METHODS OF STERILIZATION 3

CHOICE of GOOD AUTOCLAVE & CYCLE




- A`quick' cycle would heat the water to 134 degree C (273 degree F) for 3.5 min. under a pressure of 30 1b/sq in.
- Slower cycle, more suitable for plastics, would heat the water to 121 degree C under a pressure of 15 1b/sq in 15 minutes.
- In practice, instruments are placed in the trays or in packs, the autoclave turned on, and left for the desired time.
- At the end of the cycle, the instruments are ready for use.
-They will be dry with vacuum and air outlet.

The main disadvantage of the smaller autoclave is that instrument packs cannot be sterilized as there is not a vacuum cycle to extract air and dry the packs.

However, most materials including rubber, plastics and metal can be readily sterilized, the only exception being sealed containers.
Steam is the gaseous form of water. If it is to sterilize effectively, by killing all spores:
- It must be at an appropriate temperature (which implies an appropriate pressure).
- It the chamber must be saturated with STEAM.
- Thus not be mixed with air, so it must displace all the air in the chamber of the autoclave.
- And, it must reach all parts of the load. If it contains droplets of water, it will soak into porous materials.

If no air is discharged, the bottom of the chamber may be much cooler, than the top.
As soon as the chamber of an autoclave is full of steam, at the desired temperature, and pressure, it must be held there, for a critical time-the holding time.
The standard holding time is 15 minutes, at 121 degree C, but you may need to vary it.

Single walled autoclaves are strong metal chambers with water in the bottom, like large pressure cookers. They have several disadvantages and may not be acceptable foe hospital use..

A good autoclave (with double wall & vacuum) is by far the most efficient method of sterilization for materials that will stand up to heat and moisture.
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