Abstract: An optical probe is presented for use in measuring pH and oxygen content in blood in a blood vessel within a living body. An elongated flexible optical fiber means is provided which has a proximal end and a distal end. The distal end is adapted to be inserted into a blood vessel. A membrane is secured to the distal end of the optical fiber and receives light from the distal end of the fiber and returns light therethrough to the proximal end. The membrane is constructed of hydrophilic porous material containing a pH sensitive dye. A plurality of microspheres are embedded in and carried by the membrane. These microspheres are constructed hydrophobic material and each carries a fluorescent dye quenchable with oxygen. Consequently, when light is supplied to the proximal end of the optical fiber, it is conveyed to the membrane. This causes the pH sensitive dye to react and light is conveyed through the optical fiber having an intensity level indicative of the pH level in the blood.

Abstract: In photoelectric apparatus such as a pulse oximeter for monitoring a parameter of the blood in a living organism, a dark current correction signal is applied to the input at the preamplifier. The correction signal is substantially equal in magnitude but opposite in sense to the photodetector output during dark intervals when the illumination means of the apparatus is disabled. Because dark current correction is accomplished at the input of the preamplifier, the preamplifier has substantially increased resistance to overloading caused by ambient light and hence may have higher gain.

Abstract: An image analyzing apparatus comprising a source of light for radiating a target object of interest, a measuring light of a first predetermined wavelength and at least one detecting light of a second predetermined wavelength different from the first predetermined wavelength, which detecting light is utilized to detect an optically disturbing component, a camera unit for forming a measured image of the target object radiated by the measuring light and a detected image of the target object radiated by the detecting light, and capable of generating output signals representative of the respective measured and detected images, a processor for deriving an interference equation descriptive of an interference given by the optically disturbing component, on the basis of the measured and detected images outputed from the camera unit, a computer for eliminating the optically disturbing component from the measured image on the basis of the interference equation, and a display device for providing a visual representation

Abstract: A probe apparatus for use with an optical oximeter is disclosed. A pair of light emitting diodes emit light of known narrow wavelengths through an appendage of a patient onto a photosensor. A resistor of coded known resistance is used to enable the oximeter to calculate the co-efficient of extinction of the wavelengths of the LEDs. The resistor, LEDs and photosensor are mounted on self-attaching hook and eye tape for mounting the probe onto the appendage of the patient. The probe is detachably wired to the oximeter, rendering the probe completely disposable. The oximeter is programmed at the factory to calculate the co-efficients of extinction of any LEDs which may be encountered in a series of disposable probes. From the co-efficients of extinction, the pulse rate and degree of arterial oxygen saturation is computed and displayed by the oximeter.

Abstract: A medical apparatus for detecting apnea, in particular, in infants and children. The apparatus measures oxygen saturation in the blood and relates the measurement to a normal condition. The relationship is employed to indicate apnea.

Abstract: A device is described for sensing oxygen, particularly for use in medical applications. The device includes an optical waveguide and an oxygen sensing medium disposed on the waveguide. The sensing medium fluoresces in response to light from a light source such that the intensity of fluorescence is dependent on the partial pressure of oxygen in the environment. The sensing medium includes an oxygen sensitive fluorescent dye in a matrix consisting of a plasticized polymer.

Abstract: The catheter tip fits into a cavity in the boot and is held gently (in the longitudinal direction) by a detent formed within the cavity. A calibration substance faces the tip in a mechanically and optically standardized calibration relationship, to reflect light from within the catheter back into the catheter. The calibration substance is held in constant, precise contact with the tip--but passively, not by springs or other longitudinally forcible devices but by close fit between the tip and the precision-molded internal surfaces of the cavity. In the lateral direction the boot may tightly grip the tip, at a point where the optic fibers are protected against such force. To provide a reflection standard for calibration, the calibration substance is of standardized character and quality: it is preferably a homogeneous suspension of reflecting particles in translucent or transparent polymer.

Abstract: An oximeter for measuring oxygen saturation in arterial blood includes a light source for projecting light to a body member to be measured, a light responsive circuit for receiving the light which has transmitted through said body member and for generating at least first, second and third signals at three different wavelengths, and a calculator for calculating at least first SaO.sub.2 data using first and second signals and second SaO.sub.2 data using first and third signals. It is detected whether or not a difference between the first and second SaO.sub.2 data is within a predetermined level. When the difference is within the predetermined level, it is assumed that the first and/or second SaO.sub.2 data are valid, but if not, they are assumed as invalid.

Abstract: A probe apparatus for use with an optical oximeter is disclosed. A pair of light emitting diodes emit light of known narrow wavelengths through an appendage of a patient onto a photosensor. A resistor of coded known resistance is used to enable the oximeter to calculate the co-efficient of extinction of the wavelengths of the LEDs. The resistor, LEDs and photosensor are mounted on self-attaching hook and eye tape for mounting the probe onto the appendage of the patient. The probe is detachably wired to the oximeter, rendering the probe completely disposable. The oximeter is programmed at the factory to calculate the co-efficients of extinction of any LEDs which may be encountered in a series of disposable probes. From the co-efficients of extinction, the pulse rate and degree of arterial oxygen saturation is computed and displayed by the oximeter.

Abstract: Apparatus for the in-vivo measurement of blood oxygen levels in a patient, includingan elongate probe adapted to pass into the oesophagus of the patient,a fibre optic light channel for illuminating the internal surface of the oesophagusa photosensor for monitoring light reflected from the internal surface of the oesophagusand a signal processor for determining from the reflected light signal the degree of oxygenation of blood in the internal surface of the oesophagus.A single optical fibre light channel may be utilized both to conduct light into the probe to illuminate the internal surface of the oesophagus, and to conduct light reflected from the internal surface of the oesophagus to the exterior of the patient.

Abstract: A noninvasive device for photoelectrically measuring a property of arterial blood is provided. Light that contacts living tissue with arterial blood is converted into a pair of electrical signals. The electrical signals are processed to provide information of the amplitude of the measured signals and are further processed to produce a final output signal that is substantially a square function of a ratio between the electrical signals representative of the amplitudes.

Abstract: An optical module couples a fiberoptic catheter to a catheter oximeter processing apparatus. The module includes a plurality of LED's for coupling the electrical control signals from the processor and converting them to light signals to transmit to the catheter. The module also includes the means to convert the received reflected light signals from the catheter to electrical signals to be transmitted to the processor. The module further includes a memory to store calibration signals and other data so that the module and catheter can be disconnected from the processor and used with a different processor without necessitating a recalibration.

Abstract: Accurate in vivo measurement of blood oxygen saturation by fiberoptical means is made possible throughout a wide range of hematocrit or total hemoglobin values by using a single R/IR ratio I and calculating the SO.sub.2 value therefrom through the use of a second-order polynomial of the formSO.sub.2 =Ak.sup.2 I.sup.2 +BkI+Cin which A, B and C are hematocrit or total hemoglobin-dependent coefficients. These values may be contained in a lookup table accessed by a hematocrit or total hemoglobin value selection, and k is a purely multiplicative calibration constant which can be readily determined for any individual fiberoptic system.

Abstract: A calibrating device for an optical catheter is provided in order to calibrate the catheter for use in a catheter oximeter system. The calibrating device includes a tube having a reference block therein which is spring-loaded into compliant engagement with the distal end of the catheter carrying the fiberoptic light transmitting and receiving guides. A releasable strap tightly secures the catheter to the calibrating device. The packaged catheter is therefore ready for calibration by simply removing the proximal end thereof from a sealed package while the calibrating device and major length of the catheter remain in their sealed and sterilized condition and connecting it to a processor for performing the calibration operation.

Abstract: A catheter oximeter includes a fiber optic catheter for supplying radiation to blood under test at a plurality of wavelengths and detecting the intensities of the radiation back-scattered from the blood at each of the wavelengths. The oxygen saturation level of the blood is then computed by deriving it with a formula which uses the ratio of one pair of intensity signals when the oxygen saturation level is relatively low and with a formula which uses the ratio of another pair of intensity signals when the oxygen saturation level relatively is high.

Abstract: A probe apparatus for use with an optical oximeter is disclosed. A pair of light emitting diodes emit light of known narrow wavelengths through an appendage of a patient onto a photosensor. A resistor of coded known resistance is used to enable the oximeter to calculate the co-efficient of extinction of the wavelengths of the LEDs. The resistor, LEDs and photosensor are mounted on self-attaching hook and eye tape for mounting the probe onto the appendage of the patient. The probe is detachably wired to the oximeter, rendering the probe completely disposable. The oximeter is programmed at the factory to calculate the co-efficients of extinction of any LEDs which may be encountered in a series of disposable probes. From the co-efficients of extinction, the pulse rate and degree of arterial oxygen saturation is computed and displayed by the oximeter.

Abstract: A monitor system for an oximeter that sequentially tests the operative conditions of light emitting devices of the oximeter, the light detector of the oximeter, and the reference voltage of the oximeter. Data processing means is responsive to the determined test values for indicating the occurrence of the test values outside of predetermined ranges corresponding to the respective test value.

Abstract: In an instrument for spectral measurement in the bloodstream, the light-guide probe is developed with a diameter of, at most, 0.5 mm. By plug connections with precisely defined positions of the light guides, the light guide probe is connected to an illuminating device having a xenon lamp and to a diode line spectrometer. The diode line spectrometer has an aperture ratio which includes the aperture of the light guide without trimming or vignetting.

Abstract: A noninvasive device for photoelectrically measuring a property of arterial blood is provided. Light that contacts living tissue with arterial blood is converted into a pair of electrical signals. The electrical signals are processed to provide information of the amplitude of the measured signals and are further processed to produce a final output signal that is substantially a square function of a ratio between the electrical signals representative of the amplitudes.

Abstract: A signal filter method and apparatus for removing portions of a signal indicative of erroneous data, an exemplary apparatus including means for receiving the signal, means for adjusting a threshold by increasing the threshold a first predetermined amount when the signal is in a predetermined relationship with the threshold and for decreasing the threshold a second predetermined amount when the signal is in a second predetermined relationship with the threshold, and means for comparing the signal with the adjusted threshold and for transmitting the signal if the signal bears a first predetermined relationship to the threshold. Disclosed herein are digital and analog implementations of the signal filter method and apparatus, particularly suited for use with catheter-type oximeter apparatus.

Abstract: A method and apparatus is disclosed for continuously monitoring hemoglobin saturation in the blood of premature infants. A substantial portion of the eye fundus is illuminated by passing at least two frequencies of light through the pupillary opening. The light scattered from the fundus is collected as it passes out through the pupillary opening and its intensity is measured. Calculations known in the art are used to determine blood hemoglobin based on the intensity of the scattered light. A contact lens with associated fiber optic links is used to illuminate the infant eye and to collect the scattered light.

Abstract: A fiber optic probe to be implanted in human body tissue for physiologic studies involving measurement and monitoring of the partial pressure of gaseous oxygen in the blood stream, which is coursing through a particular blood vessel in the body. The use of the probe is based on the principle of dye fluorescence oxygen quenching. Structurally the probe comprises two 150-micrometer strands of plastic optical fiber ending in a section of porous polymer tubing serving as a jacket or envelope for the fibers. The tubing is packed with a suitable fluorescent light-excitable dye placed on a porous adsorptive particulate polymeric support. The tubing or jacket is usually made of a hydrophobic, gas-permeable commercial material, known as Celgard, but other suitable hydrophobic gas-permeable material could be used for such structure.

Abstract: For plotting an equilibrium curve representative of the relation between the oxygen saturation value of a hemoglobin sample, such as blood, and a changing oxygen partial pressure level in a gas, the sample is initially oxygenated by an oxygen-containing gas till it is completely saturated with oxygen, and thereafter by a controlled supply of deoxygenating gas to the volume of gas acting on the sample the oxygen partial pressure is decreased in a controlled manner. The oxygen saturation value is determined from the photometrically measured light absorption parameter of the sample in the measuring space.

Abstract: Apparatus employing a non-invasive method for objectively determining in vivo, the rate of oxygen utilization in peripheral tissue by spectral measuring means, containing a light source, a clamp or tourniquet for occluding a segment of blood in the tissue, means for transmitting the light through the isolated segment of blood to pick up the spectral values of the oxyhemoglobin for two selected wavelengths, wherein the rate of reduction of the oxyhemoglobin of the blood as determined at one wavelength is faster that the rate of reduction of the oxyhemoglobin at the other wavelength, means for converting the spectral values individually for the two selected wavelengths into current flow, and means for determining the time-space relationship between the changing spectral values of the two selected wavelengths, from the moment of occlusion.

Abstract: An optical analyzer such as oximeter is provided including a source of light having a plurality of different wavelengths. At least two or more of the different wavelengths have a fixed relationship of light absorption after coaction with hemoglobin oxide. The light is directed at the subject tissue and received after coaction by an optical probe. A first signal representative of the degree of light absorption at a predetermined standard wavelength is determined and then an attempt is made to match a second wavelength having a fixed relationship of light absorption to the predetermined standard wavelength, e.g., equal absorption, to generate a second signal representative of the second wavelength, whereby the amount of hemoglobin oxide can be determined in the bloodstream.

Abstract: A device and method for measuring blood characteristics and parameters, especially arterial, venous, or differential blood oxygen saturation levels uses one or two probes containing a unique configuration of light emitters of two different wavelengths, and sensors which alternately illuminate and read reflected light from blood passing through a specially-designed cuvette. Electronic comparison of reflected radiation received by the probes produces a voltage which is linearly related to blood oxygen saturation level. An opto-electronic feedback network compensates for differences in blood optical density.

Abstract: A device and method for measuring blood characteristics and parameters, especially arterial, venous, or differential blood oxygen saturation levels uses one or two probes containing a unique configuration of light emitters of two different wavelengths, and sensors which alternately illuminate and read reflected light from blood passing through a specially-designed cuvette. Electronic comparison of reflected radiation received by the probes produces a voltage which is linearly related to blood oxygen saturation level. An opto-electronic feedback network compensates for differences in blood optical density.

Abstract: Catheter apparatus having transmitting and receiving optical fibers for photometric analysis of a fluid eliminates the need for individually calibrating each catheter within a population of catheters by making substantially uniform the center-to-center spacing between the outlet aperture of each and every transmitting fiber and the inlet aperture of each and every receiving fiber of an individual catheter for all catheters within a population of catheters; and by making the size and shape of all the outlet apertures of all transmitting fibers generally uniform and the size and shape of the inlet apertures of all receiving fibers generally uniform in each catheter and from catheter to catheter and that the orientation of all transmitting fibers relative to all receiving fibers be similar.

Abstract: An improved cuvette unit suitable for use in blood oxygen analyzing and plotting apparatus in accordance with U.S. Pat. No. 4,304,488. A cuvette cavity, preferably cylindrical, is formed in a transparent plastic block. A Clark electrode is embedded in said block and arranged to project into the interior of the cavity. A horizontally-directed gas inlet is introduced adjacent the bottom of the cavity, for introducing the gas (oxygen, or an inert gas) and also providing efficient agitation. Among the benefits are the avoidance of mechanical agitation elements and the speeding up of the oxygen association and dissociation tests.

Abstract: A non-invasive blood constituent measuring device and method are disclosed for measuring changes in blood thickness of predetermined blood constituents relative to total change in blood thickness at a test area to thereby determine the concentration of such constituents in the blood in a living body, which measured constituents may be, for example, hemoglobin and oxyhemoglobin to enable determination of oxygen saturation of blood. The device includes a plurality of light emitting diodes operationally controlled by timing circuitry for sequentially emitting light at different predetermined wavelengths toward a blood containing tissue sample, such as an ear lobe.

Abstract: A compact, portable, clinical instrument dedicated to hemoglobin determination employs an L.E.D. light source with a peak output wavelength of about 553 nanometers and a yellow-blocking filter with a long wavelength cut-off not longer than about 565 nanometers. Thus, the relative amount of energy incident upon the blood sample in the 540 nm. hemoglobin absorption band is maximized. In addition to the L.E.D., the photodetector and the amplifying, inverting, log conversion, digital conversion, display and power supply regulation circuits are also exclusively solid-state. The display is of the reflective or liquid crystal type, and the power supply regulator is a sophisticated integrated circuit containing the equivalent of many discrete components. As a result, current consumption is minimized, and battery life and instrument accuracy are maximized. As an alternative illumination source, an infra-red L.E.D. can be employed, and the instrument is then capable of blood turbidity measurement.

Abstract: An optical scattering reference medium is formed of a plurality of scattering particles substantially uniformly dispersed in a substantially compliant, non-compressable transparent solid medium which is selectively positionable against the distal end of an optical catheter for use therewith within a sterilizable disposable package for performing repeatable photometric measurements to standardize the performance of the photometric measuring instrument.

Abstract: An eye fundus oximeter adapted to measure spectrally the oxygen saturation of the blood in the fundus of the human eye. The oximeter includes an illuminating optical system (8, 21, 10) for first illuminating the fundus of the patient's eye (11) with light of a wide wavelength range and then illuminating the same with light of four different spectra, a photoelectric element (13) for receiving the four kinds of light directly and not via the patient's eye and a photoelectric element (16) for receiving the four kinds of light impringing on the fundus of the eye and then reflected therefrom. The outputs of these photoelectric elements (13, 16) are compared at each of the same spectra, the results of such comparison being subject to given arithmetic operations to evaluate the oxygen saturation.

Abstract: A method and system for measuring the oxygen carrying capacity of normal and abnormal hemoglobins and red cells under controlled pH, ionic strength, temperature and gas conditions is described. A blood sample and a physiologically balanced medium are placed in a cuvette and means are associated therewith for measuring the fractional saturation of the sample and the partial pressure of the oxygen (sometimes referred to as the oxygen tension) and provide output signals to an X-Y plotter for continuous recording. Preferably, means for maintaining the temperature of the medium and the blood sample is provided.

Abstract: Catheter apparatus having transmitting and receiving optical fibers for photometric analysis of a fluid eliminates the need for individually calibrating each catheter within a population of catheters by making substantially uniform the center-to-center spacing between the outlet aperture of each and every transmitting fiber and the inlet aperture of each and every receiving fiber of an individual catheter for all catheters within a population of catheters; and by making the size and shape of all the outlet apertures of all transmitting fibers generally uniform and the size and shape of the inlet apertures of all receiving fibers generally uniform in each catheter and from catheter to catheter and that the orientation of all transmitting fibers relative to all receiving fibers be similar.

Abstract: A spectral photometer emits light towards an object of interest, receives e light reflected back from the object of interest, and includes a timer or synchronizer operative for causing the spectral photometer to produce an output signal whose successive values correspond to the intensity of the spectrum derived from the object of interest at successive wavelengths. The spectral photometer output signal is applied to an oscilloscope for display of the thusly generated spectrum. The oscilloscope screen is provided with interpretation marks at characteristic points of the displayed spectrum, either by providing such marks on a transparent plate mounted in front of the screen, or by applying to the oscilloscope signals causing the scope itself to generate these marks. These marks may be curves shaped and located to be intersected by both maxima of an oxygenated-hemoglobin spectrum irrespective of the degree of oxygenation.

Abstract: A digital oximeter for noninvasively measuring oxygen saturation of the arterial blood is provided. Photoelectric transducers measure the light intensity after passing through living tissue to produce at least a pair of output signals of different wavelengths of light. A sample hold circuit is provided for correspondingly storing each of the respective output signals. A microprocessor controlled pulse activates a subsequent subtraction step between a second measurement taken for each of the respective wavelengths to correspondingly produce at least a first and second subtraction output. The circuit can then process at least the first and second stored light outputs and the first and second subtraction outputs to indicate the oxygen saturation.

Abstract: Electrochemical process and apparatus to control the chemical state of a material, that is, to cause said material to retain desired characteristics in an environment that normally would cause a change in those characteristics or to cause a material that has deteriorated from a desired chemical state to revert to the desired state.

Abstract: A mechanism for carrying a calibration standard and receiving a cuvette containing a blood sample to be tested is disclosed. The mechanism permits convenient shifting to either the test position or calibration position.

Abstract: A non-invasive method of objectively determining, in vivo, the rate of oxygen utilization in peripheral tissue by spectral measuring means, which involves isolating a segment of blood in the tissue with a clamp or tourniquet, and obtaining rapid, successive spectral curves of the oxyhemoglobin in the occluded area, to and from selected wavelengths of light, and measuring the time-space relationship between a rapidly moving portion of the spectral curve and a slower moving adjacent portion of the same curve, from the moment of occlusion, to establish a rate of reduction of the oxyhemoglobin in the tissue which is directly correlated to the rate of oxygen utilization.

Abstract: Monochromatic excitation light is passed into an indicator chamber to exc the indicator therein. The side of the indicator chamber in contact with the substance to be analyzed is closed off by a membrane which is permeable to the component of that substance whose concentration is to be determined. The side through which the radiation emitted from the indicator towards the light-measuring unit of the apparatus passes is transmissive for the emitted radiation. The direction of introduction of monochromatic excitation radiation, and the direction in which the radiation emitted from the indicator towards the light-measuring unit, include an angle relative to each other, and are preferably perpendicular.

Abstract: Light of two different wavelengths is passed through or reflected from a member of the body so as to be modulated by the pulsatile blood flow therein. The amplitudes of the alternating current components of the logarithms of the respective light modulations are compared by taking their molecular extinction coefficients into account so as to yield the degree of oxygen saturation. By adding a third wavelength of light, the percentage of other absorbers in the blood stream such as a dye or carboxyhemoglobin can be measured. Fixed absorbers reduce the amount of light that passes through or is reflected from the body member by a constant amount and so have no effect on the amplitudes of the alternating current components that are used in making the measurements.

Abstract: Process and apparatus to control the chemical state of a material. Bulk control of the chemical state of such material which permits maintenance of chemicals including enzymes by both restoration and stabilization. Optical and electrical power sources act in the presence of chemical mediators to control the rate of charge transfer to substances including metals contained in proteins, for example. Controlled charge transfer to the proteins enables construction of devices including small molecule detectors, e.g., electrically restored ferrous deoxyhemoglobin in a discrete component electrooptical circuit to monitor, for example, oxygen and carbon monoxide partial pressures. Restoration of chemical activity in molecules which have deteriorated enables construction of chemical reactors composed of stabilized catalysts and enzymes, e.g., restored functional nitrogenase in solar energy conversion devices which evolve molecular hydrogen or in chemical reactors which convert molecular nitrogen into ammonia.

Abstract: An improved catheter oximeter operates on radiation at three or more different wavelengths applied to and scattered back from blood under test to provide an indication of oxygen saturation and is considerably less sensitive to accuracy-degrading variations in the blood and its environment and in the oximeter measuring system.

Abstract: A perfusion meter comprising a hand-held battery operated optical plethysmograph displays an indication of blood flow rate in response to the time-varying optical transmission characteristics of an ear or other organ. This indication, called the perfusion index, is proportional to both the amplitude and frequency of variations in the dynamic optical transmission characteristics of the ear or other organ.

Abstract: The invention relates to a non-invasive oximetry process for determining the value of oxygen saturation of the blood of a subject. In some ear oximetry processes, light at two or more frequencies is transmitted through the ear lobe or pinna of the ear of a subject, and the intensity of the transmitted light is measured on the other side of the ear lobe. These processes are affected by such variables as depth of blood in the ear lobe or pinna and differences in the total hemoglobin concentration in the blood. Applicant has discovered that inaccuracies caused by these variables can be eliminated or greatly reduced by taking the derivative of the intensity of the transmitted light, and processing the values of these derivatives in association with a set of predetermined pseudo coefficients by applying these to newly developed relationships disclosed in the specification. The result of such processing yields the value of oxygen saturation of the blood of the subject.

Abstract: An apparatus and method for deriving an oxygen association curve for a blood sample wherein the sample is placed on a transparent support and is covered by a gas-permeable membrane element. The support is mounted in a gas treatment chamber with transparent windows on opposite sides of the support to provide an optical path through the support normal to the sample. Radiant energy is directed along this optical path, said radiant energy including two light frequencies, one having a wavelength at which there is substantially no change in absorbance as between oxygenated and deoxygenated blood and the other having a wavelength at which there is a relatively large change in absorbance as between oxygenated and deoxygenated blood. A controlled source of deoxygenating gas, such as nitrogen, and a controlled source of oxygen are connected to the chamber. An oxygen electrode is mounted in the chamber and generates the X component, corresponding to oxygen in the chamber, in an X-Y recorder.

Abstract: An apparatus for incubating and analyzing blood samples while the samples are measured for oxygen association. The apparatus includes a controlled atmosphere chamber in which humidity, temperature and carbon dioxide may be maintained at a predetermined level while the level of oxygen concentration is varied. The samples are received in an apparatus which includes at least two slides having pockets therein for receiving the samples. The slides are arranged so that the specimens may be inserted in the holders, indexed to desired positions within the chamber for incubation and analysis, respectively, and removed from the chamber without affecting the controlled atmosphere within the chamber.

Abstract: A flexible fiber optic probe or catheter insertable into the cardiovasular system for monitoring blood oxygen saturation or the like is provided with an improved standard for the calibration of the catheter and its associated electro-optic equipment. The improved calibration standard is particularly suited for catheters of very small diameter, is provided by a generally tubular reflecting member aligned with and adjacent to the distal end of the catheter. The reflecting member may be vinyl tubing or the like which may be removably of fixedly positioned about the distal end of the catheter to reflect light directed thereon from the catheter when in air or a clear sterile solution for calibration.

Abstract: A method and apparatus for deriving an oxygen association .[.rate.]. curve for a blood sample wherein the sample is introduced into a transparent-walled cell and is deoxygenated by contact with a deoxygenated fluorocarbon material. The cell is located in the optical path of two time-shared respective monochromatic beams, one having a wavelength at which there is substantially no change in absorbance as between oxygenated and deoxygenated blood and the other having a wavelength at which there is a relatively large change in absorbance as between oxygenated and deoxygenated blood. The difference in absorbance through the cell of the two wavelengths is measured and recorded while oxygenated fluorocarbon titrant material is pumped through the cell, the cell having a restricted flow passage for the titrant material which acts to separate the blood therefrom and retain it in the cell while the titration is taking place.