Autoclave validation is required to get effective Sterilization to ensure good product quality and also sterility of glassware and media used for analysis is very important for product manufacturing. Ineffective autoclave validation may cause deviation in sterility and it may lead to a false result.
So data loggers play a very important role in recording the temperature at a different validation stage with the help of Probes. The number of Probes used depends on the size of the autoclave being validated.
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The Number of Probes used for Autoclave validation
There are lots of regulatory guidelines on autoclave validation, but Among the different Guidelines, most do not define the number of Probes used in autoclave validation.
During the Slow to Heat study, biological indicators are not mandatory. There is a need to ensure that one should load one load at a time in an autoclave and place more than 12 numbers of temperature probes in the load.
This is because if the load items are more or, the autoclave chamber size is more than 1000L, then we should place > than 12 probes.
Here while placing the probes, special attention is required to the selection of location, which shall cover all corners, the bottom/ upper central part, mid-central part of the autoclave, based on the load items, representative items of a load.
Autoclave validation process
- For effective Autoclave validation place the temperature probes, during this a programmed cycle should be applied to the load by simultaneously operating the Validator (Datalogger). One should calculate the F0 value (Formula for F0S10^((Measured temperature- 121.1°C)/10))x time interval) of dwell time to comply with all requirements.
- First, need to list out the number of loads to be validated in the autoclave and categorize it into porous, non-porous, and mixed loads. It is based on the nature of the load items, which cover rubber bung, silicon tube, cartridge filter, and HDPE bottle. It is important to note that heat penetration is very difficult in a porous load. After the categorization of the loads, develop the heat penetration cycle, which is known as slow to heat cycle or hardest to-heat cycle, or cold spot identification cycle in load.
- Here we have to use the same cycle parameters for the slow to heat and final run for all non-liquid loads.
- Based on the type of load, items in a load, post pulse rate, and a number of post pulse can vary because the post parameter will not have any impact on heat penetration or SAL.
- All slow to heat runs for the different loads should be performed in the cool chamber. After the Slow to Heat study, all loads must be validated for three consecutive successful runs to prove the consistency, reliability, and SAL in the biological indicators at 10 cold spots.
- Now for the worst case for the minimum load validation/ Sterile assurance level/ Variable position validation, where one particular load can be considered as a worst-case for the above-mentioned validation out of 4 loads. one will need to perform one half cycle hold time, for instance, the full cycle time is 30 minutes so that 15 minute hold time will be half cycle. There is also a need to adopt the heat penetration study with biological indicators on the worst caseload to prove the 12-log reduction or Sterility Assurance Level (SAL) in full-cycle hold time.
Things to avoid while autoclave validation
- Avoid touching of Thermocouple with the wall of the autoclave because on walls have a higher temperature as compared to the chamber.
- The Thermocouple must keep in the right position, as mentioned in the image.
- The Thermocouple should follow BS4937 standard part 4 (Nickel-chromium /Nickel-Aluminium) or part 5 (Copper-constantan).
- The width of the Thermocouple wire should not be more than 0.7 mm.
- The temperature between the Thermocouple must be controlled. It should not be more than 3⁰C. For example, the should be in between 121⁰C to 124⁰C pressure must be within 15 to 18 lbs for 15min cycle.
The 4 parameters of the autoclave process are pressure, steam, temperature, and time.
“F0 ” is defined as the number of equivalent minutes of steam sterilization at 250°F (121°C) delivered to a load
Minimum 12 and if the load items are more or, the autoclave chamber size is more than 1000L, then we should place > than 12 probes.
because at 121°C the lethality rate & saturated steam point is optimum.
A cold spot is defined as any point where the temperature indicator is situated that does not achieve the minimum sterilization temperature of 121°C throughout the sterilization temperature hold time.
The time between the first sensor reaching the specified temperature and the end sensor reaching the set temperature is referred to as the lag time.
Efficacy of the autoclave process may be achieved by using these three indicators: (1) Physical: pressure and temperature recording devices 2) chemicals like indicators 3) biological: Bacillus stearothermophilus spores are commonly used, due to heat resistance properties.