1. Laboratory equipment
Lecture (5)

2. Autoclave
Sterilization:  is the process by which all living micro-organisms both pathogenic and non-pathogenic including spores are killed.
Autoclaving is the process of moist heat sterilization, in which micro-organisms are exposed to steam under saturated pressure.

3. Physical Methods for sterilization
Heat – is the earliest, the safest and surest method of sterilization. It may be dry (hot air ovens infra red conveyor ovens) or moist (steam).

4. Dry heat, at normal atmospheric pressure.
Hot air ovens – these are electrically heated and usually with an internal fan to provide and even distribution of heat. Sterilizing time is one hour at 160ºC. This is suitable for ophthalmic instruments, glassware and sealed jars.
Infra red conveyor oven – items are passed on a conveyor through a tunnel heated by infra red elements. The infra red radiation is lethal so it is not commonly used now days.

5. Moist heat, at a raised atmospheric pressure
Steam autoclave (steam under pressure) Steam sterilization is the most inexpensive and effective method of sterilization.
Steam under pressure permits permeation of moist heat to porous substances by condensation and results in destruction of all microbial life.
This is the usual method of sterilizing surgical instruments, dressing, drapes, swabs, laps sponges and culture media.

6. WHAT IS AN AUTOCLAVE?
An autoclave is a closed chamber in which items or objects are subjected to steam at high pressures and temperatures above 100ºC.
Steam is a more efficient method of sterilization than air at the same temperature.
If air is present in the sterilizing chamber, a satisfactory temperature will not be achieved and pockets of air may prevent penetration of the load of articles by the steam. The air must therefore be removed.

7. ADVANTAGES
Destroys micro-organisms more efficiently than dry heat and therefore a shorter exposure at a lower temperature is possible.
Porous materials can be sterilized without damage.
Equipment or components of rubber and certain plastics such as nylon and pvc.

8. What can be autoclaved Surgical Instruments Glassware
Plastic tubes and pipette tips
Solutions and water
Animal food and bedding
Waste

9. TYPES OF AUTOCLAVES DOWNWARD DISPLACEMENT AUTOCLAVES
Air is removed in two stages and sterilization is effected by an atmosphere of pure steam.
The minimum exposure time is required for sterilizing instruments is 50 minutes at 131ºC or 60 minutes at 136ºC. Bulky dressings, surgical swabs and surgical drapes require exposures two or three times as long.

10. HIGH VACCUM / HIGH PRESSURE AUTOCLAVE
Air is removed by powerful pump. Steam penetrate the load instantaneously and very rapid sterilization of dressings, instruments, lap sponges and packs is possible in 15 to 30 minutes at 134ºC.

11. THE STEAM STERILIZATION PROCESS WHICH IS DIVIDED IN TO FIVE DISTINCT PHASES:
PHASE I
The loading phase - in which the objects or items are packaged and loaded in the sterilizer.
PHASE II
The heating phase – in which the steam is brought to the proper temperature and allowed to penetrate around and through the objects in the chamber.

12. PHASE III
The destroying phase – or the time-temperature cycle, in which all microbial life is exposed to the killing effect of the steam.
PHASE IV
The drying and cooling phase – in which the objects are dried and cooled, filtered air is introduced into the chamber, the door is opened and the objects are removed and stored.

13. PHASE V
Testing phase - in which the efficiency of the sterilization process is checked.
All mechanical parts of sterilizers, including gauges, steam lines and drains, should be periodically checked by a competent engineer.

14. Working of autoclave
Steam enters the chamber jacket, pass through an operating valve
Enters the rear of the chamber behind a baffle plate

15. It flows forward and down ward through the chamber and load, existing at the front bottom.
Pressure regulator maintains pressure in the chamber and in jacket at a minimum of 15psi,the pressure required for steam to reach 121°C

16. Some causes of failure to produce a sterile load are:
Faults in the autoclave and the way it is operated
It maybe:
Poor quality steam
Failure to remove air and condensate
Faulty gauges and timings
Leaking door seals

17. Errors in loading Examples: Large packs
Excessive layers of wrapping materials
Over packing