Investigation and quantification of the blood trauma caused by the combined dynamic forces experienced during cardiopulmonary bypass

Blood is exposed to various dynamic forces during cardiopulmonary bypass (CPB). Understanding the damaging nature of these forces is paramount for research and development of the CPB circuit. The object of this study was to identify the most damaging dynamic non-physiological forces and then quantify this damage. A series of in vitro experiments simulated the different combinations of dynamic forces experienced during CPB while damage to the blood was closely monitored. A combination of air interface (a) and negative pressure (P) caused the greatest rate of change in plasma Hb (deltap Hb) (4.94 x 10(-3) mg/dl/s) followed by negative pressure and then an air interface. Shear stresses, positive pressures, wall impact forces and a blood-nonendothelial surface caused the least damage (0.26 x 10(-3) mg/dl/s). An air interface showed no threshold value for blood damage, with the relationship between the size of the interface and the blood damage modelled by a second-order polynomial. However, negative pressure did exhibit a threshold value at -120 mm Hg, beyond which point there was a linear relationship. Investigating the reasons for the increased blood trauma caused by the low-pressure suction (LPS) system makes it clear how research into minimizing or completely avoiding certain forces must be the next step to advancing extracorporeal technology.