Patient controlled analgesia (PCA) device is known to be an effective method for acute and chronic pain control and the administration route for PCA pump is various. The representative routes are intravenous and epidural space. The aim of this study is to investigate the influence of catheter diameter on flow rate.

IV extension tube or epidural catheter connected to Mechanical- or balloon-type PCA devices were examined (100 ml, 2 ml/hr). There were four groups each of 5 experiments: Group I: Mechanical-type pump + IV extension tube, Group II: Mechanical-type pump + epidural catheter, Group III: Balloon-type pump + IV extension tube, Group IV: Balloon-type pump + epidural catheter. The flow rate was indirectly measured by the weight change of collecting infusate bottle. Infusion fluid was distilled water. Experiment was carried out in a laboratory room with a constant room temperature of 20-22℃.

Infusion rate differed significantly among the groups, exhibiting flow rates within ±15% of their expected rate for 28% (group IV) to 100% (group I) of their infusion duration. The mean Infusion rate in group I was significantly more rapid than that in other groups. The mean flow rate in group III was higher than that in group IV (P < 0.05).

These results indicate that the use of an epidural catheter with a small internal diameter could decrease the flow rate of PCA device.