EP2004043A1 - Procédé de détermination continue non-invasive de la concentration de composants sanguins - Google Patents

Procédé de détermination continue non-invasive de la concentration de composants sanguins

Info

Publication number
EP2004043A1
EP2004043A1 EP08735450A EP08735450A EP2004043A1 EP 2004043 A1 EP2004043 A1 EP 2004043A1 EP 08735450 A EP08735450 A EP 08735450A EP 08735450 A EP08735450 A EP 08735450A EP 2004043 A1 EP2004043 A1 EP 2004043A1
Authority
EP
European Patent Office
Prior art keywords
radiation
wavelength
absorption
concentration
examined
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP08735450A
Other languages
German (de)
English (en)
Inventor
Thomas Hübner
Michael Alt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Enverdis GmbH
Original Assignee
Enverdis GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE200710014583 external-priority patent/DE102007014583B3/de
Application filed by Enverdis GmbH filed Critical Enverdis GmbH
Priority to EP08735450A priority Critical patent/EP2004043A1/fr
Publication of EP2004043A1 publication Critical patent/EP2004043A1/fr
Withdrawn legal-status Critical Current

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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
    • A61B5/14546—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 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
    • 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

Definitions

  • the invention relates to methods for the continuous noninvasive determination of the concentration of blood constituents.
  • Hemoglobin again has four other constituents:
  • composition of human blood is exemplified in FIG.
  • the invention can also be used to determine the concentration of other blood components. All the features mentioned in connection with hemoglobin can thus also be used to measure the concentration of other blood components.
  • the Hb photometer has a capillary gap filled with a chemical reagent.
  • a small amount of blood for example a drop of blood, is supplied to this capillary pasit and changes its translucency due to the chemical decomposition that has occurred.
  • the change in the light transmittance can be detected photometrically.
  • Such a device has the disadvantage that the patient must be removed for checking the Hb value blood.
  • US 6,104,938 describes a method for determining the concentration of blood components on the basis of an evaluation of the intensities of the transmitted or reflected light of a body part with different wavelengths.
  • the illustrated calculation method is only applicable to transmitted or reflected portions of the light, but not for their combined consideration.
  • the object of the invention is to provide a method for the non-invasive determination of the concentration of a particularly comparatively large number of blood constituents.
  • the object is achieved according to the invention by the features of claim 1.
  • a method of determining the concentration of blood constituents comprises the following steps
  • the starting point for the method according to the invention is a device which is suitable for emitting a plurality of measuring beams with respectively different wavelengths.
  • the apparatus further comprises a first light receiver for receiving the measurement radiation reflected by a body part to be examined.
  • a second light receiver for receiving the transmitted through the body part to be examined is Measuring radiation provided.
  • your body part to be examined may be a human finger.
  • measuring radiation it is possible to use electromagnetic radiation, such as, for example, light in the visible range and / or infrared radiation in the near infrared range. Particularly preferred is the use of a device as described in patent application filed by the Applicant "Apparatus for Determining Concentrations of Blood Components".
  • the invention is based on the idea that the various constituents of the blood, for example hemoglobin and water, absorb radiation to varying degrees.
  • the various constituents of the blood for example hemoglobin and water
  • absorb radiation to varying degrees.
  • the concentration of different Blut sauteiie can be determined with a suitable choice of wavelength used on the basis of the measured absorbance with the help of further calculations.
  • the wavelengths of so-called isosbestic points can be used, in which the Blut josteiie have the same degree of absorption.
  • a radiation source to emit different wavelengths thus allows a particularly accurate measurement of the concentration of different blood components, since a measurement can be made precisely at those wavelengths in which particularly striking differences in absorption occur.
  • the following wavelengths have proven to be particularly advantageous for measuring the hemoglobin derivatives:
  • the optical window for the skin is taken into account in the selection of the wavelengths used. This is for human skin in a wavelength range of about, 350 nm to 1650 nm.
  • the method preferably comprises storing the determined absorption values of each wavelength and repeating the previously mentioned method steps, wherein the determined absorptances of each wavelength are stored for each recovery cycle. Subsequently, a summary of the individual absorption values of emitted radiation for each Weüenide to represent a time course of the absorption at each wavelength. This representation can take place, for example, in the form of a curve or in the form of a table.
  • wavelengths are used. If, for example, the concentration of the four hemoglobin derivatives mentioned at the outset as well as the water in the blood are to be determined, it is necessary to use at least five different wavelengths. In order to enable a more accurate measurement, it may be useful to measure the intensity at other wavelengths, for example at a total of eight wavelengths.
  • Possible methods for determining the concentration ratios of the constituents of the blood are, for example, the determination by means of linear equation systems, a determination with the aid of a heuristic algorithm and the determination by means of correlation. These methods are explained in more detail in the exemplary embodiments of the present application.
  • the low point of a curve is required in order to then determine the difference to the maximum of the curve (diastole), otherwise the DC component can not be considered.
  • the area integrals can be used as a ratio to one another as input data for the calculation algorithm.
  • a mixed signal (sum volume pulse) is obtained from the absorption of all blood constituents.
  • concentration ratios of the blood components to each other can be determined with the aid of the discrete substance and wave length-specific extinction coefficients.
  • the extinction coefficients can refer to both the amount of substance per volume and the mass per volume. Consequently, the ratios to be calculated correspond to either the mass ratios or the volume ratios of the individual blood constituents per volume,
  • the device preferably has a calculation device connected to the first and the second radiation receiver for calculating the absorption of the emitted radiation by the body part to be examined Radiation based on the measured reflected and transmitted radiation component.
  • the calculation device may be, for example, a computer.
  • the calculation of the absorption of the emitted radiation by the body part to be examined can take place in particular in the calculation device in such a way that an interaction of the calculation device with the body part to be examined is not required.
  • the calculation device can be designed as a device on which a specific software program runs.
  • the radiation source and the first radiation receiver for receiving radiation reflected by the body part to be examined on the same side of the body part to be examined.
  • the second radiation receiver for receiving the transmitted radiation can then be arranged opposite the first radiation receiver on a second side of the body part to be examined.
  • the radiation source comprises a plurality of individual radiation sources of different wavelengths.
  • the individual radiation sources can be designed, for example, as LEDs, laser diodes or white light LEDs with filters. This feature is particularly advantageous since different hemoglobin derivatives at certain wavelengths have particularly marked differences in the absorption coefficient of the emitted radiation. It is particularly advantageous to use for measuring these wavelengths, in which the difference in the degree of absorption of various hemoglobin derivatives or other blood components, such as water, is particularly large.
  • the device is designed such that the first and the second radiation receiver are arranged opposite one another, so that between the first and the second radiation receiver, a receiving space for receiving the body part to be examined is formed.
  • the radiation source and the first radiation receiver can be arranged in one plane.
  • the radiation source as a light source, for example by LEDs
  • the first and second radiation receivers as light receivers, for example as photodiodes.
  • the LEDs may be arranged, in particular in a circle around the first light receiver, on the first side of the receiving space.
  • a particularly uniform illumination of the body part to be examined can be achieved in that the radiation element has at least two individual light sources of the same wavelength, which are arranged diametrically. If, owing to a large number of wavelengths used, it is not possible, owing to the construction, to arrange two individual light sources of the same wavelength diametrically, it is also possible to work with one single source of light per wavelength. In this context, it is particularly preferred that the side of the individual light sources facing away from the first light receiver is, in particular, at an angle! of 15 °, so that the emitted radiation of the single light sources meets at a point where the body part to be examined, such as a human finger, is located.
  • the first and second light receivers are in particular of the same type and may be designed, for example, as photodetectors.
  • a two-color detector is preferably used. This points to the example! a silicon receiver surface having a wavelength range of 400 nm to 1100 nm, and, for example, an indium gallium arsenide receiver surface having a wavelength range of 1000 nm to 1700 nm.
  • a detector with, for example, three receiver surfaces of different material. It is important that the total range from 350 nm to 1650 nm can be recorded.
  • the light source is separated from the first light receiver by a separating device, in particular by an impermeable inner and outer sleeve.
  • the inner wall of the outer sleeve is provided with a white coating to homogenize the light to be emitted.
  • the sleeve can be conically shaped, so that the radiation can be irradiated on a defined surface (corresponds approximately to the area of a fingertip). It is furthermore conceivable that, in particular, the reflection sensor has two receivers located close to one another in order to take account of interference factors which can be derived from the difference of the two signals obtained (tissue, scattering, etc.).
  • the sleeves can be firmly glued to the light source and the first light receiver.
  • the cavities lying between the sleeves can be filled with a, in particular transparent, scratch-resistant, hard and / or biocompatible adhesive.
  • the adhesive can be slightly curved inwards (concave) with the sleeve.
  • the transmittive radiation receiver is arranged.
  • the device may have a first and a second receiving element, which limit the receiving space on its first and second sides respectively.
  • the first and the second Auf ⁇ ahmeelement be connected by a clamping mechanism with each other such that attachment of the device to the body part to be examined, such as on a finger, can be done.
  • first and the second radiation receiver are particularly preferred to store the first and the second radiation receiver in a floating manner, so that optimum contact with the body part to be examined is ensured and a consistent, reproducible contact pressure can be achieved.
  • first and the second radiation receiver abut directly on the body part to be examined or on the coupling medium.
  • a fiber optic cable for optical coupling between the LEDs and the skin or between the skin and the receiver surfaces in order to focus the light on the smallest possible measuring area.
  • the device according to the invention can be designed such that an automatic continuous tracking of the radiation intensity of the radiation sources, for example the transmission LEDs, takes place per channel used. If the output signal is too small or too large, the transmission power is automatically amplified or attenuated. This factor must be quantitatively reproducible in order to be able to include it in the evaluation of the signal.
  • the same principle can also be applied to the intensity of the radiation receiver, in particular the two-color detectors. Thus, for example, there can be eight readings for the eight LEDs used (eight wavelengths) and four readings for the detectors used (transmissive and reflexive, in each case for two receiver surfaces).
  • the device according to the invention can be used for a variety of applications.
  • the described device for the continuous non-invasive determination of the hemoglobin concentration is possible.
  • a use of the device for determining microvascular damage is possible.
  • Another possible use relates to the continuous noninvasive determination of blood pressure.
  • the device according to the invention can be used for further, in particular also diagnostic or medical methods.
  • the device according to the invention is suitable for determining a volume pulse rate of one or more blood constituents.
  • a volume pulse rate of one or more blood constituents From the determined VolumenpulsverSäufen and in particular from the form of a volume pulse course further medical findings, such as the blood pressure of a patient or information on the presence of microvascular damage can be derived.
  • the volume pulse rate of a single blood component may be determined using a single wavelength.
  • the measured course of the absorption at the wavelength used corresponds to the volume pulse rate of the blood constituent to be determined.
  • the choice of the wavelength used must be made according to the criteria already described.
  • An independent invention relates to a method for operating a device for determining concentrations of various blood constituents.
  • an apparatus as described in the present application can be used.
  • the device has at least one radiation source which is suitable for emitting a plurality of measuring radiations of different wavelengths.
  • the radiation source is switched on in particular sequentially to emit a measuring radiation having in each case one wavelength. This means that the radiation sources are like this is driven, that they each emitted a measuring radiation with a certain wavelength.
  • the radiation source can be formed from a plurality of individual radiation sources, such as LEDs, for emitting a measurement radiation having in each case one wavelength.
  • a straightening source may be provided which is suitable for the simultaneous emission of measuring radiation of different wavelengths.
  • the first and second radiation receiver used here must be designed in such a way that they are suitable for separately receiving the measuring radiation of the individual emitted wavelengths. This can be realized, for example, by providing a plurality of single-line receiver devices, each of which receives a specific frequency band of the emitted radiation, for example with the aid of a frequency filter. However, it is preferable that each wavelength is emitted sequentially.
  • the measurement radiation of each wavelength reflected by a body part to be examined is received by a first radiation receiver. Furthermore, receiving the transmitted by the body part to be examined measuring radiation of each wavelength by a second radiation receiver. Subsequently, the absorption of the emitted radiation by the part of the body to be examined is determined for each wavelength. This determination is made on the basis of the measurement of the reflected radiation by the first radiation receiver and the measurement of the transmitted radiation by the second radiation receiver.
  • the method according to the invention can have all the features which have been described in connection with the device according to the invention.
  • the method preferably comprises storing the determined absorbance values of each wavelength and repeating the previously mentioned method steps, wherein the ascertained absorption values of each wavelength are stored for each repetition cycle.
  • the individual absorption values of the emitted radiation for each wavelength are summarized to show a time profile of the absorption at each wavelength.
  • This representation can take place, for example, in the form of a curve or in the form of a table and is referred to as a volume pulse profile.
  • the method according to the invention can comprise the following steps:
  • the method steps d and f take place in a calculation device in such a way that the calculation device has no interaction with the body part to be examined.
  • 1 is a view of the composition of human blood
  • Fig. 2 is a schematic representation of a suitable
  • Fig. 3 is a graphical representation of the penetration depth optical
  • Fig. 4 is a graph of the absorption spectrum in human blood in a normal
  • Fig. 5 is a graph showing a comparison of a normal absorption spectrum and a
  • Fig. 6 is a graph of the absorption spectrum of
  • Fig. 8 is a schematic representation of the control of several
  • FIG. 9 is a schematic representation of the readout behavior of FIG.
  • 11 is a schematic representation of a calibration device for the reflective radiation receiver
  • 12 shows a schematic representation of a calibration device for the transmissive radiation receiver
  • FIG. 15 a flow chart for concentration determination according to a linear system of equations
  • Fig. 17 is a schematic representation of a
  • Fig. 18 is a schematic representation of the first
  • Fig. 19 is a sectional view of the first
  • Figs. 20 and 21 are a graphical representation of the detector areas of the radiation receivers.
  • FIG. 22 shows exemplary extinction curves for two substances at two different wavelengths ⁇ , wherein the intensity difference ⁇ I caused by small thickness changes ⁇ d (blood pulsations) is shown.
  • a suitable apparatus for carrying out the method according to the invention has, according to FIG. 2, a radiation source 12 for emitting a measuring radiation 14 in the direction of a body part 16 to be examined.
  • the body part 16 to be examined is a human finger.
  • the earlobe of a person, as well as other suitable body parts can be used for measurement.
  • the device 10 has a first radiation receiver 18 for receiving radiation 20 reflected by the body part 16 to be examined.
  • the first radiation receiver is shown inticiansbeisp ⁇ e! arranged in the first receiving element 28. In this first receiving element 28 and the Strahlungsqueüe 12 is arranged.
  • the device 10 further comprises a second radiation receiver 22 for receiving the radiation 24 transmitted through the body part 16 to be examined.
  • the second radiation receiver 22 is arranged in the illustrated embodiment in the second receiving element 30, which is opposite to the first receiving element 28. Opposite in this context means that the two receiving elements 28, 30 and the first 18 and the second 22 radiation receiver are arranged such that, for example, a finger 16 can be positioned between them.
  • the emitted measuring radiation 14 is at least partially reflected by the body part 16 to be examined, so that an anection of the measuring radiation 14 is reflected as reflected radiation 20 in the direction of the first radiation receiver 18.
  • At least a portion of the radiation 14 passes through the body portion 16 to be examined and strikes the second as transposed radiation 24 Radiation receiver 22.
  • the first 18 and the second 22 radiation receiver are preferably designed as photodiodes.
  • the device further comprises a calculation device 26, which is connected to the first 18 and the second 22 radiation receiver.
  • the measured reflected 20 and transmitted 24 Strahlungsanteii is supplied to the computing device 26, so that it can determine based on the measured radiation components, the absorption of the emitted radiation 14 by the body part 16 to be examined.
  • the calculation device 26 can be designed, for example, as a PC on which a specific software program for carrying out said calculations runs. In particular, these calculations can also be made on a PC at a different time than the measurement of the transmitted and reflected radiation. Thus, the calculation steps essential to the invention take place independently of the physical detection of the patient feature described so far,
  • control device 41 such as a computer or a microprocessor.
  • the control device 41 may be part of the device 10.
  • the device has at least one radiation source for emitting a measuring radiation with different wavelengths.
  • the emitted worlds are in the area in which, for example, human skin is radiolucent.
  • This area is referred to as an optical window and is in a wavelength range of about 350 nm to 1650 nm (see FIG. 7). Outside of this range is the absorption the skin so high that hardly any radiation can penetrate into the underlying tissue.
  • hemoglobin derivatives as well as the water in human blood have particularly significant differences in their absorbance at these prominent wavelengths.
  • the light source 12 has, for example, a plurality of LEDs which are suitable for emitting different wavelengths.
  • the LEDs can be controlled in such a way that the LEDs are switched on and off successively, for example at a frequency of 1.2 kHz, so that no two different wavelengths are emitted at the same time.
  • a time-parallel emission of measurement radiation of different wavelengths is also possible if a plurality of radiation receivers are provided, which are suitable, for example, by frequency filters for receiving only a specific frequency band of the radiation.
  • a sequential control of the individual radiation sources is preferred, wherein, in deviation from the frequency of 1.2 kHz, a selection of further suitable frequencies is likewise possible.
  • the representation of the signals obtained can be done either in the so-called normal operation or in lock-in operation.
  • the lock-in operation creates an improvement in signal quality.
  • the lock-in amplifier In order to use the lock-in method, the lock-in amplifier must once detect the signal when the respective LED is shaded and once when it is off. The clock numbers of the LEDs can therefore differ from normal operation to lock-in operation.
  • the drive frequency for the LEDs In lock-in mode, the drive frequency for the LEDs can be adapted to the required frequency of the lock-in amplifier.
  • the Lock-in Prinz ⁇ p is a method for filtering and amplifying very small signals. It is on the Messsigna! a reference signal known Frequency and phase are modulated so that DC and AC voltages of other frequencies and noise are eliminated.
  • a DC component DC component / offset
  • a pulse-shaped AC component AC component
  • the DC component is due to the physiological properties of the irradiated tissue, it is influenced by various causes, such as tissue properties, blood vessels without pulsatile component (venules, etc.).
  • the pulse-shaped AC component alternating component
  • the DC component can be taken into account as a correction component.
  • An additional option is the use of analog or digital filters to separate the AC and DC components. In principle, this is possible in both modes, but should at least be carried out in normal operation in order to obtain a sufficient signal quality, since otherwise all interference is amplified.
  • Fig. 8 and 9 the Taktverhaiten several LEDs and the clock behavior of the reflected light receiving 18 and the transmitted light receiving 22 photodiode is shown. Only five wavelengths used are shown in FIG. 9. Accordingly, the principle of the readout behavior according to FIG. 9 can also be transmitted to more or fewer wavelengths. Preferred is a use of eight different wavelengths, as shown for example in Fig. 8.
  • sample-and-Hoid operation it is a so-called sample-and-Hoid operation shown, wherein in the lower half of the figure, two detector signals of the two detector surfaces used for each wavelength range are mapped.
  • a silicon receiver surface covers the wavelength range from 400 nm to 1100 nm, while an indium-gaflium-arsenide receiver surface covers the wavelength range from 1000 to 1700 nm.
  • the 540, 562, 573, 623, 660, 805 and 950 nm LEDs are turned on, respectively reflected 20 and the transmitted 24 measuring radiation detected by the silicon Empf ⁇ ger composition.
  • the value of the signal present at each time at the detector is recorded for each wavelength (sample), held (hold) and stored until the wavelength is addressed again.
  • the first cycle for example, eight wavelengths are emitted, their reflected 20 and transmitted 24 light component measured and then stored.
  • the individual absorption values of the emitted radiation 14 are combined for each wavelength in order to represent a time profile of the absorption at each wavelength.
  • a first possibility for determining the concentration ratio ratios is provided by linear systems of equations.
  • the transmitted intensity is calculated from the constant value ⁇ "ECdO and a substantially smaller fraction, which is caused by the pulsatile change in the diameter of the irradiated tissue.
  • the intensity of the transmitted wave is measured during systole (I 5 ) and diastole (I d ), and the intensity difference is formed. It is assumed that the signal of the phototransistor is proportional to the incident intensity.
  • the determined intensity difference between systole and diastole is proportional to the molar extinction E and concentration C of the blood component and to the path difference (d s -d d ).
  • the factor EC is a measure of the absorption A of the transmitted light:
  • the absorption at a given wavelength of light is directly proportional to the concentration of the blood component under consideration and proportional to the absorption coefficient of the constituent blood at the given wavelength, ie the higher the concentration of substance per given volume or the higher the value of the absorption coefficient, the stronger the absorption.
  • ⁇ and concentrations C bn of the blood components the following applies:
  • the measured total absorption Ag (except for a factor K ⁇ or K R ) is known for each wavelength of light used and the respective absorption coefficient associated with the blood component at the wavelength of light used. Unknown and to be determined are the respective proportions of the substance concentrations. According to the equation (10), an n * n system of equations can now be set up in order to determine the individual proportions of the blood components in the total volume.
  • Ag 1 (A2) E (A 2 , bi) * C bl + E (A 2 , D 2 ) * C b2 + E (A 2 , b 3 ) * C b3 + E (A 2 , D 4 ) * C b4 +
  • Ag 7 (A3) E (A 3 , b x ) * C bl + E (A 3 , b 2 ) * C b2 + E (A 3 , b 3 ) * C b3 + E (A 3 , b 4 ) * C b4 +
  • Ag R (A3) (K ⁇ / K R ) * ⁇ E (A 3 , bj * Cbl + E (A 3 , b 2 ) * C b2 + E (A 3 , D 3 ) * C b3 + E ( A 3 , b 4 ) * C b4 + E (A 3 , b 5 ) * C b5 ⁇
  • Ag R (A4) (K ⁇ / K R ) * ⁇ E (A 4 , b ⁇ * C bi + E (A 4 , b 2 ) * C b2 + E (A 4 , b 3 ) * C b3 + E ( A 4 ,
  • Ag R (A5) (K T / K R ) * ⁇ E (A 5 , b x ) * C bl + E (A 5 , b 2 ) * C b2 + E (A 5 , b 3 ) * C b3 + E (A 5 , b 4 ) * C b4 + E (A 5 , b 5 ) * C b5 > Ag-r ( ⁇ n) total absorption in transmission at ⁇ n
  • the system of equations (11) has the 5 concentrations Q 5n and the factor (K J / K R ) as unknowns and is therefore uniquely solvable. If measurements are to be made exclusively in transmission or reflection, the number of equations is reduced to the number n of wavelengths. On the other hand, over-mitigation with more equations than unknowns is possible to increase the accuracy of the result.
  • FIG. 1 An exemplary flowchart for calculating the concentrations of blood components is shown in FIG. It should be mentioned that during measurements in reflection mode La. Corrections are necessary because the conditions are more complex than in
  • a second possibility for determining the concentration ratios is provided by the heuristic flood regime.
  • the newly determined theoretical blood composition is discarded and a new blood composition is determined based on the previous one.
  • the sweat value is slightly increased and the newly determined blood composition is used as the starting point of the next round.
  • the algorithm can be executed several times with different boundary parameters and different starting points in order to better verify the heuristically determined result.
  • the measured absorption spectrum is now correlated with all previously calculated spectra.
  • the theoretically determined concentration ratios of the blood constituents of the spectrum in the set which correlates best with the measured spectrum, correspond to the real Konzentrationsverhititnissen, with good approximation,
  • the accuracy of this method depends primarily on the available computing power of the hardware. The more computing power available, the finer the concentration gradations can be chosen, and the more accurate the expected result.
  • the advantage of this method over the deluge algorithm is that the result is unique rather than heuristic in nature, that is, given some uncertainty in the result, which is unavoidable by a step size greater than zero in the parameter distribution, there is certainly no potentially better result as the specific.
  • a first calibration device 48 may be used, which is designed, for example, as a calibration sleeve for the reflexive receiver.
  • the Calibration of the device takes place to determine the actual light intensities of the LEDs initially without the body part to be examined.
  • a hemispherical calibration line 48 may be positioned on the reflective sensor 18 so as to include the emitting surface.
  • the Eichhuise 48 has a white inner surface 50, through which a diffuse reflection of the light is simulated, so that the light intensity of the individual LEDs can be determined.
  • the calibration sleeve in order to calibrate the sensor for the transmitted component 22, it is also possible to use a calibrated truncated cone 52 in particular between the receiver for the transmitted light component. 22 and the reflective receiver 18 are positioned.
  • the calibration sleeve likewise has a white inner surface 54 and also a white membrane 56 placed centrally between the two detector surfaces.
  • the white membrane 56 prevents direct irradiation of the LEDs on the receiver for the transmitted light component and at the same time generates a non-directional diffuse light radiation. With the aid of this measurement, the light intensities of the respective LEDs with respect to the transceiver 22 are detected.
  • Fig. 13c the total measured light intensity of each LED is shown. This measurement is referred to as a zero measurement and can be carried out with the calibrations described above. In order to assume a uniform radiation for further calculations, the intensities are normalized to 100%, whereby a normalization factor for the light intensity results for each LED ( Figure 14c).
  • This calibration measurement is done once for each sensor head and is performed again at defined time intervals, for example every two to three years. This method is due to the decrease in the light output of the light sources used, for example the LEDs.
  • the measurement can be performed on a body part.
  • the following process steps can be parts of the process according to the invention individually or as a whole.
  • a DC and an AC component is detected. In order to be able to compare the detected pulsatile light absorptions, they must be normalized for each wavelength as a function of the DC value. For this purpose, a determination of the DC component for each wavelength takes place at least once per measurement.
  • Figure 14b shows the transmuted portion of light.
  • the vast majority of light has been absorbed by the tissue (bone, skin and its constituents, eg melanin, degradation products of hemoglobin, eg bilirubin, venules, etc.).
  • a peak value of 3 AU (arbitrary unit) is measured.
  • This peak value is multiplied by the light intensity factor (here 1.33) so that the result is 4 AU.
  • this result is multiplied by the DC component factor (here 20).
  • the obtained 80 AU are then divided by the analog gain of 1, each wavelength being characterized by its own gain (as shown in Fig. 14: 542 nm: 1, 560nm: 1, 577nm, 1, 66nm: 10, 805nm: 5 950nm: 20; 1200nm: 20).
  • the absolute intensity of the pulsatile alternation at 542 nm is thus 80.00 AU.
  • the calculation of the alternating components follows the same principle, so that the normalized values can be compared with one another. By this procedure, the DC components are removed and only the pulsatile varying components are considered.
  • the DC share has an individual for each person Value due to its skin color, skin texture (keratinization), its bone structure and other metrological properties.
  • the radiation source 12 emits a measuring radiation 14.
  • the radiation source 12 may preferably be formed as a plurality of LEDs 12a to 12h.
  • the emitted measuring radiation 14 is at least partially reflected by the body part 16 to be examined, so that a portion of the measuring radiation 14 is reflected as reflected radiation 20 in the direction of the first radiation receiver 18.
  • the measurement of the radiation 24 transmitted through the body part 16 to be examined is shown schematically in FIG. 17.
  • a measuring radiation 14 is emitted in the direction of the body part 16 to be examined. At least a portion of the radiation 14 passes through the body part 16 to be examined and impinges on the second radiation receiver 22 as transmitted radiation 24.
  • the first 18 and the second 22 radiation receiver are preferably designed as photodiodes.
  • the device further comprises, according to FIG. 2, a calculating device 26 which is connected to the first 18 and the second 22 radiation receiver.
  • the measured reflected 20 and tra ⁇ smititterte 24 Part of the radiation is supplied to the calculation device 26 so that it can determine the absorption of the emitted radiation 14 by the body part 16 to be examined on the basis of the measured radiation components.
  • the calculation device 26 may, for example, be designed as a PC on which a specific software program for carrying out the aforementioned calculations runs. In particular, these calculations can also be made on a PC at a different time than the measurement of the transmitted and reflected radiation. Thus, the calculation steps essential to the invention take place independently of the physical detection of the patient features described so far.
  • the device 10 according to FIG. 18 is particularly preferably designed such that the radiation source 12 has a plurality of individual radiation sources 12a to 12h. These single-radiation sources can be designed as LEDs and can be arranged in a circle around the first radiation receiver 18.
  • the first light receiver 18 is disposed within a particular circular separator 32 which may comprise an inner impermeable sleeve 32a and an outer opaque sleeve 32b provided with a white coated inner wall.
  • the LEDs 12a to 12h are interposed in a gap 33 the inner sleeve 32a and the outer sleeve 32b.
  • the LEDs are raised at their side facing away from the first light receiver 18 side by an angle of 15 °. As a result, the emitted measuring radiation is bundled on a point at which the body part 16 to be examined is located.
  • the inner 32a and the outer sleeve 32b extend vertically upwards in a lower portion 34, starting from a base plate 36, such as a board, and continue to be bent inwardly in an upper portion 35 at an angle ⁇ , ie, in the direction of first radiation receiver 18.
  • This arrangement in conjunction with the raising of the LEDs, for example by an angle of 15 ° ensures that only a narrow gap 37 is available through which the emitted measuring radiation 14 can radiate in the direction of the body part 16 to be examined.
  • scattered light shunt light
  • the aim of this measure is that the first radiation receiver 18 only receives the radiation 20 which is reflected by the body part 16 to be examined.
  • a cavity 33 is formed, in which the LEDs 12a to 12h are attached to the circuit board 36, for example.
  • This cavity 33 may for example be filled with a transparent adhesive.
  • the individual light sources 12a to 12h can be designed to emit the following wavelengths:
  • FIG. 20 A graphical representation of the detectable Weiienilinden Kunststoffe the receiver surfaces used is shown in Figs. 20 and 21 to find.
  • the characteristics shown in Fig. 21 show two different indium-gallium arsenide detectors. Particularly preferred is the use of the left detector (L 1713-05 / -09).
  • Wavelengths above 1100 nm are correspondingly detected by the indium gallium arsenide photodiode.
  • the body part 16 to be examined is received in a receiving space 38 which is located between the first receiving element 28 and the second receiving element 30.
  • the device may comprise a clamping mechanism 40, such as a spring mechanism, through which the first 28 and the second 30 receiving element are connected to each other such that attachment of the device 10 to the body part 16 to be examined can take place.
  • a clamping mechanism 40 such as a spring mechanism
  • two actuating lugs 42 may be provided.
  • the device 10 has a control device 41 for sequentially switching on the individual light sources 12a to 12h.
  • the product of the molar extinction E and the concentration C of the blood constituent is defined as the total absorption Ag:
  • FIG. 22 shows the extinction curve for two different substances at two different wavelengths ⁇ .
  • the figures show that the intensity change ⁇ I is very small for a very small distance change ⁇ d, so that the above-derived linear approximation becomes plausible.
  • a 9 ( ⁇ ) total absorption (for a given wavelength)
  • E ( ⁇ , b n ) absorption coefficient of the blood component n at the
  • Ag (A 1) E (A 1, b ⁇ * C 1 + E (A 1, b 2) * C 2
  • Ag (A2) E (A 2, B) * C 1 + E (A 2, b 2 ) * C 2
  • the blood component with the highest concentration ie C 2 , is set equal to 100%.

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  • Spectroscopy & Molecular Physics (AREA)
  • Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

Procédé de détermination continue non-invasive de la concentration de composants sanguins, consistant à émettre plusieurs rayonnements de mesure (14) au moyen d'une source de rayonnement (12) à diverses longueurs d'ondes. Un premier récepteur de lumière (18) reçoit le rayonnement de mesure (14) de chaque longueur d'onde, réfléchi par une partie corporelle (16) à examiner. Un deuxième récepteur de lumière (22) reçoit le rayonnement de mesure (24) de chaque longueur d'onde, transmis par la partie corporelle (16) à examiner. L'absorption du rayonnement de mesure (14) de chaque longueur d'onde par la partie corporelle (16) à examiner est ensuite déterminée sur la base de la mesure du rayonnement (20) réfléchi dans le premier récepteur de rayonnement (18) et de la mesure du rayonnement (24) transmis dans le deuxième récepteur de rayonnement (22). L'absorption du rayonnement de mesure (14) à chaque longueur d'onde permet de calculer la concentration des divers composants sanguins.
EP08735450A 2007-03-23 2008-03-20 Procédé de détermination continue non-invasive de la concentration de composants sanguins Withdrawn EP2004043A1 (fr)

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DE200710014583 DE102007014583B3 (de) 2007-03-23 2007-03-23 Vorrichtung zur kontinuierlichen nichtinvasiven Bestimmung von Konzentrationen verschiedener Blutbestandteile und Verfahren zum Betreiben einer solchen Vorrichtung
EP07104761 2007-03-23
PCT/EP2008/053397 WO2008116835A1 (fr) 2007-03-23 2008-03-20 Procédé de détermination continue non-invasive de la concentration de composants sanguins
EP08735450A EP2004043A1 (fr) 2007-03-23 2008-03-20 Procédé de détermination continue non-invasive de la concentration de composants sanguins

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US20100331636A1 (en) 2010-12-30
CN101686803B (zh) 2012-09-19

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