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Patent US7386336 - Method and system for use in non-invasive optical measurements of blood ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA method and device are presented for use in non-invasive optical measurements of at least one desired characteristic of patient's blood. A condition of artificial blood kinetics is created at a measurement location in a patient's blood perfused fleshy medium and maintained for a certain time period....http://www.google.com/patents/US7386336?utm_source=gb-gplus-sharePatent US7386336 - Method and system for use in non-invasive optical measurements of blood parametersAdvanced Patent SearchPublication numberUS7386336 B2Publication typeGrantApplication numberUS 11/341,631Publication dateJun 10, 2008Filing dateJan 30, 2006Priority dateJun 3, 2003Fee statusPaidAlso published asUS6993372, US20040249252, US20060129040Publication number11341631, 341631, US 7386336 B2, US 7386336B2, US-B2-7386336, US7386336 B2, US7386336B2InventorsIlya Fine, Alexander FinarovOriginal AssigneeOrsense Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (19), Referenced by (1), Classifications (16), Legal Events (1) External Links: USPTO, USPTO Assignment, EspacenetMethod and system for use in non-invasive optical measurements of blood parameters
US 7386336 B2Abstract
1. A system for use in non-invasive optical measurements in a human body, the system comprising:
a probe configured as a ring-like device for removable mounting onto a patient's finger so as to enclose and hold a portion of a patient's blood perfused flesh medium between two semi-ring portions, said probe carrying a pressurizing assembly and carrying an optical measuring unit, the measuring unit being configured and operable for performing optical measurement and comprising an illumination assembly for illuminating a measurement location on the finger with incident light beams of at least two different wavelengths and a detection assembly configured and operable for detecting at least two light responses of the medium for said at least two different wavelengths, and generating at least two measured data portions indicative of said light responses; and
a control unit configured for operating the pressurizing assembly to apply over-systolic pressure to said measurement location and maintain the application of over-systolic pressure during a certain time period, and for operating the measuring unit to perform said optical measurement during said certain time period, said control unit being preprogrammed for receiving and analyzing said at least two measured data portions, determining time evolutions of the light responses, determining a relation between said time evolutions indicative of at least one parameter of the patient's fleshy medium, and displaying said at least one parameter.
2. The probe of claim 1, wherein the pressurizing assembly is carried on an inner surface of the ring-like probe and the optical measuring unit is carried on an outer surface of said ring-like probe such that light propagating in between the optical measuring unit and the finger pass through apertures made in the ring-like probe.
3. The probe according to claim 2, wherein the pressurizing assembly comprises an air cushion assembly connected to a drive operable by the control unit to apply said over-systolic pressure to the portion of the finger covered by said air cushion.
4. The probe according to claim 3, wherein said air cushion assembly is configured and operable for applying a primary over-systolic pressure to the finger.
5. The probe according to claim 4, wherein said air cushion assembly is configured and operable for applying a secondary pressure variable up to over-systolic pressure values.
6. The probe according to claim 2, wherein the aperture associated with the light detection unit is located with respect to the aperture associated with the illumination unit so as to detect light reflected from the finger.
7. The probe according to claim 6, wherein an additional aperture associated with the light detection unit is located opposite the aperture associated with the illumination unit so as to detect light transmitted through the finger.
8. The probe according to claim 2, wherein the aperture associated with the light detection unit is located with respect to the aperture associated with the illumination unit so as to detect light transmitted through the finger.
Non-invasive techniques for measuring various blood parameters, e.g., blood oxygen saturation, have become very popular, since they do not require the withdrawal of a blood sample from a patient's body. Optical monitoring techniques of the kind specified utilize the detection of light transmitted or reflected from the location on the patient's body under measurement, and are based on spectrophotometric measurements enabling the indication of the presence of various blood constituents based on known spectral behaviors of these constituents.
Various probe devices suitable for the occlusion-based measurements are described in U.S. Pat. No. 6,213,952 and US 2002/0173709 both assigned to the assignee of the present application. These devices are designed to apply over-systolic pressure to the patient's finger at a location upstream of a measurement location in the finger, with respect to the direction of normal blood flow, thereby creating a state of blood flow cessation at the measurement location. Generally, the device includes a clip member for securing the patient's finger between its two clamping arms that also serve for carrying the optics of a measurement unit, and includes a pressurizing assembly outside the clip member for applying over-systolic pressure.
applying a primary over-systolic pressure to a patient's blood perfused fleshy medium at a location in vicinity of a measurement location to thereby create a condition of artificial blood kinetics at the measurement location, and maintaining this condition for a certain time period; varying the over-systolic pressure in the vicinity of the measurement location starting from said primary over-systolic pressure value thereby altering said condition of artificial blood kinetics at the measurement location over a predetermined time interval within said certain time period so as to modulate scattering properties of blood; and applying optical measurements to the measurement location by illuminating it with incident light beams of at least two different wavelengths in a range where the scattering properties of blood are sensitive to light radiation, detecting light responses of the medium, and generating measured data indicative of time evolutions of the light responses of the medium for said at least two different wavelengths, respectively, over at least a part of said predetermined time interval. According to yet another broad aspect of the present invention, there is provided an optical system for use in non-invasive optical determination of at least one desired characteristic of patient's blood, the system comprising:
(A) a probe including: (i) an optical measuring unit operable for illuminating a measurement location on a patient's blood perfused flesh medium with different wavelengths of incident light, detecting light responses of the medium, and generating measured data indicative of time evolutions of the light responses of the medium corresponding to the different wavelengths of incident light, respectively; and (ii) a pressurizing assembly operable for applying pressure to the patient's fleshy medium; (B) a control unit connectable to said measuring unit and said pressurizing assembly for synchronizing the operation thereof so as to apply a primary over-systolic pressure to a certain location on the medium to create a condition of artificial blood kinetics in the medium at the measurement location and maintain this condition for a certain time period, to apply a secondary controllably varying pressure to the fleshy medium in the vicinity of the measurement location so as to alter said condition of artificial blood kinetics over a predetermined time interval within said certain time period thereby modulating scattering properties of blood, and to apply the optical measurements while altering the condition of the artificial blood kinetics, the control unit comprising: (a) a memory for storing reference data sensitive to patient individuality and indicative of the desired blood characteristic as a function of a parameter derived from scattering spectral features of the medium, and (b) a data acquisition and processing utility coupled to output of the measuring unit for receiving and analyzing the measured data to utilize the reference data and determine said at least one desired blood characteristic. According to one embodiment of the invention, the altering of the condition of the artificial blood kinetics is performed by applying a perturbation to the medium by a secondary pressure pulse of a predetermined value over the predetermined time interval so as to modulate scattering properties of blood.
According to one embodiment, the first and second functions can be logarithmic functions log(T1) and log(T2) of the light responses T1 and T2 corresponding to the two different wavelengths λ1 and λ2, respectively. According to another embodiment, the first and second functions can be functions of the time rate of the changes of the light response signal, i.e., ΔT/Δt (or Δ log T/Δt), where Δt can be any part of the time interval during which the condition of artificial kinetics is changed.
According to one embodiment, the probe includes a pressurizing assembly and a measuring unit. The pressurizing assembly includes a primary occlusion cuff for applying the primary over-systolic pressure to the medium, a secondary occlusion cuff for applying the secondary pressure to the medium and a pressure driver actuated by the control unit for operating the squeezing of the cuffs and. According to this embodiment, the location secondary occlusion cuff is selected downstream of the location primary occlusion cuff with respect to the normal blood flow direction. The measuring unit comprises an illumination assembly and a light collection/detection assembly. The illumination assembly includes a plurality of light sources (e.g., LEDs) associated with a suitable drive mechanism operated by the control unit. Alternatively, a single broad band illuminator can be used. The light sources generate incident radiation propagating through the medium at a measurement location. The light collection/detection assembly includes one or more frequency selective detectors arranged near the measurement location. Examples of collection/detection assembly include, but are not limited to, spectrophotometers and/or photodiodes typically equipped with frequency selective filters and amplifying means, which are not specifically shown. It should be noted that the measurement location may, for example, be accommodated so as to coincide with the location of applying the secondary pressure or slightly differ from it, depending on the kind of measured medium and/or design of the measurement probe.
(A) two substantially U-shaped portions configured for enclosing and holding a portion of a patient's blood perfused flesh medium therebetween, (B) a measuring unit operable for illuminating a measurement location on the portion of the medium with different wavelengths of incident light beams, detecting light responses of the medium, and generating measured data indicative of time evolutions of the light responses of the medium corresponding to the different wavelengths of incident light, respectively; and (C) a pressurizing assembly associated with one of the U-shaped portions and operable for applying a primary over-systolic pressure to the fleshy medium so as to create a condition of artificial blood kinetics in the fleshy medium and maintain this condition for a certain time period; and for applying a secondary controllably varying over-systolic pressure to the fleshy medium, so as to alter said condition of artificial blood kinetics over a predetermined time interval within said certain time period, thereby to modulate scattering properties of blood. There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows hereinafter may be better understood. Additional details and advantages of the invention will be set forth in the detailed description, and in part will be appreciated from the description, or may be learned by practice of the invention.
FIG. 3 illustrates a plot showing three examples of the time dependency of light transmission characteristics of blood experimentally obtained for two different wavelength when the condition of artificial kinetics is altered by a perturbation of the medium by a series of shot pressure pulses;
FIG. 8 illustrate a perspective view of the probe schematically shown in FIG. 6, according to another embodiment of the invention.
According to one general aspect, the present invention provides a novel method and system for non-invasive optical determination of blood characteristics. Examples of the blood characteristics include, but are not limited to concentration of a substance in patient's blood (e.g., glucose, hemoglobin), oxygen saturation, Erythrocyte Sedimentation Rate (ESR) and Erythrocyte Aggregation Rate (EAR). The method is based on creating and controlling the artificial blood kinetics in a patient's blood perfused fleshy medium, e.g., his finger, and applying optical measurements thereto. The condition of artificial kinetics is created and maintained for a certain time period. The condition of artificial kinetics is preferably created by applying a primary over-systolic pressure to a certain location at the medium with a normal blood flow so as to achieve a state of temporary blood flow cessation. The control of the condition of the artificial kinetics is achieved by applying a perturbation of a secondary pressure to the fleshy medium, as will be described in detail hereinbelow.
FIG. 3 illustrates a plot showing three examples (curves 31 and 32) of the time dependency of light transmission characteristics of blood experimentally obtained for three different wavelengths (namely, λ1=670 nm and λ2=810 nm) when the condition of artificial kinetics is altered by a perturbation of the medium by a series of shot secondary pressure pulses. In the example shown in FIG. 3, the duration of the secondary pressure pulses is 1.5 s while the amplitude is in the range of about 220-300 nm Hg. It should be appreciated that in practice the magnitudes of the pulse duration and amplitude depend on the particular patient and configuration of the measurement system.
Referring to FIG. 4, an exemplary plot showing a relationship between the natural logarithm of the light response ln(T1) of the medium at the wavelength λ1=670 nm and the natural logarithm of the light response ln(T2) at the wavelength λ2=810 nm. The measurements were obtained when the condition of artificial kinetics is altered by a perturbation of the medium by a first secondary pressure pulse, i.e., over interval SA1 shown in FIG. 3. As can be seen, the relationship between ln(T1) and ln(T2) is a linear function, and the parametric slope (PS) is determined as the value of tangent of the angle between the line 41 and the abscissa axis. It can be appreciated that for determination of the PS, for example, a known linear regression algorithm can be used. For the example shown in FIG. 4, PS=0.9.
According to the invention, for determination of a desired blood characteristic certain reference data sensitive to patient individuality should be provided. The reference data should be indicative of the desired blood characteristic as a function of the parameter derived from scattering spectral features of the medium. Such reference data can, for example, be a calibration curve defining a dependence of the PS on the desired blood characteristic. The calibration curve can be created by plotting a dependence of the PS versus the desired blood characteristic that can be obtained for the particular individual or various patients by any other known method, independent of the current measurements. It should be appreciated that for different blood characteristics the independent methods may also be different. For example, a calibration curve to be used for determining the oxygen saturation for a specific patient may, in general, be constructed by applying measurements to various patients, and/or by applying the two kinds of measurements for a single patient in a breath hold experiment using a multiple-occlusion mode.
FIG. 8 illustrates the implementation of a probe, denoted 161, according to another embodiment of the invention, wherein the locations L1, L2 and measurement location ML substantially coincide. According to this embodiment, the probe 161 has two portions 81 and 82 each of a substantially U-shaped cross-section arranged with respect to each other for enclosing and holding therebetween a portion of the patient's finger (not shown in FIG. 8). The U-shape parts 81 and 82 are made of a rigid or semi-rigid material, such as metal or plastic. In the cross-section, the U-shape parts 81 and 82 can, for example, be of semi-circle or semi-oval forms. The parts 81 and 82 can partially overlap over a predetermined distance. The probe 161 comprises a pressurizing assembly 801 that includes an air cushion 83 associated with a drive mechanism (not shown) and operable to apply pressure to the finger portion enclosed between the parts 81 and 82. By moving the upper and lower parts 81 and 82 of the probe towards each other, a position of a finger therebetween is fixed. Then, a locking device 86 further fixes the parts 81 and 82 to thereby apply a certain preliminary pressure to start the measurement procedure. The locking device may be implemented by any suitable known means (e.g., including a teeth arrangement and a spring assembly) and is aimed at preventing the opening of the ring-like probe. Then, a cushion 83, which in the present example is associated with the lower semi-ring 81, is operated to press the finger to the upper semi-ring 82 to thereby apply an over-systolic pressure (e.g., 220-250 mm Hg) to thereby create a blood flow cessation in the finger and enable measurements. Then, a higher secondary pressure is supplied through the cushion 83. Thus, according to this embodiment of the invention, the primary over-systolic pressure as well as the secondary pressure is applied to the same location on the finger via the same pressurizing assembly (cushion 83). Therefore, the location of the main occlusion providing the over-systolic pressure coincides with the location at which the artificial blood kinetics is altered.
The probe 161 further comprises a measuring unit 802 configured for illuminating a measurement location on the portion of the finger with incident light beams, detecting light responses of the medium (at different wavelengths of incident light), and generating measured data indicative of time evolutions of the light responses of the blood. As described above, incident light beams being of at least two different wavelengths in a range where the scattering properties of blood are sensitive to the light radiation. The measuring unit 802 includes an illumination assembly 84 mounted on a holding frame 84 and a light collection/detection assembly 85. Similar to the previously described example, the illumination assembly 84 can include a plurality of light sources (e.g., LEDs) associated with a suitable drive mechanism (not shown) operated by the control unit (62 in FIG. 6), or a single broad band illuminator. The light sources radiate the measurement location of the finger through an aperture (not seen in FIG. 8) arranged in the part 82 to provide unobstructed optical transmission to the surface of the finger.
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