Abstract: A catheter hub assembly is disclosed wherein the assembly contains a membrane useful in preventing backflow of blood into the flash chamber. The hub assembly contains a membrane opener which operates upon the insertion of a luer locking mechanism into the catheter hub. This membrane opener allows flow of nutritional fluid into the body by causing the opening of the membrane during use of the catheter after removal of the catheter needle.

Abstract: A catheter is provided which deters the backflow of blood between the insertion needle and the catheter cannula by forming the distal end of the catheter hub so as to restrict the inner diameter of the catheter cannula to a wiping fit with the engaged insertion needle. In a first embodiment the distal end of the catheter hub is pre-formed to its desired final inner dimension. The distal end of the hub is stretched to an oversize condition, the catheter cannula is attached to the hub, and the distal end of the catheter hub is heated, causing a stress relief of the previously stretched hub. The distal end of the catheter hub returns to its pre-formed dimension which will mechanically restrict the diameter of the catheter cannula at that point to form the wiping fit with the engaged needle.