Types of steam sterilization cycles: how to know which one your medical facility needs


Steam sterilization is a crucial process used by autoclaves in medical facilities to ensure the safety of patients and healthcare professionals. However, not all types of steam sterilization cycles are created equal. Medical facilities must choose the appropriate cycle to meet their specific needs.

In Celitron’s next article, we will explore the various kinds of steam sterilization cycles and provide guidance on how to determine which one is best suited for your medical facility.

What is a steam sterilization cycle in medical settings?

A steam sterilization cycle is a controlled and standardized process used by medical autoclaves to eliminate or kill microorganisms, including bacteria, viruses, and spores, from instruments, equipment, and materials using high-temperature steam. This cycle is a critical component of infection control in healthcare facilities and laboratories, ensuring that reusable items are safe for patient use by rendering them free of harmful pathogens.

The primary components of a steam sterilization cycle typically include the following steps:

  1. Preparation: Items to be sterilized are cleaned, inspected, and loaded into sterilization containers or trays.
  2. Air removal: Air within the sterilization chamber is removed to create a vacuum or reduce pressure. The removal of air is essential to facilitate the penetration of steam into all areas of the load.
  3. Steam exposure: High-temperature steam is introduced into the chamber, saturating the load. The temperature and pressure are carefully controlled to ensure effective sterilization.
  4. Sterilization period: The items are exposed to the steam for a specified period, during which time microorganisms are killed by the combination of heat and moisture.
  5. Drying: After sterilization, excess moisture is removed from the items to prevent damage and to prepare them for use or storage.
  6. Cooling: The sterilized items are cooled down to a safe handling temperature.

These cycles can vary in terms of temperature, pressure, and exposure time depending on the specific type of equipment, instruments, and materials being sterilized. Different types of steam sterilization cycles may be employed for various items, such as wrapped instruments, liquid-filled containers, heat-sensitive equipment, or items needed in emergencies.

Additionally, quality control measures, including biological indicator testing and cycle monitoring, are often employed to ensure the effectiveness of the sterilization process.

Comparing the 2 main types of steam sterilization cycles: Gravity and vacuum

While there are a multitude of custom settings and options you can choose with certain autoclaves, knowing the differences between the 2 main types of steam sterilization cycles can already help your medical facility make a choice.

1. Gravity steam sterilization cycle (class N, and most class S autoclaves)

This type of steam sterilization cycle is a simpler method to treat certain medical tools. It relies on gravity to remove air from the sterilization chamber and introduce steam.

  • Applications: Suitable for medical facilities dealing primarily with solid, unwrapped, non-porous instruments like metal trays, forceps, and scissors.
  • Advantages: Simplicity. Facilities with fewer instrument sterilization needs can benefit from this cycle.
  • Limitations: Gravity sterilization is less effective in penetrating complex instruments with intricate designs or porous materials. It is not recommended for sterilizing materials that need to remain in packaging for sterility.

2. Vacuum (or pre-vac) steam sterilization cycle (class B autoclaves)

This type of steam sterilization cycle is an advanced method used to achieve effective sterilization. It employs a series of vacuum pulses to remove air from the sterilization chamber before introducing steam. This process ensures that steam can penetrate all surfaces and cavities of instruments and materials, making it highly effective for sterilizing porous materials, wrapped instruments, and complex geometries.

  • Applications: Pre-vacuum sterilization is ideal for medical facilities that frequently sterilize instruments with intricate designs. This includes dental equipment, surgical instruments with hinges and lumens, and implantable devices. It’s suitable for materials that need to remain sterile while wrapped, such as surgical packs and sterile drapes. It's also highly efficient in sterilizing porous materials like gauze and textiles.
  • Advantages: Excellent steam penetration. The multiple vacuum pulses ensure thorough steam penetration into complex instruments, leaving no space untouched. Potentially faster cycle times.
  • Limitations: Regular maintenance is required to ensure the integrity of the vacuum system. This is made easier with the self and remote diagnosis options available with Celitron’s vacuum steam sterilizers, and you can also count on our after-sales support.

All of Celitron’s autoclaves fall under this category, regardless of size. We provide the same quality steam sterilization cycle performance for small clinics and large hospitals.

Other types of steam sterilization cycles

Depending on the autoclave you choose, you can also make use of settings that include different types of steam sterilization cycles. Here’s a rundown of the most notable options:

1. Flash Steam Sterilization Cycle

This type of steam sterilization cycle is designed for the immediate sterilization of instruments that are urgently needed in busy medical facilities. This cycle is characterized by its rapid process, but it requires strict adherence to guidelines to ensure sterilization efficacy. It also may not be suitable for all instrument types, as certain materials may not withstand the rapid cycle.

2. Low-temperature steam sterilization cycle

This type of steam sterilization cycle employs lower temperatures and longer exposure times to sterilize heat-sensitive materials, without compromising their integrity. This includes delicate instruments and equipment, including endoscopes, flexible scopes, and electronic devices.

3. Steam sterilization cycle for liquids

This type of steam sterilization cycle is tailored specifically for sterilizing liquid-filled containers. This process involves careful handling to prevent container breakage due to steam pressure. This cycle is crucial in ensuring the safety of liquid medications and culture media used in medical laboratories. Requires careful handling to prevent container breakage due to steam pressure.

With the slow exhaust cycle of Celitron’s autoclaves, you can sterilize liquids according to EN285, with natural cooling and an additional PT100 temperature probe.

4. Wrapped steam sterilization cycle

This type of steam sterilization cycle is designed specifically for sterilizing materials that are wrapped in packaging (surgical gowns, drapes, instrument packs). It employs steam under pressure to penetrate the packaging material and sterilize the contents. Of course, the packaging must be compatible with steam sterilization, and proper sealing is essential.

5. Unwrapped steam sterilization cycle

This type of steam sterilization cycle is designed for solid, non-porous instruments and equipment that can be sterilized without the need for packaging (metal trays, forceps). It is usually a faster cycle compared to wrapped sterilization. Be warned that it is not suitable for porous materials or items with complex designs.

6. Prion steam sterilization cycle

The prion steam sterilization cycle is specifically designed to destroy prions, infectious proteins that are notoriously difficult to eliminate on neurosurgical instruments. Prions are associated with diseases like Creutzfeldt-Jakob disease (CJD) and variant Creutzfeldt-Jakob disease (vCJD).

Testing steam sterilization cycle efficiency in medical settings

1. Biological indicator testing

Biological indicator testing is a quality control measure rather than an actual cycle. It involves using biological indicators, typically containing highly resistant bacterial spores, to confirm the effectiveness of steam sterilization cycles. This step is vital to ensure that sterilization processes consistently achieve the desired level of microbial kill, and helps verify the sterility of instruments and equipment.

2. Bowie & Dick test

The Bowie & Dick test is a specialized test used to evaluate the effectiveness of pre-vacuum steam sterilization cycles. It is performed daily to ensure that the sterilizer is functioning correctly and that air is being effectively removed from the chamber. Allows for early detection of sterilization cycle problems, preventing potential instrument contamination.

3. Vacuum test

The vacuum test is used to verify the effectiveness of the vacuum pump in steam sterilizers. It ensures that the vacuum system can efficiently remove air from the sterilization chamber, and helps you prevent incomplete sterilization.

Choosing the right type of steam sterilization cycle with Celitron’s help

Selecting the appropriate type of steam sterilization cycle for your medical facility involves careful consideration of the type of instruments and materials you sterilize, the volume of sterilization needs, urgency, available equipment, regulatory compliance, and the need for quality control measures such as biological indicator testing, Bowie & Dick tests, and vacuum tests.

By matching the right cycle to your specific requirements, you can ensure the reliability and success of your steam sterilization procedures, ultimately contributing to patient safety and infection control in your healthcare facility.

CONTACT US today and let Celitron’s team of experts help you choose a custom solution for your facility with a free quote!

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