Abstract: An apparatus for estimating oxygen saturation is provided. The apparatus may include a sensor configured to measure optical signals of multiple wavelengths based on emitting multi-wavelength light onto an object; and a processor configured to: determine a section of the optical signals for estimating the oxygen saturation based on a difference between at least two optical signals among the optical signals of the multiple wavelengths; and estimate the oxygen saturation based on the optical signals of the multiple wavelengths in the section.

Abstract: A biometric information detecting apparatus includes a bio-signal measurer including a light-emitting unit and a light-receiving unit, the light-emitting unit configured to emit an optical signal and the light-receiving unit configured to detect the optical signal that is modulated by a target object; a low-frequency signal obtainer configured to obtain a low-frequency signal from the bio-signal measured by the bio-signal measurer; and a signal processor configured to analyze biometric information from the bio-signal in response to determining that the low-frequency signal obtained from the bio-signal is within a reference range.

Abstract: According to embodiments, techniques for using continuous wavelet transforms and spectral transforms to determine oxygen saturation from photoplethysmographic (PPG) signals are disclosed. According to embodiments, a first and a second PPG signals may be received. A spectral transform of the first and the second PPG signals may be performed to produce a first and a second spectral transformed signals. A frequency region associated with a pulse rate of the PPG signals may be identified from the first and the second spectral transformed signals. According to embodiments, a continuous wavelet transform of the first and the second PPG signals may be performed at a scale corresponding to the identified frequency region to produce a first and a second wavelet transformed signals. The oxygen saturation may be determined based at least in part upon the wavelet transformed signals.

Abstract: The invention provides a body-worn system that continuously measures pulse oximetry and blood pressure, along with motion, posture, and activity level, from an ambulatory patient. The system features an oximetry probe that comfortably clips to the base of the patient's thumb, thereby freeing up their fingers for conventional activities in a hospital, such as reading and eating. The probe secures to the thumb and measures time-dependent signals corresponding to LEDs operating near 660 and 905 nm. Analog versions of these signals pass through a low-profile cable to a wrist-worn transceiver that encloses a processing unit. Also within the wrist-worn transceiver is an accelerometer, a wireless system that sends information through a network to a remote receiver, e.g. a computer located in a central nursing station.

Abstract: A wearable computing device includes an electro-optical sensor to translate received light into an electrical signal. During a first mode of operation of the wearable computing device, a physical parameter of a wearer of the wearable computing device is assessed from the electrical signal. During a second mode of operation of the wearable computing device, encoded communication data is extracted from the electrical signal.

Abstract: A physiological parameter tracking system has a reference parameter calculator configured to provide a reference parameter responsive to a physiological signal input. A physiological measurement output is a physiological parameter derived from the physiological signal input during a favorable condition and an estimate of the physiological parameter according to the reference parameter during an unfavorable condition.

Abstract: The invention provides a body-worn system that continuously measures pulse oximetry and blood pressure, along with motion, posture, and activity level, from an ambulatory patient. The system features an oximetry probe that comfortably clips to the base of the patient's thumb, thereby freeing up their fingers for conventional activities in a hospital, such as reading and eating. The probe secures to the thumb and measures time-dependent signals corresponding to LEDs operating near 660 and 905 nm. Analog versions of these signals pass through a low-profile cable to a wrist-worn transceiver that encloses a processing unit. Also within the wrist-worn transceiver is an accelerometer, a wireless system that sends information through a network to a remote receiver, e.g. a computer located in a central nursing station.

Abstract: A method of performing measurement of a subject comprises measuring a physiological parameter of a subject, deriving data from the measured parameter, optionally, obtaining metadata relating to the measurement of the physiological parameter, determining the quality of the derived data from the derived data and/or the obtained metadata, and if the determined quality matches a predefined criteria, performing a predefined corrective action. In one embodiment, the method further comprises calculating one or more qualifiers from the derived data and/or from the obtained metadata, and wherein the step of determining the quality of the derived data comprises determining the quality of the derived data from the calculated qualifiers.

Abstract: The invention provides a body-worn system that continuously measures pulse oximetry and blood pressure, along with motion, posture, and activity level, from an ambulatory patient. The system features an oximetry probe that comfortably clips to the base of the patient's thumb, thereby freeing up their fingers for conventional activities in a hospital, such as reading and eating. The probe secures to the thumb and measures time-dependent signals corresponding to LEDs operating near 660 and 905 nm. Analog versions of these signals pass through a low-profile cable to a wrist-worn transceiver that encloses a processing unit. Also within the wrist-worn transceiver is an accelerometer, a wireless system that sends information through a network to a remote receiver, e.g. a computer located in a central nursing station.

Abstract: Improved tourniquet apparatus for measuring a patient's limb occlusion pressure includes an inflatable tourniquet cuff for encircling a limb at a location and to which a tourniquet instrument is releasably connectable.

Abstract: The present disclosure relates to monitoring a characteristic respiration rate of a patient based at least in part on a suitable time period that either precedes or follows a triggering event, such as a clinician/patient interaction, where the triggering event may negatively impact the physiological parameter. In some embodiments, physiological parameter values falling between one or more pre-set thresholds may be used to derive the characteristic physiological parameter. In some embodiments, monitoring the respiration rate may provide additional information about the patient's status. In some embodiments, confidence measures may be associated with, or may be used to analyze features of the patient signal to derive information about, the characteristic respiration rate. The patient signal used to derive a patient's respiration rate may be of an oscillatory nature or may include oscillatory features that may be analyzed to derive a characteristic respiration rate.

Abstract: The present disclosure relates to signal processing and, more particularly, to determining the value of a physiological parameter, such as the blood oxygen saturation (SpO2) of a subject. In an embodiment, a first baseline for a first waveform and a second baseline for a second waveform are determined. In this embodiment, the first and second waveforms are indicative of the physiological parameter of the subject. The first and second waveforms are filtered to obtain a first direct-current (DC) component for the first waveform and a second DC component for the second waveform. A measured value for the physiological parameter is derived from the first and second baseline signals, and the first and second DC components. In an embodiment, the measured value for the physiological parameter is determined based on a ratio of the normalized difference between the DC component and the baseline signal for the first waveform with respect to same for the second waveform.

Abstract: Apparatus for reducing an interference portion in a time-discrete signal further including a useful portion, including a first provider for providing the time-discrete signal including the interference portion and the useful portion; a second provider for providing a first time-discrete reference signal including a first interference portion, and a second time-discrete reference signal including a second interference portion, the second interference portion being shifted in phase relative to the first interference portion. The apparatus further includes a subtractor for generating a differential signal from the two reference signals, the differential signal including a frequency component caused by the first and second interference portions; and a manipulator for manipulating the time-discrete signal on the basis of the differential signal such that in a manipulated time-discrete signal the frequency component is reduced.

Abstract: Apparatus for automatically monitoring sleep, including a video recorder for recording live images of a subject sleeping, including a transmitter for transmitting the recorded images in real-time to a mobile device, and a computing device communicating with said transmitter, including a receiver for receiving the transmitted images in real-time, a processor for analyzing in real-time the received images and for automatically inferring in real-time information about the state of the subject, and a monitor for displaying in real-time the information inferred by said processor about the state of the subject. A method and a computer-readable storage medium are also described and claimed.

Abstract: The invention relates to a method for non-invasive determination of oxygen saturation of blood within a deep vascular structure of a human patient comprising locating on skin of the patient in a vicinity of the deep vascular structure of interest emitter and receiver elements of a light oximeter device, wherein optimal location of said elements is achieved through matching of a plethysmography trace obtained from the oximeter device to known plethysmography characteristics of the deep vascular structure of interest, and wherein oxygen saturation is determined from a ratio of light absorbed at different wavelengths by haemoglobin in the blood within the vascular structure of interest. The invention also relates to modified oximetry devices capable of carrying out the method.

Abstract: A method and monitor for monitoring vital signs. In one embodiment, the vital signs monitor includes a housing sized and shaped for fitting adjacent the ear of a wearer and an electronic module for measuring vital signs. The electronic module for measuring vital signs is located within the housing and includes a plurality of vital signs sensing modules in communication with a processor. The plurality of sensing modules includes at least two of the modules selected from the group of a ballistocardiographic (BCG) module, a photoplethysmographic (PPG) module, an accelerometer module, a temperature measurement module, and an electrocardiographic (ECG) module. In one embodiment, the processor calculates additional vital signs in response to signals from the plurality of vital signs sensing modules.

Abstract: Sensors and monitors for a physiological monitoring system having capability to indicate an accuracy of an estimated physiological condition. The sensor senses at least one physiological characteristic of a patient and is connectable to a monitor that estimates the physiological condition from signals detected by the sensor. The sensor includes a detector for detecting the signals from the patient which are indicative of the physiological characteristic. The sensor is associated with a memory configured to store data that defines at least one sensor signal specification boundary for the detected signals. The boundary is indicative of a quality of the signals and an accuracy of the physiological characteristic estimated from the signals by the monitor. The sensor further includes means for providing access to the memory to allow transmission of the data that defines the at least one sensor boundary to the monitor.

Abstract: The present disclosure describes a method and an apparatus for analyzing measured signals using various processing techniques. In certain embodiments, the measured signals are physiological signals. In certain embodiments, the measurements relate to blood constituent measurements including blood oxygen saturation.

Abstract: According to embodiments, techniques for extracting a signal parameter from a selected region of a generally repetitive signal are disclosed. A pulse oximetry system including a sensor or probe may be used to obtain an original photoplethysmograph (PPG) signal from a subject. A filter transformation may be applied to the original PPG signal to produce a baseline PPG signal. The baseline PPG signal may contain artifacts and/or noise, and a region of the baseline PPG signal suitable for extracting the signal parameter may be selected. A suitable region of the baseline PPG signal may be selected by applying one or more thresholds to the baseline PPG signal, where the values of the thresholds may be set based on derivative values, amplitude-based percentiles, and/or local minima and maxima of the baseline PPG signal. A portion of the original PPG signal corresponding to the selected region may be processed, and the signal parameter may be extracted from the processed region.

Abstract: A non-invasive device and a system for monitoring and measuring blood saturation and heart pulse rate of a baby or infant is provided. The device includes a housing unit configured to be integrated within apparatus, which is attachable proximate to a limb being measured. The housing unit includes at least one light source, providing light directed toward the surface of the limb, a light detector spaced apart from the light source and sensitive to intensity levels of the light reflected from the limb and a processing unit for processing the intensity signals received from the light detector for producing output signals. The device may determine the level of the blood constituent and may also use this level for monitoring and/or to activate an alarm when the level falls outside a predetermined range.

Abstract: According to embodiments, systems and methods for detecting the occurrence of events from a signal are provided. A signal processing system may analyze baseline changes and changes in signal characteristics to detect events from a signal. The system may also detect events by analyzing energy parameters and artifacts in a scalogram of the signal. Further, the system may detect events by analyzing both the signal and its corresponding scalogram.

Abstract: A method, system and device for measurement of a blood constituent level, including a light source, a light detector proximate an organ surface, adjustable gain amplifiers, and a processor/controller connected within a processing unit operative to separate AC and DC signal components. The device may determine the level of blood constituent, may use this level for monitoring and/or to activate an alarm when the level falls outside a predetermined range, may be applied to monitoring conditions of apnea, respiratory stress, and reduced blood flow in organ regions, heart rate, jaundice, and blood flow velocity, and may be incorporated within a monitoring system.

Abstract: A method, system and device for measurement of a blood constituent level, including a light source, a light detector proximate an organ surface, adjustable gain amplifiers, and a processor/controller connected within a processing unit operative to separate AC and DC signal components. The device may determine the level of blood constituent, may use this level for monitoring and/or to activate an alarm when the level falls outside a predetermined range, may be applied to monitoring conditions of apnea, respiratory stress, and reduced blood flow in organ regions, heart rate, jaundice, and blood flow velocity, and may be incorporated within a monitoring system.

Abstract: A method, system and device for measurement of a blood constituent level, including a light source, a light detector proximate an organ surface, adjustable gain amplifiers, and a processor/controller connected within a processing unit operative to separate AC and DC signal components. The device may determine the level of blood constituent, may use this level for monitoring and/or to activate an alarm when the level falls outside a predetermined range, may be applied to monitoring conditions of apnea, respiratory stress, and reduced blood flow in organ regions, heart rate, jaundice, and blood flow velocity, and may be incorporated within a monitoring system.

Abstract: A method, system and device for measurement of a blood constituent level, including a light source, a light detector proximate an organ surface, adjustable gain amplifiers, and a processor/controller connected within a processing unit operative to separate AC and DC signal components. The device may determine the level of blood constituent, may use this level for monitoring and/or to activate an alarm when the level falls outside a predetermined range, may be applied to monitoring conditions of apnea, respiratory stress, and reduced blood flow in organ regions, heart rate, jaundice, and blood flow velocity, and may be incorporated within a monitoring system.

Abstract: A method and system are presented for use in determining one or more parameters of a subject. A region of interest of the subject is irradiated with acoustic tagging radiation, which comprises at least one acoustic tagging beam. At least a portion of the region of interest is irradiated with at least one electromagnetic beam of a predetermined frequency range. Electromagnetic radiation response of the at least portion of the region of interest is detected and measured data indicative thereof is generated. The detected response comprises electromagnetic radiation tagged by the acoustic radiation. This enables processing of the measured data indicative of the detected electromagnetic radiation response to determine at least one parameter of the subject in a region corresponding to the locations in the medium at which the electromagnetic radiation has been tagged by the acoustic radiation, and outputting data indicative of the at least one determined parameter.

Abstract: Sensors and monitors for a physiological monitoring system having capability to indicate an accuracy of an estimated physiological condition. The sensor senses at least one physiological characteristic of a patient and is connectable to a monitor that estimates the physiological condition from signals detected by the sensor. The sensor includes a detector for detecting the signals from the patient which are indicative of the physiological characteristic. The sensor is associated with a memory configured to store data that defines at least one sensor signal specification boundary for the detected signals. The boundary is indicative of a quality of the signals and an accuracy of the physiological characteristic estimated from the signals by the monitor. The sensor further includes means for providing access to the memory to allow transmission of the data that defines the at least one sensor boundary to the monitor.

Abstract: A switched filter signal processing system includes an input terminal for receiving an input signal conveying first signal information in a first time phase and second signal information in a different second time phase. Desired information represents the difference between the first and second signal information. A multiplexed switch filter filters the input signal in the first phase with a first filter to obtain the first signal information and filters the input signal in the different second time phase with a second filter to obtain the second signal information. The system also includes a common filter component, which is shared by the first and second filter, and respective second filter components for the first and second filters.

Abstract: In an apparatus for determining a concentration of a light absorbing substance in blood, a plurality of photo emitters are adapted to emit light beams having different wavelengths toward a living tissue including a blood vessel. A photo receiver is adapted to receive the light beams which have been transmitted through or reflected from the living tissue. A driver inputs driving currents for causing the respective photo emitters to emit the light beams. An optimizer obtains values of AC components of the light beams received by the photo receiver, and adjusts values of the driving currents such that the values of the AC components fall within a predetermined range.

Abstract: An apparatus for measuring a concentration of a light-absorbing substance in blood is disclosed. A light emitter emits light beams to irradiate a living tissue, each of the light beams being associated with one wavelength which is absorbed by the blood. A first instrument measures first intensities of the light beams, which are to be incident on the living tissue. A second instrument measures second intensities of the light beams, which are transmitted through the living tissue. A first calculator calculates an attenuation variation ratio, which is a ratio of attenuation variations of the respective light beams due to variation of a volume of the blood caused by pulsation, based on the second intensities of the light beams. A second calculator calculates the concentration based on the first intensities, the second intensities, and the attenuation variation ratio.

Abstract: A method for use in operating a signal attenuation measurement device used to obtain a physiological parameter of a patient and an apparatus for use in determining at least one physiological parameter relating to a patient from at least first and second signals transmitted to a patient tissue site and attenuated thereby are provided. In accordance with the method and apparatus of the present invention, the first and second signals are multiplexed using frequency orthogonal code division multiplexed excitation waveforms. This allows for both relatively good source separation of the signals and whitening of external noise.

Abstract: A method, system and device for measurement of a blood constituent level, including a light source, a light detector proximate an organ surface, adjustable gain amplifiers, and a processor/controller connected within a processing unit operative to separate AC and DC signal components. The device may determine the level of blood constituent, may use this level for monitoring and/or to activate an alarm when the level falls outside a predetermined range, may be applied to monitoring conditions of apnea, respiratory stress, and reduced blood flow in organ regions, heart rate, jaundice, and blood flow velocity, and may be incorporated within a monitoring system.

Abstract: A method and a system for decomposition of a multiple channel signal reflecting characteristics of a blood perfused fleshy medium is provided. This technique can be utilized for determination of at least one desired blood parameter. According to the method a portion of the medium is illuminated by amplitude-modulated light of more than two different optic channels having wavelength in a range where the scattering properties of blood are sensitive to light radiation. Further, a light response of the medium sensed, and the multiple channel signal is generated. Thereafter, the multiple channel signal is analyzed that includes: filtering the multiple channel signal and separating at least a part of multiple channels from each other, and providing time evolutions of the light responses of the medium for the part of said multiple channels. According to the invention, the amplitude-modulated light is activated in a composite mode regime employing a combination of parallel and serial modes.

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 or 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 and apparatus extract a signal component of a measured signal using one of two methods. If the signal component in the measured signal is a periodic signal with a certain well-defined peak-to-peak intensity value, upper and lower envelopes of the measured signal are determined and analyzed to extract said signal component of the measured signal. This signal component can further be used to calculate a desired parameter of the sample. The DC component of the signal is determined as the median value of the upper envelope, and the AC component is determined as the median value of the difference between the upper and lower envelopes. If the signal component of the measured signal is a periodic signal characterized by a specific asymmetric shape, a specific adaptive filtering is applied to the measured signal, resulting in the enhancement of the signal component relative to a noise component.

Abstract: A variable indication estimator which determines an output value representative of a set of input data. For example, the estimator can reduce input data to estimates of a desired signal, select a time, and determine an output value from the estimates and the time. In one embodiment, the time is selected using one or more adjustable signal confidence parameters determine where along the estimates the output value will be computed. By varying the parameters, the characteristics of the output value are variable. For example, when input signal confidence is low, the parameters are adjusted so that the output value is a smoothed representation of the input signal. When input signal confidence is high, the parameters are adjusted so that the output value has a faster and more accurate response to the input signal.

Abstract: An optical measuring device includes a sensor which emits light flashes toward a subject of detection with a light emitting element which is supplied with electric power from a rechargeable battery for a certain duration at certain intervals and receives reflected light from the subject with a light sensitive element. A subtractor subtracts a d.c. component from a sensed signal provided by the light sensitive element, thereby extracting a variation component. The subtractor has its output signal amplified with an amplifier, with the output thereof being A/D-converted with an A/D converter.

Abstract: The invention relates to pulsed oximeters used to measure blood oxygenation. The current trend towards mobile oximeters has brought the problem of how to minimize power consumption without compromising on the performance of the device. To tackle this problem, the present invention provides a method for controlling optical power in a pulse oximeter. The signal-to-noise ratio of the received baseband signal is monitored, and the duty cycle of the driving pulses is controlled in dependence on the monitored signal-to-noise ratio, preferably so that the optical power is minimized within the confines of a predetermined lower threshold set for the signal-to-noise ratio. In this way the optical power is made dependent on the perfusion level of the subject, whereby the power can be controlled to a level which does not exceed that needed for the subject.

Abstract: An improved pulse oximeter provides for simultaneous, noninvasive oxygen status and photoplethysmograph measurements at both single and multiple sites. In particular, this multiple-site, multiple-parameter pulse oximeter, or “stereo pulse oximeter” simultaneously measures both arterial and venous oxygen saturation at any specific site and generates a corresponding plethysmograph waveform. A corresponding computation of arterial minus venous oxygen saturation is particularly advantageous for oxygen therapy management. An active pulse-inducing mechanism having a scattering-limited drive generates a consistent pulsatile venous signal utilized for the venous blood measurements. The stereo pulse oximeter also measures arterial oxygen saturation and plethysmograph shape parameters across multiple sites.

Abstract: A method for calibrating a pulse oximeter device and an apparatus incorporating the method and a system for utilizing the method. The method is based on modeling light propagation in tissue at two wavelengths, typically, one in the red and one in the infrared range of the spectrum. A formula is derived relating the arterial oxygen saturation to a ratio R commonly measured by standard pulse oximeters. A specific parameter is identified and utilized in the calibration of the oximeter. This parameter is formulated in terms of the DC signals measured by the pulse oximeter at the two wavelengths. An empirical method for estimating this parameter based on experimental data is also described.

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: An apparatus for measuring a concentration of a light-absorbing substance in blood is disclosed. A light emitter emits light beams to irradiate a living tissue, each of the light beams being associated with one wavelength which is absorbed by the blood. A first instrument measures first intensities of the light beams, which are to be incident on the living tissue. A second instrument measures second intensities of the light beams, which are transmitted through the living tissue. A first calculator calculates an attenuation variation ratio, which is a ratio of attenuation variations of the respective light beams due to variation of a volume of the blood caused by pulsation, based on the second intensities of the light beams. A second calculator calculates the concentration based on the first intensities, the second intensities, and the attenuation variation ratio.

Abstract: A method for determining an arterial blood oxygen saturation level according to this invention includes measuring the light transmittance through tissue of light of a first wavelength and a second wavelength. A steady-state component of the measured light transmission is used to select an appropriate calibration curve. A pulsatile component of the measured light transmission is used to determine the arterial blood oxygen saturation level using the selected calibration curve. An oximetry system is also provided. An improved oximetry system is further provided wherein a plurality of light transmission measurements are used to determine a blood oxygen saturation 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: Sensors and monitors for a physiological monitoring system having capability to indicate an accuracy of an estimated physiological condition. The sensor senses at least one physiological characteristic of a patient and is connectable to a monitor that estimates the physiological condition from signals detected by the sensor. The sensor includes a detector for detecting the signals from the patient which are indicative of the physiological characteristic. The sensor is associated with a memory configured to store data that defines at least one sensor signal specification boundary for the detected signals. The boundary is indicative of a quality of the signals and an accuracy of the physiological characteristic estimated from the signals by the monitor. The sensor further includes means for providing access to the memory to allow transmission of the data that defines the at least one sensor boundary to the monitor.

Abstract: A method and apparatus extract a signal component of a measured signal using one of two methods. If the signal component in the measured signal is a periodic signal with a certain well-defined peak-to-peak intensity value, upper and lower envelopes of the measured signal are determined and analyzed to extract said signal component of the measured signal. This signal component can further be used to calculate a desired parameter of the sample. The DC component of the signal is determined as the median value of the upper envelope, and the AC component is determined as the median value of the difference between the upper and lower envelopes. If the signal component of the measured signal is a periodic signal characterized by a specific asymmetric shape, a specific adaptive filtering is applied to the measured signal, resulting in the enhancement of the signal component relative to a noise component.

Abstract: A system determines heamtocrit transcutaneously and noninvasively. Disclosed are a finger clip assembly and an earlobe clip assembly, each including at least a pair of emitters and a photodiode in appropriate alignment to enable operation in either a transmissive mode or a reflectance mode. At least two, and preferably three, predetermined wavelengths of light are assed onto or through body tissues such as the finger, earlobe, or scalp, etc. and the extinction of each wavelength is detected. Mathematical manipulation of the detected values compensates for the effects of body tissue and fluid and determines the hematocrit value. If a fourth wavelength of light is used which is extinguished substantially differently by oxyhemoglobin and reduced hemoglobin and which is not substantially extinguished by plasmas, then the blood oxygen saturation value, independent of hematocrit, maybe determined. It is also disclosed how to detect and analyze multiple wavelengths using a logarithmic DC analysis technique.

Abstract: Sensors and monitors for a physiological monitoring system having capability to indicate an accuracy of an estimated physiological condition. The sensor senses at least one physiological characteristic of a patient and is connectable to a monitor that estimates the physiological condition from signals detected by the sensor. The sensor includes a detector for detecting the signals from the patient which are indicative of the physiological characteristic. The sensor is associated with a memory configured to store data that defines at least one sensor signal specification boundary for the detected signals. The boundary is indicative of a quality of the signals and an accuracy of the physiological characteristic estimated from the signals by the monitor. The sensor further includes means for providing access to the memory to allow transmission of the data that defines the at least one sensor boundary to the monitor.

Abstract: A method and apparatus extract a signal component of a measured signal using one of two methods. If the signal component in the measured signal is a periodic signal with a certain well-defined peak-to-peak intensity value, upper and lower envelopes of the measured signal are determined and analyzed to extract said signal component of the measured signal. This signal component can further be used to calculate a desired parameter of the sample. The DC component of the signal is determined as the median value of the upper envelope, and the AC component is determined as the median value of the difference between the upper and lower envelopes. If the signal component of the measured signal is a periodic signal characterized by a specific asymmetric shape, a specific adaptive filtering is applied to the measured signal, resulting in the enhancement of the signal component relative to a noise component.

Abstract: A method and system for simulating living tissue which is to be monitored by a pulse oximeter that provides red and infrared light flashes, the system including structure for: converting the red and infrared light flashes of the pulse oximeter into electrical signals; modulating the converted electrical signals to provide modulated electrical signals; and converting the modulated electrical signals to light flashes and transmitting the converted light flashes to the pulse oximeter for detection so that the pulse oximeter responds to the converted light flashes as it would to light flashes modulated by a living tissue.