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By - Pauline W. Fallis,
Microorganisms need certain conditions in order to live and reproduce.
These conditions may include a specific temperature, moisture level, pH and
even osmotic pressure. Sterilization used in electrolysis is usually heat
based.
The most effective and widely used form of heat sterilization is steam
under pressure. The ability of air to carry heat is directly related to the
amount of moisture present in the air. The more moisture present in the
air, the more heat can be carried. Steam is one of the most effective
carriers of heat. For instance, when you are cooking beef, like an eye of
the round. It can be tough when roasted in a covered pan in the oven, but
just add a little water in the bottom of the pan, and you will find that
the meat will be tender. The temperature is the same and the time of
roasting is the same, but the result is different. Now add another
parameter, add pressure. By putting this same roast in a pressure cooker
you can reduce the time it takes to cook this roast by at least three
quarters, and you still get just as tender a finished product.
Now let us look at the instruments used in your practice. When clean
instruments are subjected to steam under pressure, the protective outer
coat, or layer or microorganisms is first softened, which allows heat to
quickly coagulate the sensitive protein material within, thus effectively
killing the organisms.
There are four conditions that must always be met in order for steam to
successfully sterilize. The steam must contact all surfaces of the
instrument, because steam is a surface sterilant. The steam must make
contact with any microorganisms in order for the sterilization to take
place. The second condition is temperature. The steam within the
sterilization chamber must be at least 121 degrees centigrade (250 degrees
Fahrenheit) throughout the exposure time so that sterilization can take
place. Steam will transmit its thermal energy to the item so that both the
steam and the item reach the same temperature. The third parameter is
exposure time. There is correlation between the time and temperature
called time/temperature ratio. The higher the temperature of the steam the
shorter the time required to achieve sterilization. The exposure time at
121 degrees centigrade for sterilization to take place is 12 minutes. This
does not include the conditioning (heating up), or exhaust time. Total
cycles take from 30 to 45 minutes. The final condition is moisture. For
successful sterilization steam must be saturated, which means that it
reaches a humidity of 100%. When all these parameters, contact,
temperature, exposure time and moisture are met, successful sterilization
takes place.
An autoclave is another word for a steam sterilizer. All autoclaves work on
the principle that when a chamber is closed the steam replaces the air
which is exhausted out. There are several types of table top autoclaves
available. There is a model with a chamber of one or two cubic feet for
sterilizing small sets of instruments as well as small bowls and other
small equipment. Distilled water is placed in the bottom of the chamber and
is heated to create steam. As the pressure within the chamber increases
until the desired temperature is reached, sterilization can then take
place. There is also a model that uses a cassette that acts as both the
steam chamber and the package. Distilled water is placed in a container
which feeds into the machine, which is then heated to create steam, which
is then fed into the cassette. As the steam fills the cassette, the
pressure increases and the heat increases until the desired temperature is
met. Just like the others, distilled water is used which is placed in the
bottom of the chamber. A basket is inserted where instruments needing
sterilization are placed. The water is heated just like the others to
produce steam, which as the temperature increases, increases the heat until
the exposure temperature is reached.
In this column, in the last several issues of the COPE newsletter, the
reprocessing of instruments has been discussed. Subjects covered were, why
is sterilization important, the procedure for cleaning instruments, and all
of the methods of sterilization and disinfection. When an item needs to be
sterilized either between clients or at the time of use, they can be
sterilized by steam under pressure (by the autoclave), dry heat or
chemicals (by vapour or liquid). In most cases dry heat or chemical
sterilization are used only if the item is moisture or heat sensitive. Of
all of the methods of sterilization available, the method of choice is
still steam under pressure. Autoclaving is still the one that is most
reliable, easy, and in the long run, the most inexpensive.
INFECTION CONTROL ARTICLES
- PREPARING FOR THE PATIENT/CLIENT
Spring 2001, Volume 8, Number 1
- PREVENTING INFECTION FOR ELECTROLYSIS
Fall 2000, Volume 7, Number 2
- INFLUENZA
Spring 2000, Volume 7, Number 1
- MICROORGANISMS AND INFECTIOUS DISEASE
Summer 1999, Volume 6, Number 2
- BLOOD BORNE INFECTIOUS DISEASES AND PERSONAL PROTECTION
Spring 1999, Volume 6, Number 1
- MICROORGANISMS & INFECTION
Fall 1998, Volume 5, Number 2.
- BIOLOGICAL TESTING OF YOUR STERILIZATION PROCESS
Spring 1998, Volume 5, Number 1
- STEAM STERILIZATION
Fall 1997, Volume 4, Number 2
- CHEMICAL STERILIZATION
Spring 1997, Volume 4, Number1
- DRY HEAT STERILIZATION
Fall 1996, Volume 3, Number 2
- STERILIZATION
Spring 1996, Volume 3, Number 1
- IS YOUR USE OF NEEDLES SAFE IN YOUR PRACTICE?
Fall 1995, Volume 2, Number 2
- PREPARING INSTRUMENTS FOR STERILIZATION
Spring 1995, Volume 2, Number 1
- WHY ARE GLASS BEAD STERILIZERS NOT RECOMMENDED FOR USE IN ELECTROLOGY?
Fall 1994, Volume 1, Number 2
- STERILIZATION: HOW, WHEN, AND WHAT WITH
Spring 1994, Volume 1, Number1
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