O
`Umted States Patent
`
`[19]
`
`Diab et al.
`
`U8005632272A
`
`[11] Patent Number:
`
`5,632,272
`
`[45] Date of Patent:
`
`May 27, 1997
`
`[54]
`
`[75]
`
`[73]
`
`[21]
`
`[22]
`
`[63]
`
`[5 1]
`[52]
`[5 8]
`
`[5 6]
`
`SIGNAL PROCESSING APPARATUS
`’
`Inventors: Mohamed K. Diab; Esmaiel
`Kiani-Azarbayjany; Ibrahim M.
`Elfadel, all of Laguna Niguel; Rex J.
`McCarthy, Mission Viejo; Walter M.
`.
`Weber, Los Angeles; Robert A. Smlth,
`.
`(30191143111 0f Cahf-
`.
`.
`Ass1gnee: Masrmo Corporation, Mission Viejo,
`Calif.
`
`.
`
`9/1989 Stone et a1.
`4,369,254
`11/1989 Hausman .
`4,883,353
`1/1990 Cheung 6t 81 .
`4,892,101
`3/1990 Muz .
`4,907,594
`$1333 Egrenmaglet 31’ '
`2932’;ng
`ga 6t
`'
`'
`’
`’
`5/1990 Goodman et a1.
`.
`4,928,692
`8/1990 Lehman .
`4,948,248
`9/1990 Hall.
`4,955,379
`9/1990 Zurek et a].
`4,956,867
`.
`10/1991 Hirao et a1.
`5,057,695
`.
`5,273,036 12/1993 Kronberg et a1.
`5,458,128
`10/1995 Polanyi et a1. ...................... 128/633 X
`
`.
`
`APPI- No“ 320,154
`
`Ffled:
`
`OCt’ 7’ 1994
`Related US. Application Data
`
`Continuation-impart of Ser. No. 132,812, Oct. 6, 1993, Pat.
`No. 5,490,505, and a continuation-in—part of Ser. No. 249,
`2122;193:3égr6fi29‘61’61g‘36g‘342’r4g2igggiwggfld::edonunu-
`'
`’
`’
`'
`’
`’
`'
`'
`
`Int. Cl.6 ............. A61B 5/00
`US. Cl. ............................................. 128/633; 128/666
`Field of Search ..................................... 128/633-634,
`128/664—667, 672. 687—688, 716; 356/39—41
`
`References Cited
`
`OTHER PUBLICATIONS
`
`Rabiner, Lawrence et a1. Theory and Application of Digital
`Slgnal Procesfmg’ p. 260’ 1975'_
`_
`Tremper, Kevm et al., Advances tn Oxygen Monitoring, pp.
`137-151 1937-
`Harris, Fred et 31., “Digital Signal Processing with Eflicient
`Polyphase Recursive All—Pass Filters”, Presented at Inter-
`national Conference on Signal Processing, Florence, Italy,
`Sep. 4—6, 1991, 6 pages.
`t
`d
`(L' t
`t'
`15 C0“ ““16 0“ “X Page“)
`Primary Examiner—Angela D. Sykes
`Attorney, Agent, or Firm—Knobbe, Martens, Olson & Bear,
`LLP.
`
`US. PATENT DOCUMENTS
`
`[57]
`
`ABSTRACT
`
`‘
`
`‘
`
`.
`
`3/1972 Lavallee -
`3,647,299
`3,704,705 12/1972 HCICZfeld Ct 3L -
`4882915 15/137;
`iwfeneyf a1
`4’095’117
`6/1978 N: Sky 8
`4’407’290
`10/1983 Wider '
`4:537:200
`3,1935 Wldrow ‘
`4,649,505
`3/1937 Zinger, J1-_ et a1.
`4,773,422
`9/1988 Isaacson et a1.
`.
`4,799,493
`1/1989 DeFault .
`4,800,495
`1/1989 Snflth -
`-
`$23,321)?
`7/1333 £11013 ‘3; 31-
`,
`,
`oo ,
`r.
`,
`.
`4,860,759
`8/1989 Kahn et a1.
`4,863,265
`9/1989 Flower et a1.
`4,867,571
`9/1989 Flick et a1.
`.
`4,869,253
`9/1989 Craig, Jr. et al.
`
`.
`
`.
`
`The present invention involves method and apparatus for
`analyzing two measured signals that are modeled as con-
`taining primary and secondary portions. Coefficients relate
`the two signals according to a model defined in accordance
`with the present invention. In one embodiment, the present
`invention involves utilizing a transformation which evalu-
`ates a plurality of possible signal coefficients in order to find
`appropriate coefficients. Alternatively, the present invention
`involves using statistical functions or Fourier transform and
`windowing techniques to determine the coefficients relating
`to two measured signals. Use of this invention is described
`.
`.
`.
`.
`.
`_
`:11cplaittcular detail With respect to blood oxrmetry measure
`'
`
`23 Claims, 37 Drawing Sheets
`
`/./5t7p
`
`r ————————————— n
`,1 _ _ _ _ gemsoa
`_
`
`_ ,
`
`,/"..e.0
`
`/
`
`I
`I
`*Am CONTROL
`V/OFFV
`- V4
`5.55 \
`
`_/’.5L7/
`I
`it”
`’
`/
`//// ”J
`\\
`//‘§\/‘5”L7 , TEL?
`: “7‘30
`
`y,"
`l
`\\
`~44 \~.
`.
`1‘
`‘
`\\
`
`
`I"- J/
`I
`FRONT £an
`06 T
`
`
`
`
`
`
`
`ANISTEITAL 0
`I
`/ m? /
`ANALOG
`worm. SIGNAL PROCESSING HEART RATE
`0,5,“,
`L
`
`
`
`
`
`
`COr‘ISUT'l’lt/J‘NING
`CONVERSION
`AND SIGNAL EXTRACTION
`/
`..
`..
`PLETHYSMOGRAF‘HIC
`:
`
`
`'4
`i
`WAVEFORM
`
`
`
`
`
`DIGITAL TO
`EMITTER CURRENT
`
` ANALOG
`
`DRIVERS
`
`EMITTER CURRENT
`
`CON VERSION
`
`CONTROL
`
`"1
`
`
`
`APPLE 1007
`
`1
`
`APPLE 1007
`
`

`

`5,632,272
`Page 2
`
`OTHER PUBLICATIONS
`
`Haykin, Simon, Adaptive Filter Theory, Prentice Hall,
`Englewood Cliffs, NJ, 1985.
`Widrow, Bernard. Adaptive Signal Processing, Prentice
`Hall, Englewood Cliffs, NJ 1985.
`Brown, David P., “Evaluation of Pulse Oximeters using
`Theoretical Models and Experimental Studies”, Master’s
`thesis. University of Washington. Nov. 25, 1987, pp. 1—142.
`Cohen, Amon. “Volume I Time and Frequency Domains
`Analysis”, Biomedical Signal Processing, CRC Press, Inc,
`jBoca Raton, Florida, pp. 152—159.
`Severinghaus, J.W., “Pulse Oximetry Uses and Limitations”,
`pp. 1—4, ASA Convention. New Orleans, 1989.
`
`Mook, G.A., et al., “Spectrophotometirc determination of
`Oxygen saturation of blood independent of the presence of
`indocyanine green”, Cardiovascular Research, vol. 13, pp.
`233—237, 1979.
`Neuman, Michael R., “Pulse Oximetry: Physical Principles,
`Technical Realization and Present Limitations”, Continuous
`Transcutaneous Monitoring, Plenum Press, New York,
`1987, pp. 135—144.
`Mook, G.A.. et a1., “Wavelength dependency of the spec-
`trophotometric determination of blood oxygen saturation”,
`Clinical Chemistry Acta, Vol. 26, pp. 170—173, 1969.
`Klimasauskas, Casey, “Neural Nets and Noise Filtering”, Dr.
`Dobb’s Journal, Jan. 1989, p. 32.
`Melnikof, S. “Neural Networks for Signal Processing: A
`Case Study”, Dr Dobbs Journal, Jan. 1989. pp. 36—37.
`
`2
`
`

`

`US. Patent
`
`May 27, 1997
`
`_
`
`Sheet 1 of 37
`
`5,632,272
`
`1
`
`F/G./
`
`
`
`BONE
`MUSCLE
`
`TISSUE
`
`ARTERIAL BLOOD
`
`VENOUS BLOOD
`
`
`FIG. 2
`
`
`
`3
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 2 of 37
`
`5,632,272
`
`21%
`
`24b
`
` DISPLAY
`
`CORRELATION
`
`sXaU’)
`
`CANCELER
`
`
`
`FIG. 4a
`
`4
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 3 of 37
`
`5,632,272
`
`22b
`
`24b
`
` DlSPLAY
`
`CORRELATION
`
`
`
`FIG. 4b
`
`CANCELER
`
`“151(1)
`
`
`
`
`5
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 4 of 37
`
`5,632,272
`
`sgam 0R 5ng
`
`Jé’\
`
`Sxé”=s>\é”+ nxam
`
`0R
`Smgths M?) + nAbm
`
`ngét) 0R ngbm
`
`
`
`S'(’£)
`
`FIG. 5b
`
`6
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 5 of 37
`
`5,632,272
`
`
`
`‘TRANSFERFUNCHON
`
`FREQUENCY(f)
`
`F7C145<2
`
`7
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 6 of 37
`
`5,632,272
`
`
`
`FIG. 6a
`
`31
`
`'
`
`
`
`[110
`
`(42
`
`A2A2 A2 A2 A2 A2A2
`A A A A A .A A
`A4A4 A4 A4 A4 A4A4
`
`A6
`A6 ‘6 ‘
`
`
`
`
`
`
`
`
`
`
`
`
`- AA A A A AA
`A2A2 A2 A2 A2 A2A2
`A
`A
`A A A
`3A3 1A4 A:
`3A:
`A5 A5 A6
`A6 6 ‘6
`A6
`A5 A5 A6 As
`An An An An An AnAn
`FIG. 5c
`U1
`
`
`
`
`8
`
`

`

`U.S.
`
`Patent
`
`May 27, 1997
`
`Sheet 7 of 37
`
`95
`
`632,272
`
`232mmhxu
`
`mokowhmo
`
`mOquOMHZ
`
`mwmdfiom
`
`mmjmoz<o
`
`ZOF<.E~EOO
`
`NW
`
`UK6?.
`
`38:?I395+322.3:39$u3.mE3&5:xESQ138$;
`133mu3.;E Eflm32m
`
`
`
`38:?“I32E+$Vn<mfi1€2mn3&2E.O
`
`9
`
`
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 8 of 37
`
`5,632,272
`
`r10.0
`
`r9
`
`FIG.7b
`
`SIGNAL
`
`COEFFICIENTS
`
`RELATlVE CORRELATION CANCELER
`ENERGY OUTPUT
`
`10
`
`10
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 9 of 37
`
`5,632,272
`
`U')
`'2
`
`EU E t
`
`:
`o(J
`._l
`<L'
`Z
`9U)
`
`O
`
`- sf
`
`_ d”
`
`0 _ :1”
`
`K5 — 9“
`LT.
`
`(D
`— 9
`
`— d”
`
`— sf
`
`— sf“
`
`:::-**N
`
`:5
`
`
`
`
`<
`
`~____._.._..______________.__J
`
`RELATIVE CORRELATION CANCELER
`ENERGY OUTPUT
`
`11
`
`11
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 10 of 37
`
`5,632,272
`
`LEAST SQUARES LATTICE
`PREDICTOR
`
`REGRESSION
`FILTER
`
`L0
`
`5E«a
`
`59?Shape
`
`mm{\
`
`mufiwmExmz
`
`OB
`
`‘11
`
`
`
`ommN
`
`mesa
`
`m.0:
`
`12
`
`12
`
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 1170f 37
`
`5,632,272
`
`QRD— LSL PREDICATOR
`
`QRD— LSL FILTER
`
`om<3xo<m
`
`mzmlmzfioo
`
`KMFDQEOQ
`
`Qm<3xo<m
`
`mZmlmzfiOo
`
`mmHDQEOQ
`
`OD.
`
`.0.
`
`om<§mou
`
`mZmIMZMOo
`
`mmHDQEOo
`
`Dm<§xo<m
`
`mZmleEOO
`
`KMFDQEOQ
`
`Qm<§xo<m
`
`mZmlszOQ
`
`mmhnafioo
`
`2-221..
`
`8%wtIs
`
`Qm<§m0u
`
`mzmlmZmOO
`
`mmHDQEOQ
`
`
`
`38w
`
`12m
`
`3%Eb
`
`13
`
`13
`
`
`
`
`
`
`
`
`
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 12 of 37
`
`5,632,272
`
`INITIALIZE NOISE
`CANCELLER
`
`Lfi?
`
`L59
`
`TTME UPDATE
`OF [i4] ELEMENTS
`
`INPUT NEW SAMPLES
`[SAa(0 AND SAbU)]
`
`[n'(0 or S'O)]
`CALCULATE REFERENCE
`FOR TWO MEASURED SIGNAL
`
`SAMPLES
`
`MU
`
`ZERO- STAGE
`UPDATE
`
`/70
`
`
`ORDER UPDATE
`m“‘——STAGE OF
`
`
`LmSL— PREDICTOR
`hfl7
`
` I
`
`ORDER UPDATE
`th—STAGE OF
`REGREsaoN
`TTLTER(S)
`m=m+1
`
`/90
`
`NO
`
`YES
`CALCULATE
`OUTPUT
`
`25v
`
`2mg
`
`14
`
`FIG.9
`
`14
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 13 of 37
`
`5,632,272
`
`1200
`
`INITIALIZE NOISE
`CANCELLER
`
`INPUT NEW SAMPLES
`[3mm AND 37mm]
`
`£300
`
`TIME UPDATE
`OF [2“] ELEMENTS
`
`[n' (+) or s' (1)]
`CALCULATE REFERENCE
`FOR TWO MEASURED SIGNAL
`SAMPLES
`
`1'400
`
`ZERO—STAGE
`UPDATE
`
`1500
`
`1500
`
`
`
`
`ORDER UPDATE
`nTh—STACE 0F
`
`QRD-LSL-PREDICTOR
`
`
`
`
`
`
`
`ORDER UPDATE
`mfh-STAGE OF
`QRD—LSL
`FILTER(S)
`m = m +
`
`1
`
`YES
`
`200 0
`
`CALCULATE
`OUTPUT
`
`2/00
`
`T0 DISPLAY
`
`F/G.9a
`
`15
`
`15
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 14 of 37
`
`5,632,272
`
`LEAST SQURES LATTICE
`PREDICTOR
`
`REGRESSION
`FILTER
`
`REGRESSION
`FILTER
`
`§QLI
`
`mmm:.eameso
`
`Asa<éw
`
`nMw:.F:mhao
`
`murk\\
`
`GEN
`
`mofim
`
`96t
`
`I‘|IIIIII|
`
`mwfirmExmz
`
`Oh.
`
`16
`
`16
`
`
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 15 of 37
`
`5,632,272
`
`QRD~ LSL PREDICATOR
`
`FILTER 1
`
`FILTER 2
`
`
`
`17
`
`17
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 16 of 37
`
`5,632,272
`
`
`
`ZOF<mDH<mzwuxrxo
`
`58%;
`
`mmN\
`\
`
`/.QMJMJVMM;\
`
`MNW\\
`
`><.Em_ou._.<m.Efirozfimmoomn..220645.90
`
`
`
`
`
`
`
`oin<mooz§x$dzo=b<Exu._<zo_moz<
`\QMJ_49:282.5____r.llllllllllllllllllllu.
`flH__........l0220:5200_mm:m8_zommmSzooom_#505in._mokomhaWSW_Eooéz<
`.oo<z<__‘ozmHzoE"lllllllmmtim8m_/__WNW;
`
`QMMJ_QNM.\QxMJK
`
`
`
`
`memzmm\QQM\
`
`\\“wt
`
`
`
`Hzmmmao”GEL—2m
`
`Aom‘rzoo
`
`
`
`zowwfiaEgg9.255pzummao3E5
`
`18
`
`18
`
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 17 of 37
`
`5,632,272
`
`“ISM:
`
`
`
`Txx“wt
`
`MN.“NW»)
`
`10.2410::
`
`\NMJ
`
`18.44
`
`\MJMJ
`
`Hzmmmao
`
`JOWFZOQ
`
`mmktim
`
`NWM;
`
`mo<HI_O>
`
`mozmmmumm
`
`19
`
`19
`
`
`
`

`

`US. Patent
`
`Blay 27,1997
`
`Sheet 18 of 37
`
`5,632,272
`
`
`
`<H<QNILON
`meoz:mof
`
`Ema0:4
`o\<ozi<xm
`
`mamaohv
`
`mMme>zoo
`
`o\<:mm_
`
`awkmm>zoo
`
`
`
`
`
`mmoymHumz<o
`
`
`
`l/J‘MJVM.“V‘MJ
`
`>>O._
`
`mm<m
`
`mmhlzu
`
`E<moomm
`
`mmijn§<mmfija2<
`
`
`
`Z_<oImam
`
`
`
`mtmOQEOo
`
`._<Zo_m
`
`20
`
`20
`
`
`
`
`
`
`
`

`

`US. Patent
`
`m
`
`5,632,272
`
`VMM;I.\\
`
`\\\\NIXON
`
`mMJa§<m
`
`mmn
`
`NJa2<m
`
`y2<moomammummnm
`
`n,>m02m2
`
`
`
`7<._.<m_/%%N)
`
`>m02m2
`
`
`
`MJomkzoo220mNMx
`
`J\WUKMJMV«rQBMJ
`
`
`o<mm>m02m2m§Mm>420
`fiJomkzoo‘\\\wHzmmmsommbtgm
`
`o<4¢/Fz_
`
`
`
`2<zmMme
`
`21
`
`
`
`
`
`mmmhmémm
`
`MR6Q
`
`mxn2200FmOQ4<Emm
`
`mmqqomhzooomoi
`
`21
`
`
`
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 20 of 37
`
`5,632,272
`
`IQ<mOO§m>IquamtqmmMISQ
`
`Spam
`
`
`
`mmADQZO_._.<.504<0
`
`ZmoerOZOF<KDH<M
`
`
`
`zop<m3<m292535.
`
`zMwwW2mEmz<E
`
`zo:<m2<m
`
`\
`
`%QV\V\msw\\
`
`
`
`
`
`Vx“wt
`
`22
`
`VQV
`
`NQW
`
`Qhwf\
`\\
`
`w
`
`8.5.35
`NImNm
`ZO_H<_>__0H._Q
`NImN©
`
`ZQCEDQOEMQ
`
`noo<20mmv
`
`NIXON
`
`22
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 21 of 37
`
`5,632,272
`
`QQV\\
`\
`
`NImmm._.<0mgg
`
`NImmmH<QmmEEV¥V
`
`mNMJV
`
`mmd2<mv53a:23m8%
`
`QWVWNW
`
`
`
`2%?22%?
`
`
`
`“whiz/aN3._<zo_‘m853382
`
`
`
`EmaziomgEm_m2<+8m
`
`
`
`84%,;w53n5Em8m8238:
`
`
`
`
`
`yawx?)mm»x336NIXONEBalsam¢53a:23m2292E3
`
`23
`
`VVVI
`
`mmjaszmw53a:23m59%?
`
`mfiw/«MNV\\5W».
`
`F0M4mm
`
`23
`
`
`

`

`US. Patent
`
`hday 27,1997
`
`Sheet 22 of 37
`
`5,632,272
`
`
`
`AN:m.mmv
`
`
`
`Amm4m2<monmv
`
`Hoxma<zmomm<mlz
`
`
`mmuusmFDQFDO
`ZO_._.<_>__omo
`
`mmpgmmm<m304a;
`
`4mzz<xoQmm<mmzfl
`
`0.2>m
`
`%\“wt
`
`Amm;m:<mumv
`
`ANImNmV
`
`
`
`Hozma<zm0mm
`
`AN:m&©v
`
`
`
`mmuuamPaapoo
`
`
`
`Amm4a2<monmv
`
`ZO_H<§_omo
`
`or%m
`
`
`
`mmPJEmm<a304a:
`
`Amm4a2<mm_mv
`
`
`
`4mzz<zoomm
`
`ANImNmV
`
`QQV
`
`.QhV
`
`NWV
`
`24
`
`%m.v.\\
`
`wa
`
`QMV
`
`% R
`
`24
`
`
`
`
`
`
`
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 23 of 37
`
`5,632,272
`
`wQ¥‘\
`
`mm3n=2<m
`
`m:.:.n5v55
`ON?53AmmdgmORV
`nim—0<Qmmmkgi
`mm<moz<m
`omm<mmz_
`
`KEHE
`
`
`
`SWEEZBag;Emma/22mBm<EZ
`
`
`4<>%Q2mm03AmmEsZmown.N:33
`
`/1WWWRafi
`
`(V%WIQWV
`
`Vm.|\
`
`me‘
`
`mme§<m
`
`0mm
`
`KNEE
`
`.QnQV/
`
`NQm,
`
`Gum
`
`0mm4<>O§mm00400
`
`va\
`
`VQIQ
`
`Sxma<zmEm
`
`
`
`m9>_omo_>_o
`
`mgno
`
`19$mo;{VNM
`
`
`
`ZO_._.<._m_mmOo
`
`Gum/«mug
`
`mfim
`
`25
`
`MIHn5x05
`ON~Hm<u_Ammfizflxm33
`BEo<8E5:
`
`mm<n52<m
`
`
`
`ZO_._.<.w_3.r<mQmwm
`
`ZOF<DOmZO_H<KD._.<m
`
`mmomommomo
`1'11...mfimomm
` ZO_._.<:_m_mw_OOZO_._.<N:.:.<mOH Ammfiszm0%a:mag
`NV2:582
`
`
`
`0OPZ_mth_
`
`#58:38miSmmwhm58mmzfimin.0mm
`
`
`
`mammz_\mzoimazm8mmz_m
`
`Sm\NQ29238zoEEDZm
`
`Io<mmomWNW;
`
`
`
`
`
`ME208mg;8mg;
`
`
`
`ZOF<4mmmOo
`29:3”.de
`
`mmomo
`
`$0525N\“WE
`
`25
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 24 of 37
`
`5,632,272
`
`O._.
`
`ZOF<KDH<W
`
`Eltmoouz
`
`
`
`
`
`mMFm<2mozmmmmmm
`
`
`
`mwmwwgupgumoh<mmzwo
`
`
`
`/.Qh..fl\
`
`zO_._.<m3H<m
`
`ZOF<DOm
`
`QM“.
`
`
`
`
`
`z<omm§<zoc<m2P<m
`
`20mmmm34<>n__v
`
`Acme?ohmew
`
`
`
`.mMJa2<monmv
`AN:mam
`
`Qmm<mmz_
`
`
`
`.mMJa2<mcmmv
`AN:mam
`
`0mm
`
`26
`
`
`
`
`
`
`
`mm<¢204///x
`
`._.Z_Ow
`
`mmmoomm
`
`mOH<S=Hmm
`
`WVM.
`
`
`
`mozmmlz_2§?/m._u_m_oOmmmEDZ
`.AN‘<Qm§<4I
`
`
`
`mm<moz<m
`
`mmFJE
`
`00
`
`4<>O§mm
`
`26
`
`
`
`
`
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 25 of 37
`
`5,632,272
`
`Pomfimm
`
`OZ_IHOO_2m
`
`KNEE
`
`IQ:
`
`mozmoizoo
`
`Hmmz.
`
`WK“wt
`
`WWW
`
`QZ<QEQ
`
`IHOOEm
`
`WQV\\
`
`ZOP<mDH<m
`
`2mo>xo
`
`ZOPnEOxm
`
`OZZQZ<I
`
`
`
`Oz_\ru.__._<30z_m
`
`0604
`
`Z_mmFDQEOQ
`
`mmHDmECk
`
`
`
`
`
`mm>m30mmgomZ_m_
`
`
`
`mofimVF/fimZ_m_
`
`27
`
`27
`
`
`
`
`
`
`
`

`

`US. Patent
`
`Dday 27,1997
`
`Sheet 26 of 37
`
`5,632,272
`
`HK<MI
`
`
`
`IaéodngEEzfid
`
`2m0um><>>
`
`
`
`
`
`KMHJEHDQHDO
`
`‘mumoo
`
`
`
`WDH<HmZOFOE
`
`EN@\I.\
`
`
`
`3<mzamkomam4<mbomam
`
`ZOPOE
`
`H0<¢Fm<
`
`zofimmmaam
`
`
`
`.mMJa:<monmv
`
`hoImQ<zm
`
`AN:m.um
`
`0mm
`
`ZOFKDF<m
`
`
`
`Amu>msommgou
`
`:5?Vin.
`
`EmEomuv
`
`mo<mm><
`
`28
`
`FDQHDO
`
`KMEJE
`
`mh<mmw<m
`
`
`
`02:22:wh<mhm<mx
`
`m5>4<2<ZO?<§Pmm
`
`.Qmm.
`
`mme‘
`
`Q\VI\\
`
`4<mkomam
`
`ZOF<§me
`
`00
`
`Qz<4<>02mm
`
`mm<aoz<m
`
`mMFJE
`
`
`
`.mmJuz<monmv
`
`
`
`AN:m.mm
`
`Hoxmm<zm
`
`omm<muz_
`
`28
`
`
`
`
`
`
`
`
`

`

`
`
`QWIQV\\
`
`R‘Rm
`
`rIIIIIIIIIwII\11111_
`
`no59223
`
`7_9no;nwm2u2<moncv1__7,SEEMS;E5:
`mommuxzzM_mime
`
`
`mmmooma_FW5.9.”622:8Emzfi225:0mm<n§3
`
`___
`
`ww<uoz<m
`
`awkgm
`
`0o
`
`A<>Ozmm
`
`US. Patent
`
`2
`
`73
`
`5,632,272
`
`t_flllllllllllllllllllllhI:S__
`
`nm_7_
`
`__
`
`m02mmmumm
`
`mOF<mm2mo
`
`\mmunm
`
`\\z
`ZO§<DGm
`OF<mDH<m
`
`
`
`20:53:;.2352
`
`zop<m2<m20x“:
`
`“292535
`
`‘mnjatém0an
`
`RN...mam
`
`SEE;
`
`.mflazfione
`
`Q...0%
`
`Sm
`
`29
`
`29
`
`
`
`
`
`

`

`US. Patent
`
`3f
`
`5,632,272
`
`
`
`7,58%;ES:
`
` ”622:82z<md$5.26..880%£623_IIIm.H261«523mz_2_M«NM\\wjuo_nommmzaz.
`
`R?A..2
`
`N58.
`
`
`
`
`
`
` _73..mam9ES:,mmfiszmone9_mméozéSWEEE
`
`7.lsl.l
`
`
`
`
`
`bxm.“QR
`
`at.
`
`
`
`zopéaqm.2522
`
`zo;<m3<m28$
`
`“20.2385
`
`
`
`tQMw,AN:0%mm‘mflaim0an
`020.238%\zoEmDEm
`:2_Eu2%:2_£5moEmmEo8m_mozfimbm
`
`
`
`30
`
`
`
`30
`
`
`
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 29 of 37
`
`5,632,272
`
`9:
`
`___________.__,__;_
`:___:__1.______
`I3
`
`.—._____
`
`_
`
`_____A_i___
`
`%h.h.
`
`___
`
`
`
`mm3<>z<omzoF<m3H<m
`
`.:=__2___u_
` IIIIIIIIIIIIIIIIIIIIIF11\\‘\j‘...}Ix|lllll_..llll:‘___2m_A,,,
`
`mummmm
`..........................................
`
`‘lll||‘\}lal|).
`
`mv
`
`o;
`
`wd
`
`,m6
`
`To
`
`Nd
`
`OUTPUT ENERGY
`
`31
`
`31
`
`
`
`
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 30 of 37
`
`5,632,272
`
`ZO_H<mD._.<mOH
`
`mZOP<nSOJ<O
`
`§<mOOHm_I
`
`ZOF<mD._.<m
`
`ZO_._.<DOm_
`
`QN.©\
`
`Q\.Q\
`
`IIIIIIIIIIIIIJ
`
`\smm\\
`
` \
`
`rv_2<mKNEE
`
`2m!sz{.mmlm..EIO
`
`Qmm<muz_
`
`VQrQ
`
`
`
`fl7f3.le2...filo
`
`Nxz<mES:
`
`0mm
`
`(\QQK
`
`
`
`32
`
`32
`
`
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 31 of 37
`
`5,632,272
`
`105
`
`VALUES
`
`SATURATION
`
`NUMBER OF OCCURENCES 7
`
`33
`
`33
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 32 of 37
`
`5,632,272
`
`zo_._.<m3.r<m
`
`Zmo>xo
`
`QMJQ
`
`Fm<u
`
`
`zop<mak<mNImNm
` ZO_H<_2_Om_Q
`
`Z<m_._o
`
`Ia<m002m>IHw4u
`\2m0um2<mH
`wk<mmmJDQ
`
`mil—3Q
`
`midi
`
`zop<4304<o
`
`TMW
`
`Nut
`
`zDfiafiSoOEmo
`
`Aoo<zomuv
`
`NIXON
`
`34
`
`34
`
`
`
`
`
`
`

`

`US. Patent
`
`7
`
`3
`
`3
`
`5,632,272
`
`Wm“.
`
`%V%
`
`hxxbVVQ
`
`QV%
`
`ZOF<4304<0
`
`mmISu9.
`
`
`
`
`
`90.95%
`
`
`
`Eu...20:02:...
`
`“3.52%
`
`N5
`
`XMJQEOO3002.;
`
`0mm:o<ommmpqi
`oum<muz_
`
`a...
`
`mmhgu
`
`omm<muz_
`
`oo
`
`4<>02mm
`
`8m<Ez_
`
`03
`
`”855%mam.NI0%;
`
`menzzmREE;
`
`
`
`Mhm/,Hoflmmxmfizoo3002.;8m3SEE:0mm0mm
`
`,mmm{New755mm2hugMW\wmm
`WI//1//
`
`
`
`
`
`Eh.20:02.:maniaEv5%:._<>%%mm
`
`oo._Ammdimmom.NT.38
`BaHoxmnzzm8m
`
`
`
`cmmoat20<2QJOImMKI...
`
`
`
`7mmm\Nmmmum
`
`
`3\m3»qrw(6SEE;292:8
`non“BEzoimnim
`
`ka\\PG
`
`
`
`
`8323:SozwmmE
`
`
`
`mw<Ia
`
`040:9..th
`
`mumw
`
`“wt
`
`
`zmfimwflmmzoz<¥fi<m
`83mm:35?
`
`N%%
`
`35
`
`35
`
`
`
`
`
`
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 34 of 37
`
`5,632,272
`
`
`
`Ia<m00§m>lhm4aZ<mqo
`
`wh<mmmqam
`
`GEN
`
`EDmhomam SQ
`
`mfiyg<z<
`
`300E;
`
`ZOFOZDm
`
`
`
`ZOF<KDH<W4<thm<
`
`Hum20mm
`
`mmmm>z_
`
`30mg?
`
`ZOFOZDm
`
`SEN
`
`36
`
`36
`
`
`
`
`
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 35 of 37
`
`5,632,272
`
`I
`
`250
`
`~75"
`
`25”
`
`Sxau) = SAred(t)
`
` I
`
`27
`C
`
`be(t)=s>\IR(t)
`
`”a
`
`27.5
`
`
`
`37
`
`37
`
`

`

`US. Patent
`
`May 27, 1997
`
`Sheet 36 of 37
`
`5,632,272
`
`290
`a
`
`291;
`a
`
`I
`I 29c
`1
`7
`
`f
`
`Siam = S’iredfi)
`
`FIG. 29
`
`t
`
`II
`(t)=SAIR(t)
`
`t
`
`IJOC‘
`II
`a / Ab
`
`S
`
`I 300
`I1
`
`Jab
`I;
`
`W \ ‘
`
`FIG. 30
`
`38
`
`38
`
`

`

`US. Patent
`
`May 27
`
`, 1997
`
`Sheet 37 of 37
`
`5,632,272
`
`00m
`
`“mEL3m>0>>
`
`W22:35
`
`855:5 WmEmotEoucoo
`
`ouotoofi08
`
`39
`
`R.6?.
`
`39
`
`

`

`5,632,272
`
`1
`SIGNAL PROCESSING APPARATUS
`
`Reference to Prior Related Application
`This is a continuation-in—part application of US. patent
`application Ser. No. 08/132,812 filed Oct. 6, 1993, and
`entitled “Signal Processing Apparatus” now US. Pat. No.
`5,490,505 and a continuation-in—part application of U.S.
`patent application Ser. No. 08/249,690 filed May 26, 1994
`entitled “Signal Processing Apparatus and Method”, now U.
`S. Pat. No. 5.482.036 which is a continuation of US. patent
`application Ser. No. 07/666,060 filed Mar. 7, 1991, now
`abandoned.
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`
`The present invention relates to the field of signal pro—
`cessing. More specifically, the present invention relates to
`the processing of measured signals, containing a primary
`signal portion and a secondary signal portion, for the
`removal or derivation of either the primary or secondary
`signal portion when little is known about either of these
`components. More particularly, the present invention relates
`to modeling the measured signals in a novel way which
`facilitates minimizing the correlation between the primary
`signal portion and the secondary signal portion in order to
`produce a primary and/or secondary signal. The present
`invention is especially useful for physiological monitoring
`systems including blood oxygen saturation systems.
`2. Description of the Related Art
`Signal processors are typically employed to remove or
`derive either the primary or secondary signal portion from a
`composite measured signal including a primary signal por-
`tion and a secondary signal portion. For example, a com—
`posite signal may contain noise and desirable portions. Ifthe
`secondary signal portion occupies a different frequency
`spectrum than the primary signal portion, then conventional
`filtering techniques such as low pass, band pass, and high
`pass filtering are available to remove or derive either the
`primary or the secondary signal portion from the total signal.
`Fixed single or multiple notch filters could also be employed
`if the primary and/or secondary signal portion(s) exist at a
`fixed frequency(s).
`It is often the case that an overlap in frequency spectrum
`between the primary and secondary signal portions exists.
`Complicating matters further. the statistical properties of one
`or both of the primary and secondary signal portions change
`with time. In such cases, conventional filtering techniques
`are ineffective in extracting either the primary or secondary
`signal. If, however. a description of either the primary or
`secondary signal portion can be derived, correlation
`canceling, such as adaptive noise canceling, can be
`employed to remove either the primary or secondary signal
`portion of the signal isolating the other portion. In other
`words, given sufficient information about one of the signal
`portions.that signal portion can be extracted.
`Conventional correlation cancelers, such as adaptive
`noise cancelers, dynamically change their transfer function
`to adapt to and remove portions of a composite signal.
`However. correlation cancelers require either a secondary
`reference or a primary reference which correlates to either
`the secondary signal portion only or the primary signal
`portion only. For instance, for a measured signal containing
`noise and desirable signal, the noise can be removed with a
`correlation canceler if a noise reference is available. This is
`often the case. Although the amplitude of the reference
`signals are not necessarily the same as the amplitude of the
`
`2
`corresponding primary or secondary Signal portions, they
`have a frequency spectrum which is similar to that of the
`primary or secondary signal portions.
`In many cases, nothing or very little is known about the
`secondary and/or primary signal portions. One area where
`measured signals comprising a primary signal portion and a
`secondary signal portion about which no information can
`easily be determined is physiological monitoring. Physi-
`ological monitoring generally involves measured signals
`derived from a physiological system, such as the human
`body. Measurements which are typically taken with physi-
`ological monitoring systems include electrocardiographs,
`blood pressure, blood gas saturation (such as oxygen
`saturation), capnographs, other blood constituent
`monitoring, heart rate, respiration rate, electro-
`encephalograph (EEG) and depth of anesthesia, for example.
`Other types of measurements include those which measure
`the pressure and quantity of a substance within the body
`such as cardiac output, venous oxygen saturation, arterial
`oxygen saturation. bilirubin, total hemoglobin. breathalyzer
`testing, drug testing, cholesterol
`testing, glucose testing,
`extra vasation, and carbon dioxide testing. protein testing,
`carbon monoxide testing, and other in—vivo measurements,
`for example. Complications arising in these measurements
`are often due to motion of the patient, both external and
`internal (muscle movement, vessel movement, and probe
`movement, for example), during the measurement process.
`Many types of physiological measurements can be made
`by using the known properties of energy attenuation as a
`selected form of energy passes through a medium.
`A blood gas monitor is one example of a physiological
`monitoring system which is based upon the measurement of
`energy attenuated by biological tissues or substances. Blood
`gas monitors transmit light into the test medium and mea-
`sure the attenuation of the light as a function of time. The
`output signal of a blood gas monitor which is sensitive to the
`arterial blood flow contains a component which is a wave—
`form representative of the patient’s arterial pulse. This type
`of signal. which contains a component related to the
`patient’s pulse. is called a plethysmographic wave, and is
`shown in FIG. 1 as curve s. Plethysmographic waveforms
`are used in blood gas saturation measurements. As the heart
`beats, the amount of blood in the arteries increases and
`decreases, causing increases and decreases in energy
`attenuation, illustrated by the cyclic wave 5 in FIG. 1.
`Typically, a digit such as a finger, an ear lobe, or other
`portion of the body where blood flows close to the skin, is
`employed as the medium through which light energy is
`transmitted for blood gas attenuation measurements. The
`finger comprises skin. fat, bone, muscle. etc., shown sche—
`matically in FIG. 2, each of which attenuates energy incident
`on the finger in a generally predictable and constant manner.
`However, when fleshy portions of the finger are compressed
`erratically, for example by motion of the finger, energy
`attenuation becomes erratic.
`
`An example of a more realistic measured waveform S is
`shown in FIG. 3, illustrating the effect of motion. The
`primary plethysmographic waveform portion of the signal s
`is the waveform representative of the pulse, corresponding
`to the sawtooth—like pattern wave in FIG. 1. The large,
`secondary motion-induced excursions in signal amplitude
`obscure the primary plethysmographic signal 5. Even small
`variations in amplitude make it difficult to distinguish the
`primary signal component s in the presence of a secondary
`signal component n.
`A pulse oxirneter is a type of blood gas monitor which
`non—invasively measures the arterial saturation of oxygen in
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`40
`
`40
`
`

`

`5,632,272
`
`3
`the blood. The pumping of the heart forces freshly oxygen—
`ated blood into the arteries causing greater energy attenua-
`tion. As well understood in the art. the arterial saturation of
`oxygenated blood may be determined from the depth of the
`valleys relative to the peaks of two plethysmographic wave-
`forms measured at separate wavelengths. Patient movement
`introduces motion artifacts to the composite signal as illus-
`trated in the plethysmographic waveform illustrated in FIG.
`3. These motion artifacts distort the measured signal.
`
`SUMMARY OF THE INVENTION
`
`This invention provides improvements upon the methods
`and apparatus disclosed in U.S. patent application Ser. No.
`08/132312. filed Oct. 6. 1993. entitled Signal Processing
`Apparatus. which earlier application has been assigned to
`the assignee of the instant application. The present invention
`involves several ditferent embodiments using the novel
`signal model in accordance with the present invention to
`isolate either a primary signal portion or a secondary signal
`portion of a composite measured signal. In one embodiment,
`a signal processor acquires a first measured signal and a
`second measured signal that is correlated to the first mea-
`sured signal. The first signal comprises a first primary signal
`portion and a first secondary signal portion. The second
`signal comprises a second primary signal portion and a
`second secondary signal portion. The signals may be
`acquired by propagating energy through a medium and
`measuring an attenuated signal after transmission or reflec-
`tion. Alternatively. the signals may be acquired by measur—
`ing energy generated by the medium.
`In one embodiment. the first and second measured signals
`are processed to generate a secondary reference which does
`not contain the primary signal portions from either of the
`first or second measured signals. This secondary reference is
`correlated to the secondary signal portion of each of the first
`and second measured signals. The secondary reference is
`used to remove the secondary portion of each of the first and
`second measured signals via a correlation canceler. such as
`an adaptive noise canceler. The correlation canceler is a
`device which takes a first and second input and removes
`from the first input all signal components which are corre-
`lated to the second input. Any unit which performs or nearly
`performs this function is herein considered to be a correla-
`tion canceler.
`
`An adaptive correlation canceler can be described by
`analogy to a dynamic multiple notch filter which dynami—
`cally changes its transfer function in response to a reference
`signal and the measured signals to remove frequencies from
`the measured signals that are also present in the reference
`signal. Thus. a typical adaptive correlation canceler receives
`the signal from which it is desired to remove a component
`and receives a reference signal of the undesired portion. The
`output of the correlation canceler is a good approximation to
`the desired signal with the undesired component removed.
`Alternatively. the first and second measured signals may
`be processed to generate a primary reference which does not
`contain the secondary signal portions from either of the first
`or second measured signals. The primary reference may then
`be used to remove the primary portion of each of the first and
`second measured signals via a correlation canceler. The
`output of the correlation canceler is a good approximation to
`the secondary signal with the primary signal removed and
`may be used for subsequent processing in the same instru-
`ment or an auxiliary instrument. In this capacity,
`the
`approximation to the secondary signal may be used as a
`reference signal for input to a second correlau‘on canceler
`
`4
`together with either the first or second measured signals for
`computation of, respectively. either the first or second pri—
`mary signal portions.
`Physiological monitors can benefit from signal processors
`of the present invention. Often in physiological measure-
`ments a first signal comprising a first primary portion and a
`first secondary portion and a second signal comprising a
`second primary portion and a second secondary portion are
`acquired. The signals may be acquired by propagating
`energy through a patient’s body (or a material which is
`derived from the body. such as breath, blood. or tissue, for
`example) or inside a vessel and measuring an attenuated
`signal after transmission or reflection. Alternatively,
`the
`signal may be acquired by measuring energy generated by a
`patient’s body. such as in electrocardiography. The signals
`are processed via the signal processor of the present inven-
`tion to acquire either a secondary reference or a primary
`reference which is input to a correlation canceler. such as an
`adaptive noise canceler.
`One physiological monitoring apparatus which benefits
`from the present invention is a monitoring system which
`determines a signal which is representative of the arterial
`pulse, called a plethysmographic wave. This signal can be
`used in blood pressure calculations. blood constituent
`measurements. etc. A specific example of such a use is in
`pulse oximetry. Pulse oxjrnetr'y involves determining the
`saturation of oxygen in the blood. In this configuration. the
`primary portion of the signal is the arterial blood contribu-
`tion to attenuation of energy as it passes through a portion
`of the body where blood flows close to the skin. The
`pumping of the heart causes blood flow to increase and
`decrease in the arteries in a periodic fashion. causing peri-
`odic attenuation wherein the periodic waveform is the
`plethysmographic waveform representative of the arterial
`pulse. The secondary portion is noise. In accordance with the
`present invention. the measured signals are modeled such
`that this secondary portion of the signal is related to the
`venous blood contribution to attenuation of energy as it
`passes through the body. The secondary portion also
`includes artifacts due to patient movement which causes the
`venous blood to flow in an unpredictable manner. causing
`unpredictable attenuation and corrupting the otherwise peri-
`odic plethysmographic waveform. Respiration also causes
`the secondary or noise portion to vary. although typically at
`a lower frequency than the patients pulse rate. Accordingly.
`the measured signal which forms a plethysmographic wave-
`form is modeled in accordance with the present invention
`such that the primary portion of the signal is representative
`of arterial blood contribution to attenuation and the second-
`ary portion is due to several other parameters.
`A physiological monitor particularly adapted to pulse
`oximetry oxygen saturation measurement comprises two
`light emitting diodes (LED’s) which emit light at different
`wavelengths to produce first and second signals. A detector
`registers the attenuation of the two dijferent energy signals
`after each passes through an absorptive media. for example
`a digit such as a finger. or an earlobe. The attenuated signals
`generally comprise both primary (arterial attenuator) and
`secondary (noise) signal portions. A static filtering system.
`such as a bandpass filter. removes a portion of the secondary
`signal which is outside of a known bandwidth of interest.
`leaving an erratic or random secondary signal portion, often
`caused by motion and often difficult to remove. along with
`the primary signal portion.
`A processor in accordance with one embodiment of the
`present invention removes the primary signal portions fiom
`the measured signals yielding a secondary reference which
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`41
`
`41
`
`

`

`5,632,272
`
`5
`is a combination of the remaining secondary signal portions.
`The secondary reference is correlated to both of the second-
`ary signal portions. The secondary reference and at least one
`of the measured signals are input to a correlation canceler.
`such as an adaptive noise canceler, which removes the
`random or erratic portion of the secondary signal. This
`yields a good approximation to a primary plethysmographic
`signal as measured at one of the measured signal wave-
`lengths. As is known in the art, quantitative measurements of
`the amount of oxygenated arterial blood in the body can be
`determined from the plethysmographic signal in a variety of
`ways.
`The processor of the present invention may also remove
`the secondary signal portions from the measured signals
`yielding a primary reference which is a combination of the
`remaining primary signal portions. The primary reference is
`correlated to both of the primary signal portions. The
`primary reference and at least one of the measured signals
`are input to a correlation canceler which removes the pri-
`mary portions of the measured signals. This yields a good
`approximation to the secondary signal at one of the mea-
`sured signal wavelengths. This signal may be useful for
`removing secondary signals from an auxiliary instrument as
`well as determining venous blood oxygen saturation.
`In accordance with the signal model of the present
`invention. the two measured signals each having primary
`and secondary signal portions can be related by coeficients.
`By relating the two equations with respect to coefficients
`defined in accordance with the present invention. the coef-
`ficients provide information about the arterial oxygen satu-
`ration and about the noise (the venous oxygen saturation and
`other parameters). In accordance with this aspect of the
`present invention, the coeflicients can be determined by
`minimizing the correlation between the primary and sec-
`ondary signal portions as defined in the model.