Abstract: Access recirculation in a shunt is determined quantitatively by a method in which a standard solution, such as a saline, is injected into a patient's bloodstream upstream of the shunt. At a point in the access line, a photometric measurement is conducted of the change in hematocrit (&Dgr;H) with respect to time. Electronic circuitry receives signals from the detector and compares the integrated area of &Dgr;H with respect to time of the standard solution initially flowing through the access and of the recirculated solution and provides display of access recirculation. In another aspect, access recirculation and access blood flow are quantitatively determined without injecting a solution into the bloodstream. In this aspect the extent of access recirculation and/or access blood flow is determined quantitatively by a method in which the dialyzer blood flow rate or the ultrafiltration rate (UFR) is changed and the corresponding change in concentration of a blood constituent is measured.

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.

Abstract: Systems and methods are provided for noninvasively measuring the levels of urea, blood osmolarity (or Na+), plasma free hemoglobin and tissue water content in a patient's blood or tissue. Light of selected wavelengths is passed through blood or body tissue and the transmitted or reflected light is detected and the detected signals can be electronically compared and manipulated to provide the non-invasive, continuous and quantitative display of a patient's blood urea, blood osmolarity (or Na+), plasma free hemoglobin and tissue water content.

Abstract: A system for determining a biologic constituent including hematocrit transcutaneously, noninvasively and continuously. A finger clip assembly includes 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 one predetermined wavelength of light is passed onto or through body tissues such as a finger, earlobe, or scalp, etc. and attenuation of light at that wavelength is detected. Likewise, the change in blood flow is determined by various techniques including optical, pressure, piezo and strain gage methods. Mathematical manipulation of the detected values compensates for the effects of body tissue and fluid and determines the hematocrit value. If an additional wavelength of light is used which attenuates light substantially differently by oxyhemoglobin and reduced hemoglobin, then the blood oxygen saturation value, independent of hematocrit may be determined.

Abstract: Access recirculation in a shunt is determined quantitatively by a method in which a standard solution, such as a saline, is injected into a patient's bloodstream upstream of the shunt. At a point in the access line, a photometric measurement is conducted of the change in hematocrit (.DELTA.H) with respect to time. Electronic circuitry receives signals from the detector and compares the integrated area of .DELTA.H with respect to time of the standard solution initially flowing through the access and of the recirculated solution and provides display of access recirculation. In another aspect, access recirculation and access blood flow are quantitatively determined without injecting a solution into the bloodstream. In this aspect the extent of access recirculation and/or access blood flow is determined quantitatively by a method in which the dialyzer blood flow rate or the ultrafiltration rate (UFR) is changed and the corresponding change in concentration of a blood constituent is measured.

Abstract: A cuvette having a pedestal for transmitting light through a relatively thin layer of blood. While the pedestal enables the use of a small path length it also permits the use of a high volume and/or high flow rate conduit. The pedestal further enables methods of determining various blood parameters in which the path length, d, is fixed; i.e., there are little or no pulsatile variations. Hence, the flow-through cuvette accommodates a large range of blood flow rates without any reduction in accuracy of the hematocrit measurement. The pedestal, because of its elliptical shape, does not damage or hemolyze the individual red blood cells as they pass through. A quantitative method for determining changes in blood volume in view of the path length is provided along with a method for measuring a patient's cardiac output and oxygen consumption rate. Cardiac output is obtained by injecting a saline arterial bolus and a saline venous bolus into a patient and measuring the change in hematocrit caused by each bolus.

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: 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: A disposable cuvette through which to pass pulsatile flowing blood. The cuvette has a conduit with two opposed walls having a predetermined separation therebetween that varies with each pulse of the flowing blood. A sealed air pocket damps the variation of the predetermined separation. The conduit is comprised of materials which permit passage therethrough of wavelengths of selected electromagnetic radiation. The radiation is emitted from a photoemitter which, and after passing through the cuvette, is detected by a photodetector. The quantities of detected radiation are operated on by a computer which uses a spectrophotometry technique to derive therefrom a blood constituent concentration value. Preferably, both cuvette and spectrophotometry technique are used during hemodialysis to derive changes in the hematocrit value of the blood of a dialyzed patient, thereby to deduce therefrom changes in the blood volume of the patient during dialysis.

Abstract: A disposable cuvette through which to pass pulsatile flowing blood. The cuvette has a conduit with two opposed walls having a predetermined separation therebetween that varies with each pulse of the flowing blood. A sealed air pocket damps the variation of the predetermined separation. The conduit is comprised of materials which permit passage therethrough of wavelengths of selected electromagnetic radiation. The radiation is emitted from a photoemitter which, and after passing through the cuvette, is detected by a photodetector. The quantities of detected radiation are operated on by a computer which uses a spectrophotometry technique to derive therefrom a blood constituent concentration value. Preferably, both cuvette and spectrophotometry technique are used during hemodialysis to derive changes in the hematocrit value of the blood of a dialyzed patient, thereby to deduce therefrom changes in the blood volume of the patient during dialysis.