`[11] Patent Number:
`[19]
`United States Patent
`
`Diab et al.
`[45] Date of Patent:
`*Jun. 27, 2000
`
`U8006081735A
`
`[54]
`
`SIGNAL PROCESSING APPARATUS
`
`[75]
`
`Inventors: Mohamed K. Diab; Massi E. Kiani;
`Ibrahim M. Elfadel, all of Laguna
`Niguel; Rex J. McCarthy, Mission
`Viejo; Walter M. Weber, Los Angeles;
`.
`.
`Robert A. Smlth, Corona, all of Calif.
`.
`.
`.
`.
`.
`[73] Assignee: Ma51m0 C0rp0rat10n, Irvme, Calif.
`
`[ * ] Notice:
`
`This patent is subject to a terminal dis-
`claimer.
`
`[21] Appl‘ No“ 08/887315
`[22]
`Filed:
`JuL 3, 1997
`
`4,824,242
`4,848,901
`4,860,759
`498639265
`1223:;
`4,869,254
`,
`,
`4,883,353
`4,892,101
`4,907,594
`
`4/1989 FriCk eta1~ ~
`7/1989 Hood, Jr.
`.
`8/1989 Kahn 6t a1~ ~
`9/1989 F19W6r 6t al~ ~
`313:3 Er1°¥6f1~t~ 1
`9
`ralg’
`r‘ e a' ’
`/1989 Stone et al.
`.
`11/1989 Hausman .
`1 1990 Ch
`t
`#1990 Muezuflg e a
`
`l..
`
`(List continued on next page.)
`FOREIGN PATENT DOCUMENTS
`
`1674798
`92/15955
`
`9/1991 U.S.S.R. .
`9/1992 WIPO .
`
`Related US. Application Data
`
`OTHER PUBLICATIONS
`
`[63] Continuation of application No. 08/859,837, May 16, 1997,
`which is a continuation of application No. 08/320,154, Oct.
`7, 19947.1)”: No. 5,632,272, which is a continuation—in—part
`gf apighgatlon No- 08/132,812, Oct 6; 1993, Pat NO-
`’490’ 0 ’
`
`.“Digital Processing Of
`a1”
`et
`Jingzheng, Ouyang
`Electrocardiograms—Detection
`0f
`High—Resolution
`His—Purkinje Activity from the Body Surface”, Biomediz-
`inische Technik, 33, Oct. 1, 1988, No. 10, Berlin, W.
`Germany, pp. 224—230.
`
`[51]
`
`Int. Cl.7 ........................................................ A61B 5/00
`
`(LISI continued on next page.)
`
`[52] U.S. Cl.
`
`.......................... 600/336; 600/481; 600/508;
`600/529
`[58] Field of Search ..................................... 600/300, 322,
`600/323, 330, 336, 473, 476, 481, 500,
`508, 509, 529
`
`[56]
`
`References Cited
`
`i
`
`.
`
`.
`
`U.S. PATENT DOCUMENTS
`3/1972 Lavallee
`3 647 299
`12/1972 Herczfeld et a1
`3,704,706
`12/1977 Sweeney .
`4,063,551
`5/1978 Kofsky et a1.
`4,086,915
`6/1978 Nagy .
`4,095,117
`4,407,290 10/1983 Wilber .
`4,537,200
`8/1985 Widrow .
`476497505
`3/1987 Z1115“: .Jr- et ‘11-
`27:33:23:
`313::
`ITaguChI '
`t
`1
`,
`,
`saacson e a .
`.
`4,799,493
`1/1989 DuFault.
`4,800,495
`1/1989 Smith.
`4,819,752
`4/1989 Zelin .
`
`-
`
`Primary Examiner—Eric F, Winakur
`Attorney, Agent, or Firm—Knobbe, Martens, Olson & Bear,
`LLP
`
`[57]
`
`ABSTRACT
`
`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
`in particular detail with respect to blood oximetry measure-
`mems‘
`
`28 Claims, 37 Drawing Sheets
`
`
`
`
`
`
`SIGNAL
`CONDITIONER
`
`
`
`
`
`n’(I) = “mm — ranxbfl)
`Z7
`
`CORRELATION
`CANCELER
`
`Z!
`
`DISPLAY
`”
`SAaG)
`
`1
`
`APPLE 1030
`
`1
`
`APPLE 1030
`
`
`
`6,081,735
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`Haykin, Simon, Adaptive Filter Theory, Prentice Hall,
`Englewood Cliffs, NJ, 1991.
`
`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, Arnon, “Volume I” Time and Frequency Domains
`Analysis, Biomedical Signal Processing, CRC Press, Inc.,
`Boca 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., “Spectrophotometric 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 al., “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. p. 36—37.
`
`.
`
`.
`
`3/1990 Corenman et al.
`4,911,167
`5/1990 Shiga et al.
`.
`4,927,264
`5/1990 Goodman et al.
`4,928,692
`8/1990 Lehman.
`4,948,248
`9/1990 Hall.
`4,955,379
`.
`9/1990 Zurek et al.
`4,956,867
`10/1990 Conlon et al.
`4,960,126
`10/1991 Hirao et al.
`.
`5,057,695
`9/1993 Prosser .
`5,246,002
`.
`12/1993 Kronberg et al.
`5,273,036
`7/1995 Mathews ................................. 600/323
`5,431,170
`5,458,128 10/1995 Pulanyi et al.
`.
`5,632,272
`5/1997 Diab et al.
`.............................. 600/323
`
`.
`
`OTHER PUBLICATIONS
`
`Chen, Jiande, et al., “Adaptive System for Processing of
`Electrogastric Signals”, Images of the Twenty—First Cen-
`tury, Seattle, WA, vol. 11, Nov. 9—12, 1989. pp. 698—699.
`Varanini, M. et al., “A Two Channel Adaptive Filtering
`Approach for Recognition of the QRS Morphology”, Pro-
`ceedings of the Computers in Cardiology Meeting, Venice,
`Sep. 23—26, 1991, Institute of Electrical and Electronics
`Engineers, pp. 141—144.
`Rabiner, Lawrence et al. Theory and Application of Digital
`Signal Processing, p. 260, 1975.
`Tremper, Kevin et al., Advances in Oxygen Monitoring pp.
`137—153, 1987.
`Harris, Fred et al., “Digital Signal Processing with Efficient
`Polyphase Recursive All—Pass Filters”, Presented at Inter-
`national Conference on Signal Processing, Florence, Italy,
`Sep. 4—6, 1991, 6 pages.
`
`2
`
`
`
`US. Patent
`
`Jun. 27,2000
`
`Sheet 1 0f 37
`
`6,081,735
`
`I
`
`F/G./
`
`TISSUE
`
`
`
`BONE
`MUSCLE
`
`
`ARTERIAL BLOOD
`
`VENOUS BLOOD
`
`
`FIG.2
`
`
`
`3
`
`
`
`US. Patent
`
`Jun. 27,2000
`
`Sheet 2 0f 37
`
`6,081,735
`
`CORRELATION
`
`
` DISPLAY
`
`
`Siafi)
`
`CANCELER
`
`FIG. 4a
`
`4
`
`
`
`US. Patent
`
`Jun. 27,2000
`
`Sheet 3 0f 37
`
`6,081,735
`
`
`
`“151(1)
`
`
`DISPLAY
`
`
`
`CORRELATION
`
`CANCELER
`
`FIG. 4b
`
`5
`
`
`
`US. Patent
`
`Jun. 27,2000
`
`Sheet 4 0f 37
`
`6,081,735
`
`Siam OR sgbm
`
`niét) OR nib“)
`
`6
`
`
`
`US. Patent
`
`Jun. 27,2000
`
`Sheet 5 0f 37
`
`6,081,735
`
`
`
`NOIlONnJHEIJSNVHJ.
`
`FREQUENCY (f)
`
`F/G.5c
`
`7
`
`
`
`US. Patent
`
`Jun. 27,2000
`
`Sheet 6 0f 37
`
`6,081,735
`
`
`
` A2 A2 A2 52 A2 A2A2
`AnAn An A. An AnAn
`
`FIG. 5a
`
`[11
`
`
`
`U1
`
`
`
`
`
`A A A A A1A1A1
`A2 A2 A2 A2 A2 A2A2
`
`
`
`
`
`
`
`A1 A1 A1 A1 A1 A1A1
`A2 A2 A2 A2 A2 A2A2
`A3 A3 A3 A4 A4 A3A4
`£4
`A;
`AA4
`A3
`A: A5A66A5 6A5 A56
`AnAn An A, An AnAn
`FIG. 66
`U1
`
`A6 A
`
`A
`
`A
`
`A ‘6 A
`
`
`
`A: ASASBAS 6A6 A56
`
`AnAn An A. An AnAn
`
`8
`
`
`
`US. Patent
`
`Jun.27,2000
`
`Sheet7 0f37
`
`6,081,735
`
`EDEMmem
`
`mohomhmo
`
`EN
`
`kw
`
`mok<mOMHz_
`
`mmm<30m
`
`mm4moz<o
`
`zofi<4mmmoo
`
`UN6?.
`
`32m32m
`
`
`
`385gISEE+38$5:39$n3.(HE
`
`385$:EEG+38mmmy132mn3.Npym
`
`
`
`Eflmfi132:+£02ch32mu3;:E
`
`9
`
`
`
`
`
`
`
`US. Patent
`
`Jun. 27,2000
`
`Sheet 8 0f 37
`
`6,081,735
`
`~Q
`I\
`
`~°°
`
`Q — ¢
`Ln.
`
`
`
`SIGNALCOEFFICIENTS
`
`RELATIVE CORRELATION CANCELER
`
`ENERGY OUTPUT
`
`10
`
`10
`
`
`
`US. Patent
`
`Jun. 27,2000
`
`Sheet 9 0f 37
`
`6,081,735
`
`o
`r\
`
`L5
`L.~
`
`
`
`-~°°
`
`
`
`:—¢
`
`
`
`SIGNALCOEFFICIENTS
`
`
`
`RELATIVE CORRELATION CANCELER
`ENERGY OUTPUT
`
`11
`
`11
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 10 0f 37
`
`6,081,735
`
`LEAST SQUARES LATTICE
`PREDICTOR
`
`REGRESSION
`FILTER
`
`.HO
`
`03«a
`
`
`
`3%?5950
`
`Qmr\\
`
`
`
`12
`
`12
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 11 0f 37
`
`6,081,735
`
`QRD- LSL PREDICATOR
`
`QRD— LSL FILTER
`
`om<3xo<m
`
`mzfilmzmoo
`
`mmHDQEOo
`
`om<3xo<m
`
`mZmlmzfioo
`
`KMHDQEOO
`
`Qm<3xo<m
`
`mZmlmzfiOo
`
`meDQEOO
`
`om<3xo<m
`
`mZmlmzfioo
`
`«MHDQEOQ
`
`13
`
`Qm<3m0u
`
`mzmlmzfioo
`
`mmHDQEOQ
`
`om<>>m0L
`
`mZmlmzmoo
`
`awhaafioo
`
`13
`
`
`
`
`
`
`
`
`US. Patent
`
`Jun. 27,2000
`
`Sheet 12 0f 37
`
`6,081,735
`
`_
`
`L20
`
`INITIALIZE NOISE
`CANCEUER
`
`[30
`
`INPUT NEW SAMPLES
`[Skaco AND SAbUH-
`
`TIME UPDATE
`or [z‘T] ELEMENTS
`
`[n' (t) or s'(+)]
`CALCULATE REFERENCE
`FOR TWO MEASURED SIGNAL
`SAMPLES
`
`I40
`
`ZERO— STAGE
`UPDATE
`
`/
`
`ORDER UPDATE
`m”1—STAGE or
`LSL-PREDICTOR
`
`
`
`
`
`
`
`¢
`
`ORDER UPDATE
`mfh—STAGE or
`REGRESSION
`FILTER(S)
`m = m + 1
`
`200
`
`CALCULATE
`
`FIG. 9
`
`14
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 13 0f 37
`
`6,081,735
`
`/200
`
`INITIALIZE NOISE
`CANCELLER
`
`INPUT NEw SAMPLES
`[3mm AND 8mm]
`
`/.500
`
`TIME UPDATE
`OF [2’ 1] ELEMENTS
`
`[n’ (1) or s’ (1)]
`CALCULATE REFERENCE
`FOR Two MEASURED SIGNAL
`SAMPLES
`
`
`
`I400
`
`ZERO-STAGE
`UPDATE
`
`7500
`
`I600
`
`
`
`ORDER UPDATE
`th—STAGE OF
`
`QRD—LSL-PREDICTOR
`
`
`
`
`ORDER UPDATE
`th—STAGE 0F
`
`
`QRD—LSL
`
`
`FILTER(S)
`
`
`
`m = m + 1
`
`
`
`
`200 a
`
`2/00
`
`15
`
`FlG.9a
`
`¢ Y
`
`S
`
`E
`
`CALCULATE
`OUTPUT
`
`TO DISPLAY
`
`15
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 14 0f 37
`
`6,081,735
`
`LEAST SQURES LATTICE
`PREDICTOR
`
`REGRESSION
`FILTER
`
`REGRESSION
`FILTER
`
`+
`
`393:»
`
`mShape
`
`16
`
`16
`
`
`
`US. Patent
`
`Jun.27,2000
`
`Sheetls 0f37
`
`6,081,735
`
`QRD— LSL PREDlCATOR
`
`FILTER 1
`
`FILTER 2
`
`omismOu
`QQx@Nx «whoa200n2%1m.2.moo
`
`17
`
`17
`
`
`
`US. Patent
`
`Jun.27
`
`9
`
`2000
`
`Sheet16 0f37
`
`6,081,735
`
`QMH;
`
`mmw\
`
`MVM.
`
`
`
`
`
`“MM;._O~_._.zooz_<o
`
`
`
`ZO_H<m_D._.<mzmo>xo
`
`EKOmmSSS
`
`$.55NEEES:
`
`
`
`oz_mmmoomn_._<zo_m45.6.0
`
`o_Im<m002m>I._.m._n_
`
`zo_ko<m._.xm._<zo_m.oz<
`
`
`
`O._.OO._<Z<
`
`._<._._o_n_
`
`zo_mmm>zoo
`
`OZZOEOZOO
`
`._<zo_m
`
`
`
`004<z<_mOFomFmomumm,
`
`__
`
`.
`.0232?uE_mmw1_mmww
`
`m«ma\\\mmj
`
`
`
`momzmm1
`
`mkww
`
`
`
`
`
`;1‘”mt—Em0mm.
`
`kwww
`
`mmww
`
`Qua;
`
`
`
`18
`
`\\SQ
`
`Jomhzoo
`
`Summon.5E5zo_m$>zoo
`
`
`
`O._.._<._._O_o
`
`OO._<Z<
`
`
`
`hzmmmbo”Ebb—am.
`
`maniac
`
`18
`
`
`
`
`
`
`
`
`
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 17 0f 37
`
`6,081,735
`
`(\QM.
`
`WNW
`
`mm.
`
`MN“
`
`WNW
`
`mo<bu_o>
`
`mozmmmhmm
`
`19
`
`\NM.
`
`NW5
`
`Io._.<..
`
`Hzmmmso
`
`Jomkzoo
`
`mELEm
`
`ExSQ
`
`WNWWNW
`
`
`
`Io._.<._Io._.<._
`
`19
`
`
`
`
`US. Patent
`
`Jun.27,2000
`
`Sheet18 0f37
`
`6,081,735
`
`<H<oNIXON
`
`meoz:mor
`
`Ammoohv
`Q\<oza<xm
`
`
`
`mMHmm>zoo
`
`Q\<CmNF
`awkmm>zoo
`
`
`
`QMMK
`
`amo>mHmm220
`
`ssh\
`
`
`
`304
`
`mm<a
`
`mmHJE
`
`§<mooma
`
`Z<O
`
`mmE3Q§<
`
`Ioi
`
`mm<a
`
`KMFAE
`
`Imam
`
`mmEDQE<
`
`20
`
`20
`
`
`
`
`
`
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 19 0f 37
`
`6,081,735
`
`mam.\\
`
`NIXON
`
`mm4n§<m
`
`QQM.
`
`mmnEDm
`
`mn_n__2<m
`
`§<mooma
`
`
`
`Hzmmmaommfihim
`
`Jomhzoo
`
`
`
`JOmHZOoz_<o
`
`MVMJ
`
`NMMJ
`
`
`
`>420o<mm
`
`>mO§m=2
`
`2200
`
`mmmhmamm
`
`MNSQ
`
`>m02m2
`
`
`
`<._.<Q/%.QM
`
`o<._.../._.z_
`
`mmm,\
`
`mmjomkzooomozz
`
`
`
`Hmoa._<_mmm
`
`q<zmmhxm
`
`>mO§m§
`
`21
`
`21
`
`
`
`
`
`
`
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 20 0f 37
`
`6,081,735
`
`In_<moo_2m>_.:m._n_
`wh<mmmuSn.
`
`mm._3n_
`
`mh<m
`
`ZOF<._DOI_<O
`
`WSW
`
`
`
`zo:§3<m20:38.20
`
`
`
`zmo>xozo_._.<m2.<m
`
`z©fi<mDH<m
`
`EmOumz<mH
`
`%\SQ
`
`22
`
`VQV
`
`(\QV
`
`QQV
`
`mo_._.m_._.<.rm
`
`20:32:50
`
`zO:.<._DQO_2m_O
`
`Aoo<EOmLV
`
`NIXON
`
`22
`
`
`
`
`
`
`
`
`
`
`US. Patent
`
`Jun.27,2000
`
`Sheet2170f37
`
`6,081,735
`
`mmw\
`
`WWW
`
`www
`
`mfiw
`
`QMVNIWNW“
`
`mm4a2<mwHm<4Q323mQmm
`
`mMJQE<mwHm<4m323mHzEm§<
`
`mMJQE<mvHm<4a:23m
`
`
`
`mmgafi<m¢Hm<4a:23m
`
`HZEm§<
`
`HzEm§<HZEm2<
`
`Ammdszmm3ézom9:338:
`
`mmSQ
`
`Homem
`
`\WV
`
`omk<43002
`
`NIXONH<
`
`<H<Q
`
`23
`
`
`
`HZEm§<+omm_HZEm§<+Qmm
`
`23
`
`
`
`
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 22 0f 37
`
`6,081,735
`
`WQV\\
`
`nflmfi
`
`
`
`Fozma<zm0mm
`
`MN:mva
`
`
`
`mmmmamFoakao
`
`
`
`AmMJQE<monmv
`
`ZOF<_2_OMQ
`
`or>m
`
`
`
`mmHJEmm<a§04m:
`
`AmMJa2<mm_mv
`
`
`
`4mzz<zo0mm
`
`ANImmmv
`
`Qm
`
`QWV
`
`WWW
`
`24
`
`AN:38
`
`
`
`Amm4a2<mommv
`
`Hoima<zmomm<mmz_
`
`
`mmumamPsakoo
`ZO_._.<2_omo
`
`mmFJEmm<a304a:
`
`4mzz<zoomm<mmz_
`
`OF>m
`
`AmMJa2<mmemv
`
`ANImmmv
`
`.Q\SE
`
`24
`
`
`
`
`
`
`
`US. Patent
`
`53
`
`
`
`wmwk
`
`
`9%mumVm5.
`
`
`
`
`
`mmm»m.25:29:58zop<m2<m
`.WSWmmmmIvm58”.
`
`"MyQQMmfimlommzo_._.<m_3.r<mVQm.Qmmm
`
`Jmm»m”?I.
`
`
`
`VmVQWV(NQV
`
`
`
`MEa:558m8m
`ofi53am28&5:mm<aoz<m88mBig/Em8m
`mm._n_2<mAmmdimES3::4<>02mm004AmmfiwémQB.NIm‘mmv
`
`
`
`WWW
`
`%%V
`
`Qmww
`
`
`
`
`
`QE:a:65E28&5:Smfitz.Smfitz8mg;ExmnzzmBmfitz
`
`wwfifidm$5505mmwmwfiwfié2800me03Ammdim0%.N:38
`
`
`
`3mE;m92.2%mam8m2T;I._amazeH.5355:as&m2:582mzoidmmoo
`
`3mzamzaSm.9%M£38.238m5m38m
`
`zoidmmoozo:<m2<m9S$08$96
`
`
`7@2dezop<m2<m8mmz_m_
`
`Sm%E29:38zo:§2<m
`
`Io<mmo...
`
`
`
`6mz_mm>¢mfimNNm.m2”.
`
`m5noBWZEZ8m<Ez_
`
`7.,ll1zQEdEOQzocfimmmoo\
`
`
`
`000mmomommomoz_mRxHut
`
`8m<Ez_mam/5:2.
`
`25
`
`25
`
`
`
`
`
`
`
`
`
`
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 24 0f 37
`
`6,081,735
`
`mm».\\
`
`WM“
`
`9.
`
`ZO_H<mD._.<m
`
`EIHEOQZ
`
`_
`
`mumfi.
`
`mmBOa
`
`
`
`immw
`
`mo;
`
`25:05___
`
`1_
`
` “mmgoa25mohz_mo<:ommn
`
`awkm<2mww_
`m>maoIIIIIII.4
`
`
`mmmoOma<om2<4
`
`Egosmommmuzg
`.mfim.Imm._.n__.._I._<>O_2m_m_
`wm<moz<m00
`
`z<omm2<zop<moh<m
`20mmmm34<>NFFV
`
`mok<z:mm
`
`\Mfi.“xWWWVVIQ
`
`
`m44moommmzaz/WWW
`
`NVM.
`
`
`mfim.
`
`Ram.
`
`mozmmmumm
`
`mo._.<mm_zmo
`
`WNW
`
`ZOF<m3H<m
`
`ZOF<DOm
`
`
`
`,mMJ12<monmv
`
`AN:m.mo
`
`omm<muz
`
`
`
`.mm4m2<monmv
`
`AN:mNo
`
`0mm
`
`Aomo_0»men
`
`26
`
`26
`
`
`
`
`
`
`
`
`US. Patent
`
`Jun.27,2000
`
`Sheet25 0f37
`
`6,081,735
`
`m§\\
`
`5mm.
`
`zo:<mDH<m
`
`zmo>xo
`
`ZOFamoxm
`
`Ozfioz<I
`
`:QQM.
`
`QZ<ujo
`
`IHOOEW
`
`HQMJMm
`
`OZEHOOEm
`
`mmHJE
`
`10E
`
`mozmoizoo
`
`HmMH
`
`WKQR
`
`0504
`
`
`
`02¥m3<3025W
`
`ZmMHDQEOQ
`
`WMHDmEHH<
`
`mofimF<HmZE
`
`mm>mao,mm30&25
`
`27
`
`27
`
`
`
`
`
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 26 0f 37
`
`6,081,735
`
`EmOmm><>>
`
`9W“wt
`
`
`mH<mmmHJE
`
`ozpze4uk<mHm<mx
`
`
`
`«MHJEHDQHDO
`
`.mumoo
`
`
`
`Hm<m1HDQHDO
`
`WWW
`
`MH<m
`
`>><m2325.0QO
`4<mkomum
`
`Qm>4<z<
`
`zoP<2Pmm
`
`ZOPOE
`
`H0<¢Fm<
`
`ZOEmMKQDm
`
`V%W
`
`
`
`.mm;a2<monmv
`
`Hoxma<zm
`
`
`
`AN:m\mm
`
`cum
`
`ZOFKDH<m
`
`28
`
`
`
`
`
`mDH<Hm20:02mo<mm><
`
`
`
`1H9;x<ma
`
`m?!\
`
`4<mkomam
`
`ZOF<2Pmm
`
`mm,“%\m.
`
`00
`
`oz<4<>O§mm
`
`mm<aoz<m
`
`KMHJE
`
`
`
`.mMJaz<monmv
`
`AN:mam
`
`Hozmu<zm
`
`omm<mu2_
`
`
`
`
`
`Iu<m002m>IHMJaz<MJozazomuv
`
`
`
`Amm>maommaoa
`
`28
`
`
`
`
`
`
`
`
`
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 27 0f 37
`
`6,081,735
`
`RM;\\
`
`\Nm.
`
`
`
`u_ _5.9,moEmlzz_QMmjma_no59233_WNW»
`
`
`
`
`
`
`
`AmflaimES
`
`mm<aoz<m
`
`mm:..=.._
`
`\Mm.
`
`ZO_.r<mD._.<m
`
`
`
`zo_2m3<m._<_mm:m<
`
`zop<m3<mzomb
`292.533
`
`
`
`2mOmm><§ISLEmo._.<§:.mm
`
`
`zfid$533$883<om:<.___
`EhI.235”.I!
`
`
`
`(th.mozmmmmmm
`
`.mméém28
`AN:0%
`
`omm<mmz_
`
`.mm._n_z<m0an
`AN:0%
`
`BE
`
`29
`
`”5.21“..sz
`29.230”.—
`
`
`29
`
`
`
`
`
`
`
`
`US. Patent
`
`Jun.27,2000
`
`Sheet28 0f37
`
`6,081,735
`
`EKOum><§
`
`z<m40
`
`
`
`mfifiV\\\\
`
`\\%‘\
`
`NR“
`
`
`
`MN“
`
`mw<a304
`
`mmHJE
`
`H25:
`
`mmmooma
`
`mOH<2me
`
`mam23mZ:
`
`nommminz
`
`mJJmo
`
`<0m§<4
`
`Cz_mmm23m
`
`CZ_m2<o
`
`
`
`be“wt
`
`ka‘z/
`
`
`
`zop<m2<m435:2
`
`zoEEDEm28...:
`
`£338.20
`
`
`
`_ZOF<DOu_ZOF<m3H<m
`
`hmfimfifi
`
`mmHJE
`
`oo
`
`4<>02mm
`
`\Nh
`
`
`
`NWQmozummumm
`
`m0p<mmzmo
`
`|||||.oum<muz
`
`.mmdzd‘mEB
`
`fix0%
`
`.mmdimORV
`
`AN...08
`
`8m
`
`30
`
`
`
`30
`
`
`
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 29 0f 37
`
`6,081,735
`
`normm
`
`mmmmmmmmw0:3”
`
`
`
`
`
`mm:._<>z<omzo_._.<~_D._.<m
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`OUTPUT ENERGY
`
`31
`
`31
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 30 0f 37
`
`6,081,735
`
`ZOF<mDH<mOH
`
`mZO_H<4304<o
`
`§<m00HmE
`
`QWQ
`
`mex
`
`
`
`
`
`QQW
`
`ZO_._.<w_Dh<m
`
`ZOF<DOm
`
`
`
`
`
`
`
`2|._|_|zu._:;I._|Q;|.*IO
`
`Nx2<mKHZ—m
`
`NQQN
`
`Qmm
`
`_xz<mKNEE
`
`
`
`
`
`
`
`z.._|72...:LNmIE.Elo
`
`omm<muz_
`
`VQQ
`
`32
`
`32
`
`
`
`
`
`
`
`US. Patent
`
`Jun. 27,2000
`
`Sheet 31 0f 37
`
`6,081,735
`
`I!)
`O
`
`x
`
`xxxxx
`
`x
`
`U)
`L|.l
`
`D_
`
`l <> Z 2.
`
`—
`g
`:>I'—
`a
`
`V'
`C\l
`-
`
`3
`
`><><><
`
`NUMBER OF OCCURENCES
`
`0
`
`33
`
`33
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 32 0f 37
`
`6,081,735
`
`ZOF<mDH<m
`
`zmo>xo
`
`QMHQ
`
`Hm<n_
`
`
`
`mmJDQ
`
`m._.<m
`
`zoc<4304<o
`
`Z<mjo
`
`Ia<m002m>I._.m_._n_
`
`\zmoumz<mk
`mk<mmmJDQ
`zop<mah<mNImNo
`ZOF<§0mo
`
`29541500360
`
`Aoo<EOKEV
`
`NIxom
`
`34
`
`WWW“wt
`
`34
`
`
`
`
`
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 33 0f 37
`
`6,081,735
`
`Nmfi
`
`WWW»
`
`WNWVNQ
`
`QVM
`
`292.535
`
`
`
`
`
`Rm53mmxmdzoo382.;
`
`
`
`QMQKNQ
`
`8xo<8E5:
`
`mmSn.9E20.52.:
`
`Amflazé93
`
`E20:02.:
`33%;53
`
`53%
`
`Vmfi
`
`%m.%
`
`NEW.
`
`6:2838;;
`8g2SEE:
`Gum/Eu;
`
`a:
`
`Gum/«mm;
`
`oo
`
`mm._..__.._
`
`4<>02mm
`
`0mm
`
`of
`
`KNEE
`
`0mm
`
`00
`
`#302mm
`
`BNQNV%
`
`0mm<muz_
`
`004
`
`awaimmom‘NI3.8
`
`Elma/2mBEE;
`
`Gum
`
`004
`
`Amaacém8m.N138
`
`Hoxma<zm8m
`
`32.23:
`
`o._OImmmIH
`
`WNQ
`
`QWQ
`
`99%
`
`mm<1a
`
`83:23:
`
`QJOIWMKIH
`
`mm<Ia
`
`OJOImMZIH
`
`.Qmfi
`
`WMW
`
`“WE
`
`0mm
`
`omm<muz_
`
`zo_._.<m3.r<m
`
`ZOF<30m
`
`Honfimm
`
`._<_mm_._.m<
`
`
`
`zopésimzop<~§<m
`
`Wmfi
`
`43mm;m<
`
`35
`
`35
`
`
`
`
`
`
`
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 34 0f 37
`
`6,081,735
`
`
`
`Im<m002m>lbmjmz<m._o
`
`mmmm>z_
`
`>>OQZ_>>
`
`zo:.oz:n_
`
`QQN
`
`“QR
`
`m._.<mmmfii
`
`Ezmhomam
`
`m_m>._<z<
`
`>>Ooz_>>
`
`ZO_._.oz:u._
`
`NQN
`
`QQN
`
`NMm/
`
`
`
`ZOP<mDH<m|_<_mm.E<
`
`FE20m...
`
`36
`
`36
`
`
`
`
`
`
`
`
`
`US. Patent
`
`Jun. 27,2000
`
`Sheet 35 0f 37
`
`6,081,735
`
`”b
`
`”6
`
`Sm) =S>\red(t)
`
`I
`
`”a
`
`
`
`270
`
`>
`
`27b
`
`§
`
`27c
`
`b / Swt) = 3MB“)
`
`
`
`37
`
`37
`
`
`
`US. Patent
`
`Jun. 27,2000
`
`Sheet 36 0f 37
`
`6,081,735
`
` I
`
`\
`;
`
`300
`
`30b
`
`l 306'
`
`t
`
`||
`
`I
`
`|[
`
`\
`
`
`
`38
`
`38
`
`
`
`US. Patent
`
`Jun. 27, 2000
`
`Sheet 37 0f 37
`
`6,081,735
`
`00”..
`
`‘1?wmELoEE;
`
`W23:35,:
`
`3:82.50 MmcEoEcmocoo
`
`acetoom08
`
`39
`
`R,6?.
`
`39
`
`
`
`6,081,735
`
`1
`SIGNAL PROCESSING APPARATUS
`
`REFERENCE TO PRIOR RELATED
`APPLICATION
`
`This is a continuation of application of US. patent
`application Ser. No. 08/859,837 filed May 16, 1997, which
`is a continuation of application of US. patent application
`Ser. No. 08/320,154 filed Oct. 7, 1994, now US. Pat. No.
`5,632,272 which is a c-i-p of US. patent application Ser. No.
`08/132,812 filed Oct. 6, 1993, now US. Pat. No. 5,490,505.
`
`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. If the
`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 cancilers, 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
`corresponding primary or secondary signal portions, they
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`40
`
`2
`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 s 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 s. 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 oximeter is a type of blood gas monitor which
`non-invasively measures the arterial saturation of oxygen in
`
`40
`
`
`
`6,081,735
`
`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 US. patent application Ser. No.
`08/132,812, 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 different 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 correlation canceler
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`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 oximetry 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 different 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 from
`the measured signals yielding a secondary reference which
`
`41
`
`41
`
`
`
`6,081,735
`
`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 coefficients.
`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