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`US 20(140059236Al
`
`(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2004/0059236 A1
`
`(43) Pub. Date:
`Mar. 25, 2004
`Margulios ct :11.
`
`Publication Clafisificution
`
`A6113 5/02
`600/500
`
`
`
`Int. (:1.7 ............. ..
`(51)
`(52) U.S.Cl.
`............. ..
`
`(s7)
`
`ABSTRACF
`
`An apparatus and method [or (lcloction and monitoring ()1
`autonomic nervous system (ANS) activity in humans, pri—
`marily in [he field of siccp research. The prescnl invenlion
`discloses a porlahlc, simpic, and cosi-cfl‘cctivu clcclronic
`device conlaining hardware and sol'lwarc lhal permits real-
`1imc monitoring of a pulsatilc blood volume waveform
`obtained lhrough um: of a pholoplcthysmographic (optical
`volume detecting) probe. thereby allowing signal condition-
`ing,wuvc1‘orm slope analysis. display, recording, and output
`of pulse Iransilional slope Llala rcprcscmalivc of aclivity in
`Ihc ANS.
`
`LIGHT SOURCE
`
`(54) METHOD AN!) APPARATUS FOR
`MONITORING THE AUTONOMIC NERVOUS
`SYSTEM
`
`(715)
`
`Invcnlors: Ler Aaron Margulies, Scalllc, WA
`(US): David B. Harrell. Mukillco. WA
`(US); Michael Allen Higgins. Scatllc,
`WA (US)
`
`('(irrcsIXindnncc Address:
`GARRISON ASSOCIATES
`2001 SIXTH AVENUE
`SUITE 3301]
`SliA'l'l'Ll‘Z, WA 981212522
`
`(2|) Appl. No:
`
`101666.121
`
`(22
`
`Filed:
`
`Sep. 19, 2903
`
`Related U.S. Application Data
`
`(60)
`
`Provisional applicaiion No. 60,412,310, filed on Sep.
`21), 3002.
`
`
`
`PHOTODETECTOR
`
`001
`
`Apple Inc.
`APLl 034
`
`US. Patent No.
`
`8,923,941
`
`FITBIT, EX. 1034
`
`Apple Inc.
`APL1034
`U.S. Patent No. 8,923,941
`
`001
`
`FITBIT, Ex. 1034
`
`

`

`Patent Application Publication Mar. 25, 2004 Sheet 1 of 7
`
`US 2004{0059236 A1
`
`FIG.1
`
`LIGHT SOURCE
`
`
`
`PHOTODETECTOR
`
`VARIABLE ABSORPTION
`DUE TO PULSE-ADDED
`VOLUME OF ARTERIAL
`BLOOO
`ABSORPTION DUE
`TO ARTERIAL BLOOD
`
`ABSORPTION DUE
`TO VENOUS BLOOD
`
`ABSORPTION
`DUE TO TISSUE
`
`
`
`____._.....______.._._._._._-—_
`
`ABSORPTION
`
`TIME
`
`FIG.2
`
`002
`
`FITBIT, EX. 1034
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`

`

`Patent Application Publication Mar. 25, 2004 Sheet 2 0f 7
`
`US 2004(0059236 A1
`
`FIG.3
`
`.——-——.——_.._ PEAK TOP
`
`SLOPE END
`
`PEAK BOTTOM
`
`
`
`dPidt
`
`PERIPHERAL PULSE WAVEFORM
`
`003
`
`FITBIT, EX. 1034
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`003
`
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`

`

`Patent Application Publication Mar. 25, 2004 Sheet 3 0f 7
`
`US 200410059236 A]
`
`FIG.4A
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`
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`

`

`Patent Application Publication Mar. 25, 2004 Sheet 4 of 7
`
`US 2004f0059236 A]
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`Patent Application Publication
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`Mar. 25, 2004 Sheet 6 0f 7
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`US 2004f0059236 A]
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`Patent Application Publication Mar. 25, 2004 Sheet 7 0f 7
`
`US 2004(0059236 A1
`
`DISPOSING A
`PHOTO-PLETHYSMOGRAPHIC PROBE
`PROXIMAL TO A SINGLE BODY PART
`
`DEFINING A CONTINUOUS PULSATILE
`BLOOD VOLUME WAVEFORM AS A
`FUNCTION OF PULSE AMPLITUDE AND
`TIME
`
`
`
`
`
`DEFINING A TIME INTERVAL FOR
`CALCULATION OF A SLOPE OF THE
`PULSATILE BLOOD VOLUME WAVEFORM
`
`TIME INTERVAL
`
`PERFORMING CONTINUOUS
`CALCULATION OF THE SLOPE OF THE
`RISING SEGMENT OF EACH BLOOD
`VOLUME WAVEFORM OVER DEFINED
`
`PROCESSING INPUT DATA T0 DIVIDE
`PEAK AMPLITUDE VALUES BY A GIVEN
`TIME CONSTANT
`
`ELIMINATING FROM FURTHER
`CALCULATION SLOPE VALUES OF LESS
`THAN ONE
`
`SIGNAL PROCESSING, CONDITIONING.
`AND ARTIFACT REJECTION
`
`AMPLIFYING AND FILTERING SLOPE
`VALUES
`
`PROVIDING DATA
`
`
`OUTPUT
`
`
`REPRESENTATIVE
`
`
`OF SLOPE VALUES
`FOR USE BY
`
`
`OTHER DEVICES
`
`
`
`STORING
`ELECTRON 3c DATA
`REPRESENTATIVE
`0F SLOPE VALUES
`
`
`
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`
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`PROVIDING AN
`
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`
`SEIEESFE’fififig‘;
`REPRESENTATIVE
`OF SLOPE VALUES
`
`008
`
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`

`US 2tl04f005 9236 Al
`
`Mar. 25, 2004
`
`METHOD AND APPARATUS FOR MONITORING
`THE AUTONOMIC NERVOUS SYSTEM
`
`CROSS—REFERENCE. TO RELATED
`APPLICNI‘ION
`
`[0001] This application claims benefit of United States
`Provisional Application Serial No. 6(IX412,310 entitled
`Method and Apparatus for Monitoring the Autonomous
`Nervous System, filed Sep. 20, 2002.
`TECI-INTCAI. FIELD
`
`[0002] This invention relatesto medical devices, and more
`particularly to physiological monitoring methods and
`devices used for detection of autonomic nervous system
`(ANS) activity in the field of sleep research. The present
`invention discloses a portable, simple, and cost-effective
`electronic sleep diagnostic device containing hardware and
`software that permits recording and signal conditioning of'a
`pu lsatile blood volume waveform obtained through use of a
`photoplethysmographic (optical volume detecting) probe.
`thereby allowing analysis pulse transitional slope data that is
`representative of activity in the autonomic nervous system
`(ANS).
`
`BACKGROUND OF THE INVENTION
`
`risk is directly linked to sleep
`[0003] Cardiovascular
`related breathing disorders (SRBD). The number of US.
`laboratories that study sleep. roughly 2,792,
`is incredibly
`low when compared to the number of Americans estimated
`to have a chronic SRBD, just over 40 million. The average
`number of beds per lab is 3.6 bringing the total number of
`beds in which to do a sleep study to roughly [0,000. This
`means that to test all 40 million Americans, there would be
`4,000 patients that would be seen per bed. if sleep tests were
`run 365 days per year, the result is an astounding 11 years
`of conclusive tests needed to be run to test
`the current
`population ol‘individuals suffering form SRBD. The length
`of time increases as one considers the actual number of days
`per year sleep labs actually test patients, plus the amount of
`tests that need to be re-run due to inconclusive testing, plus
`the number of patients that continu ally need to he retested to
`see if their treatment is functioning property. Given this
`scenario, it
`is no shock that wait times for patients to be
`scheduled for a sleep test can typically range from six weeks
`to six months The problem will only increase, as "it
`is
`estimated that nearly 80 million Americans will have a sleep
`problem by the year 3010 and 100 million will have one by
`the year 2050." Clearly then, the problem with wait time for
`testing should he addressed immediately to relieve pent up
`demand.
`
`testing sleep
`[0004] The current "gold standard" for
`related breathing disorders is full polysomnography. Full
`polysomnography is. however, quite
`labor
`intensive,
`requires considerable instrumentation and is therefore rather
`expensive to conduct. As a result, many sleep laboratories
`have found it difficult to keep up with the demand for this
`test, and a long waiting list becomes the norm. Given that
`obstructive sleep apnea (OSA) is quite prevalent, leads to
`serious complications and that treatment options exist, it is
`imponant
`that individuals suffering from the disease are
`identified.
`
`[0005] The need to study the ANS has been realized in
`academia for a considerable time. It is known in the field of
`
`mieroneurography that rapidcye movement (REM) sleep is
`associated with profound sympathetic activity.
`it has also
`been found that arousals from non—rapid—eyc movement
`(NREM) elicits K complexes that are associated with symA
`pathetic activity. The sympathetic division of the ANS
`prepares a body for movement. Arousals require movement
`and hence an arousal requires sympathetic activation.
`[0006] Generally, patients with USA, a type of SRBD,
`have extremely disrupted sleep and terribly high daytime
`somnolencc. Obstructive sleep apnea events are always
`accompanied by an acute rise in systolic blood pressure
`(rises in systolic blood pressure are associated with sympa-
`thetic activation), even when the usual EEG criteria for
`arousals are not met {a recognizable cortical electroencepha-
`lographic arousal). The duration of the apnea of individuals
`that demonstrate EEG arousal and those that do not meet the
`usual criteria for defining an arousal have been found to be
`identical. The pleural pressure peak, at the end of apnea. is
`identical between the two types of arousals, as are the EEG
`frequencies. These findings suggest
`that monitoring the
`cardiac changes of sleep is a more accurate measurement.
`
`It has been demonstrated that apneic episodes
`[0007]
`result in progressive increases in sympathetic nerve activity.
`The increases are most marked toward the end of the apnea,
`when a patient moves. These findings are exactly what is
`excepted of sympathetic activation and its relationship to
`arousals in patients with SRBD.
`
`[0008] Because cardiovascular control during sleep is pri-
`marily dictated by brain states that produce profound varia-
`tion in ANS activity, many studies have been conducted to
`monitor the ANS. Since the data shows clearly that moni-
`toring the ANS or cardiac changes in sleep yields more
`accurate data defining an arousal
`in sleep,
`it
`is clear that
`diagnoeaic studies must include ANS or cardiac monitoring.
`[0009]
`It has been shown that in transitions from NREM
`to REM sleep, heart rate accelerations precede the EEG
`arousals marking the onset of REM. Therefore, not only
`does monitoring ANS activity give the clinician a possibly
`more accurate study, but also changes in ANS activity
`precede that information being observed via the EEG elec—
`trodes.
`
`[0010] There are two existing technologies that attempt to
`monitor the ANS, namely pulse transit
`time (PTT) and
`peripheral arterial tonometry (PAT). Neither PTT nor PAT
`can lay claim to monitoring the ANS without adding addi-
`tional sensors. PTT requires the use of ECG electrodes that
`may be difficult for a patient
`to self—apply due to skin
`cleaning and shaving requirements. PAT requires a very
`costly gauntlet~type device with a single—use finger pressure
`cull. Also, the addition of extra sensors adds to noise artifact
`and ditItculty in patient use. It is therefore an object of the
`present invention to provide an improvement over existing
`P'IT and PAT technology through a more economical and
`more easily used device without need of additional sensors.
`
`[0011] Several disclosures have been made in the prior art
`that teach methods and devices for diagnosis and monitoring
`of sleep breathing disorders using physiological data
`obtained from pulse oximetry-derivcd waveforms.
`
`[mm] us. Pat. No 5,398,682 to Lynn (Mar. 21. 1995)
`discloses a method and apparatus for the diagnosis of sleep
`apnea utilizing a single interface with a human body part.
`
`009
`
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`

`US 2tl04f005 9236 A1
`
`Mar. 25, 2004
`
`More specifically. a device is disclosed for diagnosing sleep
`apnea by identifying the desaturalion and resatut'ation events
`in oxygen saturation of a patient’s blood. The slope of the
`events is determined and compared against various infor—
`mation to determine sleep apnea.
`
`[0013] U.S. Pat. No. 6,363,270 B1 to Colla,et 31. (Mar. 26,
`2002) discloses a method and apparatus for monitoring the
`occurrence of apncic and hypopneic arousals utilizing sen-
`sors placed on a patient to obtain signals representative of at
`least two physiological variables, including blood oxygen
`concentration, and providing a means for recording the
`occurrence of arousals. Obtained signals pass through eon-
`ditioning circuitry and then processing circuitry, where
`correlation analysis is performed. A coincident change in at
`least
`two of the processed signals are indicative of the
`occurrence of an arousal that in turn indicates an apneic or
`hypopneic episode has occurred, A patient
`thus can be
`diagnosed as suffering conditions such as obstructive sleep
`apnea.
`
`[0014] U.S. Pat. No. 6,529,752 BZ to Krausman and Allen
`(Mar. 4, 2003) discloses a method and apparatus [or count-
`ing the number of sleep disordered breathing events expe-
`rienced by a subject within a specified time period. Such a
`counter comprises: (1) an oxygen saturation level sensor for
`location at a prescribed site on the subject, (2) art oximetry
`conditioning and control module that controls the operation
`of the sensor and converts its output data to oxygen satu-
`ration level data, (3) a miniature monitoring unit having a
`microprocessor, a memory device, a timer for use in time—
`stamping data, a display means and a recall switch, and (4)
`firmware for the unit
`that directs: (i) the sampling and
`temporary storage of the oxygen saturation level data, (ii)
`the unit to analyze using a specified method the temporarily
`stored data to identify and count
`the occurrence of the
`subject's disordered breathing events, and to store the time
`of occurrence of each of these events, and
`the display
`means to display specified information pertaining to the
`counts in response to the actuation of the recall switch.
`
`[0015] US. Pat. No. 6,580,944 Bl to Katz, et 3]. (Jun. 17",
`2003) discloses a method and apparatus for identifying the
`timing of the onset of and duration of an event characteristic
`of sleep breathing disorder while a patient is awake. Chaotic
`processing techniques analyze data concerning a cardiores-
`piratory function, such as oxygen saturation and nasal air
`flow. Excursions of the resulting signal beyond a threshold
`provide markets for delivering the average repetition rate for
`Such events that is useful in the diagnosis nf obstructed sleep
`apnea and other respiratory dysfunctions.
`[0016] The above references all make use of oxygen
`saturation data obtained through pulse oximetry to deter-
`mine arousals and/or sleep breathing disorders. Each nee—
`essarily requires additional analysis and calculation of blood
`oxygen concentrations in order to render information useful
`specifically in the diagnosis and monitoring of sleep breath-
`ing disorders. It is therefore another object of the present
`invention to provide a more simplified method ofobtainirtg
`and analyzing physiological data that accurately represents
`ANS activity.
`
`BRIEF SUMMARY OF THE INVENTION
`
`It is an object ofthe present invention to overcome
`[0017]
`one or more of the problems with the prior art.
`In one
`
`invention provides a
`the present
`preferred embodiment
`method and apparatus for improved monitoring of ANS
`activity using a single patient sensor.
`[0018] A variety of breathing disturbances may occur
`during sleep,
`including snoring, hypoventilation, apnea,
`increased upper-airway resistance, and asthma related con-
`ditions. This project proposes development of a novel device
`that can noninvasively and accurately detect frequent brief
`micro arousals that are not well identified by conventional
`airflow, respiratory eflort, pulse oximetry and EEG methods.
`These subeortical events result from increased respiratory
`effort and cause disruption of nocturnal sleep, leading to
`excessive daytime somnolence.
`
`[0019] Since microarousals have been associated with
`changes in autonomic system outllow, this invention pro-
`vides for a small, portable device that analyzes the shape of
`the arterial linger pulse, thereby detecting on a beat by heat
`basis changes in vascular
`tone directly attributable to
`microarousals. The present invention uses a photoptethys-
`mographically derived arterial blood volume waveform for
`monitoring changes in peripheral arterial Vascular tone, in
`conjunction with NI) converters and a mierocontroller for
`analyzing the morphology of the pulsatile signal.
`[0020] The method of the present invention provides for
`detection of microarousals that compares favorably with
`detection by pulse transit time (FTP) devices, EEG analysis,
`ECG analysis, esophagal pressure (Pes) or some combina—
`tion of these methods. Although FTP and peripheral arterial
`tonomctry (PAT) have both been receiving much attention as
`techniques for detecting changes in the ANS during sleep
`studies, PAT is relatively expensive and PTT has implemen-
`tation problems caused by motion artifact.
`
`is a further object of the present invention to
`it
`[0021]
`provide an apparatus that utilizes transmitted light intensity
`from an existing FDA approved pulse oximeter probe so that
`no additional device is attached to the patient. Valuable
`diagnostic information can then be extracted through elec-
`tronic procnssing of this existing data.
`
`[0022] Normalization is a method to correct for the pho-
`toplethysmographic pulse signal morphological changes
`based on finger position (as opposed to actual changes of
`autonomic activity.) FTP and PA'I‘ lack a means for signal
`normalization and therefor cannot correct for finger position
`changes. Normalization provides
`immunity to artifact
`caused by both elevation changes of the finger probe, and
`changes in blood liow due to arterial compression during
`patient positional changes. It is therefor another object of the
`present invention to provide a means of normalization in
`order to ensure appropriate artifact suppression.
`
`[0023] Since pulse oximeters use an alternating flashing of
`two difl'erent wavelength LEDs,
`the present
`invention is
`intended to synchronize with the desired LED in order to
`examine the transmitted intensity due to a single wave-
`length. Alternatively, certain models of oximeter OEM mod-
`ules provide an analog or digital output that can be utilized
`directly by the present invention.
`
`[0024] Another objective is to provide algorithms for
`slope detection, peak to peak height, and normalization may
`be performed either with firmware within the present inven-
`tion apparatus, or by software after the data is downloaded
`into a polysomnogtaph or other data processing device.
`
`010
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`

`US 2tl04f005 9236 A1
`
`Mar. 25, 2004
`
`DJ
`
`It is a funher objective of the present invention to
`[0025]
`provide a means of data storage and transfer, and to provide
`a method of displaying the observed changes in slope.
`Altemalive embodiments display these changes as a wave»
`form, light bars, and/or numerical information.
`
`BRIEF DESCRIPTION 0|T Tllll DRAWINGS
`
`1 shows a schematic representation of a
`[0026] FIG.
`typical pulse oximetcr sensing configuration on a finger.
`
`[002?] FIG. 2 shows a graphic representation of the
`components of vascular
`tissue that contribute to light
`absorption plotted as absorption versus time.
`[0028] FIG. 3 shows a graphic representation of a single
`peripheral pulse waveform plotted as volume versus time.
`[0029] FIG. 4 shows comparative physiological wave-
`forms following administration of vasoactive agents.
`[0030] FIG. 5 shows a second derivative waveform con-
`sisting of a, h, c and d waves in systole, and an e wave in
`diastole.
`
`[0031] FIG. 6 shows a graphic representation of changes
`in Non-natized Slope plotted as sIOpe ratio versus heart beats
`while subject performs Valsalva maneuver.
`[0032] FIG. 7 shows a sleep stage hypnogram of an hour
`and a quarter sleep study.
`
`[0033] FIG. 8 shows a block diagram of the present
`invention apparatus.
`
`[0034] FIG. 9 shows a block diagram of the present
`invention method.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`[0035] A variety of breathing disturbances may occur
`during sleep,
`including snoring, hypoventilation, apnea,
`increased upper-airway resistance, and asthma related con-
`ditions. The present invention discloses a method and appa-
`ratus that can noninvasiver and accurately detect [requcnt
`brief "nticroarousals" (small amplitude subconical distur~
`bances that disrupt normal sleep) that are not well identified
`by conventional airflow, respiratory etfort, pulse oximetry
`and EEG methods. These subcortical events result from
`increased respiratory elforl and cause disruption of nocturnal
`sleep, leading to excessive daytime somnolencc.
`[0036] Microarousals can be detected using data obtained
`from the absorbancc of visible or infrared light in a finger or
`other body pan of a patient. and by analyzing changes in the
`obtained peripheral blood volume waveform that are indica-
`tive of microarousals. Specifically, sulficient information is
`contained in slope variations of the rising edge of the
`pulsatile blood volume waveform to ailow analysis of
`changes in the autonomic nervous system (ANS). This
`technology is herein referred to as pulse transitional slope
`(P'I‘S). Both ANS and hemodynamic responses occur during
`obstructive sleep apnea and are influenced by apnea. hypop—
`nea, hypercapnea, and arousal.
`[0037] Analysis of the noninvasive blood pressure pulse
`wave has been shown to he Lawful for evaluation of vascular
`load and aging. Pressure transducers located at a palpable
`artery, such as the carotid, femoral. or radial artery provided
`
`a detailed waveform of pressure versus time. This continu-
`ous pulse wave tracing contains precise wavesbape, fre-
`quency. and inflection information easily discernablc by the
`human eye that
`is not available from only systolic and
`diastolic pressure numerics. Tnc progression from pressure
`transducers to photoplethysmography aIIDWS detection of
`the polar: wave at sites not easily palpated, including the
`finger and earlobe. Photoplethysrnography detects the
`changes in the amount of light absorbed by hemoglobin,
`which corresponds to changes in blood volume. Changes in
`amplitude of the photoplethysmographic wave have been
`used to evaluate arterial compliance, but the wave contour
`itself was not used, as is disclosed by the present invention.
`
`[0038] Plethysmography is the measurement of volume
`changes of tissue or an organ. Photoplethysmography mea-
`sures blood volume changes in a tissue using the fractional
`change in light transmission. One of the most common
`applications of this technology is the noninvasive measure—
`ment of the oxygen saturation of the hemoglobin in red
`blood cells through a technique called pulse oximetry. FIG.
`I shows a typical pulse oximeler sensing configuration on a
`finger. ‘lypicaily, two diflerent wavelengths of light (eg. 660
`and 805 nm) are applied to one side of a linger and the
`received intensity is detected on the opposite side after
`experiencing some absorption by the intervening vascular
`tissues. The amount of absorption (and conversely transmis-
`sion) is a function of the thickness, color. and structure of the
`skin, tissue, bone, blood. and other tissues that
`the light
`traverses.
`
`invention is specifically directed to
`[0039] The present
`alpha andrcnergic receptor sites.
`the activation of these
`receptors at certain locations on the body resulting in
`physiological responses such as peripheral vascular resis-
`tance, mydriasis, and contraction of pilomotor muscles,
`which are representative of sympathetic nervous system
`activity. The preferred locations generally include the fingers
`and the big toe (other sites are under investigation), due to
`a desirable lack of beta or parasympathetic receptors at those
`locations on the body.
`
`[004-0] The transmitting light comes from light emitting
`diodes (LEDs), typically in the visible red and the invisible
`infrared (IR) spectrums. The optical receiver may be a
`photodiode, photoresistor, or solar cell By using two dif-
`ferent wavelengths, each with different absorbance charac-
`teristics in oxygenated and deoxygenated blood, the inten-
`sity ratio between the two received signals can be analyzed,
`and not just the intensity. Therefore the attenuating tissues
`mentioned earlier do not affect the ratio of the intensities.
`which via a lookvup table can determine the oxygen satu~
`ration percent in the linger vasculatu re.
`
`[004l] FIG. 2 shows the components ofvasculature tissue
`that contribute to light absorption. The static or dc compo-
`nent ol‘the received optical signal represents light absorption
`by the tissue, venous blood, pigments and other structures.
`The present invention is concerned with the ac, or pulsatile
`component because the focus is on examining the wave
`shape of the systolic portion of the blood volume waveform.
`Electronically. the dc component is removed with a simple
`resistor-capacitor high pass circuit
`that has a —3 dB fre-
`quency of around one Hertz.
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`[0042] The amount of light passing through the finger is
`called transmittance, T, and is defined by:
`Effie;
`
`[0053] NTGsNiIroglycerin
`
`[0054] PTG-Photoplethysmography
`
`[0043] where 10 is the intensity of the incident light and l
`is the intensity of the transmitter! light.
`
`[0044] The amount of light of a specified wavelength
`absorbed by a substance is directly proportional to both the
`length ofthe light path and the concentration of the material
`within the light path. The absnrbance, A, is defined as the
`negative logarithm of the transmittance, or:
`A =7 log T=7 log fHG=tflCL
`
`[0045] where a is a constant called the extinction coeifi~
`cient and is dependent on the wavelength of the light passing
`through the substance and on the chemical nature of the
`Substance. C is the concentration of the substance and L is
`the path length of the absorbing material.
`
`[0046] The present invention makes use of just one of the
`wavelengths from the pulse oximeler probe, since the objec-
`tive is to observe only relative changes in the pulse wave
`shape, which in turn is derived from systolic blood volume
`changes in the finger. Since a pulse oximeter probe is part of
`all portable sleep diagnostic screening devices, it is a further
`object of the present invention to tap into the received light
`intensity signal of an existing probe, thereby alleviating the
`need for any additional patient sensors.
`
`[0047] FIG. 3 shows a typical peripheral pulse waveform
`Pulse height
`is the number of Ail] counts between the
`minimum and maximum exeursionsofcach pulse, while the
`slope is also calculated in AID counts for a fixed period of
`time beginning about 40 ms after a minimum is detected.
`
`[0048] The first and second derivative waveforms of the
`photoplethysmographic waveform have characteristic cort-
`tours, and the contour of the second derivative facilitates the
`interpretation of the original waves. The analysis of the
`second derivative of a fingertip photoplelhysmogram wave-
`form has been shown to be a good indicator of the sheets of
`vasoconstriction and vasodilation by vasoactive agents, as
`well as an index of left ventricular afterload as shown in
`FIGS. 4A, 4B and 4C.
`
`[004-9] FIGS. 4A, 4B and 4C show waveform tracings
`demonstrating the results of administration of vasoaclive
`agents. FIG. 4A shows the ECG parameter, FIG. 4B shoWs
`corresponding PTG and SDPTG waveforms. and FIG. 4C
`shows corresponding AoP and AoF waveforms. An increase
`in the late systolic component of aortic pressure (ADP) and
`PTO after intravenous injection of 2.5 mg AG? and a
`deepened d—wave in relation to the height of the a—wave
`(decreased dfs) are seen in SDPTG. On the olber hand, NI‘G
`produces marked reduction in late systolic components of
`aortic pressure and PTG, with d-vvaves becoming shallower
`in relation to the height of a wave (increased clfa). AoF
`indicates ascending aortic flow velocity. Augmentation
`index (Al) is defined as the ratio of the height of the late
`systolic peak to that of the early systolic peak, two compo-
`nents of the ascending aonic pressure at the anacrolic notcb.
`
`[0050] Selected Abbreviations and Acronyms
`
`[0051] AGT=Angiotensin
`
`[0052] AI-Augmentation Index
`
`[0055] SDl”l‘(j=Second Derivative Wave of Finger-
`tip Photoplelhysmography, where the a through (1
`components of the second derivative wave are
`described in FIG. 5. The second derivative wave-
`form consists of a, h, c, and d waves in systole and
`an e-wave in diastole.
`
`technology as
`slope (PTS)
`transitional
`Pulse
`[0056]
`applied in the present invention expands on this concept of
`using photOplethysmographically derived waveforms to
`assess changes in vascular tension, whether caused by
`apnacic obstruction or [he more subtle microarousals that are
`not delectable by cortical means. A normalized slope is
`calculated by dividing the height achieved during 40 ms of
`rise time by the maximum height of the pulse waveform
`(-height of late systolic peak). A normalized slope can be
`calculated in real time by a microprocessor controlled device
`as opposed to the post processing (analysis after recording)
`required by second derivative methods. This will allow use
`of the present
`invention technology in labs performing
`overnight polysomnograplt
`studies
`in addition to [he
`intended use for home sleep screening.
`
`[0057] Since vasoactive drugs have a distinct and predict-
`able afi’ect on the A] when measured by photoplethysmo—
`graphic methods, by extension the body’s own hormonal
`control of the arterial system shows comparable changes in
`the pulse waveform when measured using similar tech-
`niques.
`
`[0058] The present invention provides a portable, simple,
`and cost effective sleep diagnostic method and apparatus
`capable of detecting arousals and microarousals without
`adding EEG electrodes or additional patient sensors beyond
`those worn during a typical home study.
`
`[0059] Since microarousals have been associated with
`changes in autonomic system outflow, an object of the
`present invention is to provide a small, portable device that
`analyzes the shape of the arterial
`finger pulse,
`thereby
`detecting on a beat by beat basis changes in vascular tone
`directly attributable to microarousals. The present invention
`uses a photoplethysmographically derived arterial blood
`volume waveform for monitoring change in peripheral arte-
`rial vascular tone in conjunction with ND converters and a
`microcontroller for analyzing the morphology of the pulsa-
`tile Signal
`
`inven—
`[0060] Detection of microarousals by the present
`tion compares favorably with results achieved using pulse
`transit
`time (P'I'l') devices, EEG analysis, ECG analysis,
`esophagai pressure (Pes), and combinations of these meth-
`ods. Although P'l'l‘ and peripheral arterial tonometry (PM)
`have both been receiving much attention as [techniques for
`detecting changes in the ANS during sleep studies, PAT is
`relatively expensive and FTP has implementation problems
`caused by motion artifact.
`
`[0061] Eficacy of the present invention has been verified
`through monitoring of test subjects performing a “Valsalva
`Maneuver," which is the quickest and most dramatic method
`of producing ANS discharge—a resulting increase in intra-
`pulmonic pressure produced by forcible exhalation against
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`Mar. 25, 2004
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`the closed glottis. This produces a sympathetic discharge
`with subsequent vascular constriction.
`
`[0062] Atypical response to the Valsalva Maneuver is
`shown in FIG. 6. The normalized slope increases signifi—
`cantly, around 30% on the average which we postulate to be
`caused by increased rate of heart
`tissue conduction,
`increased contraction force, and increased rigidity in the
`arterioles. FIG. 6 shows changes in Normalized Slope
`produced by the present invention during a Valsalva Maneu-
`ver. The increase in ANS outflow begins around heart beat
`59, indicated by the sharp rise in the normalized slope of he
`putsatilc arteriole waveform.
`
`Further testing was conducted using daytime nap
`[0063]
`studies~Several short daytime nap studies were performed
`on sleep deprived volunteers for the purpose of scoring the
`sleep stages during these naps and looking for correlations
`between the stages and recorded normalized PTS slopes.
`None of the subjects were known to have sleep disordered
`breathing. volunteers were monitored with two central lobe
`electroencephalographic EEC: electrodes, two occipital EEG
`electrodes, two electrooculograrrt (BOG) electrodes, a chin
`electrode, a nasal air llow device, two respiratory airllow
`belts. and a PTS apparatus of the present invention, which
`provided a normalized slope value on a beat to beat basis.
`
`[0064] A typical recording of the normalized slope (on a
`scale of [l to tilt), where 100 is vertical) versus the sleep
`stages is shown in FIGS. 7A and 7B. The sleep stages were
`scored by a registered polysomnographic technologist
`(RI’SG’l') from the EEG, ECG, and respiratory waveforms.
`FIGS. 7A and 7B show a Sleep stage hypnogram of an hour
`and a quarter sleep study. FIG. 7A shows sleep ratio
`percentages through the duration of the study. FIG. TB
`shows a graph that has been scored from EEG. BOG. and
`respiratory wavefonns according to the sleep scoring cort-
`vention of the American Sleep Academy. Point A is the
`beginning of sta