In addition to the high temperature, steam must be saturated so that it will quickly release heat through condensation when it comes into contact with a cool object.
Sterilization will not occur unless all air is eliminated from the chamber at the beginning of the process and periodically throughout sterilization.
The packaging of supplies and loading of the sterilizer must be done so that steam comes in contact with all areas or surfaces of the items being sterilized.
Flash sterilization is defined as the sterilization of unwrapped items in a gravity displacement or prevacuum sterilizer with recommended minimum exposure times and temperatures.
Steam sterilization by this unwrapped method is not recommended. It should be used only for emergency sterilization.
A steam sterilizer, also know as an "autoclave," is a pressure-type vessel with a door or cover, valves to control the entry and exit of steam and air, and monitoring devices to allow the operator to observe conditions inside.
It is designed to hold items and allow steam under pressure to penetrate these items. Steam sterilizers are available in many sizes, ranging from portable countertop to the fixed room-size sterilizer.
Two of the most common types of steam sterilizers used in the Navy are the gravity displacement and prevacuum sterilizers.
GRAVITY DISPLACEMENT. - Once this sterilizer is loaded and the door is closed as shown in figure 10-10, steam is admitted through an inlet and the sterilization process begins.
A typical standard for steam sterilization is achieved at 250°F or 121°C after 20 to 30 minutes at 15 psi.
It is important to refer to the manufacturer's instructions for operation, since exposure times can vary according to the design of the particular sterilizer.
You should observe the following precautions when loading the sterilizer chamber:
Do not overload. The passage of steam from the top of the chamber to the bottom should not be blocked.
Place all packages on edges, with large packs at the bottom of the chamber, and small packages in an upper layer crosswise to the lower layer. This allows free passage of steam.
If mixed loads of metal items and linen are sterilized together, the linen is placed on the upper shelf and the metal items on the lower.
Articles that require the same amount of time and the same final steps should be sterilized together.
Enclosed fluids are sterilized separately because the pressure must be slowly released.
Load all packages at the same time when you are ready to sterilize.
A standard operation chart for the correct exposure period of all supplies should be prepared and posted for easy daily reference.
It is important to note that sterilizing conditions are based on temperature rather than on pressure. Effective steam sterilization and exposure time are measured from the moment the thermometer in the discharge line indicates the desired preset temperature. The pressure inside the sterilizer is not an indication of positive sterilization because other factors determine the pressure inside the sterilizer.
PREVACUUM STEAM STERILIZER. - The prevacuum steam sterilizer (fig. 10-11) was designed to help overcome the trapping of air in the chamber.
Trapping of air is one of the greatest dangers encountered when using saturated steam under gravity cycles. When errors are made by improperly packaging items or overloading the sterilizer chamber, cool air pockets may form resulting in items not being sterilized. The speed and efficiency of the steam sterilizer may be improved by removing air from the chamber with a powerful pump, creating a nearly perfect vacuum before steam is introduced into the chamber. This procedure allows fast and more positive heat to penetrate the entire sterilizer load. The improved sterilizer is referred to as the prevacuum steam sterilizer.
Full heating of the loads is faster in the prevacuum sterilizer than in the gravity displacement sterilizer. For example, wrapped instruments can be sterilized at 270°F (131°C) after 4 minutes exposure in a prevacuum steam sterilizer. Consult the manu- facturers instructions for specific details on operation and user maintenance information. The
Bowie-Dick type test was developed for prevacuum sterilizers to determine if the air has been removed from the chamber during the prevacuum stage.
Air must be removed so that steam can penetrate the load instantaneously. It must be understood that this is not a test for adequate exposure to heat in terms of time-at-temperature.
A commercially prepared Bowie-Dick type test can be used by carefully reading and following the manufacturers instructions. AllContinue Reading