Hydrophobic Filter in EVD Systems: What It Does
What a hydrophobic filter does in an EVD system: why drainage needs venting, why a wet filter matters, and how it fits in EVD-010 and EVD-020.
A hydrophobic filter in an EVD system is a vent: it lets air pass while repelling water-based fluids such as cerebrospinal fluid (CSF), so air can move without an open port. DESU EVD-010 and EVD-020 systems both include one as a core drainage component, alongside an 800 ml air-filtered drainage bag.
Key takeaways
- A hydrophobic filter is a vent: it lets air pass while repelling water-based fluids such as CSF.
- Venting matters because fluid entering a closed space has to displace air.
- EVD-010 and EVD-020 both include a hydrophobic filter, and separately a drainage bag air filter.
- What to do with a wetted filter is set by the instructions for use and hospital protocol.
The filter is a small part of DESU EVD sets with a simple job. Use in practice is governed by the instructions for use and hospital protocol.
What does hydrophobic mean?
Hydrophobic means water-repelling. A hydrophobic filter is a membrane with very fine pores, made of a material that water-based liquids do not readily wet. Air passes through the pores. A water-based liquid tends to bead on the surface instead of soaking through, under normal conditions.
CSF is mostly water, so the same principle applies to it. That is the whole idea of the part: a route for air that is not a route for fluid.
Why does an EVD system need a vent?
External drainage works largely by gravity. CSF flows from the catheter along the line and down into a collection path. In the DESU sets, that path runs through a 150 ml drip chamber into an 800 ml bag.
Any enclosed space that receives fluid has to give up the same volume of air. If that air has nowhere to go, pressure builds inside and flow can slow or stop. The opposite is also true: fluid leaving an enclosed space needs air to take its place.
A simple open port would solve the problem, but it would leave the inside of the system open to the room. A filter gives the air a path through a membrane instead. EVD-020 is a closed system, with a hydrophobic filter and two three-way connectors.
What do DESU EVD systems include?
Both series have the same drainage components.
| Item | EVD-010 | EVD-020 |
|---|---|---|
| Hydrophobic filter | Yes | Yes |
| Drainage bag | 800 ml, air-filtered | 800 ml, air-filtered |
| Drip chamber | 150 ml | 150 ml |
| Three-way connectors | 2 | 2 |
| Reinforced connection line | 60 cm, with locking mechanism | 60 cm, with locking mechanism |
The hydrophobic filter and the drainage bag air filter are separate items. The bag’s filter is integrated. The bag can also be ordered separately: ENDS-B1, ENDS-B5 and ENDS-B10 are packs of 1, 5 and 10.
What happens if a hydrophobic filter gets wet?
Hydrophobic does not mean immune to liquid. In vent filters of this kind, a film of fluid on the membrane can block the pores to air. A blocked vent can no longer do its job, and drainage may slow or stop even though the catheter and line are open.
This is one reason teams pay attention to how the collection path is handled when a patient is moved or repositioned. See transporting a patient with an EVD for the questions units raise. What to do with a wetted filter on a particular system is set by the instructions for use and the hospital protocol.
What should nurses and buyers check?
At receipt or set-up, the EVD set components checklist covers the filter along with everything else. The instructions for use are the reference for how the filter is positioned in use, how to keep it dry and what to do if it becomes wet. Filter details needed for a technical evaluation are available from our product specialists.
A filter is one part of a closed system. It does not take the place of careful handling, and no single component should be presented as the answer to infection control.
Does the filter change with the catheter option?
No. EVD-010 pairs the same drainage system with a standard or an antibiotic-impregnated ventricular catheter, and EVD-020 is used with a ventricular or a lumbar catheter. The hydrophobic filter is part of the drainage system in each case, so these choices change the catheter, not the vent.
Talk to a DESU product specialist
For filter details, or the instructions for use for your EVD set, our product specialists can help. Write to sales@desu.tr, use the contact page, or request a quote.
Frequently asked questions
Is the hydrophobic filter the same as the air filter on the bag?
No. They are separate items: the air filter is integrated into the drainage bag. The instructions for use are the place to confirm how each one works in the set.
Does a lumbar EVD-020 configuration include the filter?
Yes. The hydrophobic filter is a core component of the EVD-020 drainage system, and that system is used with either a ventricular or a lumbar catheter.
Can a replacement filter be ordered on its own?
The 800 ml air-filtered drainage bag has its own order codes; the hydrophobic filter does not. If your protocol calls for replacing it, tell our product specialists.
Related standards
- ISO 13485: Medical devices — Quality management systems
- ISO 10993 series: Biological evaluation of medical devices