Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS20030023140 A1
Publication typeApplication
Application numberUS 10/174,482
Publication date30 Jan 2003
Filing date18 Jun 2002
Priority date6 Feb 1989
Also published asUS6183414
Publication number10174482, 174482, US 2003/0023140 A1, US 2003/023140 A1, US 20030023140 A1, US 20030023140A1, US 2003023140 A1, US 2003023140A1, US-A1-20030023140, US-A1-2003023140, US2003/0023140A1, US2003/023140A1, US20030023140 A1, US20030023140A1, US2003023140 A1, US2003023140A1
InventorsBritton Chance
Original AssigneeBritton Chance
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Pathlength corrected oximeter and the like
US 20030023140 A1
Abstract
A pathlength corrected spectrophotometer for tissue examination includes an oscillator for generating a carrier waveform of a selected frequency, an LED light source for generating light of a selected wavelength that is intensity modulated at the selected frequency introduced to a subject, and a photodiode detector for detecting light that has migrated in the tissue of the subject. The spectrophotometer also includes a phase detector for measuring a phase shift between the introduced and detected light, a magnitude detector for determination of light attenuation in the examined tissue, and a processor adapted to calculate the photon migration pathlength and determine a physiological property of the examined tissue based on the pathlength and on the attenuation data.
Images(6)
Previous page
Next page
Claims(21)
1. A spectrophotometer for tissue examination utilizing a measured average pathlength of migrating photons, comprising:
an oscillator adapted to generate a carrier waveform of a selected frequency comparable to an average migration time of photons scattered in tissue on paths from an optical input port to an optical detection port;
a light source, operatively connected to said oscillator, adapted to generate light of a selected wavelength that is intensity modulated at said frequency, said light being introduced to a subject at said input port;
a photodiode detector adapted to detect, at said detection port, light of said wavelength that has migrated in said tissue of the subject between said input and detection ports;
a phase detector, operatively connected to receive signals from said oscillator and said diode detector, adapted to measure a phase shift between said introduced and said detected light;
a processor adapted to determine said pathlength based on said phase shift; and
said processor further adapted to determine a physiological property of the examined tissue based on said pathlength.
2. A spectrophotometer for tissue examination utilizing a measured average pathlength of migrating photons, comprising:
an oscillator adapted to generate a carrier waveform of a selected frequency comparable to an average migration time of photons scattered in tissue on paths from an optical input port to an optical detection port;
a light source, operatively connected to said oscillator, adapted to generate light of a selected wavelength that is intensity modulated at said frequency, said light being introduced to a subject at said input port;
a photodiode detector adapted to detect, at said detection port, light of said wavelength that has migrated in said tissue of the subject between said input and detection ports;
a phase splitter adapted to produce, based on said carrier waveform, first and second reference phase signals of predefined substantially different phase;
first and second double balanced mixers adapted to correlate said reference phase signals and signals of said detected radiation to produce therefrom a real output signal and an imaginary output signal, respectively;
a processor adapted to determine, on the basis of said real output signal and said imaginary output signal, a phase shift between said introduced light and said detected light; and
said processor further adapted to determine a physiological property of the examined tissue based on said phase shift.
3. A spectrophotometer for tissue examination utilizing a measured average pathlength of migrating photons, comprising:
a first oscillator adapted to generate a carrier waveform of a first selected frequency comparable to an average migration time of photons scattered in tissue on paths from an optical input port to an optical detection port;
a light source, operatively connected to said oscillator, adapted to generate light of a selected wavelength that is intensity modulated at said first frequency, said light being introduced to a subject at said input port;
a photodiode detector adapted to detect, at said detection port, light of said wavelength that has migrated in said tissue of the subject between said input and detection ports, said detector producing a detection signal at said first frequency corresponding to said detected light;
a second oscillator adapted to generate a carrier waveform of a second frequency that is offset on the order of 104 Hz from said first frequency;
a reference mixer, connected to said first and second oscillators, adapted to generate a reference signal of a frequency approximately equal to the difference between said first and second frequencies;
a mixer connected to receive signals from said second oscillator and said detection signal and adapted to convert said detection signal to said difference frequency;
a phase detector, operatively connected to receive signals from said reference mixer and said converted detection signal, adapted to measure a phase shift between said introduced light and said detected light,
a processor adapted to determine said pathlength based on said phase shift; and
said processor further adapted to determine a physiological property of the examined tissue based on said pathlength.
4. The spectrophotometer of claims 1, 2 or 3 further comprising:
a magnitude detector, connected to said photodiode detector, adapted to measure magnitude of said detected light, and
said processor further adapted to receive said magnitude for determination of said physiological property.
5. The spectrophotometer of claims 1, 2 or 3 further comprising:
a low frequency oximeter circuit, switchably connected to said source and said photodiode, adapted to determine absorption of light at said wavelength; and
said processor further adapted to receive absorption values from said oximeter circuit for determination of said physiological property.
6. The spectrophotometer of claims 1 or 3 further comprising two automatic gain controls adapted to level signals corresponding to said introduced light and said detected light, both said leveled signals being introduced to said phase detector.
7. The spectrophotometer of claims 1 or 3 further comprising:
a magnitude detector, connected to said photodiode detector, adapted to measure magnitude of said detected light, and
two automatic gain controls adapted to level signals corresponding to said introduced light and said detected light, both said leveled signals being introduced to said phase detector.
8. The spectrophotometer of claims 1, 2 or 3 wherein said light source is a light emitting diode and said selected wavelength is in the visible or infra-red range.
9. The spectrophotometer of claims 1, 2 or 3 wherein said photodiode detector is a PIN diode.
10. The spectrophotometer of claims 1, 2 or 3 wherein said photodiode detector is an avalanche diode.
11. The spectrophotometer of claims 1, 2 or 3 wherein said photodiode detector further comprises a substantially single wavelength filter.
12. The spectrophotometer of claims 1, 2 or 3 further comprising:
a second light source, operatively connected to said oscillator, adapted to generate light of a second selected wavelength that is intensity modulated at said first frequency, said radiation being introduced to a subject at a second input port;
said photodiode detector further adapted to detect alternately, at said detection port, light of said first and second wavelengths that have migrated in said tissue of the subject between the first and said second input ports and said detection port, respectively;
said phase detector further adapted to receive alternately signals corresponding to said detected first and second wavelengths; and
said processor further adapted to receive alternately phase shifts from said phase detector, said phase shifts being subsequently used for determination of said physiological property.
13. The spectrophotometer of claim 12 further comprising:
a magnitude detector, connected to said photodiode detector, adapted to measure magnitude of said detected light at each of said wavelengths, and
said processor further adapted to receive said magnitudes for determination of said physiological property.
14. The spectrophotometer of claims 1 or 3 further comprising:
a second light source, operatively connected to said oscillator, adapted to generate light of a second selected wavelength that is intensity modulated at said first frequency, said radiation being introduced to a subject at a second input port;
a second photodiode detector adapted to detect, at a second detection port, light of said second wavelength that has migrated in said tissue of the subject between said second input port and said second detection port, respectively;
a second phase detector, operatively connected to receive a reference signal and a detection signal from said third diode detector, adapted to measure a phase shift between said introduced and said detected light at said second wavelength; and
said processor further adapted to receive a second phase shift at said second wavelength, said first and second phase shifts being subsequently used for determination of said physiological property.
15. The spectrophotometer of claim 14 further comprising:
a first and a second magnitude detector connected to said first and second photodiode detectors, respectively, said magnitude detectors being adapted to measure magnitude of said detected light at each of said wavelengths, and
said processor further adapted to receive said magnitudes for determination of said physiological property.
16. The spectrophotometer of claims 14 further comprising:
a third light source, operatively connected to said oscillator, adapted to generate light of a third selected wavelength that is intensity modulated at said first frequency, said radiation being introduced to a subject at a third input port;
a third photodiode detector adapted to detect, at a third detection port, light of said third wavelength that has migrated in said tissue of the subject between said third input port and said third detection port, respectively;
a third phase detector, operatively connected to receive a reference signal and a detection signal from said third diode detector, adapted to measure a phase shift between said introduced and said detected light at said third wavelength; and
said processor further adapted to receive phase shifts from said phase detector, said first second and third phase shifts being subsequently used for determination of said physiological property.
17. The spectrophotometer of claim 14 further comprising:
a first, a second and a third magnitude detector connected to said first, second and third photodiode detectors, respectively, said magnitude detectors being adapted to measure magnitude of said detected light at each of said wavelengths; and
said processor further adapted to receive said magnitudes for determination of said physiological property.
18. The spectrophotometer of claim 16 wherein each said light source is a light emitting diode and said selected wavelength is in the visible or infra-red range.
19. The spectrophotometer of claim 16 wherein each said photodiode detector is a PIN diode.
20. The spectrophotometer of claim 16 wherein each said photodiode detector is an avalanche diode.
21. The spectrophotometer of claim 16 wherein each said photodiode detector further comprises a substantially single wavelength filter.
Description
    CROSS REFERENCE TO RELATED APPLICATION
  • [0001]
    This application is a continuation-in-part of application Ser. No. 07/645,590 filed Jan. 24, 1991 incorporated by reference as if fully set forth herein.
  • BACKGROUND OF THE INVENTION
  • [0002]
    The present invention relates to a wearable tissue spectrophotometer for in vivo examination of tissue of a specific target region.
  • [0003]
    Continuous wave (CW) tissue oximeters have been widely used to determine in vivo concentration of an optically absorbing pigment (e.g., hemoglobin, oxyhemoglobin) in biological tissue. The CW oximeters measure attenuation of continuous light in the tissue and evaluate the concentration based on the Beer Lambert equation or modified Beer Lambert absorbance equation. The Beer Lambert equation (1) describes the relationship between the concentration of an absorbent constituent (C), the extinction coefficient (ε), the photon migration pathlength <L>, and the attenuated light intensity (I/Io). log [ I / I 0 ] L = ε i C i ( 1 )
  • [0004]
    The CW spectrophotometric techniques can not determine ε, C, and <L> at the same time. If one could assume that the photon pathlength were constant and uniform throughout all subjects, direct quantitation of the constituent concentration (C) using CW oximeters would be possible.
  • [0005]
    In tissue, the optical migration pathlength varies with the size, structure, and physiology of the internal tissue examined by the CW oximeters. For example, in the brain, the gray and white matter and the structures thereof are different in various individuals. In addition, the photon migration pathlength itself is a function of the relative concentration of absorbing constituents. As a result, the pathlength through an organ with a high blood hemoglobin concentration, for example, will be different from the same with a low blood hemoglobin concentration. Furthermore, the pathlength is frequently dependent upon the wavelength of the light since the absorption coefficient of many tissue constituents is wavelength dependent. Thus, where possible, it is advantageous to measure the pathlength directly when quantifying the hemoglobin concentration in tissue.
  • SUMMARY OF THE INVENTION
  • [0006]
    In one aspect, the present invention is a pathlength corrected oximeter that utilizes principles of continuous wave spectroscopy and phase modulation spectroscopy. The oximeter is a compact unit constructed to be worn by a subject on the body over long periods of activity. The oximeter is also suitable for tissue monitoring in critical care facilities, in operating rooms while undergoing surgery or in trauma related situations.
  • [0007]
    The oximeter is mounted on a body-conformable support structure placed on the skin. The support structure encapsulates several light emitting diodes (LEDs) generating light of different wavelengths introduced into the examined tissue and several photodiode detectors with interference filters for wavelength specific detection. Since both the LEDs and the photodiodes are placed directly on the skin, there is no need to use optical fibers. The distance between the LEDs and the diode detectors is selected to examine a targeted tissue region. The support structure also includes a conformable barrier, located between the LEDs and the diode detectors, designed to reduce detection of light that migrates subcutaneously from the source to the detector. The support structure may further include means for preventing escape of photons from the skin without being detected; the photon escape preventing means are located around the LEDs and the photodiode detectors.
  • [0008]
    The LEDs, the diode detectors, and the electronic control circuitry of the oximeter are powered by a battery pack adapted to be worn on the body or by the standard 50/60 Hz supply. The electronic circuitry includes a processor for directing operation of the sources, the detectors and for directing the data acquisition and processing. The data may be displayed on a readout device worn by the user, sent by telemetry to a remote location or accumulated in a memory for later use.
  • [0009]
    The oximeter is adapted to measure the attenuation of light migrating from the source to the detector and also to determine the average migration pathlength. The migration pathlength and the intensity attenuation data are then used for direct quantitation of a tissue property.
  • [0010]
    In another aspect, the invention is a spectrophotometer for tissue examination utilizing a measured average pathlength of migrating photons, including
  • [0011]
    an oscillator adapted to generate a carrier waveform of a selected frequency comparable to an average migration time of photons scattered in tissue on paths from an optical input port to an optical detection port; a light source, operatively connected to the oscillator, adapted to generate light of a selected wavelength that is intensity modulated at the frequency and introduced to a subject at the input port; a photodiode detector adapted to detect, at the detection port, light of the selected wavelength that has migrated in the tissue of the subject between the input and detection ports; a phase detector, operatively connected to receive signals from the oscillator and the diode detector, adapted to measure a phase shift between the introduced and the detected light; and a processor adapted to calculate pathlength based on the phase shift, and determine a physiological property of the examined tissue based on the pathlength.
  • [0012]
    In another aspect, the invention is a spectrophotometer for tissue examination utilizing a measured average pathlength of migrating photons, including an oscillator adapted to generate a carrier waveform of a selected frequency comparable to an average migration time of photons scattered in tissue on paths from an optical input port to an optical detection port; a light source, operatively connected to the oscillator, adapted to generate light of a selected wavelength that is intensity modulated at the frequency and introduced to a subject at the input port; a photodiode detector adapted to detect, at the detection port, light of the selected wavelength that has migrated in the tissue of the subject between the input and detection ports; a phase splitter adapted to produce, based on the carrier waveform, first and second reference phase signals of predefined substantially different phase; first and second double balanced mixers adapted to correlate the reference phase signals and signals of the detected radiation to produce therefrom a real output signal and an imaginary output signal, respectively; and a processor adapted to calculate, on the basis of the real output signal and the imaginary output signal, a phase shift between the introduced light and the detected light, and determine a physiological property of the examined tissue based on the phase shift.
  • [0013]
    In another aspect, the invention is a spectrophotometer for tissue examination utilizing a measured average pathlength of migrating photons, comprising a first oscillator adapted to generate a carrier waveform of a first selected frequency comparable to an average migration time of photons scattered in tissue on paths from an optical input port to an optical detection port; a light source, operatively connected to the oscillator, adapted to generate light of a selected wavelength, intensity modulated at the first frequency, that is introduced to a subject at the input port; a photodiode detector adapted to detect, at the detection port, light of the wavelength that has migrated in the tissue of the subject between the input and detection ports, the detector producing a detection signal at the first frequency corresponding to the detected light; a second oscillator adapted to generate a carrier waveform of a second frequency that is offset on the order of 104 Hz from the first frequency; a reference mixer, connected to the first and second oscillators, adapted to generate a reference signal of a frequency approximately equal to the difference between the first and second frequencies; a mixer connected to receive signals from the second oscillator and the detection signal and adapted to convert the detection signal to the difference frequency; a phase detector, operatively connected to receive signals from the reference mixer and the converted detection signal, adapted to measure a phase shift between the introduced light and the detected light; and a processor adapted to calculate the pathlength based on the phase shift, and to determine a physiological property of the examined tissue based on the pathlength.
  • [0014]
    Preferred embodiments of these aspects may include one or more of the following features.
  • [0015]
    The spectrophotometer may further include a magnitude detector, connected to the photodiode detector, adapted to measure magnitude of the detected light, and the processor is further adapted to receive the magnitude for determination of the physiological property.
  • [0016]
    The spectrophotometer may further include a low frequency oximeter circuit, switchably connected to the source and the photodiode, adapted to determine absorption of light at the wavelength; and the processor is further adapted to receive absorption values from the oximeter circuit for determination of the physiological property.
  • [0017]
    The spectrophotometer may further include two automatic gain controls adapted to level signals corresponding to the introduced light and the detected light, both the leveled signals being introduced to the phase detector.
  • [0018]
    The photodiode detector may further include a substantially single wavelength filter.
  • [0019]
    The spectrophotometer may further include a second light source, operatively connected to the oscillator, adapted to generate light of a second selected wavelength that is intensity modulated at the first frequency, the radiation being introduced to a subject at a second input port; the photodiode detector further adapted to detect alternately, at the detection port, light of the first and second wavelengths that have migrated in the tissue of the subject between the first and the second input ports and the detection port, respectively; the phase detector further adapted to receive alternately signals corresponding to the detected first and second wavelengths; and the processor further adapted to receive alternately phase shifts from the phase detector, the phase shifts being subsequently used for determination of the physiological property of the tissue.
  • [0020]
    The spectrophotometer may further include a second light source, operatively connected to the oscillator, adapted to generate light of a second selected wavelength that is intensity modulated at the first frequency, the radiation being introduced to a subject at a second input port; a second photodiode detector adapted to detect, at a second detection port, light of the second wavelength that has migrated in the tissue of the subject between the second input port and the second detection port, respectively; a second phase detector, operatively connected to receive a reference signal and a detection signal from the third diode detector, adapted to measure a phase shift between the introduced and the detected light at the second wavelength; and the processor further adapted to receive a second phase shift at the second wavelength, the first and second phase shifts being subsequently used for determination of the physiological property of the tissue.
  • [0021]
    The two wavelength spectrophotometer may further include a third light source, operatively connected to the oscillator, adapted to generate light of a third selected wavelength that is intensity modulated at the first frequency, the radiation being introduced to a subject at a third input port; a third photodiode detector adapted to detect, at a third detection port, light of the third wavelength that has migrated in the tissue of the subject between the third input port and the third detection port, respectively; a third phase detector, operatively connected to receive a reference signal and a detection signal from the third diode detector, adapted to measure a phase shift between the introduced and the detected light at the third wavelength; and the processor further adapted to receive phase shifts from the phase detector, the first second and third phase shifts being subsequently used for determination of the physiological property of the tissue.
  • [0022]
    The two or three wavelength spectrophotometer may further include a first, a second (or a third) magnitude detector connected to the first, second (or third) photodiode detectors, respectively, the magnitude detectors being adapted to measure magnitude of the detected light at each of the wavelengths; and the processor further adapted to receive the magnitudes for determination of the physiological property of the tissue.
  • [0023]
    The light source may be a light emitting diode for generating light of a selected wavelength in the visible or infra-red range.
  • [0024]
    The photodiode detector may be a PIN diode or an avalanche diode.
  • [0025]
    The examined physiological property of the tissue may be hemoglobin oxygenation, myoglobin, cytochrome iron and copper, melanin, glucose or other.
  • BRIEF DESCRIPTION OF THE DRAWING
  • [0026]
    [0026]FIG. 1 is a block diagram of a pathlength corrected oximeter in accordance with the present invention.
  • [0027]
    [0027]FIG. 2 is a schematic circuit diagram of a 50.1 MHz (50.125 MHz) oscillator used in the oximeter of FIG. 1.
  • [0028]
    [0028]FIG. 3 is a schematic circuit diagram of a PIN diode and a preamplifier used in the oximeter of FIG. 1.
  • [0029]
    [0029]FIG. 4 is a schematic circuit diagram of a magnitude detector used in the oximeter of FIG. 1.
  • [0030]
    [0030]FIG. 5 is a schematic circuit diagram of a 25 kHz filter used in the oximeter of FIG. 1.
  • [0031]
    [0031]FIG. 6 is a schematic diagram of an AGC circuit of the oximeter of FIG. 1.
  • [0032]
    [0032]FIG. 7 is a schematic circuit diagram of a phase detector of the oximeter of FIG. 1.
  • [0033]
    [0033]FIG. 8A is a plan view of a source-detector probe of the oximeter.
  • [0034]
    [0034]FIG. 8B is a transverse cross-sectional view taken on lines 8B of FIG. 8A further showing the photon migration.
  • DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • [0035]
    One preferred embodiment of the pathlength corrected oximeter utilizes three LEDs for generation of light at three selected wavelengths intensity modulated at a frequency of 50.1 MHz and coupled directly to the examined tissue. At each wavelength, the introduced light is altered by the tissue and is detected by a wide area photodiode placed against the skin. The introduced and detected radiations are compared to determine their relative phase shift that corresponds to an average pathlength of the migrating photons and, furthermore, the light attenuation is determined.
  • [0036]
    Referring to FIG. 1, the oximeter includes a master oscillator 10 operating at 50.1 MHz connected to a power amplifier 15 of sufficient output power to drive LEDs 22 a, 22 b, and 22 c (for example HLP 20RG or HLP 40RG made by Hitachi) that emit 760 nm, 840 nm, and 905 nm (or 950 nm) light, respectively. A second local oscillator 14 operating at 50.125 MHz and mixer 12 are used to generate a reference frequency 13 of 25 kHz. Each LED directly positioned on the skin has an appropriate heat sink to eliminate uncomfortable temperature increases that could also alter blood perfusion of the surrounding tissue. Three PIN diode detectors 24 a, 24 b, and 24 c are placed at a distance of approximately 5 cm from the LEDs and have a detection area of about 1 cm2. Photons migrating a few centimeters deep into the tissue are detected by the respective PIN diodes. The source-detector separation can be increased or decreased to capture deeper or shallower migrating photons. The signals from PIN diodes 24 a, 24 b, and 24 c are amplified by preamplifiers 30 a, 30 b, and 30 c, respectively.
  • [0037]
    The amplified signals (32 a, 32 b, 32 c) are sent to magnitude detectors 36 a, 36 b, and 36 c and to mixers 40 a, 40 b, and 40 c, respectively. The magnitude detectors are used to determine intensity values of detected signals at each wavelength to be used in Eq. 1. Each mixer, connected to receive a 50.125 MHz reference signal (41 a, 41 b, 41 c) from local oscillator 14, converts the detection signal to a 25 kHz frequency signal (42 a, 42 b, 42 c). The mixers are high dynamic range frequency mixers, model SRA-1H, commercially available from Mini-Circuits (Brooklyn N.Y.). The detection signals (42 a, 42 b, and 42 c) are filtered by filters 45 a, 45 b, 45 c, respectively.
  • [0038]
    Phase detectors 60 a, 60 b, and 60 c are used to determine phase shift between the input signal and the detected signal at each wavelength. Each phase detector receives the 25 kHz detection signal (54 a, 54 b, 54 c) and the 25 kHz reference signal (56 a, 56 b, 56 c), both of which are automatically leveled by automatic gain controls 50 and 52 to cover the dynamic range of signal changes. Phase detectors 60 a, 60 b, and 60 c generate phase shift signals (62 a, 62 b, 62 c) corresponding to the migration delay of photons at each wavelength. Each phase shift signal is proportional to the migration pathlength used in calculation algorithms performed by processor 70.
  • [0039]
    [0039]FIG. 2 shows a schematic circuit diagram of a precision oscillator used as the 50.1 MHz master oscillator 10 and 50.125 MHz local oscillator 14. The oscillator crystals are neutralized for operation in the fundamental resonance mode; this achieves long-term stability. Both oscillators are thermally coupled so that their frequency difference is maintained constant at 25 kHz if a frequency drift occurs.
  • [0040]
    PIN diodes 24 a, 24 b, and 24 c are directly connected to their respective preamplifiers 30 a, 30 b, and 30 c, as shown in FIG. 3. The oximeter uses PIN silicon photodiodes S1723-04 with 10 mm10 mm sensitive area and spectral response in the range of 320 nm to 1060 nm. The detection signal is amplified by stages 29 and 31, each providing about 20 dB amplification. The NE5205N operational amplifier is powered at +8V to operate in a high gain regime. The 8V signal is supplied by a voltage regulator 33. The amplified detection signals (32 a, 32 b, and 32 c) are sent to magnitude detectors 36 a, 36 b, and 36 c, shown in FIG. 4. The magnitude values (37 a, 37 b, and 37 c) are sent to processor 70 that calculates the light attenuation ratio or logarithm thereof as shown Eq. 1.
  • [0041]
    Also referring to FIG. 5, the AGC circuit uses MC 1350 integrated circuit for amplification that maintains the input signal of phase detector 60 at substantially constant levels. The amount of gain is selected to be equal for AGCs, 50 and 52. The signal amplitude is controlled by a feedback network 53. The AGCs provide a substantially constant amplitude of the detected and reference signals to eliminate variations in the detected phase shift due to cross talk between amplitude and phase changes in the phase detector.
  • [0042]
    Referring to FIG. 6, each phase detector includes a Schmitt trigger that converts the substantially sinusoidal detection signal (54 a, 54 b, 54 c) and reference signal (56 a, 56 b, 56 c) to square waves. The square waves are input to a detector that has complementary MOS silicon-gate transistors. The phase shift signal is sent to processor 70.
  • [0043]
    The oximeter is calibrated by measuring the phase shift for a selected distance in a known medium, i.e., using a standard delay unit, and by switching the length of a connector wire to change the electrical delay between master oscillator 10 and local oscillator 14.
  • [0044]
    Referring to FIGS. 8A and 8B source-detector probe 20 includes several LEDs (22 a, 22 b, 22 c) of selected wavelengths and PIN photodiodes (24 a, 24 b, 24 c) mounted in a body-conformable support structure 21. Structure 21 also includes a photon escape barrier 27 made of a material with selected scattering and absorption properties (for example, styrofoam) designed to return escaping photons back to the examined tissue. The support structure further includes a second conformable barrier 28, located between the LEDs and the diode detectors, designed to absorb photons directly propagating from the source to the detector and thus prevent detection of photons that migrate subcutaneously. Support structure 21 also includes electronic circuitry 29 encapsulated by an electronic shield 21 a.
  • [0045]
    Each PIN diode is provided with an evaporated single wavelength film filter (25 a, 25 b, 25 c). The filters eliminate the cross talk of different wavelength signals and allow continuous operation of the three light sources, i.e., no time sharing is needed.
  • [0046]
    The use of photodiode detectors has substantial advantages when compared with the photomultiplier tube used in standard phase modulation systems. The photodiodes are placed directly on the skin, i.e., no optical fibers are needed. Furthermore, there is no need to use a high voltage power supply that is necessary for the photomultiplier tube. The photodiodes are much smaller and are easy to place close to the skin. Advantages of the photomultiplier tube are a huge multiplication gain and a possibility of direct mixing at the photomultiplier; this cannot be achieved directly by a photodiode. This invention envisions the use of several different photodiodes such as PIN diode, avalanche diode, and other.
  • [0047]
    The processor uses algorithms that are based on equations described by E. M. Sevick et al. in “Quantitation of Time- and Frequency-Resolved Optical Spectra for the Determination of Tissue Oxygenation” published in Analytical Biochemistry 195, 330 Apr. 15, 1991 which is incorporated by reference as if fully set forth herein.
  • [0048]
    At each wavelength, the phase shift (θλ) (62 a, 62 b, 62 c) is used to calculate the pathlength as follows: θ λ = tan - 1 π f ( t λ ) = tan - 1 2 π f L λ c 2 π f L λ c ( 2 )
  • [0049]
    wherein f is modulation frequency of the introduced light which is in the range of 10 MHz to 100 MHz; tλ is the photon migration delay time; c is the speed of photons in the scattering medium; and Lλ is the migration pathlength.
  • [0050]
    Equation (2) is valid at low modulation frequencies, i.e., 2πf<<μac. The modulation frequency of 50 MHz was selected due to the frequency limitation of the LEDs and photodiodes. However, for faster LEDs and photodiodes it may be desirable to use higher modulation frequencies that increase the phase shift. At high modulation frequencies, i.e., 2πf>>μac, the phase shift is no longer proportional to the mean time of flight <t>. θ λ = a ρ ( 1 - g ) μ s f { 1 - μ a λ c 4 π f } ( 3 )
  • [0051]
    wherein ρ is the source-detector separation; (1−g) μs is effective scattering coefficient; f is modulation frequency and μa λ is absorption coefficient at wavelength λ. At two wavelength, the ratio of absorption coefficients is determined as follows: μ a λ 1 μ a λ 2 = θ λ 1 - θ 0 λ 1 θ λ 2 - θ 0 λ 2 ( 4 )
  • [0052]
    wherein θ0 λ represents background scattering and absorption.
  • [0053]
    The wavelengths are in the visible and infra-red range and are selected to have absorbance sensitive (or insensitive) to various tissue components such as water, cytochrome iron and copper, oxy- and deoxygenated forms of hemoglobin, myoglobin, melanin, glucose and other.
  • [0054]
    For oxygenated and deoxygenated hemoblogin, the absorption coefficient written in terms of Beer Lambert relationship is as follows: μ a λ 1 = ε H b λ 1 [ H b ] + ε H b O λ 1 [ H b O 2 ] + α λ 1 ( 5 )
  • [0055]
    wherein εHb λ1 and εHb0 λ1 are extinction coefficients for hemoglobin and deoxyhemoglobin that can be stored in a look up table; [Hb], [HbO2] are the tissue concentration of hemoglobin and oxyhemoglobin, respectively; αλ1 is background absorbance. The hemoglobin saturation is conventionally defined as follows: Y = [ H b O 2 ] [ H b ] + [ H b O 2 ] ( 6 )
  • [0056]
    For a three wavelength measurement, the hemoglobin saturation can be calculated using Eqs. (5) and (6) as follows: Y = a ( ε H b λ 3 - ε H b λ 2 ) - ( ε H b λ 1 - ε H b λ 2 ) [ ( ε H b O 2 λ 1 - ε H b O 2 λ 2 ) - ( ε H b λ 1 - ε H b λ 2 ) ] - a [ ( ε H b O 2 λ 3 - ( ε H b O 2 λ 2 ) - ( ε H b λ 3 - ε H b λ 2 ) ] w h e r e a = μ a λ 1 - μ a λ 2 μ a λ 3 - μ a λ 2 ( 7 )
  • [0057]
    Thus, processor 70 determines Y based on Eq. (7) using Eq. (2) to determine the average migration pathlength L that is then used in Eq. (1) and to determine μa λ for each wavelength λ1, λ2, λ3.
  • [0058]
    In another embodiment, the spectrophotometer's electronics includes a low frequency module suitably and a high frequency module switchably coupled to the same source-detector probe 20. The low frequency module and the arrangement of the source-detector probe are substantially similar to the hemoglobinometer described in a copending U.S. patent application Ser. No. 701,127 filed May 16, 1991 which is incorporated by reference as if fully set forth herein. The low frequency module corresponds to a standard oximeter with modulation frequencies in the range of a few hertz to 104 hertz and is adapted to provide intensity attenuation data at two or three wavelengths. Then, the LEDs are switched to the high frequency phase modulation unit, similar to the unit of FIG. 1, which determines the average pathlength at each wavelength. The attenuation and pathlength data are sent to processor 70 for determination of a physiological property of the examined tissue.
  • [0059]
    In another embodiment, the pathlength corrected oximeter utilizes the same LED sources (22 a, 22 b, 22 c) sinusoidally modulated at a selected frequency comparable to the average migration time of photons scattered in the examined tissue on paths from the optical input port of the LED's to the optical detection part of the photodiode detectors (24 a, 24 b, 24 c), but the electronic circuitry is different. The detector output is put through two wide band double balance mixers (DBM) which are coupled through a 90 phase splitter so that real (R) and imaginary (I) portions of the signal are obtained. The double balance mixers preferably operate at the modulation frequency. The phase (θλ) is the angle whose tangent is the imaginary over the real part. θ λ = tan - 1 I λ R λ ( 8 )
  • [0060]
    The amplitude is the square root of the sum of the squares of these values, providing the phase shift has been taken out as the residual phase shift θ set to zero.
  • A λ={square root}{square root over ((R λ)2+(I λ)2)}  (9)
  • [0061]
    This embodiment uses summing and dividing circuits to calculate the modulation index, which is the quotient of the amplitude over the amplitude plus the DC component obtained from a narrow band detector. M λ = A λ A λ + D C λ ( 10 )
  • [0062]
    The phase processor receives the phase shifts for the phase and amplitude values for two or three wavelengths and calculates the ratio of the phase shifts.
  • [0063]
    For each wavelength, the phase shift and the DC amplitude are used to determine a selected tissue property, e.g., hemoglobin oxygenation.
  • [0064]
    Additional embodiments are within the following claims:
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US769800229 Sep 200613 Apr 2010Nellcor Puritan Bennett LlcSystems and methods for user interface and identification in a medical device
US769890913 Feb 200420 Apr 2010Nellcor Puritan Bennett LlcHeadband with tension indicator
US770689629 Sep 200627 Apr 2010Nellcor Puritan Bennett LlcUser interface and identification in a medical device system and method
US772051616 Nov 200418 May 2010Nellcor Puritan Bennett LlcMotion compatible sensor for non-invasive optical blood analysis
US772514629 Sep 200525 May 2010Nellcor Puritan Bennett LlcSystem and method for pre-processing waveforms
US772514729 Sep 200525 May 2010Nellcor Puritan Bennett LlcSystem and method for removing artifacts from waveforms
US780942026 Jul 20065 Oct 2010Nellcor Puritan Bennett LlcHat-based oximeter sensor
US781377926 Jul 200612 Oct 2010Nellcor Puritan Bennett LlcHat-based oximeter sensor
US782245328 Jul 200626 Oct 2010Nellcor Puritan Bennett LlcForehead sensor placement
US784889129 Sep 20067 Dec 2010Nellcor Puritan Bennett LlcModulation ratio determination with accommodation of uncertainty
US787712626 Jul 200625 Jan 2011Nellcor Puritan Bennett LlcHat-based oximeter sensor
US787712726 Jul 200625 Jan 2011Nellcor Puritan Bennett LlcHat-based oximeter sensor
US78901543 Dec 200815 Feb 2011Nellcor Puritan Bennett LlcSelection of ensemble averaging weights for a pulse oximeter based on signal quality metrics
US789950928 Jul 20061 Mar 2011Nellcor Puritan Bennett LlcForehead sensor placement
US792266528 Sep 200612 Apr 2011Nellcor Puritan Bennett LlcSystem and method for pulse rate calculation using a scheme for alternate weighting
US792551129 Sep 200612 Apr 2011Nellcor Puritan Bennett LlcSystem and method for secure voice identification in a medical device
US797910221 Feb 200612 Jul 2011Nellcor Puritan Bennett LlcHat-based oximeter sensor
US80074417 May 200930 Aug 2011Nellcor Puritan Bennett LlcPulse oximeter with alternate heart-rate determination
US806497520 Sep 200622 Nov 2011Nellcor Puritan Bennett LlcSystem and method for probability based determination of estimated oxygen saturation
US806889029 Sep 200629 Nov 2011Nellcor Puritan Bennett LlcPulse oximetry sensor switchover
US806889129 Sep 200629 Nov 2011Nellcor Puritan Bennett LlcSymmetric LED array for pulse oximetry
US809299318 Dec 200810 Jan 2012Nellcor Puritan Bennett LlcHydrogel thin film for use as a biosensor
US80951922 Dec 200510 Jan 2012Nellcor Puritan Bennett LlcSignal quality metrics design for qualifying data for a physiological monitor
US811237527 Mar 20097 Feb 2012Nellcor Puritan Bennett LlcWavelength selection and outlier detection in reduced rank linear models
US813317630 Sep 200513 Mar 2012Tyco Healthcare Group LpMethod and circuit for indicating quality and accuracy of physiological measurements
US814027227 Mar 200920 Mar 2012Nellcor Puritan Bennett LlcSystem and method for unmixing spectroscopic observations with nonnegative matrix factorization
US816066829 Sep 200617 Apr 2012Nellcor Puritan Bennett LlcPathological condition detector using kernel methods and oximeters
US816068330 Dec 201017 Apr 2012Nellcor Puritan Bennett LlcSystem and method for integrating voice with a medical device
US816072616 Feb 201017 Apr 2012Nellcor Puritan Bennett LlcUser interface and identification in a medical device system and method
US817566729 Sep 20068 May 2012Nellcor Puritan Bennett LlcSymmetric LED array for pulse oximetry
US817567015 Sep 20068 May 2012Nellcor Puritan Bennett LlcPulse oximetry signal correction using near infrared absorption by water
US819526226 Jul 20065 Jun 2012Nellcor Puritan Bennett LlcSwitch-mode oximeter LED drive with a single inductor
US819526318 Sep 20075 Jun 2012Nellcor Puritan Bennett LlcPulse oximetry motion artifact rejection using near infrared absorption by water
US820456713 Dec 200719 Jun 2012Nellcor Puritan Bennett LlcSignal demodulation
US822131925 Mar 200917 Jul 2012Nellcor Puritan Bennett LlcMedical device for assessing intravascular blood volume and technique for using the same
US823899412 Jun 20097 Aug 2012Nellcor Puritan Bennett LlcAdjusting parameters used in pulse oximetry analysis
US825727425 Sep 20084 Sep 2012Nellcor Puritan Bennett LlcMedical sensor and technique for using the same
US82657249 Mar 200711 Sep 2012Nellcor Puritan Bennett LlcCancellation of light shunting
US827555318 Feb 200925 Sep 2012Nellcor Puritan Bennett LlcSystem and method for evaluating physiological parameter data
US829280927 Mar 200923 Oct 2012Nellcor Puritan Bennett LlcDetecting chemical components from spectroscopic observations
US831568414 Jul 200820 Nov 2012Covidien LpOximeter ambient light cancellation
US836422025 Sep 200829 Jan 2013Covidien LpMedical sensor and technique for using the same
US836422121 Nov 200829 Jan 2013Covidien LpPatient monitoring alarm escalation system and method
US836422431 Mar 200929 Jan 2013Covidien LpSystem and method for facilitating sensor and monitor communication
US837695529 Sep 200919 Feb 2013Covidien LpSpectroscopic method and system for assessing tissue temperature
US838027115 Jun 200619 Feb 2013Covidien LpSystem and method for generating customizable audible beep tones and alarms
US838600030 Sep 200826 Feb 2013Covidien LpSystem and method for photon density wave pulse oximetry and pulse hemometry
US839194331 Mar 20105 Mar 2013Covidien LpMulti-wavelength photon density wave system using an optical switch
US840160616 Oct 200619 Mar 2013Covidien LpNuisance alarm reductions in a physiological monitor
US840160731 Mar 200819 Mar 2013Covidien LpNuisance alarm reductions in a physiological monitor
US840160830 Sep 200919 Mar 2013Covidien LpMethod of analyzing photon density waves in a medical monitor
US841229728 Jul 20062 Apr 2013Covidien LpForehead sensor placement
US841730930 Sep 20089 Apr 2013Covidien LpMedical sensor
US842310920 Jun 200816 Apr 2013Covidien LpMethod for enhancing pulse oximery calculations in the presence of correlated artifacts
US843338230 Jul 200930 Apr 2013Covidien LpTransmission mode photon density wave system and method
US843782227 Mar 20097 May 2013Covidien LpSystem and method for estimating blood analyte concentration
US845236726 Jul 201028 May 2013Covidien LpForehead sensor placement
US849460421 Sep 200923 Jul 2013Covidien LpWavelength-division multiplexing in a multi-wavelength photon density wave system
US849460619 Aug 200923 Jul 2013Covidien LpPhotoplethysmography with controlled application of sensor pressure
US849478630 Jul 200923 Jul 2013Covidien LpExponential sampling of red and infrared signals
US849868330 Apr 201030 Jul 2013Covidien LLPMethod for respiration rate and blood pressure alarm management
US850986915 May 200913 Aug 2013Covidien LpMethod and apparatus for detecting and analyzing variations in a physiologic parameter
US851551129 Sep 200920 Aug 2013Covidien LpSensor with an optical coupling material to improve plethysmographic measurements and method of using the same
US851551511 Mar 201020 Aug 2013Covidien LpMedical sensor with compressible light barrier and technique for using the same
US853850020 Oct 201117 Sep 2013Covidien LpSystem and method for probability based determination of estimated oxygen saturation
US856003628 Dec 201015 Oct 2013Covidien LpSelection of ensemble averaging weights for a pulse oximeter based on signal quality metrics
US857162124 Jun 201029 Oct 2013Covidien LpMinimax filtering for pulse oximetry
US861076928 Feb 201117 Dec 2013Covidien LpMedical monitor data collection system and method
US86119778 Mar 200417 Dec 2013Covidien LpMethod and apparatus for optical detection of mixed venous and arterial blood pulsation in tissue
US862291630 Oct 20097 Jan 2014Covidien LpSystem and method for facilitating observation of monitored physiologic data
US866646713 Jun 20124 Mar 2014Lawrence A. LynnSystem and method for SPO2 instability detection and quantification
US869659327 Sep 200615 Apr 2014Covidien LpMethod and system for monitoring intracranial pressure
US870260616 May 200822 Apr 2014Covidien LpPatient monitoring help video system and method
US870466621 Sep 200922 Apr 2014Covidien LpMedical device interface customization systems and methods
US87280017 Jan 201020 May 2014Lawrence A. LynnNasal capnographic pressure monitoring system
US872805929 Sep 200620 May 2014Covidien LpSystem and method for assuring validity of monitoring parameter in combination with a therapeutic device
US874454321 May 20103 Jun 2014Covidien LpSystem and method for removing artifacts from waveforms
US875095318 Feb 200910 Jun 2014Covidien LpMethods and systems for alerting practitioners to physiological conditions
US878154811 Mar 201015 Jul 2014Covidien LpMedical sensor with flexible components and technique for using the same
US87817536 Sep 201215 Jul 2014Covidien LpSystem and method for evaluating physiological parameter data
US878800121 Sep 200922 Jul 2014Covidien LpTime-division multiplexing in a multi-wavelength photon density wave system
US879870413 Sep 20105 Aug 2014Covidien LpPhotoacoustic spectroscopy method and system to discern sepsis from shock
US88016227 Mar 201112 Aug 2014Covidien LpSystem and method for pulse rate calculation using a scheme for alternate weighting
US881847528 Mar 201326 Aug 2014Covidien LpMethod for enhancing pulse oximetry calculations in the presence of correlated artifacts
US883819614 Mar 201316 Sep 2014Covidien LpNuisance alarm reductions in a physiological monitor
US885574916 Aug 20107 Oct 2014Covidien LpDetermination of a physiological parameter
US886219430 Jun 200814 Oct 2014Covidien LpMethod for improved oxygen saturation estimation in the presence of noise
US88621966 May 201114 Oct 2014Lawrence A. LynnSystem and method for automatic detection of a plurality of SP02 time series pattern types
US887418129 Oct 201228 Oct 2014Covidien LpOximeter ambient light cancellation
US892394513 Sep 201030 Dec 2014Covidien LpDetermination of a physiological parameter
US893014528 Jul 20106 Jan 2015Covidien LpLight focusing continuous wave photoacoustic spectroscopy and its applications to patient monitoring
US893222710 Feb 200613 Jan 2015Lawrence A. LynnSystem and method for CO2 and oximetry integration
US896819330 Sep 20083 Mar 2015Covidien LpSystem and method for enabling a research mode on physiological monitors
US898380011 Oct 200517 Mar 2015Covidien LpSelection of preset filter parameters based on signal quality
US90317935 Sep 201212 May 2015Lawrence A. LynnCentralized hospital monitoring system for automatically detecting upper airway instability and for preventing and aborting adverse drug reactions
US904295210 Feb 200626 May 2015Lawrence A. LynnSystem and method for automatic detection of a plurality of SPO2 time series pattern types
US90532227 May 20099 Jun 2015Lawrence A. LynnPatient safety processor
US93516744 Aug 201431 May 2016Covidien LpMethod for enhancing pulse oximetry calculations in the presence of correlated artifacts
US93809698 Jul 20135 Jul 2016Covidien LpSystems and methods for varying a sampling rate of a signal
US938098228 Jul 20105 Jul 2016Covidien LpAdaptive alarm system and method
US946837816 Nov 200518 Oct 2016Lawrence A. LynnAirway instability detection system and method
US20040221370 *13 Feb 200411 Nov 2004Nellcor Puritan Bennett IncorporatedHeadband with tension indicator
US20050197579 *8 Mar 20048 Sep 2005Nellcor Puritan Bennett IncorporatedMethod and apparatus for optical detection of mixed venous and arterial blood pulsation in tissue
US20060030764 *30 Sep 20059 Feb 2006Mallinckrodt Inc.Method and circuit for indicating quality and accuracy of physiological measurements
US20060135860 *2 Dec 200522 Jun 2006Baker Clark R JrSignal quality metrics design for qualifying data for a physiological monitor
US20060195028 *21 Feb 200631 Aug 2006Don HannulaHat-based oximeter sensor
US20060195041 *7 Mar 200631 Aug 2006Lynn Lawrence ACentralized hospital monitoring system for automatically detecting upper airway instability and for preventing and aborting adverse drug reactions
US20060264722 *26 Jul 200623 Nov 2006Don HannulaHat-based oximeter sensor
US20060264724 *26 Jul 200623 Nov 2006Don HannulaHat-based oximeter sensor
US20060264725 *26 Jul 200623 Nov 2006Don HannulaHat-based oximeter sensor
US20070032714 *16 Oct 20068 Feb 2007Nellcor Puritan Bennett Inc.Nuisance alarm reductions in a physiological monitor
US20070073124 *29 Sep 200529 Mar 2007Li LiSystem and method for removing artifacts from waveforms
US20070093721 *10 May 200626 Apr 2007Lynn Lawrence AMicroprocessor system for the analysis of physiologic and financial datasets
US20070106137 *15 Sep 200610 May 2007Baker Clark R JrPulse oximetry signal correction using near infrared absorption by water
US20070129647 *10 Feb 20067 Jun 2007Lynn Lawrence ASystem and method for CO2 and oximetry integration
US20080009690 *18 Sep 200710 Jan 2008Nellcor Puritan Bennett LlcPulse oximetry motion artifact rejection using near infrared absorption by water
US20080076977 *26 Sep 200627 Mar 2008Nellcor Puritan Bennett Inc.Patient monitoring device snapshot feature system and method
US20080076986 *20 Sep 200627 Mar 2008Nellcor Puritan Bennett Inc.System and method for probability based determination of estimated oxygen saturation
US20080081956 *29 Sep 20063 Apr 2008Jayesh ShahSystem and method for integrating voice with a medical device
US20080081970 *29 Sep 20063 Apr 2008Nellcor Puritan Bennett IncorporatedPulse oximetry sensor switchover
US20080081974 *29 Sep 20063 Apr 2008Nellcor Puritan Bennett IncorporatedPathological condition detector using kernel methods and oximeters
US20080082338 *29 Sep 20063 Apr 2008O'neil Michael PSystems and methods for secure voice identification and medical device interface
US20080082339 *29 Sep 20063 Apr 2008Nellcor Puritan Bennett IncorporatedSystem and method for secure voice identification in a medical device
US20080097175 *29 Sep 200624 Apr 2008Boyce Robin SSystem and method for display control of patient monitor
US20080114211 *29 Sep 200615 May 2008Edward KarstSystem and method for assuring validity of monitoring parameter in combination with a therapeutic device
US20080114226 *29 Sep 200615 May 2008Doug MusicSystems and methods for user interface and identification in a medical device
US20080189783 *29 Sep 20067 Aug 2008Doug MusicUser interface and identification in a medical device system and method
US20080200775 *20 Feb 200721 Aug 2008Lynn Lawrence AManeuver-based plethysmographic pulse variation detection system and method
US20080200819 *20 Feb 200721 Aug 2008Lynn Lawrence AOrthostasis detection system and method
US20080214906 *16 May 20084 Sep 2008Nellcor Puritan Bennett LlcPatient Monitoring Help Video System and Method
US20080221426 *9 Mar 200711 Sep 2008Nellcor Puritan Bennett LlcMethods and apparatus for detecting misapplied optical sensors
US20080221427 *9 Mar 200711 Sep 2008Nellcor Puritan Bennett LlcCancellation of light shunting
US20080255436 *20 Jun 200816 Oct 2008Nellcor Puritain Bennett IncorporatedMethod for Enhancing Pulse Oximery Calculations in the Presence of Correlated Artifacts
US20090005662 *14 Jul 20081 Jan 2009Nellcor Puritan Bennett IncOximeter Ambient Light Cancellation
US20090080007 *22 Sep 200826 Mar 2009Brother Kogyo Kabushiki KaishaPrinting device and method therefor
US20090082651 *3 Dec 200826 Mar 2009Nellcor Puritan Bennett LlcSelection of ensemble averaging weights for a pulse oximeter based on signal quality metrics
US20090154573 *13 Dec 200718 Jun 2009Nellcor Puritan Bennett LlcSignal Demodulation
US20090171166 *22 Dec 20082 Jul 2009Nellcor Puritan Bennett LlcOximeter with location awareness
US20090171167 *23 Dec 20082 Jul 2009Nellcor Puritan Bennett LlcSystem And Method For Monitor Alarm Management
US20090171172 *19 Dec 20082 Jul 2009Nellcor Puritan Bennett LlcMethod and system for pulse gating
US20090171173 *22 Dec 20082 Jul 2009Nellcor Puritan Bennett LlcSystem and method for reducing motion artifacts in a sensor
US20090171174 *22 Dec 20082 Jul 2009Nellcor Puritan Bennett LlcSystem and method for maintaining battery life
US20090171226 *22 Dec 20082 Jul 2009Nellcor Puritan Bennett LlcSystem and method for evaluating variation in the timing of physiological events
US20090209839 *18 Feb 200920 Aug 2009Nellcor Puritan Bennett LlcMethods And Systems For Alerting Practitioners To Physiological Conditions
US20090210163 *18 Feb 200920 Aug 2009Nellcor Puritan Bennett LlcSystem And Method For Evaluating Physiological Parameter Data
US20090247083 *27 Mar 20091 Oct 2009Nellcor Puritan Bennett LlcWavelength Selection And Outlier Detection In Reduced Rank Linear Models
US20090247845 *27 Mar 20091 Oct 2009Nellcor Puritan Bennett LlcSystem And Method For Estimating Blood Analyte Concentration
US20090247850 *27 Mar 20091 Oct 2009Nellcor Puritan Bennett LlcManually Powered Oximeter
US20090247851 *24 Mar 20091 Oct 2009Nellcor Puritan Bennett LlcGraphical User Interface For Monitor Alarm Management
US20090247852 *31 Mar 20091 Oct 2009Nellcor Puritan Bennett LlcSystem and method for facilitating sensor and monitor communication
US20090247854 *27 Mar 20091 Oct 2009Nellcor Puritan Bennett LlcRetractable Sensor Cable For A Pulse Oximeter
US20090248320 *27 Mar 20091 Oct 2009Nellcor Puritan Benett LlcSystem And Method For Unmixing Spectroscopic Observations With Nonnegative Matrix Factorization
US20090253971 *12 Jun 20098 Oct 2009Nellcor Puritan Bennett LlcAdjusting parameters used in pulse oximetry analysis
US20090281838 *7 May 200912 Nov 2009Lawrence A. LynnMedical failure pattern search engine
US20090326335 *30 Jun 200831 Dec 2009Baker Clark RPulse Oximeter With Wait-Time Indication
US20090327515 *30 Jun 200831 Dec 2009Thomas PriceMedical Monitor With Network Connectivity
US20100076319 *25 Sep 200825 Mar 2010Nellcor Puritan Bennett LlcPathlength-Corrected Medical Spectroscopy
US20100076337 *25 Sep 200825 Mar 2010Nellcor Puritan Bennett LlcMedical Sensor And Technique For Using The Same
US20100079292 *2 Dec 20091 Apr 2010Lawrence A. LynnMicroprocessor system for the analysis of physiologic and financial datasets
US20100081890 *30 Sep 20081 Apr 2010Nellcor Puritan Bennett LlcSystem And Method For Enabling A Research Mode On Physiological Monitors
US20100081897 *30 Jul 20091 Apr 2010Nellcor Puritan Bennett LlcTransmission Mode Photon Density Wave System And Method
US20100081899 *30 Sep 20081 Apr 2010Nellcor Puritan Bennett LlcSystem and Method for Photon Density Wave Pulse Oximetry and Pulse Hemometry
US20100113908 *30 Oct 20096 May 2010Nellcor Puritan Bennett LlcSystem And Method For Facilitating Observation Of Monitored Physiologic Data
US20100113909 *30 Oct 20096 May 2010Nellcor Puritan Bennett LlcSystem And Method For Facilitating Observation Of Monitored Physiologic Data
US20100141391 *16 Feb 201010 Jun 2010Nellcor Puritan Bennett LlcUser interface and identification in a medical device system and method
US20100174161 *7 Jan 20108 Jul 2010Lynn Lawrence ASystem and method for the detection of physiologic response to stimulation
US20100234705 *10 May 201016 Sep 2010Lynn Lawrence ASystem and Method for Automatic Detection of a Plurality of SP02 Time Series Pattern Types
US20100240972 *20 Mar 200923 Sep 2010Nellcor Puritan Bennett LlcSlider Spot Check Pulse Oximeter
US20110009723 *26 Jul 201013 Jan 2011Nellcor Puritan Bennett LlcForehead sensor placement
US20110029865 *31 Jul 20093 Feb 2011Nellcor Puritan Bennett LlcControl Interface For A Medical Monitor
US20110071366 *13 Sep 201024 Mar 2011Nellcor Puritan Bennett LlcDetermination Of A Physiological Parameter
US20110071368 *21 Sep 200924 Mar 2011Nellcor Puritan Bennett LlcMedical Device Interface Customization Systems And Methods
US20110071371 *21 Sep 200924 Mar 2011Nellcor Puritan Bennett LlcWavelength-Division Multiplexing In A Multi-Wavelength Photon Density Wave System
US20110071373 *21 Sep 200924 Mar 2011Nellcor Puritan Bennett LlcTime-Division Multiplexing In A Multi-Wavelength Photon Density Wave System
US20110071376 *16 Aug 201024 Mar 2011Nellcor Puritan Bennett LlcDetermination Of A Physiological Parameter
US20110071598 *13 Sep 201024 Mar 2011Nellcor Puritan Bennett LlcPhotoacoustic Spectroscopy Method And System To Discern Sepsis From Shock
US20110074342 *30 Sep 200931 Mar 2011Nellcor Puritan Bennett LlcWireless electricity for electronic devices
US20110077470 *30 Sep 200931 Mar 2011Nellcor Puritan Bennett LlcPatient Monitor Symmetry Control
US20110077485 *30 Sep 200931 Mar 2011Nellcor Puritan Bennett LlcMethod Of Analyzing Photon Density Waves In A Medical Monitor
US20110077547 *29 Sep 200931 Mar 2011Nellcor Puritan Bennett LlcSpectroscopic Method And System For Assessing Tissue Temperature
US20110092785 *28 Dec 201021 Apr 2011Nellcor Puritan Bennett LlcSelection of Ensemble Averaging Weights for a Pulse Oximeter Based on Signal Quality Metrics
US20110098544 *30 Dec 201028 Apr 2011Nellcor Puritan Bennett LlcSystem and method for integrating voice with a medical device
USD62656130 Jun 20082 Nov 2010Nellcor Puritan Bennett LlcCircular satseconds indicator and triangular saturation pattern detection indicator for a patient monitor display panel
USD62656230 Jun 20082 Nov 2010Nellcor Puritan Bennett LlcTriangular saturation pattern detection indicator for a patient monitor display panel
USD7362508 Oct 201011 Aug 2015Covidien LpPortion of a display panel with an indicator icon
CN104068865A *24 Apr 20141 Oct 2014辛勤Oxyhemoglobin saturation measuring method and portable device
Classifications
U.S. Classification600/38
International ClassificationA61F5/41, G01J9/04, G01N21/31, G01N21/64, G01N21/49, G01N21/47, A61B5/00
Cooperative ClassificationG01N21/49, G01N2021/1789, A61F5/41, G01N21/47, G01N21/4795, G01N2201/0696, G01N2201/06113, A61B5/14551, G01N2021/1791, G01N21/3151, A61B5/14553, A61F2005/411, A61B2562/0233, A61B2562/0242, G01N2021/3181, G01J9/04, A61B2562/043
European ClassificationA61B5/1455N4, A61B5/1455N, G01N21/47S, A61F5/41, G01N21/31D4, G01N21/49