Particle spallation and plasticiser (DEHP) release from extracorporeal circuit tubing materials

Particle spallation and plasticiser (DEHP) release from medical grade polyvinylchloride (PVC), co-extruded PVC-polyurethane (PIVIPOL)R and an experimentally produced co-extruded PVC-ethylene vinyl acetate (EVA) has been studied when used with manually occluded and self-occluding peristaltic pumps over a six hour pumping period. The shore hardness of the tubings studied were similar but the luminal coating thickness differed (0.2 mm polyurethane, 0.99 mm EVA). The pattern of particle release was similar for all materials on the pump type used with the majority of particles released being less than 5 microns in diameter. The number of particles greater than 5 microns released was independent of the tubing material but depended on the pump type. Particle release with self-occluding pumps was significantly higher (p less than 0.001) than for the manually occluded pump. Scanning electron microscopy indicated that the particles released originate from the repeated compression and flexing of the insert during pumping which leads to material structural failure. The higher release observed in the case of self-occluding pumps is suggestive of over-occlusion by the springs utilised in the pump. DEHP release (ppm) over a six hour period while perfused at 300 ml/min was significantly reduced for co-extruded tubing (0.56 +/- 0.05 mg (PVC-polyurethane) and 0.12 +/- 0.04 mg (PVC-EVA) compared with PVC (0.74 +/- 0.05 mg).