Comparison of Delphin and BioMedicus pumps. There is an increasing use of centrifugal pump systems for cardiopulmonary bypass (CPB) and circulatory assistance. The BioMedicus and Delphin centrifugal pump systems were tested in two side-by-side, identical in vitro flow loops for blood trauma and flow probe accuracy. Blood parameters tested were hemoglobin, hematocrit, lactate dehydrogenase, free plasma hemoglobin, and platelet counts. The Delphin pump demonstrated significant increases in plasma hemoglobin levels at the three flow rates tested: 2 L/min (p less than 0.05), 4 L/min (p less than 0.005), and 6 L/min (p less than 0.05). After 4 hr of pumping, the drop in platelet counts was significantly greater in the BioMedicus loop as compared with the Delphin loop (p less than 0.05) at the 2 L/min and 4 L/min flow rates; however, platelet levels remained within normal ranges in both systems. At 6 L/min, no statistical difference in platelet counts was noted. The flow probe readings were found to deviate by as much as 58% of stopwatch timed flow rate comparisons at low flow rates, but improved to within 10% or better at 6 L/min. 