(12) United States Patent
`Rapoport et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 9.427,539 B2
`Aug. 30, 2016
`
`USOO9427539B2
`
`(54)
`
`(71)
`
`(72)
`
`(73)
`
`(*)
`
`(21)
`(22)
`(65)
`
`(63)
`
`SYSTEMAND METHOD FOR DIAGNOSIS
`AND TREATMENT OF A BREATHING
`PATTERN OF A PATIENT
`
`Applicant: NEW YORK UNIVERSITY, New
`York, NY (US)
`Inventors: David M. Rapoport, New York, NY
`(US); Robert G. Norman, New
`Windsor, NY (US)
`Assignee: NEW YORK UNIVERSITY, New
`York, NY (US)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`Appl. No.: 15/015.944
`
`Notice:
`
`Filed:
`
`Feb. 4, 2016
`
`Prior Publication Data
`US 2016/O151595 A1
`Jun. 2, 2016
`
`Related U.S. Application Data
`Continuation of application No. 14/633,535, filed on
`Feb. 27, 2015, which is a continuation of application
`No. 14/583,005, filed on Dec. 24, 2014, now Pat. No.
`9,108.009, which is a continuation of application No.
`(Continued)
`
`(51)
`
`Int. C.
`A6 IB5/08
`A6B 5/87
`
`(2006.01)
`(2006.01)
`(Continued)
`
`(52)
`
`U.S. C.
`CPC .......... A61M 16/0069 (2014.02); A61 B 5/087
`(2013.01); A61 B 5/0816 (2013.01); A61B
`5/4812 (2013.01); A61 B 5/4818 (2013.01);
`A61M 16/00 (2013.01); A61M 16/0003
`(2014.02); A61M 16/06 (2013.01); A61B
`
`5/021 (2013.01); A61 B 5/024 (2013.01); A61 B
`5/0205 (2013.01); A61 B 5/0476 (2013.01);
`A61 B 5/0826 (2013.01); A61 B 5/4809
`(2013.01); A61 B 5/7267 (2013.01); A61M
`16/0066 (2013.01);
`
`(Continued)
`(58) Field of Classification Search
`CPC. A61 B 5/0816: A61 B 5/0826; A61 B 5/087;
`A61 B 5/4809; A61 B 5/4812: A61 B 5/4818;
`A61 B 5/08: A61 B 5/4803; A61M 16/00;
`A61M 2016/003: A61M 2016/0039; A61M
`2016/0042: A61M 2205/3334: A61M
`2205/3344; A61M 16/0069; A61M 16/0003;
`A61M 16/06; A61M 16/0066; A61M
`2016/0021: A61M 2016/0036
`See application file for complete search history.
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
`
`5,492,113 A * 2/1996 Estes ..................... A61M 16.00
`128.204.21
`5,551,418 A * 9/1996 Estes ..................... A61M 16.00
`128.204.21
`
`(Continued)
`Primary Examiner — Navin Natnithithadha
`(74) Attorney, Agent, or Firm — Fay Kaplun & Marcin,
`LLP
`ABSTRACT
`(57)
`Described is a system including a sensor and a processing
`arrangement. The sensor measures data corresponding to a
`patient's breathing patterns. The processing arrangement
`analyzes the breathing patterns to determine whether the
`breathing patterns are indicative of a REM sleep state. In
`another embodiment, the processing arrangement analyzes
`the breathing patterns to determine whether the breathing
`patterns are indicative of one of the following states: (i) a
`wake state and (ii) a sleep state. In another embodiment, a
`neural network analyzes the data to determine whether the
`breathing patterns are indicative of one of the following
`states: (i) a REM sleep state, (ii) awake state and (iii) a sleep
`state. In another embodiment, the processing arrangement
`analyzes the data to determine whether the breathing pattern
`is indicative of an arousal.
`30 Claims, 6 Drawing Sheets
`
`
`
`25
`
`22
`
`24
`
`ResMed Inc. Exhibit 1001
`Page 1 of 14
`
`

`

`US 9.427,539 B2
`Page 2
`
`Related U.S. Application Data
`12/983,628, filed on Jan. 3, 2011, now Pat. No.
`9,168,344, which is a continuation of application No.
`11/240,197, filed on Sep. 30, 2005, now Pat. No.
`7,896,812, which is a continuation-in-part of appli
`cation No. 1 1/210,568, filed on Aug. 24, 2005, now
`Pat. No. 7,186,221, which is a continuation of appli
`cation No. 10/642,459, filed on Aug. 14, 2003, now
`Pat. No. 6,988,994.
`
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`
`(51) Int. Cl.
`A6M I6/06
`A6M 16/00
`A6 IB 5/02
`A6 IB 5/024
`A6 IB5/0476
`A61 B 5/0205
`A61 B 5/OO
`(52) U.S. Cl.
`CPC A61M2016/003 (2013.01); A61M 2016/0021
`(2013.01); A61M 2016/0027 (2013.01); A61M
`2016/0039 (2013.01); A61M 2016/0042
`(2013.01); A61M 2205/3334 (2013.01); A61M
`2205/3344 (2013.01); A61M 2230/04
`(2013.01); A61M 2.230/30 (2013.01); YIOS
`128/925 (2013.01)
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,823,187
`
`5,901,704
`
`5,904,141
`
`5,970,975
`
`6,015,388
`
`6,397,845
`
`6.427,689
`
`6,629,527
`
`6,644,312
`
`6,845,773
`
`6,889,691
`
`10, 1998
`
`5, 1999
`
`5, 1999
`
`10, 1999
`
`1, 2000
`
`6, 2002
`
`8, 2002
`
`10, 2003
`
`11/2003
`
`1/2005
`
`5/2005
`
`Estes ..................... A61M 16.00
`128.204.21
`Estes ..................... A61M 16.00
`128.204.21
`Estes ..................... A61M 16.00
`128.204.21
`Estes ..................... A61M 16.00
`128.204.18
`Sackner ................... A61B5/08
`600,529
`Burton .................. A61M 16.00
`128.204.18
`Estes ..................... A61M 16.00
`128.204.18
`Estes ..................... A61M 16.00
`128,202.22
`Berthon-Jones ...... A61M16/00
`128.204.18
`Berthon-Jones ...... A61M16/00
`128.204.18
`Eklund .................. A61 B 5,087
`128.200.24
`
`6,988.994
`
`7,013,892
`
`7,089,937
`
`7,186,221
`
`7.469,697
`
`7,770,578
`
`7,787,946
`
`7,896,812
`
`8,069,852
`
`8,333,708
`
`9,108,009
`9,168,344
`9,227,032
`2001/OO27792
`
`1, 2006
`
`3, 2006
`
`8, 2006
`
`3, 2007
`
`12, 2008
`
`8, 2010
`
`8, 2010
`
`3, 2011
`
`12, 2011
`
`12/2012
`
`8, 2015
`10, 2015
`1, 2016
`10, 2001
`
`2002.0193697
`
`12, 2002
`
`2003/0000528
`
`2004, OO16433
`
`2004/OO74497
`
`2005/OO38353
`
`2005/O113710
`
`2005/O115561
`
`2005/O133032
`
`2006, OOO9708
`
`2006/0084877
`
`2006.010217.9
`
`2006/0118112
`
`1, 2003
`
`1, 2004
`
`4, 2004
`
`2, 2005
`
`5/2005
`
`6, 2005
`
`6, 2005
`
`1, 2006
`
`4, 2006
`
`5/2006
`
`6, 2006
`
`2006/0249149
`
`11/2006
`
`2011 0166470
`
`T/2011
`
`2015,0107594
`
`2015,0165147
`
`4, 2015
`
`6, 2015
`
`* cited by examiner
`
`
`
`Rapoport ............. A61B5/0816
`128.204.18
`Estes ..................... A61M 16.00
`128.204.18
`Berthon-Jones ...... A61M 16.00
`128.204.18
`Rapoport ............. A61B5/0816
`128.204.18
`Lee ...................... A61B5/0031
`128.200.24
`Estes ..................... A61M 16.00
`128.204.18
`Stahmann ............ A61B5/0031
`6O7.3
`Rapoport ............. A61B5/0816
`128.204.23
`Burton ..................... A61B 5,04
`128.204.18
`Rapoport ............. A61B5/0816
`128.204.23
`Rapoport ............. A61B5/0816
`Rapoport ...
`... A61B 5,0816
`Kwok ...........
`A61M16/0051
`Berthon-Jones ...... A61M 16.00
`128.204.23
`Cho ..................... A61B5/0205
`600,529
`Eklund .................. A61B 5,087
`128.204.23
`Estes ..................... A61M 16.00
`128.204.21
`Berthon-Jones ...... A61M 16.00
`128.204.23
`Rapoport ............. A61B5/0816
`600,532
`Stahmann ......... A61M16/0051
`600,534
`Stahmann ............ A61B5/0031
`128.200.24
`Berthon-Jones ...... A61M 16.00
`128.204.23
`Rapoport ............. A61B5/0816
`600,538
`Ujihazy ............. A61M16/0051
`600,483
`Rapoport ............. A61B5/0816
`128.204.23
`Cattano ................. A61M 16.00
`128.204.21
`Meier .................... A61B 5,087
`128.204.18
`Rapoport ............. A61B5/0816
`600,534
`Rapoport ............. A61B5/0816
`128.204.23
`Rapoport ............. A61B5/0816
`128.204.23
`
`ResMed Inc. Exhibit 1001
`Page 2 of 14
`
`

`

`U.S. Patent
`
`Aug. 30, 2016
`
`Sheet 1 of 6
`
`US 9,427,539 B2
`
`
`
`F G. 1
`
`ResMed Inc. Exhibit 1001
`Page 3 of 14
`
`

`

`U.S. Patent
`
`Aug. 30, 2016
`
`Sheet 2 of 6
`
`US 9,427,539 B2
`
`
`
`
`
`O
`
`Initiating System
`
`2O2
`
`Performing Monitoring Procedure
`
`2O4
`
`Has There Been Change
`in Patient's State?
`
`
`
`YES
`
`Pressure Provided to Patient is Adjusted
`
`208
`
`
`
`21 O
`
`
`
`NO
`
`Disengage System?
`
`YES
`
`End
`
`F G. 2
`
`ResMed Inc. Exhibit 1001
`Page 4 of 14
`
`

`

`U.S. Patent
`
`Aug. 30, 2016
`
`Sheet 3 of 6
`
`US 9.427,539 B2
`
`F G. 3
`
`F G. 4
`
`F G. 6
`
`PVVV///VVVVV-VVVVV
`vvvvvvvvvvvvvvvv
`UVVvvvu- ~~~\\
`M-MA-HVW
`AJJ a??ulu-VJJuv
`YYYY-viv-wv-v-yv-vi
`
`F G. 5
`
`F G. 7
`
`F G. 8
`
`ResMed Inc. Exhibit 1001
`Page 5 of 14
`
`

`

`U.S. Patent
`
`Aug. 30, 2016
`
`Sheet 4 of 6
`
`US 9,427,539 B2
`
`1 100 O
`
`
`
`
`
`
`
`
`
`
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`
`
`
`
`
`
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`
`
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`
`
`2 O
`
`
`
`initialize
`System
`
`102
`
`/
`
`104
`
`Obtain data from
`Sensors regarding
`breathing pattern
`
`Initialize
`System
`
`252
`
`254
`
`identity state of patient
`(asleep/awake)
`
`106
`
`256
`
`
`
`s
`breathing pattern
`indicative of
`REM sleep
`state?
`
`
`
`Report REM sleep
`State
`
`
`
`F G. 10
`
`F G. 9
`
`ResMed Inc. Exhibit 1001
`Page 6 of 14
`
`

`

`U.S. Patent
`
`Aug. 30, 2016
`
`Sheet S of 6
`
`US 9,427,539 B2
`
`
`
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`302
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`304
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`306
`
`Construct neural
`network
`
`Train neural
`network
`
`Test neural
`network
`
`Performance
`of neural network
`satisfactory?
`
`Detect patient's state
`using neural network
`
`31 O
`
`F G. 11
`
`ResMed Inc. Exhibit 1001
`Page 7 of 14
`
`

`

`U.S. Patent
`
`Aug. 30, 2016
`
`Sheet 6 of 6
`
`US 9,427,539 B2
`
`
`
`
`
`
`
`
`
`Supply pressure
`at default level
`
`4O2
`
`is
`breathing pattern
`Sleep digg
`State
`
`increase
`yes pressure toward
`first
`predetermined
`pressure
`
`
`
`
`
`
`
`
`
`Decrease
`pressure toward yes
`Second
`predetermined
`pressure
`
`s
`breathing pattern
`troubled
`Wakefulness
`State?
`
`F G. 12
`
`ResMed Inc. Exhibit 1001
`Page 8 of 14
`
`

`

`US 9,427,539 B2
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`10
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`30
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`35
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`50
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`2
`PAP therapy has become the mainstay of treatment in
`Obstructive Sleep Disordered Breathing (OSDB), which
`includes Obstructive Sleep Apnea, Upper Airway Resistance
`Syndrome, Snoring, exaggerations of sleep induced
`increases in the collapsibility of the upper airway and all
`conditions in which inappropriate collapsing of a segment of
`the upper airway causes significant un-physiologic obstruc
`tion to airflow. This collapse generally occurs whenever
`pressure in the collapsible portion of the airway decreases
`below a level defined as a “critical tissue pressure' in the
`surrounding wall. The PAP therapy is directed to maintain
`ing pressure in the collapsible portion of the airway at or
`above the critical tissue pressure at all times. In the past, this
`goal has been achieved by raising a pressure delivered to the
`patient’s airway to a level higher than this critical tissue
`pressure at all times when the patient is wearing the device.
`In general, the need for the PAP therapy occurs only
`during sleep. However, the conventional PAP therapy has
`not taken sleep/wake state into account, and conventional
`PAP systems apply pressure unnecessarily when the patient
`is awake. The applied pressure is either a constant pressure,
`or a pressure based on breath-by-breath determination of the
`need for treatment. Various strategies for determining the
`minimal pressure have evolved based on recognizing patho
`logical events (e.g., apnea, hypopnea and other evidence of
`high airway resistance) as determined by feedback from a
`variety of signals that indicate the need for the PAP therapy
`due to the airway collapse.
`Despite its success, limitations on the use of the conven
`tional PAP systems still exist based on, for example, dis
`comfort from the mask and the pressure required to oblit
`erate the apneas. In particular, patients often report
`discomfort due to high pressure while being awake. To avoid
`this discomfort, the applied pressure should be provided
`only when the patient is asleep. For example, a "ramp”
`system utilizes a patient activated delay in the onset of the
`applied pressure, but the ramp system is not automatically
`responsive to patient awakenings during the night, unless
`deliberately activated by the patient pushing a button.
`Patient’s discomfort during wakefulness is often associ
`ated with changes from a regular breathing pattern (e.g., near
`constant breath size and frequency) to one which contains
`irregularities. These irregular patterns (e.g., including iso
`lated big breaths, short pauses, and changes in breath flow
`shape that do not vary in any regular pattern) are recognized
`by inspection of the airflow tracing alone, and frequently
`occur when the patient is distressed by the PAP system.
`Some conventional PAP systems utilize algorithms which
`continuously and automatically titrate the applied pressure.
`These algorithms depend on detecting evidence of airway
`collapse from the breathing signals. However, these algo
`rithms of the conventional PAP systems have certain limi
`tations. For example, the irregular pattern of breathing
`present while a Subject is awake, and more so when anxious,
`interferes with the processing of the breath signal that
`calculates the applied pressure.
`
`1.
`SYSTEMAND METHOD FOR DIAGNOSIS
`AND TREATMENT OF A BREATHING
`PATTERN OF A PATIENT
`
`PRIORITY CLAIM
`
`This application is a continuation application of U.S.
`patent application Ser. No. 14/633,535 filed on Feb. 27,
`2015; which is continuation application of U.S. patent
`application Ser. No. 14/583,005 filed on Dec. 24, 2014, now
`U.S. Pat. No. 9,108,009; which is a continuation application
`of U.S. patent application Ser. No. 12/983,628 filed on Jan.
`3, 2011, now U.S. Pat. No. 9,168,344, which is a continu
`ation application of U.S. patent application Ser. No. 1 1/240,
`197 filed on Sep. 30, 2005, now U.S. Pat. No. 7,896,812;
`which is a continuation-in-part application of U.S. patent
`application Ser. No. 1 1/210,568 filed on Aug. 24, 2005, now
`U.S. Pat. No. 7,186.221; which is a continuation application
`of and U.S. patent application Ser. No. 10/642.459 filed on
`Aug. 14, 2003, now U.S. Pat. No. 6,988.994. The entire
`disclosure of these prior applications/patents are considered
`as being part of the disclosure of the accompanying appli
`cation and hereby expressly incorporated by reference
`herein.
`
`BACKGROUND
`
`Obstructive sleep apnea syndrome (OSAS) is a well
`recognized disorder which may affect as much as 1-5% of
`the adult population. OSAS is one of the most common
`causes of excessive daytime somnolence. OSAS is most
`frequent in obese males, and it is the single most frequent
`reason for referral to sleep disorder clinics.
`OSAS is associated with many conditions in which there
`is an anatomic or functional narrowing of the patient's upper
`airway, and is characterized by an intermittent obstruction of
`the upper airway occurring during sleep. The obstruction
`results in a spectrum of respiratory disturbances ranging
`from the total absence of airflow (apnea) to significant
`obstruction with or without reduced airflow (hypopnea and
`Snoring), despite continued respiratory efforts. The morbid
`ity of the syndrome arises from hypoxemia, hypercapnia,
`bradycardia and sleep disruption associated with the apneas
`and Subsequent arousals from sleep.
`The pathophysiology of OSAS has not yet been fully
`worked out. However, it is well recognized that obstruction
`of the upper airway during sleep is in part due to the
`collapsible behavior of the supraglottic segment of the
`airway resulting from negative intraluminal pressure gener
`ated by inspiratory effort. Thus, in patients suffering from
`OSAS, the upper airway during sleep behaves substantially
`as a Starling resistor (i.e., the airflow is limited to a fixed
`value irrespective of the driving (inspiratory) pressure).
`Partial or complete airway collapse may then occur with the
`loss of airway tone which is characteristic of the onset of
`sleep and which may be exaggerated in OSAS.
`Since 1981, positive airway pressure (PAP) therapy
`applied by a tight fitting nasal mask worn during sleep has
`evolved as the most effective treatment for OSAS, and is
`now the standard of care. The availability of this non
`invasive form of therapy has resulted in extensive publicity
`for OSAS and the appearance of large numbers of patients
`who previously may have avoided the medical establishment
`because of the fear of tracheostomy. Increasing the comfort
`of the PAP system has been a major goal of research aimed
`at improving patient compliance with the PAP therapy.
`
`SUMMARY OF THE INVENTION
`
`60
`
`65
`
`In one exemplary embodiment, the present invention
`relates to a system including a sensor and a processing
`arrangement. The sensor measures data corresponding to a
`patient's breathing patterns. The processing arrangement
`analyzes the breathing patterns to determine whether the
`breathing patterns are indicative of a REM sleep state.
`In another embodiment, the present invention relates to a
`System comprising a sensor and a processing arrangement.
`
`ResMed Inc. Exhibit 1001
`Page 9 of 14
`
`

`

`3
`The sensor measuring data corresponding to the patients
`breathing patterns. The processing arrangement analyzes the
`breathing patterns to determine whether the breathing pat
`terns are indicative of one of the following states: (i) awake
`state and (ii) a sleep state.
`In a further embodiment, the present invention relates to
`a system comprising a sensor and a neural network. The
`sensor measuring data corresponding to the patient's breath
`ing patterns. The neural network analyzes the data to deter
`mine whether the breathing patterns are indicative of one of
`the following states: (i) a REM sleep state, (ii) a wake state
`and (iii) a sleep state.
`In yet another embodiment, the present invention relates
`to a system comprising a sensor and a processing arrange
`ment. The sensor measuring data corresponding to the
`patient’s breathing patterns. The processing arrangement
`analyzes the data to determine whether the breathing pattern
`is indicative of an arousal.
`
`5
`
`10
`
`15
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 shows an exemplary embodiment of a system
`according to the present invention;
`FIG. 2 shows an exemplary embodiment of a method
`according to the present invention which utilizes the system
`shown in FIG. 1;
`FIG. 3 shows a waveform of airflow during regular
`wakefulness of a patient (e.g., not anxious) who utilizes the
`system according to the present invention;
`FIG. 4 shows a waveform of airflow during regular sleep
`in a patient;
`FIG. 5 shows a waveform of airflow from a sleeping
`patient which is indicative of an elevated upper airway
`pressure resistance and hypopnea;
`FIG. 6 shows a waveform of airflow from a sleeping
`patient which is indicative of a repetitive obstructive apnea;
`FIG. 7 shows a waveform of airflow from a patient which
`is indicative of a period of troubled wakefulness;
`FIG. 8 shows a waveform of airflow from a patient which
`is indicative of a period of REM sleep with irregular
`breathing due to phasic REM in a patient;
`FIG. 9 shows a method for identifying a REM sleep state;
`FIG. 10 shows a method identifying a sleep and a wake
`states of a patient;
`FIG. 11 shows a method for training and utilizing a neural
`network for identifying the patient's state; and
`FIG. 12 shows a method for controlling a pressure Sup
`plied to a patient.
`
`25
`
`30
`
`35
`
`40
`
`45
`
`DETAILED DESCRIPTION
`
`FIG. 1 shows an exemplary embodiment of a system 1
`according to the present invention. The system 1 may
`include a mask 20 which is connected via a tube 21 to
`receive airflow having a particular pressure from a flow
`generator 22. The amount of pressure provided to a particu
`lar patient varies depending on patient’s particular condi
`tion. Such amount of pressure may be determined utilizing
`any conventional PAP therapy methods.
`The mask 20 covers the patient’s nose and/or mouth.
`Conventional flow sensors 23 are coupled to the tube 21. The
`sensors 23 detect the rate of airflow to/from patent and/or a
`pressure Supplied to the patent by the generator 22. The
`sensors 23 may be internal or external to the generator 22.
`Signals corresponding to the airflow and/or the pressure are
`provided to a processing arrangement 24 for processing. The
`processing arrangement 24 outputs a signal to a conven
`
`50
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`55
`
`60
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`65
`
`US 9,427,539 B2
`
`4
`tional flow control device 25 to control a pressure applied to
`the flow tube 21 by the flow generator 22. Those skilled in
`the art will understand that, for certain types of flow gen
`erators which may by employed as the flow generator 22, the
`processing arrangement 24 may directly control the flow
`generator 22, instead of controlling airflow therefrom by
`manipulating the separate flow control device 25.
`The system 1 may also include a continuous leak port or
`other venting arrangement 28. The venting arrangement 28
`allows for gases contained in the exhaled airflow of the
`patient to be diverted from the incoming airflow to prevent
`re-breathing of the exhaled gases.
`FIG. 2 shows an exemplary embodiment of a method
`according to the present invention. In step 202, the patient
`initiates the system 1 by placing the mask 20 over his face
`and powering up the generator 22, the flow control device 25
`and the processing arrangement 24.
`In step 204, the system 1 initiates a real-time monitoring
`procedure of the patient's breathing patterns. The monitor
`ing procedure is performed by the processing arrangement
`24 which may utilize pre-stored patient data along with
`current data provided by the sensors 23 regarding the airflow
`to and from the patient and/or the applied pressure.
`During the monitoring procedure, the processing arrange
`ment 24 makes a determination as to a current state of the
`patient (e.g., whether the patient is asleep, awake and
`breathing regularly or awake and breathing irregularly due
`to distress or anxiousness). Such determination can be made
`based on a number of different measurements. For example,
`the processing arrangement 24 may analyze the patients
`heart rate, blood pressure, EEG data, breathing patterns, etc.
`in the determining the patient’s state.
`There are a number of characteristics of the patients
`breathing patterns that may be taken into account in making
`such a determination. FIGS. 3 and 4 show breathing patterns
`indicative of quiet, regular and relaxed breathing in a patient
`during the PAP therapy. FIG. 3 is indicative of relaxed
`wakefulness (patient is not anxious or distressed). FIG. 4
`shows a period of relaxed breathing during sleep during
`which the patient is correctly treated with the PAP therapy.
`In either case the applied pressure can be delivered without
`impairing comfort. In addition, there are periods of sleep
`disordered breathing during which the PAP therapy must be
`applied. Indices of sleep disordered breathing include apnea
`(e.g., periods of Zero airflow which are greater than 8-10
`seconds alternating with large breaths), hypopnea (e.g.,
`cyclical periods of airflow which is substantially reduced,
`lasting 10 or more seconds, and terminated by larger
`breaths), or periods of intermittent and cyclical change in the
`shape of the signal (e.g., characterized by flattening of the
`waveform, terminated by normal shaped breaths).
`In contrast, the following exemplary characteristics may
`Suggest that the patient is awake and anxious or distressed:
`pure mouth breathing (e.g., no signal from the sensors 23
`which is configured to detect the patient’s airflow from the
`nose); erratic large breaths with varying inspiratory times;
`irregularity of intervals between breaths (but not cyclic
`apneas which indicate sleep and the need for higher pres
`sure, etc). FIG. 7 shows a period of such troubled wakeful
`ness in which the breathing pattern is characterized by
`irregularly variations in the size and/or frequency of breaths
`and/or irregular variation in the shapes of the patients
`airflow tracing indicating that the patient is awake and either
`anxious or uncomfortable. There is, however, no cyclical
`change (e.g., a periodic irregularity) in breath size. Such as
`would be seen during apnea and hypopnea sleep events. One
`of the ways to increase the patient’s comfort is to reduce the
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`applied pressure when it is not needed. Patients with
`obstructive sleep apnea do not require any pressure at all
`while awake. Thus, lowering the pressure applied to the
`mask during Such periods of irregular breathing should
`improve the patient’s comfort until the patient falls asleep
`(e.g., which may be marked by the resumption of regularity
`or cyclical but regular periods of obstruction easily recog
`nized as apnea and hypopnea or elevated upper airway
`resistance).
`The above-described breathing patterns are distinguish
`able from the slow modulation in breath size and inspiratory
`timing seen, e.g., in Cheyne Stoke and other forms of
`obstructive apnea. FIG. 5 shows a breathing pattern of a
`patient on the PAP therapy which includes an event of
`elevated upper airway resistance and hypopnea during sleep
`and FIG. 6 show a breathing pattern corresponding to a
`repetitive obstructive apnea. In both cases, the changes in
`breath size and frequency are slowly modulated and repeti
`tive and cyclical (e.g., regularly irregular). In these periods,
`the applied pressure is either needed or must be raised, but
`there is no indication it is contributing to patient distress.
`Thus, the applied pressure should not be lowered.
`FIG. 8 shows a period of REM sleep. In this phase of
`sleep, which occurs, e.g., for 10-30 minutes every 90 min
`utes of normal sleep, a breathing pattern is often character
`ized by irregular breathing. This pattern represents a poten
`tial exception to the use of irregularity to indicate
`wakefulness with anxiety. However, during this type of
`breathing, the patient is asleep and the applied pressure must
`be maintained (i.e., not reduced as during wakefulness). The
`type of irregularity seen during REM differs from that seen
`in wakefulness in several key parameters. This REM asso
`ciated pattern of breathing may include, e.g., the absence of
`larger breaths, especially after pauses, generally high respi
`ratory rates and low flow rates, and a tendency for clustering
`of small breaths. These differences in the pattern of the
`respiratory airflow signal from those seen during troubled
`wakefulness allow the separation of these states and can be
`used to make a change in the applied pressure.
`The processing arrangement 24 also collects and records
`data for each patient. Such data may be collected and entered
`manually by a technician or automatically by the processing
`arrangement 24 itself. For example, the technician may
`monitor the patient's breathing and simultaneously deter
`mine whether the patient is awake. Then, when the patient
`falls asleep, the technician may mark the breathing patterns
`of this sleeping patient so that the processing arrangement
`24 may utilize this data in future determinations as to
`whether or not the patient is awake. When a database of the
`patient’s breathing characteristics has been built, determi
`nations as to the patients wakefulness may be made sig
`nificantly more accurate.
`In step 206, the processing arrangement 24 determines
`whether there has been a change in the patient’s state. For
`example, the processing arrangement 24 may determine
`whether the patient was asleep and has been awakened; or
`the patient was awake and has fallen asleep. If there has been
`no change, the processing arrangement 24 continues with
`the monitoring procedure.
`If there has been a change in the patient's state, the
`processing arrangement 24 adjusts the pressure to corre
`spond to the patient’s current state (step 208). For example,
`if the patient has been awakened and the patient’s breathing
`patterns indicate a period of troubled wakefulness as shown
`in FIG. 7, the processing arrangement 24 may reduce the
`applied pressure provided to the patient during such period.
`This reduction may be a complete elimination of the applied
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`pressure (i.e., the flow generator 22 reduces the flow rate to
`a level which does not provide any net pressure to the patient
`in the mask, while maintaining only the minimum sufficient
`flow through the circuit to the venting arrangement 28 to
`prevent CO2 buildup), or a partial reduction (i.e., the flow
`generator 22 produces only the flow Sufficient to maintain a
`reduced portion of the air pressure that it generates while the
`patient is asleep).
`On the other hand, if the patient has fallen asleep, the
`processing arrangement 24 may instruct the flow control
`device 25 to elevate the pressure to the level to be applied
`while the patient is asleep. For example, this may be
`indicated where the patient’s breathing patterns changed
`from the pattern shown in FIG. 7 to the pattern shown in
`FIG. 4. In Such a case, the processing arrangement 24 should
`increase the pressure. From that time on, this increased
`pressure should not be reduced unless one of a plurality of
`predetermined breathing patterns is detected. For example,
`the processing arrangement 24 should at least maintain the
`same pressure or, preferably, increase the pressure if the
`patient's breathing pattern indicates an event of elevated
`upper airway resistance and hypopnea as shown in FIG. 5.
`Also, the pressure should be at least maintained at the same
`value, or, preferably, increased, if the patient’s breathing
`pattern indicates a repetitive obstructive apnea as shown in
`FIG. 6, or if the patient shows irregular breathing which
`Suggests he is in REM sleep, as during this type of breathing
`the patient is asleep and the applied pressure must be
`maintained at the same level as during other periods of sleep
`(i.e., not reduced as during wakefulness).
`In step 210, the processing arrangement 24 determines
`whether instructions to disengage the system 1 have been
`given. If Such instructions have been given (e.g., if the
`patient has pressed a designated button or a preset time
`limitation has expired), the system 1 shuts down and ends all
`monitoring and flow generating activities. Otherwise, the
`system 1 continues with the monitoring procedure of step
`204.
`One of the advantages of the system 1 according to the
`present invention is that the pressure Supplied to the patient
`is adjusted (e.g., reduced to Zero or a preset low level) when
`the patient has an irregular breathing pattern that suggests
`that he is awake and anxious. When breathing is either
`regular (e.g., Suggesting sleep) or shows sleep disorder
`breathing events, the pressure may be maintained or
`increased.
`In another embodiment of the present invention, the
`system 1 may be utilized for one or more diagnostic appli
`cations. That is, the processing arrangement 24 may obtain
`data from the sensors 23 regarding the breathing patterns of
`the patient and record the patient's state without Supplying
`the pressure thereto. For example, the present invention may
`include a method 100 as shown in FIG. 9 for determining
`when the patient is in the REM sleep state. In step 102, the
`system 1 is initialized and the mask 20 is coupled to the
`patient. In step 104, the sensors 23 obtain data indicative of
`the patient’s breathing patterns.
`In step 106, the processing arrangement 24 determines
`whether the breathing pattern is identifiable as the REM
`sleep state. For example, when the breathing pattern
`includes the absence of large breaths (e.g., after pauses in
`breathing), a high respiratory rate and a low flow rate and/or
`a tendency for clustering of Small breaths, the processing
`arrangement 24 may identify the breathing pattern as the
`REM sleep state. When the breathing pattern is not identified
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`as the REM sleep state, the processing arrangement 24 may
`continue to gather data regarding the patient’s breathing
`patterns.
`In step 108, the processing arrangement 24 has identified
`the breathing pattern as the REM sleep state and reports such
`to a user (e.g., a physician) of the system 1. Additionally or
`alternatively, the processing arrangement 24 may flag a
`portion of an internal log to note that the patient was in the
`REM sleep state for a predefined time. That is, after the
`REM sleep state has been identified, the processing arrange
`ment 24 may continue identifying the breathing patterns of
`the patient to determine a termination of the REM sleep
`State.
`In a further embodiment of the present invention, the
`system 1 may be utilized to detect when the patient is
`asleep/awake and adjust pressure based thereon. A method
`250 according to this embodiment is shown in FIG. 10. In
`step 252, the system 1 is initialized and coupled to the
`patient. In step 254, the processing arrangement 24 deter
`mines a first state of the patient based on data obtained from
`the sensors 23 regarding the breathing pattern of the patient.
`In this embodiment, the processing arrangement 24 may
`determine whether the patient is in a sleep state or a wake
`state based on the breathing pattern. That is, the data may be
`indicative of a regular breathing state which is generally
`identified with the sleep state or the wake state.
`In another e