WO1995012349A1 - Mesure optique non invasive in vivo des proprietes d'un constituant de l'organisme humain ou animal - Google Patents

Mesure optique non invasive in vivo des proprietes d'un constituant de l'organisme humain ou animal Download PDF

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Publication number
WO1995012349A1
WO1995012349A1 PCT/NL1993/000233 NL9300233W WO9512349A1 WO 1995012349 A1 WO1995012349 A1 WO 1995012349A1 NL 9300233 W NL9300233 W NL 9300233W WO 9512349 A1 WO9512349 A1 WO 9512349A1
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light
intensities
wavelengths
wavelength
entry area
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PCT/NL1993/000233
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English (en)
Inventor
Reindert Graaff
Original Assignee
Aarnoudse, Jan, Gerard
Centrum Voor Biomedische Technologie Rijksuniversiteit Groningen
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Priority to PCT/NL1993/000233 priority Critical patent/WO1995012349A1/fr
Publication of WO1995012349A1 publication Critical patent/WO1995012349A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
    • A61B5/1464—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters specially adapted for foetal tissue
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
    • A61B5/14551—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters for measuring blood gases
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
    • A61B5/14551—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters for measuring blood gases
    • A61B5/14552—Details of sensors specially adapted therefor

Definitions

  • TITLE Optical, noninvasive, in-vivo measurement of properties of a constituent of a human or animal body
  • the invention relates to an optical method for noninvasive, in-vivo monitoring a property of a constituent, such as blood or tissue, of a human or animal body.
  • the invention also relates to a device, a probe and a driver/processor for carrying out that method.
  • pulse oximetry An example of a measuring method as identified above is pulse oximetry.
  • this method has become generally accepted for determining the arterial oxygen saturation (S a ⁇ 2 ).
  • S a ⁇ 2 the ratio of relative intensity fluctuations of light of different wavelengths which has passed through a portion of the body is used as an indicator for the S a ⁇ 2 -
  • the observed fluctuations are caused by pulsatile changes of the amount of arterial blood in the tissue into which the light has been emitted.
  • the principle underlying pulse oximetry is that the ratio of the relative intensity fluctuations at.
  • different wavelengths or wavelength ranges (generally red and infrared and therefore denoted as R/IR) is a function of the ratio of absorption coefficients of arterial blood for these wavelengths or wavelength ranges, which in turn depends on the S a ⁇ 2 .
  • R/IR red and infrared and therefore denoted as IR
  • Pulse oximetry is usually carried out by transmitting light through a relatively thin portion of the body, for example through an ear-lobe, a finger, a toe or a part of the nose.
  • a disadvantage of this method is that it cannot be used if suitable portions of the body cannot be reached. This problem occurs for example when it is desired to monitor the S a ⁇ 2 of a fetus during labour. Also when the patient suffers from circulatory problems or when artefacts are caused by motion of parts of the body available for attachment of the probe, the use of transmission pulse oximetry is impaired. In particular in such situations reflectance pulse oximetry is a more appropriate technique for monitoring the S a ⁇ 2 . In this technique, the intensity of light emerging from a part of the body is measured adjacent to the area where the light has been introduced into that part of the body instead of in a position diametrically opposite to the entry area.
  • a probe for carrying out this method comprises an emitter and a detector facing into essentially the same direction.
  • Such a probe can for example be held against the fetal scalp during labour or to any other accessible and free part of the body, provided that pulsations of sufficient magnitude can be detected at that location.
  • an intensity of light of a wavelength or wavelength range leaving the body in a second distance range from the entry area where the light has been introduced into the body is measured.
  • an estimate of the property to be monitored is determined from the measured intensities of light leaving the body in the first and second distance ranges from the entry area where the light has been introduced into the body.
  • reflectance pulse oximetry and laser Doppler flowmetry are carried out as separate independent measurements using an integrated sensor.
  • the problem occurs that optical properties of the tissue and fluids in that part of the body other than the properties to be measured influence the measurement result.
  • the average Doppler frequency measured during laser Doppler flowmetry which provides an indication of relative changes in blood flow - and in clinical practice of the blood perfusion in tissue immediately below the skin - is not only determined by the blood flow, but also influenced by the optical properties of the tissue and the blood which may vary between wavelength of the emitted light, between individuals and also between different measurement locations on the body.
  • the known empirical method described above does not provide for application in measurement techniques other than reflectance pulse oximetry.
  • this object is achieved by measuring the intensities of introduced light of at least two of the wavelengths or wavelength ranges leaving the body in the second distance range from the entry area where the light has been introduced into the body, and by using the measured intensities of the light of the two or more wavelengths or wavelength ranges in the second distance range from the entry area where the light has been introduced into the body for determining an estimate of the property to be monitored.
  • this object can also be achieved by measuring intensities of portions of the light of at least two of the wavelengths or wavelength ranges which has not been introduced into the body, and using the measured intensities of the other portions of the emitted light for determining an estimate of the property to be monitored.
  • the intensities of light of each of the at least two, mutually different wavelengths or wavelength ranges having travelled along different average path lengths through the body is detected.
  • the position of one or more additional areas or light emitters is chosen in such a manner, that the second distance range is different from the first distance range.
  • an additional detection area is positioned in such a manner that light reaching that area has not passed through the body, i.e. the average path length through the body is zero.
  • Methods according to the present invention can be used for taking into account specific optical properties of the tissue and/or the blood and/or variations thereof in the calculation of estimates of the property to be monitored.
  • the method according to the present invention allows to differentiate between variation of the absorption coefficient and the reduced scattering coefficient of the part of the body through which the detected light has propagated and therefore to design more universally applicable and accurate calibration procedures.
  • simultaneous calculation of an estimate of the reduced scattering coefficient and taking into account the estimated value thereof substantially improved the precision of estimates of the S a ⁇ 2 obtained by reflectance pulse oximetry.
  • the method according to the present invention can provide a possibility to correct for the influence of both the absorption coefficient and the reduced scattering coefficient for the wavelength at which the laser Doppler flowmetry is performed.
  • the observed average Doppler frequency is larger the lower the absorption coefficient and the higher the scattering coefficient is, because the average number of scattering events each detected photon has been subjected to decreases with an increasing absorption coefficient and increases with an increasing scattering coefficient.
  • a further advantage of the method according to the present invention is, that also correction factors for the average penetration depth of detected light of each wavelength or wavelength range become available. This is advantageous where the assumption of a homogeneous change of the blood volume fraction leads to unacceptable inaccuracies (e.g. if pressure is applied to the probe or if measurements are taken at the scalp) .
  • Particular advantages of the mode of the method according to the invention in which light leaving the body is detected at at least two different distance ranges from the area where the light has been introduced into the body are that also pulsatile fluctuations in the reduced scattering coefficient of arterial blood can be estimated and taken into account, so that also variations of this factor can be allowed for. Moreover, two different options to obtain estimates of this factor are made available.
  • a first option is to calculate the reduced scattering coefficient of arterial blood from determined or default values of the hematocrit and/or the plasma protein content.
  • the second option is to calculate the aforementioned factor by varying it, while keeping it identical for both distance ranges, until the estimates of the property to be monitored for both distance ranges are equal or within a predetermined range of each other.
  • the invention can also be embodied in a device, a probe or a driver/processor adapted for use in the measuring method according to the present invention.
  • Fig. 1 is a block diagram of a device according to the present invention.
  • Fig. 2 is a schematic bottom view of a probe according to the present invention.
  • Figs. 3-5 are consecutive parts of a flow chart of an algorithm for carrying out the present invention
  • Fig. 6 is a schematic side view in cross-section of a another probe according to the present invention.
  • Fig. 7 is a schematic bottom view of still another probe according to the present invention. DETAILED DESCRIPTION OF THE BEST MODE AND VARIANTS OF THE INVENTION
  • the device generally consists of a pulse oximetry driver/processor 1 and a probe 2 which is shown in more detail in Fig. 2.
  • the probe 2 shown in Fig. 2 which represents the presently most preferred embodiment thereof, has a diameter of about 18 mm. It comprises a red and an infrared LED 3 respectively 4 (Cerled types CR 10 MR respectively CR 10 IR; Electronic Consulting Services, Pfaffenhofen, Germany) for emitting light at wavelengths about 660 nm respectively about 940 nm.
  • the probe 2 further comprises a first and a second detector in form of photodiodes 5 respectively 6 (Siemens BPW 32) of which the first detector 5 is closer to the LEDs than the second detector 6.
  • Each of the detectors is capable of detecting light intensities at both wavelengths.
  • the probe has an internally black housing 7 to keep disturbing light away from the entry area and the exit area of the patient's skin where light is introduced into respectively received from the part of the patient's body adjacent the probe 2.
  • the separation wall 8 between the LEDs 3, 4 and the detectors as well as the inside of the probe 2 are also black to avoid transmission of light which has not passed through the skin from the LEDs to the detectors and to avoid re-entrance of light into the body.
  • the detectors 5, 6 and the LEDs 3, 4 have been fixed by filling the housing 7 with clear epoxy resin (e.g. EPOTEK 301).
  • the heart-to-heart distance between each of the LEDs 3, 4 and the first detector 5 is 4,8 mm.
  • this distance is 7,4 mm.
  • the largest LED to detector distance should not be more than 8 to 9 mm, since at greater distances apparently less reliable estimate of the optical properties of the skin and therefore of the S a ⁇ 2 have been obtained.
  • the maximum distance may also depend from the location at the body of the patient against which the probe is to be held. For use with animals other distances may be more suitable.
  • the distance of the LEDs 3, 4 to each of the detectors 5, 6 is mutually equal, but may also be different for example to achieve a more equal average penetration depth of reflected light of the two wavelenghts. An equal penetration depth is particularly important when measurements are taken from parts of the body of which the structure varies substantially with the depth beneath the skin, such as the head.
  • the probe 2 is connected to the driver/processor 1 via a cable 9. Means for cordless communication could be provided instead.
  • the pulse oximetry driver analyzer 1 is to a large extent identical to existing commercially available devices. It comprises a housing 10. In this housing 10 are provided a clock 11, which may for example provide a 2 Mhz output signal, an EPROM 12 for controlling LED drivers 13 and sample and hold circuits 14, amplifiers 15 interconnected with the detectors 5, 6 for amplifying signals received from the detectors 5 and 6. Preferably patient isolation according to customary standards is also provided.
  • the signals received from the amplifier 15 are demultiplexed by the sample and hold circuit 14 where also a constant signal caused by background illumination is subtracted from the received signal.
  • the driver/processor 1 further comprises logarithmic amplifiers 16, an analog/digital converter 17, a dataprocessor 18 and a display 19. Instead of or in addition to the display 19, a port for connecting display means such as a monitor or a plotter to the driver/processor may be provided.
  • the signals received from the sample and hold circuit 14 are logarithmically amplified by the logarithmic amplifiers 16 so after amplification the fluctuations are proportional to the relative fluctuations of the light intensities as detected. For determination of these relative fluctuations, signals are further amplified after high-pass filtering.
  • the avareage intensities are derived from the unfiltered output of the logarithmic amplifiers 16. All the aforementioned signals are converted to digital values by the analog/digital converter 17, for example into 12 bit digital values each 30 ms.
  • the digital values are inputted into the dataprocessor 18, which calculates estimates of the optical properties and of a value for the S a ⁇ 2 on the basis of the received signals and an algorithm.
  • the signals can also be processed in essentially the same manner or somewhat differently using a driver/processor with another structure.
  • Essential functional differences between the driver/processor according to the present invention and known driver/processors are, that the driver/processor according to the present invention is adapted for receiving and processing signals representing intensities of light of two or more wavelengths or wavelength ranges from two or more detectors (i.e. at least four different input signals) and programmed for calculating an S a ⁇ 2 value which is dependent from the relation between the signals generated by the different detectors.
  • the processor 18 is to be programmed on the basis of functions defining the relation between on the one hand the intensities and ratios between the fluctuations of light of different wavelengths at different detectors and, on the other hand, optical properties of the part of the body in front of the probe, tissue and/or the blood.
  • Light propagation in turbid media - e.g. skin tissue and blood - can be characterized by the following optical characteristics: an absorption coefficient ⁇ a , a scattering coefficient ⁇ g and a phase function which is the distribution of scattering angles per scattering event.
  • phase function is often characterized by the asymmetry factor g, which is defined as the average cosine of the scattering angles.
  • Predictions of light intensities at predetermined detectors can be obtained by carrying out Monte Carlo simulations for different values of the above-identified optical characteristics.
  • Monte Carlo techniques for simulating light propagation in turbid media are published in many earlier publications so the skilled person will generally be familiar with these techniques.
  • the intensity decay of a collimated beam of photons in a turbid medium equals the probability p t (z) that a photon has a free path with a length z:
  • I(z) is the intensity at a distance z from the location where the light enters the medium; ⁇ t is the transport coefficient. The chance that a photon travels within the collimated beam to a distance between z and z + dz can be found by differentiation of Eq. (1):
  • the Monte Carlo simulation comprises a repetition of the following sequence of steps. Firstly, a random number ⁇ is picked between 0 and 1 to determine l t . Secondly, a new random number is ⁇ is picked to determine whether the photon is absorbed or scattered. Thirdly, if the photon is scattered, then a scattering angle is picked from the phase function. If the photon has been absorbed simulation of the path of that photon is terminated. If the photon has not been absorbed, the three step sequence set out above is repeated until the photon is absorbed or leaves the medium. Each time new random numbers ⁇ are used. For reasons of efficiency, the photons may also be deemed to be absorbed if the number of interactions is very large, e.g. more than 20.000.
  • the Fresnel law can be used by picking a random number for each interaction to determine whether the photon is reflected or refracted.
  • the condensed Monte Carlo simulation described in that publication essentially consists of using the results of one Monte Carlo simulation for modelling light propagation in a situation in which the albedo c, the scattering coefficient ⁇ s or the absorption coefficient ⁇ a are different from the corresponding value used in the original performed Monte Carlo simulation.
  • the average depth of all interactions of detected photons can be calculated quickly if the average depth ⁇ d(l)> of each photon path has been stored too. If the simulated medium is semi-infinite and reflection from that medium is simulated, for each photon that has left the medium, the distance r(i) from the place of entry where that photon is deemed to have left the medium must also be available to determine the intensity in a predetermined area. If a slab has been simulated, it must furthermore be known for each photon that is deemed to have left the medium whether it is deemed to have been transmitted through the slab or to have been reflected back from the slab to determine the intensity in a predetermined area at the front or the back side of the slab.
  • the light distribution in the medium is the same in the simulation.
  • results from the condensed Monte Carlo simulations are implemented in the algorithm embodied by the signal processing software for each detector 5, 6 by determining a function relating the intensities of received light to the absorption coefficient ⁇ a and the reduced scattering coefficient ⁇ g ' .
  • this is carried out by determining coefficients of polynomials by fitting the polynomial to results of Monte Carlo or condensed Monte Carlo simulations for each detector separately.
  • These polynomials are independent from the wavelength and can for example be of the following form:
  • ln(I) Ao+A ⁇ a +A 2 ( ⁇ a ) 0 ' 5 +A3 ⁇ g , +A4ln( ⁇ s ')+A5 ⁇ g , ( ⁇ a ) 0 ' 5 +A6 ⁇ g ' 2 .
  • the processor 18 of a driver/processor for carrying out the method according to the invention is preferably programmed to carry out the algorithm described below with reference to Figs. 3-5.
  • the step denoted with reference numeral 20 comprises detecting and storing samples of the light intensities for red and infrared light and for both the first and the second detector 3, 4.
  • the samples are preferably taken with a high frequency (e.g. each 30 ms) and over a time interval which comprises at least one systole and diastole cycle. If light of the two wavelengths is emitted in an alternating sequence, values for different wavelengths of the same sample can be detected one shortly after the other. Instead of high frequency sampling, intensity values obtained at systole and diastole may be selected.
  • all measured intensities in a certain time-interval are stored temporarily. Subsequently, the intensity fluctuations are analyzed by means of linear regression analysis using samples of the signals over a time interval which is longer than the heart-beat cycle.
  • the data denoted by ln[Ii(R)] and ln[li(IR)] are used for obtaining ratios between intensities detected at different distances from the source.
  • the data denoted by ⁇ ln[Ii(R)] and ⁇ ln[I ⁇ (IR)] are used to analyze the intensity fluctuations.
  • the latter data are obtained after high-pass (e.g. 0.6 Hz) filtering and additional amplification of the signal (e.g. 20 times).
  • the ratio between the average intensities at the two detectors 5 and 6 are calculated from the stored values of ln[Ii(R)] and ln[Ii(IR)] as is denoted by steps 21 and 22.
  • the polynomials of the structure of Eq. (8) are used inversely to calculate the reduced scattering coefficient ⁇ g '(IR) from the ratio between the intensities at detectors 1 and 2, for example with an assumed non-pulsatile value for ⁇ a (IR) of 0.035 mm -1 as denoted by steps 23 and 24 (see Fig. 3).
  • Values of the pulse independent part of the reduced scattering coefficients for infrared light can then be determined as denoted by step 26.
  • the inverse algorithm using Eq. (8) is used to determine ⁇ a (R) from u s '(R) and l 2 /I ⁇ (R) as denoted by step 27.
  • Signal processing of the intensity fluctuations can be performed in several ways.
  • the optimal choise depends on many aspects, for instance, the signal to noise ratio of the signals at each detector, and whether the LEDs generate secondary emissions at other wavelengths.
  • a ,i( ⁇ ) and ⁇ s ,i'( ⁇ ) are the derivatives that are obtained in step 29 using Eq. (8) with the coefficients of the respective detector 1 and 2 (5 and 6, respectively in Fig. 2) .
  • the terms ⁇ a ( ⁇ ) and ⁇ g '( ⁇ ) are the absorption coefficient respectively the reduced scattering coefficient of the part of the body in front of the probe for wavelength ⁇ , as determined 5 in steps 21-28.
  • the values ⁇ a , a ( ⁇ ) and ⁇ s , a '( ⁇ ) are the absorption coefficient respectively the reduced scattering coefficient of arterial blood.
  • the multiplier ⁇ is optional
  • ⁇ a ( ⁇ ) and ⁇ g '( ⁇ ) can also be obtained 10 from a linear combination of ⁇ ln[I ⁇ ( ⁇ )] and ⁇ ln[l 2 ( ⁇ )].
  • step 31 the absorption coefficients for oxygenated and de-oxygenated blood are calculated using input values 15 determined in step 30 and the equations (11) and (12) set out below.
  • G Hb ( ⁇ ), G Hb02 ( ), Hb co( ⁇ ) and ⁇ i( ⁇ ) are the extinction coefficients of de- oxyhemoglobin, oxyhemoglobin, carboxyhemoglobin, and methemoglobin, respectively.
  • /a b co and /ai are the 35 molar fractions of carboxyhemoglobin and methemoglobin in the blood
  • c t , H b s the total hemoglobin content of the blood
  • the total hemoglobin content C t , Hb as well as the fractions Hbco and Hi can be determined in step 30.
  • the reduced scattering coefficients of arterial blood at each of the applied wavelengths only depend on the total hemoglobin content, which is obtained from step 30.
  • the reduced scattering coefficient of blood as denoted by step 32, for instance the following relation may be used:
  • M p ⁇ is a correction factor for the individual refractive index of blood plasma n p ⁇ which is influenced by the plasma protein content. This relation can be described as follows:
  • n avg is the normal refractive index of blood plasma.
  • the reduced scattering coefficient at other wavelengths can for instance be calculated using the following equation:
  • R ⁇ /IR ⁇ and R 2 /IR 2 , R 1 /R 2 and IR 1 /IR 2 are calculated from the light intensity data stored in step 20.
  • the calculated ratios are stored as set out in steps 33-36. All values may be obtained in a similar way as in commercially available pulse oximeter devices, for instance by analysis of the difference between minimum and maximum.
  • the slopes obtained by linear regression analysis of the light intensity data are used as is described below. Thereby, it is possible to use the whole signal or to select the inclinations and/or declinations during the systolic parts of the registrations, depending on the accuracy in the predicted saturation that can be obtained.
  • First estimates for R 1 /IR 1 and R 2 /IR 2 for each detector separately are obtained from the slopes b 1 .j R1 , bi R1-R1 , kR 2 .iR 2 ' and t>i R2 .R 2 in a linear regression analysis, where the data of ⁇ ln[I( ⁇ )] and ⁇ ln(I( ⁇ 2 )] are the independent variable by turns as denoted by step 33. Correlation coefficients and variances are also calculated.
  • b R1 . R2 , b ⁇ . R i, b IR1 . IR2 , and bu ⁇ .rai are the first estimates for R 1 /R 2 and IR 1 /IR 2 that are obtained in step 34, where the data of ⁇ ln[I ⁇ ( ⁇ )] and ⁇ ln(I 2 ( ⁇ )] are the independent variable by turns. Correlation coefficients and variances are also calculated.
  • step 35 The correlation coefficients and variances from step 33 and 34, which also denote the 'lack of correlation' for each detector, are used in step 35 for estimation of the contributions of uncorrelated signal by each of the signals, since the correlations between the red and infrared signals are not only determined by the arterial volume fluctuations, but for instance also by noise and venous volume fluctuations, which may differ for each of the input signals.
  • equations of the following form can be used:
  • R 2 R1,IR1 (I" - - - ⁇ ) (I" " ⁇ 2 ⁇ ) (15) ⁇ - ⁇ R i ⁇ R1 ⁇ R1 o ⁇ IR1
  • ⁇ 2 R ⁇ and ⁇ 2 ⁇ R ⁇ are the (total) variances of each signal
  • ⁇ 2 R1 . v and ⁇ 2 ⁇ R1 . v are uncorrelated parts of the variance caused by venous volume fluctuations
  • ⁇ 2 R j and ⁇ 2 iR 2 are tne uncorrelated parts of the remaining variances.
  • the uncorrelated part of the variance can be evaluated when it is assumed, firstly, that venous volume fluctuations do not alter the uncorrelated parts of the two signals obtained with the same wavelength, secondly, that the ratio between the remaining red and infrared noise amplitudes is the same for each detector, and, thirdly, that for each wavelength the ratio between the venous and arterial variances, for instance ⁇ 2 R1/V /(l- ⁇ 2 R1 ), has the same value ⁇ for both detectors. From these assumptions it can be concluded that the venous terms of the variance are absent in equations similar to Eq. (15) for determining the correlations between signals for the same wavelength at different detectors, as denoted by step 34.
  • Ri/IRi dln [ l ! ( IR) ] /d/ a ⁇ a , l ( R) d ⁇ a (R) /d/ a + ⁇ g , ⁇ ' (R)d ⁇ g ' (R) /d/ a
  • s ' are obtained from step 29.
  • Eq. (19) shows that a value for the multiplier ⁇ different from 1 may be given to correct for deviations from the assumed values. Such deviations may for example be caused by differences between the assumed and the actual plasma protein concentrations.
  • the multiplier ⁇ will then have the same value for all wavelengths.
  • the default value for ⁇ is one (1).
  • the multiplier ⁇ may also be determined from the measured values of R 1 /R 2 or IR 1 /IR 2 . In principle both results give the same value for ⁇ .
  • ⁇ corrects for deviations in the reduced scattering coefficients, but also for changes in the reduced scattering coefficient of blood during the pulsations, which may for example be caused by changes in red cell aggregation.
  • the presence of blood vessels may also influence R/IR if a fraction of the light pulsations is determined by blood within vessels of which diameters are not small compared to l/ ⁇ S/a '( ⁇ ) or l/ ⁇ a/a ( ⁇ ). In that event the changes d ⁇ a and d ⁇ g ' of the optical properties of the medium cannot be interpreted with Eqs. (18) and (19).
  • Pulsations can then me modelled as changes in the diameter of the blood vessel, which will influence the apparent absorption and reduced scattering coefficients. It is to be taken into account, that the reduced scattering coefficient is influenced by the absorption properties of blood, whereas in the model in which the medium is assumed to be homogeneous, the reduced scattering coefficient is not influenced by the absorption properties of blood.
  • Another option - provided for in the algorithm shown in the drawings - is to determine the values for A and/or A 2 from (condensed) Monte Carlo simulation data, based on the principle that the average depth from which the signal contributions occur should be equal for both wavelengths. To derive the average depths for each detector from condensed
  • step 38 the values for Ai and A 2 are derived.
  • the correction for the influence of depth dependent fluctuations of the arterial volume fraction for the red signal at the second detector 6 is obtained with
  • the initial value of ⁇ can be a fixed default value or be specified - for example obtained from Eq. (19) - as denoted by step 39.
  • step 41 it is checked whether the S a ⁇ 2 calculated with A 2 is within a predetermined tolerance range about the S a ⁇ 2 value calculated for A . If the value calculated for 2 is outside that tolerance range, then at step 43 the value of ⁇ is varied, the new value is read in step 39 and the calculations of step 40 are repeated with that new value of ⁇ . The cycle of steps 38-41 and 43 is repeated until the value calculated with 2 is within the specified tolerance range.
  • the most likely value for S a ⁇ 2 can be calculated from the two estimated values for the S a ⁇ 2 and the uncertainties in these properties.
  • steps may be carried out in a different order.
  • the step 37 in which the average penetration depth is determined may be carried out immediatley after the ⁇ a and ⁇ g ' have become available from step 28.
  • steps 33 to 36 in which the relations between relative fluctuations at different distance ranges and different wavelengths or wavelength ranges are analyzed, can be carried out immediately after the measuring step 20 and before analysis of the avarage intensities in steps 21 to 29.
  • steps 21-28 can be replaced by entering assumed or default values.
  • the measurement of relative fluctuations is not affected by the presence of obstacles in front of one or more of the detectors as long as sufficient light reaches the detectors. Measurement of the hematocrit and hemoglobin fractions will generally not appear opportune where normal values can be expected. In such situations steps 30 and 31 can be replaced by enetering assumed or default values.
  • FIG. 6 another probe according to the invention,is shown in a position against a body 110.
  • This probe comprises two LEDs 103, 104, a first detector 105 and a second detector 106.
  • the second detector is positioned at the side of the LEDs facing away from the side of the probe which is to be held against the skin.
  • Connection 109 comprises individual connections for each detector 105, 106 and for each LED 103, 104.
  • this probe is adapted for determining the ratio between light which has propagated through the skin and light which has reached the detector 106 without propagating through the skin.
  • ⁇ a and ⁇ g ' can be provided, so ⁇ a and ⁇ s ' can be determined for each wavelength using these ratios. These ratios can also be used in addition to ratios between light intensities at different distance ranges from the light source, so that less assumptions are needed and more variations of optical properties can be taken into account.
  • Fig. 7 still another probe according to the present invention is shown. In this probe two detectors 204 and 205 are provided. Detector 204 is adapted for detecting red light and detector 205 is adapted for detecting infrared light. For emitting red light LEDs 201, 202 at diferent distances from the detector 204 are provided.
  • LEDs 200, 203 For emitting infrared light LEDs 200, 203 at diferent distances from the detector 205 are provided. Alternating operation of on the one hand the LEDs 202, 203 close to the detectors 204, 205 and, on the other hand, the LEDs 200, 201 remote from the detectors 204, 205, provides the possibility to measure intensities of light leaving the body at different distances from the area where the light has been introduced into the body.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Biophysics (AREA)
  • Pathology (AREA)
  • Veterinary Medicine (AREA)
  • Biomedical Technology (AREA)
  • Optics & Photonics (AREA)
  • Medical Informatics (AREA)
  • Molecular Biology (AREA)
  • Surgery (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Pediatric Medicine (AREA)
  • Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)

Abstract

On introduit de la lumière de longueurs d'onde différentes dans une partie de l'organisme d'un sujet humain ou d'un animal, et on mesure les variations pulsatives de l'intensité de la lumière propagée dans cet organisme. On mesure, pour chacune d'au moins deux longueurs d'onde, les intensités de la lumière se propageant dans l'organisme et sortant de celui-ci à différentes distances de la zone d'entrée. On élabore à partir des intensités de lumière des évaluations des propriétés du tissu et/ou du sang en prenant en compte les propriétés du tissu et du sang qui influent sur les intensités de la lumière sortant de l'organisme. Ce procédé trouve application, par exemple, dans l'oxymétrie pulsée. On a également prévu un dispositif, une sonde (2) et une unité commande/processeur (1) utilisables dans ledit procédé.
PCT/NL1993/000233 1993-11-05 1993-11-05 Mesure optique non invasive in vivo des proprietes d'un constituant de l'organisme humain ou animal WO1995012349A1 (fr)

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Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999018844A1 (fr) * 1997-10-10 1999-04-22 Boston Scientific Corporation Systeme de spectrometre miniature
US6238348B1 (en) 1997-07-22 2001-05-29 Scimed Life Systems, Inc. Miniature spectrometer system and method
EP1453412A2 (fr) * 2001-12-06 2004-09-08 Ric Investments, Inc. Etalonnage adaptatif pour oxymetrie pulsee
EP1946697A1 (fr) * 2007-01-16 2008-07-23 CSEM Centre Suisse d'Electronique et de Microtechnique SA Recherche et Développement Dispositif pour surveiller la saturation du sang artériel en oxygène
US7684842B2 (en) 2006-09-29 2010-03-23 Nellcor Puritan Bennett Llc System and method for preventing sensor misuse
US8140148B2 (en) 1998-01-20 2012-03-20 Boston Scientific Scimed Ltd. Readable probe array for in vivo use
US8219170B2 (en) 2006-09-20 2012-07-10 Nellcor Puritan Bennett Llc System and method for practicing spectrophotometry using light emitting nanostructure devices
US8265724B2 (en) 2007-03-09 2012-09-11 Nellcor Puritan Bennett Llc Cancellation of light shunting
US8280469B2 (en) 2007-03-09 2012-10-02 Nellcor Puritan Bennett Llc Method for detection of aberrant tissue spectra
US8315685B2 (en) 2006-09-27 2012-11-20 Nellcor Puritan Bennett Llc Flexible medical sensor enclosure
US8364220B2 (en) 2008-09-25 2013-01-29 Covidien Lp Medical sensor and technique for using the same
US8521247B2 (en) 2010-12-29 2013-08-27 Covidien Lp Certification apparatus and method for a medical device computer
US8600469B2 (en) 2005-09-29 2013-12-03 Covidien Lp Medical sensor and technique for using the same
US8930145B2 (en) 2010-07-28 2015-01-06 Covidien Lp Light focusing continuous wave photoacoustic spectroscopy and its applications to patient monitoring
US8965473B2 (en) 2005-09-29 2015-02-24 Covidien Lp Medical sensor for reducing motion artifacts and technique for using the same
CN105324659A (zh) * 2013-06-11 2016-02-10 日本电气方案创新株式会社 光学单元和光学分析设备
US9351674B2 (en) 2005-03-03 2016-05-31 Covidien Lp Method for enhancing pulse oximetry calculations in the presence of correlated artifacts
EP3120770A3 (fr) * 2015-07-23 2017-02-22 Advantest Corporation Appareil de biodétection optique infrarouge et sonde de celui-ci
US9833146B2 (en) 2012-04-17 2017-12-05 Covidien Lp Surgical system and method of use of the same
US9895068B2 (en) 2008-06-30 2018-02-20 Covidien Lp Pulse oximeter with wait-time indication
JP2018051065A (ja) * 2016-09-29 2018-04-05 富士フイルム株式会社 内視鏡システム、プロセッサ装置、及び内視鏡システムの作動方法
JP6309659B1 (ja) * 2017-01-27 2018-04-11 フクダ電子株式会社 生体信号解析装置およびその制御方法
US10076276B2 (en) 2008-02-19 2018-09-18 Covidien Lp Methods and systems for alerting practitioners to physiological conditions
EP3593719A4 (fr) * 2017-03-08 2020-12-16 Kyocera Corporation Dispositif de mesure, procédé de mesure, et programme associé

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0280986A1 (fr) * 1987-02-23 1988-09-07 Sumitomo Electric Industries, Ltd. Appareil pour mesurer le métabolisme d'un tissu
EP0374844A1 (fr) * 1988-12-19 1990-06-27 Otsuka Electronics Co., Ltd. Méthode et appareil de mesure des caractéristiques d'une substance par dispersion de lumière
EP0380664A1 (fr) * 1987-07-24 1990-08-08 Terumo Kabushiki Kaisha Appareil servant a mesurer la concentration et la saturation en oxygene de l'hemoglobine
EP0442011A1 (fr) * 1990-02-15 1991-08-21 Hewlett-Packard GmbH Sonde, appareil et méthode pour la mesure extracorporelle du taux d'oxygène
WO1993011701A1 (fr) * 1991-12-12 1993-06-24 Vivascan Corporation Mesure non invasive de la teneur en hematocryte et hemoglobine par analyse optique differentielle______________________

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0280986A1 (fr) * 1987-02-23 1988-09-07 Sumitomo Electric Industries, Ltd. Appareil pour mesurer le métabolisme d'un tissu
EP0380664A1 (fr) * 1987-07-24 1990-08-08 Terumo Kabushiki Kaisha Appareil servant a mesurer la concentration et la saturation en oxygene de l'hemoglobine
EP0374844A1 (fr) * 1988-12-19 1990-06-27 Otsuka Electronics Co., Ltd. Méthode et appareil de mesure des caractéristiques d'une substance par dispersion de lumière
EP0442011A1 (fr) * 1990-02-15 1991-08-21 Hewlett-Packard GmbH Sonde, appareil et méthode pour la mesure extracorporelle du taux d'oxygène
WO1993011701A1 (fr) * 1991-12-12 1993-06-24 Vivascan Corporation Mesure non invasive de la teneur en hematocryte et hemoglobine par analyse optique differentielle______________________

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
G.DOUGHERTY ET AL.: "Design and evaluation of an instrument to measure microcirculatory blood flow and oxygen saturation simultaneously", JOURNAL OF MEDICAL ENGINEERING AND TECHNOLOGY, vol. 16, no. 3, May 1992 (1992-05-01), pages 123 - 128 *
R.GRAAF ET AL.: "Optical properties of human dermis 'in vitro' and 'in vivo'", APPLIED OPTICS, vol. 32, no. 4, 1 February 1993 (1993-02-01), NEW YORK US, pages 435 - 447 *

Cited By (30)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6238348B1 (en) 1997-07-22 2001-05-29 Scimed Life Systems, Inc. Miniature spectrometer system and method
WO1999018844A1 (fr) * 1997-10-10 1999-04-22 Boston Scientific Corporation Systeme de spectrometre miniature
US8140148B2 (en) 1998-01-20 2012-03-20 Boston Scientific Scimed Ltd. Readable probe array for in vivo use
EP1453412A2 (fr) * 2001-12-06 2004-09-08 Ric Investments, Inc. Etalonnage adaptatif pour oxymetrie pulsee
EP1453412A4 (fr) * 2001-12-06 2005-08-31 Ric Investments Inc Etalonnage adaptatif pour oxymetrie pulsee
US9351674B2 (en) 2005-03-03 2016-05-31 Covidien Lp Method for enhancing pulse oximetry calculations in the presence of correlated artifacts
US8600469B2 (en) 2005-09-29 2013-12-03 Covidien Lp Medical sensor and technique for using the same
US8965473B2 (en) 2005-09-29 2015-02-24 Covidien Lp Medical sensor for reducing motion artifacts and technique for using the same
US8219170B2 (en) 2006-09-20 2012-07-10 Nellcor Puritan Bennett Llc System and method for practicing spectrophotometry using light emitting nanostructure devices
US8315685B2 (en) 2006-09-27 2012-11-20 Nellcor Puritan Bennett Llc Flexible medical sensor enclosure
US7684842B2 (en) 2006-09-29 2010-03-23 Nellcor Puritan Bennett Llc System and method for preventing sensor misuse
EP1946697A1 (fr) * 2007-01-16 2008-07-23 CSEM Centre Suisse d'Electronique et de Microtechnique SA Recherche et Développement Dispositif pour surveiller la saturation du sang artériel en oxygène
US8265724B2 (en) 2007-03-09 2012-09-11 Nellcor Puritan Bennett Llc Cancellation of light shunting
US8280469B2 (en) 2007-03-09 2012-10-02 Nellcor Puritan Bennett Llc Method for detection of aberrant tissue spectra
US10076276B2 (en) 2008-02-19 2018-09-18 Covidien Lp Methods and systems for alerting practitioners to physiological conditions
US11298076B2 (en) 2008-02-19 2022-04-12 Covidien Lp Methods and systems for alerting practitioners to physiological conditions
US9895068B2 (en) 2008-06-30 2018-02-20 Covidien Lp Pulse oximeter with wait-time indication
US8364220B2 (en) 2008-09-25 2013-01-29 Covidien Lp Medical sensor and technique for using the same
US8930145B2 (en) 2010-07-28 2015-01-06 Covidien Lp Light focusing continuous wave photoacoustic spectroscopy and its applications to patient monitoring
US8521247B2 (en) 2010-12-29 2013-08-27 Covidien Lp Certification apparatus and method for a medical device computer
US9833146B2 (en) 2012-04-17 2017-12-05 Covidien Lp Surgical system and method of use of the same
US10335067B2 (en) 2013-06-11 2019-07-02 Nec Solution Innovators, Ltd. Optical unit and optical analysis device
CN105324659A (zh) * 2013-06-11 2016-02-10 日本电气方案创新株式会社 光学单元和光学分析设备
EP3009830A4 (fr) * 2013-06-11 2017-02-15 NEC Solution Innovators, Ltd. Unité optique et dispositif d'analyse optique
EP3120770A3 (fr) * 2015-07-23 2017-02-22 Advantest Corporation Appareil de biodétection optique infrarouge et sonde de celui-ci
JP2018051065A (ja) * 2016-09-29 2018-04-05 富士フイルム株式会社 内視鏡システム、プロセッサ装置、及び内視鏡システムの作動方法
JP6309659B1 (ja) * 2017-01-27 2018-04-11 フクダ電子株式会社 生体信号解析装置およびその制御方法
JP2018117968A (ja) * 2017-01-27 2018-08-02 フクダ電子株式会社 生体信号解析装置およびその制御方法
EP3593719A4 (fr) * 2017-03-08 2020-12-16 Kyocera Corporation Dispositif de mesure, procédé de mesure, et programme associé
US11666228B2 (en) 2017-03-08 2023-06-06 Kyocera Corporation Measuring apparatus, measuring method, and program

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