(12) United States Patent
`Rapoport et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 9,168,344 B2
`*Oct. 27, 2015
`
`USOO916834.4B2
`
`(75)
`
`(73)
`
`Assignee:
`
`(*)
`
`Notice:
`
`(54) SYSTEMAND METHOD FOR DIAGNOSIS
`AND TREATMENT OF A BREATHING
`PATTERN OF A PATIENT
`Inventors: David M. Rapoport, New York, NY
`(US); Robert G. Norman, New
`Windsor, NY (US)
`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 174 days.
`This patent is Subject to a terminal dis
`claimer.
`Appl. No.: 12/983,628
`Filed:
`Jan. 3, 2011
`Prior Publication Data
`US 2011 FO16647OA1
`Jul. 7, 2011
`Related U.S. Application Data
`Continuation of application No. 1 1/240,197, filed on
`Sep. 30, 2005, now Pat. No. 7,896,812, which is a
`continuation-in-part of application No. 1 1/210,568,
`filed on Aug. 24, 2005, now Pat. No. 7,186.221, which
`is a continuation of application No. 10/642.459, filed
`on Aug. 14, 2003, now Pat. No. 6,988.994.
`Int. C.
`A6IB5/087
`A6M 16/06
`
`(21)
`(22)
`(65)
`
`(63)
`
`(51)
`
`(2006.01)
`(2006.01)
`(Continued)
`
`(52)
`
`(58)
`
`U.S. C.
`CPC ............ A61M 16/0069 (2014.02); A61B5/087
`(2013.01); A61B5/0816 (2013.01);
`(Continued)
`Field of Classification Search
`CPC ...... A61B 5/0205; A61 B 5/021: A61B 5/024;
`A61B5/0476; A61B5/0816: A61B5/087;
`A61 B 5/4809; A61 B 5/4812: A61 B 5/4818;
`A61 B 5/7267: A61M 16/00; A61M 16/0066:
`A61M 16/06; A61M 2016/0021: A61M
`2016/OO39
`
`
`
`USPC ......................... 600/484,529-543, 300, 301;
`128/920–925, 204.26, 204.21, 204.22,
`128/204.23
`See application file for complete search history.
`References Cited
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`(56)
`
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`
`5,101,831 A *
`5,485,851 A *
`
`4/1992 Koyama et al. ............... 600,500
`1/1996 Erickson ....................... 600,529
`(Continued)
`
`FOREIGN PATENT DOCUMENTS
`
`JP
`WO
`
`11, 2004
`2004-533270
`8, 1997
`97.28838
`(Continued)
`OTHER PUBLICATIONS
`
`Massie et al., “Comparison between Automatic and Fixed Positive
`Airway Pressure Therapy in the Home'. American Journal of Respi
`ratory and Critical Care Medicine, 2003, vol. 167. No. 1, pp. 20-23.
`(Continued)
`Primary Examiner — Navin Natnithithadha
`(74) Attorney, Agent, or Firm — Fay Kaplun & Marcin, LLP
`(57)
`ABSTRACT
`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) a wake 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.
`
`16 Claims, 6 Drawing Sheets
`
`ResMed Inc. Exhibit 1001
`Page 1 of 13
`
`

`

`US 9,168,344 B2
`Page 2
`
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`
`(51) Int. Cl.
`A6M ls00
`A61B5/08
`A61 B 5/0205
`A61 B 5/021
`A61 B 5/024
`A61B5/0476
`A61B5/OO
`(52) U.S. Cl.
`CPC ............. A61B5/4812 (2013.01); A61B5/4818
`(2013.01); A61M 16/00 (2013.01); A61M
`16/0003 (2014.02); A61M 16/06 (2013.01);
`A61 B 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); A61B
`5/4809 (2013.01); A61 B 5/7267 (2013.01);
`A61M 16/0066 (2013.01); A61M 2016/003
`(2013.01); A61M 2016/0021 (2013.01); A61M
`2016/0039 (2013.01); A61M 2016/0042
`(2013.01); A61M 2205/3334 (2013.01); A61M
`2205/3344 (2013.01); A61M 2.230/04
`(2013.01); A61M 2.230/30 (2013.01); YIOS
`128/925 (2013.01)
`
`(56)
`
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`6,605,038 B1* 8/2003 Teller et al. ................... 600/300
`6,629,527 B1 * 10/2003 Estes et al. ..
`... 128,204.18
`6,805,668 B1 * 10/2004 Cadwell ........................ 600/300
`6,889,691 B2* 5/2005 Eklund et al. ......
`... 128,204.21
`6,988.994 B2 *
`1/2006 Rapoport et al. ............. 600,538
`7,013,892 B2 * 3/2006 Estes et al. .....
`... 128,204.18
`7,041,049 B1* 5/2006 Raniere ........................... 600, 26
`7,150,718 B2 * 12/2006 Okada et al. .......
`... 600,538
`7,186.221 B2 * 3/2007 Rapoport et al. ............. 600/538
`7,189,204 B2 * 3/2007 Ni et al. ........................ 600/300
`7,204.250 B1 * 4/2007 Burton ........
`... 128.205.23
`7,207,947 B2 * 4/2007 Koh et al. ..................... 600,529
`7,662,101 B2 * 2/2010 Lee et al. .......
`... 600,484
`7,717.848 B2 * 5/2010 Heruth et al. ................. 600/300
`7,770,578 B2* 8/2010 Estes et al. ...
`... 128,204.18
`7,775,993 B2 * 8/2010 Heruth et al. ................. 600,587
`7,896,812 B2 * 3/2011 Rapoport et al. ......
`... 600,529
`8,002,553 B2 * 8/2011 Hatlestad et al. ............. 434,262
`8,069,852 B2 * 12/2011 Burton et al. ......
`... 128,204.18
`8, 192,376 B2 * 6/2012 Lovett et al. .................. 600,595
`8,281,787 B2 * 10/2012 Burton ...............
`... 128,204.23
`8.333,708 B2 * 12/2012 Rapoport et al. ............. 600,529
`2002fOO29000 A1* 3, 2002 Ohsaki et al. ......
`... 600,500
`2005/0038353 A1* 2/2005 Rapoport et al. ............. 600,532
`2005, 0080349 A1
`4/2005 Okada et al.
`2006/0009708 A1* 1/2006 Rapoport et al. ............. 600,538
`2006/0102179 A1* 5/2006 Rapoport et al. ........ 128.204.23
`2007/0032733 A1
`2/2007 Burton .......................... 600/509
`2007/0055.168 A1* 3/2007 Rapoport et al. ............. 600,529
`
`
`
`U.S. PATENT DOCUMENTS
`
`FOREIGN PATENT DOCUMENTS
`
`5.492,113 A *
`5,551418 A *
`5,657,752 A
`5,823, 187 A
`5,901,704 A
`5,904,141 A
`5,970,975 A
`6, 190,328 B1*
`6,397,845 B1*
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`
`2, 1996
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`6, 2002
`
`Estes et al. ............... 128.204.23
`Estes et al. ............... 128.204.23
`Landis et al.
`Estes et al. ............... 128.204.23
`Estes et al. ...
`... 128.204.23
`Estes et al. ...
`... 128.204.23
`Estes et al. ...
`... 128.204.23
`Ruton et al. .................. 600,532
`Burton .............
`128.204.23
`Ruton et al. .................. 600,532
`
`WO
`WO
`
`4/2004
`2002/028281
`3, 2005
`2005/O18416
`OTHER PUBLICATIONS
`
`ZoZula et al., “Compliance with Continuous positive airway pres
`Sure therapy: assessing and improving treatment outcomes. Current
`Opinion in Pulmonary Medicine, 2001, vol.7. Issue 6, pp.391-398.
`
`* cited by examiner
`
`ResMed Inc. Exhibit 1001
`Page 2 of 13
`
`

`

`U.S. Patent
`
`Oct. 27, 2015
`
`Sheet 1 of 6
`
`US 9,168,344 B2
`
`
`
`F G. 1
`
`ResMed Inc. Exhibit 1001
`Page 3 of 13
`
`

`

`U.S. Patent
`
`Oct. 27, 2015
`
`Sheet 2 of 6
`
`US 9,168,344 B2
`
`
`
`
`
`
`
`
`
`Initiating System
`
`202
`
`Performing Monitoring Procedure
`
`204
`
`Has There Been Change
`in Patient's State?
`
`Pressure Provided to Patient is Adjusted
`
`208
`
`210
`
`Disengage System?
`
`
`
`F G. 2
`
`ResMed Inc. Exhibit 1001
`Page 4 of 13
`
`

`

`U.S. Patent
`
`Oct. 27, 2015
`
`Sheet 3 of 6
`
`US 9,168,344 B2
`
`F G. 3
`
`PVVVVA/VVVV-V-I/VVV
`vvvvvvvvvvvvvvvv
`UVVvvv-v-V.
`M-MAH-WW
`
`F G. 5
`
`F G. 6
`
`F. G. 4
`
`(Vyvi-viv-wv-viv-vi
`
`F G. 7
`
`F G. 8
`
`ResMed Inc. Exhibit 1001
`Page 5 of 13
`
`

`

`U.S. Patent
`
`Oct. 27, 2015
`
`Sheet 4 of 6
`
`US 9,168,344 B2
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Initialize
`system
`
`102
`
`104
`
`Obtain data from
`sensors regarding
`breathing pattern
`
`Initialize
`system
`
`252
`
`254
`
`Identity state of patient
`(asleep/awake)
`
`106
`
`256
`
`Adjust pressure
`
`F G. 10
`
`
`
`ls
`breathing pattern
`indicative of
`REM sleep
`state?
`
`YES
`Report REM sleep
`State
`
`
`
`F G. 9
`
`ResMed Inc. Exhibit 1001
`Page 6 of 13
`
`

`

`U.S. Patent
`
`Oct. 27, 2015
`
`Sheet 5 of 6
`
`US 9,168,344 B2
`
`
`
`
`
`
`
`
`
`Construct neural
`network
`
`Train neural
`network
`
`Test neural
`network
`
`304
`
`306
`
`
`
`
`
`Performance
`of neural network
`satisfactory?
`
`
`
`Detect patient's state
`using neural network
`
`310
`
`F G 11
`
`ResMed Inc. Exhibit 1001
`Page 7 of 13
`
`

`

`U.S. Patent
`
`Oct. 27, 2015
`
`Sheet 6 of 6
`
`US 9,168,344 B2
`
`Supply pressure
`at default level
`
`
`
`402
`
`
`
`S
`breathing pattern
`sleep disorder
`state
`
`Increase
`ressure toward
`YES P
`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 13
`
`

`

`US 9, 168,344 B2
`
`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. 1 1/240,197 filed on Sep. 30, 2005
`entitled “System and Method for Diagnosis and Treatment of
`a Breathing Pattern of a Patient' which is a Continuation-in
`Part 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 of 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 con
`sidered as being part of the disclosure of the accompanying
`application and hereby expressly incorporated by reference
`herein.
`
`10
`
`15
`
`BACKGROUND
`
`25
`
`30
`
`35
`
`Obstructive sleep apnea syndrome (OSAS) is a well rec
`ognized 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 morbidity of the
`syndrome arises from hypoxemia, hypercapnia, bradycardia
`and sleep disruption associated with the apneas and Subse
`quent arousals from sleep.
`The pathophysiology of OSAS has not yet been fully
`worked out. However, it is well recognized that obstruction of
`40
`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 generated by inspiratory
`effort. Thus, in patients suffering from OSAS, the upper
`airway during sleep behaves Substantially as a Starling resis
`45
`tor (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 exag
`gerated 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 sys
`tem has been a major goal of research aimed at improving
`patient compliance with the PAP therapy.
`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 obstruction to air
`
`50
`
`55
`
`60
`
`65
`
`2
`flow. 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 maintaining 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 treat
`ment. Various strategies for determining the minimal pressure
`have evolved based on recognizing pathological events (e.g.,
`apnea, hypopnea and other evidence of high airway resistan
`ce)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, discom
`fort from the mask and the pressure required to obliterate 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 awak
`enings 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 limita
`tions. For example, the irregular pattern of breathing present
`while a subject is awake, and more so when anxious, inter
`feres with the processing of the breath signal that calculates
`the applied pressure.
`
`SUMMARY OF THE INVENTION
`
`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.
`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) a wake
`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
`
`ResMed Inc. Exhibit 1001
`Page 9 of 13
`
`

`

`US 9, 168,344 B2
`
`3
`measuring data corresponding to the patient's breathing pat
`terns. The 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) 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 arrangement.
`The sensor measuring data corresponding to the patients
`breathing patterns. The processing arrangement analyzes the
`data to determine whether the breathing pattern is indicative
`of an arousal.
`
`4
`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-breath
`ing 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 monitoring
`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 breath
`ing regularly or awake and breathing irregularly due to dis
`tress or anxiousness). Such determination can be made based
`on a number of different measurements. For example, the
`processing arrangement 24 may analyze the patient's 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 wake
`fulness (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 com
`fort. In addition, there are periods of sleep disordered breath
`ing 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 air
`flow which is substantially reduced, lasting 10 or more sec
`onds, and terminated by larger breaths), or periods of inter
`mittent 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 pressure,
`etc). FIG. 7 shows a period of such troubled wakefulness 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 patient’s airflow trac
`ing 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 applied pres
`sure 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 patients comfort
`until the patient falls asleep (e.g., which may be marked by the
`resumption of regularity or cyclical but regular periods of
`
`5
`
`10
`
`15
`
`25
`
`30
`
`35
`
`40
`
`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 wake
`fulness 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 resis
`tance 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 supplied
`to a patient.
`
`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 particular patient varies
`depending on patient’s particular condition. Such amount of
`pressure may be determined utilizing any conventional PAP
`therapy methods.
`The mask 20 covers the patient’s nose and/or mouth. Con
`ventional 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 sen
`sors 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 process
`ing arrangement 24 outputs a signal to a conventional 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 generators 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.
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`obstruction easily recognized 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 otherforms of obstruc
`tive apnea. FIG.5 shows a breathing pattern of a patient on the
`PAP therapy which includes an event of elevated upper air
`way 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 repetitive and cyclical (e.g., regu
`larly 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 minutes of
`normal sleep, a breathing pattern is often characterized by
`irregular breathing. This pattern represents a potential excep
`tion 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 associated pattern of breathing
`may include, e.g., the absence of larger breaths, especially
`after pauses, generally high respiratory 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 sepa
`ration 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 moni
`tor the patient’s breathing and simultaneously determine
`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 riot
`the patient is awake. When a database of the patient’s breath
`ing characteristics has been built, determinations as to the
`patient’s wakefulness may be made significantly more accu
`rate.
`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 pro
`cessing arrangement 24 adjusts the pressure to correspond to
`the patient’s current state (step 208). For example, if the
`patient has been awakened and the patient's breathing pat
`terns 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
`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
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`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 pat
`tern shown in FIG. 7 to the pattern shown in FIG. 4. In such a
`case, the processing arrangement 24 should increase the pres
`Sure. 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 indi
`cates an event of elevated upper airway resistance and hypop
`nea 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 applications.
`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 patients
`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 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 por
`tion 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 arrangement 24 may
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`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 sys
`tem 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 determines a first
`state of the patient based on data obtained from the sensors 23
`regarding the breathing pattern of the patient. In this embodi
`ment, 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 embodiment, the processing arrangement 24
`may detect whether, for example, the patient is in the sleep
`state. That is, the system 1 may be applied when the patient is
`in the wake state. After the system 1 is initialized, the pro
`cessing arrangement 24 may default to assuming that the
`patient is in the wake state. Thus, the processing arrangement
`24 may only detect whether the patient is in the sleep state,
`and when the sleep state is not detected, default to assuming
`that the patient is in the wake state.
`In step 256, the processing arrangement applies Supplies
`the air pressure as a function of the state. In one