Sterilisation of medical equipment

Ethylene oxide, or EtO as it is often referred to, has been used as a sterilant for more than a century. It has stayed in favour in hospitals over this time because it kills a wide range of pathogens, it can sterilise complex shapes and, unlike gamma radiation, has no detrimental effect on the items being treated. It is overwhelmingly the leading choice for the sterilisation of medical devices and if you look on the packages of devices for use in surgery perhaps 70% will contain the statement 'Sterile EO'. EtO is very good at reaching inside all the corners of complex geometric shapes and will also penetrate most plastics. In other words, long, narrow lumens and complicated shapes present no problem to EtO.

With regard to economics, the use of EtO sterilisation tends to be more expensive than steam autoclaving which is also ubiquitous in hospitals, clinics, veterinary practices and dentists. However, EtO comes into its own with items that will be damaged or destroyed by autoclaving, such as items that contain plastic, rubber or electrical components. Examples might be endoscopes and various laparoscopic devices. It it is also favoured for equipment that contains optics or cutting and grinding edges, such as devices for ophthalmic surgery.

Additionally, investment in EtO sterilisation equipment can save the hospital money when it is used to sterilise procedure kits containing bandages and swabs that can be purchased non-sterile at lower cost.

Product selection

Ethylene oxide for sterilisation in medical applications in hospitals and clinics is most commonly supplied as a mixture of 9% EtO in a balance of carbon dioxide. At Coregas, we refer to this product as Biosterile 9. The benefit of this gas mixture is that when it is introduced into the sterilisation chamber the gas mixture remains non-flammable. This can significantly reduce the cost of the sterilisation chamber equipment because it eliminates the need for the chamber to be constructed and certified as explosion proof.

A mixture of 90% EtO with 10% carbon dioxide has also been common in some industrial sterilisation applications. The benefit of operating at this high EtO concentration is that the pressure in the sterilisation chamber can be vastly reduced and this, in turn, can reduce the cost of the sterilisation chamber. It is also possible, and increasingly popular, to use pure EtO for sterilisation in these large scale applications and in this case nitrogen will be used to create headspace pressure in the EtO container to propel it into the sterilisation chamber.