December 22, 2016 | Posted in Patient Safety | By

Neutral needle-free connector logo

Until a few years ago, the prevailing view was that a neutral needle-free connector was impossible to achieve. Consequently, many medical device manufacturers promoted positive displacement as the best approach for preventing blood reflux into an IV catheter. However, in the last few years, neutral connectors have become a reality, and now a neutral needle-free connector with no blood reflux is the preferred technology1.

But how close to “true neutral” — or zero displacement — do commercial needle-free connectors actually get? NP Medical has proven that the neutral connector is possible, reliable, easy to use and safe. But we have also demonstrated that not all neutral connectors have the same performance. In other words, “neutral” is relative. I want to share the results of an in vitro study that NP Medical conducted in 2013. The study involved four commercially available needle-free connectors that are advertised as neutral displacement, including NP Medical’s
nPulse™ Neutral Connector.

The other three were the InVision-Plus® Neutral®from RyMed Technologies, the MicroCLAVE® Clear Connector from ICU Medical, and the One-Link Needle-free IV Connector from Baxter.

Graph depicting neutral displacement with needle-free connector
We procured thirty (30) randomly selected samples of each brand from commercial distribution. The study examined displacement upon disconnection of a Luer device, specifically a Luer lock syringe. The study protocol eliminated handling “noise,” such as squeezing the syringe barrel, to ensure that the displacement was truly a function of connector performance. The connection and disconnection procedure was repeated 30 times, providing a total of 30 data points for each brand.
The table below shows the results. As you can see, the average displacement for each brand is notably different, with all brands exhibiting negative displacement except for the nPulse™ Neutral Connector.

Achieving neutral displacement is, in reality, an engineering feat. Actually, it requires a combination of advanced engineering design, and high-precision manufacturing processes— the latter is especially important for consistent performance in high volume production.

1Jarvis W., MD. Choosing the Best Design for Intravenous Needleless Connectors to Prevent Bloodstream Infections. Infection Control Today, July 2010,
2 For an in vivo correlation, -2 microliters of blood reflux within a typical 3 Fr silicone PICC would be approximately 1 cm of length up the lumen of the catheter.


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