Bench-top evaluation of air flow through a valved peelable introducer sheath

Air embolism is a rare but potentially fatal complication that may occur during the insertion of a central venous catheter. A valved peelable introducer sheath was developed to reduce the likelihood of an air embolus. This study was performed to determine the rate of air flow through this valved introducer sheath under different conditions that may be encountered in a clinical setting.

A 16-F-diameter valved peelable introducer sheath was used for all experiments. A bench-top testing system was constructed that consisted of a vacuum source, a mass flow meter, and a digital vacuum gauge. A coupling device with a pneumatic O-ring was used to seal and connect the distal end of the introducer sheath to the testing system. A vacuum of -5 mm Hg was applied to the sealed distal end of the sheath to simulate physiologic conditions. The rate of air flow through the valved sheath was measured under three different conditions; (i) valve open, (ii) valve closed, and (iii) valve open but with the sheath manually pinched. Thirty air flow measurements were performed for each of the three test conditions.

When the valve was in the open position, the mean rate of air flow through the introducer sheath was 417.2 mL/sec (range, 415.5-419.7 mL/sec). When the valve was in the closed position, the mean rate of air flow was 0.004 mL/sec (range, 0.000-0.067 mL/sec). When the valve was open but the sheath was manually pinched, the mean rate of air flow through the sheath was 31.7 mL/sec (range, 23.0-38.8 mL/sec). During the 90 testing procedures, the mean vacuum was -5.10 mm Hg (range, -5.00 to -5.45 mm Hg).

This bench-top study revealed that a massive amount of air flowed through the open 16-F introducer sheath when it was subjected to a vacuum of -5 mm Hg, a situation that may occur under normal physiologic conditions. The rate of air flow could be decreased by aggressively pinching the sheath but the rate of air flow was still substantial. This study demonstrated that the addition of a sophisticated valve mechanism can essentially eliminate air flow through a peelable introducer sheath.