Banked blood microfiltration. I. Microfilter composed of five polyurethane foam layers with graded pore size.

Aggregates of amorphous material which develop with storage of banked blood may be a source of pulmonary microembolism in patients having massive transfusions. In order to remove such debris, blood microfilters have been developed and are in routine clinical use. This paper describes the evaluation of one such filter, the Bentley PF 127 model B, which is composed of five layers of polyurethane foam. The time of filtration as a function of the pressure applied, the number of particles removed, the observed changes in blood cells, and the results of scanning electron microscopy of the filter after filtration of human banked blood, are reported.