Penetration forces in cannulation of the dorsal veins of the hand: I. A comparison between polyurethane (Insyte®) and polytetrafluoroethylene (Venflon®) cannulae

The functional tip tapering design of peripheral venous cannulae (introducer steel needle + catheter) made of polyurethane (PUR-Instye) and polytetrafluoroethylene (PTFE-Venflon) was studied with 3 techniques: A) Scanning electron microscopy (SEM). B) Measurement of penetration forces in vitro through latex membranes and lamb skins with a tensile-compression apparatus (Instron-1122) at 1) the introducer steel-needle point, 2) the needle heel (the spot marking the passage from the point of the needle to its shaft). 3) the catheter top (i.e. the beginning of the plastic sheath), 4) the catheter tip, i.e. the beginning of the largest diameter of the plastic sheath, and 5) between the catheter tip and its hub (catheter friction). C) Two cannulae (one of each type for every subject were inserted at random into the dorsal veins of the left and right hand in 37 volunteers, and the penetration forces were measured with a force transducer. Results: A) The PUR-cannulae had a lancet-like appearance and a smoother transition at the catheter top, whilst the PTFE cannulae were arrow-like, cut back and had a less accentuated conical design. B) Penetration forces in vitro through latex membranes were 9-41 times lower (P less than 0.0001) than those through the large skins. The highest forces (mean +/- s.d.) registered in vitro (lamb skins) were 4.1 +/- 0.2 Newtons (N) with PUR-cannulae at the catheter tip, and 3.4 +/- 0.6 with the PTFE-cannulae at the catheter top (P less than 0.05). C).(ABSTRACT TRUNCATED AT 250 WORDS)