An apparatus and method are provided for measuring hematocrit. A diluted blood sample is passed through a well-known conductivity sensor providing a sensor pulse for each sensed blood cell. Each pulse has a peak amplitude corresponding to the size of a blood cell passing through the sensor. During a first time period initiated by passing of the sensor pulse above a threshold level, the sensor pulse is coupled to peak detecting means, and a signal indicative of the level of the peak is generated and stored. The value of each stored signal is added to an integrator for a fixed period of time. The value stored by the integrator is thus indicative of hematocrit level for a known sample volume.
A method and apparatus for measuring resistance of a blood sample in order to determine the hematocrit of that blood sample. The present invention makes a direct ratiometric measurement. That is, the alternating current that flows through the sample is directly measured by applying that alternating current to an integrator which converts the current to a D.C. voltage which is directly proportional to the applied current.
In a hematology parameter measuring apparatus, signals indicative of measured parameters are obtained and loaded into first digital registers. Calculated parameter values are generated through use of the values stored in the digital registers. A first parameter value is circulated from a register into a digital divider through a digital data line to set a divisor in the divider. A control circuit circulates a value from another register to the divider for utilization as a signal indicative of a dividend. The output of the divider is coupled to a result register to store a value indicative of the calculated parameter. In this manner, calculated parameter values are obtained, and the first registers retain values indicative of the measured parameter values. The control means may selectively couple signals to a display from any of the registers or to a printing unit.
A process and an apparatus for monitoring the progress of haemodialysis by extra-corporeal measurement of the haematocrit are presented. The process comprises the steps of: calculating at a given time the variation of a function of the haematocrit over a short period, on the one hand, and over a medium period preceding this time, on the other, comparing the values of these variations, the result of this comparison is a first indicator of the progress of the haemodialysis.
A biosensor and method for determining the hematocrit level of a whole blood sample using electrochemistry. The biosensor includes working and counter electrodes. A porous membrane is impregnated with an electroactive compound and is spatially displaced from the surface of the electrodes. When a whole blood sample is applied to the porous substrate, a mixture of the electroactive compound and the blood is formed. The mixture settles on the electrodes and a potential difference is applied sufficient to oxidize or reduce the electroactive compound and generate a current. This current can be measured and correlated to hematocrit level.
A conductivity sensor for measuring hematocrit and a sensor housing for a blood analysis instrument using the conductivity sensor are described. The conductivity sensor includes a seven-electrode conductivity measurement cell in which three symmetric pairs of electrodes are arranged on opposite sides of a central electrode. The central electrode is connected to an AC source and the outermost pair of electrodes, which provide a return path for the current, are maintained at a ground or reference potential. The two inner pairs of electrodes measure the voltage drop along the current flow path. This arrangement confines the measurement current and potential within the sensor chamber, thereby preventing the sensor from interfering with other electrochemical sensors that may be provided in the blood analysis instrument. The sensor housing provides a linear arrangement of flow cells defining a fluid flow path through the housing. The conductivity and other sensors are each located within an associated cell to form a wall portion of the flow path. The housing arrangement is simple to assemble and provides a flow path which resists fouling and is readily flushed out.
