory pressure
portions is at a pressure lower than at least one of the
inspiratory pressure portions. The controller of the apparatus may
also control a determination of a measure of ventilation. The
controller may then control a change to control parameters of an
expiratory pressure portion to modify a reduction in expiratory
pressure while still permitting a reduction in expiratory pressure
for the expiratory pressure portion, the controlled change being a
function of the measure of ventilation. For example, the function
of the measure of ventilation may comprises a comparison of the
measure and a target ventilation. In some such cases, the reduction
is decreased if the target ventilation exceeds the measure of
ventilation. In still other cases, the reduction is increased if
the measure of ventilation exceeds the target ventilation.
[0026] In some embodiments, the controller may be configured to
control a change to a control parameter for a rise time of said
inspiratory pressure portions where the controlled change may be a
function of the measure of ventilation. For example, the function
of the measure of ventilation may comprise a comparison of the
measure and a target ventilation. In some cases, the rise time is
increased if the target ventilation exceeds the measure of
ventilation. In some cases, the rise time is decreased if the
measure of ventilation exceeds the target ventilation.
[0027] In still further embodiments of the technology, a
respiratory pressure treatment apparatus includes a flow generator
to generate a flow of breathable gas to a patient interface. A
controller of the apparatus controls the flow generator to deliver
a flow of breathable gas at a patient interface. The flow of
breathable gas also comprises expiratory pressure portions and
inspiratory pressure portions wherein at least one of the
expiratory pressure portions is at a pressure lower than at least
one of the inspiratory pressure portions. Optionally, the
controller may control an activation of a pre-termination pressure
treatment protocol during a pre-termination period wherein a change
to control parameters for setting pressure of the inspiratory
pressure portions of the expiratory pressure portion is
initiated.
[0028] For example, in some embodiments of the pre-termination
pressure treatment protocol, the change to control parameters for
setting pressure of the expiratory pressure portion comprises an
increase in a reduction in expiratory pressure. In some embodiments
of the pre-termination pressure treatment protocol, the change to
control parameters for setting pressure of the inspiratory pressure
portion comprises a decrease in a rise time for an early portion of
the inspiratory pressure. In still further embodiments of the
pre-termination pressure treatment protocol, the change to control
parameters for setting pressure comprises a ramping down of a peak
inspiratory pressure. This peak inspiratory level in the treatment
before the pre-termination period to a pressure level of an
expiratory pressure portion also from the treatment before the
pre-termination period. In such a case, the ramping down may
comprise a gradual reduction of the peak inspiratory pressure
extending over the pre-termination period. In some such
embodiments, the controller may initiate the pre-termination period
as a function of a pre-set termination time. Optionally, the
controller may initiate the pre-termination period as a function a
detection by the controller of a lapsed time in a sleep state
attributable to sleep. Still further, the controller may initiate
the pre-termination period as a function of a detection by the
controller of a sleep state attributable to wakefulness.
[0029] Various aspects of the described example embodiments may be
combined with aspects of certain other example embodiments to
realize yet further embodiments.
[0030] Other features of the technology will be apparent from
consideration of the information contained in the following
detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The present technology is illustrated by way of example, and
not by way of limitation, in the figures of the accompanying
drawings, in which like reference numerals refer to similar
elements including:
[0032] FIG. 1 illustrates example components of respiratory
pressure treatment device of the present technology;
[0033] FIG. 2 is an example methodology for expiratory pressure
relief control;
[0034] FIG. 3 illustrates an example pressure wave form with
adjustments in accordance with the methodology of FIG. 2;
[0035] FIG. 4 is an further example methodology for expiratory
pressure relief control;
[0036] FIG. 5 illustrates an example pressure waveform with
adjustments in accordance with the methodology of FIG. 4;
[0037] FIG. 6 is a further example methodology for pressure
treatment control of the present technology;
[0038] FIG. 7 illustrates several example inspiratory pressure
waveforms with adjustments in accordance with the example
methodology of FIG. 6;
[0039] FIG. 8 is a data table with illustrative inspiratory
pressure waveform scaling factor data in accordance with an example
embodiment of the methodology of FIG. 6;
[0040] FIG. 9 illustrates a block diagram of an example controller
architecture of the present technology; and
[0041] FIG. 10 is a graph of a pressure time curve illustrating a
ramp down procedure.
DETAILED DESCRIPTION
[0042] The present technology involves methods and devices for the
treatment of patients with sleep disordered breathing (SDB). One
embodiment of a respiratory pressure treatment apparatus 102 for
implementing the present technology is illustrated in FIG. 1. In
the embodiment, the device includes a controller 104 to detect SDB
events and make changes to treatment pressure in accordance with
one or more control methodologies. The apparatus 102 will also
include a flow generator such as such a servo-controlled blower
110. The apparatus may be configured for coupling with a patient
interface, such as a delivery tube 112 and a mask 108. The mask may
optionally be a nasal mask, nose & mouth mask, full-face mask
of nasal pillows other device to provide a seal with the patient's
respiratory system so as to permit a pressure treatment at one or
more pressures above atmospheric or ambient pressure.
[0043] The apparatus 102 also may include sensors, such as a
pressure sensor 105 and/or flow sensor 106. In such an embodiment,
the pressure sensor 105, such as a pressure transducer, may measure
the pressure generated by the blower 110 and generate a pressure
signal p(t) indicative of the measurements of pressure. Similarly,
the flow sensor generates a signal representative of the patient's
respiratory flow. For example, flow proximate to the patient
interface 108 or a sense tube (not shown) may be measured using
pneumotachograph and differential pressure transducer or similar
device such as one employing a bundle of tubes or ducts to derive a
flow signal f(t). Other sensors may be utilized to generate data
indicative of flow or pressure for the purposes of the control
methodologies of the apparatus.
[0044] Based on flow f(t) and pressure p(t) signals, the controller
104 with one or more processors generates blower control signals.
For example, the controller may generate a desired pressure set
point and servo-control the blower to meet the set point by
comparing the setpoint with the measured condition of the pressure
sensor. Thus, the controller 104 may make controlled changes to the
pressure delivered to the patient interface by the blower 110.
Optionally, such changes to pressure may be implemented by
controlling an exhaust with a mechanical release valve (not shown)
to increase or decrease the exhaust while maintaining a relatively
constant blower speed. Such changes in pressure may be determined
by automated detection of SDB events in the controller by analysis
of data from a flow signal as discussed in more detail herein. With
such a controller or processor, the apparatus can be used for many
different pressure treatment therapies, such as the pressure
treatments for sleep disordered by breathing by adjusting a
suitable pressure delivery equation.
[0045] Thus, the controller 104 will typically include a processor
configured to implement particular control methodologies such as
the algorithms described in more detail herein. To this end, the
controller may include integrated chips, a memory and/or other
control instruction, data or information storage medium. For
example, programmed instructions encompassing such a control
methodology may be coded on integrated chips in the memory of the
device. Such instructions may also or alternatively be loaded as
software or firmware using an appropriate data storage medium.
[0046] For example, the controller may be configured to generate a
CPAP pressure treatment with expiratory pressure relief as
described by U.S. Pat. No. 7,128,069, the entire disclosure of
which is incorporated herein by reference. Thus, it may set a
treatment CPAP pressure for each inspiration, which may be chosen
(automatically or manually to treat sleep disordered breathing
events) and may reduce the pressure by a chosen level of reduction
for expiratory pressure relief (EPR) depending on the control
methodologies discussed herein. The EPR levels can make breathing
more comfortable for the patient. For example, such an EPR control
scheme may be implemented with several different levels or
magnitudes of pressure reduction (e.g., Level 0=0 cmH.sub.2O; Level
1=1.5 cmH.sub.2O, Level 2=2 cmH.sub.2O, Level 3.5=3 cmH.sub.2O).
Additional EPR levels may also be implemented and other pressure
amounts may be associated with each level. Thus, if a CPAP pressure
is prescribed or automatically adjusted to 8 cmH.sub.2O to treat
SDB and a level 2 EPR is chosen, pressure during inspiration would
be at the CPAP pressure and pressure during expiration would be
reduced to 6 cmH.sub.2O. Known methods for detecting patient
inspiratory phase (i.e., triggering) and expiratory phase (i.e.,
cycling) based on data from the sensors may be implemented for the
pressure changes to be synchronized with the respiratory cycle.
When the presently set EPR level is changed to another level
associated with a lower pressure, it would result in a reduction in
Pressure Support ("PS") where pressure support is considered the
difference between the inspiratory pressure level ("IPL") and the
expiratory pressure level ("EPL"). (i.e., PS=IPL-EPL)).
A. Open Airway EPR Adjustments
[0047] In some patients the level of EPR may be enough to amplify
an existing predisposition to periodic breathing. The dual level
waveform, although comfortable and an inefficient form of
ventilation, could drive the arterial CO.sub.2 down below the
apneic threshold and cause a central apnoea. Subsequently, the
patient would begin breathing (when the CO.sub.2 eupnic threshold
is reached). This may constitute a periodic breathing sequence
similar to Cheyne-Stokes respiration. Accordingly, in some
embodiments of the present technology, the selection of the level
of EPR may be automated based on the detection of one or more SDB
events to minimize such a situation.
[0048] One such example methodology or algorithm of the controller
104 is illustrated in the flow chart of FIG. 2. At 220, the
controller controls a respiratory pressure treatment apparatus 102
so as to generate a flow of breathable gas at the patient
interface. The flow of breathable gas can be synchronized with a
respiratory cycle of the patient, for example, upon detection of
inspiration or expiration through analysis of pressure and/or flow
data from the sensors. The generated flow of breathable gas may
then include inspiratory pressure portions and expiratory pressure
portions so that the EPR level establishes an expiratory pressure
portion at a pressure lower than an inspiratory pressure portion at
a pressure lower than an inspiratory pressure portion. At 222, the
flow of breathable gas to the patient interface is measured, for
example, with the flow sensor 106.
[0049] At 224, based on the measure of flow, the controller detects
whether or not an open airway exists, which in some embodiments may
be contemporaneous with a detection of and apnea and/or a reduction
in a measure of patient airflow volume or patient ventilation. For
example, the controller may determine whether or not a central
apnea or a central hypopnea is occurring. In one such embodiment,
the detection of central apnea may be made by any of the
methodologies described in U.S. Pat. No. 5,704,345. For example,
the detection of central apnea may be made by a determination of
patency of the airway (e.g. an open airway) in conjunction with a
significant reduction in patient respiratory flow below a
threshold. The patency determination may be performed by applying
an oscillatory pressure waveform of known frequency to a patient's
airway, calculating the magnitude of the component of the flow
signal at the known frequency induced by the oscillatory pressure
waveform and comparing the calculated magnitude with a threshold
value. Other methods for detection of central apnea may also be
implemented.
[0050] In some embodiments, the central hypopnea may be determined
by detecting both a hypopnea and an open airway. For example, the
following may be detected: (a) a partial reduction in breathing or
ventilation that lasts a period of time (e.g., at least 10 seconds)
during sleep and (b) either an absence of partial obstruction or an
open airway. For example, the controller may determine from the
measure of flow a 10 second reduction in a measured volume of flow
by at least 50%. It may also consider the absence of flow
limitation (e.g., partial obstruction) by detecting an absence of
flow flattening using a flattening index as discussed in U.S. Pat.
No. 5,704,345. Patency may also be detected as described in U.S.
Pat. No. 5,704,345. A flattening index may be a real number
calculated using flow data from a patient's inspiratory waveform.
An absence of partial obstruction may also be determined from a
degree of roundness of the flow signal. Other methods for detection
of hypopnea, open airway, partial reduction in breathing and
partial obstruction may also be implemented. By way for further
example, methods for determining hypopnea as disclosed in U.S.
Patent Application No. 61/184,592, entitled "Methods and Devices
for the Detection of Hypopnoea" filed on Jun. 5, 2009, the
disclosure of which is incorporated herein by reference, may also
be implemented. Similarly, methods of determining flow limitation
or an absence thereof, may be implemented in accordance with
PCT/AU2008/000647 (WO/2008/138040), filed on May 9, 2008, the
disclosure of which is incorporated herein by reference.
[0051] At step 226, the controller may modify control parameters of
an expiratory pressure portion based on the detection of an open
airway, which may correspond with a contemporaneous detection of an
apnea and/or a reduction in patient airflow, so as to decrease a
reduction in expiratory pressure while still permitting a reduction
in expiratory pressure for the expiratory pressure portion. For
example, if an EPR level is currently set to level 3, upon
detection of either a central apnea or a central hypopnea
condition, the EPR level may be decremented to level 2. In response
thereto, the flow generator would decrease the pressure reduction
delivered during a subsequent expiratory phase. Because EPR is a
reduction from the inspiratory level of treatment pressure (e.g.,
the CPAP treatment pressure), it will be recognized that these
decreases in pressure reduction would result in a decrease in
pressure support (PS).
[0052] In some embodiments, a continued detection of central apnea
or central hypopnea condition (or additional detections) by the
controller may further decrement the EPR level. If a sufficient
number of central apneas are detected, the EPR level may be
decremented to an EPR Level 0. In such a case, the pressure
delivered by the flow generator under control of the controller
would be essentially a relatively constant pressure across both
inspiration and expiration. In some embodiments of this technology,
this termination of the EPR reduction might be continued for the
remainder of the treatment session (e.g., the nights sleep
session.) such that the CPAP pressure will continue to be delivered
during subsequent expiratory phases of the patient's respiratory
cycles of the session. In such a case, the resetting of the EPR
reductions can be enabled once the apparatus is reset or restarted
for a new treatment session.
[0053] However, in some applications of the technology, the EPR
Level may be incremented thereafter if the controller detects an
open airway that corresponds with an apnea and/or a reduction in
patient airflow volume for a period of time in a post-detection
pause. For example, if after several minutes or after a
predetermined number of respiratory cycles, central apneas and
central hypopneas are no longer detected, the level of EPR may be
incremented or reset to the maximum comfort level (e.g., EPR level
3). Optionally, incrementing of the EPR level may be gradual so as
to eventually increase the EPR to a maximum level to provide a
maximum EPR comfort pressure setting in the continued absence of
the detection of the open airway apnea or patient airflow
reduction. For example, additional increments to the EPR may be
made if after several minutes or after a predetermined number of
respiratory cycles, central apneas and central hypopneas are still
not detected.
[0054] An example pressure treatment according to such a control
methodology is illustrated in FIG. 3. As shown at T1, the wave form
initially illustrates a pressure treatment at an EPR Level 3 at
line 333-A. As shown at T2, upon detection of a central apnea or
central hypopnea, the EPR level is reduced to the EPR Level 2 shown
at line 333-B. As shown at T3, upon continued detection of the
central apnea or central hypopnea, the EPR level is again reduced
to EPR Level 1 shown a line 333-C. As shown at T4, upon still
continued detection of the central apnea or central hypopnea, the
EPR level is again reduced to EPR Level 0 such that it remains at
the same pressure as the CPAP pressure during both phases of the
respiratory cycle (i.e., inspiration and expiration). As shown at
T5, after a post-detection pause, a chosen level of EPR may then
resume. Optionally, this resumption setting may be to the most
comfortable setting (e.g., EPR Level 3) as shown or the level may
gradually increment to the most comfortable setting with each
increment occurring after a period of time (e.g., minutes or a
chosen number of respiratory cycles) without a detection of the
central events.
B. Persistent Obstruction EPR Adjustments
[0055] In some versions of the present technology, the selection of
the level of EPR may be automated based on the detection of one or
more SDB events by the example methodology or algorithm of the
controller 104 as illustrated in the flow chart of FIG. 4. At 440,
the controller controls a respiratory pressure treatment apparatus
102 so as to generate a flow of breathable gas at the patient
interface. The flow of breathable gas can be synchronized with a
respiratory cycle of the patient, for example, upon detection of
inspiration or expiration through analysis of pressure and/or flow
data from the sensors. The generated flow of breathable gas may
then include inspiratory pressure portions and expiratory pressure
portions so that the EPR level establishes an expiratory pressure
portion at a pressure lower than an inspiratory pressure portion.
At 442, the flow of breathable gas to the patient interface is
measured, for example, with the flow sensor 106.
[0056] At 444, based on the measure of flow, the controller detects
whether or not a persistent obstruction to flow exists. For
example, the detection of persistent obstruction may be determined
from a measure of flow limitation, partial obstruction, obstructive
apnea, flow flattening and or flow roundness that does not
substantially change during a period of time such as a number of
minutes (e.g., 5 or more) or a number of respiratory cycles (e.g.,
10 or more). During such time, the controller may attempt to treat
the detected obstruction with one or more successive increases to
the CPAP treatment pressure that is delivered during inspiration,
but the set EPR level would remain unchanged. Thus, the pressure
support may stay the same during this treatment adjustment period.
In some embodiments, the persistent obstruction may be determined
based on the existence of detected obstruction despite repeated
changes to a therapy pressure. (e.g., (a) several step increases in
the CPAP pressure and the continued presence of partial obstruction
or (b) several such increases up to a maximum CPAP pressure and the
continued presence of partial obstruction.)
[0057] At 446, the controller 104 would then automatically modify
control parameters for at least one of the expiratory pressure
portions to change a pressure delivered during the expiratory
pressure portion based on the detection of the persistent
obstruction. For example, in the event that one or more treatment
changes does not resolve the obstruction and/or the detected airway
obstruction continues to exist for the period of time, this
detection of persistent obstruction can serve as logic to control a
reduction of the EPR level, such as a decrement of the currently
set EPR level. In the event that the persistent obstruction
condition remains after a further period of time (e.g., minutes or
cycles), then the EPR level may again be decremented. Additional
decrements may also be implemented to eventually reduce the EPR
level to the EPR Level 0 at which time there would be no reduction
in pressure during expiration.
[0058] An example pressure treatment according to such a control
methodology is illustrated in FIG. 5. As shown at TT1, the waveform
initially illustrates a pressure treatment at an EPR Level 3 at
line 555-A. AS shown at TT2, upon detection of partial obstruction
(e.g., flow flattening, degree of roundness or flow limitation,
etc.), the CPAP treatment pressure or SD therapy pressure may be
increased. Since the EPR level is unchanged at line 555-A, the
pressure support (PS) remains the same with respect to the prior
respiratory cycle at TT1.
[0059] At TT3, another obstruction is detected or the same
obstruction is detected. Since the persistence period PP has not
lapsed, which may be determined by a timer or respiratory cycle
counter and a threshold, a CPAP pressure treatment increase is
applied. Again the previously set EPR level and the pressure
support PSA remains the same.
[0060] However, at TT4, since the obstruction is still detected and
a persistence time period PP has lapsed or the maximum CPAP
pressure has been reached, the EPR level is decremented so that the
expiratory pressure relief is reduced as shown at line 555-B.
Consequently, the pressure support is also reduced. Again at TTS,
since obstruction is still detected, the EPR level is decremented
so that the expiratory pressure relief Is reduced as shown at line
555-C with a consequent reduction in pressure support. Similarly at
TT6, since obstruction is still detected, the EPR level is
decremented so that the expiratory pressure relief is reduced to
EPR level 0 so as to maintain the CPAP pressure of inspiration
during expiration. Finally, at TT7, obstruction is no longer
detected and an optional pause period as previously mentioned has
lapsed. Thus, the EPR level may be incremented or reset to the most
comfortable setting. However, in some embodiments of this
technology, once the EPR reduction has been terminated upon
reaching EPR Level 0, this termination might continue for the
remainder of the treatment session (e.g., the nights sleep
session.) or until the apparatus is reset or restarted for a new
treatment session.
[0061] In the above pressure treatment illustration, consecutive
decreases in the EPR level may be controlled in consecutive
respiratory cycles in the presence of a detection of obstruction in
each such cycle. However, in some embodiments, each consecutive
decrease may be made after an optional pause time period, (e.g.,
several respiratory cycles) to provide the device an opportunity to
impact the detected obstruction a the new EPR level setting before
an additional decrease in the EPR level is made. An example of such
a change is illustrated between time markers TT5 and TT6.
[0062] Additionally, although the illustrated pressure waveforms of
FIGS. 3 and 5 show that there is no increase to the EPR Level
setting until reaching the lowest EPR level, such an increase may
be made before the lowest EPR level (i.e., a level with no EPR
pressure reduction) in the absence of a detection of obstruction or
central hypopnea or central apnea. Thus, in FIG. 5, if at TT5 no
obstruction had been detected and an optional pause time period has
lapsed, the control of the device may make an increase in the EPR
level to increase the reduction of expiratory pressure from the
CPAP treatment pressure. Similarly, in FIG. 3, if at T3 no central
events had been detected and an optional pause time period has
lapsed, the control of the device may make an increase in the EPR
level to increase the reduction of expiratory pressure from the
CPAP treatment pressure.
[0063] Optionally, one or more of the aforementioned features may
be combined with methods for automated adjustments to end
expiratory pressure (auto-EEP). For example, an auto-EEP algorithm
might also be implemented into the controller to make adjustments
to the end expiratory pressure in an attempt to abolish
closed-airway apneas. These adjustments may be attempted before
making the aforementioned adjustments that would reduce the EPR
level and thereby before making any reduction to the pressure
support. Optionally, the EEP algorithm could also determine an EEP
that is a minimum pressure required to abolish obstructive apnoeas.
This could then be implemented so as to prevent an automated
selection of an EPR level that would permit the pressure set during
expiration to go below the established minimum EEP. For example,
when incrementing to a higher EPR level, a check might first
compare the possible resultant expiratory pressure (i.e.,
CPAP_pressure minus EPR_pressure) and only permit the EPR level
change if the resultant pressure would be higher than the minimum
EEP.
[0064] In still further modifications of the technology, pressure
adjustments based on the detection of SDB events may be made to the
EPR level before making modifications to the CPAP treatment
pressure. For example, the logic of the controller may be
configured to automatically decrease the EPR level when one or more
SDB events are detected. This may be done incrementally. If the
problem persists, such as if a time period has elapsed and the
obstruction is still detected or if the EPR has been incrementally
reduced to level 0 and SDB events are still detected, then
automated adjustments may be made to CPAP treatment pressure (e.g.,
with automated increments of the CPAP pressure up to a maximum CPAP
treatment pressure). An example of a device with such an automated
control of the CPAP treatment pressure level is described in U.S.
Pat. No. 5,704,345. Optionally, such automated pressure adjustments
may be made by shifting the pressure curve.
C. Obstructed Airway Inspiratory Adjustments
[0065] In some embodiments of the present technology, the control
settings for returning the pressure to the CPAP level during
inspiration from the level of pressure reduced by the EPR setting
may also be automatically adjusted based on the detection of one or
more SDB events. An example of such an automated control
methodology or algorithm of the controller 104 is illustrated in
the flow chart of FIG. 6. At 660, the controller controls a
respiratory pressure treatment apparatus 102 so as to generate a
flow of breathable gas at the patient interface. The flow of
breathable gas can be synchronized with a respiratory cycle of the
patient, for example, upon detection of inspiration or expiration
through analysis of pressure and/or flow data form the sensors. The
generated flow of breathable gas may then include inspiratory
pressure portions and expiratory pressure portions. With the EPR
settings, the inspiratory portion can peak at a pressure that is
higher than the pressure delivered during expiration. At 662, the
flow of breathable gas to the patient interface is measured, for
example, with the flow sensor 106. At 664, based on the measure of
flow, a measure of partial obstruction or flow limitation is
determined.
[0066] At 666, based on the detection of flow limitation, the
controller can modify a pressure rise time of an early part of the
inspiratory pressure portion. The controller can then control a
generation of a further flow of breathable gas at the patient
interface with an inspiratory pressure that peaks at the pressure
from the prior inspiratory cycle but rises according to the
pressure rise time modification.
[0067] Example inspiratory pressure waveforms that may be
controlled by the aforementioned methodology are illustrated in the
graph of FIG. 7. In this example, although the number of different
waveforms can be change, four inspiratory waveforms are shown that
may be selectively generated by the controller as a function of a
detection of partial obstruction or flow limitation. As
illustrated, waveform 777A may be considered a least aggressive
inspiratory waveform. When considered with a shared peak at the
CPAP pressure level, the remaining waveforms 777B, 777C and 777D,
have rise times R3, R2 and R1 in their early portions (e.g., before
middle inspiration at T.sub.i/2) with respect to a reference
pressure level P1.sub.ref that are lesser than the rise time R4 of
the early part of waveform 777A. When considering a peak at a
common CPAP pressure level, the latter portions may also have
different rise times. In the example, the rise in a latter portion
of the waveform 777A has a shorter rise time (R8 minus R4) than the
rise time (R7 minus R3) of the wave form 777B with respect to
reference pressure levels P1.sub.ref and P2.sub.ref. Similarly,
waveform 777A has a shorter rise time (R8 minus R4) than the rise
time (R6 minus R2) of the waveform 777C and shorter than the rise
time (R5 minus R1) pf waveform 777D.
[0068] As illustrated, the early portions of the waveforms may be
characterized as being progressively more aggressive. In this
regard, waveform 777B is more aggressive than 777A. Similarly,
waveform 777C is more aggressive than 777B and waveform 777D is
more aggressive than 777C. In embodiments of the present
technology, the flow generator may progressively deliver more
aggressive waveforms as a function of detected obstructive
events.
[0069] For example, an obstruction or flow limitation index may be
used for a scaling function or for an index to a look-up table for
adjustment of the pressure verses time inspiratory flow curve. One
example is illustrated in the table of FIG. 8 which can be
implemented in a pressure delivery equation such as the
following:
Pressure =[RESP*EPR*F(O.sub.i, T.sub.i)]+[CPAP-EPR]; [0070] where:
[0071] RESP is 1 for detected inspiration and 0 for detected
expiration; [0072] CPAP is a therapeutic pressure for treatment of
sleep disordered breathing events; [0073] EPR is the pressure of
the currently set EPR level; [0074] O.sub.i is an obstruction index
such as a flow limitation index or a flow flattening index; [0075]
T.sub.i is a time index during inspiration; [0076] F is a function
to obtain a rise time scaling factor from the table illustrated in
FIG. 8 based on an inspiratory time index (e.g., T.sub.1, T.sub.2,
T.sub.3 . . . T.sub.N) and the obstruction index. This data of the
table may implement an adjustment of the pressure setting according
to data representing the rise time profiles illustrated in FIG. 7.
In this example, for higher obstruction indices where there is a
greater degree or partial obstruction, the rise time of the early
portion of the pressure waveform is lower to implement more
aggressive waveforms. For lower obstruction indices where there is
a lower degree of partial obstruction, the rise time of the early
portion of the pressure waveform is higher to implement less
aggressive inspiratory waveform. However, the peak pressure during
inspiration may still rise to the CPAP treatment pressure. This
CPAP treatment pressure setting may be determined and adjusted by
other methods (e.g., by automatic detection or a manual setting).
Upon detection of expiration, the pressure equation will regulate
the pressure at the EPR level below the CPAP treatment pressure
setting.
[0077] According, with such a system having expiratory pressure
relief (EPR) and less aggressive inspiratory waveforms (e.g., a
gentle rise time), an SDB patient may experience greater comfort
while falling asleep or progressing from an awake state to sleep
state. However, these comfort adjustments might not be necessary
once the patient is in a sleep state (except in the case of high
CPAP pressure treatment settings such as a pressure above .about.14
cmH.sub.2O in which case it will more than likely improve comfort
during sleep as well).
[0078] For example, a gentle rise time during sleep might permit a
patient's airway to begin to experience partial obstruction and
become unstable. If the pressure support (PS) is not aggressive
enough, it may lead to airway collapse (obstructive apnea).
Accordingly, when a patient begins to fall asleep, and the
obstruction index is a 0, the delivered waveform would be least
aggressive and most comfortable permitting the patient to fall
asleep easier. However, as the patient's airway begins to obstruct
and flow limitation is detected, the obstruction index will
increase and thereby adapt the waveform to increase the
aggressiveness of the early inspiratory part of the waveform
according to the above methodology.
D. Sleep State Based Pressure Adjustments
[0079] In some embodiments of the technology, pressure adjustments,
such as the level of EPR and/or aggressiveness of early inspiratory
pressure, may be automated based on a detection of a sleep state of
a patient using the respiratory pressure treatment apparatus 102.
In such embodiments, the controller may be implemented as or with a
sleep state director. For example, the controller may use signals
or data from one or more of electroencephalogram (EEG),
Electrocardiography (ECG), blood gas saturation (e.g.,
Pulse-Oximeter), Effort Bands, Accelerometer, Non-contact
respiratory flow/ECG sensor, respiratory flow sensor and/or any
other sensor means to determine or calculate sleep states of a
patient. Thus, the controller may be configured to differentiate
between Awake, REM Sleep and NREM Sleep states based on the signals
or data. An example of a suitable sleep state detector is described
in International Patent Application No. PCT/AU2010/000894, the
disclosure of which is incorporated herein by reference. Such a
controller may then have EPR settings and/or rise time settings
that are associated with different detectable sleep states in a
memory of the apparatus.
[0080] With such a controller, EPR may be primarily used as a
comfort feature, helping the patient expire against a lower
pressure during wakefulness/sleep onset, where breathing still has
some level of voluntary control. It may not be necessary then for
the controller to implement EPR during REM and NREM sleep states.
Thus, in some embodiments of the technology the EPR may be
activated or deactivated depending on sleep state, such as being
activated when an AWAKE state is detected and/or deactivated when a
REM or NREM state is detected.
[0081] In some embodiments, the controller of the treatment
apparatus may be configured to set EPR and/or aggressiveness of
inspiratory pressure rise time with one or more of the following
treatment options based on sleep state:
[0082] i.) During a detected AWAKE State the EPR may be set by the
controller to a high level (e.g., EPR level 3). Once the controller
detects that the patient's sleep state has changed to a SLEEP state
(either REM or NERM states), the controller may adjust down the EPR
level from an awake level (e.g., a high or higher EPR) to a sleep
level (e.g., a low or lower level or a zero level EPR). Optionally,
this adjustment may be ramped down such as by successively
decrementing the previously set EPR level over a pre-set time
period (e.g., 1 level per consecutive 5 minute interval) or a
pre-set number of respiratory cycles) until the EPR reaches the
desired sleep level, which may be a preset in the settings of the
controller.
[0083] In such embodiments, the EPR level during sleep can be
decremented to any suitable or preset EPR level depending on what
is appropriate for the patient (e.g., from Level 3 to level 0 o
level 3 to level 1). Thereafter, if the patient is sleeping and the
controller detects a transition into an AWAKE state, then the
controller may be configured to raise the EPR level, such as by
ramping up, to a suitable awake level from the presently set sleep
level. Optionally, the ramp period (either up or down) may be set
to any value by input from a physician to adjust configuration
parameters of the controller, depending on what is appropriate for
the patient. Thus, the controller may successively increment (or
decrement) the EPR level over a pre-set time period (e.g., 1 level
per consecutive 5 minute interval) or a pre-set number of
respiratory cycles (e.g., 1 level per 10 detected respiratory
cycles) until the EPR level is set to the desired awake (or sleep)
level.
[0084] ii.) During a detected AWAKE state, the controller may
adjust or set the EPR level and may also adjust and/or set a rise
time at suitable levels as previously discussed. Once the
controller detects that the patient's sleep condition has changed
to a SLEEP state (e.g., either a REM state or NREM state), the rise
time setting of the early portion of the inspiratory waveform may
be reduced by the controller to a sleep level (e.g., to be more
aggressive in the nature of its response). Optionally, this
reduction may be an incremental change so as to make the change
gradual over a chosen time period or number of respiratory cycles,
etc. In this way, a suitable rise time may be pre-set in the
apparatus to have an association with a sleep state. This pre-set
rise time may be manually input by a physician or anyone else who
is administering therapy for the patient.
[0085] Optionally, the detection of a sleep state indicative of
sleep may initiate the previously discussed automated control
algorithm that adjusts the rise time (inspiratory portion
aggressiveness) based on the automated detection of the SDB events
(e.g., flow flattening or obstruction) so as to deliver
progressively more aggressive rise times with the detection of such
events and less aggressive rise times in the absence of the
detection of such events. If the patient is sleeping and
transitions in an AWAKE state, the rise time may be changed (e.g.,
by ramping incrementally) to an awake level (thereby making the
nature of the response less aggressive). This Awake state may then
also serve as a basis to control disengaging of the control
protocol that changes the rise times in response to the detection
of SDB events.
E. Pressure Adjustments by Ventilation
[0086] In some embodiments, the controller may be configured to
determine a measure of ventilation. Such a measure may be, for
example, a volume derived from a flow signal such as a tidal
volume, a minute volume or a low pass filtered absolute value of a
flow signal divided in half. Other measures of ventilation may also
be implemented. Such measures of ventilation may in turn serve as
part of the logic of the controller for selecting or setting the
ERP level and/or rise time profile. In this respect, the EPR level
or rise time profile may be set in response to the ventilation
parameter as opposed to an obstructive breathing detection index
such as apnea index, flow flattening, snore, etc.) For example, the
ventilation measure, such as certain detected decreases, may
control a decrease in the EPR level and/or a more aggressive
inspiratory rise time profile (e.g., a profile with a shorter rise
time). Moreover, detected increases in the ventilation measure may
also serve to control or permit increases in the EPR level and/or a
less aggressive inspiratory rise time profile (e.g., a profile with
a longer rise time). In one such embodiment, if the ventilation
falls below a target ventilation (such as a pre-set ventilation
target of an average ventilation determined from a prior treatment
session or a prior period of treatment) by some threshold amount,
the drop may trigger the controller to make a decrease in the EPR
level and/or am increase in the aggressiveness of the rise time of
the early inspiratory portion of the pressure wave form. Additional
ventilation drops may trigger yet further EPR level reductions
and/or rise time decreases down to some minimum. Similarly, in one
such embodiment, if the ventilation rises above a target
ventilation by some threshold amount, the rise may trigger the
controller to make an increase in the EPR level and/or an decrease
in the aggressiveness of the rise time of the early inspiratory
portion of the pressure wave form. Additional ventilation rises may
trigger yet further EPR level increases and/or rise time increases
up to some maximum.
F. Certain Recurring Events
[0087] In some embodiments, upon detection of several recurring SDB
events, over-ventilation and/or long pauses that are not long
enough to be a central apnea, an automated adjustment to pressure
may involve an increase of the pressure support baseline and
reduction of the pressure support or a reduction of CPAP and
pressure support.
G. Pre-Termination Treatment Adjustments
[0088] In some embodiments, the controller may be configured to
make adjustments to the treatment protocol in conjunction with an
anticipated or detected ending of a treatment session. This may
permit patients to wake more comfortably by initiating pressure
changes to more comfortable levels (e.g., lower) from more
therapeutic levels (e.g., higher) at or near the time that the
patient wakes up from sleep. Such a treatment adjustment may be
particularly helpful where higher therapy levels are utilized
during sleep, such as in the case of Chronic Obstructive Pulmonary
Disease (C.O.P.D.) patients.
[0089] For example, the controller may be configured with a timer
or clock and a time threshold may be configured with a timer or
clock and a time threshold may be determined or set (e.g., by the
patient) to a particular time at which the patient using the device
will wake up from sleep and/or the apparatus will be turned off
(automatically or manually). Thus, the set time can serve as a
timing threshold that may be compared with a timer or clock of the
apparatus. This set time may then represent a wake up time or the
time the patient will stop a current treatment session with the
respiratory treatment apparatus. With such an ending time, the
controller may be configured with a pre-termination control
methodology that modifies the treatment settings of the device for
the patient during a period of time (e.g., a number of minutes
etc.) that immediately precedes the termination time when the
patient will wake up or the apparatus will be turned off. For
example, this pre-termination period may be initiated when a timer
of the apparatus exceeds the timing threshold less the amount of
time of the pre-termination period. A pre-termination treatment
protocol may be initiated by the controller during this time
period.
[0090] For example, in some embodiments, during this
pre-termination period, the EPR may be initiated (e.g., activated)
or the EPR level may be gradually increased.
[0091] In some embodiments, during this pre-termination period, the
therapeutic treatment pressure setting (e.g., the peak pressure
level associated with an IPAP) may be reduced or gradually ramped
down by the controller of the apparatus. Optionally, this reduction
or gradual ramp down may be to the level of pressure of the EPR
setting at the time that the apparatus initiates the
pre-termination period. For example, if the therapeutic treatment
pressure is at 10 cm H.sub.2O and the EPR is set at level 3 at the
time that the pre-termination period initiated by the controller,
the therapeutic treatment pressure may be gradually ramped down to
the effective pressure level of the EPR setting (e.g., 10 cm
H.sub.2O minus 3 cm H.sub.2O=7 cm H.sub.2O) over the course of the
pre-termination period such that the pre-termination period starts
at a higher pressure and ends at a lower pressure. For example,
this typically will take place over a number of respiratory cycles
or a time on the order of minutes, as opposed to in a single
respiratory cycle. Optionally, the pressure time curve of the
ramping down of pressure over this pre-termination period may be
linear or it may be some other function such as a step-wise
function or other curve. Still further, the treatment pressure may
be ramped down to some other pre-set pressure level from the level
at which the treatment pressure setting was set at the time of
initiation of the pre-termination period An example ramp down
during a pre-termination period is illustrated in the pressure
verses time graph of FIG. 10. Although FIG. 10 illustrates a
ramping down of treatment pressure, in some embodiments the control
change during the pre-termination period may include either
additionally or alternatively a change of the rise time profile of
the inspiratory pressure. This rise time profile change may involve
controlling a gradual change from more aggressive to less
aggressive pressure time profiles over the course of the
pre-termination time period.
[0092] Optionally, in some embodiments, the controller may be
configured with a logic to estimate a time when the patient will
wake or terminate treatment with the apparatus so as to assess a
suitable time to initiate the pre-termination period. For example,
it may judge that a patient is likely to wake up at a certain
amount of time after beginning treatment (e.g., some machine run
time or machine use time in a range of 6 to 8 hours from the start
of treatment). This estimate may serve as the timing threshold.
Optionally, the timing threshold may be determined by the
controller monitoring the machine run time or the time of use by
the patient in one or more prior treatment sessions. For example,
an average run time or average time of use of several prior
treatment sessions may be determined and used to predict when a new
treatment session is likely to end so as to serve as the timing
threshold.
[0093] Still further, in some embodiments the triggering of the
pre-termination period with the timing threshold may be based on
sleep state detection as well. For example, the time for
termination of treatment may not be based just on device use.
Rather, it may be based on an amount of time in a treatment session
that the patient treated with the device while the device detected
a sleep state. For example, the timing threshold might be set to an
amount of time that the patient was being treated while in a
detected REM state. This REM state based timing threshold may be
pre-set or it may be a calculated REM state time, or portion
thereof, from one or more prior treatment sessions. In such a case
it may be an average REM state time from prior sessions. Thus, the
pre-termination period may be triggered as a function of a detected
lapsed REM sleep time in a current treatment session.
[0094] Still further, the termination period may be initiated based
on a detection of wake related events, which may be in conjunction
with a timing threshold. For example, EEG signals or effort band
signals may be processed by the controller to detect that the
patient is waking up. If the signals contain an indication that the
patient is waking up and/or a timing threshold has been reached
such as one of the threshold previously discussed, the apparatus
may initiate the pre-termination period.
[0095] Still further the pre-termination period may be initiated by
a patient manually. For example, a patient may simply press a
button or other user control on the device to more immediately
activate initiation of the pre-termination period. Thus, when a
patient initially wakes up he or she may manually initiate the
pre-termination period.
Example Architecture
[0096] An example system architecture of a controller suitable for
the present technology is illustrated in the block diagram of FIG.
9. In the illustration, the controller 901 for the respiratory
pressure treatment apparatus 102 may include one or more processors
908. The device may also include a display interface 910 to output
SDB event detection reports (e.g., obstruction information and/or
measures), results or graphs (e.g., pressure vs. time curves
illustrated in FIGS. 3, 5 and 7 or flow vs. time curves, etc.) as
described herein such as on a monitor or LCD panel. A user
control/input interface 912, for example, for a keyboard, touch
panel, control buttons, mouse etc. may also be provided to activate
or modify the control parameters for the methodologies described
herein. The device may also include a sensor or data interface 914,
such as a bus, for receiving/transmitting data such as programming
instructions, rise time or pressure data, EPR level data, SDB event
detection data etc. The device may also typically include
memory/data storage components containing control instructions of
the aforementioned methodologies (e.g., FIGS. 2-6). These may
include processor control instructions for flow and/or signal
processing and/or CPAP treatment control (e.g., pre-processing
methods, filters, automated treatment pressure adjustment
methodology) at 922 as discussed in more detail herein. They may
also include processor control instructions for EPR Control and
Adjustment (e.g., obstruction detection, apnea detection, hypopnea
detection, EPR level adjustments, inspiratory rise time
adjustments, etc.) at 924. Finally, they may also include stored
data, timing thresholds, scaling factors, scaling functions, EPR
levels, tables, timing thresholds, etc.)
[0097] In some embodiments, the processor control instructions and
data for controlling the above described methodologies may be
contained in a computer readable recording medium as software for
use by a general purpose computer so that the general purpose
computer may serve as a specific purpose computer according to any
of the methodologies discussed herein upon loading the software
into the general purpose computer.
[0098] A device in accordance with the present technology is
suitable for use in the home of a patient, for example on a bedside
table. Such devices often have a volume of approximately 2 to 3 L
and are quiet enough for a patient to sleep in close proximity. A
device suitable for incorporating the present technology is the
ResMed S9 CPAP device. Commonly such devices are available only on
prescription. Depending on the healthcare system in a particular
country, patients may be entitled to a reimbursement of some or all
of the cost of the device from a government agency, or a healthcare
insurer. Devices in accordance with the present technology may be
used with a humidifier, e.g. ResMed H5i, to improve patient
comfort.
[0099] In the foregoing description and in the accompanying
drawings, specific terminology, equations and drawing symbols are
set forth to provide a thorough understanding of the present
technology. In some instances, the terminology and symbols may
imply specific details that are not required to practice the
technology. For example, although the terms "first" and "second"
have been used herein, unless otherwise specified, the language is
not intended to provide any specified order but merely to assist in
explaining distinct elements of the technology. Furthermore,
although process steps in the detection methodologies have been
illustrated in the figures in an order, such an ordering is not
required. Those skilled in the art will recognize that such
ordering may be modified and/or aspects thereof may be conducted in
parallel. Moreover, although the features described herein may be
utilized independently various combinations thereof may be made in
a respiratory pressure treatment apparatus. Other variations can be
made without departing with the spirit and scope of the technology.
For example, a controller may be configured with the control logic
to make different combinations of the automated adjustments of the
CPAP treatment pressure, the EPR level and/or the aggressiveness of
the inspiratory portion of the pressure waveform based on the
detection of SDB events or obstruction detection. For example, an
automated detection of an obstructive event may be initially
treated by increasing the aggressiveness of the inspiratory portion
of the waveform (e.g., by one increment or incrementally to its
maximum aggressiveness). If the event persists (e.g., over a time
period or lapsing of one or more respiratory cycles), the
controller may then decrease the EPR level (e.g., by one decrement
or incrementally to its lowest level). If the event still persists
(e.g., over a further time period or lapsing of one or more
additional respiratory cycles), the controller may then increase
the CPAP treatment pressure level. (e.g., by one increment or
incrementally to its maximum pressure setting). Still further
embodiments may be made with different orders and combinations of
these adjustments.
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