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  2. ULTRASONIC CLEANERS • Primary Users • It is the responsibility of the Central Sterile Section (CSS) to provide clean and sterile medical and surgical supplies and instruments for patient care. • Purpose • To clean medical instruments and utensils before sterilization • Today’s surgical instruments are manufactured to very strict tolerances leaving gaps and hiding places for micro-organisms that cannot be reached by manual hand cleaning

  3. ULTRASONIC CLEANERS • Ultrasonic cleaning takes place after proper manual cleaning and before sterilization • Can be used for practically any cleaning task provided that the liquid chemicals or water can reach those parts to be cleaned • Cleaning in most instances requires that a contaminant be dissolved (as in the case of a soluble soil), displaced (as in the case of a nonsoluble soil) or both dissolved and displaced (as in the case of insoluble particles being held by soluble binder such as oil or grease)

  4. ULTRASONIC CLEANERS • Comparing Chemical and Ultrasonic Cleaning • Chemical cleaning dissolves the contaminant causing a saturated layer to develop at the interface between the fresh cleaning chemicals and the contaminant • Saturated layer will stop cleaning • Saturated chemical can no longer attack the contaminants • Fresh chemicals cannot reach the contaminant

  5. ULTRASONIC CLEANERS • Ultrasonic cleaner energy effectively displaces the saturated layer to allow fresh chemistry to come into contact with the contaminant • The mechanical effects of ultrasonic sound wave energy can be helpful in both speeding dissolution and displacing particles • This is especially beneficial when irregular surfaces or internal passageways need to be cleaned • Ultrasonic cleaning is a very effective way of cleaning such utensils because it removes all organic material • Greatly reduces post-operative infection and cross-contamination between patients

  6. ULTRASONIC CLEANERS • Ultrasonic sound wave energy consists of sound waves at frequencies above those detectable by the human ear (normal human hearing range is between 20 Hz to 20 KHz) • An electronic frequency generator creates the ultrasonic frequency needed by the ultrasonic cleaner • Industrial ultrasonic cleaning applications utilize the frequency range between 20 kHz to 100 kHz, medical applications uses the frequency range between 20 kHz to 40 kHz

  7. ULTRASONIC CLEANERS • Principles of Ultrasonic Cleaning • The cleaning action consists of high powered acoustical energy being applied to solid objects immersed in a light viscosity liquid • The high powered acoustical energy creates cavitation (Cavitation is the process of creating microscopic bubbles in a light viscosity liquid)

  8. ULTRASONIC CLEANERS • Light viscosity liquids have varying surface tension, viscosity, and vapor pressure • Surface tension – the cohesive force between liquid molecules, this cohesive force is stronger on the surface than on the molecules under the surface (it is easier to move an object under the water than on the surface of the water)

  9. ULTRASONIC CLEANERS • Viscosity – thickness of the liquid or gas (syrup compared to water) • Vapor pressure – at the boiling point, saturated vapor pressure equals atmospheric pressure • Liquids have a much greater potential for movement than solids • Higher forces of attraction than gases • Water is a molecular liquid that will evaporate at all temperatures but boils at a well-defined temperature of 100 degrees centigrade (212 Degrees F) at a pressure of 1 atmosphere • Since the bubbles produced are extremely fine (microscopic), they find their way into tiny crevice

  10. ULTRASONIC CLEANERS • Cavitation • Cavitation creates fine bubbles in liquids in and around solid objects submerged in the solution where the bubbles implode loosening foreign matter and dirt • The size of the bubbles depends upon • The surface tension of the liquid • Temperature • Water near freezing would require large amounts of energy to create bubbles (cavitation) because of the close proximity of the water molecules


  12. ULTRASONIC CLEANERS • Boiling water would decrease the cavitation (bubble production) action due to the water molecules being too far apart • Wetting action of the detergent (ability of the detergent to “seep” into contaminate) • Frequency of the applied ultrasonic energy (higher frequency translates to more cavitation; bubble production)

  13. Cavitation (Continued) • The implosion generates minute vacuum areas • which are responsible for the cleaning action • During the duration of acoustic vacuum phase, negative pressure creates microscopic bubbles within the liquid that will expand forming gaseous cavities in the liquid • During the ultrasonic compression phase • Enormous pressure is exerted onto the newly expanded bubble compressing it up to approximately 500 atmospheres or over 7000 PSI

  14. Cavitation (Continued) • During the ultrasonic compression phase • Hugely increasing the gas bubbles internal temperature, to a temperature in excess of 10,000 degrees F • Bubbles implode releasing vast amounts of impact energy traveling at a speed of approximately 400 km/hr/ 248 miles per hour

  15. Cavitation (Continued) • During the ultrasonic compression phase • Impact energy interacts both physically and chemically • In physical terms a “micro brushing” effect is achieved at the frequency of the generator • In chemical terms, the cleaning effect of the chemical substance present in the detergent is enhanced by the ultrasonic bath

  16. Bath Temperature • The optimum bath temperature ranges between 80º and 110º F • Why is this important? • Because if the temperature rises above 140º F protein (blood) coagulates making it more difficult to remove protein materials

  17. Degassing • If excess gas is present in the cleaning solution or water, it decreases cleaning efficiency because the cleaning bubbles fill with gas (filling a box with Styrofoam peanuts to soften impact with objects within the box) • The energy released during implosion is reduced by this “cushioning” effect

  18. Degassing (Continued) • The cleaning solution or water is readily degassed by applying ultrasonic energy to the cleaning bath • There is no definitive time period for degassing cleaning solutions because of too many variables contained within the mixture • Tap water with no other chemical added should be degassed no less than 5 minutes each time it is changed

  19. Locations • Central Sterile Supply (CSS) Department • Physically located near surgery but is a separate and distinct department • Specialized expertise and direct responsibility for providing clean and sterile medical/surgical supplies and equipment for patient care • Medical Laboratory - used to clean laboratory utensils • Dental Laboratory - used to clean and polish artificial teeth

  20. Alternate Cleaning Methods • Manual Cleaning • Washing Machines • Washer Disinfectors • Washer Sterilizers