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Infection Prevention
Plasma or Ozone: Which Is Better For You?
Nancy Chobin
Publish Date: October 10, 2007   |  Tags:   Infection Prevention

Sterilizing an endoscope that's sensitive to heat and moisture in a steam autoclave could damage the device. Considering what we pay for endoscopes, we want them to last for a long time. Steam may still be the standard for sterilization, but we may start looking for less distressing techniques to treat our high-tech devices.

The new low-temperature sterilizers may seem like an attractive alternative to steam in these situations, but it's not as simple as switching one system for another. The two leading low-temperature sterilization technologies - plasma and ozone - have their advantages, but they may not be able to accommodate the items that are commonly used in your facility. Here's what you should know to decide which one is the best choice for your center.

Pros and cons on both sides
Ethylene oxide, the old standard for low-temperature sterilization, isn't really feasible for most surgery centers. It's toxic (OSHA classified it as a carcinogen), has a very long processing time (12 to 16 hours) and takes a large inventory of items to make it cost-effective. Liquid chemical sterilizers such as peracetic acid are only effective while wet, so you must use the device immediately after it's processed because you can't package it and use it for a later procedure. Compared to these, both low-temperature gas plasma (LTGP) and ozone are likely to be better, more practical choices for your facility.

Both offer low-heat sterilization through a gentle process. LTGP works by using a cartridge containing multiple doses of a small amount of hydrogen peroxide, which is vaporized and turned to plasma by radio frequency energy to kill microorganisms; during the process it never goes above 122 degrees. An ozone processor combines the microbicidal properties of ozone gas with water vapor, and it stays at about 95 degrees.

One of the main differences is the time it takes to run a cycle. LTGP processing takes about 28 to 50 minutes, depending on the specific sterilizer model and the cycle selected. In contrast, ozone typically takes about four-and-a-half hours. Exactly how many devices are sterilized during this time depends on the size of the sterilizers. While LTGP sterilizers are available in several sizes, ozone sterilizers tend to be very large. Furthermore, when comparing costs, it is important to consider the turnaround time for instruments; the longer the turnaround time, the more instrumentation you'll need.

But ozone looks better when you compare the processing costs. It costs less than a dollar to run an ozone sterilization cycle because the machine only needs electricity and water. A plasma cycle can cost about $8 to run because each use requires a dose of concentrated hydrogen peroxide.

Staff safety is not much of a concern here because both of these systems are environmentally sound. After a cycle, they only emit water vapor and oxygen. While hydrogen peroxide is associated with skin and respiratory irritation, staffers never have to touch the substance if they use a cassette.

What stays out of the new sterilizer
How much of a role an adjunct sterilizer will have in your facility depends on how many of your instruments are compatible with its technology. It's important to consult your owner's manual or ask the vendor about some of the high-end devices such as endoscopes. When you do this, you'll often find that LTGP is becoming the treatment of choice for flexible endoscopes because ozone sterilizers only have FDA approval for stainless steel instruments, hinged instruments and instruments with rigid stainless steel lumens.

The standard LTGP is the method of choice for rigid scopes, cameras, fiber-optic cables, defibrillator paddles, electrocautery equipment, endoscopic instruments, laryngoscope blades, trocar sheaths, cryoprobes, laser handpieces, fibers and accessories, and dopplers.

Sometimes the answer can be as simple as considering the length of the lumens. For example, you can't put anything with an inside diameter of more than 0.9mm and a length of less than 485mm in an ozone sterilizer. In some plasma sterilizers, similar limits apply to instruments with stainless steel lumens wider than 2mm and shorter than 400mm. There are several other combinations of diameter and length between these extremes.

Some of the other limitations for LTGP processors are:

  • any device with dead-end channels or lumens;
  • devices that do not meet the lumen claims for diameter or length, as established by the manufacturer;
  • cellulose-based materials such as cotton, paper or gauze;
  • paper load control stickers unless they are plastic or Tyvek;
  • traditional adhesive labels such as dust cover labels; and
  • instruments or devices labeled specifically for gravity displacement sterilization.

Ozone processors have similar limitations, including:

  • latex;
  • textile fabrics; and
  • glass or plastic ampoules.

It's important to note that neither LTGP nor ozone is recommended for liquids or implants.

As with all sterilization processes, you must thoroughly clean (according to the device manufacturer's instructions) and dry all items before placing them in the LTGP or ozone sterilizers.

Accounting for cost and space
If your facility uses enough compatible devices to make either an LGTP or an ozone sterilizer feasible, it's time to consider what place it would have in your budget and sterilization room. A quick look at the list prices will give you an idea of which is more expensive, but to truly calculate the costs you have to account for:

  • the installation costs for plumbing and drains;
  • the installation costs for the oxygen system (you can't connect this to the facility's oxygen system; it must be an independent system)
  • the ongoing costs for parts such as water filters;
  • the costs per sterilization cycle; and
  • the training costs, in terms of the amount of time it'll take for staffers to become competent with this system.

An ozone sterilizer is about the size as a refrigerator, but plasma sterilizers are compact and easy to move around. And while ozone sterilizers need to be connected to a water source, electricity and oxygen, plasma sterilizers only need an electrical connection. If the person who handles the engineering or construction in your facility makes the effort to work closely with the vendor, you should encounter very few problems getting the most out of your system.

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