Abstract: An apparatus of and method for measuring arterial blood oxygen saturation at a particular tissue level of interest. Visible and near infrared radiation are emitted into a patient at the measurement site using two different wavelengths. Detection at two different detection sites permits rejection of oxygen saturation at undesired tissue levels.

Abstract: A system for measuring a blood parameter, such as pH, pCO.sub.2 or pO.sub.2, comprises an optical probe with an optical fiber and an invasive blood sensor. Light emitted by a light-emitting diode (1) is irradiated into an optical fiber (2). The system compensates for variations in the luminous efficiency of the LED (1) in that either a fraction of the light is fed directly to a photodetector (22), or in that the forward voltage of the LED is measured, and in that the signal received from the sensor is either normalized, or in that the LED drive current is adjusted accordingly.

Abstract: A method and an apparatus enable detection of an irregular state in a non-invasive pulse oximeter system. The system comprises an oxygen saturation sensing probe for generating spectrophotometric signals and an oxygen saturation computing section for deriving arterial hemoglobin oxygen saturation from the spectrophotometric signals. Irregular states of the system are detected by pre-defining at least one criterion for distinguishing between spectrophotometric signals indicative of the normal state of the system and spectrophotometric signals generated by the pulse oximeter system when a predetermined non-physiological event occurs. Then it is judged whether the actual spectrophotometric signals fulfill this criterion. The presence of the irregular state is detected if the actual criterion fulfill the criterion.

Abstract: Methods are described for the in vivo topographic determination of tissue and bodily fluid oxygen concentration or PO.sub.2 within an imaged tissue, as well as a method for measuring blood or bodily fluid PO.sub.2 with a fiber optic catheter. In the first method, a lipid soluble, biocompatible fluorescent probe substance is administered to an animal body and accumulates within the lipid bilayers of its tissue cells. In the second method, the fluorescent probe substance is conjugated to a large molecular mass protein which causes it to be retained within a bodily fluid such as blood. In the third method describing a catheter design, in which PO.sub.2 is measured at the catheter tip, the tip contains the fluorescent probe substance dissolved in a viscous nonpolar solvent. In all methods described, a fluorescent probe substance is preferred whose fluorescence lifetime is quenched by molecular oxygen, and oxygen concentration or PO.sub.

Abstract: The improved pulse oximeter preprocesses the sets of red and infrared signals received from the probe. The set of pairs of processed red and infrared data points are fitted to a linear equation to compute the slope of the best fit line through these data points and account for noise in both of these sets of data points. A measure of the linearity of the input data points, if less than a predetermined threshold, indicates that a distorted signal has been received from the probe. The computed slope of the best fit line is converted to a RRatio which is used in a empirical calibration formula to compute the average SpO.sub.2 value.

Abstract: A system for determining the hematocrit 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 passed 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 plasma, then the blood oxygen saturation value, independent of hematocrit, may be determined.It is also disclosed how to detect and analyze multiple wavelengths using a logarithmic DC analysis technique.

Abstract: The quantitative determination of various materials in highly scattering media such as living tissue may be determined in an external, photometric manner by the use of a plurality of light sources positioned at differing distances from a sensor. The light from said sources is amplitude modulated, and, in accordance with conventional frequency domain fluorometry or phosphorimetry techniques, the gain of the sensor is modulated at a frequency different from the frequency of the light modulation. Data may be acquired from each of the light sources at differing distances at a frequency which is the difference between the two frequencies described above. From these sets of data from each individual light source, curves may be constructed, and the slopes used to quantitatively determine the amount of certain materials present, for example oxyhemoglobin and deoxyhemoglobin in living tissue.

Abstract: Methods are described for the in vivo topographic determination of tissue and bodily fluid oxygen concentration or PO.sub.2 within an imaged tissue, as well as a method for measuring blood or bodily fluid PO.sub.2 with a fiber optic catheter. In the first method, a lipid soluble, biocompatible fluorescent probe substance is administered to an animal body and accumulates within the lipid bilayers of its tissue cells. In the second method, the fluorescent probe substance is conjugated to a large molecular mass protein which causes it to be retained within a bodily fluid such as blood. In the third method describing a catheter design, in which PO.sub.2 is measured at the catheter tip, the tip contains the fluorescent probe substance dissolved in a viscous nonpolar solvent. In all methods described, a fluorescent probe substance is preferred whose fluorescence lifetime is quenched by molecular oxygen, and oxygen concentration or PO.sub.

Abstract: With the crude instrumentation now in use to continuously monitor the status of the fetus at delivery, the obstetrician and labor room staff not only over-recognize the possibility of fetal distress with the resultant rise in operative deliveries, but at times do not identify fetal distress which may result in preventable fetal neurological harm. The invention, which addresses these two basic problems, comprises a method and apparatus for non-invasive determination of blood oxygen saturation in the fetus. The apparatus includes a multiple frequency light source which is coupled to an optical fiber. The output of the fiber is used to illuminate blood containing tissue of the fetus. In the preferred embodiment, the reflected light is transmitted back to the apparatus where the light intensities are simultaneously detected at multiple frequencies. The resulting spectrum is then analyzed for determination of oxygen saturation.

Abstract: The relative concentration of a material such as glucose in a turbid medium such as living tissue may determining the scattering coefficient of the light that has passed through the turbid medium; and comparing the scattering coefficient with a previous scattering coefficient determined with respect to the turbid medium.

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 apparatus for evaluating a peripheral blood flow of a living subject, including a reflection-type pulse wave detecting device including two pairs of light-emitting and light-receiving elements provided such that a distance between the light-emitting and light-receiving elements of one pair is different from that of the other pair; and a determining device for determining an attenuation coefficient of the light beam emitted by the light-emitting element of each pair, based on (a) an intensity of the light beam which is emitted by the light-emitting element of each pair and (b) an intensity of the light which has been emitted from the light-emitting element of each pair, reflected from skin of the subject, and subsequently received by the light-receiving element of each pair.

Abstract: A non-invasive blood pressure measurment device including: a cuff, a pressure detector for detecting a cuff pressure; a cuff pressure control pump for linearly increasing or decreasing the cuff pressure; a light-emitting member for injecting a beam of light into a part of a body by the cuff; light-receiving members for detecting an amount of light transmitted or an amount of light reflected of the beam of light injected into the body from the light-emitting member; a demodulating circuit for separating a pulsatile component from the light-receiving signal obtained from the light-receiving members; a CPU for sending a control signal to the cuff pressure control pump to thereby either increase the cuff pressure if it is judged that the pulsatile component has not been detected before applying pressure to the cuff based on the detection output from the demodulating circuit or decrease the once increased cuff pressure, and detecting an inflection point in the light-receiving signal in the course of increasing or

Abstract: Spectrophotometric apparatus and related methodology, including a sensor having a source and at least two receivers of electromagnetic radiation such as red and/or near-infrared light, which is applied non-invasively to the outer periphery of a patient or other animate test subject to examine a particular internal region to which is disposed beyond a peripheral extremity of specifically indeterminant thickness lying immediately inwardly of the outer periphery of the test subject.

Abstract: An oximetric sensor probe is movably coupled to a patient's finger to facilitate transillumination and detection of optical energy through a portion of the patient's finger without subjecting the finger to significant deformation. The finger is received within a receptacle having a cup-shaped closed end and an opposite open end that is rolled up upon itself and is adapted to be unrolled longitudinally along the finger to form a tubular enclosure which closely surrounds the finger. An optical source and an optical detector are arranged in spaced axial alignment with each other on opposite sides of the finger so that optical energy transmitted by the source through the finger is received by the detector. The detected light is analyzed to noninvasively determine the saturation of oxygen within the patient's blood.

Abstract: An improved pulse oximeter for the measurement of oxygen saturation in the blood, which is faster and more accurate than conventional pulse oximeter. Improved speed and accuracy is attached by elimination of normalization and feedback circuitry and the use of analog to digital converting devices having a wide dynamic range along with a sophisticated computer analysis. The instant invention eliminates inaccuracies resulting from channel matching errors, and detects and eliminates aberrant input data.

Abstract: There is disclosed a device capable of continuously measuring the presence and concentration of an analyte or analytes and a method for using said device in a liquid and/or a gas phase reaction volume. The inventive device comprises a sensor probe, a reservoir, and a detector. The inventive device delivers reagent to the sensor probe in a flow method to directly and continuously renew reagent, thereby allowing the continuous measurement of the presence and the concentration of an analyte or analytes.

Abstract: Non-invasive oximetry wherein red and infrared light from light sources energized at different frequencies is applied to arterial blood-containing tissue of a living subject. The red and infrared light coming from this tissue is sensed in order to obtain frequency-muliplexed information as to the absorption of said light by said tissue, the information being processed in order to derive therefrom a measure of percent oxygen saturation of said blood. The processing includes filtering for separating information represented by red light absorption from information represented by infrared light absorption. In particular, both notch and bandpass filters are used, and AM detectors provide for further separating such information into DC and AC components.

Abstract: A pulse oximeter sensor apparatus which is sealed against liquid penetration during its formation by overmolding, and methods for overmolding. The pulse oximeter sensor apparatus disclosed comprises a preform first section, oximeter sensor components, and an overmolded second section bonded to the preform first section during the overmolding process to form a liquid resistant seal comprising a mechanical bond of overlapping elements.

Abstract: A pulse oximeter sensor with a light source optimized for low oxygen saturation ranges and for maximizing the immunity to perturbation induced artifact. Preferably, a red and an infrared light source are used, with the red light source having a mean wavelength between 700-790 nm. The infrared light source can have a mean wavelength as in prior art devices used on adults. The sensor of the present invention is further optimized by arranging the spacing between the light emitter and light detectors to minimize the sensitivity to perturbation induced artifact. The present invention optimizes the chosen wavelengths to achieve a closer matching of the absorption and scattering coefficient products for the red and IR light sources. This optimization gives robust readings in the presence of perturbation artifacts including force variations, tissue variations and variations in the oxygen saturation itself.

Abstract: A pulse oximeter probe can be attached securely to the ear of a subject without compressing the site of measurement, and permits precise measurements and which can be used as a disposable product. A covering member formed as a tubular bag of a flexible synthetic resin is provided with light-emitting element and light-receiving element at opposite ends, and holding member consisting of main body and moving flap is inserted into the covering member.

Abstract: An optical sensor system (such as an oximeter system) for use on a patient in an electrical environment (such as an RF field) includes at least one of the following three subsystems: (A) A light input subsystem includes a first control and display module disposed remotely outside of an electrical field, and input electrical cable connected at one end to the first module and at the other end to an electrically-powered light source disposed closely adjacent but outside of the electrical field. Input fiber optic cable for the transmission of analog optical signals extends from the light source to adjacent a patient in the electrical field. (B) A light output subsystem includes output fiber optic cable for the transmission of analog optical signals extending from adjacent the patient in the electrical field to a light detector disposed closely adjacent but outside of the electrical field.

Abstract: A flexible sensor assembly for detecting optical pulses in which said sensor assembly comprises a flexible printed circuit having mounted thereon at least one light emitting diode and at least one photoelectric detector connected to different circuit patterns with an insulative tape secured over the circuit and components and wherein the flexible sensor is adapted to be folded so that the photoelectric detector can be spaced from and disposed over the light emitting diode.

Abstract: Disclosed is an apparatus for measuring a predetermined data of a living tissue, such as an oxygen saturation, a dye dilution curve and level of hemoglobin. The apparatus has an illumination intensity computing and storing circuit that stores the intensities of light components emitted from a three-wavelength light source assembly, and a computing circuit that calculates the intensity ratios of illuminating light from the intensity data stored in the circuit. The circuit determines the predetermined data of blood on the basis of the calculated intensity ratios and the intensities of light transmitted through a living tissue under assay, and it displays the predetermined data on display unit. The apparatus is capable of measuring the predetermined data without relying upon pulsations that occur in the subject.

Abstract: A non-invasive and an in-vitro method for determining a person's hemoglobin concentration are described. The methods employ substantially simultaneous measurements of absorbance of near-infrared and long wavelength visible light. The measurement consists of a combination of ordinary absorbance data at multiple wavelengths in the form of a ratio or of a ratio of derivative absorbance data. The method minimizes the need for path-length measurement or extinction coefficient determination or estimation of scattering losses. In the in-vitro setting, the method minimizes the need for cell lysis or for reagents.

Abstract: A system for determining the hematocrit 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 passed 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 plasma, then the blood oxygen saturation value, independent of hematocrit, may be determined.It is also disclosed how to detect and analyze multiple wavelengths using a logarithmic DC analysis technique.

Abstract: An improved noninvasive, electrooptical sensor probe is suitable for removable attachment to the skin of a patient to measure light extinction during transillumination of the blood-perfused tissue beneath the skin. According to the preferred embodiment of the probe, the probe has a unitary chassis having two widened ends connected by a flexible bridge. The topside of each widened end has a concave finger location saddle. The underside of the chassis has a cavity to receive an electrical sensor assembly including a light source and a photosensor. The probe further includes a foam backing having a front end connected to a back end by a neck, and two wings which extend laterally from opposing sides of the back end. The foam backing has an adhesive topside, which is bonded to the underside of the chassis to capture the electrical sensor assembly in the cavity of the chassis. Removable release tabs cover the adhesive topside of the wings prior to the application of the probe to a patient.

Abstract: A pulse oximeter which modifies the alarm condition when motion is detected. Basically, if the lack of a pulse is determined to be as a result of motion artifact, the generation of an alarm is postponed. In addition, the display indicates that motion is present and that the last reading is questionable due to the presence of motion. The invention also determines if motion artifact is present from the pulse oximeter detector signal itself. The ratio of the positive and negative peaks of the derivative of the pulse signal are compared to a motion/blood pulse threshold.

Abstract: A calibration boot for use with an optical catheter includes a plurality of materials, each having a different reflectivity characteristic with respect to known wavelengths of light. The boot is positioned over the distal end of the optical catheter and light is emitted from the distal end of the optical catheter into one of the materials at a time. At each emission, the reflected or backscattered light is measured by a detector and a plurality of signals are obtained. The plurality of readings are used to calibrate the overall optical catheter and system. The use of a plurality of calibration signals improves the overall system accuracy, particularly where two or more variables are present in the measured parameter. In the preferred system, the parameter being sensed in the oxygenatin of blood invasively.

Abstract: A improved pulse oximeter comprises first and second light-emitting diodes that apply red light and infrared light, respectively, to a living tissue including the arterial blood, a photodiode for detecting optical outputs as produced after the red and infrared light of two wavelengths issuing from light-emitting diodes have been absorbed by the living tissue, a first computing unit that computes the ratio between the pulsating components of light absorbance .PHI. for the two wavelengths due to the arterial blood on the basis of the dc components and pulsating components of the respective wavelengths that are obtained from the reception outputs of the photodiode, a correction circuit that not only detects the degree of fluctuation in the absorbance ratio .PHI. as produced from the first computing unit but which also holds the pulsating components of the respective wavelengths when they are stable and which, if there is a fluctuation in the absorbance ratio .PHI., computes a corrected absorbance ratio .PHI.

Abstract: Disclosed herein is an optical organism measuring apparatus in which cables provided on both light transmission and receiving sides are sufficiently reduced in diameter and provided with flexibility for attaining handleability while light can be transmitted and received in high efficiency so that information can be obtained from a deep portion in an organism. Semiconductor lasers (2-1, 2-2, 2-3) are coupled with incident ends of a plurality of single core optical fibers which are contained in a flexible probe (12), so that laser light guided by the single core optical fibers is applied to an organism (8) from a forward end portion of the probe (12). A light receiving probe (18) is provided on its forward end with a silicon photodiode (14), which is attached in close contact to the organism (8) to receive light transmitted through or reflected by the organism (8). This silicon photodiode (14) is integrated with a preamplifier (16).

Abstract: A compact pulse oximetry system which separates the combined signal into its respective AC and DC components. By separating the signal into AC and DC components, a smaller order bit A/D converter may be used while still maintaining signal accuracy. Instead of using the combined signal to calculate the oxygen saturation content, the system microprocessor computes the Ratio of Ratios using the derivative of the separated AC component of the diffused signal to calculate the oxygen saturation of the measured fluid. To calculate the Ratio of Ratios, a ratio of the derivative value of the separated AC component is used. Instead of taking a single sample between the peak and valley of the signal, the oximeter system samples each value. To decrease the effect of system noise, a linear regression is performed over each sample.

Abstract: First and second carrier signals, distinguishable by phase, are respectively applied to infrared and red energy emitters. A detector receives the sum of the energy after modulation at the infrared and red wavelengths. The signal received by the detector is then demultiplexed into its original first and second components, thereby allowing determining of both the infrared and red modulation components. The first and second carrier signals may comprise time-varying periodic signals with identical frequency and frequency spectra, such as a pair of sine waves which are indistinguishable except by phase and amplitude. A 90.degree. phase difference is preferred, but any phase other than 0 or an integer multiple of 180.degree. is workable. A carrier frequency which avoids excessive interference from ambient light is preferred.

Abstract: Disclosed is a method and apparatus for determining the presence and/or concentration of chemical species which absorb electromagnetic energy, dependent to a degree upon the chemical species and the wavelength of electromagnetic energy applied to matter including said species. The absorbed electromagnetic energy generates acoustic energy which is detected and analyzed to determine the presence and/or concentration of the chemical species in the matter.

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.

Abstract: A method and apparatus for determining the parameters (i.e., proportion, mean, and standard deviation) of constituent subpopulations within a sample population of particles which contains overlapping populations. The invention includes the use of the EM algorithm, an iterative process which estimates the probability that a particle belongs to any given overlapping subpopulation.

Abstract: An electronic processor for calculating in vivo blood oxygenation concentration levels using pulsed light that eliminates both requirements for comparing photosensor signal amplitudes with analog/digital circuit dynamic ranges and also adjusting electronic processor parameters. The invention uses monolithic a/d converters with expanded capacity and a microcontroller/processor with a pulse control module to synchronize switching in an oversampling demodulator with pulsing of light sources to overcome prior circuitry limitations that consumed substantial central processor capacity.

Abstract: A system for disabling an oximetric device when radiation-carrying channels are exposed to excess ambient radiation is disclosed. It includes a transmitter channel adjacent the sample to be measured, means for isolating the channel from the sample so that it does not carry radiation reflected from or transmitted through the sample, a detector for receiving the transmitted signal, if any, and means for disabling the output in response to the transmitted signal. Preferably, the transmitter channel runs parallel to other transmitter channels in the device, and is isolated from undue ambient light. The system preferably includes means for determining when the second transmitted signal exceeds background noise and the output is disabled when the second transmitted signal exceeds background noise.

Abstract: A new warning system for informing an aircrew member undergoing high acceleration, or other brain oxygen-depleting environmental stressors, of the time remaining before fatigue sets in and the aircrew member will no longer be able to maintain straining maneuvers fighting the effects of high acceleration utilizes the new discovery that pilots and other aircrew members experience performance-ending fatigue at about the same percentage level of blood oxygen saturation. The particular percentage varies individually, but is nearly always the same for a single individual. The warning system uses a non-invasive monitor to measure blood oxygen saturation at different times and to compute from those measurements the amount of time remaining before the individual percentage blood oxygen saturation at which fatigue or exhaustion will occur for that individual will be reached. That remaining time is displayed to the aircrew member on an instrument panel display.

Abstract: A low cost, disposable oximetric sensor including a finger cot probe to facilitate either the transillumination or transreflectance and the detection of optical energy emitted towards a patient's finger without subjecting the finger to deformation. The finger is received within a receptacle having a cup-shaped closed end and an opposite open end that is rolled up upon itself and adapted to be unrolled longitudinally along the finger to form a tubular enclosure in surrounding engagement with the finger. An optical source and an optical detector are arranged in spaced axial alignment with one another at opposite sides of the finger so that optical energy transmitted by the source towards the finger is received by the detector for non-invasively indicating the saturation of oxygen within the patient's blood depending upon the magnitude of the optical energy detected.

Abstract: A measuring apparatus of the present invention measures the constituent concentration of a specimen after loading into the apparatus a test piece having a test material which develops coloring as a result of a reaction with the constituents of a specimen. When the apparatus detects that the test piece having the test material has been loaded, it automatically begins to measure the constituent concentration of the specimen. That is, after the loading of the test piece is detected, a predetermined time period is measured. During this time measurement, the time period is displayed at a predetermined time interval. After the time measurement of this predetermined time period is terminated, the test material is irradiated with a light, and the intensity of the light from the test material is detected. The constituent concentration of the specimen applied to the test material can be determined on the basis of the reflected light intensity thus detected.

Abstract: A fiber optic catheter for continuous measurement of central venous oxygen saturation (Scv02) during human cardiopulmonary arrest and shock. When applied in cardiopulmonary arrest (cardiac arrest), the catheter provides therapeutic and prognostic guidelines in the management of a patient in this condition. The catheter also serves as a conduit for fluid and drug infusion and as a sampling port for venous blood. The catheter comprises a body having a first port that exits through a connector body to the computer interface that provides the sending signal and receiving signal which generates central venous oxygen saturation readings. A fiberoptic bundle of afferent and efferent light-conducting fibers transverses the first port to provide signal generation and interpretation of oxygen measured in the blood. A second port is a lumen that traverses and exits at the distal port to allow for pressure measurement and sampling of the venous blood.

Abstract: A method and apparatus for monitoring glucose, ethyl alcohol and other blood constituents in a noninvasive manner. The measurements are made by monitoring infrared absorption of the desired blood constituent in the long infrared wavelength range where the blood constituent has a strong and distinguishable absorption spectrum. The long wavelength infrared energy is passed through a finger or other vascularized appendage and the measurement made. To prevent the high energy source from burning or causing patient discomfort, only short bursts or pulses of energy are sent through the finger with a very low duty cycle and low optical bandwidth. The bursts are further synchronized with systole and diastole of the cardiac cycle so that only two pulses are sent per heart beat, one during diastole and one during systole. The detection signals measured during application of these bursts of energy are then used to calculate the concentration of the blood constituents in accordance with a polynomial equation.

Abstract: An optical distribution system incorporating an improved luminescent based optical fiber sensor incorporating a signal generating component for generating a first optical signal, a signal separating component for delivering said first optical signal to the sensor, delivering said second returned optical signal to an associated signal detector, and including signal interference means to separate said first and second signals and minimize cross-talk therebetween. A sensor optical fiber connects a sensor tip to the signal separating component. The signal detector receives a returned signal from the signal separating component and transmits it to a signal-measuring component of the distribution system.

Abstract: A non-invasive eye oximeter which monitors the arteriovenous oxygen difference. The optic disc region of the ocular fundus is illuminated with three or more wavelengths of light focused in approximately the same area. One of the light sources serves as a tracking beam which, through reflectance spectrophotometry, is used to determine when the tracking light beam is focused upon the optic disc. The scanning light beams are primarily focused within the boundary of the tracking beam. The intensity of light reflected from retinal venules and arterioles is detected, and the arteriovenous oxygen difference is determined.

Abstract: A system (10) for in vivo measuring chemical and physical parameters of a patient's blood includes a probe (12), a sensing system (14), and flush interference warning devices (20). The system measures pH, pCO.sub.2, and temperature values, and determines a base excess value using the measured pH and pCO.sub.2. The time rate of change of the base excess value is also determined, as is the time rate of change of temperature. The warning devices are activated, indicating that the measured parameters are likely affected by the presence of flush solution flowing past the probe, when either: (a) the base excess value is less than a predefined threshold base excess; (b) the absolute value of the time rate of change of the base excess value is greater than a predefined threshold time rate of change of base excess; or, (c) the absolute value of the time rate of change of temperature is greater than a predefined threshold time rate of change of temperature.

Abstract: A system for measuring the saturation of at least one gas in blood has a sensor which is, intended to be placed on a living body. Light is emitted from the sensor and into the body at a light radiating zone. The sensor has a plurality of light receiving zones, serving to receive light backscattered in the body, which zones are at various distances from the light radiating zone. Light receiving means are also present, in order to measure the intensities of the light backscattered from the body and reaching the sensor in the various light receiving zones. The measuring system also has electronic circuitry, which upon measurement, based on a predetermined criterion, selects one evaluation zone from among the light receiving zones and evaluate the portion of the light detected in the evaluation range that varies periodically over time at the rate of the pulse frequency in order to detect at least one gas saturation of blood, in particular the oxygen saturation of blood.

Abstract: A method and system for controlling the intervals during which light signals are sampled in a fiber-optic sensing system compensates for signal artifacts that are caused by movement of the fiber-optic waveguide during the sampling. The method and system sample the light signals at intervals that are shorter than the intervals during which displacement of the optical waveguide occurs in normal use. The short-sampling intervals result in the individual sampling of different wavelengths of light being exposed to the same changes in transmission characteristics of the optical waveguide which causes signal artifacts. Accordingly, when subsequent processing of the collected signals occurs, the effects of the signal artifacts are compensated for.

Abstract: This arterial blood monitoring system takes advantage of the basic statistical property that arterial blood contains a plurality of dominant absorbers, whose measured light absorption spectra appear as a constant over a short interval of time. By measuring the transmitted light as it varies with arterial pulsation at selected wavelengths of light, over a common light path, the relative amount of these dominant absorbers in the arterial blood can noninvasively be determined. To ensure the common light path, a sandwich construction light detector is used.

Abstract: A method and apparatus for improving the calculation of oxygen saturation and other blood constituents by non-invasive pulse oximeters. The method and apparatus permit more accurate determination of blood flow by collecting time-measures of the absorption signal at two or more wavelengths and processing the collected time-measure to obtain composite pulsatile flow data from which artifacts have been filtered. The processing may occur in the time domain or in the frequency domain. In the preferred time domain embodiment, successive portions of periodic information are weighted and added together in synchrony to obtain the composite pulse information. In the preferred frequency domain embodiment, the time-measure is Fourier transformed into its spectral components to form the composite information.