uv light wand for elimination of bacteria found in pediatric endotracheal tubes team members: sarah...
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UV Light Wand for Elimination of Bacteria Found in Pediatric Endotracheal Tubes
Team Members:Sarah Hodges Matthew Sundermann Jeffrey Turner Sarah Williams
Advisors
•Neal Maynord, MDPediatric Critical Care FellowMonroe Carell Jr. Children's Hospital
at Vanderbilt
•Ty Berutti, MD, MS, MSAssistant Professor, Pediatric Critical
CareMonroe Carell Jr. Children’s Hospital
at Vanderbilt
Other Correspondents• James Harrington- Rutgers University, fiber
optics expert, mostly IR but some UVJames A. HarringtonDepartment of Material Science and EngineeringRutgers University
• Prof. Yuji Matsuura at Tohoku University in Japan- Contact given to us by Dr. Harrington DOKO Engineering- Japan
Problem Statement
•Ventilator Associated Pneumonia (VAP) is the second most common infection acquired by patients in the pediatric ICU
•20% of nosocomial infections in the PICU can be identified as VAP
•VAP affects 30% of patients with a critical illness
•Need a more efficient way to clear bacteria from pediatric endotracheal tubes to prevent VAP
Effects of VAPVAP Cause
of VAP
Extended mechanical ventilation
Bacterial build-up in
endotracheal tube
4 Day Extension of hospital stay
Increased cost of care
($10,000 per VAP case)
Increased mortality rate
Silver Nitrate Coated Endotracheal Tubes Reduce but Do Not Eliminate Bacterial Colonies
•STUDY: ▫ 12 of 21 bacteria populations the silver
coated endotracheal tubes reduced bacterial counts
▫ 7 the counts stayed constant ▫ 2 (specifically Enterobacter aerogenes and
Enterobacter cloacae) the colony count rose
•A more effective method of eliminating bacteria is necessary
UV Light Effectively Eliminates Bacterial Colonies Present in VAP
•E. coli is generally representative of a wide range of Gram negative bacteria
•High intensity UV light of wavelength 200- 300 nm causes effective inactivation of the bacteria
•Maximum inactivation of E. coli occurs at 270 nm
Ultraviolet Radiation Safety Concerns
•UV-C (100 -280 nm) cannot penetrate the dead layer of human skin, but can burn the cornea
•UV-C kills bacteria•No regulatory limits but the American
Conference of Governmental Industrial Hygienists (ACGIH) publishes Threshold Limit Values (TLV) ▫250 mJ/cm2 at 180 nm and 3.1 mJ/cm2 at 275 nm
•UV light can be blocked by opaque surfaces
http://www.americanairandwater.com/UV-pdf/ultraviolet-radiation-safety.pdf
Primary Objective
•Design a device using UV technology to reduce the occurrence of VAP in pediatric patients
Secondary Goals •Device goals
▫Effectively kill bacteria ▫Fit through a 3mm diameter pediatric
endotracheal tube ▫ Flexibility sufficient to travel down the entire
length of an endotracheal tube •Build a prototype of the device • Test prototype to determine safety (Amount
of UV light allowed to escape from the endotracheal tube) and efficacy against bacteria
Solution Description • UV light source coupled to a hollow optical waveguide with an
internal aluminum coating
• UV light travels down the length of the hollow waveguide and is emitted from the end
• UV light strikes either reflection or scattering system and irradiates sides of the endotracheal tube ▫ May occlude up to 80% of the tube for about 15 seconds at the time
• Irradiation kills the bacteria in the tube
• Silicon tube and silver tube lining used to protect patient from UV radiation (will test UV light escape using both types of tubes)
Solution Description
UV Lasers for Light Source
•Advantages of using UV lasers▫Collimated light
Less light loss Easier to couple
▫More power possible Expose tube for less time Kill more bacteria
UV Light Source • UV TOP LEDs from Sensor
Electronic Technology, Inc▫ Can obtain at 270 nm
wavelength▫ Power 600 µW▫ Ball Lens to focus light
http://www.s-et.com/products/uvtop.html
Hollow Optical Waveguides • Traditional optical fibers
are not an option for transmitting UV light ▫ Traditional materials
absorb UV light
• Solution: Hollow Optical Waveguides ▫ Hollow core filled with air
(inert gas)- absorption loss in the core eliminated
▫ Aluminum thin-film coating on the inside of a capillary tube
Doko Engineering LLC
Performance Criteria and Other Design Considerations • Compatibility constraints
▫Solution must be suitable for pediatric applications▫Patient must be protected from harmful UV light
• Cost and Reusability Constraints▫Protective sheath on any device desirable for
efficiency
• Effectively eliminate bacteria ▫A sufficient amount of light must reach the
bacteria
Pediatric Endotracheal Tubes- 3 mm diameter minimum
J. Pediatr. (Rio J.) vol.79 suppl.2 Porto Alegre Nov. 2003
Pediatric Endotracheal Tubes- Radius of Curvature
• Radius of curvature for larger (7mm) ETT > 15 cm
• Waveguides may not be suitable for smaller ETT
• Future work on this device could include thinner, more flexible waveguides as they are available
Silicon and Silver Protect the Patient from UV Light
• A study on contact lenses found UV-C light is significantly blocked by silicone ▫ ETT are typically silicone
• The silver coating on the inside of the silicone ETT provides an extra barrier to UV light▫ Photometer testing
• Need to ensure no UV light escape from the end of the tube
Laube et.al. 2004
Loss of Light- Factors
• Internal coating of the hollow waveguides ▫ Aluminum was found to
minimize this loss
• Bending of the waveguide
• Efficiency of coupling between the UV light source and waveguide
Matsuura et. al. 2004
Performance Metrics
•Success determined by: ▫Size appropriate prototype completed▫Photodetector indicates no UV light
escaping from the endotracheal tube▫Bacterial cultures eliminated
Cost-Benefit AnalysisPrototype Estimated Costs:
• $200 UV light waveguide (Doko Engineering, Japan)
• $250 UV LED (Sensor Electronic Technology, Inc., South Carolina)
• $100 in waveguide modifications (lenses and coupling)
• Total Cost Estimate: $550
Benefit:
• $10,000 average extra cost for each case of VAP- 300,000 cases of VAP per year
• Conservatively if we are 50% effective the benefit to each possible patient is $5,000
• About 27% of ICU patients are infected with VAP. Final benefit per patient will be $1,350
Future Work
•Order/ purchase materials for prototype
•Build prototype
•Test prototype against bacteria
•Determine light loss
References Laube T. Apel H. Koch HR. Ultraviolet Radiation Absorption of Intraocular Lenses. Opthamology.
2004. 111:880-885.
Matsuura Y. Harrington JA. Optical Properties of Small-bore Hollow Glass Waveguides. Applied Optics. 1995. Vol. 34 No. 30.
Matsuura Y. Miyagi M. Hollow Optical Fibers for Ultraviolet and Vacuum Ultraviolet Light. IEEE Journal of Selected Topics in Quantum Electronics. December 2004. Vol 10 No. 6.
Matsuura Y. Miyagi M. Hollow Waveguide for Ultraviolet Light and Making the Same. United States Patent. October 2000.
“Prevention of Ventilator Associated Pneumonia VAP”, American Society of Anesthesiologists. http://www.asahq.org/For-Members/Advocacy/Office-of-Governmental-and-Legal-Affairs/Prevention-Of-Ventilator-Associated-Pneumonia-VAP.aspx .
Rello J. et. al. Activity of a Silver Coated Endotracheal Tube in Preclinical models of ventilator- associated pneumonia and a study after extubation. Crit Care Med. 201 0 Vol 38 No. 4.
Wang T. et.al. Pulsed ultra- violet inactivation spectrum of Escherichia coli. Water Research. 2005 Vol. 39: 2921-2925.