Abstract: A method is disclosed for reliably calibrating a sensor used in diagnostic sensing of a predetermined parameter, e.g., CO.sub.2 partial pressure, O.sub.2 partial pressure, or pH, of a solution such as blood, the method compensating for expected variations over time in the value of the parameter in a calibration solution. The parameter of the calibration solution has a predetermined initial value, and the solution is initially located within a container that is configured to allow the value of that parameter to vary over time in a predetermined manner. Supplying the calibration solution to the sensor causes the sensor to produce a calibration solution signal, which is compared with a calculated value for the parameter based on its expected variation over time, to produce a calibration factor. Thereafter supplying the test fluid to the sensor causes the sensor produces a test fluid signal, and this test fluid signal then is adjusted in accordance with the calibration factor.

Abstract: An improved apparatus is disclosed for maintaining a medical assembly, e.g., a blood chemistry electrode assembly, filled with a bubble-free storage liquid for an extended storage time period. The apparatus achieves this result by connecting to the assembly a pressurized reservoir that supplies additional storage liquid, to replenish any storage liquid lost due to diffusion from the medical assembly.

Abstract: A method and apparatus for reducing the volume of fluid required to purge a patient's blood from a blood sampling site after the blood has been sampled for measurement. A coil is formed in the fluid flow line between the source of fluid and the blood sampling site by looping the fluid flow line around on itself in order to generate turbulence in the fluid flow to help purge the patient's blood from the blood sampling site after sampling. This turbulence-inducing coil is conveniently formed in a fluid flow line extending from the upstream end of a blood chemistry sensor module which is adapted to be installed in the fluid flow line of a standard IV infusion set as part of a combined infusion fluid delivery and blood chemistry monitoring system.

Abstract: An improved sensor apparatus of a kind that positions a semi-permeable membrane adjacent to an electrode assembly, for measuring a predetermined parameter, e.g., glucose concentration, of an adjacent fluid sample. A special compressible ring serves a first function of tensioning the membrane so that it is maintained in intimate contact with the electrode assembly, and it further serves a second function of sealing the fluid sample from the external environment.

Abstract: An improved electrode assembly is disclosed for use in assaying glucose in solution, e.g., in undiluted whole blood. The assembly includes a sensor electrode and a special overlaying multi-layer membrane that can be sterilized by gamma radiation without reducing the activity of a glucose oxidase enzyme located in an intermediate layer of the membrane. An outer layer of the membrane is formed with microscopic pores having a predetermined density and predetermined size, for reliably controlling the flux of glucose and oxygen from the solution to the intermediate layer, where they react in the presence of the glucose oxidase enzyme to form reactions products that include hydrogen peroxide. The outer layer thus functions as a diffusion barrier, to eliminate the adverse effects of any oxygen deficit that might be present. In addition, an inner layer of the membrane functions as an interference barrier, for controlling the permeation of the hydrogen peroxide reaction product to the underlying electrode.

Abstract: An improved system is disclosed for monitoring a patient's blood chemistry, wherein the system intermittently draws blood samples from the patient into a special sensor assembly having a plurality of analytical sensors, each sensitive to a particular parameter of the blood. After signals produced by these various sensors have been read, the system reinfuses the blood samples back into the patient. Withdrawal of the successive samples to a desired, optimal position within the sensor assembly is achieved by monitoring signals produced by one or more of the analytical sensors, themselves. This allows a catheter that connects the sensor assembly to the patient to have a variable length and internal volume and obviates the need for a separate, dedicated sensor for detecting the arrival of the blood sample at the desired position.

Abstract: Novel calibration solutions are provided which are useful, for example, with sensor assemblies used for analysis of CO.sub.2, and optionally, for concurrent analysis of O.sub.2, especially in combination infusion fluid delivery/blood chemistry analysis systems which include a sensor assembly with each of the assembly electrodes mounted in an electrode cavity in the assembly. The analysis system used in the practice of the present invention typically includes provision for delivering infusion fluid and measuring blood chemistry during reinfusion of the physiological fluid at approximately the same flow rates. The invention calibration solutions are useful for calibrating an array of sensors capable of simultaneously measuring a number of blood chemistry parameters, including the partial pressures (tensions) of carbon dioxide and oxygen, pH (hydrogen ion), sodium, potassium, ionized calcium, ionized magnesium, chloride, glucose, lactate and hematocrit, in body fluids.

Abstract: A method of using a multi-compartment fluid assembly for calibrating an apparatus external to the assembly, while conveniently maintaining sterility. The method includes providing calibration fluid in a closed calibration container disposed within a bag that includes a connector for conveying fluids between the interior of the bag and a conventional intravascular tube. In use, fluids may be directed through the external apparatus and the intravascular tube and into the bag's interior. At an appropriate time, the calibration container is opened and the calibration fluid is withdrawn from the container to the intravascular tube, through the connector, without mixing the calibration fluid with any fluids in a remaining volume of the bag. Subsequently, the calibration fluid is transferred from the intravascular tube to the bag's interior, again through the connector.

Abstract: Novel calibration solutions are provided which are useful, for example, with sensor assemblies used for analysis of CO.sub.2, especially in combination infusion fluid delivery/blood chemistry analysis systems which include a sensor assembly with each of the assembly electrodes mounted in an electrode cavity in the assembly. The analysis system used in the practice of the present invention typically includes provision for delivering infusion fluid and measuring blood chemistry during reinfusion of the physiological fluid at approximately the same flow rates. The invention calibration solutions are useful for calibrating an array of sensors capable of simultaneously measuring a number of blood chemistry parameters, including the partial pressures (tensions) of carbon dioxide and oxygen, pH (hydrogen ion), sodium, potassium, ionized calcium, ionized magnesium, chloride, glucose, lactate and hematocrit, in body fluids.

Abstract: This invention provides an electrochemical sensor capable of measuring the glucose level of body fluids, especially blood. More particularly, this invention also relates to the use of such a glucose sensor in an automated bedside blood chemistry system which facilitates the operation of the sensor.

Abstract: A system for electrically measuring certain chemical characteristics of electrically-conductive fluids, such as blood, located within a tube and subject to electrical current interference. The measurements are made by measuring the voltage potential between a reference electrode and a sensor electrode sensitive to a particular blood parameter such as pH or calcium, potassium or chloride concentration. A bypass path for the electrical current interference is provided by a pair of noise-reduction electrodes located on opposite sides of the reference and sensor electrodes and interconnected by an amplifier having a relatively low output impedance and a relatively high input impedance. The electrical current interference bypasses the signal electrodes by flowing directly into the amplifier's output terminal, such that the reference and sensor electrodes develop a potential between them that is independent of the electrical current interference.

Abstract: A sensor assembly for a combination infusion fluid delivery system and blood chemistry analysis system includes a sensor assembly with each of the assembly electrodes mounted in an electrode cavity in the assembly. Each electrode cavity includes a circular ridge that defines a cylindrical inner cavity and a ring-shaped outer cavity. The circular ridge prevents the water soluble gel from wicking into the surrounding selectively-permeable membrane, and thereby provides easier manufacture, higher yield rates, and longer shelf life. A helical groove increases turbulence in the assembly, reducing the purge volume needed to flush the assembly after each sample measurement. The system includes provision for delivering the infusion fluid and measuring blood chemistry during reinfusion of the blood at approximately the same flow rates.