Low temperature plasma sterilization
Some medical devices are made of materials that can withstand the high temperatures of a sterilization autoclave (134°C) : metals, glass, polymers such as PEEK, polypropylene, acetal copolymers or polyphenylsulfone, etc.
But innovations in the medical device have led to the use of more fragile materialseither that they cannot withstand heat (heat-sensitive materials), or that they are not resistant to sterilization products (chemical-sensitive or radio-sensitive materials). They are called fragile medical devices.
Aurora plasma sterilization meets the needs of manufacturers of these medical devices : low temperature sterilization that does not damage the materials. Low temperature for medical devices is below 60°C.
Low temperature sterilization in large volumes
Low temperature sterilization is used for two purposes. The most important applies to ingle-use medical devices. The other applies to devices that can be reused in healthcare centers.
The first is required from manufacturers of fragile medical devices, which must provide patients with pathogen-free devices with a probability of less than one in a million cases.
The most common low temperature sterilization (LTS) techniques for single-use devices are gamma irradiation and ethylene oxide fumigation.
X and beta rays, nitric oxide, peracetic acid and supercritical CO2 are other modes of industrial low temperature sterilization. But their use is very limited in the sterilization industry.
Industrial sterilization is carried out at 75% by subcontracting, due to the complexity and dangers posed by the processes mentioned.
Low temperature sterilization per unit
The other type of low temperature sterilization applies to reusable devices. It is the responsibility of the hospital or medical practice. It is sometimes subcontracted. In such reprocessing, only one to three devices are sterilized at a time.
There is a low temperature sterilizer model that uses ozone (O3) combined with hydrogen peroxide. The dangers posed by ozone to the human respiratory system render this solution unpalatable, even if the sterilization results are undeniable.
The most common low-temperature sterilization method in healthcare centers is vaporized hydrogen peroxide (VHP) sterilization. It consists of exposing the device to be sterilized to H2O2 in the form of vapor in an enclosure under primary vacuum (about one mbar). The enclosure is heated to around 55°C, depending on the VHP sterilizer models.
A single dose of hydrogen peroxide is used for an entire cycle. To this dose corresponds a certain mass to be sterilized. Manufacturers implement various means to overcome the hydrogen peroxide present at the end of the cycle. Questions remains about the validity of the concentrations. One model creates a plasma discharge at the end of the cycle, which is supposed to break down the H2O2 into water and oxygen.
True and False Plasma Sterilization
This use of plasma in HPV has given rise to an abuse of language. Some still speak of « hydrogen peroxide gas plasma sterilization » about this process. Now it is clear that this plasma does not sterilize anything. Hydrogen peroxide is the sterilizing agent.
The only true low-temperature plasma sterilization process in the care center is Aurora’s. Aurora exclusively uses an air gas plasma to sterilize medical devices. Aurora does not use any chemical agent to sterilize. From this point of view, Aurora differs from supercritical CO2 sterilization, which still uses H2O2 or peracetic acid as additives.
The benefits of low temperature plasma sterilization
Aurora plasma low-temperature sterilization has a first advantage over VHP. The plasma precursor gas, oxygen, is injected throughout the sterilization cycle. There is therefore no dose phenomenon to consider. There is as much plasma as injected oxygen.
To generate the Aurora plasma, the tank must reach a much higher vacuum than for the VHP. The vacuum for plasma is a secondary vacuum. During the vacuum descent phase, the device to be sterilized is purged of any liquid or gas. It is thus perfectly dry, with no risk of ice formation.
There is also no risk of condensation since the tank is not heated, and the injected oxygen cannot liquefy at such a pressure. There is therefore no concern of condensation of the sterilizing agent, contrary to what can happen in VHP, and which affects the effectiveness of this technique.
Excellent plasma penetration in long and thin tubes
Aurora Plasma also allows long narrow lumens to penetrate much farther than VHP. Indeed, due to its design, a VHP sterilizer will come up against the constraints of fluid mechanics to enter and exit a tube of more than 89 cm and 1 mm inside diameter. The Aurora plasma is not subject to this constraint, and it has demonstrated its effectiveness on tubes 5 m long and 1 mm in internal diameter.
With the Aurora plasma, no desorption phase or elimination of chemical residues is necessary at the end of a sterilization cycle. Indeed, the reactive species composing the plasma do not survive the interruption of the electromagnetic field which ignites the plasma. Simply cut off the radio frequency for the oxygen ions to recompose into harmless gases in the air.
And since the temperature reached during the plasma sterilization cycle does not exceed 40°C, operators do not have to wait for a temperature drop.