Ultrasonic Cleaning and Automated Washer-Disinfector Operation

Ultrasonic Cleaning and Automated Washer-Disinfector Operation

Mechanical cleaning is the backbone of the decontamination process. Before any instrument can be safely sterilized, it must be thoroughly cleaned to remove bioburden—blood, tissue, bone fragments, and other organic or inorganic soil. Two workhorses of the sterile processing department (SPD) decontamination area are the ultrasonic cleaner and the automated washer-disinfector. Knowing how to load, operate, and document both correctly is a core competency tested by both the HSPA CRCST and CBSPD CSPDT exams.

How Ultrasonic Cleaners Work

Ultrasonic cleaners remove soil through a process called cavitation. High-frequency sound waves (typically in the range used for medical instrument cleaning) create millions of microscopic bubbles in the cleaning solution. When those bubbles collapse, they produce tiny but intense jets of energy that dislodge soil from instrument surfaces, including hard-to-reach lumens, serrations, and box locks.

Ultrasonic cleaning does not disinfect instruments—it is a cleaning step only. The instruments must still move through subsequent disinfection or sterilization processes.

Degassing the Ultrasonic Bath

Whenever fresh water and detergent solution are added to the tank, dissolved gases must be removed before instruments are loaded. This is called degassing. If the unit is not degassed, air bubbles in solution will absorb cavitation energy and significantly reduce cleaning effectiveness. To degas:

1. Fill the tank with the correct cleaning solution (enzymatic or manufacturer-specified detergent) at the water temperature recommended in the unit's Instructions for Use (IFU).

2. Run the unit without instruments for the degassing time stated in the IFU (commonly several minutes).

3. Do not skip this step even when the department is busy.

Loading Ultrasonic Cleaners Correctly

• Place instruments in a single layer, open-side down, so cavitation energy reaches box locks and internal surfaces.
• Never stack instruments—stacking shields surfaces and blocks cavitation.
• Keep instruments below the water surface but not resting on the tank bottom; use the provided basket.
• Separate dissimilar metals (e.g., aluminum and stainless steel) to prevent galvanic corrosion.
• Follow the unit IFU for maximum basket load and cycle time.

Verifying Cavitation: The Foil Test

Before relying on the ultrasonic cleaner for daily processing, and whenever cavitation is in doubt, perform a foil test (or the equivalent cavitation verification method specified by the manufacturer). Cut a piece of standard aluminum foil to fit inside the basket, submerge it, and run a short cycle. At the end, inspect the foil: uniform pitting and small perforations across the foil surface indicate active cavitation. A foil with no marks, or marks concentrated only on edges, suggests inadequate cavitation. Record the result—pass or fail—in the lab log with the date, time, and your initials.

Automated Washer-Disinfectors

A washer-disinfector is a large automated unit that moves instruments through several sequential phases: pre-rinse, wash (with detergent), rinse, optional ultrasonic phase (in some units), thermal disinfection rinse, and drying. The thermal disinfection rinse uses hot water to achieve a validated level of disinfection—this is quantified by the A0 value, a concept from international standards that represents the equivalent disinfection effect at a reference temperature. Washer-disinfectors do not sterilize instruments.

Loading the Washer-Disinfector

• Consult the manufacturer IFU and your facility's policies for rack and tray placement.
• Position instruments so water jets can reach all surfaces. Open all box locks and hinges.
• Point instrument tips downward when possible to allow drainage.
• Use instrument-specific accessories (e.g., lumen adaptors for hollow items) as directed.
• Do not overload racks; overloading blocks spray arms and reduces cleaning effectiveness.
• Check that spray arms can rotate freely after loading before closing the door.

Selecting the Correct Cycle

Different instruments require different cycles. Delicate or heat-sensitive items may need a lower-temperature cycle; heavily soiled instruments may require an extended wash phase. Always match the cycle to the instrument type per the IFU and facility protocol. Record the cycle name or number in the lab log before starting.

Monitoring and Documenting the Cycle

Modern washer-disinfectors produce a cycle printout or digital record that logs key parameters:

• Water temperature at each phase (especially the final thermal disinfection rinse)
• Cycle time for each phase
• Chemical pump status (detergent, neutralizer, rinse aid)
• Fault codes if any phase did not meet set-point values

You must review the printout immediately at cycle end. A cycle is considered passing only when all critical parameters meet the validated set points—no fault codes, correct temperatures, and correct phase durations. If any parameter is out of range, the load fails and must be reprocessed; do not release instruments for packaging or sterilization.

Reading Cycle Printouts: Pass or Fail?

When reviewing a printout, look for these common failure indicators:

| Deviation | Significance |

|---|---|

| Final rinse temperature below set point | Thermal disinfection not achieved |

| Phase time shorter than validated time | Cycle incomplete |

| Chemical pump fault | Detergent or rinse aid not dispensed |

| Door fault or interrupted cycle | Process compromised |

For a failed load: quarantine the instruments, document the failure with the specific deviation and the printout, notify your supervisor, and reprocess the load from the beginning. Never assume a borderline result is acceptable.

PPE Requirements in Decontamination

The decontamination area is classified as a restricted area with significant exposure risk. Always wear the full PPE ensemble: fluid-resistant gown, gloves, surgical mask or respirator, and face shield or goggles. Never reach bare-handed into an ultrasonic basket or washer rack while instruments are present. Inspect PPE before each session and replace anything torn or compromised.

Documentation Is Patient Safety

Every cycle you run must be documented. The record links a specific instrument load to a specific cycle with verified parameters. If a surgical-site infection is later investigated, cycle documentation is the evidence that cleaning was or was not performed correctly. Accurate, legible, and timely records protect the patient, the facility, and you.