Sterilization In General - PowerPoint PPT Presentation

1 / 55
About This Presentation
Title:

Sterilization In General

Description:

... test 'Sterilizers' called BIER or CIER vessels. BIER = Biological Indicator Experimental Resistometer ... BIER/CIER vessels performance specified by ISO 18472 ... – PowerPoint PPT presentation

Number of Views:446
Avg rating:3.0/5.0
Slides: 56
Provided by: Ca60
Category:

less

Transcript and Presenter's Notes

Title: Sterilization In General


1
Sterilization In General
  • Whats the process?
  • Decontamination removes gt 80 of microbes
  • Sterilization Kills/inactivates the remaining
    microbes
  • What are the Sterilants?
  • Saturated Steam
  • Ethylene Oxide
  • Ozone
  • Hydrogen Peroxide
  • High Level Disinfectants (Glutaraldehyde, OPA,
    PAA)

2
Sterilization In General
  • Whats the process?
  • Decontamination removes gt 80 of microbes
  • Sterilization Kills/inactivates the remaining
    microbes
  • What are the Sterilants?
  • Saturated Steam
  • Ethylene Oxide
  • Ozone
  • Hydrogen Peroxide
  • High Level Disinfectants (Glutaraldehyde, OPA,
    PAA)

3
Steam Sterilization
  • Critical Variables
  • Time.
  • Temperature.
  • Saturated Steam. (Depends on Temperature and
    Pressure)
  • Other Variables (Incomplete List)
  • Loading
  • Sterilant contact with items to be sterilized
  • Outside weather changes
  • Boiler Chemicals
  • Wrapping Materials
  • Etc, etc, etc.

4
Saturated Steam
Superheated Steam
Wet Steam/ Liquid Water
5
Saturated Steam What is it?
  • It is a colourless gas, containing lt 3 liquid
    water
  • Depends on temperature and pressure
  • It will condense if it cools down a fraction of a
    degree
  • It releases latent or potential heat energy as it
    condenses
  • It is the latent or potential heat transferred to
    microbes that kills/inactivates them

6
Latent Heat Potential Energy
Researcher knows the 16 ton weight has
zero Potential energy. She is not afraid.
16 Ton weight is sitting on the floor It has zero
Potential energy
16 Tons
7
Latent Heat Potential Energy
16 ton weight is now 2 meters off the ground. It
has quite a lot of potential energy with respect
to the researcher
16 Tons
The researcher is now very afraid of the 16
ton weights potential energy
2 meters
8
Latent Heat Potential Energy
Latent or Potential energy from the 16 ton weight
is now realized. Especially by the
late Researcher.
2 meters
16 Tons
9
Latent Heat Potential Energy
16 Tons
Steam (Gas)
Water (Liquid)
16 Tons
10
The ExperimentGenerating Saturated Steam at 1
Atmosphere
100ºC
Temp
All the energy is now going in To creating
latent heat in the steam With no increase in
temperature
It takes 150 KJoules to heat 1 lb of water from
20ºC to 100ºC and 1023 Kjoules to convert 1 lb of
water from liquid to gas at 100ºC
Time
11
Typical Steam Sterilizer
12
Sterilization Monitoring
  • We monitor the Process not sterility of items
  • Because the process is validated (by the
    manufacturer of the sterilizer) we assume that,
    if the process functions correctly, the goods in
    the process will be sterile.

13
Process Monitors for Steam Sterilization
  • 3 Major types used
  • Biological Indicators
  • Monitor all variables in the process
  • Chemical Indicators
  • Monitor one or more of the critical variables
  • Mechanical Indicators
  • Monitor one of the critical variables

14
Process Monitors for Steam Sterilization
  • Individually they provide information, but only
    together do they tell the whole story!
  • A failure in any one of the monitors implies the
    process is incomplete in one or more necessary
    variables

15
Biological Indicators
  • Large (gt 105 or 106) of resistant spores
  • Usually Self-contained type
  • Placed in a normally loaded sterilizer
  • At least one per day per cycle (CSA)
  • Final Readout made at 1, 3, 24 or 48 hours
  • Test the process to ensure it is capable of
    killing microorganisms

16
Self-contained Biological Indicator
Vial
Ampoule Growth media Indicators
Cap
Spore Strip
Filter
17
How do they Work?
  • Colour change indication
  • If spore survives, it is incubated
  • Spore consumes nutrients, excretes acid
  • Spore creates subsequent generations that also
    consume nutrients and excrete acids
  • Purple (or other) dye is acid sensitive
  • If enough acid is produced, dye will change from
    purple to yellow (or other colour change)
  • Process can take up to 48 hours to get reliable
    prediction of kill

18
How do they Work?
  • Rapid Read BIs
  • Spore survives the sterilization cycle and is
    incubated
  • Nutrients are tagged with a U.V. fluorescent
    dye
  • As spore consumes nutrients the dye is released
    and begins to fluoresce
  • Fluorescence is detected electronically
  • Process takes up 3 hours to get reliable
    prediction of kill

19
What bout these Extended Cycles?
  • G.stearothermophilus will still be the test
    spore.
  • Requires a new Process Challenge Device (test
    pack) not a new BI
  • Extended cycle required because bigger. Heavier
    more complex sets protect microbes better
  • PCD must provide the same protection to the BI

20
BIs and CIs
  • All current sterilization standards (AAMI, CSA
    and ISO) require the use of Biological
    indicators.
  • Chemical Indicators cannot replace Biological
    indicators because
  • Biologics are far more complex
  • Biologics have the potential to recover after
    serious damage
  • Chemistries only approximate the response of
    Biologics
  • Chemical kinetics are far simpler than biologic
    kinetics
  • Chemical indicators only measure the critical
    variables of the process. Biologics integrate
    all the variables of microbial death

21
Understanding Chemical Indicators
  • To fully understand Chemical indicators one must
    understand
  • BIER/CIER Vessels/Test methods used by
    manufacturers
  • Stated Values (SVs)
  • ISO/AAMI Classifications of Chemical Indicators
  • How it all relates to YOUR sterilization process
  • What a pass/fail result really means

22
Test Methods for Testing Chemical Indicators
  • Must be reproducible, controlled and consistent
  • Based on standard test Sterilizers called BIER
    or CIER vessels
  • BIER Biological Indicator Experimental
    Resistometer
  • CIER Chemical Indicator Experimental
    Resistometer
  • BIER/CIER vessels performance specified by ISO
    18472
  • BIER/CIER Vessels behave very differently from a
    typical health care sterilizer

23
BIER/CIER Vessels
  • Very Small Chamber
  • Very tight controls
  • Highly reproducible results
  • Basis for all Biological and Chemical indicator
    testing
  • All CI Stated Values are based on this vessel

24
Some Requirements of CIER Vessels
  • Come-up time lt 10 seconds
  • Come-down time lt 10 seconds
  • Vacuum air removal lt 2 minutes
  • No steam allowed during air removal
  • Set Temperature within 0.5ºC
  • Set Time within 1 second
  • Pressure within 3.5 Torr
  • One data point recorded per second

25
Contrast CIER Vessel to Health Care Sterilizer
  • Come-up time 5 to 15 minutes
  • Come-down time 5 to 15 minutes
  • Vacuum air removal 5 to 15 minutes
  • Steam used during air removal
  • Set Temperature within 2ºC (?)
  • Set Time within ??
  • Pressure within ??
  • One data point recorded per 30 seconds

26
Test Methods for Chemical Indicators
  • All testing done in a CIER Vessel
  • Must meet requirements of ISO 11140-1
  • ISO 11140 is written for Manufacturers not end
    users
  • Specifications are broken in to 6 categories
  • Only need to show the ability to reach the stated
    values.

27
Stated Values What are they?
  • For any given chemical indicator to be compliant
    with ISO 11140-1, it must have Stated Values
    for the parameters it measures.
  • Example For a Class 3 Chemical Indicator, it
    must have a stated value for temperature. This
    is the temperature at which we can expect to see
    the change in the CIER vessel.

28
Stated Values and ISO 11140-1
  • The standard uses the Stated Values to define
    how the indicator will perform.
  • Example A Class 4 Indicator
  • Stated Values
  • 134ºC
  • 4 Minutes
  • ISO allows a range
  • Colour change (Pass result) must be seen at
    134ºC, after 4 minutes exposure in the CIER
    vessel. A fail (no colour change) result must be
    seen at 132ºC after only 3 minutes exposure. No
    additional testing is required at points in
    between.

29
Stated Values and ISO 11140-1
  • A Class 6 example
  • Stated Values
  • 134ºC, 4 Minutes (Saturated steam)
  • A pass result must be seen ( in the CIER vessel)
    after 4 minutes exposure at 134ºC
  • A Fail result must be seen at 133ºC after 3 min
    45 second exposure in a CIER vessel.
  • No additional testing of points in between is
    required.

30
Stated Values and ISO 11140-1
  • The BIG QUESTION
  • So, if a chemical indicator shows a pass result
    in your sterilizer does it mean that the Stated
    Values given for that particular chemical
    indicator have been achieved?

31
Chemical Indicators
  • Changes (reactions that cause colour change)
    start at temperatures well below the stated
    values for the CI
  • Temperature at which the reaction starts is the
    initiation temperature
  • Changes (reactions) will continue once initiated
    and the temperature is above the initiation
    temperature

32
Rates of Reaction and Initiation Energies
In our house my wife allows me the honour of
pressing my own shirts. As part of that process
I have learned a lot about the chemistry of
burning fabrics.
33
Rates of Reaction and Initiation Energies
For example, I discovered that if I place an
unplugged (cool) iron on a shirt, I can leave it
there indefinitely and it will not scorch the
shirt. Thats because the energy imparted to the
shirt from the cool iron is well below the
initiation energy required to start the burning
reaction of the fabric. It also doesnt remove
wrinkles
34
Rates of Reaction and Initiation Energies
  • Ive also learned that I can leave an iron on its
    lowest setting on the shirt indefinitely and it
    will not scorch the shirt either. I guess the
    low setting still doesnt deliver enough energy
    to start the burning reaction

35
Rates of Reaction and Initiation Energies
  • Of course, an iron on medium setting will scorch
    the shirt, but it takes quite a few minutes to do
    so,
  • On high setting, the wrinkles go, but if I leave
    the iron on the shirt for even a short time, it
    will scorch.

36
The Scorched Shirt Example
37
Chemical Indicators
  • Example (Theoretical) CI has stated values of
    134ºC, 4 minutes Initiation temperature may be
    100ºC and reaction (change) will start to occur
    at that temperature and continue while the
    temperature remains over 100ºC.
  • The rate of change will vary with temperature
    once initiated. Usually faster as temperature
    increases

38
BIER/CIER Vessel Testing
39
Same CI in a Health Care Sterilizer
40
Next Big Question(s)
  • If chemical indicators start to react below the
    stated values
  • How fast do they react at lower temperatures?
  • Will they change if they spend sufficient time at
    lower temperatures?
  • What does that mean for monitoring my sterilizer?

41
Extended Cycle Time Temperature Plot Set Points
132ºC, 18 min)
42
Conclusions so far..
  • Stated Values cannot be duplicated in Health Care
    Sterilizers
  • Stated values can be used only for comparative
    purposes between Chemical Indicators of the same
    class
  • Stated Values are used by Manufacturers of
    Chemical Indicators to make CSA/ISO or AAMI
    Classification claims.

43
CSA/ISO/AAMI Classification of Chemical Indicators
  • All follow the ISO 11140, 6 tier classification
    structure
  • All state the class has no hierarchical
    significance. (i.e. a Class 2 is not better
    than a Class 3 or a Class 6 is not better than
    a Class 5.)
  • Classification structure is to provide
    specifications and targets for manufacturers of
    chemical indicators
  • It may be used by users for comparing CIs within
    the same class

44
Definitions
  • Critical Variable
  • For steam sterilization Time, Temperature and
    Saturated Steam
  • For Ethylene Oxide EtO concentration, humidity,
    time, temperature
  • Critical Parameter
  • A set value of a critical variable that must be
    attained
  • Stated Values
  • The critical parameters measured by a Chemical
    Indicator in a CIER vessel

45
CSA/ISO/AAMI Classification
  • Class 1 Process Indicators
  • Autoclave tapes, built-in CIs on peel pouches
  • Simply identify processed from unprocessed
    packages
  • Class 2 Special Indicators
  • Bowie-Dick Type Tests
  • Class 3, 4, 5, and 6 are all Internal Indicators

46
Classes 3 - 6
  • Class 3 Indicator
  • Measures only one of the critical variables of
    the process
  • Class 4 Indicator
  • Measures 2 or more of the critical variables of
    the process
  • E.g. Time and temperature, or time saturated
    steam.

47
Classes 3 - 6
  • Class 5 Integrating Indicator
  • Measures all critical variables of the process,
    and correlates with the test spore for that
    process across a range of sterilization
    conditions
  • For steam sterilization, the Class 5 must
    correlate with G.stearothermophilus at 121ºC,
    128ºC and 135ºC
  • Has a known response over a range of
    sterilization temperatures

May be other temperatures within the range of
121 - 135ºC
48
Class 5 Integrating Indicator Response
49
Class 3 - 6
  • Class 6 Emulating Indicator
  • Measures all critical variables of the process
  • Tightest specifications of all indicators
  • Stated Values are for a specific time and
    temperature for steam sterilization

50
Class 6 Emulating Indicator Response
51
Class 6 Emulating Indicator Response
52
Conclusions
  • Saturated Steam is critical to the sterilization
    process
  • Non-condensable gases (air, CO2, N2) are poor
    heat transfer media and poor sterilants
  • It is the latent heat of saturated steam, not the
    temperature that kills the microbes

53
Conclusions
  • All process monitors must agree that the cycle
    was successful
  • A failure in any one of the 3 types of monitor
    (Biological, chemical or mechanical) means the
    process was insufficient and processed goods are
    suspect

54
Conclusions
  • Biological Indicators are the only indicator to
    integrate all the variables of he sterilization
    process
  • They are the only direct measure of the lethality
    of the process
  • The BI response can be approximated by chemical
    indicators, but CIs cannot replace BIs

55
Conclusions
  • The basis for classification of Chemical
    Indicators in Canada is CANISO 11140
  • This standard is written for manufacturers of
    chemical indicators.
  • The standard has no hierarchical significance
  • Stated values are only realizable in the test
    vessel (CIER vessel)

56
Conclusions
  • Selection of biological indicators and chemical
    indicators must be made considering patient
    safety, the information needed from the
    indicators, the standard requirements, best
    practices and economic considerations. No single
    indicator will likely accommodate every
    circumstance
Write a Comment
User Comments (0)
About PowerShow.com