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  1. #1

    Default Autoclave F0 calculations

    Hello,

    Can anybody help with this dilemma.

    During PQ of the autoclave cycle one of the requirements is that the Fo specification must be met.

    We are using a Kaye 2000 which calculates the lethality. However, there is some confusion at what point the Fo is taken.

    1. Some suggest at the end of the exposure phase (end of 20 minute hold time)
    2. Some suggest at the end of the autoclave cycle, as the Fo is still accumulating. (The Kaye recording is stopped 25 minutes after the end of the exposure phase)

    Any suggestions

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  3. #2

    Default

    F0 = D121 x (log N0 - log Nt)

    where, F0 equals the number of minutes exposure at 121 degrees Celsius which would have the same lethal effect as an alternative designated autoclave cycle. N0 equals the initial contamination level (bioburden) and Nt equals the final or required contamination level (SAL) after t minutes exposure.
    Durga Prasad

  4. #3

    Default

    F0 = t x 10 T-121/Z.

    t= time in minutes at which product is at exposure temprature

    T= sterilisation temprature

    Z= A constant considered as 10 for steam sterilisation.
    Durga Prasad

  5. #4

    Default

    Thanks Durga,

    Useful information. However, its the actual time that is of concern. Our exposure is >121oC for 20 minutes. But as you are aware the some of the thermocouples even after 20 minutes exposure will still be above 121oC. So, for the Fo calculation do you only take into account the exposure phase (20 minutes) or (20 minutes exposure + the additional minutes) that the thermocouples are above 121oC.

  6. #5

    Default

    Exposure time is noted as time when Thermocouple reaches 121C.Once this temperature is reached, you have to expose the material of concern for 20 minits.
    Durga Prasad

  7. #6

    Default

    It depends on what you are trying to correlate to the Fo value. Are you trying to demonstrate that the entire cycle provided adequate lethality to destroy the BI or are you trying to demonstrate that the exposure phase provided adequate lethatlity to destroy the BI?

    For a PQ, I would start the calculation at the start of exposure and end at the end of exposure. I would then claim that the exposure phase provides an Fo of >20 minutes. That way I would have some wiggle room if an issue arrises during operations. For example, the exposure stops one minute short or dips during exposure. I would calculate Fo start to finish in operations.

  8. #7

    Default

    Quote Originally Posted by DURGA PRASAD View Post
    F0 = t x 10 T-121/Z.

    t= time in minutes at which product is at exposure temprature

    T= sterilisation temprature

    Z= A constant considered as 10 for steam sterilisation.
    Hi there, i think the right equation is as follows:
    "F0 = t x 10(T-121.1/z)" ..... In which 10 is to the power (T-121.1/z)

  9. #8

    Default f0 calculation

    Concept of F0 is very vast accoring to me if your autoclave cycles is based on F0 then you should consider exposure end F0 value as the final value which can be surely accumulated because after exposure you can not gurantee the temperature of each probe to be maintained up to end of cycle.
    while in case of time based autoclave cycle you should consider end F0 value as the final value which is achived during whole cycle.

  10. #9

    Default

    Hi Mike. I'm not certain your question was answered. You could continue to calculate F0 until the cycle stopped, however, the amount of lethality added below 100 C is negligible. We use Kaye Valprobes and they support this type of collection, I bet the Kaye 2000 does also. Mike

    Quote Originally Posted by mikey70 View Post
    Thanks Durga,

    Useful information. However, its the actual time that is of concern. Our exposure is >121oC for 20 minutes. But as you are aware the some of the thermocouples even after 20 minutes exposure will still be above 121oC. So, for the Fo calculation do you only take into account the exposure phase (20 minutes) or (20 minutes exposure + the additional minutes) that the thermocouples are above 121oC.

  11. #10

    Default

    Hi Mikey70,

    According to PDA Technical Report No. 1 - Validation of Moist Heat Sterilization Processes the PQ includes certain acceptance criteria. These are examples:
    - Minimum and maximum time above a specified minimum temperature measured with heat penetration probes.
    - Minimum and maximum total accumulated F0.
    - Minimum F0 at the end of the exposure phase.
    - Minimum and maximum pressure during exposure.
    - Correlation of temperature and pressure for saturated steam.
    - Minimum and maximum chamber temperature during exposure.
    - Maximum temperature or F0 variation between heat penetration probes.
    - Maximum temperature variation in temperature distribution probes.
    - Maximum equilibration time.
    - Minimum number of properly functioning probes.

    In other words, the PDA suggests taking into consideration the total process F0 (min. and max.), F0 at the end of the exposure phase, and F0 during the exposure phase only (max. variation).

    I hope this is useful.

    Regards,

    Enrique Riis

  12. #11

    Default Total Fo

    Fo is Fo, whether generated during exposure or after exposure. As noted in previous posts, it may be of value to understand / know the amount of Fo generated post-exposure (e.g. "wiggle room"). I typically build in "wiggle room" by requiring an additional amount of Fo in the acceptance criteria, and use the total Fo value.

    So, it depends on what one is trying to demonstrate...as long as the meaning of that value is stated in the summary report.

  13. #12

    Default

    It depends on what you are trying to correlate to the Fo value. Are you trying to demonstrate that the entire cycle provided adequate lethality to destroy the BI or are you trying to demonstrate that the exposure phase provided adequate lethatlity to destroy the BI? Autoklavai
    Laboratoriniai saldikliai
    Autoklavai
    Elektronines svarstykles
    Last edited by Autoklavai; 05-09-2012 at 06:10 AM.

  14. #13
    Validation Analyst
    Join Date
    Dec 2012
    Location
    Connecticut, USA
    Posts
    31

    Default Better Late then Never

    Quote Originally Posted by mikey70 View Post
    Hello,

    Can anybody help with this dilemma.

    During PQ of the autoclave cycle one of the requirements is that the Fo specification must be met.

    We are using a Kaye 2000 which calculates the lethality. However, there is some confusion at what point the Fo is taken.

    1. Some suggest at the end of the exposure phase (end of 20 minute hold time)
    2. Some suggest at the end of the autoclave cycle, as the Fo is still accumulating. (The Kaye recording is stopped 25 minutes after the end of the exposure phase)

    Any suggestions
    So I hope by now that you have figured out some answer to this delima. I would like to weigh in on this since I have recently helped a company develop new autoclave procedures with the assistance of some really knowledgable industry leaders. Speaking to your question specifically, you can set up the Kaye to record the lethality calculation based on the temperature set point so that it is calculated during the exposure period. The concern about having wiggle room in this should actually be addressed during the cycle development. What I have seen is the hold time being established with more than adequate overkill time. In an audit situation, it is easier to defend your claim of meeting the sterility standards by having your AF0 time for the platteau period when everything is within the temperature band. I would also implore you to research the often overlooked BS EN:285 requirements for equilibration as well. Just meeting the lethality requirements alone does not adequately demonstrate that you have control and that your load is sterilized. In the past few years the EMA has been clamping down on companies that are not meeting this.

  15. #14

    Default

    Quote Originally Posted by mikey70 View Post
    Hello,

    Can anybody help with this dilemma.

    During PQ of the autoclave cycle one of the requirements is that the Fo specification must be met.

    We are using a Kaye 2000 which calculates the lethality. However, there is some confusion at what point the Fo is taken.

    1. Some suggest at the end of the exposure phase (end of 20 minute hold time)
    2. Some suggest at the end of the autoclave cycle, as the Fo is still accumulating. (The Kaye recording is stopped 25 minutes after the end of the exposure phase)

    Any suggestions
    My suggestion is when you calculate Fo for equipment which is not termal labile to calculate Fo only for exposure time and Fo collected in heating and cooling phase will be some kind of safety margine. But for termal labile product like some nutrient media it is better to calculate Fo for entire cycle to be sure that your product is not affected by long temperature exposing.
    But, as PPG-Validation-Guru said, for porous load according to EN:285 you start to calculate Fo when all temperatures are above 121oC and this is another approach because autoclave exposure time is not important for you, just your termocouples readings.
    US audits are more focused on PDA Technical Report and Fo values but EU audits on EN:285.
    Zeljko Joksimovic

    Independent Expert Associate for Equipment Qualification

  16. #15

    Default

    Hallo Everyone,
    I want to ask about "how to calculate the lethality when oven or autoclave qualification.
    Is calculating lethality ranging from 0 minutes or 1 minute?
    Why? Where i can see the article?
    Thank you for your answer

  17. #16

    Default

    Quote Originally Posted by Muhammad Hendra View Post
    Hallo Everyone,
    I want to ask about "how to calculate the lethality when oven or autoclave qualification.
    Is calculating lethality ranging from 0 minutes or 1 minute?
    Why? Where i can see the article?
    Thank you for your answer
    All about calculation of Fo you can find: http://www.fedegari.com/servizi_documenti_EN.aspx
    Zeljko Joksimovic

    Independent Expert Associate for Equipment Qualification

  18. #17

    Default

    Dear all,

    Please answer what is the lag and log phase in Autoclave validation?

  19. #18

    Default

    Quote Originally Posted by ynreddy83 View Post
    Dear all,

    Please answer what is the lag and log phase in Autoclave validation?
    Lag time is the time in minute between your first sensor reached 121.1 or ur set temperature and last sensor reached 121.1 or set temperature.
    Zeljko Joksimovic

    Independent Expert Associate for Equipment Qualification

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