Technology

Description of the technology the theory behind it and how it works.

UV sterilization
UVC LED diodes
Light propagation in polymer tubes

TECHNOLOGY

UV disinfection

A method for killing bacteria is exposure to ultraviolet light (UV). The most germicidal part of UV spectrum, designated UVC, occurs at wavelengths < 280 nm. UVC has become a useful tool for disinfecting aquatic systems, such as water distribution systems. UVC is used at hospitals and in other health care environments for deactivating airborne pathogenic microorganisms, and has recently been demonstrated to be effective for treating chronic wounds infected with methicillin resistant staphylococcus aureus. UVC doses between 1-30 mJ/cm2 effectively kill 99.9% of viable planktonic bacteria.

UV light propagation in polymer tubes

The propagation of the germicidal light lengthwise through the interior of the catheter depends both on the optical properties of the catheter material and the aqueous solution injected into the catheter lumen. If the refractive index of the catheter material is smaller than that of the aqueous solution contained in the tube lumen, light propagation lengthwise inside the catheter is favored by the so-called ‘liquid light guiding’ principle. In order to implement and optimize liquid light guiding knowledge about the UVC optical data of common polymers used for catheter manufacturing and for the liquids filling the tubes would be advantageous. A major problem is that apparently no optical data (refractive index) is available in the UVC spectral range for the polymers used for catheters. UVC light propagation through tubes made in different materials must then be determined and optimized empirically. The refractive index of the solution injected into the tube lumens is increased by adding ionic compounds such as sodium chloride to pure water (5-30 % NaCl).

UV disinfection of catheters

Several technical problems have to be solved before UVC light can be considered as a method for disinfection of patient catheters. First, the light source should be small and have a geometrical shape that allows the light to be launched effectively into the small catheter openings (few millimeters). It is not possible to focus the light from common UV light sources such as mercury discharge lamps into a small spot without a substantial loss of intensity due to the cylindrical shape and relative large size of these lamps. Newly developed UVC light sources based on light emitting diode (LED) technology combined with appropriate lens systems are much more applicable in that respect because of the fact that almost all light emitted from the light source can be focused into a small spot and launched directly into the tube lumen.