A Practical Approach to Low Temperature Etyylene Oxide Gas Sterilization

PROPER Loading : During sterilization, depending on the requirement from various faculties, there is a tendency to overload the chamber or pack the material too densely ; thus impeding the path of contact for the E.O. gas with the medical device. Care has to be taken that the material to be sterilized is loaded in such a way so as to present ample space for the movement of gas within the material . If the packing material used has a plastic component, it is advisable to place each pack on its edge ;and in such a way, as not to stick to each other during the sterilization process.

GAS Absorbing Materials: When the sterilizer is loaded with material which have a tendency to absorb excessive amounts of E.O like latex gloves etc.; there is a possibility of the other material in the load getting exposed to lesser quantity of the sterilant gas . Hence, a healthy balance, has to be maintained in the load between the absorbing materials and the rest of the load. A sure way of knowing if the gas is being absorbed is the indication of pressure inside the
sterilizer getting reduced drastically during exposure period.

STERILIZATION INDICATORS : It has been noticed that many times it is the sterilization indicators – biological as well as chemical indicators – which present a failure though the batch has met all the parameters and has passed. The cause for failure can be due to:

Incorrect storage: The manufacturers mention the essential storage conditions . Normally Chemical indicators must be kept away from direct light and excessive temperature. Biological Indicators must not be stored in a refrigerator and should be kept in a safe place away from direct sunlight and in normal room temperatures.

After Expiry usage : The manufacturer mentions an expiry date especially for biological indicators . If the product is used after this date, there may be an error, in the results obtained.

Incorrect handling and process during incubation : The process of incubation has to be properly understood as per the manufacturers specifications. Each manufacturer mentions the procedure regarding incubation and testing methods and these procedures should be followed precisely. Using biological indicators in strip form; though a cheaper option, may lead to false results due to the improper handling of the strips. Hence using self contained vials is a better and practical alternative.

Quality of the indicators : The quality of the indicators is also sometimes suspect. If an indicator repeatedly shows wrong results despite the contrary, it is advisable to change the manufacturer or the type of indicator used.

Overall, it is advisable to read the technical specifications given by the manufacturers and follow them precisely to get the best results.

OPERATING PERSONNEL: Due to the unprecedented growth in the number of hospitals, many hospitals and healthcare facilities find themselves either understaffed or without properly trained personnel. It is essential that personnel who operate the EtO sterilizers have a complete knowledge of the operation of the sterilizer and the related safety issues. In our country, due to the various languages in various states, there is a necessity for the personnel to be trained correctly and if possible in their own language. Retraining of staff should also be considered from time to time and proper records of the cycles taken, maintenance schedules and sterility testing records should be maintained.

CONCLUSION: When considering buying a new E.O. gas sterilizer or even replacing your existing one, it is helpful to consider the following points :

Need : Every hospital may not have the need for an E.O gas sterilizer and steam autoclaving maybe adequate for the needs of the sterilization department. However, hospitals having O.T.s and expensive re-sterilizable surgical items or medical devices should consider going for an EtO gas sterilizer.

Application : Another important factor is the actual dimensions of the unit ; for eg. If the sterilizer is primarily used for Cardiac Cath lab applications then the depth of the sterilizer should be considered critical ; as the catheters which are to be resterilized have extended life when sterilized straight; instead of in coil form.

Safety: It has to be ascertained whether the sterilizer is operating in total vacuum or is a combination of vacuum and pressure. Pressure based models normally use mixtures of E.O and inert  gases. In such sterilizers, if leakage takes place, there is a definate chance for the gas to leak out as the gas inside the chamber is under pressure. This tends to make them unsafe . It also increases the sterilization time and since the sterilizer uses a mixture of gas using cylinders ; there is also the issue of transportation of cylinders, handling, storage and the costs for all these. As E.O gas does not mix very well with inert gases, mixtures of E.O also have the issue of stratification of gases and the sterilization cycle may or may not receive the correct dosage for every cycle. This may cause failure in the cycle especially towards the last
15% of the gas left in the cylinder.

Cost: The initial capital cost and the per cycle running cost have to be taken into consideration. With the increasing competitiveness in the healthcare industry, the running per cycle cost also plays an important role in the selection. The cost is also related to the type of sterilizer; whether, manually operated ; semi- automatic or automatic.

It is equally important that the cost of consumables be ascertained prior to placing an order. Imported sterilizers use imported gas cartridges which are not only expensive but many times in short supply and the prices fluctuate with currency fluctuations.

In gas diffusion technology, there is a much higher cost for the consumables as the parts are packed in bags, and each of these bags have to be provided with a separate gas cartridge, humidifier, indicator and a special packing bag. This increases the cost per cycle for the same amount of load by more than 700%.

Consumables: When choosing a sterilizer, it is essential to know if the company has the capacity  to regularly supply consumables required for the daily batches and spares needed for the sterilizer in case of any malfunction.

Maintenance & Service: The sterilizer manufacturer should train the user in the regular maintenance, that is required for the upkeep of the machine. He should have proper service facility and trained technicians who can sort out problems quickly and effectively. He should be able to offer quick service to ensure minimum downtime.

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