System and method for collecting plasma

What is this patent about?

’652 is related to the field of blood apheresis and automated plasma collection. Specifically, it addresses the technical challenge of accurately measuring the actual volume of plasma harvested from a donor during a procedure where the collected product is inherently diluted by anticoagulant fluids.

The underlying idea behind ’652 is that the volume of pure plasma in a collection container can be mathematically isolated from the total fluid volume by accounting for the donor's hematocrit and the specific amount of anticoagulant metered into the system. Because anticoagulant does not penetrate red blood cells due to their osmolarity, it remains almost entirely in the plasma fraction, allowing the system to calculate a precise dilution ratio and stop the collection only when a true target volume of plasma is reached.

The claims of ’652 focus on a method and system that dynamically calculate the volume of pure plasma as it is being collected. This is achieved by determining the donor's weight and hematocrit, introducing a controlled amount of anticoagulant into the withdrawn blood, and using a controller to subtract the calculated volume of anticoagulant from the total collected fluid in real-time to ensure the procedure continues until a specific, pure plasma threshold is met.

In practice, the system utilizes a centrifugal bowl to separate whole blood into its constituent parts while sensors monitor the process. The controller tracks the anticoagulant volume by either monitoring the rotations of a metering pump or measuring the weight loss of the anticoagulant source container. Simultaneously, a weight sensor on the plasma collection bag provides the total mass of the mixture, which the system then processes using the donor's hematocrit to determine the exact moment the target yield is achieved.

This approach differs from prior solutions that typically stop collection based on the total volume of the plasma-anticoagulant mixture. By failing to account for the variable dilution caused by different donor hematocrit levels, prior systems often under-collect plasma from donors with high red blood cell counts. The invention optimizes the yield for every donor, ensuring that the maximum allowable pure plasma volume is harvested according to regulatory guidelines without exceeding safety limits.