WO2017199251A1 - Mesure de la saturation en oxygène dans le sang d'une veine - Google Patents

Mesure de la saturation en oxygène dans le sang d'une veine Download PDF

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WO2017199251A1
WO2017199251A1 PCT/IL2017/050549 IL2017050549W WO2017199251A1 WO 2017199251 A1 WO2017199251 A1 WO 2017199251A1 IL 2017050549 W IL2017050549 W IL 2017050549W WO 2017199251 A1 WO2017199251 A1 WO 2017199251A1
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vein
light
detector
light source
wavelengths
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Meir Nitzan
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Jerusalem Colleague Of Technology
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    • 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 or pH-value ; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid or cerebral tissue
    • A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration or pH-value ; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid or cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
    • A61B5/14551—Measuring characteristics of blood in vivo, e.g. gas concentration or pH-value ; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid or cerebral tissue using optical sensors, e.g. spectral photometrical oximeters for measuring blood gases
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/314—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths
    • 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
    • A61B5/0075—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording for evaluating the cardiovascular system, e.g. pulse, heart rate, blood pressure or blood flow
    • A61B5/024—Measuring pulse rate or heart rate
    • A61B5/02416—Measuring pulse rate or heart rate using photoplethysmograph signals, e.g. generated by infrared radiation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/314—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths
    • G01N2021/3144—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths for oxymetry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/06—Illumination; Optics
    • G01N2201/066—Modifiable path; multiple paths in one sample
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/08—Optical fibres; light guides

Definitions

  • the presently disclosed subject matter relates to oxygen saturation measurement in a single vein blood.
  • Oxygen saturation in blood is the ratio between the concentration of oxygenated and total hemoglobin in the blood, and its value in arterial blood, Sa0 2 , provides information regarding the performance of the respiratory system.
  • Total hemoglobin in the blood includes oxygenated (Hb0 2 ) and deoxygenated hemoglobin (Hb).
  • Pulse oximetry is a noninvasive method for the assessment of Sa0 2 by measuring the cardiac induced changes in light transmission through the tissue due to changes in the blood volume of small arteries in the microcirculation - photoplethysmography (PPG). Pulse oximetry technique is based on the different light absorption spectra for Hb0 2 and Hb (Fig. 1), and on the measurement of light transmission changes in two wavelengths, which, in the commercial devices, are in the red and the infra-red (IR) regions (Farmer 1997, Wieben 1997, Moyle 2002).
  • the quantitative relationship between the PPG pulses and the Sa0 2 is derived by applying the modified Beer- Lambert equation to the transmitted light intensity, I t , through a tissue sample of width d which includes blood vessels, arteries and veins, with whole blood (Matcher 2002, Delpy 1988, Yoxal 1997).
  • the transmitted light intensity, I t c ⁇ m thus be expressed as:
  • Pulse oximetry is based on the application of Equation [la] to the PPG signal.
  • I t t e values of Is the lower light transmission through the higher tissue blood volume during systole, and ID, the higher transmitted light through the lower tissue blood volume at end-diastole (Fig. 2), and assuming that G, the attenuation due to the tissue, does not change appreciably by the systolic arterial blood volume increase (Matcher 2002, Yoxal et al 1997) it can be shown that: and
  • ID-IS is the PPG signal amplitude (AM) shown in Fig. 2, and is related to the maximal blood volume change during systole (Babchenko et al 2001).
  • the pulse oximetry technique for the assessment of oxygen saturation in arterial blood is based on the assumption that the PPG signal reflects absorption in the arterial blood volume increase during systole. It should be noted that pulse oximetry is a measurement in microcirculation and its accuracy is reduced if the illuminated region includes a big artery (Mannheimer et al 2004, Reuss and Siker 2004). In pulse oximetry, light transmission is measured at two wavelengths ⁇ and ⁇ 2 . If the extinction coefficient of the arterial blood volume for the two wavelengths ⁇ and ⁇ 2 are ⁇ and ⁇ 2 respectively, then, from Equation [3]:
  • ratios R defined by:
  • Equation [5] assuming that the difference in the blood concentration change AC between the two wavelengths and the difference in path-lengths between the two wavelengths can be neglected (ACi»:AC 2 , h ⁇ h).
  • ACi AC 2 , h ⁇ h.
  • the assumption that the difference in path-lengths can be neglected can be acceptable when the two wavelengths are close to each other (i.e. when both are in the IR region) but not for wavelengths in the red and IR regions.
  • Equation [5] the relationship between the measured parameter R and the physiological parameter Sa0 2 can be derived (Nitzan et al 2000):
  • ⁇ and SD are the extinction coefficients for Hb0 2 and Hb, respectively and the subscripts 1 and 2 refer to the two wavelengths.
  • the assumption that h is not much different than h, and R can be approximated by ⁇ / ⁇ 2 can introduce error in the calculation of Sa0 2 : significant error for wavelengths in the red and IR regions and small error for two wavelengths in the IR region. In the latter case, some correction, due to the small difference between the two path-lengths, may be required (Nitzan et al 2000).
  • the maximum (ID), minimum (Is), amplitude and relative amplitude (rAM-AM/Is) are calculated (Fig. 2), and from the relative amplitude in the two wavelengths, rAMi and
  • the measured parameter R is a
  • the value of oxygen saturation in venous blood also has clinical significance since it is related to oxygen utilization in the corresponding tissue, which is related to the blood flow to the tissue and to its metabolism rate (Thiele et al 2011).
  • Pulse oximetry of the venous blood in the microcirculation was performed, using the changes in venous blood due to mechanical ventilation (Shafqat et al 2015, Walton et al 2010).
  • direct calibration is not applicable in venous pulse oximetry since pulse oximetry is a measurement in the microcirculation while the calibration is based on in vitro measurement of oxygen saturation in extracted blood from big veins, and different veins have different value of Sv0 2 .
  • Sv02 in the microcirculation can also be obtained by inflating a pressure cuff to apply pressure, above venous blood pressure, in order to increase the venous blood volume in the microcirculation (Nitzan et al 2000).
  • NIRS near IR spectroscopy
  • NIRS techniques have generally been used for measurement of tissue oxygen saturation, St02, which is the mean oxygen saturation in all blood vessels, arteries and veins; in some studies, NIRS techniques were used for measurement of Sv02 in microcirculation (14, Yoxal et al 1997).
  • Pulse oximetry has also been used for Sv0 2 measurement in a single vein (Thiele 2011), utilizing venous blood volume changes by respiration, but, the results significantly deviated from real Sv0 2 values.
  • pulse oximetry is not applicable in the neighborhood of big vessel (Mannheimer et al 2004, Reuss and Siker 2004), probably because pulse oximetry is based on the assumption that the pulsatile change in light absorption is proportional to the pulsatile change in blood volume and this assumption is not valid in big vessels [15].
  • the light source illuminates a large region of the tissue, wider than the single vein, and the detector also detects light scattered from the other small veins in the tissue outside the single vein. Accordingly, there is a need for an innovative method for the measurement of the oxygen saturation in a single vein, based on minimal interference of the light traveling in the tissue outside the vessel.
  • an apparatus for oxygen saturation measurements in a single blood vein includes a light source configured to emit light at two wavelengths into at least one site on the surface of a single blood vein, and at least one detector configured to detect the transmitted light at the two wavelengths after passing through the blood vein, the at least one detector is disposed in close proximity to the light source such that a majority of light detected by the detector travels through the vein; wherein the light source and the at least one detector are so disposed with respect to the blood vein such that the light travels from the at least one site to the at least one detector in a first optical path having a first effective path-length and a second optical path having a second effective path-length.
  • the light source can be configured to emit light into the single blood vein such that the amount of light scattered and reflected by tissues surrounding the vein and detected by the detector is negligible with respect to the total amount of light detected by the detector.
  • the light source can be configured to emit light at a site having a dimeter smaller than the diameter of the vein, such that the majority of the light travels through the vein.
  • the detector can be disposed such that the amount of light which is scattered and reflected by tissues surrounding the vein and detected by said detector is negligible with respect to the total amount of light detected by said detector.
  • the light source can be configured to alternately emit light at two wavelengths towards a single vein blood and wherein the detector can be configured to separately detect the two wavelengths after passing through the blood vein.
  • the light source can include at least one emitting optic fiber optically coupled thereto and being configured to transfer the light from the light source towards the blood vein, wherein the emitting optic fiber can be selectively displaceable between a first disposition with respect to the detector and a second disposition with respect to the detector, wherein in the first disposition the light travels from the light source to the at least one detector in the first optical path, and wherein in the second disposition the light travels from the light source to the at least one detector in the second optical path.
  • the first disposition the emitting optic fiber can be disposed at a first location with respect to the vein and in the second disposition the emitting optic fiber can be disposed at a second location with respect to the vein.
  • the first disposition the emitting optic fiber can be configured to emit light at a first angle with respect to the vein and in the second disposition the emitting optic fiber can be configured to emit light at a second angle with respect to the vein.
  • the light source includes a first emitting optic fiber and a second emitting optic fiber, the first and second emitting optic fibers are optically coupled to the light source and being configured to transfer the light from the light source towards the blood vein; wherein the first optical path can be defined between the first emitting optic fiber and the detector and the second optical path can be defined between the second emitting optic fiber and the detector.
  • the at least one detector includes a first collecting optic fiber and a second collecting optic fiber, the first and second collecting optic fibers are optically coupled to the detector and being configured to transfer light from the vein towards the detector; wherein the first optical path can be defined between the light source and the first collecting optic fiber and the second optical path can be defined between the light source and the second collecting optic fiber.
  • the detector can be a camera configured for detection the two wavelengths at several regions in proximity of the at least one site.
  • the light source can include an emitting optic fiber disposed on one side of the vein and the detector includes a collecting optic fibers disposed on an opposing sides of the vein such that light measured by the detector can be a portion of the light which traveled from one side of the vein to the other side thereof.
  • the two wavelengths are selected such that the difference between an extinction coefficient of Hb and an extinction coefficient of Hb02 can be different for each of the two wavelengths.
  • a first wavelength of the two wavelengths can be below an isosbestic point, where Hb has higher extinction coefficient than Hb0 2
  • a second wavelength of the two wavelengths can be above the isosbestic point, where Hb0 2 has higher extinction coefficient.
  • the apparatus can further include a processor configured to calculate the oxygen saturation in a single vein by measuring a relative difference in light transmission between the first and second effective path-lengths through the single vein, for the two wavelengths, where the relative difference in light transmission is the difference in light transmission divided by the light transmission through the longer effective path-length.
  • the calculation can include calculation of ratio of ratios for the two wavelengths wherein the ratio for each wavelength can be the natural logarithm of the ratio between the light intensity with the first path-length and the light intensity with the second path- length.
  • the processor can be further configured to obtain oxygen saturation measurements in a single blood vein from the ratio of ratios by calibration of the results of the ratio of ratios with respect to corresponding data measured in vitro in extracted blood from the vein.
  • the processor can be further configured to obtain oxygen saturation measurements in a single blood vein from the ratio of ratios by an analytical function based on simulation of the light from transfer from the light source and detected by the detector.
  • a method for measuring oxygen saturation in a single blood vein includes illuminating with a light source a single blood vein with light at two wavelengths; detecting with a detector the light after passing through the blood vein, the detector is disposed in close proximity to the the light source such that a majority of light detected by the detector travels through the vein; wherein the light source and the at least one detector are so disposed with respect to the blood vein such that the light travels from the light source to the at least one detector in a first optical path having a first effective path- length and a second optical path having a second effective path-length.
  • the step of illuminating with a light source a single blood vein can be carried out at a first location with respect to the vein forming thereby the first optical path, and at a second location with respect to the vein forming thereby the second optical path.
  • the step of detecting with a detector the light can be carried out with a first collecting optic fiber disposed at a first location with respect to the vein forming thereby the first optical path, and with a second collecting optic fiber disposed at a second location with respect to the vein forming thereby the second optical path.
  • the step illuminating can be carried out on one side of the vein and the step of detecting can be carried out on an opposing side of the vein.
  • the method can further include calculating the oxygen saturation in a single vein by measuring a relative difference in light transmission between the first and second effective path-lengths through the single vein, for the two wavelengths.
  • the method can further include calculating ratio of ratios for the two wavelengths wherein the ratio for each wavelength can be the natural logarithm of the ratio between the light intensity with the first path-length and the light intensity with the second path- length.
  • the method can further include obtaining oxygen saturation measurements in the single blood vein from the ratio of ratios by calibration of the results of the ratio of ratios with respect to corresponding data measured in vitro in extracted blood from the vein.
  • the above apparatus and method provides difference oximetry technique which includes measurement of the relative difference in or ratio of light transmission between two effective path-lengths through a single vein, for two wavelengths.
  • the vein's oxygen saturation can be derived from the ratio of these differences for two wavelengths.
  • Fig. 1 is a prior art graph of the extinction coefficients of the oxi- and deoxi- hemoglobin as a function of the wavelength, in the near-infrared region;
  • Fig. 2 is a prior art graph of the PPG signal in the microcirculation, which presents the light transmission in the tissue against time, showing variations at the heart rate, wherein maximal light transmission I D (minimal light absorption) occurs at end-diastole when the tissue blood volume is at minimum;
  • Fig. 3a is a schematic illustration of a system for non-invasive measurement of Sv0 2 in accordance with an example of the presently disclosed subject matter
  • Fig. 3b is a schematic illustration of a system for non-invasive measurement of Sv0 2 in accordance with another example of the presently disclosed subject matter
  • Fig. 4 is a schematic illustration of a system for non-invasive measurement of Sv0 2 in accordance with yet another example of the presently disclosed subject matter
  • Fig. 5a is a top view of the system of Fig. 4 in which both the emitting and the collecting optical fibers are disposed on a single side of a vein;
  • Fig. 5b is a top view of the system of fig. 4, in which the emitting and the collecting optical fibers are disposed on opposing sides of a vein.
  • the presently disclosed subject matter provides an apparatus and a method for a non-invasive measurement of Sv0 2 in the blood of a single vein 5 (hereinafter Ssv0 2 ).
  • the apparatus 10 includes a light source 12 configured to emit, alternately, light at two wavelengths, schematically designated 14a and 14b, and a detector 20 configured to detect the two wavelengths 14a and 14b, separately.
  • the light source 12 and the detector 20 are disposed on a skin surface above the vein under examination such that light at the two wavelengths 14a and 14b is directed towards the vein and is reflected back to the detector 20.
  • the detector 20 which can be located adjacent the light source 12, detects the light transmitted and scattered through the vein 5.
  • the light source 12 and the detector 20 have a relatively small optical aperture and are brought into proximity (i.e. with minimal intervening tissue) with the blood vein 5, such that there is minimal tissue intervening between the optical apertures and the vein 5.
  • the detector 20 measures mainly light that its trajectory is mostly in the single vein 5 and the effect of absorption and scattering of the light in adjacent tissues, such as other blood vessels, is minimized.
  • the light from the light source 12 can be conveyed to the desired location on skin surface via one or more optic fibers (hereinafter emitting optic fiber 16).
  • the light reflected and or transmitted from the vein 5 and the surrounding tissues can be collected via one or more optic fibers (hereinafter collecting optic fiber 18).
  • obtaining a relatively small optical apertures for the light transmitted or collected from the skin surface can be carried out by means of appropriate slits, attached to the light source 12 and/or the detector 20. It is appreciated that collection of light from a small defined region on the skin above the vein can also be achieved without contacting the skin surface for example via imaging device such as CCD or CMOS camera, as described below.
  • the blood vein 5 is illuminated by light of two wavelengths 14a and 14b emitted through two emitting optic fibers or, as shown here, through a single emitting optic fiber 16, for example i.e. bifurcated optic fiber.
  • light transferred through the blood vein can be collected by a single collecting optic fiber 18, which can be placed adjacent the emitting optic fiber 16, and is configured to convey the light into the detector 20.
  • the emitting optic fiber 16 is a stationary fiber configured such that the light transmitted therethrough and through the vein 5 and towards the detector 20 travels through a predefined optical path.
  • the emitting optic fiber 16 coupled to the light source 12 emits light in two wavelengths alternatively, and the detectors 20 measure the transmitted light in each of the wavelengths, for example by using time sharing or frequency sharing.
  • one of the two wavelengths is selected such that a first wavelength is below the isosbestic point, where Hb has higher extinction coefficient than Hb0 2 , while the other wavelength is above the isosbestic point, where Hb0 2 has higher extinction coefficient.
  • Measurement of In for a single wavelength during time can provide
  • the two wavelengths, ⁇ and ⁇ 2 preferably selected such that one is below the isosbestic wavelength and the other is above the isosbestic wavelength, can provide better evaluation of Ssv0 2 .
  • Accuracy may be increased if the differences between the values of G, C and / for the two wavelengths are small, as will happen when the two wavelengths will be close to each other. Accuracy is also expected to increase when the detector is disposed in close proximity to the light source such that a majority of light detected by the detector travels through the vein that is to say, the detector can be disposed such that the amount of light which is scattered and reflected by tissues surrounding the vein is negligible with respect to the amount of light detected by the detector.
  • the emitting optic fiber 16 and the collecting optic fiber 18 are disposed such that the distance between their contact sites is small (1 mm or less) and they are located on the midline of the vessel.
  • the light source is configured to emit light into the single blood vein such that the amount of light scattered and reflected by tissues surrounding the vein is negligible with respect to the amount of light detected by the detector. That is to say, the light source can be configured to emit light at a site having a dimeter smaller than the diameter of the vein, such that the majority of the light travels through the vein. For example, in case the vein width is large (i.e. more than 2 mm), the optical apertures of the emitting optic fiber 16 and the collecting optic fiber 18are small (0.5 mm or less).
  • the accuracy of the technique can be improved by imitating pulse oximetry. That is to say, in pulse oximetry the transmitted light is measured, for each wavelength, after the light travels along two different optical paths each having a different path length, i.e. during systole and during diastole.
  • the two different optical paths are formed by emitting or detecting light in more than one location as described above with respect to Figs. 3b and 4 each having a different path-length between the light-emitting fiber and the detector fiber.
  • the two different optical paths occur when the light-emitting fiber changes its direction or its contact site with the vessel's wall (or more accurately the contact site with the skin above the vessel), resulting in different path-lengths between the light source 12 and the detector 20.
  • the changes of the fiber direction or its contact site with the vessel's wall can be achieved by means of electro-mechanical element such as piezoelectric transducer or by electro-optic modulator etc.
  • the preferred period time of changing the direction of the light or the location of the contact site on the skin is in the range of 0.1-1 s.
  • the method is defined difference oximetry.
  • the detection of the light transmitted through the blood inside the vein can also be performed in several effective path-lengths by means of a camera, viewing a region at proximity to the light emitting fiber, and measuring the light intensity, in each wavelength, emitted from each pixel in that region.
  • the two different optical paths can be obtained with an apparatus wherein the emitting optic fiber 16 is configured to be displaceable between two adjacent locations, 32 and 34, on the skin surface.
  • the emitting optic fiber 16 is configured to selectively emit light at a first and a second directions into the skin above the vein 5.
  • the light is thus transmitted through the vein via two different optical paths, starting either from 32 or from 34.
  • the collecting optic fiber 18 alternately collects light which travels through two different optical paths.
  • the emitting optic fiber 16 is configured to be displaceable between two adjacent locations such that light travels towards the collecting optic fiber 18 via two different optical paths.
  • the collecting optic fiber 18 is also configured to be displaceable between two adjacent locations.
  • the emitting optic fiber 16 is configured to selectively emit light at a first and a second locations on the skin surface
  • collecting optic fiber 18 is configured to selectively collect light at a third and a forth locations on the skin surface. The light which is received by the detector 20 is transmitted through the vein via two different optical paths.
  • the apparatus 50 can include a single emitting optic fiber 16 and two detectors 20a and 20b, each of which having a collecting optic fibers 18a and 18b configured to transmit light thereto.
  • light is emitted via an emitting optic fiber 16 at a single location 32 on the skin surface where it is directed towards the vein 5.
  • the light transmitted through the vein 5 is collected by the first optic fibers 18a disposed on one location 36a over the skin surface, as well as by the second collecting optic fibers 18b disposed on a second location 36b over the skin surface.
  • the first and second collecting optic fibers 18a and 18b convey the light into the first and second detectors 20a and 20b, respectively.
  • the two collecting optic fibers 18a and 18b can be placed in close proximity to one another and adjacent the emitting optic fiber 16, such that the optical path between the emitting optic fiber 16 and the first collecting optic fiber 18a is different than the optical path between the emitting optic fiber 16 and the second collecting optic fiber 18b.
  • the apparatus collects data regarding light transmitted through two different optical paths via the vein 5.
  • the detection of the light transmitted through the blood inside the vein in two or more effective path-lengths can also be realized by means of a camera, viewing a region at proximity to the light emitting fiber, and measuring the light intensity, in each wavelength, emitted from different pixels in that region.
  • the two wavelengths can be in the IR region, or in the red and infrared regions.
  • emitting optic fiber 16 is configured to convey light from two light sources 12, each of which emits light in one wavelength. The light is emitted by the emitting optic fiber 16 into the vein 5 and the two collecting optic fibers 18a and 18b, which collect light scattered by the red blood cells in the vein, are configured to convey the light towards the two detectors 20a and 20b. According to this example the two collecting optic fibers 18a and 18b, are placed in different distances from the emitting optic fiber 16.
  • the emitting optic fiber 16 and the collecting optic fibers 18a and 18b can be placed on the same side of the vein (as shown in Fig. 5a) such that the light measured by the detector is a portion of the backscattered light.
  • the emitting optic fiber 16 is disposed on one side of the vein 5, while the collecting optic fibers 18a and 18b are disposed on opposing sides thereof (as shown in Fig. 5b). This way, the light measured by the detector 20 is a portion of the light which traveled from one side of the vein 5 to the other side thereof.
  • the difference in light transmission between the light transmission values for each of the two optical paths can be small relative to the light transmission values, say, ⁇ a - « where a and b are the two locations of the emitting optic fiber 16.
  • This difference in the values obtain by the difference in the path length is similar to the situation of pulse oximetry (see Equation [2]), where the difference in path-lengths, between systole and in diastole is small (typical value 0.5- 2%).
  • Rv can be defined by: R
  • the value of Ssv0 2 can be determined from Rv by:
  • Ssv0 2 can be determined by another similar analytic formula, or by calibration.
  • Rv is defined by:
  • RV and Ssv0 2 can be determined from Rv either by calibration or by another analytic formula which uses scattering and absorption parameters, such as:
  • h and h are the path-lengths for the two wavelengths, ⁇ and ⁇ 2 , respectively (Nitzan et al 2000).
  • two different path-lengths can be achieved in case the measurements of Ssv0 2 of a system as described above with respect to Figs. 3b or 4, i.e. a system moving emitting optic fiber 16, two emitting optic fiber 16, or having two detector coupled to collecting optic fibers 18a and 18b each disposed at a different distance from the emitting optic fiber 16.
  • the system provides a similar effect as in pulse oximetry, where the transmitted light is measured, in each wavelength, after passing through two different path-lengths, in systole and in diastole.
  • the two path-lengths in the blood are the path- lengths in the two trajectories along which the light passed towards the two detectors.
  • the method can be defined as difference oximeter. It is noted that in pulse oximetry the difference in the effect of the scattering on the attenuation of light between end-diastole and during systole is small due to the relative small change in blood volume during systole. In single vein measurement with two detectors, on the other hand, the difference in the effect of scattering on the attenuation of light for the two detectors is generally significant. This is due to the great difference in path-length between the two detectors and the high scattering coefficient of light in blood. Accordingly, for each wavelength, assuming the same incident light intensity for the two wavelengths:
  • I t2 I Q e - ⁇ - £C ⁇ ;
  • Rv and Ssv0 2 can be obtained either by calibration or by analytical function, based on a model or simulation of the transmitted light from the light-emitting fiber to each detector fiber, such as above Equation [6] or similar equation.
  • Calibration can be carried out by applying the probe on an external vein and calculating the measured parameter Rv and comparing it to the physiological parameter Ssv0 2 in the vein, measured in vitro in extracted blood from the vein.
  • the detection of the light transmitted through the blood in the vein can also be performed in several effective path-lengths by means of a camera, viewing a region at proximity to the light emitting fiber, and measuring the light intensity, in each wavelength, emitted from each pixel in that region.

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

Abstract

L'invention porte sur un appareil pour des mesures de saturation en oxygène dans une veine, l'appareil comprenant une source de lumière conçue pour émettre de la lumière à deux longueurs d'onde vers une veine, et au moins un détecteur conçu pour détecter la lumière aux deux longueurs d'onde après avoir traversé la veine; l'au moins un détecteur est disposé à proximité immédiate de la source de lumière de telle sorte qu'une majorité de la lumière détectée par le détecteur traverse la veine; la source de lumière et l'au moins un détecteur étant disposés par rapport à la veine de telle sorte que la lumière se déplace de la source de lumière vers l'au moins un détecteur dans un premier trajet optique ayant une première longueur de trajet effective et un second trajet optique ayant une seconde longueur de trajet effective.
PCT/IL2017/050549 2016-05-17 2017-05-16 Mesure de la saturation en oxygène dans le sang d'une veine Ceased WO2017199251A1 (fr)

Applications Claiming Priority (2)

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US201662337359P 2016-05-17 2016-05-17
US62/337,359 2016-05-17

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WO2017199251A1 true WO2017199251A1 (fr) 2017-11-23

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PCT/IL2017/050549 Ceased WO2017199251A1 (fr) 2016-05-17 2017-05-16 Mesure de la saturation en oxygène dans le sang d'une veine

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080097173A1 (en) * 2006-05-30 2008-04-24 Soyemi Olusola O Measuring Tissue Oxygenation
US20130310669A1 (en) * 2012-05-20 2013-11-21 Jerusalem College Of Technology Pulmonary pulse oximetry method for the measurement of oxygen saturation in the mixed venous blood

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080097173A1 (en) * 2006-05-30 2008-04-24 Soyemi Olusola O Measuring Tissue Oxygenation
US20130310669A1 (en) * 2012-05-20 2013-11-21 Jerusalem College Of Technology Pulmonary pulse oximetry method for the measurement of oxygen saturation in the mixed venous blood

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