Abstract
The influence of vacuum-assisted venous return on the discharge characteristics of a roller pump was verified via water tests. Using the JIS method with a half inch inner diameter pump tube, the counter flow rates at the roller occlusion measured with a 100cmH2O load were 0.35-0.75mL/min(critical occlusion), 18mL/min(non-tight occlusion L), and 50mL/min(non-tight occlusion H), respectively. Under these conditions, a 20-100mmHg vacuum was applied at the venous reservoir. For non-tight occlusion H and with the pump stopped, a leak in the applied vacuum(approximately 25%)was confirmed at the exit side of the pump. With the pump operating at 100 RPM(no-load flow rate is approximately 4.2L/min)and critical occlusion, the flow rate decreased proportionally with vacuum and a 10% flow rate drop was observed at -100mmHg. For non-tight occlusion, the flow rate drop was not proportional with vacuum. At -20mmHg, the flow rate was approximately 2.3L/min for non-tight occlusion L, whereas for non-tight occlusion H, a minimum flow rate of 2.0L/min was observed. It is assumed that the flow rate drop was due to the vacuum reaching the pump intake area, thereby affecting the recovery of the occluded pump tube. Especially, for non-tight occlusion, the vacuum effect reaches the pump exit side as well, thereby causing a more pronounced flow rate drop. It has been determined that in order to obtain the accurate set flow rate, it is essential to adjust the critical occlusion. In addition, it appears necessary to measure the actual blood flow rate even when using a roller pump.
