The effects of protein, red blood cells and whole blood on PS valve function

We tested the performance of low- and medium-pressure PS flow control valves as they were perfused with (1) solutions with varying concentrations of protein, (2) solutions with varying numbers of red blood cells (RBC) or (3) solutions with varying concentrations of whole blood. Perfusion was performed with a peristaltic pump at a constant rate and each trial lasted 2 weeks or until valve failure. Mean valve pressures were measured and recorded electronically, and opening and closing pressures were obtained at baseline and at the end of the perfusion period or upon valve failure. Any buildup of material within the valve was noted and recorded. Our findings were as follows: (1) protein levels have little practical effect on valve function; (2) moderate numbers of RBC cause increased variability in valve function while large numbers of RBC uniformly lead to valve failure; (3) prolonged perfusion with solutions of dilute whole blood is poorly tolerated, and (4) valve failure is preceded by a period of increased variability in perfusion pressure.