Background

A high offset in sterile packaging may be seen with large animal implant catheters that were. The offset value can range from 10 mmHg to 60 mmHg or more while still in its packaging. After the implant package is opened and catheter tip is removed, the pressure value will return to normal.

This high offset while in the packaging is due to thickened gel in the catheter tip cover. The gel thickening is a result of a chemical reaction, called cross-linking, which occurs during the manufacturing process and is induced by uncured adhesive in the extended tip cover.  The likelihood of cross-linking and high offsets is low, but there is still potential for it to occur especially when implants are stored for a few months prior to implantation.  

Symptoms

Either 1 of the symptoms may occur (or occur simultaneously):

• Pressure reading prior to implantation (Checking Pressure Offset Prior to Implantation) shows more than the expected pressure drift (PTD Implant Specification)
• The meniscus has a bullet shape versus a square share (as shown in the picture below)

Resolution

DSI has tested that the removal of the tip alone will resolve this issue.  

Removal of the tip cover should be done by alternating gentle traction and release. Take care to prevent gel loss due to compression of the catheter or sudden release of the tip cover. Always examine the catheter under high magnification prior to implantation for gel loss or bubbles. If there is gel loss or bubbles, the catheter will need to be regelled. For help with this process, refer to the Guidelines for the Regel of the PhysioTel and PhysioTel Digital Large Animal Devices article on the DSI Support Center. 

After the removal of the tip cover and re-gel, when appropriate, recheck the pressure offset.