(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(19) World Intellectual Property Organization
`International Bureau
`
`1111111111111111 IIIIII 111111111111111 lllll lllll lllll lllll 11111111111111111111111
`
`(43) International Publication Date
`25 January 2001 (25.01.2001)
`
`PCT
`
`(10) International Publication Number
`WO 01/05460 Al
`
`(51) International Patent Classification 7:
`
`A61M 16/00
`
`(74) Agent: F.B.RICE & CO.; 605 Darling Street, Balmain,
`NSW 2041 (AU).
`
`(21) International Application Number: PCT/AU00/00370
`
`(22) International Filing Date:
`
`26 April 2000 (26.04.2000)
`
`(25) Filing Language:
`
`(26) Publication Language:
`
`English
`
`English
`
`(30) Priority Data:
`PP9964
`
`23 April 1999 (23.04.1999) AU
`
`(71) Applicant (for all designated States except US): AUS(cid:173)
`TRALIAN CENTRE FOR ADVANCED MEDICAL
`TECHNOLOGY LTD. [AU/AU]; David Read Labo(cid:173)
`ratories D06, Dept. of Medicine, University of Sydney,
`Sydney, NSW 2006 (AU).
`
`(81) Designated States (national): AE, AG, AL, AM, AT, AU,
`AZ, BA, BB, BG, BR, BY, CA, CH, CN, CR, CU, CZ, DE,
`DK, DM, DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU,
`ID, IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS,
`LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, NO, NZ,
`PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT,
`TZ, UA, UG, US, UZ, VN, YU, ZA, ZW.
`
`(84) Designated States (regional): ARIPO patent (GH, GM,
`KE, LS, MW, SD, SL, SZ, TZ, UG, ZW), Eurasian patent
`(AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), European patent
`(AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU,
`MC, NL, PT, SE), OAPI patent (BF, BJ, CF, CG, CI, CM,
`GA, GN, GW, ML, MR, NE, SN, TD, TG).
`
`Published:
`-
`With international search report.
`
`(72) Inventor; and
`(75) Inventor/Applicant (for US only): SULLIVAN, Colin
`[AU/AU]; David Read Laboratories D06, Dept.
`of
`
`For two-letter codes and other abbreviations, refer to the "Guid(cid:173)
`ance Notes on Codes and Abbreviations" appearing at the begin(cid:173)
`ning of each regular issue of the PCT Gazette.
`
`!IO
`
`!,()
`
`70
`
`f(X)
`
`60
`
`= Medicine, University of Sydney, Sydney, NSW 2006 (AU).
`-iiiiiiiiiiii
`= (54) Title: APPARATUS AND METHOD FOR THE TREATMENT OF AN UPPER AIRWAY FLOW LIMITATION
`iiiiiiiiiiii =
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`~ = 0 (57) Abstract: An apparatus and a method for the treatment of an upper airway flow limitation, the apparatus including a means to
`
`:;;_.. detect an interruption in an upper airway inspiratory flow rate of the patient and further including a treatment means which treats the
`;;-,- upper airway flow limitation on detection of the interruption cycle.
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`APPARATUS AND METHOD FOR THE TREATMENT OF AN UPPER
`AIRWAY FLOW LIMITATION
`
`Technical Field
`The present invention concerns an apparatus and method for the
`treatment of an upper airway flow limitation in a patient. In particular, the
`present invention concerns an apparatus and method of treating
`hypertension caused by pre-eclampsia.
`Background
`Hypertension in pregnancy is associated with increased risk of foetal
`growth retardation and in severe cases can lead to both maternal and foetal
`problems. It is the major complication of pregnancy and is one of the three
`leading causes of maternal death.
`Hypertension in pregnant women is either a chronic condition caused
`by a disease unrelated to pregnancy (essential or secondary hypertension), or
`caused by a pregnancy induced condition known as "pre-eclampsia" (also
`known as "pregnancy induced hypertension"). In the former condition,
`elevated blood pressure is the cardinal patho-physiological feature. In pre(cid:173)
`eclampsia, the increased blood pressure is a sign of the underlying disorder
`and the impact of the two conditions and their management on the mother
`and foetus is quite different. An attempt to differentiate these two classes of
`patient has led to confusion in terminology worldwide.
`The circadian blood pressure (BP) variation in normal pregnancy is
`similar to that of non-pregnant women, with the highest value being in the
`morning and the lowest around midnight. A similar pattern exists in
`pregnancy accompanied by chronic ( essential) hypertension.
`In contrast, in women with pre-eclampsia, the diurnal blood pressure
`pattern is reversed with the maximum blood pressure occurring at night.
`Pre-eclampsia is a disease of the placenta with widespread systemic
`effects affecting maternal renal, cerebral, hepatic and/or clotting functions.
`The principal clinical features include hypertension, proteinuria and oedema
`with any or all of these present.
`While there are generally agreed risk factors for pre-eclampsia, the
`precise causes and mechanisms remain unproved. In addition, there are no
`clear indicators that are useful in predicting the occurrence or the severity of
`the condition. There are no known effective preventative measures and
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`although various techniques and medications are used to limit the symptoms
`(in particular the hypertension), the only definitive treatment is delivery of
`the baby, and removal of the diseased placenta.
`Pre-eclampsia usually occurs after 20 weeks gestation and most
`frequently near term. Pre-eclampsia (and the hypertension associated with
`it) is a different medical condition to essential or secondary hypertension
`(e.g., as illustrated by the different diurnal characteristics). The methods
`used to manage patients with pre-eclampsia mainly consist of closely
`monitoring the patient and if necessary, controlling blood pressure with
`medication. In severe cases, additional medications are used to prevent
`convulsions (eclampsia).
`It has been recognised that obstructive sleep apnea (OSA) is related to
`elevated blood pressure. The inventor has previously demonstrated the
`treatment of OSA by use of Continuous Positive Airway Pressure (CPAP), and
`in particular nasal-Continuous Positive Airway Pressure (nCPAP). It has also
`been demonstrated that partial airflow limitation (upper airway resistance
`syndrome "UARS") can cause elevations in blood pressure and that the blood
`pressure can be controlled by the use of CPAP, and in particular nCPAP.
`However patients with pre-eclampsia-induced hypertension may not display
`symptoms indicative of UARS. Accordingly, UARS symptoms in such a
`patient may be missed resulting in the hypertension caused by pre-eclampsia
`going untreated.
`
`Summary of the Invention
`In a first aspect, the present invention consists in an apparatus for the
`treatment of an upper airway flow limitation in a patient the apparatus
`including;
`a means to detect at least one interruption cycle in an upper airway
`inspiratory flow rate of the patient wherein the interruption cycle is
`characterised by a decrease in upper airway inspiratory flow rate followed by
`an increase in the upper airway inspiratory flow rate: and
`a treatment means which treats the upper airway flow limitation on
`detection of said at least one interruption cycle in the upper airway
`inspirato1y flow rate.
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`In one embodiment, the detection means of the apparatus is adapted to
`detect a plurality of interruption cycles in the upper airway inspiratory flow
`rate.
`
`In a further embodiment. the interruption cycle is indicative of an
`upper airway flow limitation.
`In a further embodiment, the detection means detects a decrease in the
`inspiratory flow rate followed by a subsequent increase in inspiratory flow
`rate. In this embodiment, the flow rate is interrupted. and the flow rate
`decreases, followed by a recovery whereupon the flow rate increases before
`the flow rate finally decreases towards the end of inspiration.
`In another embodiment, the subsequent increase in inspiratory flow
`rate increases the inspiratory flow rate to a maxima that is substantially the
`same as the rate before the decrease in inspiratory flow rate.
`In a further embodiment. the subsequent increase in inspiratory flow
`rate increases the inspiratory flow rate to a maxima that is relatively lesser
`rate than the rate before the decrease in inspiratory flow rate.
`In yet a further embodiment the subsequent increase in inspiratory
`flow rate increases the inspiratory flow rate to a maxima that is relatively
`greater rate than the rate before the decrease in inspiratory flow rate.
`In a still further embodiment, the detection means is adapted to detect
`the occurrence of at least two or more interruption cycles in the upper
`inspiratory flow rate and the treatment means treats the airway limitation on
`detection of said at least two interruption cycles.
`In another embodiment. the apparatus is used in the treatment of
`hypertension caused by pre-eclampsia. In this embodiment, the interruption
`to inspiratory flow rate is indicative of an upper airway flow limitation which
`can lead to pre-eclampsia induced hypertension. The type of interruption
`cycle detected may not be observed in a breathing pattern of a patient
`suffering from another form of airway limitation such as snoring or sleep
`apnea. While there is still an inspiratory airway flow limitation in a patient
`suffering from another form of airway limitation, the increase in airway flow
`following a decrease in airway flow is not observed. Instead, the inspiratory
`flow rate continues to decrease at a certain rate until inspiration ends and
`expiration begins.
`In a further embodiment of the first aspect of the invention, the
`detection means includes a means for measuring vibrations in a patient's
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`airway. Preferably, the detection means to detect the at least one
`interruption cycle further includes an identification means for identifying
`those measured airway vibrations which are indicative of the upper airway
`flow limitation.
`In a further embodiment, the measured vibrations in the patient's
`airway indicative of upper airway flow limitation are caused by a decrease in
`the diameter of the airway followed by a subsequent increase in the diameter
`of the airway.
`In another embodiment, the subsequent increase in diameter of the
`airway increases the diameter to substantially the same diameter as before
`the decrease in diameter of airway.
`In a further embodiment, the subsequent increase in diameter of the
`airway increases the diameter to a diameter less than the diameter before the
`initial decrease in diameter of the airway.
`In a further embodiment, the subsequent increase in diameter of the
`airway increases the diameter to a diameter greater than the diameter before
`the initial decrease in diameter of the airway.
`In a second aspect, the present invention consists in an apparatus
`when used in the treatment of hypertension caused by pre-eclampsia, the
`apparatus including:
`a flow rate measurement means which measures an air flow intake rate
`in an airway of a patient; and
`a treatment means which treats an upper airway flow limitation in the
`patient when the measured air flow intake rate falls below a pre-determined
`flow rate to alleviate hypertension caused by pre-eclampsia.
`In a third aspect, the present invention consists in an apparatus for the
`treatment of hypertension caused by pre-eclampsia. the apparatus including:
`a measuring means for measuring airway vibrations in a patient:
`an identification means which identifies those measured airway
`vibrations which are indicative of an upper airway flow limitation; and
`a treatment means which treats the upper airway flow limitation in the
`patient.
`In one embodiment of the third aspect. the apparatus is used for the
`treatment of hypertension caused by pre-eclampsia.
`In a fourth aspect, the present invention consists in a method of
`treating an upper airway flow limitation in a patient including the steps of:
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`detecting at least one interruption cycle in an upper airway inspiratory
`flow rate of the patient wherein the interruption cycle is characterised by a
`decrease in upper airway inspiratory flow rate followed by an increase in the
`upper airway inspiratory flow rate; and
`treating the upper airway flow limitation on detection of an
`interruption cycle in the upper airway inspiratory flow rate.
`In one embodiment of the fourth aspect of the invention. the detecting
`step comprises detecting a plurality of interruption cycles in the upper
`airway inspiratory flow rate.
`In a further embodiment of the fourth aspect of the present invention,
`the method is used to treat hypertension caused by pre-eclampsia.
`In a fifth aspect, the present invention consists in a method of treating
`a patient for hypertension caused by pre-eclampsia, the method including the
`steps of:
`measuring an air flow intake rate in an airway of the patient; and
`treating an upper airway flow limitation in the patient when the
`measured air flow intake rate falls below a pre-determined flow rate to
`alleviate hypertension caused by pre-eclampsia.
`In a sixth aspect, the present invention consists in a method of treating
`a patient for an upper airway flow limitation, the method including the steps
`of:
`
`measuring airway vibrations in the patient;
`identifying those measured airway vibrations which are indicative of
`the upper airway flow limitation;
`on identification, treating the upper airway flow limitation in the
`patient.
`In one embodiment of the sixth aspect, the method is used to treat
`hypertension caused by pre-eclampsia.
`The inventor has observed that women with pre-eclampsia exhibit
`substantial blood pressure elevations during sleep even when medicated
`following current medical practice to control blood pressure. The present
`invention results from the inventor's observation that there is upper airway
`flow limitation (in the absence of apnea) in the majority of these patients. As
`mentioned above, upper aiiway vibration is well known in snoring, where
`the base frequency of flutter is usually above 30 Hz. However. in pre(cid:173)
`eclamptic women. the upper airway often has a much lower vibration
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`frequency, with a base frequency of flutter in the range of about 0.2 to about
`10 Hz (typically about 1-2 Hz).
`Whereas these women on occasions may also produce audible snoring
`(which would be recognised by an observer) the low frequency vibrations are
`not audible, and would not be detected by commonly used sleep and
`breathing recordings, thus failing to reveal the upper airway functional
`abnormality. The inventor has found that this type of low frequency
`vibrations is representative of an upper airway flow limitation which is the
`cause of increasing blood pressure in sleeping patients with pre-eclampsia.
`likely through the effect of the limitation of reducing ventilation and
`increasing arterial carbon dioxide.
`As noted in the background, the only cure for pre-eclampsia is delivery
`of the baby and placenta. This invention does not claim to prevent or treat
`pre-eclampsia but aims to minimise hypertension that is present due to the
`pre-eclampsia. As such, at least some embodiments of this invention may be
`used as an additional tool by clinicians treating patients with pre-eclampsia.
`In one embodiment of the first, second and third aspects, the treatment
`means is a device which applies Continuous Positive Airway Pressure
`(CPAP), more preferably nasal-Continuous Positive Airway Pressure (nCPAP),
`to the airway of the patient. In another embodiment of the apparatus, the
`treatment means is a device which induces positive airway pressure therapy.
`In another embodiment, the flow rate measurement means and the
`treatment means may be constructed together as part of one apparatus. such
`as the AutoSet product from ResMed described in US Patent No 5245995. the
`contents of which are incorporated herein by reference. This apparatus
`senses and responds to airway flow limitations and. once appropriately
`modified, could be used to sense an upper airway flow limitation
`characterised by at least one decrease in upper airway inspiratory flow rate
`followed by at least one increase in flow rate.
`In a further embodiment, the treatment means may operate with two
`modes of delivery, a first mode for use when the patient is awake, and a
`second mode for use when the patient is asleep. In the first mode of air
`delivery, the treatment means provides a minimally intrusive air and
`pressure delivery to the patient, and hence is more comfortable. In the
`second mode of air delivery. the treatment means provides a relatively
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`greater air and pressure delivery to the patient than in the first mode, which
`is sufficient to treat an air flow limitation.
`In another embodiment. the treatment means may additionally include
`a sleep sensor which senses whether or not the patient is asleep, and may
`also include a switching means which responds to the sleep sensor and
`automatically switches the treatment means between the two modes of air
`delivery. This embodiment addresses one of the key issues in treating blood
`pressure elevations during sleep in women with pre-eclampsia, namely the
`comfort of CPAP, including nCPAP, or positive airway pressure therapy.
`This feature is an improvement over the prior art because as soon as the
`patient goes to sleep (as determined by an appropriate sensing algorithm in
`the treatment means), the second treatment mode is activated. In the known
`devices. the second treatment mode is not activated is not activated until the
`end of the "setting time" period which may lead to the activation of the
`second treatment mode being delayed beyond that desirable or activated
`before the patient has in fact gone to sleep.
`In a further embodiment, the sleep sensor is adapted to register that
`the patient is asleep when there is a reduced average airflow in the patient's
`upper airway. Another embodiment is adapted to register that the patient is
`asleep when a movement sensor detects a reduced respiration effort by the
`patient. In another embodiment. known ECG techniques are used for
`establishing whether the patient is awake or asleep.
`In another embodiment, the identification means is adapted to identify
`airway vibrations in the frequency range of 0.2 to 10 Hz as airway vibrations
`which are indicative of an upper airway flow limitation.
`In a further embodiment, the identification means is adapted to
`identify airway vibrations in the frequency range of 0.5 to 5 Hz as airway
`vibrations which are indicative of an upper airway flow limitation.
`In another embodiment. the detection means and the identification
`means are together capable of detecting and generating an output signal
`representative of the breathing cycle of the patient. A breathing cycle
`detection and identification means is disclosed in International Application
`No PCT/AU96/00306, the contents of which are incorporated herein by
`reference. While the breathing rate of a human can vary significantly due to
`such factors as illness or exertion, the frequency of the breathing cycle of a
`sleeping human typically lies in the range of greater than O Hz and less than
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`or equal to 2 Hz. The advantage of having the apparatus generate an output
`signal representative of the breathing cycle is that the airway vibrations
`indicative of an upper airway flow limitation can be time-locked to the
`breathing cycle. If peaks in the signal occur during inspiration or expiration,
`this provides confirmation that the signal being received is in fact due to
`airway vibrations, rather than from some other source.
`In a further embodiment, the apparatus may include a comparator
`means which compares the signal representative of the breathing cycle with
`a signal indicative of airway vibrations, and produces an output indicative of
`the comparison.
`In another embodiment, the measuring means which measures airway
`vibrations may be selected from the group consisting of a pressure detector
`comprising a piezoelectric transducer and an accelerometer comprising an
`integrated circuit containing a floating piezoelectric transducer. The
`pressure or acceleration detector can be placed on or under the mattress of a
`bed on which the patient will sleep. This arrangement is particularly
`advantageous as there is no discomfort caused to the patient by the
`attachment of any sensors. This arrangement also avoids the high risk of
`detachment or disconnection of sensors attached to the patient during the
`long hours of sleep. The detector could also be attached to the bed frame or
`incorporated in a pillow as well as or instead of on or under the mattress. The
`detector may further be attached to a hearing aid placed in the ear of the
`patient.
`In a further embodiment. the pressure detector can comprise a
`piezoelectric transducer while the accelerometer can comprise an integrated
`circuit containing a floating piezoelectric transducer. In a preferred
`embodiment, the piezoelectric transducer comprises one or a plurality of
`sheets of piezoelectric plastics material such as polyvinylidene fluoride
`(hereinafter called PVDF) or an analogue or family derivative thereof. PVDF
`is an ideal material for this invention as it has a potential frequency response
`from sub Hertz (ie less than one cycle per second) to kiloHertz levels. In
`addition, the material is highly sensitive, producing relatively larger voltages
`in response to extremely small movements. It can. for example. act as a
`highly sensitive microphone detecting low levels of sound pressure. In this
`invention, the microphone property of PVDF is used to essentially "listen" to
`the vibrations of the patient's airway. This embodiment takes advantage of
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`the physical properties of this plastic, which is robust. to characterise the
`vibration of the airway, and preferably the breathing cycle of the patient, to
`identify the dominant frequency components of these actions and, by
`comparison, to positively separate each action thus allowing the generation
`of electrical signals which can be recorded and identified as that of the
`vibration of the airway and breathing movements.
`In yet a further embodiment. the piezoelectric plastics material may
`consist of a layer of this material attached to a firm rubber or plastic backing
`sheet, with or without an air space. Multiple layers of the piezoelectric
`material throughout a mattress may also be utilised where appropriate.
`In another embodiment, the detector detects movements of low
`frequency (e.g. about 0-5 Hertz) which can be digitally processed and
`amplified to give a signal representative of the breathing cycle (inspiration
`and expiration) of the patient. The detector will be able to detect sub-audible
`vibrations of the patient's airway which may also be digitally processed and
`amplified to give a signal representative of the sub-audible vibrations in the
`airway.
`Brief Description of the Drawings
`The following description of a preferred embodiment of the present
`invention is provided as an example of the invention and is described with
`reference to the accompanying drawings in which:-
`Figure 1 is a graph of the breathing cycle of a patient with pre(cid:173)
`eclampsia;
`Figure 2 is a schematic representation of an embodiment of an
`apparatus for treating a patient with hypertension caused by pre-eclampsia;
`Figure 3 is a schematic representation of another embodiment of an
`apparatus for treating a patient with hypertension caused by pre-eclampsia.
`Figure 4 is a schematic representation of a further embodiment of an
`apparatus for treating a patient with hypertension caused by pre-eclampsia.
`Detailed Description of the Drawings
`Figure 1 is a graph of the breathing cycle of a patient with pre(cid:173)
`eclampsia. Small interruptions to inspiratory flow 10 superimposed at the
`peak 20 of each cycle are indicative of an upper airway flow limitation. not
`usually associated with audible snoring. In each case, the interruption 10
`comprises at least a first decrease 11 in the inspiratory flow rate and a
`subsequent increase 12 in inspiratory flow rate. In this way. the flow rate is
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`interrupted, followed by a "recovery" before finally decreasing towards the
`end of inspiration.
`The small interruptions 10 in inspiratory flow are not observed in the
`breathing patterns of a patient suffering from snoring in which case whilst
`there is still a flow limitation, there is no "recovery" of flow rate as observed
`in a patient with pre-eclampsia.
`Figure 2 shows a patient 30 being treated for hypertension caused by
`pre-eclampsia. The patient 30 is laying on a bed 40, and has a mask 50
`covering the nose. The mask 50 is shown connected by 80 to a nasal-
`Continuous Positive Airway Pressure (nCPAP) apparatus 90. The flow rate
`measurement means 70 detects the rate at which the patient breathes in air,
`and generates a signal which is sent to a central controller 100. When the
`flow rate measurement means 70 detects the interruptions to inspiratory flow
`10, the controller 100 activates a switch 110 which activates the nCPAP
`apparatus 90 to supply air to the patient 30 at a pressure which ameliorates
`or eliminates the upper airway flow limitation for that patient.
`In another embodiment of the invention when the flow rate
`measurement means 70 detects that the flow rate has fallen below a present
`level, the controller 100 activates the nCPAP apparatus 90 to supply air to the
`patient 30 at a pressure which ameliorates or eliminates the upper airway
`flow limitation. When the flow rate measurement means 70 detects that the
`flow rate increases above the preset level, the controller activates the switch
`110 to switch the nCPAP apparatus 90 into a mode in which a reduced air
`pressure is applied to the patient's airways. The patient is assumed to be
`awake in this mode.
`Figure 3 shows another embodiment of an apparatus for treating a
`patient 30 for hypertension caused by pre-eclampsia. The same reference
`numerals are used where the features are the same as in Figure 2. This
`embodiment uses a mat 120 with a measuring means 130 beneath the patient
`30 to measure airway vibrations of the patient. When airway vibrations are
`detected and determined to be representative of at least one interruption
`cycle, a signal is sent to the controller 100. The controller 100 then activates
`the switch 110, which switches on the nCPAP apparatus 90. The nCPAP
`apparatus 90 then supplies air to the patient 30 at a pressure which
`ameliorates or eliminates the upper airway flow limitation for that patient.
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`WO 01/05460
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`PCT/AU00/00370
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`11
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`Figure 4 depicts a further embodiment of the invention wherein, mat
`120, having measuring means 130, is placed beneath the patient 30 to
`measure airway vibrations in the patient. The measuring means 130 is
`connected by appropriate electrical leads to an electronic amplifier device
`140. The amplified signals are then passed to a comparator 150 which is
`adapted to discriminate from the signals output from the measuring means
`130 signals representative of the breathing cycle of the patient and of
`episodes of airway vibrations which are representative of at least one
`interruption cycle. The amplified signals from the comparator can be fed to a
`display means 160 or fed directly to controller 100. The controller 100
`activates switch 110 which activates the nCPAP apparatus 90 to supply air to
`the patient 30 at a pressure which ameliorates or eliminates the upper airway
`flow limitation for that patient.
`It will be appreciated by persons skilled in the art that numerous
`variations and/or modifications may be made to the invention as shown in
`the specific embodiments without departing from the spirit or scope of the
`invention as broadly described. The present embodiments are, therefore, to
`be considered in all respects as illustrative and not restrictive.
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`CLAIMS:-
`An apparatus for the treatment of an upper airway flow limitation in a
`1.
`patient, the apparatus including;
`a means to detect at least one interruption cycle in an upper airway
`inspiratory flow rate of the patient wherein the interruption cycle is
`characterised by a decrease in upper airway inspiratory flow rate followed by
`an increase in the upper airway inspiratory flow rate; and
`a treatment means which treats the upper airway flow limitation on
`detection of said at least one interruption cycle in the upper airway
`inspiratory flow rate.
`The apparatus of claim 1 wherein the detection means is adapted to
`2.
`detect a plurality of interruption cycles.
`The apparatus of claim 1 or claim 2 when used in the treatment of
`3.
`hypertension caused by pre-eclampsia.
`The apparatus of any one of the preceding claims wherein the means
`4.
`to detect the at least one interruption cycle includes a means for measuring
`vibrations in a patient's airway.
`The apparatus of claim 4 wherein the means to detect the at least one
`5.
`interruption cycle further includes a means for identifying those measured
`airway vibrations which are indicative of the upper airway flow limitation.
`6.
`The apparatus of any one of claims 1 to 3 wherein the means to detect
`the at least one interruption cycle includes a flow rate measurement means
`which measures the air flow intake rate in the airway of the patient.
`An apparatus when used in the treatment of hypertension caused by
`7.
`pre-eclampsia, the apparatus including:
`a flow rate measurement means which measures an air flow intake rate
`in an airway of a patient; and
`a treatment means which treats an upper airway flow limitation in the
`patient when the measured air flow intake rate falls below a pre-determined
`flow rate to alleviate hypertension caused by pre-eclampsia.
`An apparatus for the treatment of hypertension caused by pre-
`8.
`eclampsia, the apparatus including:
`a measuring means for measuring airway vibrations in a patient;
`an identification means which identifies those measured airway
`vibrations which are indicative of an upper airway flow limitation: and
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`SUBSTITUTE SHEET (RULE 26)
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`ResMed Inc. Exhibit 1006
`Page 13 of 25
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`PCT/AU00/00370
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`a treatment means which treats the upper airway flow limitation in the
`patient.
`The apparatus of claim 8 when used for the treatment of hypertension
`9.
`caused by pre-eclampsia.
`The apparatus of claim 8 or claim 9 wherein airway vibrations in the
`10.
`frequency range of about 0.2 to about 10 Hz are identified by the
`identification means as indicative of the upper airway flow limitation.
`11. The apparatus of claim 8 or claim 9 wherein airway vibrations in the
`frequency range of about 0.5 to about 5 Hz are identified by the identification
`means as indicative of the upper airway flow limitation.
`12. The apparatus of any one of claims 8 to 11 wherein the identification
`means is capable of generating a signal representative of the breathing cycle
`of the patient.
`The apparatus of claim 12 wher