SPD Sterilization Methods and Monitoring 2 — Questions and Answers
Question 1: What are the two main types of steam sterilizers used in healthcare facilities?
- Microwave and infrared sterilizers
- Gravity-displacement and dynamic-air-removal (pre-vacuum) steam sterilizers (Correct answer)
- Dry heat and chemical vapor sterilizers
- Flash and tabletop sterilizers
Correct answer: Gravity-displacement and dynamic-air-removal (pre-vacuum) steam sterilizers
Gravity-displacement and pre-vacuum are the two primary steam sterilizer types, differing in how they remove air from the chamber.
Gravity-displacement sterilizers rely on steam pushing air down and out by gravity — slower but suitable for non-porous items, liquids, and waste (250°F/121°C for 30 minutes). Dynamic-air-removal (pre-vacuum) sterilizers use vacuum pumps to actively remove air, enabling faster cycles (270°F/132°C for 4 minutes for wrapped items). Pre-vacuum sterilizers require daily Bowie-Dick testing.
Question 2: What is ethylene oxide (ETO) sterilization and when is it used?
- A high-temperature sterilization method for metal instruments
- A low-temperature gas sterilization method for heat-sensitive and moisture-sensitive devices (Correct answer)
- A chemical cleaning process for endoscopes
- An ultraviolet light sterilization method
Correct answer: A low-temperature gas sterilization method for heat-sensitive and moisture-sensitive devices
ETO is a low-temperature gas sterilant for devices that would be damaged by the heat and moisture of steam sterilization.
ETO operates at low temperatures (37-63°C) through alkylation of microbial proteins and nucleic acids. Used for heat-sensitive devices, moisture-sensitive items, and complex devices with long narrow lumens. Disadvantages include long cycle times (2-12 hours plus 8-12 hours aeration), carcinogenicity, environmental regulations, and higher costs. Despite challenges, ETO remains essential for many modern medical devices.
Question 3: How does hydrogen peroxide gas plasma sterilization work?
- It uses liquid hydrogen peroxide to soak instruments
- Hydrogen peroxide vapor is injected into a vacuum chamber and energized into a plasma state, then breaks down into water and oxygen (Correct answer)
- It combines hydrogen peroxide with steam
- It requires high temperatures above 200°F
Correct answer: Hydrogen peroxide vapor is injected into a vacuum chamber and energized into a plasma state, then breaks down into water and oxygen
H2O2 gas plasma sterilizes at low temperatures through vapor-phase killing plus plasma activation, leaving only harmless water and oxygen.
The process involves: vacuum air removal, H2O2 vapor injection and microbial killing, radiofrequency plasma generation for additional killing, and decomposition into water vapor and oxygen. Advantages: low temperature (45-55°C), short cycles (28-75 minutes), no toxic residuals, no aeration needed. Limitations: cannot use cellulose-containing materials (paper, cotton), restricted for long narrow lumens, and limited chamber sizes.
Question 4: What are the three types of sterilization monitoring and what does each verify?
- Visual, audio, and electronic monitoring
- Physical monitoring verifies cycle parameters, chemical monitoring confirms sterilant exposure, and biological monitoring proves lethality to microorganisms (Correct answer)
- Weekly, monthly, and annual monitoring
- Temperature, pressure, and humidity monitoring
Correct answer: Physical monitoring verifies cycle parameters, chemical monitoring confirms sterilant exposure, and biological monitoring proves lethality to microorganisms
Physical checks the machine worked, chemical confirms exposure occurred, and biological proves killing happened.
Physical monitoring reviews time, temperature, and pressure parameters. Chemical indicators change when exposed to sterilization parameters. Biological indicators use living spores of the most resistant organisms. AAMI ST79 requires all three: physical parameters every cycle, chemical indicators in every package, and biological indicators at minimum weekly plus every implant load.
Question 5: What is immediate-use steam sterilization (IUSS) and when is it appropriate?
- IUSS is the standard sterilization method
- IUSS is an abbreviated cycle used only in urgent situations when a properly sterilized item is not available and patient safety requires immediate access (Correct answer)
- IUSS can replace routine sterilization
- IUSS uses lower temperatures for delicate instruments
Correct answer: IUSS is an abbreviated cycle used only in urgent situations when a properly sterilized item is not available and patient safety requires immediate access
IUSS is reserved for urgent, unplanned situations and should never be used as a routine method or to compensate for insufficient inventory.
IUSS uses shorter exposure times without standard packaging. Appropriate ONLY when a critical instrument is urgently needed and no sterile alternative is available, AND the item is properly cleaned first. NOT appropriate for routine processing, compensating for inventory, convenience, or implantable devices. Excessive IUSS use is a red flag for accreditation surveyors.
Question 6: What is the significance of the D-value in sterilization science?
- The D-value measures the sterilizer chamber size
- The D-value is the time required at a given temperature to kill 90% of a specific microorganism population (Correct answer)
- The D-value is the shelf life of sterile items
- The D-value measures steam penetration depth
Correct answer: The D-value is the time required at a given temperature to kill 90% of a specific microorganism population
The D-value quantifies microbial resistance and is fundamental to calculating exposure times needed for the required Sterility Assurance Level.
The D-value (decimal reduction time) is the time to reduce a microbial population by 90% at a specific temperature. For example, with a D-value of 1 minute at 121°C, starting with 10^6 spores: after 6D, 10^0 (1 organism) survives; after 12D, SAL of 10^-6 is achieved. Understanding D-values explains why minimum exposure times are critical and why BI organisms are selected for exceptional resistance.
SPD Sterilization Methods and Monitoring 2
What are the two main types of steam sterilizers used in healthcare facilities?