`
`
`
`olume 7 Number I janaary 1991
`
`CLINICAL SCIENCES CENTER LIBRI
`UNIVERSITY OF WISCONSIN
`50f] HIGHLAND AVE; MADISON. WI 53?
`
`I
`
`JAN 17199?
`
`—-—-___
`FIOIIIL .I;:..IIIIIAL III—IIIESDIIIETII
`LEEHI'"-.Ii-UGY_.IN_BHE$IH_ES|A
`
`,
`IIIINAL
`CLINICAL
`
`Originaf Articles
`
`
`
`
`NikflIdHS GI-rIIIeIIsIeI'II. MD, and Rflfl H. BIarkfl'IeaI‘, MD
`..
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`and MI'IIIIII'I L LrIIrI'III'. PIID
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`W. EIIgeIIIardr, Dr IIIed G. Carl Dr I'vaI. T. DI'erILs. DrIIIcrI.
`and K. Mam-III PIof Dr med
`Case Reports”I“. ”H. ..
`-I."i'.IIII 3.: “I
`
`=
`--.-III'
`'I.
`Takan Morioka. MD KI'onIIIIrI FIIjII' MD
`Show TobI'IIIarsn MD. Masashr' FII'IIEI'I’I, MD,
`f‘.’.'.‘I YMI'I'I'I S“""‘R.”..‘I'.II_MD
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`I‘Il'I'I I'II'JII-.
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`IFIJ I. fi'EiIIIU‘ITI'
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`s. K. GmIIIIII MD. IF/IIICS. Char"! A. MIIIIIIII, MD,
`Robrr.’ COOII._’I3IID,__I1IIrI AIIII“NB“I'dM'I'HmeI’C-LuMD
`|.‘."I.'."-.;!.
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`II-.II'I"1.II:-
`Wayne R. AIIdEIsIIII, AID,”IIIIIIJDIIII G_. _Brork- UIII_e, ITA(5A)
`.T‘Ifhmml,,NOIES.
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`.II‘.':31;
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`I-"II. :II .
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`-' 5:1... 1.5.5.":-=
`
`I'I'IIeIIaeIJ DeIIIIgII. _MD. _aIId Raga SIIadIIIeIII MS
`"
`
` '-'Ii
`John Bernard VIIIIIII'QIII', IUD rIIIII PaIrI'rk NeIIIIaIIrI Name. MD
`KaowingYour Momtormg qupment
`I.
`I
`1 I
`IIII.‘-.1..;--I..
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`
`A’Iflj’flal’d RaIIIsex III. MD. PIID
`CMew IIIIIieIICe
`Book;
`Workshop
`HI." - -.II
`JOIHIH. EIII’IIIHIFH MD and DaIII'rI W EdsaH I'IID
`Abstracts of Sciem‘Ific Papers
`
`".;-:I: 'l
`
`_-I-
`
`-‘.
`
`.
`
`:
`
`'Ia'I;
`
`Announcements
`
`1
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`APPLE 1011
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`30
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`35
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`39
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`42
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`49
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`'56
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`68'
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`34
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`A-IO
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`A716
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`1
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`APPLE 1011
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`

`
`JOURNAL OF CLINICAL MOMI'I'OIHIIlfl
`
`Volume 7 Number 1 january 1991
`
`JAN 17 1391
`EFFICIAL Jlillliliihl. OF THE SOCIETY FOR TEBHIOHJEY lil AHESTHESIA
`EDl'foilfti. tanner:
`H:
`tats
`Paul G. Barash. MD. New Haven. Connecticut
`N. Ty Smith, MD
`Charlotte Bell, MD. New Haven. Connecticut
`University of California. San Diego
`VA Medical Center
`jau E. W. Bencken, PhD. Eindhoven. The Netherlands
`San Diego. California
`Casey D. Blitt. MD. Tucson. Arizona
`jerry M. Calltins. MD. PhD. Phoenix. AZ
`Henry Casson. MD. Portland. Oregon
`jeffrey B. Cooper. PhD. Boston. Massachusetts
`D. Daub, MD. Karlsruhe. Germany
`Edward Deland, MD. Los Angeles. California
`Peter C. Duke. MD. Winnipeg, Manitoba. Canada
`joim H. Eichhom. MD, Boston. Massachusetts
`Erich Epple. PhD. Tiibingen. Germany
`A. Dean Forbes. Palo Alto, California
`
`j. S. Gravenstein, MD
`University of Florida College of Medicine
`Gainesville. Florida
`Allen R. Ream, MD
`Stanford University School of Medicine
`Stanford. California__ .
`Bi
`.
`['EEVIEW fiiiil TELEBOMMUHICEWIDHS EIJITill'l
`Frank E. Block. jr. MD. Columbus. Ohio
`In.
`.-li"ii$l‘lillTWE Eilll‘Gll
`Robert K. Kalwinsky
`P'
`' TSHEH
`Little, Brown and Company. Boston. Massachusetts
`Pi
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`The authors. editors. and publisher have exerted every effort to ensure that
`drug selection and dosage. as well as the description ofinsttunients and rec-
`ommendations for their use. set forth in all articles appearing in the journal of
`Clinimi Monitoring arc in accord with current rcconnncndations and practice
`at the time of publication. However. many considerations necessitate caution
`in applying in practice information reported in any article appearing in the
`Journal. These include ongoing research. changes in government regulations.
`variations in standards among different countries. the possibility that original
`research as reported in thcjourmi may differ from standard practice. and the
`constant flow of information relating to drug therapy and drug reactions. :is
`well as the principles of monitoring. application of instruments. and differ-
`ences in instruments among manufacturers. The reader is advised to check
`the package inserts for each drug for change in indication and dosage. and the
`descriptions provided by instrument manufacturers for added warnings and
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`The Journal afCiiHitai Monitoring is indexed in i'ndrx Merlin“. Current
`Cmnrmstiinimi Prarrirr. Exrtrpra Mrdim. and Current dummies: in
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`illogical Sttt'JKE'I.
`
`Wesley T. Frazier. MD, Atlanta. Georgia
`Yasuhiro Fukui. PhD, Hatoyama. japan
`Leslie A. Geddes. ME. PhD. FACC. West Lafayette, Indiana
`Nikolaus Gravenstein, MD. Gainesville. Florida
`A. Gerson Grecnburg, MD. PhD. Providence, Rhode Island
`Betty L. Grundy. MD, Gainesville. Florida
`H. j. Hartung. MD. Mannheim, Germany
`Carl C. Hug. jr. MD. Atlanta. Georgia
`Kazuyuki Ikeda. MD. PhD, Hamamatsu. japan
`joel Karlirtcr. MD. San Francisco. California
`john D. Michcnfclder. MD. Rochester. Minnesota
`P. M. Osswald. PhD, Mannheim. Germany
`Tsutomu Oyama, MD. Hirosaki. japan
`Carlos Parsloc. MD. Sao Paulo. Brazil
`jan Pefiaz. MUDr, CSc. Brno. Czechoslovakia
`james H. Philip, ME{E). MD. Boston. Massachusetts
`Richard E. Piazza. PhD. Bellevue, Washington
`Ellison C. Pierce. jr, MD. Boston, Massachusetts
`Cedric Prys-Roberts. MA. DM. PhD, FFARCS. Bristol. UK
`Michael L. Quinn. l’hB. San Diego, California
`in]. Rampil. MD. San Francisco. California
`Maynard Ramsey III. MD. Tampa. Florida
`Charles L. Rice. MD. Seattle, Washington
`Michael F. Roizcu. MD, Chicago. Illinois
`Helmut SChwildcn. MD. PhD, Bonn. Germany
`john W. Severinghaus, MD, San Francisco. California
`Lewis B. Sheiner. MD. San Francisco. California
`David B. Swedlow. MD, Hayward, California
`Richard Tepliek, MD. Boston. Massachusetts
`Kevin K. Tremper, PhD. MD. Orange. California
`Max H. Weil, MD. Chicago. illinois
`Arnold M. Weissler, MD. Denver. Colorado
`
`Karel H. Wesseling. PhD. Amsterdam. Holland
`
`2
`
`

`

`JOURNAL OF CLINICAL MONITORING
`
`Volume 7 Number 1 January 1991
`
`
`
`'A—Z
`
`Original Articles
`III VITRO EVALUATION OF RELATIVE PEHFDFIATIIIG POTENTIAL
`OF CENTRAL VENOUS CATHETERS: COMPARISON OF
`METEHIAL‘S. SELECTED MODELS. NUHBER OF LUMENS. Mil]
`ANGLES [IF INCIOEHCE T0 SIOIIJLATED MEMBRANE
`Nikolaus Craueusteiu, MD, and Robert H. Biaduheor, MD
`SKIN HEFLECTMIOE PULSE DXIMETRY:
`III
`'IilIIO MEASUREHEHTS
`FROM THE FOHEARM AND GALE
`Y. Me'ndeison, PhD, and M. J. McGimi, MS:
`_
`THE RELATIVE AOCUMCIES OF TWO AUTOMATED
`HOHIHVLSWE ARTERIAL PRESSURE MEASUREMENT DEVICES
`Michael S. Gorbdck, MD, Timothy J. Qm‘ii, MD,
`and Mirhaei L. Lovine, PhD
`ELECTROEHCEPHALDGMPHIC MAPPING OUHIHG ISOFLIJRAHE
`AHESTIIESIA FOII TflEflTflENT OF MENTAL DEPRESSION
`W. Engefltara‘t, Dr med, G. Cerf, Dr Med,
`T. Dierks, Dr med, and K. Mam-er, Prof Dr med
`
`Case Reports
`USEFUUIESS 0F EPIDUTIALLY EUDKED CORTICAL I’DTEHTIAL
`MONITORING DURING CERVICDMEDOLLAHT OUOMA SURGERY
`Tokato Moriako, MD, Kiyotako Fujit‘, MD,
`Shozo Tobimatsu, MD, Mososbi Fulani, MD,
`
`and Yoshiro Sakagudli, MD
`OAPIIDGMPHY FDR DETECTION OF ENOOBHOIIGHLAL
`HIGHATIOH OF Ml EILDOTRFICHEM. TLIDE
`S. K. Gandhi, MD, FFARCS, Chami A. Mitmhl', MD,
`Robert Coon, PhD, and Ann Bardeen-Hensdlei, MD
`(“TEEN PIPELINE SUPPEY FRILIIRE: A DDPIUG STMTEGT
`Wayne R. Anderson, MD, and joint C. Brock-Um; FFAfSA)
`
`'
`|
`.|
`
`Technical Notes
`A TARGET FEEDBOCK DEVICE FOR VENTILHTOITY MUSCLE
`TRAIHIIIO
`Michael }. Beiman, MD, and Rea-a Shadmehr. MS
`REDUCTION OF FRESH OAS FLOW P-EOUIHEHEHTS BY A
`CIRCLE-MODIFIED DMII BREATHING CIRCUIT
`john Benson!I Vairinlghi, MD, and Patrick Newiond Nance, MD
`
`Knowing Your Monitoring Equipment
`BLOOD PRESSURE MONITORING: AUTOMATED DSCILLOHETIUC
`DEVICES
`Maynard Ramsey III, MD, PhD
`
`Correspondence
`LOW PEHFIlSIOII PRESSURE DH INTEHHUPTIOH OF BLOOD FLOIKr
`SLIPPHESSES ELECTROEIICEPHALOGHAPHIG ACTIVITY?
`jorge Urzrm, MD
`REPLY
`Mark S. ScIteIIer and Brian R. jams
`MEASUREMENT OF ARTERIAL OXYGEN TENSION III THE
`HYPEFIBAFIIC ENVIRONMENT
`LindeII K. Weaver, MD
`
`fiEP‘LIf
`Dr. C. Ll'tseher
`
`Books
`COPHDGRAPHY III CLIHICM. PRACTICE
`
`‘
`
`J. S. Gravcnstein, MD, David A. Pauius, MD, MS, and
`Thomas 1. Hayes, BS
`B. Smaiitom, MD, PhD
`
`1'3
`
`23
`
`30
`
`35
`
`39
`
`42
`
`49
`
`56
`
`68
`
`68
`
`68
`
`69
`
`70
`
`Contents continued on page 11-4
`
`3
`
`

`

`Contents continued jam page 11-2
`
`Workshop
`71 CBHPII‘IEHHA'HBII 0F MESIHESIR IHFBHMR‘I'IDH
`MMAGEHE”
`john H. Eichhom, MD, and David W. Edsel}, MD
`Abstracts of Scientific Papers
`33 Tim Minion HDIIITBIIIIIB Tscuunmav BIHFEBEIIGE
`
`102 FIRST MlllflAL MEETING (IF THE SOCIETY FOR TECHNOLOGY IN I
`
`AHESTHESIA
`
`11-16 Announcements
`34 name more we EfllTllBS
`
`A-ID mmnmnuu sun cnmnlnmuas
`
`ms me some" FDB Tacnnnmev m AHESIHESIA
`
`A.“ INDEX TO nnvsansaas
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`A—4
`
`4
`
`

`

`This material may be protected by Copyright law (Title 17 U.S. Code)
`
`5
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`TERMOE‘OIL
`HEATER
`51L ICON'E
`RUBBER
`
`Fig l. (A) Frontal and (B) side nienis attire treated skin rty‘ler—
`tnnre pulse axinteter sensor. See textjrir explanation. R St IR
`LEDs = red and inflated light-entitling diodes.
`
`eludes an array ofsix identical photodetectors arranged
`symmetrically in a hexagonal configuration surround-
`ing two pairs of red (peak emission wavelength, 660
`nm) and infrared (peak emission wavelength, 930 um)
`light-emitting diodes (LEDs) [1]
`In another related
`study, we showed that by locally heating the skin under
`the sensor to a temperature above 40°C, it is possible to
`achieve a Four— to fivefold increase in the magnitude of
`the pulsatile component detected from the forearm, and
`thus significantly improve the detection reliability ofthe
`reflectance photoplcthysmograms 12]. The new optical
`reflectance sensor designed for this study combines the
`two features described above.
`
`
`SENSOR DESIGN
`
`reflectance sensor
`The teniperaturewcontrolled optical
`used in this study is shown in Figure 1. The major fea—
`ture of the optical layout design is the multiple photo-
`diode array, which is arranged concentric with the
`LEDs. This arrangement maximizes the amount of
`backseattcred light that is detected by the sensor. The
`technical details related to the design and geometric
`
`8 Journal qult'm‘mi Monitoring Vol 7 No I jammy 1991'
`
`company, are better reliability in critical care situations
`such as peripheral circulatory shutdown, less interferu
`ence from ambient light, and better accuracy because
`measurement from the forehead is relatively unsuscep-
`tible to motion artifacts.
`
`there are no commercially available re-
`Currently,
`flectance pulse oximeters for monitoring SaOz from lo-
`cations other than the Forehead. Therefore, the objective
`of this work was to investigate the feasibility ofrnoni-
`toring SaO; with a skin reflectance pulse oxirneter from
`two alternative and convenient locations on the body:
`the ventral side ofthe forearm and the dorsal side ofthe
`
`calf. Besides extending the clinical application of pulse
`oximetry, it appears also that reflectance pulse oximetry
`from peripheral tissues may have potential advantage in
`the assessment of local blood oxygenation after skin
`transplantation and regeneration Following inicrovascu-
`lar surgery.
`In this article, we describe preliminary in vivo evalua-
`tion ofa new optical reflectance sensor for noninvasive
`monitoring of $303 with a modified commercial trans-
`mittance pulse oximetcr. We present the experimental
`evaluation of this sensor in a group ot'10 healthy adult
`volunteers and compare SaOz measured with the reflec—
`tance pulse oximeter sensor, Sp03(r), with SaOa Inca-
`sured noninvasively From the finger by a standard trans-
`mittance pulse oximeter sensor. Sp03(t).
`
`IIEFLEB'I'lllIBE PULSE DXIMEiflY
`
`The principle of reflectance, or backseatter, pulse ox—
`imetry is generally similar to that oftransmittance pulse
`oximetry. Both techniques are based on the change in
`light absorption oftissuc caused by the pulsating arterial
`blood during the cardiac cycle. The pulsating arterioles
`in the vascular bed, by expanding and relaxing. mod-
`ulate the amount of light absorbed by the tissue. This
`rhythmic change produces characteristic photoplethys-
`mographic waveforms, two of which are used to mea-
`sure SaOZ noninvasively.
`Recently, we showed that accurate noninvasive mea—
`surements of SaOZ from the forehead can be made with
`an unheated reflectance pulse oximeter sensor [1]. The
`major practical limitation of reflectance pulse oximetry
`is the comparatively low-level photoplethystnograms
`recorded from low-density vascular areas of the skin.
`Therefore,
`the feasibility of reflectance pulse oximetry
`depends on the ability to design an optical reflectance
`sensor that can reliably detect sufficiently strong reflec—
`tance photoplethysmograms from various locations on
`the skin.
`
`In order to partially overcome this limitation. we
`have developed an optical
`reflectance sensor that
`in-
`
`6
`
`

`

`r'lrfendel'snn and r‘vIrCimi: Slain Rrjlrrmury Pulse Oxfmetry
`
`9
`
`configuration ofthe optical components were described
`recently by Mendelson et al [I]
`The heater consists of a
`ring—shaped (dimensions:
`30—min outside diameter;
`15—min
`inside diameter)
`therlnofoil resistive heating element (Ocean State Ther—
`motics, Smithfleld, RI). The thermofoil heater was
`mounted between the surface of the optically clear
`epoxy. which was used to seal the optical components
`ot'the reflectance sensor. and a thin [0.005 mm) match—
`ing brass ring. which facilitates better thermal conduc—
`tion to the skin. A miniature (dimensions: 2 X 5
`x l min) solid-state temperature transducer (AD 590,
`Analog Devices, Wilmington, MA) was mounted on
`the outer surface of the brass ring with the thermally
`sensitive surface facing the skin. The entire sensor as-
`sembly was potted in room—temperature vulcanizing
`silicone rubber to minimize heat losses to the surround—
`
`ing environment. The assembled sensor weighs approx—
`iniately 65 g. The sensor measures approximately 38
`mm in diameter and is 15 mm thick. The heater assemv—
`
`bly was separately interfaced to a temperature controller
`that was used to vary the temperature ofthe skin be—
`tween 35 and 45°C in ] i U. 1°C steps.
`
`
`SUBJECTS MID Mill-IDES
`
`Data Acquisition
`
`Each of the two heated optical reflectance sensors were
`separately interfaced to a temperature controller and a
`commercially available ACCUSAT (Dataseope Corp,
`Paramus, Nj) pulse oximeter [3].
`Two of the three ACCUSAT pulse oximeters were
`modified to function as reflectance pulse oxiineters. The
`modification, which was described in a separate study
`[1], included the adjustment ofthe red and infrared LED
`intensities in the reflectance sensors so that the reflec—
`
`tance photoplethysmograms were approximately equal
`to transmittance photuplethysmograms measured by a
`Standard transmittance sensor from an average size adult
`finger tip.
`The third ACCUSAT transmittance pulse oximeter
`was used as a reference to measure Sp02(t) from the
`finger tip. The specified accuracy of this transmittance
`pulse oximeter is i2.0% and i4.0% for 5210; values
`ranging between 70 and 100% and 60 and 70%, respec-
`tively [3]. The three pulse oximeters were adapted to
`provide continuous digital readouts of the AC and DC
`components of the red and infrared photoplethysmo—
`grams.
`
`Readings from each of the three pulse oximeters were
`acquired every 2 seconds through a standard RS—232C
`
`serial port interface using an AT&T 6300 personal com»
`puter. The conversions of the reflectance redfinfrared
`(RI'IR) ratios measured by the two reflectance pulse ox-
`imeters to SpOfir) were performed by using the cali—
`bration algorithm obtained in a previous calibration
`study in which measurements were made with a similar
`nonheated sensor from the forehead [1]
`
`In Viva Study
`
`The ability to measure Sp02(r) from the forearm and
`calf was investigated in vivo during progressive steady—
`state hypoxia in humans.
`Measurements were acquired from 10 healthy non-
`smoking male adult volunteers ofdifferent ages and skin
`pigmentations. The study was performed in compliance
`with the University of Massachusetts Medical Center’s
`review guidelines on human experimentation. Each
`volunteer was informed of the complete procedure :15
`well as the possible risks associated with breathing by-
`poxic gas levels. Each volunteer received monetary
`compensation for participation 'in this study. The sub-
`ject distribution included 1 East Indian, 3 Asians, and 2
`darkly tanned and 4 lightly tanned Caucasians. Their
`ages ranged from 22 to 37 years old {mean 1 SD, 27.5
`i 4.9 years). Measured blood hematocrits were in the
`range of 4D to 50.5% (mean 1 SD, 45.7 i 3.20/0).
`All instruments were allowed to warm up for at least
`30 minutes before the study. The transmittance sensor
`of the pulse oximeter was attached to the index finger.
`The reflectance sensors were attached to the ventral side
`
`of the forearm and the dorsal side ofthe calf by using a
`double—sided transparent adhesive ring. In cases where
`an abundance of hair prevented intimate contact be-
`tween the sensors and the skin,
`the contact was im-
`proved by loosely wrapping the sensor and the limb
`with an elastic strap. The temperature of each reflec—
`tance sensor was set to 40°C and remained unchanged
`throughout the entire study.
`A standard lead-l electrocardiogram and end-tidal
`carbon dioxide levels were continuously monitored by
`a Hewlett-Packard 78345A patient monitor (Hewlett-
`Packard, Andover, MA). Each subject was placed in a
`supine position. A face mask was tightly fitted over the
`subject's nose and mouth, and the subject was instructed
`to breathe spontaneously while we administered differ-
`ent gas mixtures of nitrogen and oxygen. The inspired
`gas mixture was supplied by a modified Heidbrink anes-
`thesia machine (Ohio Medical Products. Madison, WI).
`The breathing circuit of the anesthesia machine was
`equipped with a carbon dioxide scrubber (soda lime).
`The inspired oxygen concentration was adjusted be—
`tween 12 and 100% and was monitored continuously
`
`g
`
`7
`
`

`

`l
`
`1.6
`
`H N
`
`11/IR“announceRusso P (D
`
`0.4
`
`U
`
`1. 2
`D. 8
`,
`I]. 4
`RI IR TRENSMIT'I‘ANCE RATIO
`
`1. 5
`
`Fig 2. Comparison qfrrd/infiami (R/IR) ratios measured by (in:
`modified rtjlt’rmute pulse oxinmer (y axis) and iilt’ standard trans-
`urirmure pulser oxiulrrcr (.1: axis) during progressive steady-suite
`hypoxia in ‘10 healthy subjects. The solid line represents the best—
`filled linear regression iinrfor tin-forearm measurements. The lira-
`laen line represents the best—filled linear regression lint’for the tail
`measurements.
`
`
`
`RESULTS
`
`Normalized R/IR ratios and Sp02(r) values measured
`by the reflectance pulse oximeters from the forearm and
`calf of the 10 subjects were compared with the nor-
`malized RIIR ratios and Sp02(t) values measured simul-
`taneously by the transmittance pulse oximeter from the
`finger. A total of9'1 and 93 pairs ofdata points measured
`simultaneously from the forearm and calf, respectively,
`were used in the regression analysis, which provided the
`estimated slopes and intercepts of the linear regression
`lines. Each pair of data points represents a different hy—
`poxic level.
`Regression analysis of the normalized R/[R ratios
`measured from the reflectance pulse oximcters from the
`forearm and calf (y axis) versus the normalized RHR
`ratios measured simultaneously by the transmittance
`pulse oximetcr from the finger tip (x axis) is shown in
`Figure 2. The equations for the best-fitted linear regresF
`sion lines were y = — 0.05 + 1.02): (r = 0.94. SEE =
`0.08, p < 0.001) for the forearm and y = 0.04 + 0.87::
`(r = 0.88, SEE = 0.11, p < 0.001) for the calf.
`A comparison of 513030) readings from the reflec-
`tance pulse oximetcr (y axis) and Sp02{t) readings mea-
`
`10
`
`journal ofCiinimi Monitoring Vol 7 No ljmumry 1991‘
`
`throughout the study with an IL 408 (Instrumentation
`Laboratories, Lexington. MA) oxygen monitor, which
`was inserted in the inspiratory limb of the breathing
`circuit.
`
`Steady-«state hypoxia was gradually induced by low-
`ering the inspired fraction of oxygen in the breathing
`gas mixture. Initially,
`the inspired oxygen concentra—
`tion was changed in step decrements. each step pro-
`ducing approximately a 5% decrease in Sp02(t) as
`determined from the display of the ACCUSAT
`transmittance pulse oximeter. The inspired oxygen was
`maintained at each level for at least 3 minutes until the
`pulse oximeter readings reached a steady level (i.e.,
`5:102 fluctuations ofless than $390). When the inspired
`oxygen level reached 12%,
`the process was reversed.
`Thereafter, the inspired oxygen level was increased in a
`similar stepwise manner to 100%. Data were recorded
`during both desaluration and reoxygenation.
`All subjects tolerated the procedure well without ad-
`verse reactions. None of the subjects showed electrocar-
`diographic abnormalities before or after the study. Each
`subject was studied for approximately 1 hour.
`
`Data Analysis
`
`To avoid operator biases, the data from each pulse ox—
`imeter were acquired automatically by the computer
`and later subjected to the same statistical tests.
`For each step change in inspired oxygen, readings
`from the three pulse oximetcrs were averaged consecu—
`tively over a period of 20 seconds. Averaged readings
`from the 10 subjects were pooled and a least-squares
`linear regression analysis was performed. Student's r test
`determined the significance of each correlation; p <
`0.001 was considered significant.
`Although the correlation coefficient of the linear re-
`gression (r) provides a measure of association between
`the SPOg(l’) and Sp03(t) measurements, it does not pro—
`vide an accurate measure ofagreement between the two
`variables. Therefore, the measurement accuracy was es-
`timated on the basis ofthe mean and standard deviations
`
`of the difference between the readings from the trans—
`mittance and reflectance pulse oximeters. The mean of
`the difference between the pulse oximeter measure-
`ments, which is often referred to as the bias, was used to
`assess whether there was a systematic over- or underes-
`timation of one method compared with the other. The
`standard deviation ofthe bias, which is often referred to
`as the precision, represents the variability or random
`error. Finally, We computed the mean errors and stan—
`dard deviations of each measurement. The mean error
`
`is defined as the absolute bias divided by the corre-
`sponding Sp02(t) values.
`
`8
`
`

`

`Mrnrietson and McCinn: Skin Reflectance Pulse Oxintetry
`
`11
`
`100
`
`
`
`
`
`nausea-mes:33:02(a)
`
`03C3
`
`in C3
`
`
`
`FORIRRH
`y I 1.09: - 7.06
`CAL?
`Y I 0.93x + 7.78
`
`70
`
`EU
`
`90
`
`100
`
`70
`
`an
`
`on
`
`1 oo
`
`Tmsurmmcr: 51302 (is)
`
`ramsurmmca 85:02 (a: )
`
`Fig 3. Comparison ofpercent arteriai hemoglobin oxygen satura-
`tion (SpOz) measurements obtaincdfiorn the modified reflectance
`prtlse oxitneter {)1 axis) and SpOz values measured by a standan‘l'
`transmittance pulse oxinteter {x axis) a'nring progressive steady-
`state hypoxia in 10 healthy subjects. The solid line represents the
`bestzfirteci linear regression line fiar ritejbreartn measurements. The
`broken line represents the best-fitted linear regression iincfin' the
`calf measurements.
`
`DIFFERENCES
`
`7D
`
`30
`
`90
`
`100
`
`TRANSMITTANCE Spoz (Qt)
`
`Fig 4. Mean difl‘orenres between arterial hemoglobin oxygen sat—
`uration (Sp02) tneasnredfiont the Jforearm by the modified reflec-
`tance pulse oxirneter and the standard transmittance pulse oxitneter
`ntrosurements fiont the finger tip.
`
`Fig 5. Mean difliererices between arterial. hemoglobin oxygen sat-
`uration (SpOg) measured from the calf by the motif ed reflectance
`pulse oximeter and the standard transmittance pnise axinteter mea-
`surements fiom the finger tip.
`
`Statistical Analysis of Arterial Oxygen Saturation ($1102) Levels
`Meamrea'fiom the Forearm and Calf by the Modified Reflectance
`Pulse Oxfnteters
`
`Locationt‘
`"/a 5302
`
`No. of
`Data Points
`
`Mean Value (SD)
`
`Difference
`
`”/0 Error
`
`Forearm
`90—100
`80~89
`70—79
`Calf
`90-100
`80—89
`70—79
`
`42
`37
`12
`
`43
`33
`17
`
`1.25 (2.55)
`0.52 (2.85)
`70.82 (1.96)
`
`2.47 (1.66)
`2.35 (2.45)
`2.42 (1.20)
`
`3.36 (3.06)
`1.57 (4.00)
`3. 45 (4.12)
`2.22 (4.00)
`
`1.95 (2.42) 2.97 (2.75)
`
`sured simultaneously from the transmittance pulse: ox—
`imctcr (x axis) is shown in Figure 3. The: equations for
`the best—fitted linear regression lines were y = — 7.06
`+ 1.09): (r = 0.95, SEE = 2.62, p < 0.001) for the
`forearm and y = 7.73 + 0.93x (r = 0.88, SEE = 3.73,
`p <1 0.001) for the: calf.
`Figures 4 and 5 show the percent differences between
`Sp02(r) and Sp02(t), that is, Sp02(r) — SpOfit). ob-
`tained From the: forearm and calf data plotted in Figure.-
`3. respectively. The corresponding means and standard
`deviations of the differences and errors for the Forearm
`and calf measurements are summarized in the Table.
`
`9
`
`

`

`[2 Journal ofClr'niml Allariitririitq Vol 7 No 1 jammr'y 1991'
`
`Data were summarized for three different ranges of
`SpOglt) values between 70 and 100%.
`
`IllSllllSSlllll
`
`Commercially available transmittance sensors can be
`used on only a limited number of peripheral locations of
`the body. Brinkman and Zijlstra [4-] and Cohen and
`Wadsworth [5] showed that instead of tissue transil-
`lumination, noninvasive monitoring of 8302 can be
`performed based on skin
`reflectance
`spectropho-
`tometry. More recently. we described an improved
`optical reflectance sensor that was used for measuring
`SaOz from the forehead with a modified commercial
`transmittance pulse oximcter [l ].
`Measuring large reflectance photoplethysmograms
`from sparsely vascularized areas ofthe skin is challeng-
`ing. Differences in capillary densities between various
`locations on the body are known to affect the magnitude
`and quality of the reflected photoplcthysmograms. For
`example, estimated average capillary density of the hu-
`man forehead is approximately 127 to 149 loopsr'mmP‘,
`whereas the capillary densities of the forearm and calf
`are approximately 35 to 51 and 41 loops/mmz, respec-
`tively [6,7]. Furthermore. the frontal bone of the forc~
`head provides a highly reflective surface that signifi-
`cantly increases the amount of light detected by the
`reflectance sensor. Therefore.
`reflected photoplethys—
`mograms recorded from the forehead are normally
`larger than those recorded from the forearm and calf.
`Local skin heating could he used as a practical method
`for improving the signalutounoise ratio of the reflected
`photoplethysmograms from the forearm or calf areas
`and thus reduce the measurement errors in reflectance
`
`pulse oximetry.
`The approach presented in this article demonstrated
`that 5302 can be estimated by using a heated skin
`reflectance sensor from the forearm and calf over a rela—
`
`tively wide range of 5302 values. This technique may
`provide a clinically acceptable alternative to currently
`available transmittance pulse oximetcrs. In a previous
`study [2}, we found that the ability to measure accurate
`SaOZ values with a reflectance skin oximcter is indepen—
`dent of the exact skin temperature. We noticed, how-
`ever,
`that a minimum skin temperature of approxi—
`mately 40°C is generally sufficient to detect adequately
`stable photoplethysmograms. Furthermore. our experi-
`ence in healthy adults also has shown that at this skin
`temperature, the heated sensor can remain in the same
`location without any apparent skin damage.
`Note that despite the proven advantage oflocal skin
`heating to increase skin blood flow. reflected photo-
`plethysmograms recorded from the forearm and the calf
`are considerably weaker than those recorded from the
`
`the mean errors for the SpOg(r)
`forehead. Therefore,
`measurements from the forearm and calfare higher than
`the corresponding errors for similar SpOg(r) measure-
`ments made with an unheated reflectance sensor from
`
`the forehead. For comparison, relative to 5:103 mea-
`sured with a noninvasive transmittance pulse oximeter.
`the SEE for Sp02(r) measurements obtained from the
`forehead using a similar unheated optical reflectance
`sensor were 1.82% ill. The SEE obtained in this study
`using the heated reflectance sensor were 2.62% for the
`forearm and 3.73% for the calf measurements. Despite
`those differences, it is apparent that the degree ofcorre-
`lation obtained in this preliminary Study is encouraging
`and in selected clinical applications may be aCCeptable.
`We conclude that reflectance pulse oximetry from the
`forearm and calf may provide a possible alternative to
`conventional transmittance pulse oximctry and reflec-
`tance pulse oximetry from the forehead. Further stud-
`ies, however, are needed in order to compare our
`reflectance pulse oximeter against 530; measurements
`obtained directly from arterial blood samples. Addi-
`tional work to investigate the source of variability in
`reflectance pulse oximetry is in progress.
`
`Financial support for this study was provided in part by the
`Datascope Corporation and NIH Grant Rlfi GM36lll-UIA1.
`The authors would like to acknowledge the clinical assistance
`of Albert Shahnarian, PhD, Gary W. Welch MD, PhD. and
`Robert M. Giasi. MD. Department of Anesthesiology. Uni—
`versity of Massachusetts Medical Center. Worcester, MA.
`We also thank Paul A. Nigroni. Dalascopc Corporation.
`Paramus. NJ, and Kevin Hines. Semiconductor Division.
`Analog Devices, Wilmington. MA. for technical assistance.
`The skillful art work by Yi Wang is also greatly appreciated.
`
`1. Mendelson Y. Kent jC, Yocum BL, Birle M]. Design and
`evaluation of a new reflectance pulse oximetcr sensor.
`Biomed lnstrum Techno] l988;22(4):167—l73
`2. Mendelson Y. Ochs BD. Noninvasive pulse oximetry
`utilizing skin reflectance photoplethysmography.
`IEEE
`Trans Biomed Eng 1988;35(10):798—805
`3. Mendelson Y, KentJC, Shahnarian A, et al. Evaluation of
`the 'Datascope ACCUSAT pulse oximeter
`in healthy
`adults. J Clin Monit 1988;4z5'J—(13
`4. Brinkman R. Zijlstra WG. Determination and continuous
`registra