Importance

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Abstract

A blood constituent processing system uses a disposable plastic fluid flow path into which an anticoagulant must be accurately metered with respect to pumped blood flow. In a preliminary calibration phase, a closed fluid flow path is provided between the anticoagulant pump and the blood pump. One of the pumps is then controlled to inject fluid into such closed path while the other pump is controlled to withdraw fluid from that path at what is nominally an equal fluid flow rate. Changes in fluid pressure within the closed fluid flow path are then monitored and the flow rate of at least one of the pumps is changed as necessary to achieve an approximately constant fluid pressure within the closed fluid flow path. The relative pump flow control required to achieve constant pressure may then be taken as a relative flow rate calibration between the two pumps so as to permit subsequent accurate pumped metering of anticoagulant into the pumped blood flow. A similar arrangement may be used to derive relative flow calibration constants for the blood pump and a packed cell pump also present in the blood constituent processing system.

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First Claim