Sterilization With Saturated Steam: General Concepts - Gima H100 Instrucciones Para El Uso

Autoclave GIMA H100 automatic
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STERILIZATION WITH SATURATED STEAM :
GENERAL CONCEPTS
After many years of application, experience has shown that all the differen kinds of sterilization are reliable.
But the most effective and safest way to obtain a complete asepsis is certainly the treatment in autoclave
with water saturated steam (this is the common way used in hospital).
The working of the autoclave is regulated by the Test of Boyle-Mariotte which binds pressure, temperature
and volume.
The autoclaves with distilled water easily sterilize thanks to the perfect distribution of heat, the action of
saturated steam, which brings about the heat exchange with the material to be sterilized (latent heat of water
evaporation is extremely high: 539 at 100°C, 526 at 120°C, 519 at 130°C).
The essential reason for sterilizing through water saturated steam in pressure is that all the instruments,
either liquid or solid, must be treated at the requested temperature for the right time. Pressure itself does not
contribute to lethal process, but it just increases latent heat of water evaporation.
When steam comes into contact with any other colder material or body, it yields its quantity of heat by
condensing and thus increasing the object temperature. In steam condensing on microorganisms (owing to
the difference in temperature) this heat is integrally given with devastated effects on microbic cells. This
action goes on till there is a thermal equilibrium, then there is no more heat exchange and further condensing.
We can thus say that sterilization takes place in an acqueus fluid. From this introductory statement two
important factors come: first, superheated steam must be avoided; second, all air must be excluded.
Superheated steam or steam heated above its usual temperature in connection with its pressure must be
avoided for the following reason: although condensing tekes place during the initial phase of heating, then it
vaporizes again and the sterilizing process becomes a process of dry heat, whose conditions are different and
sterilizing temperature is higher and time is longer.
Air must be completely excluded, so that air pockets or layers are avoided, which compromize the effective
steam penetration and the right heat exchange. In fact a content of 50% air increases seven times the necessary
time to kill spores and time increases 11 times in presence of 100% air.
With water steam heating process is not immediate in any case, and needed time to reach thermal equilibrium
varies according to the size of the autoclave, the quantity and quality of the material to be sterilized.
With liquids or materials for surgical dressing and glass articles, where penetration is difficult or heat capacity
is high, time is important and you must consider it in the treatment cycle.
Scientific European and American Community have fixed and defined three temperatures, 115°C, 120°C
and 134°C and relative exposures for different materials and their resistance to temperature. Treatment at
105°C has been recognized effective with appropriate exposure, to be used for disinfection of thermolabile
materials which have obviously no direct contact with patients.
Cycle at 125°C for 15 minutes of sterilization is a middle cycle for sterilization of any metal instruments.
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