On initiation of bypass using a centrifugal pump, full calculated flow was achieved with RPM close to maximum (3500RPM). After 10mins of bypass, maximum RPM failed to achieve full calculated flow and steady decline of flow was observed for 39mins. The nadir flow during this stage was 4L/min. During this period, arterial line (post membrane) pressures reduced as flow reduced. After the nadir flow was reached, flow began to increase with maximal RPM. After this period of 39 mins until the end of bypass (another 82mins), RPM was decreased and >calculated flow was achieved. Prior to weaning from bypass RPM were at 3150 with a flow of 6l/min. During the bypass arterial line pressures (post membrane) correlated with flow. Pre-membrane pressures were not recorded. All of the patient's parameters were maintained within desired thresholds (arterial blood gas values, venous saturations, mean arterial pressure, ACT>400, DO2) throughout bypass. The supplier was informed but the device not returned.