Abstract: A bandage for attaching a sensor to a part of the human body while protecting the sensor against contamination and permitting its reuse in which the sensor is located within a flexible transparent sleeve which is fastened to the adhesive inner surface of the bandage, the parts of the bandage inner adhesive surface outside of the sleeve thereafter being fastened to the body. In the preferred embodiment the probe is an oximeter probe with a light emitter and a light detector. Apertures are provided in the bandage to view the positioning of the oximeter components.

Abstract: An improved blood analyzing device is disclosed for measuring the hematocrit and oxygen saturation levels of a quantity of blood. The device comprises a housing having a carriage assembly electrically interfaced thereto. Disposed within the carriage assembly is a light emitting means and a plurality of light detecting optical sensors which are used to provide hematocrit and oxygen saturation signals based on the scattering of light within a blood containment vessel disposed within the carriage. Signals generated from the sensors are processed by control electronics disposed within the housing so as to output a hematocrit measurement which is compensated for the effects of oxygen saturation, pH, and temperature, and an oxygen saturation measurement which is compensated for the effects of hematocrit, pH, and temperature.

Abstract: An oximeter that measures both the total hemoglobin concentration in whole, undiluted blood and the percentage of the hemoglobin saturated with oxygen. The oximeter uses red and infrared light-emitting diodes to illuminate a capillary tube filled with a sample of whole, undiluted blood. Light scattered by the blood travels a short distance down the length of the capillary tube and reaches a photodetector, the output of which is amplified, digitized, and fed to a microprocessor. The microprocessor computes the total hemoglobin concentration as a nonlinear monotonic function of the infrared light intensity. Oxyhemoglobin saturation is computed from the ratio of the logarithms of the intensities of red and infrared light. The invention provides a measurement of oxygen saturation without calibration shifts present in other oximeters due to fluctuations in total hemoglobin concentration.

Abstract: A medical sensor for measuring oxygen saturation contains encoding means for encoding the type of sensor. An oximeter comprises corresponding decoding means. The type of sensor represents the place of application at the human body. The oximeter uses this information to calculate oxygen saturation in dependence the place of application and for further purposes.

Abstract: The present invention utilizes the difference of light reception data generated based on the difference in length of substantial optical diffusion paths between a single light receiving point and a plurality of irradiation points, or between a plurality of light receiving points and a single irradiation point. According to the present invention, the inside information of substance based on the difference in length of the optical diffusion paths, may be measured. Even though measurements are made under different measuring conditions as to the part to be measured, the measuring time, etc., there may be obtained reliable measured data of the inside information with good reproducibility.

Abstract: In a liver function testing apparatus, light sources (11, 12) expose vital tissue (15) to first light of a wavelength capable of being absorbed by a specific dye dosed into blood of the vital tissue to be taken in and removed by the liver, and second light of a wavelength not capable of being absorbed by the specific dye. Optical pulses obtained from the vital tissue are received by a light receiving element (13), the output of which is sampled by an A/D converter (30) for converting the analog output signals into digital signals. A biocalibration is preformed on the basis of variable components in the blood. For this purpose a CPU (34) determines coefficients for first and second regression line expressions before and after an injection of the specific dye. The coefficients are provided by first and second photoelectric conversion signals.

Abstract: A liver function testing apparatus, provides light signals (11, 12) exposing vital tissue (15) to a first light signal that is substantially absorbed by a specific dye dosed into the blood of the vital tissue. The dye is to be taken in and removed by the liver. A second light signal is substantially not absorbed by the specific dye. Optical pulses obtained from the vital tissue are received by a light receiving element (13), the output of which is sampled by an A-D converter (30) to provide digital output signals. On the basis of variable components in the blood, a CPU (34) determines a coefficient of a regression line expression between first and second photoelectric conversion signals, to perform a biocalibration.

Abstract: An apparatus for photo-optically detecting transducer motion in a transducer using a photodetector elastically suspended inside the transducer housing and photo-optically coupled to a light source. During movement the inertia effect of the photodetector along with the elastic suspension system causes the changes in the photo-optical coupling between the photodetector and the light source. The inertia effect of the photodetector is enhanced by adding a mass to the photodetector. Either the magnitude or the phase of the photodetector output is monitored to detect movement.

Abstract: A bundle of fiber-optic sensors that resist breakage, for use in measuring pH, CO.sub.2, and O.sub.2 concentration, and a method of making the same. Three otpical fibers are enclosed in a common polyimide sheath and extend parallel to one another toward a distal end of the sensor, where they are bonded together in a mutually supportive array. At the distal end of one of these optical fibers is disposed a pellet comprising a CO.sub.2 analyte indicator molecule codissolved within a polymer matrix. A thin reflective surface of gold foil is provided on the pellet such that incident light transmitted through the optical fiber and polymer matrix is reflected back into the optical fiber. The CO.sub.2 polymer matrix absorbs light of a given wavelength to an extent dependent upon the level of CO.sub.2 present.

Abstract: An optical examination apparatus for optically examining density, distribution, etc.

Abstract: An endoscope including a light source for generating light beams having difference wavelengths to an object in an internal organ such as the stomach and the intestines of a subject, in which picture signals are picked up by a pickup device such as an optoelectronic device from the object radiated with the light beams, in which correction signals such as reference picture signals for correcting sensitivities of the light source and the pickup device depending on the different wavelengths of the light beams are picked up by the pickup device from a reference member such as a reference white plate radiated with the same light beams, and in which a bloodstream amount and an oxygen saturation rate are operated from the picture signals and the correction signals. The bloodstream amount and the oxygen saturation rate may be displayed on a display. The correction signals may be picked up outside the body of the subject.

Abstract: Method and apparatus for spectrophotometrically determining the concentration of a number of hemoglobin derivatives comprising at least deoxyhemoglobin and oxyhemoglobin or parameters derived from the concentration of individual hemoglobin derivatives, in particular the oxygen saturation fraction, in whole blood, in which light is transmitted to the blood under test, the modification on the light transmitted to the blood which the blood causes is determined at a number of individual wavelengths, and the concentrations (or the derived parameters) are determined on the basis of the light modification at the individual wavelengths and on the basis of predetermined coefficients representing the light absorption characteristics of each of the hemoglobin derivatives at each of the individual wavelengths, any error on the determination values due to turbidity being substantially compensated for by utilizing predetermined coefficients representing an absorption characteristic of turbidity at each of the wavelengths.

Abstract: A sensor and a method for determining the concentration or the partial pressure of oxygen comprising:(a) means for transmitting and collecting light to and from a light modifying medium; and(b) a light modifying medium containing a luminescent dye dispersed in or upon a matrix and the dye is accessible to oxygen, wherein said luminescent dye contains a hexanuclear core of molybdenum, tungsten or mixtures thereof having 14 coordination sites, wherein each coordination site is occupied by a ligand.

Abstract: A calibration device is provided for in vitro calibration of a light guide. The calibration device has a surface defining a cavity having an open end and a closed end opposite the open end. The opening is sized to receive the end portion of a light guide and a stop is provided near the closed end to prevent the light guide from contacting the inner surface of the closed end and to define an air gap between the end face of the light guide and the inner surface of the closed end. The inner surface of the closed end is flat and perpendicular to the longitudinal axis of the light guide. The light guide directs light from the end face of the light guide across the gap and against the flat surface. The calibration device is formed of a suitable material, such as polyethylene, with a plurality of light scattering particles and a plurality of light absorbing particles having neutral density filter properties uniformly distributed therein.

Abstract: A device and method for calibration of pulse oximeters is disclosed. A standard specimen that has optical characteristics of hemoglobin of a known oxygen saturation is placed in the light path of a pulse oximeter probe. The image of a pulse is created by a filter that periodically increases and decreases the amount of light allowed to reach the sensor of the probe. In one embodiment, the filter comprises a pair of polarizing filters rotated with respect to one another under the control of a digital computer with a motor interface device. In another embodiment, a wedge of a light-attenuating medium, such as a cuvette containing oxygenated blood, is reciprocated in the light path, the wide portions of the wedge attenuating a greater amount of light than the narrow portions. Such a cuvette can include filler openings, with outwardly extending tubes at both the wide and narrow ends.

Abstract: A method and device are disclosed for the detection of the relative percentage of at least one light absorber in the blood stream of living tissue. The method and device are based upon the employment of a narrow band width amplifier and pulses of different wavelength light sources wherein the frequency of the pulses of the light sources are selected so that a large component of the signal falls within the frequency of the narrow band amplifier, so that there is reduced likelyhood of interference from extraneous electromagnetic waves.

Abstract: An improved oximeter device for the calculation of oxygen saturation in arterial blood is provided. A pair of LED's are positioned to transmit red and infrared light through tissue containing the blood. A photo electric converter is provided to receive the transmitted light and convert it into a electrical signals. The probe can store data directed to various characteristics of the LED's, such as the primary wavelength and a secondary wavelength of the LED and an indication of the amount of crosstalk that can occur in the signals. The correction of any errors resulting from crosstalk plus the calculation of oxygen saturation depending on the various characteristics of the LED's can be effectuated.

Abstract: Disclosed in an optical fiber transducer system with energy generating means for transmitting pulsing energy at various frequencies to bidirectional couplers for each frequency. The couplers record the intensity and further transmit the pulsing energy to a wavelength multiplexer/demultiplexer. The wavelength multiplexer/demultiplexer combines the plurality of energy supply means into a single output for an optic fiber which includes an optical delay sufficient to time separate the pulsing waves of energy. Reflected energy is transmitted back through the same wavelength multiplexer/demultiplexer, bidirectional coupler so that the recorded intensity of transmission and reflectance are comparable without system influence.

Abstract: In order to measure the oxygen saturation in venous blood, a venous blood stream is made time-variant by applying pressure with a peak value of the minimum blood pressure to a proximal portion from a measuring part. Light beams with different wavelengths are transmitted from the measuring part and detected by photodiodes. Photodetected signals are logarithm-converted and venous signal components are separated from logarithm-converted signals with a filter circuit. The oxygen saturation of venous blood is calculated on the basis of separated venous signal components.

Abstract: An examination apparatus which measures the oxygenation in objects with near infrared light transmission spectrophotometry and that automatically adjusts a transmission light quantity to a magnitude suitable for detection by a photomultiplier tube. The examination apparatus comprises a ring-like ND filter whose transmission factor varies along its circumference, a filter driver for automatically setting a transmission factor of a filter, and a light source control device for automatically controlling output powers of light sources.

Abstract: An examination apparatus measures the oxygenation in body organs by the near infrared light transmission spectrophotometry. To inspect the examination apparatus itself before the oxygenation measurement, an illumination-side fixture and a detection-side fixture have such structures that these fixtures can be assembled together in such a manner that near infrared light is directly made incident on the detection-side fixture from the illumination-side fixture. In the midst of the measurement, the examination apparatus is regularly inspected and a photomultiplier tube can be separately inspected by employing a separate light source for inspection.

Abstract: Sensing apparatus for remote sensing of quantities such as blood oxygen concentration using a phosphorescent material located at one end of an optical fiber. The phosphorescent material emits a relatively long-lived luminescence when exposed to energy in a predetermined wavelength range. The sensing apparatus includes a light source for generating an incident pulsed energy signal within the predetermined wavelength range and a detector subsystem for selectively detecting the long-lived luminescence from the phosphorescent material. The light source and the detector subsystem are coupled to the other end of the optical fiber along a common optical path. The detector subsystem includes dual channels for detecting a measuring wavelength and a reference wavelength in the long-lived luminescence. The detector subsystem is inhibited during the incident pulsed energy signal to provide low noise operation. The detected signals are integrated and averaged to improve accuracy.

Abstract: A feedback control system is disclosed for use in processing signals employed in pulse transmittance oximetry. The signals are produced in response to light transmitted through, for example, a finger at two different wavelengths. Each signal includes a slowly varying baseline component representing the relatively fixed attenuation of light produced by bone, tissue, skin, and hair. The signals also include pulsatile components representing the attenuation produced by the changing blood volume and oxygen saturation within the finger. The signals are processed by the feedback control system before being converted by an analog-to-digital (A/D) converter (72) for subsequent analysis by a microcomputer (16). The feedback control system includes a controllable offset subtractor (66), a programmable gain amplifier (68), controllable drivers (44) for the light sources (40, 42), and the microcomputer (16).

Abstract: A pulse oximeter having a sensor responsive to light transmitted through an area of blood flow which is optically absorbed by hemoglobin for producing a pulsatile waveform indicating the current pulsatile component of blood flow. A process waveform is created for tracking the process of the oximeter during its determination of a maximum and a minimum value of the pulsatile waveform, which is used for calculating the saturation of oxygen.

Abstract: An improved optical sensor which has increased sensitivity and which is resistant to the effects of ambient light. In one embodiment of the invention, the sensor housing has a flat lower face with a central protrusion in which a plurality of light emitting diodes and an optical sensor are mounted. When the sensor is placed on the patient's tissue, the portion of the sensor face containing the LEDs and detector protrudes slightly into the tissue to provide improved optical coupling of the sensor to the skin. A light absorbing compliant material is attached to the perimeter of the sensor to reduce the effects of ambient light and to provide a cushion to minimize discomfort to the patient. In an alternate embodiment of the sensor, the LEDs and detector are mounted in a horizontal configuration substantially parallel to the surface of the tissue. The light produced by the LEDs is projected into a central chamber of the housing where the respective beams are combined and directed toward the tissue.

Abstract: A device and method for determining pulses in a modulated signal is disclosed. The modulated signal is processed and converted into a quantized analog type of digital data stream. The data stream is evaluated over time by considering preceeding and subsequent values in the data stream to generate a filtered wave form. By using extreme values in the filtered wave form pulse detection is accurately determined regardless of whether the modulated signal has complicating features, such as dicrotic notch, or high noise levels, or both.

Abstract: A reflection type oximeter comprises light emitting diodes (11 to 16) as first to sixth light sources which emit first and second beams of a wavelength involving a change in absorption due to a change an oxygen saturation of hemoglobin in blood of a tissue of a living body, third and fourth beams of another wavelength involving no change in absorption, and fifth and sixth beams of a further wavelength involving a relatively small change in absorption due to changes in a quantity of hemoglobin an oxygen saturation. The beams ae applied to the body tissue and the beams of the first to sixth light sources reflected by the body are received by a light receiving element (17). Intensities of the beams emitted from the light emitting diodes are set to predetermined levels and the intensities of the beams received by the light receiving element are evaluated by a CPU (23). Based on a predetermined function, the quantity of hemoglobin and of the oxygen saturation of the body tissue are evaluated.

Abstract: A sensor appliance removably attachable to a living body for non-invasively producing signals indicative of a condition of the body and applying them to a monitoring or measuring device and method of making the appliance characterized by a small, highly flexible light weight substrate with surface mounted light emitting and photodetector components hermetically sealed in a flexible moisture resistant envelope. Provision is made for inclusion of a form sustaining spine to enhance positional stability.

Abstract: An apparatus for noninvasive determination of constituent concentrations utilizing light wave absorption measurements and methods for processing signals generated by such measurements.

Abstract: The disclosed invention is for use in extracting more accurate information from signals employed in pulse oximetry. Basically, pulse oximetry involves the illumination of arterial blood flowing in tissue with light at two wavelengths. Upon emerging from the tissue the light is received by a detector (38) that produces signals that are proportional to the intensity of the light received at each of the wavelengths. Each signal includes a slowly varying baseline component representing the attenuation .beta.(t) of light produced by bone, tissue, skin, and hair. The signals also include pulsatile components representing the attenuation .alpha.(t) produced by the changing blood volume and oxygen saturation within the finger. The signals produced by the detector (38) are converted by an analog-to-digital (A/D) converter (72) for subsequent analysis by a microcomputer (16). The microcomputer (16) extracts the following information from the signal corresponding to each wavelength. V.sub.

Abstract: An oximeter apparatus especially adapted to reflectance oximetry includes a sensor having a red LED, an infrared LED and a photosensor resiliently mounted in a carrier to provide constant linear pressure characteristics. The LED's and photodetector are fixed to a flexible circuit board. The d.c. components of the reflectance signals are fed back to control the brightness of the LED's A.c. component signals from the photodetector are rejected in the determination of oxygen saturation when the red and infrared a.c. components differ by more than a determined amount. The difference between the maximum and minimum values of each pulse is employed in the determination of oxygen saturation, with two measurements being taken for each pulse.

Abstract: A noninvasive optical oximeter for measuring oxygen saturation of arterial blood. A sample of blood is illuminated with light at four different wavelengths. Light reflected by the blood is sensed by a photodetector and a plurality of output signals are created in response thereto. The reflected light at each of the four wavelengths is detected after contact with the blood and is correlated with the oxygen saturation of the patient's blood using mathematical relationships for arterial and venous oxygen saturation. The present invention provides a noninvasive backscatter oximeter which is capable of providing accurate indications of a patient's blood oxygen saturation without the need for obtaining prior information relating to the oxygen content of the patient's blood.

Abstract: A pulse oximeter is provided including two light emitting diodes. Each LED is energized by a unique modulation signal. Light produced by the LEDs passes through the tissue of a subject and is detected by a photodiode. The photodiode signal is separated by tuned circuits resonant at the two modulation signal frequencies and physiological information signals are recovered from the separated signals by amplitude demodulation. The inventive arrangement provides identification of back-to-back coupled LEDs and narrow band filtering for good noise immunity.

Abstract: A pulse oximeter or plethysmographic device utilizes light varying in intensity at a predetermined carrier frequency. A passive resonant circuit having a resonant frequency substantially equal to the carrier frequency is connected between the photodetector and the first amplifier. The resonant circuit serves to suppress spurious DC and low frequency components such as those due to ambient light and ambient light flicker and also to suppress high frequency interference. Because ambient light signals are suppressed, there is no need for dark current correction or restoration. Suppression of ambient light and other interference upstream of the front end amplifier avoids saturation of the amplifier and permits use of a front end amplifier having high gain.

Abstract: A device and method for calibration of pulse oximeters is disclosed. A standard specimen that has optical charactertistics of hemoglobin of a known oxygen saturation is placed in the light path of a pulse oximeter probe. The image of a pulse is also created by providing a filter that periodically increases and decreases the amount of light allowed to reach the sensor of the probe. In one embodiment, the filter can comprise a pair of polarizing filters rotated with respect to one another. In another embodiment, a wedge of a filtering medium, such as oxygenated blood, is reciprocated in the light path, the wide portions of the wedge attenuating a greater amount of light than the narrow portions.

Abstract: An apparatus for determining the concentration of a light-absorbing material contained in blood flowing through a tissue which minimizes the amount of error caused by noise and which ensures highly precise results at all times. The apparatus operates according the principle that light beams of different wavelengths are absorbed by different amounts when passing through the tissue at different portions of the blood pulsation cycle. A plurality of points are detected that fall in the vicinity of the peak and trough of a cycle of a light detection signal. For each wavelength of light, the values of the detection signals produced at each of these points in time is stored. The concentration of the light-absorbing material is computed in response to the stored detection signals.

Abstract: A measuring instrument for obtaining an intracardial signal indicative of blood oxygen saturation, which may be used to control the stimulation frequency of a heart pacemaker, has a measuring probe which contains a light transmitter and a light receiver. The light receiver receives light from the light transmitter reflected by the blood. The light transmitter and the light receiver are connected in parallel to an evaluation circuit via two leads. A constant current source is connected in series with the light transmitter. The current generated by the light receiver, indicative of blood oxygen saturation, can be identified by forming the difference between current flowing in the measuring probe and the constant current. A reference measurement to compensate for factors in the total current resulting from the lead resistances and the measuring probe temperature is not necessary.

Abstract: A finger sensor for a pulse oximetry system is provided having a body of flexible, resilient polymeric material formed as a pocket. On the inside walls of the pocket toward the closed end are a LED light source and an opposing photodetector. The space within the pocket transverse to the longitudinal dimension of the pocket exhibits a relatively smaller width and a relatively greater width. As a finger is inserted into the pocket with the fingertip between the LED and the photodetector, the relatively smaller width of the pocket expands and the relatively greater width of the pocket decreases. This expansion and decrease of the pocket dimensions are resisted by the resilient polymeric material, causing the walls of the pocket containing the LED and the photodetector to securely contact and retain the finger within the pocket.

Abstract: The present invention relates to an oximeter for monitoring oxygen saturation of arterial blood. Light of two wavelengths is transmitted through a specimen. Detectors measure the attenuation of light through the specimen to produce two modulating data streams. The data streams are thereafter processed, evaluated, and compared to determine oxygen saturation. A novel method to process, evaluate and compare the two data streams is disclosed.

Abstract: A feedback control system is disclosed for use in processing signals employed in pulse transmittance oximetry. The signals are produced in response to light transmitted through, for example, a finger at two different wavelengths. Each signal includes a slowly varying baseline component representing the relatively fixed attenuation of light produced by bone, tissue, skin, and hair. The signals also include pulsatile components representing the attenuation produced by the changing blood volume and oxygen saturation within the finger. The signals are processed by the feedback control system before being converted by an analog-to-digital (A/D) converter (72) for subsequent analysis by a microcomputer (16). The feedback control system includes a controllable offset subtractor (66), a programmable gain amplifier (68), controllable drivers (44) for the light sources (40,42), and the microcomputer (16).

Abstract: A blood constituent measuring apparatus and method, which can be used to measure the oxygen (or other blood constituent) content of the blood. The apparatus includes sources of two or more wavelengths of light for transmitting, e.g., red and infrared light through a portion of the body, and a photodetector for generating respective signals representing each wavelength of light transmitted through the body portion. The photodetector signals have pulsatile and non-pulsatile components. The oxygen content of the blood is computed based on the light transmitted through the body portion at each wavelength, as determined from the pulsatile component, amplified alone after the much larger non-pulsatile component is subtracted from it. The apparatus can compute the oxygen content of patients with weak pulses, or unstable physiological states, or both, by using, preferably, a plurality of independently settable gains, to maintain the signal level within a range suitable for accurate measurement.

Abstract: A heart pacemaker including a two wave length reflectance oximeter for determining oxygen saturation. The pacing rate is increased or decreased in response to the measured oxygen saturation. By appropriate multiplexing and timing functions, the two wave length reflectance oximeter is included in a pacing lead coupled to the pacemaker which requires only three conductors.

Abstract: A hemolysis reaction measuring device includes a hemolysis reacting member made of a light transmitting material and adapted to cause hemolysis reaction to take place therein, a light source supported so as to be able to project light toward a side portion of the hemolysis reacting member, and a light receiving member which allows the light emitted from the light source and passing through the hemolysis reacting member to be incident upon it so as to measure light absorbance of a liquid within the hemolysis reacting member based on the intensity of the incident light. The light source is formed by a light emitting diode.

Abstract: Methods and compositions are described for measuring oxygen concentration, particularly for monitoring oxygen in the blood with a fiber optic catheter. Oxygen concentration is determined by observing quenching of the emission from a luminescent (phosphorescent of fluorescent) molecule embedded in an oxygen-permeable matrix. A test fluid of unknown oxygen concentration is contacted with the matrix containing at least one luminescent substance. The matrix is subjected to irradiation over some period of time by light of a wavelength that is strongly absorbed by the luminescent substance, and a measure of the time dependence of luminescent emission intensity I(t) is obtained. Three modes of determining oxygen concentration from I(t) are described.

Abstract: A pulse oximetry system is provided in which LEDs of two different wavelengths illuminate tissue containing arterial blood flow. A photodiode receives light from the LEDs and produces electrical signals containing pulsatile components. The components of the two wavelengths are separated and the pulsatile waveforms are monitored until signal peaks are detected at the end of diastole. The waveforms are then integrated over the systolic interval, and the integrals are combined with the signal peak values to determine an index value. The index value is used to select a value representative of oxygen saturation from a look-up table.

Abstract: A measuring instrument for the intracardial acquistion of the blood oxygen saturation of a patient for use in controlling a heart pacemaker implanted in the patient has a measuring probe with a measuring current path which includes a light transmitter and a light receiver which receives light emitted by the light transmitter and reflected by the blood. The measuring probe is connected to an evaluation circuit via two lines. A useful signal measurement and a reference measurement, independent of the blood reflection, are made and the blood oxygen saturation is identified by comparing the two signals. A separate evaluation of the useful signal measurement and the reference signal measurement is enabled by making the useful signal measurement chronologically offset with respect to the reference measurement in one embodiment, or by using the amplitude of the current from the light receiver to make one measurement, and using the voltage amplitude to make the other measurement in another embodiment.

Abstract: A method of exposing a patient's extremity to light of two wavelengths and detecting the absorbance of the extremity at each of the wavelengths is provided comprising the steps of: (a) generating pulses of light having the first wavelength at a first pulse frequency; (b) generating pulses of light having the second wavelength at a second pulse frequency; (c) exposing the extremity to the first and second pulses; (d) producing an electrical signal corresponding to the total amount of light transmitted through the extremity; (e) separating the electrical signal produced in step (d) into a first amplitude-modulated electrical signal at the first pulse frequency and a second amplitude-modulated electrical signal at the second pulse frequency; and (f) demodulating the first and second amplitude-modulated electrical signals to produce a first signal corresponding to the amount of light transmitted through the extremity at the first wavelength and a second signal corresponding to the amount of light transmitted thro

Abstract: A spectrophotometric method is described of quantitatively determining the concentration of a dilute component in either a clear or a strongly light-scattering environment containing same in unknown concentration together with a reference component of known concentration, by a series of contemporaneous radiation-directing and measurement steps of radiation of selected varying wavelengths. Specific applications are disclosed involving the in situ, in vivo, non-invasive spectrophotometric determination of blood-borne as well as tissue species, e.g., hemoglobin, and oxyhemoglobin, and intra-cellular enzyme cytochrome c oxidase, in human body parts such as fingers, hands, toes, feet, earlobes, etc., as well as organs such as the brain, skeletal muscle, liver, etc.

Abstract: Apparatus and method for measuring the level of a constituent such as oxygen in the blood of a living subject. Light at a plurality of wavelengths is emitted and directed through the patient's body to a photodetector. The amplitude of the emitted light at each wavelength is varied in accordance with a different carrier frequency, and the photodetector signal thus includes a component at each carrier frequency. Each such component represents transmissivity of the body structure at one wavelength of the emitted light. The photodetector signal is subdivided by frequency so as to separate the components at the different carrier frequencies. The constituent level is determined from these separated components.

Abstract: The present invention relates to the processing of signals containing information about the pulse rate and oxygen saturation of arterial blood flowing in tissue. These signals have a relatively periodic pulsatile component superimposed upon a varying baseline component. To determine the pulse rate and oxygen saturation from the signals, the positive peaks, negative peaks, and period of the signal must be determined. The present invention accomplishes this by first searching for a sustained positive sloping region of the signal. Then the first derivative of the signal with respect to time is analyzed and points on the signal before and after the occurrence of a slope reversal marked. If the slope at the first point is positive, the interval between the two points is searched for a maximum amplitude that is identified as a positive peak. After the occurrence of a negative sloping region of the signal, another pair of points are marked occurring before and after a subsequent slope reversal.