CER Endoscope Sterilization Methods Questions and Answers 2 — Questions and Answers

Question 1: Which low-temperature sterilization method uses hydrogen peroxide gas plasma?

ETO sterilization
Peracetic acid immersion
STERRAD system (hydrogen peroxide gas plasma) (Correct answer)
Glutaraldehyde soaking

Correct answer: STERRAD system (hydrogen peroxide gas plasma)

The STERRAD system (Advanced Sterilization Products) uses hydrogen peroxide gas plasma to sterilize heat-sensitive instruments including some endoscopes.

Hydrogen peroxide gas plasma sterilization (e.g., STERRAD) works by first creating a deep vacuum and introducing hydrogen peroxide vapor which diffuses throughout the chamber and kills microorganisms. Radio-frequency energy then converts the residual peroxide to plasma, completing sterilization. The byproducts are water and oxygen — no toxic residues. Some flexible endoscopes are compatible with this method per their IFU, but channel length/diameter limitations exist.

Question 2: Why is steam sterilization (autoclaving) generally NOT used for flexible endoscopes?

Steam does not kill bacterial spores
The high heat and moisture of autoclaving damages the flexible materials and adhesives in endoscopes (Correct answer)
Steam sterilization takes too long
Steam sterilization requires special chemical indicators

Correct answer: The high heat and moisture of autoclaving damages the flexible materials and adhesives in endoscopes

Flexible endoscopes contain heat-sensitive polymers, adhesives, and electronic components that are destroyed by the high temperature and moisture of steam sterilization.

Standard steam sterilization requires temperatures of 121–134°C with high moisture, which melts adhesives, warps polymers, damages optical coatings, and destroys electronic sensors in flexible endoscopes. Endoscope manufacturers specifically prohibit steam sterilization. Low-temperature methods (ETO, hydrogen peroxide gas plasma, peracetic acid) are used instead. Only a few rigid endoscope components may be compatible with steam; always verify with the specific device's IFU.

Question 3: What is the Spaulding classification for flexible endoscopes that enter sterile body cavities (e.g., during ERCP)?

Non-critical — requires low-level disinfection
Semi-critical — requires high-level disinfection
Critical — requires sterilization (Correct answer)
Non-critical — requires intermediate-level disinfection

Correct answer: Critical — requires sterilization

Instruments that enter sterile body cavities or the vascular system are classified as critical and require sterilization per the Spaulding classification.

The Spaulding classification system categorizes medical devices by infection risk: Critical items contact sterile tissue or the vascular system and require sterilization (e.g., surgical instruments, some endoscopes entering bile ducts). Semi-critical items contact intact mucous membranes and require HLD minimum. Non-critical items contact only intact skin. Duodenoscopes used during ERCP enter the sterile biliary tree, technically classifying them as critical and ideally requiring sterilization.

Question 4: What is a key limitation of ethylene oxide (ETO) sterilization for flexible endoscopes?

ETO does not kill bacterial spores
ETO requires long aeration times (12–24 hours) to remove toxic residues before use (Correct answer)
ETO damages metal channels
ETO is only effective at high temperatures

Correct answer: ETO requires long aeration times (12–24 hours) to remove toxic residues before use

ETO is effective but requires prolonged aeration to remove toxic residual gas from materials before the endoscope can safely be used.

Ethylene oxide sterilizes effectively at low temperatures and is compatible with endoscope materials. However, ETO residues absorbed into polymers and rubber components are toxic and carcinogenic. After the sterilization cycle, items must be aerated (typically 12 hours at elevated temperature in a dedicated aerator or up to 7 days at room temperature) to allow residues to off-gas to safe levels. This turnaround time makes ETO impractical for routine endoscope reprocessing between patients.

Question 5: Peracetic acid immersion sterilization (e.g., SYSTEM 1E/EVOTECH) achieves sterilization at what temperature range?

121–134°C
50–60°C
Approximately 50–56°C (Correct answer)
Room temperature (20–25°C)

Correct answer: Approximately 50–56°C

Peracetic acid sterilization systems operate at approximately 50–56°C, making them compatible with heat-sensitive endoscopes.

Peracetic acid (PAA) sterilization systems (such as STERIS SYSTEM 1E) use a dilute solution of PAA (~0.2%) at 50–56°C, flowing through the endoscope channels under controlled pressure. At this concentration and temperature, it achieves a sterility assurance level (SAL) of 10⁻⁶ within a 25–30 minute cycle. It is effective against bacteria, spores, fungi, and viruses. Instruments are ready for immediate use with no aeration required.

Question 6: When should sterilization be considered instead of high-level disinfection for an endoscope?

When the procedure takes longer than 30 minutes
When the endoscope will penetrate a sterile body cavity or contact sterile tissue (Correct answer)
When the patient is immunocompromised
When the endoscope has failed a previous HLD cycle

Correct answer: When the endoscope will penetrate a sterile body cavity or contact sterile tissue

Instruments that penetrate sterile tissues or body cavities are classified as critical and require sterilization per the Spaulding classification.

The Spaulding classification requires sterilization for critical items contacting sterile body spaces. For GI endoscopy, most procedures involve contact with mucous membranes (semi-critical), for which HLD is the minimum standard. However, endoscopes used in ERCP (contacting sterile bile duct) or laparoscopy/arthroscopy (entering sterile cavities) are classified as critical and require sterilization. Patient immune status does not change the Spaulding category per se.

CER Endoscope Sterilization Methods Questions and Answers 2

Which low-temperature sterilization method uses hydrogen peroxide gas plasma?