Air / Water Channel Assembly
Using test articles, the air and water channels were made from 1.2 mm inner diameter (ID) by 1775 mm lengths of clear polytetrafluoroethylene (PTFE) tubing and joined with a stainless steel “y” connection.
The air and water channels were steam sterilized at 132degC for 6 minutes, then sealed with “hot-melt” thermoplastic polymer and confirmed airtight by pressurizing Air / Water Channel Assembly under water. The test articles also contained a syringe attached to the test article’s two Luer locks that was used for inoculating P. aeruginosa solution and for depressing the plunger to remove excess inoculum after 30 minutes of incubation under ambient conditions.
Installation
The air/water channel assembly consisted of a 1.0 mm ID by 185 mm length of clear PTFE tubing with a stainless steel “y” connection that combined the air and water channels into a common channel. The metal Y connector was sealed with “hot-melt” thermoplastic polymer and pressurized under water to verify that it was airtight. Luer locks were attached to the air and water channels as a mode to deliver forced air or liquid flushes.
For manual final water rinses, the test article was placed in a basin with the manufacturer-issued adapters appropriately attached and the directed volume of water (dyed blue) applied to each channel system using a syringe attached to the adapters. After the water was drained, the external surfaces were dried with lint-free Air / Water Channel Assembly cloths and valve cylinders and ports were dried with cotton swabs. The auxiliary water channel and elevator guide-wire channel were irrigated to dilute any remaining dyed liquids. For the suction/instrument channel system, a suction pump was connected to the light guide connector unit end of the test article to aspirate residual water from the channel system.
Design
An air / water channel assembly has a lot of moving parts, so it is important to design the part appropriately. For example, the “y” connection area was sealed with a high-temperature plastic polymer (Cole-Parmer, Vernon Hills, Illinois, USA), and the water channel holder was designed with multiple mounting points to minimize the chances of contamination. The y-shaped air channel was also designed with a clear tubing to allow for direct visualization of approximately 0.1 uL of the liquid inside. In addition, an ATS-EPC was inoculated into the channel to test for its ability to slurp up a small amount of fluid and display it to the human eye. The slurp was able to show up on an image of the endoscope using a microscope.
Replacement
A damaged Air / Water Channel Assembly can cause problems with suction and air insuflation. When this occurs, the hose barbs, air passages and tubing may have to be replaced. The Air / Water Channel Assembly includes two pieces of tubing that are pressed into hose barbs. One piece has a brass pinch bar that pinches off one or the other of the small air tubes when the flow adjust knob is turned (Figure 1-4). If this tubing becomes pinched between the two hose barbs, it can seal off and block the passages. In some cases, a replacement of this tubing is all that is needed to remedy the problem.
