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

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)

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

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

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

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)

ULTRASONIC CLEANERS

Light viscosity liquids have varying surface tension, viscosity, and vapor pressureSurface 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)

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

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

ULTRASONIC CLEANERS

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)

ULTRASONIC CLEANERS

Cavitation (Continued)

The implosion generates minute vacuum areaswhich are responsible for the cleaning actionDuring 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 phaseEnormous pressure is exerted onto the newly

expanded bubble compressing it up to approximately 500 atmospheres or over 7000 PSI

Cavitation (Continued)

During the ultrasonic compression phaseHugely 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

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

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

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

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

Locations

Central Sterile Supply (CSS) DepartmentPhysically 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 utensilsDental Laboratory - used to clean and polish artificial teeth

Alternate Cleaning Methods

Manual CleaningWashing MachinesWasher DisinfectorsWasher Sterilizers