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Sterilisation principles. WHAT IS STERILISATION WHY STERILISATION HOW TO STERILISE. Categories of instruments and specific requirements for use:. Clean / Disinfected High Level Disinfected Sterile. Cleaning, disinfection & sterilisation. Cleaning:
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Sterilisation principles • WHAT IS STERILISATION • WHY STERILISATION • HOW TO STERILISE
Categories of instruments and specific requirements for use: Clean / Disinfected High Level Disinfected Sterile
Cleaning, disinfection & sterilisation • Cleaning: • Removing of all visible dirt, dust or other foreign material • Decontamination (disinfection): • killing all vegetative microorganisms • Sterilization: • Killing all microorganisms, including spores
What is sterilisation? • Sterilization is the process where the goal is to reach a ‘sterile’ condition of the instruments • The keyword is ‘sterile’ • EN556 gives a definition of sterile: • “condition of a medical device that is free from viable micro organisms” • The scientific expression for ‘free from micro organisms’ is also defined in EN556 • The theoretical probability of a viable micro- organism present on the medical device shall be equal or less than one in a million.
Why sterilisation? • To kill all micro-organisms • To prevent cross-infection • To protect personnel and patient
Pasteur History of micro organisms • 1674: ‘Antonie Van Leeuwenhoek’ discovers great numbers of bacteria's • 1862: ‘Louis Pasteur’ a French biologist proves that: • Bacteria's multiply by dividing • Infection is ‘air born’ • Boiling kills the bacteria • 1870: ‘Henry Charlton Bastian’ English neurologist concludes that 100ºC is not killing all the bacteria • 1880: ‘Charles Chamberland’ manufactures the first autoclave to boil on more than100ºC
Various Micro Organisms • Animal-like: • Malaria and Bilharzias • Vegetable-like: • Mould (10 times the size of a bacteria) • Bacteria (10 times the size of a virus) • Bacillus or spores (high resistant bacteria) • Viruses: Needs “living” material to multiply
Multiplication of Micro Organisms • 0-7 ºC: Relatively no multiplication • 10-50 ºC: Ideal for the multiplication • 62-100 ºC: Most bacteria's die off • 100-134ºC: Spores die off at WET HEAT
How to sterilize Sterilisation methods Dry HeatOxidation of the micro organism SteamCoagulation of themicro-organisms Plasma-low temperature Chemical reaction Ethylene Oxide Chemical reaction
Autoclave principles • Pressure vessel • Generating steam inside the chamber • Controlling temperature and pressure • Holding time at fixed temperature
Pressure Temperature Time Main parameters
Saturated steam • Pressure - Temperature Relation: • 1.0 bar - 120 ºC • 1.1 bar - 121 ºC • 2.0 bar - 134 ºC • 2.2 bar - 135 ºC
Minimum holding time • Temperature - Time relation • 134 to 138 ºC - 3 Minutes • 121 to 124 ºC - 15 Minutes • 105 to 108 ºC - 2 Hours
Air & steam • Where there’s air, there’s no steam • Where there’s no steam, there’s no sterilization • Air obstructs the temperature from rising
Air removal • Since air is causing a problem, the air removal is an important part of the sterilization process • Two removal principles: • Gravity autoclaves • Pre-vacuum autoclaves
Gravity principle • Steam production in vessel • Steam rises and pushes up the air • Air escapes through a valve at the top of the vessel • Sterilization conditions are reached • Temperature and pressure are maintained for a fixed period of time • In gravity autoclaves 5-10% of air left
Pre-vacuum principle • Air removal through vacuum pump • Steam production or steam injection in vessel • Sterilization conditions are reached • Temperature and pressure are maintained for a fixed period of time • In pre-vacuum autoclaves 1% of air left
Process stages - vacuum 1 vacuum pulse
Arguments for steam sterilisation • Safe way to sterilize instruments • Safe for user • Possibility to wrap instruments • Relatively inexpensive
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