Common Causes of Failure in Hydrogen Peroxide Low-Temperature Plasma Sterilization and Corresponding Remedial Measures

1. Instrument/Item Preparation and Loading Issues (Most Common Cause): This is the primary cause of sterilization failure, accounting for over 50% of cases.

1. Incomplete cleaning:

Residues of blood, tissue, proteins, salts, and other organic or inorganic materials on instruments can consume and obstruct the penetration and contact of hydrogen peroxide gas/plasma.

2. Insufficient drying:

Micro amounts of moisture in instrument lumens or joints that are not visible to the naked eye can dilute hydrogen peroxide, reducing its effective concentration and even causing sterilization cycles to stop due to "excessive humidity".

3. Improper packaging:

• Using packaging materials that do not meet requirements (e.g., cotton, paper, oil, water, powders, wood, etc. which are not resistant to hydrogen peroxide).
• Overtight or excessive packaging that hinders gas diffusion.
• Instruments with lumens not using the correct adapters, or mismatched adapter models, leading to gas being unable to reach deep into the lumen.

4. Overloading or improper placement:

• Overloaded items or items placed too densely, blocking the diffusion device inside the sterilization chamber, creating "shadow areas".
• Improper placement of metal and non-metal items together (metal items should be placed on the lower chamber to avoid shielding the electric field).
• Items touching the chamber wall or door, affecting gas circulation and plasma generation.

5. Complex instrument structure:

Instruments with long lumens (such as laparoscope lenses), blind ends, or fine pores (such as springs) have high requirements for gas penetration and replacement, making them prone to failure if process control is not stringent.

2. Equipment and Consumable Related Issues

1. Equipment failure or aging:

• Declining vacuum pump performance: Unable to achieve the required vacuum, affecting hydrogen peroxide vaporization and injection, and ultimately plasma generation.
• Hydrogen peroxide injector malfunction: Incorrect injection dosage (too little or leakage).
• Pressure/humidity/temperature sensor drift: Causes the equipment to operate under incorrect parameters.
• Plasma generator insufficient power: Affects the final sterilization effect.
• Diffusion device blockage or damage: Causes uneven gas distribution.

2. Cassette (Hydrogen Peroxide Sterilizing Agent) Issues:

• Expired or improperly stored (e.g., high temperatures, sunlight) hydrogen peroxide, reducing its effective concentration.
• Incorrect installation of the cassette, leading to leaks.
• Use of non-original or incompatible cassettes.

3. Biological/Chemical Indicator Issues:

• Indicators themselves are ineffective or expired.
• Biological indicator (BI) cultivation process is not standardized (e.g., incubator temperature not correct, insufficient incubation time).
• Chemical indicator (CI) reading errors.

3. Cycle Parameters and Program Selection Issues

1. Incorrect program selection:

The sterilization program has not been selected based on instrument material, lumen length, and complexity (e.g., standard instrument program vs. long-lumen instrument program).

2. Cycle cancellation or interruption:

• The equipment aborts the vacuum phase due to excessive moisture or leakage.
• Power instability causes the cycle to be interrupted.
• Operator inadvertently cancels.

3. Environmental factors:

• Low environmental temperature: Affects hydrogen peroxide vaporization efficiency and sensor accuracy inside the equipment.
• High environmental humidity: Equipment inhales moist air, increasing internal moisture and interfering with the process.
• High altitude: Affects the equipment’s vacuum ability and boiling point, and some equipment needs altitude calibration.

4. Human Operation and Management Issues

1. Insufficient training:

Operators are unfamiliar with device operation procedures, loading requirements, instrument preparation specifications, and error code meanings.

2. Failure to perform routine monitoring:

• Failure to monitor using chemical indicators daily.
• Failure to perform biological monitoring regularly (e.g., weekly or per cycle).
• Failure to properly handle and analyze failed monitoring results.

3. Lack of equipment maintenance:

Failure to perform routine cleaning (e.g., chamber, diffusion device), periodic preventive maintenance (PM), and performance validation (e.g., annual testing) according to the manufacturer's or guide's manual.

Steps to Take When Sterilization Fails:

1. Immediate response: Re-clean, disinfect, and sterilize the failed batch of items, trace possible affected items.
2. Repeat test: Immediately perform a biological monitoring cycle without load, using new biological and chemical indicators. If successful, the problem is likely with item preparation or loading.
3. Check the equipment:
• Check whether the cassette is within its validity period and properly installed.
• Check whether the chamber is clean and dry and whether the diffusion device is functioning normally.
• Print and analyze the parameter curve from the failed cycle to see if there were any abnormal fluctuations in vacuum, injection, or plasma phases.
4. Review the process:
• Review the entire cleaning, disinfecting, drying, packaging, and loading process of the failed instruments.
• Check if the operator followed all steps properly.
5. Contact the manufacturer's engineer: If the empty test fails or the equipment frequently alarms, contact the engineer for professional testing (e.g., vacuum leak testing, hydrogen peroxide concentration testing, etc.).

Summary

Hydrogen peroxide low-temperature plasma sterilization is a highly precise chemical-physical process that requires strict process control. Most failures are not caused by equipment malfunctions but stem from issues with pre-treatment, loading, and human operation.

Establishing strict standard operating procedures (SOPs), providing thorough staff training, and implementing a complete quality control system are the key to ensuring successful sterilization.