STERILIZERS AND CONFIRM SUCCESS
WHAT ARE THE TYPES?
GRAVITY DISPLACEMENT STERILIZER The gravity (or "downward") displacement sterilizer uses the principle that air is heavier than steam.
-Within the sterilizer there is an inner chamber where goods are loaded and an outer jacket type chamber that injects steam forcefully into it.
-Any air in the inner chamber blocks the passage of pressureized steam to the surface of the goods and thus prevents sterilization.
-All the air must be removed because every surface of the supplies must be exposed to the pressurized steam to ensure sterilization.
-Therefore, the sterilizer is constructed in such a way that air is pushed downward by gravity (hence the name "gravity displacement sterilizer").
PRE-VACUUM STERILIZER The pre-vacuum sterilizer does not rely on gravity to remove air from the inner chamber. Instead, the air is pulled out of the chamber, which creates a vacuum in the chamber.
Steam is injected into the chamber to replace the air. This type of sterilizer offers greater steam penetration in a shorter time than the gravity displacement sterilizer.
FLASH STERILIZER The flash sterilizer has traditionally been used in the operating room and in other areas of the hospital to quickly sterilize items that are unwrapped.
It has been common practice to flash sterilize any instrument that had become contaminated during surgery.
HOW DO CONFIRM STERILIZATION?
- A chemical monitor is an object that is treated with material that changes its characteristics when sterilized.
This may be in the form of special ink that is impregnated into paper strips or tape and placed on the outside of the package, or it may be a substance that is incorporated into a pellet contained in a glass vial.
- The chemical responds to conditions such as extreme heat, pressure, or humidity but does not take into consideration the duration of exposure, which is critical to the sterilization process.
- Another monitoring method used to evaluate the steam sterilizer is the combined temperature time graphs that are installed within the control panel of the sterilizer. These graphs provide a permanent written record of all loads that have been processed.
- The surest way, to determine the sterility of given item, is with the use of biologic controls.
A highly resistant, nonpathogenic, spore-forming bacteria, is used as indicator. Contained in a glass vial or a strip of paper.
This is placed in the load of goods, to be sterilized.
For steam sterilization, the dry spores of the bacteria Bacillus Stearothermophilus are used.
The gas sterilization process uses the bacterium Bacillus Subtilis.
The vial or strip is recovered at the end of the sterilization process and cultured.
This process is time consuming and the results method of testing the efficacy of a sterilization process. Biologic controls should be administered at least once weekly. If feasible, they should also be used whenever an artificial implant or prosthesis is sterilized and the item withheld from use until the results are known to be negative.
ANY questions be sent to drmmkapur@gmail.com
All earlier posts are stored in archives for access and review
Friday, August 20, 2010
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.
Any questions be sent to drmmkapur@gmail.com
All earlier posts are stored in archives for your access and review
- 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.
Any questions be sent to drmmkapur@gmail.com
All earlier posts are stored in archives for your access and review
Friday, August 6, 2010
METHODS OF STERILIZATION 2
STERILIZATION BY HOT-AIR OVENS:
These are thermostatic controlled ovens, with an electric heating element, similar to a domestic electric oven.
- Instruments to be sterilized are heated to 160 degree C (320 degree F) for 1 hour.
- Sterilization is achieved, but it is not suitable for rubber or plastic instruments.
- In hospital has been used for sterilizing powders and petroleum products and sharp delicate instruments
The efficiency of dry heat sterilization depends on the initial moisture of the microbial cells, but all microorganisms are killed at 160 degree C for a hold time of not less than 2 hours.
The main advantages of dry heat sterilization are its ability to treat solids, non-aqueous liquids, grease/ointments and to process closed (airtight) containers.
Lack of corrosion is important in the sterilization of non-stainless metals and surgical instruments with fine cutting edges.
WHAT ARE AUTOCLAVES?
This is the most efficient method of sterilizing instruments, packs and dressings, and is suitable for most materials.
An autoclave is basically a pressure cooker and in fact, there is no reason why a domestic pressure cooker should not be used to sterilize instruments in a small clinic.
The small autoclaves produced for the doctor's surgery offer a choice of temperatures, pressures and sterilizing times:
The highest temperature that can be reached by boiling water at sea level in an open vessel is 100 degree C.
With increased pressure, the water can be raised to much higher temperatures before it boils, e.g., at a pressure of 0.35 kg per cm2 (5 p.s.i.) the temperature reaches 105.5 degree C: at 0.7 kg per cm2 (10 p.s.i.). 115 degree C; and at 1.05 kg per cm2 (15 p.s.i.) the temperature will reach 121 degree C, etc. In a sterilizer chamber (autoclave) which has been well exhausted of air the steam entering promptly fills the free spaces surrounding the load.
As steam contacts the cool outer layers of the fabrics a film of steam condenses, leaving a minute quantity of moisture in the fibres of the fabrics.
Air contained in the fabric interstices, being heavier than steam, is displaced by gravity in a downward direction, and the latent heat given off during the process of condensation is absorbed by that layer of the fabrics. fig 2.15
The next film of steam immediately fills the space created when the first film condensed into water, and it does not condense on the outer layer of the fabrics but penetrates into the second layer, condenses and heats it.
This process continues until the whole load is heated through and no further condensation occurs, the temperature within the pack remaining at that of the surrounding steam.
Any questions be sent to drmmkapur@gmail.com
All posts are stored in archives for your access and review
These are thermostatic controlled ovens, with an electric heating element, similar to a domestic electric oven.
- Instruments to be sterilized are heated to 160 degree C (320 degree F) for 1 hour.
- Sterilization is achieved, but it is not suitable for rubber or plastic instruments.
- In hospital has been used for sterilizing powders and petroleum products and sharp delicate instruments
The efficiency of dry heat sterilization depends on the initial moisture of the microbial cells, but all microorganisms are killed at 160 degree C for a hold time of not less than 2 hours.
The main advantages of dry heat sterilization are its ability to treat solids, non-aqueous liquids, grease/ointments and to process closed (airtight) containers.
Lack of corrosion is important in the sterilization of non-stainless metals and surgical instruments with fine cutting edges.
WHAT ARE AUTOCLAVES?
This is the most efficient method of sterilizing instruments, packs and dressings, and is suitable for most materials.
An autoclave is basically a pressure cooker and in fact, there is no reason why a domestic pressure cooker should not be used to sterilize instruments in a small clinic.
The small autoclaves produced for the doctor's surgery offer a choice of temperatures, pressures and sterilizing times:
The highest temperature that can be reached by boiling water at sea level in an open vessel is 100 degree C.
With increased pressure, the water can be raised to much higher temperatures before it boils, e.g., at a pressure of 0.35 kg per cm2 (5 p.s.i.) the temperature reaches 105.5 degree C: at 0.7 kg per cm2 (10 p.s.i.). 115 degree C; and at 1.05 kg per cm2 (15 p.s.i.) the temperature will reach 121 degree C, etc. In a sterilizer chamber (autoclave) which has been well exhausted of air the steam entering promptly fills the free spaces surrounding the load.
As steam contacts the cool outer layers of the fabrics a film of steam condenses, leaving a minute quantity of moisture in the fibres of the fabrics.
Air contained in the fabric interstices, being heavier than steam, is displaced by gravity in a downward direction, and the latent heat given off during the process of condensation is absorbed by that layer of the fabrics. fig 2.15
The next film of steam immediately fills the space created when the first film condensed into water, and it does not condense on the outer layer of the fabrics but penetrates into the second layer, condenses and heats it.
This process continues until the whole load is heated through and no further condensation occurs, the temperature within the pack remaining at that of the surrounding steam.
Any questions be sent to drmmkapur@gmail.com
All posts are stored in archives for your access and review
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