Aerostasis during central venous access: Updates in protective sheaths

PURPOSE: Air emboli (AE) complicating central venous catheter (CVC) placement are rare but potentially fatal events. Building on earlier experience, the authors conducted in vitro testing of the aerostatic properties of newly designed protective sheaths. MATERIALS AND METHODS: The standard peel-away sheath, the previously studied sliding-valve sheath, and newer fixed-valve and double-valved sheaths were evaluated. Aerostatic stability of the sheaths was evaluated by measuring air flow into the model under standard and stressed conditions. In addition, volumes of AE created during simulated CVC insertion through the sheaths were determined. RESULTS: Under physiologic conditions, significantly smaller volumes of AE occurred with a pinch 2 inches from the sheath hub relative to a pinch at 1 inch. Sliding-, fixed-, and double-valve sheaths yielded leak rates of 0.05 ± 0.05 mL/sec, 0.06 ± 0.05 mL/sec, and 0.08 ± 0.07 mL/sec, respectively. Under stress, protective sheath leak rates increased to 1.8 ± 0.4 mL/sec, 1.6 ± 0.5 mL/sec, and 1.8 ± 0.4 mL/sec, respectively. Use of a double-valved sheath demonstrated no significant difference in leak rates under standard and stressed conditions. In most cases, protective sheaths yielded significantly smaller AE than control sheaths. In comparison of protective sheaths, AE volumes during CVC insertion for sliding-, fixed-, and double-valved sheaths were 22.8 ± 4.5 mL, 16.6 ± 7.3 mL, and 10.8 ± 4.5 mL, respectively. Double-valved sheaths yielded significantly smaller AE volumes than did sliding-valve sheaths (P < .01). CONCLUSIONS: In most standard situations, AE volumes and aerostatic stability of protective sheaths tested favorably in comparison with control sheaths. When some sheaths were stressed, their aerostatic properties failed. In a comparison of the three protective sheaths in standard and stressed conditions, the double-valved sheath fared better than the sliding and fixed-valve sheaths.