Abstract: A blood leak detector is disclosed having a light source projecting a beam along an optical path, wherein the beam has a wavelength in a range of about 800 nm to 930 nm; a light detector receiving the beam; a housing with a slot to receive a transparent tube between the light source and light detector and aligned with the optical path.

Abstract: Pulse oximetry is improved through classification of plethysmographic signals by processing the plethysmographic signals using a neural network that receives input coefficients from multiple signal domains including, for example, spectral, bispectral, cepstral and Wavelet filtered signal domains. In one embodiment, a plethysmographic signal obtained from a patient is transformed (240) from a first domain to a plurality of different signal domains (242, 243, 244, 245) to obtain a corresponding plurality of transformed plethysmographic signals. A plurality of sets of coefficients derived from the transformed plethysmographic signals are selected and directed to an input layer (251) of a neural network (250). The plethysmographic signal is classified by an output layer (253) of the neural network (250) that is connected to the input layer (251) by one or more hidden layers (252).

Abstract: There is a need for a technique to compensate for, or eliminate, motion-induced artifacts in patient-attached critical care monitoring instruments. Consequently, the invention is directed to improving pulse-oximetry by incorporating additional signals to aid in the triggering of the pulse-oximeter or in analyzing the data received by the pulse oximeter. This includes detecting when the patient moves and analyzing the pulse-oximetry data in light of the detected movement.

Abstract: A pulse oximetry method and system for improved motion correction is disclosed. The method/system provides for the use of a detector output signal to obtain a different plurality of differential absorption data sets in corresponding relation to each of a succession of measurement, wherein each of the data sets includes differential absorption values for light of a first wavelength and light of a second wavelength. The data sets are processed to obtain a relative motion estimate value for each measurement. When the relative motion estimate value for a given measurement falls within a predetermined range (i.e., corresponding with clinical motion), a corresponding blood analyte indicator value is adjusted in a predetermined manner, wherein the corresponding adjusted blood analyte indicator is employable to obtain at least one blood analyte concentration value. In one embodiment, blood analyte indicator values may be readily multiplied by a predetermined adjustment factor (i.e.

Abstract: In a pulse oximeter (blood component measurement apparatus), a subject body is irradiated periodically with red light and infrared light. Then, carried out sequentially in a time sharing manner are the measurement of the transmitted light intensity through the subject body, the measurement of the pulse wave component of the transmitted light intensity, and the measurement of the dark level in the state that the subject body is not irradiated with the light. On the basis of these measurement values, oxygen saturation of the arterial blood is measured. In the present embodiments, each measurement is carried out with a time interval equal to the period corresponding to the line frequency. In this approach, periodic noise of the line frequency or other noise are eliminated in dark level correction. This permits precise measurement of the blood component.

Abstract: A signal processor which acquires a first signal, including a first desired signal portion and a first undesired signal portion, and a second signal, including a second desired signal portion and a second undesired signal portion, wherein the first and second desired signal portions are correlated. The signals may be acquired by propagating energy through a medium and measuring an attenuated signal after transmission or reflection. Alternatively, the signals may be acquired by measuring energy generated by the medium. A processor of the present invention generates a noise reference signal that is a combination of the undesired signal portions and is correlated to both the first and second undesired signal portions. The noise reference signal is then used to remove the undesired portion of each of the first and second measured signals.

Abstract: A signal processor which acquires a first signal, including a first primary signal portion and a first secondary signal portion, and a second signal, including a second primary signal portion and a second secondary signal portion, wherein the first and second primary signal portions are correlated. The signals may be acquired by propagating energy through a medium and measuring an attenuated signal after transmission or reflection. Alternatively, the signals may be acquired by measuring energy generated by the medium. A processor of the present invention generates a primary or secondary reference signal which is a combination, respectively, of only the primary or secondary signal portions. The secondary reference signal is then used to remove the secondary portion of each of the first and second measured signals via a correlation canceler, such as an adaptive noise canceler, preferably of the joint process estimator type.

Abstract: An intelligent, rule-based processor provides recognition of individual pulses in a pulse oximeter-derived photo-plethysmograph waveform. Pulse recognition occurs in two stages. The first stage identifies candidate pulses in the plethysmograph waveform. The candidate pulse stage identifies points in the waveform representing peaks and valleys corresponding to an idealized triangular wave model of the waveform pulses. At this stage, waveform features that do not correspond to this model are removed, including the characteristic dicrotic notch. The second stage applies a plethysmograph model to the candidate pulses and decides which pulses satisfies this model. This is done by first calculating certain pulse features and then applying different checks to identify physiologically acceptable features.

Abstract: A method for removing motion artifacts from devices for sensing bodily parameters and apparatus and system for effecting same. The method includes analyzing segments of measured data representing bodily parameters and possibly noise from motion artifacts. Each segment of measured data may correspond to a single light signal transmitted and detected after transmission or reflection through bodily tissue. Each data segment is frequency analyzed to determine up to three candidate peaks for further analysis. Each of the up to three candidate frequencies may be filtered and various parameters associated with each of the up to three candidate frequencies are calculated. The best frequency, if one exists, is determined by arbitrating the candidate frequencies using the calculated parameters according to predefined criteria. If a best frequency is found, a pulse rate and SpO2 may be output. If a best frequency is not found, other, conventional techniques for calculating pulse rate and SpO2 may be used.

Abstract: A signal processor which acquires a first signal, including a first desired signal portion and a first undesired signal portion, and a second signal, including a second desired signal portion and a second undesired signal portion, wherein the first and second desired signal portions are correlated. The signals may be acquired by propagating energy through a medium and measuring an attenuated signal after transmission or reflection. Alternatively, the signals may be acquired by measuring energy generated by the medium. A processor of the present invention generates a noise reference signal that is a combination of the undesired signal portions and is correlated to both the first and second undesired signal portions. The noise reference signal is then used to remove the undesired portion of each of the first and second measured signals.

Abstract: A method and an apparatus to analyze two measured signals that are modeled as containing desired and undesired portions such as noise, FM and AM modulation. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, a transformation is used to evaluate a ratio of the two measured signals in order to find appropriate coefficients. The measured signals are then fed into a signal scrubber which uses the coefficients to remove the unwanted portions. The signal scrubbing is performed in either the time domain or in the frequency domain. The method and apparatus are particularly advantageous to blood oximetry and pulserate measurements. In another embodiment, an estimate of the pulserate is obtained by applying a set of rules to a spectral transform of the scrubbed signal. In another embodiment, an estimate of the pulserate is obtained by transforming the scrubbed signal from a first spectral domain into a second spectral domain.

Abstract: The present invention involves method and apparatus for analyzing measured signals that are modeled as containing primary and secondary portions. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, the present invention involves utilizing a transformation which evaluates a plurality of possible signal coefficients in order to find appropriate coefficients. Alternatively, the present invention involves using statistical functions or Fourier transform and windowing techniques to determine the coefficients relating to two measured signals. Use of this invention is described in particular detail with respect to blood oximetry measurements.

Abstract: A sensor for use in an optical measurement device and a method for non-invasive measurement of a blood parameter. The sensor includes sensor housing, a source of radiation coupled to the housing, and a detector assembly coupled to the housing. The source of radiation is adapted to emit radiation at predetermined frequencies. The detector assembly is adapted to detect reflected radiation at least one predetermined frequency and to generate respective signals. The signals are used to determine the parameter of the blood.

Abstract: A pulse oximeter adaptively samples an input signal from a sensor in order to reduce power consumption in the absence of overriding conditions. Various sampling mechanisms may be used individually or in combination, including reducing the duty cycle of a drive current to a sensor emitter, intermittently powering-down a front-end interface to a sensor detector, or increasing the time shift between processed data blocks. Both internal parameters and output parameters may be monitored to trigger or override a reduced power consumption state. In this manner, a pulse oximeter can lower power consumption without sacrificing performance during, for example, high noise conditions or oxygen desaturations.

Abstract: A method and apparatus for reducing the effects of noise on a system for measuring physiological parameters, such as, for example, a pulse oximeter. The method and apparatus of the invention take into account the physical limitations on various physiological parameters being monitored when weighting and averaging a series of measurements. Varying weights are assigned different measurements, measurements are rejected, and the averaging period is adjusted according to the reliability of the measurements. Similarly, calculated values derived from analyzing the measurements are also assigned varying weights and averaged over adjustable periods. More specifically, a general class of filters such as, for example, Kalman filters, is employed in processing the measurements and calculated values. The filters use mathematical models which describe how the physiological parameters change in time, and how these parameters relate to measurement in a noisy environment.

Abstract: A processor provides signal quality based limits to a signal strength operating region of a pulse oximeter. These limits are superimposed on the typical gain dependent signal strength limits. If a sensor signal appears physiologically generated, the pulse oximeter is allowed to operate with minimal signal strength, maximizing low perfusion performance. If a sensor signal is potentially due to a signal induced by a dislodged sensor, signal strength requirements are raised. Thus, signal quality limitations enhance probe off detection without significantly impacting low perfusion performance. One signal quality measure used is pulse rate density, which defines the percentage of time physiologically acceptable pulses are occurring. If the detected signal contains a significant percentage of unacceptable pulses, the minimum required signal strength is raised proportionately.

Abstract: A method and an apparatus measure blood oxygenation in a subject. A first signal source applies a first input signal during a first time interval. A second signal source applies a second input signal during a second time interval. A detector detects a first parametric signal responsive to the first input signal passing through a portion of the subject having blood therein. The detector also detects a second parametric signal responsive to the second input signal passing through the portion of the subject. The detector generates a detector output signal responsive to the first and second parametric signals. A signal processor receives the detector output signal and demodulates the detector output signal by applying a first demodulation signal to a signal responsive to the detector output signal to generate a first output signal responsive to the first parametric signal.

Abstract: A method and a device for determining the quality of signal used for measuring a physiological parameter. One embodiment of the present invention is directed towards a pulse oximeter, where the measured physiological parameter includes a patient's pulse rate and blood oxygen saturation. The signal quality, which is indicative of the accuracy and reliability of the measured physiological parameter, is calculated by combining a plurality of signal quality indicators, each of which is an indicator of a quality of the measured signal. The value of the signal quality metric is compared to a threshold and based on this comparison various decisions are made by the medical device. One decision is directed towards deciding whether or not to display the measured physiological parameter, to ensure that only accurate measured values are displayed. Another decision is directed towards providing feedback to guide the clinician to adjust the location of the sensor to a more suitable tissue location.

Abstract: There is a need for a technique to compensate for, or eliminate, motion-induced artifacts in patient-attached critical care monitoring instruments. Also, a need exists to extend the accurate operational range of patient-attached pulse oximeters in environments when the patient's blood oxygen saturation is well below the normal physiologic range, or where there is low blood flow. Accordingly, the invention is directed to improving pulse-oximetry by incorporating additional signals to aid in the triggering of the pulse-oximeter or in analyzing the data received by the pulse oximeter. These approaches include measuring a pulsatile characteristic of the patient at a position close to, or at the pulse-oximetry measurement site, or using pulsatile characteristics that result from contraction of the patient's heart.

Abstract: A pulse oximeter sensor having an emitter(s) and a detector, with a layer having a first portion of the emitter and a second portion of layer over the detector is provided. A barrier is included between the first and second portions of the overlying layer to substantially block radiation of the wavelengths emitted by the emitter(s). Preferably, the barrier reduces the radiation shunted to less than 10% of the radiation detected, and more preferably to less than 1% of the radiation detected.

Abstract: A data confidence indicator includes a plurality of physiological data and a plurality of signal quality measures derived from a physiological sensor output, and a plurality of comparator outputs each responsive to one of the measures and a corresponding one of a plurality of thresholds. An alert trigger output combines the comparator outputs. A low signal quality warning is generated in response to the alert trigger output, wherein the thresholds are set so that the warning occurs during a time period when there is low confidence in the data. The alert may be in the form of a message generated on the pulse oximeter display to warn that the accuracy of saturation and pulse rate measurements may be compromised. A confidence-based alarm utilizes signal quality measures to reduce the probability of false alarms when data confidence is low and to reduce the probability of missed events when data confidence is high.

Abstract: A monitor has a primary input responsive to a first property of a tissue site. An uncompensated measurement is determinable from the primary input. A parameter input is responsive to a second property associated with the tissue site, where the first property is dependent upon the second property. The monitor also has a compensation relationship of the primary input, the parameter input and a compensated measurement. A processor is configured to output a compensated measurement from the primary input and the parameter input utilizing the compensation relationship, where the compensated measurement more accurately represents the first property than the uncompensated measurement.

Abstract: A method and apparatus for photoplethysmographic measurements is disclosed. In this system light from a plurality of emitters is delivered to the tissue-under-test. A subset of one or more of the emitters is known to be quiet light sources with relatively stable output intensity levels and spectral contents. A second subset of one or more emitters is known to be relatively noisy light sources with output intensity levels that fluctuate over time. The use of noisy light sources may be necessary for the photoplethysmographic measurements due to favorable spectral output characteristics such as narrow spectral bandwidth or desirable center wavelengths for the measurement of the hemodynamic parameters or analytes of interest.

Abstract: An oversampling pulse oximeter includes an analog to digital converter with a sampling rate sufficient to take multiple samples per source cycle. In one embodiment, a pulse oximeter (100) includes two mor more light sources (102) driven by light source drives (104) in response to drive signals from a digital signal processing unit (116). The source drives (104) may drive the sources (102) to produce a frequency division multiplex signal. The optical signals transmitted by the light sources (102) are transmitted through a patient's appendage (103) and impinge on a detector (106). The detector (106) provides an analog current signal representative of the received optical signals. An amplifier circuit (110) converts the analog current signal to an analog voltage signal in addition to performing a number of other functions. The amplifier circuit (110) outputs an analog voltage signal which is representative of the optical signals from the sources (102).

Abstract: The present invention involves method and apparatus for analyzing two measured signals that are modeled as containing primary and secondary portions. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, the present invention involves utilizing a transformation which evaluates a plurality of possible signal coefficients in order to find appropriate coefficients. Alternatively, the present invention involves using statistical functions or Fourier transform and windowing techniques to determine the coefficients relating to two measured signals. Use of this invention is described in particular detail with respect to blood oximetry measurements.

Abstract: A pulse oximeter adaptively samples an input signal from a sensor in order to reduce power consumption in the absence of overriding conditions. Various sampling mechanisms may be used individually or in combination, including reducing the duty cycle of a drive current to a sensor emitter, intermittently powering-down a front-end interface to a sensor detector, or increasing the time shift between processed data blocks. Both internal parameters and output parameters may be monitored to trigger or override a reduced power consumption state. In this manner, a pulse oximeter can lower power consumption without sacrificing performance during, for example, high noise conditions or oxygen desaturations.

Abstract: An intelligent, rule-based processor provides a pulse indicator designating the occurrence of each pulse in a pulse oximeter-derived photo-plethysmograph waveform. When there is relatively no distortion corrupting the plethysmograph signal, the processor analyzes the shape of the pulses in the waveform to determine where in the waveform to generate the pulse indication. When distortion is present, looser waveform criteria are used to determine if pulses are present. If pulses are present, the pulse indication is based upon an averaged pulse rate. If no pulses are present, no indication occurs. The pulse indicator provides a trigger and amplitude output. The trigger output is used to initiate an audible tone “beep” or a visual pulse indication on a display, such as a vertical spike on a horizontal trace or a corresponding indication on a bar display. The amplitude output is used to indicate data integrity and corresponding confidence in the computed values of saturation and pulse rate.

Abstract: In one aspect, the invention is a method for processing pulse oxymetry data signals. The method includes recording pulse oxymetry data signals. The pulse oxymetry data signals have a plurality of oxymetry waveforms. The method also includes determining a correlation coefficient between sequential oxymetry waveforms and identifying a valid pulse oxymetry waveform.

Abstract: The invention relates to a method for suppressing the interferences in a measuring signal with a substantially periodic wanted signal. According to the method, first a transformation, preferably a wavelet transformation, of the measuring signal to a summation of aperiodic basic logic functions is carried out, wherein each element of the sum has a coefficient. Those coefficients that exceed a predetermined threshold value are characterized as interference coefficients that are presumably influenced by interferences and the interference coefficients are manipulated to suppress the interferences. The manipulated summation is then retransformed to an interference-suppressed measuring signal. An undisturbed base signal is shown as curve 300 (thin) and the disturbed signal as curve 310 (extra-bold). The curve 320 (bold) shows the signal screened according to the invention, by starting from curve 310 and carrying out the embodiment presented in the invention.

Abstract: An intelligent, rule-based processor provides signal quality based limits to the signal strength operating region of a pulse oximeter. These limits are superimposed on the typical gain dependent signal strength limits. If a sensor signal appears physiologically generated, the pulse oximeter is allowed to operate with minimal signal strength, maximizing low perfusion performance. If a sensor signal is potentially due to a signal induced by a dislodged sensor, signal strength requirements are raised. Thus, signal quality limitations enhance probe off detection without significantly impacting low perfusion performance. One signal quality measure used is pulse rate density, which defines the percentage of time physiologically acceptable pulses are occurring. If the detected signal contains a significant percentage of unacceptable pulses, the minimum required signal strength is raised proportionately.

Abstract: Processing of plethysmographic signals via the cepstral domain is provided. In one embodiment, a cepstral domain plethysmographic signal processing method (200) includes the steps of obtaining (210) time domain plethysmographic signals, smoothing (220) the time domain plethysmographic signals, performing (230) a first-stage Fourier transformation of the time domain plethysmographic signals to frequency domain plethysmographic signals, computing (240) power spectrums from the frequency domain plethysmographic signals, scaling (250) the power spectrums with a logarithmic function, performing (260) a second-stage Fourier transformation on log-scaled spectrums to transform the power spectrums into cepstrums, and examining (270) the cepstrums to obtain information therefrom relating to a physiological condition of the patient such as the patient's pulse rate or SPO2 level.

Abstract: The present invention involves method and apparatus for analyzing two measured signals that are modeled as containing primary and secondary portions. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, the present invention involves utilizing a transformation which evaluates a plurality of possible signal coefficients in order to find appropriate coefficients. Alternatively, the present invention involves using statistical functions or Fourier transform and windowing techniques to determine the coefficients relating to two measured signals. Use of this invention is described in particular detail with respect to blood oximetry measurements.

Abstract: A signal processing method, preferably for extracting a fundamental period from a noisy, low-frequency signal, is disclosed. The signal processing method generally comprises calculating a numerical transform for a number of selected periods by multiplying signal data by discrete points of a sine and a cosine wave of varying period and summing the results. The period of the sine and cosine waves are preferably selected to have a period substantially equivalent to the period of interest when performing the transform.

Abstract: A method and an apparatus measure blood oxygenation in a subject. A first signal source applies a first input signal during a first time interval. A second signal source applies a second input signal during a second time interval. A detector detects a first parametric signal responsive to the first input signal passing through a portion of the subject having blood therein. The detector also detects a second parametric signal responsive to the second input signal passing through the portion of the subject. The detector generates a detector output signal responsive to the first and second parametric signals. A signal processor receives the detector output signal and demodulates the detector output signal by applying a first demodulation signal to a signal responsive to the detector output signal to generate a first output signal responsive to the first parametric signal.

Abstract: Recognition of a useful signal in a measurement signal by: transforming the measurement signal for a given time slot into the frequency range; identifying frequency peaks in the transformed measurement signal; assigning identified frequency peaks to temporal progressions of identified frequency peaks of one or more preceding time slots to the extent the identified frequency peaks are already present; assigning the temporal progressions to one or more families which are comprised of a fundamental wave and/or of one or more harmonic waves; selecting a family as that which should represent the useful signal, and; selecting a frequency peak of the current time slot from the selected family as that which should represent the measured value of the useful signal in this time slot. The signal filtering is preferably used for medical measurement signals, preferably in the area of pulsoximetry and for measuring blood pressure or determining the heart rate.

Abstract: A system is disclosed which first identifies a plurality of characteristics of a physiological signal any one of which may represent a physiological parameter. A plurality of different techniques are used to provide respective likelihood factors for each such identified characteristic. The resulting likelihood factors are then analyzed to select the one characteristic of the physiological signal which most likely represents the desired physiological parameter. The physiological parameter is then calculated from the selected characteristic of the physiological signal.

Abstract: A method for determining physiological characteristics comprising the steps of (a) acquiring a first blood oxygen signal from a subject, the blood oxygen signal having an undesirable artifact signal component; (b) acquiring an additional physiological signal having a heart rate component using an acquisition technique that is different and independent from the first acquiring step; (c) processing the first blood oxygen signal and the physiological signal to provide a first waveform having a reduced level of the artifact signal component therein; (d) processing the first waveform and the physiological signal to provide a reference waveform; and (e) processing the reference waveform and the physiological signal to provide a second blood oxygen saturation signal corresponding to the blood oxygen saturation level of said subject.

Abstract: A system for detecting a physiological parameter from a physiological signal, includes a source of the physiological signal. Circuitry, coupled to the signal source, detects spectral peaks in the physiological signal. Calculating circuitry, coupled to the spectral peak detecting circuitry, calculates a parameter value corresponding to each detected spectral peak. Weighting circuitry, coupled to the calculating circuitry and the spectral peak detecting circuit, assigns a weight to each peak according to a feature of a signal and the parameter value corresponding to that peak. Circuitry, coupled to the weighting circuitry, selects the peak according to a predetermined criterion. Output circuitry, coupled to the selecting circuitry and the calculating circuitry, then generates the parameter value corresponding to the selected peak.

Abstract: The present invention involves method and apparatus for analyzing two measured signals that are modeled as containing primary and secondary portions. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, the present invention involves utilizing a transformation which evaluates a plurality of possible signal coefficients in order to find appropriate coefficients. Alternatively, the present invention involves using statistical functions or Fourier transform and windowing techniques to determine the coefficients relating to two measured signals. Use of this invention is described in particular detail with respect to blood oximetry measurements.

Abstract: A method for removing motion artifacts from devices for sensing bodily parameters and apparatus and system for effecting same. The method includes analyzing segments of measured data representing bodily parameters and possibly noise from motion artifacts. Each segment of measured data may correspond to a single light signal transmitted and detected after transmission or reflection through bodily tissue. Each data segment is frequency analyzed to determine up to three candidate peaks for further analysis. Each of the up to three candidate frequencies may be filtered and various parameters associated with each of the up to three candidate frequencies are calculated. The best frequency, if one exists, is determined by arbitrating the candidate frequencies using the calculated parameters according to predefined criteria. If a best frequency is found, a pulse rate and SpO2 may be output. If a best frequency is not found, other, conventional techniques for calculating pulse rate and Spo2 may be used.

Abstract: Differential values, for use in blood oxygenation calculations, are determined based on multiple sample values for each channel of an oximetry system, each such value constituting a data point. In one implementation, each of these data points is defined by a sample window (220, 222 and 224), where the window includes, for example, 7-10 data points. That is, the data points within window (220, 222 or 224) are used to establish a differential value nominally associated with the data sample about which the window is centered. The differential value is calculated based on a mathematical model such as a weighted linear regression analysis. In this manner, output may be provided on a sample-by-sample basis while mitigating noise sensitivity.

Abstract: A signal processor which acquires a first signal, including a first desired signal portion and a first undesired signal portion, and a second signal, including a second desired signal portion and a second undesired signal portion, wherein the first and second desired signal portions are correlated. The signals may be acquired by propagating energy through a medium and measuring an attenuated signal after transmission or reflection. Alternatively, the signals may be acquired by measuring energy generated by the medium. A processor of the present invention generates a noise reference signal which is a combination of only the undesired signal portions and is correlated to both the first and second undesired signal portions. The noise reference signal is then used to remove the undesired portion of each of the first and second measured signals via an adaptive noise canceler, preferably of the joint process estimator type.

Abstract: An oversampling pulse oximeter includes an analog to digital converter with a sampling rate sufficient to take multiple samples per source cycle. In one embodiment, a pulse oximeter (100) includes two mor more light sources (102) driven by light source drives (104) in response to drive signals from a digital signal processing unit (116). The source drives (104) may drive the sources (102) to produce a frequency division multiplex signal. The optical signals transmitted by the light sources (102) are transmitted through a patient's appendage (103) and impinge on a detector (106). The detector (106) provides an analog current signal representative of the received optical signals. An amplifier circuit (110) converts the analog current signal to an analog voltage signal in addition to performing a number of other functions. The amplifier circuit (110) outputs an analog voltage signal which is representative of the optical signals from the sources (102).

Abstract: A method for determining the blood constituents of a patient comprising coupling an oximeter sensor arrangement to a tissue region of the patient; passing first and second lights through the patient's tissue region for a first period of time while the venous blood in the tissue region has a first volume and for a second period of time while the venous blood in the tissue region has a second volume, the first light being substantially in a red light range and the second light being substantially in an infrared light range; detecting a red light signal and an infrared light signal, the red and infrared signals having at least first and second frequencies; computing a first ratio of the red and infrared signals at the first frequency; computing a second ratio of the red and infrared signals at the second frequency; comparing the first and second ratios to determine a first blood constituent.

Abstract: An intelligent, rule-based processor provides recognition of individual pulses in a pulse oximeter-derived photo-plethysmograph waveform. Pulse recognition occurs in two stages. The first stage identifies candidate pulses in the plethysmograph waveform. The candidate pulse stage identifies points in the waveform representing peaks and valleys corresponding to an idealized triangular wave model of the waveform pulses. At this stage, waveform features that do not correspond to this model are removed, including the characteristic dicrotic notch. The second stage applies a plethysmograph model to the candidate pulses and decides which pulses satisfies this model. This is done by first calculating certain pulse features and then applying different checks to identify physiologically acceptable features.

Abstract: A red light and an infrared light which are emitted from a light emitting portion 2 are transmitted through a fingertip 4 of a subject and are converted into electric signals by a light receiving portion 3. The respective signals are separated and amplified and are then sent to a CPU 8. In the CPU 8, the input signals are divided into D.C. components DC1 and DC2 and A.C. components AC1 and AC2, changes &Dgr;A1=(AC/DC) 1 and &Dgr;A2=(AC/DC)2 in an absorbance are calculated, high frequency components thereof are extracted, a mutual ratio &PSgr; is calculated, and a noise removing waveform is calculated based thereon. Based on the noise removing waveform, a pulse wave is detected, a pulse rate is calculated, a display wave form is calculated and an oxygen saturation is calculated. These are displayed through a display unit 11.

Abstract: The present invention involves method and apparatus for analyzing two measured signals that are modeled as containing primary and secondary portions. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, the present invention involves utilizing a transformation which evaluates a plurality of possible signal coefficients in order to find appropriate coefficients. Alternatively, the present invention involves using statistical functions or Fourier transform and windowing techniques to determine the coefficients relating to two measured signals. Use of this invention is described in particular detail with respect to blood oximetry measurements.

Abstract: An improved pulse oximeter is disclosed. The pulse oximeter includes audio signal generation means, controlled by algorithms in a processing element which continuously transform the signals from the sensor into signal quality information. This information is converted into an audio signal and annunciated for the operator's use in guiding sensor placement. This signal quality information is available even in the absence of successful computation of pulse rate and/or oxygen saturation level. It furthermore can reflect signal quality changes that may be too subtle to be reflected in the typical numerical representation of pulse rate and oxygen saturation trend. The audio representation of the signal quality can further be modulated to convey other system and/or physiological status and alerts.

Abstract: The present invention involves method and apparatus for analyzing two measured signals that are modeled as containing primary and secondary portions. Coefficients relate the two signals according to a model defined in accordance with the present invention. In one embodiment, the present invention involves utilizing a transformation which evaluates a plurality of possible signal coefficients in order to find appropriate coefficients. Alternatively, the present invention involves using statistical functions or Fourier transform and windowing techniques to determine the coefficients relating to two measured signals. Use of this invention is described in particular detail with respect to blood oximetry measurements.

Abstract: A signal processor which acquires a first signal, including a first desired signal portion and a first undesired signal portion, and a second signal, including a second desired signal portion and a second undesired signal portion, wherein the first and second desired signal portions are correlated. The signals may be acquired by propagating energy through a medium and measuring an attenuated signal after transmission or reflection. Alternatively, the signals may be acquired by measuring energy generated by the medium. A processor generates a noise reference signal which is a combination of only the undesired signal portions and is correlated to both the first and second undesired signal portions. The noise reference signal is then used to remove the undesired portion of each of the first and second measured signals via an adaptive noise canceler, preferably of the joint process estimator type.