Automated Cleaning Methods

Automated cleaning equipment provides standardized, reproducible, and validated cleaning results that are more consistent than manual cleaning alone. However, automated cleaning does not replace manual cleaning entirely — it supplements and enhances it.

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Types of Automated Cleaning Equipment

1. Washer-Disinfectors (WDs)

The primary automated cleaning equipment in most CS departments.

Cycle phases:

1. Pre-wash/flush — Cold water rinse to remove gross soil
2. Enzymatic wash — Detergent applied at specified temperature
3. Rinse — Multiple rinse cycles to remove detergent residue
4. Thermal disinfection — Water heated to 180-195°F (82-90°C) for a specified time
5. Drying — Heated air drying phase (some models)

Key points:

• Thermal disinfection at 180°F+ for the appropriate exposure time provides intermediate-level disinfection
• Items must still be sterilized after washer-disinfection if they are critical or semi-critical items intended for sterilization
• Proper loading is essential for effectiveness:
  • Open all hinged instruments
  • Position instruments with concave surfaces facing down for drainage
  • Do not overload — water and detergent must reach all surfaces
  • Separate dissimilar metals to prevent galvanic corrosion
  • Use appropriate racks and adapters for specific instrument types

2. Ultrasonic Cleaners

Use high-frequency sound waves (20,000-40,000 Hz / 20-40 kHz) to create millions of tiny bubbles in the cleaning solution. These bubbles implode on contact with surfaces, creating a scrubbing action called cavitation.

How cavitation works:

• Sound waves create alternating high and low pressure zones in the liquid
• In low-pressure zones, microscopic bubbles form (cavitation)
• In high-pressure zones, these bubbles collapse violently against instrument surfaces
• The collapsing bubbles generate intense localized energy that dislodges soil from crevices, hinges, serrations, and other hard-to-reach areas

Key points:

• Ultrasonic cleaning is a CLEANING process only — it does NOT disinfect
• Instruments must be fully submerged in the ultrasonic solution
• Do not place hands in the ultrasonic solution while the unit is operating — cavitation can damage tissue
• Lids should be closed during operation to prevent aerosolization
• Degassing is required when filling with fresh solution — run the unit empty for the manufacturer-recommended time to remove dissolved air
• Solution should be changed at regular intervals or when visibly contaminated
• Chrome-plated instruments should not be processed in ultrasonic cleaners (plating may separate)

3. Cart Washers

• Large, drive-through or roll-in washers for case carts, transport carts, and large containers
• Operate similarly to washer-disinfectors but on a larger scale
• Ensure all surfaces are accessible to the wash spray

4. Washer-Sterilizers (Older Technology)

• Combine washing and steam sterilization in one cycle
• Being phased out in many facilities due to limitations:
  • Items are sterilized while wet (reduces sterile barrier)
  • Difficult to validate
  • Modern washer-disinfectors + separate sterilizers provide better results

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Cleaning Verification Testing

Automated cleaning equipment must be monitored regularly to verify it is functioning correctly:

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