Decontamination: Operator Level and Process Overview Part 2

Question 1

what is sterilisation

Answer 1

the process which used instrumentation is subject to, generally using high temperature and clean-steam pressure to destroy any microbial presence on the surface of the instruments, offering assurance that we have minimised the risk of Healthcare Associated Infections (HAI’s), by ensuring the instruments are sterile or have been sterilised, for any patients that the instruments will be used on in the future.

Question 2

how can the survival of a microorganism on an individual item be expressed

Answer 2

The survival of a microorganism on an individual item can be expressed in terms of probability

while this probability can be reduced to a very low number, it can never be reduced to zero

Question 3

what is clean steam

Answer 3

This term is in reference to steam made form purified water opposed to steam being made directly from potable water (tap water)

Question 4

what is the problem with potable water

Answer 4

Potable water still has the potential to carry harmful substances and mineral particulate that can form residue on items it contacts

Question 5

why is clean steam essential in the sterilisation process

Answer 5

Clean-steam is essential in the sterilisation process as almost every bit of particulate has been removed from the water before it is used to produce steam.

Question 6

define sterile

Answer 6

‘free from all viable microorganisms’

Question 7

can you guarantee instruments are sterile

Answer 7

the only guarantee that we can offer is that we processed our instrumentation to the best of our abilities, following all recommended guidance and achieving all required standards.

Question 8

what does the term sterilised suggest

Answer 8

This would suggest that something is not sterile at the point of use

An instrument may have been subject to a sterilisation process but without proper handling and management may no longer be sterile at the point it will be used for a procedure

Question 9

how can pressure be measured

Answer 9

Pressure can be measured/displayed in ‘Bar gauge’ or ‘Bar absolute’

Question 10

explain bar gauge

Answer 10

This is in reference to pressure being measured with the starting pressure/atmospheric pressure listed as ‘0 bar’ (atmospheric pressure is approximately 1 bar)

Question 11

explain bar absolute

Answer 11

This is in reference to pressure being measured from absolute zero (complete vacuum) where atmospheric pressure is identified, correctly, as 1 bar

Question 12

what are the different types of sterilisers available

Answer 12

Type - N
Type - B
Type - S

Question 13

what do all the sterilisers have in common

Answer 13

The one thing they all have in common is they all use steam to destroy microbial presence

Question 14

what is the issue with sterilisation

Answer 14

The issue we have is that the temperature we require exceeds the boiling point of water

Question 15

how can we overcome the issue with temperature

Answer 15

We must increase the pressure and in order for us to do this we need to trap the steam with a vessel while producing more steam to feed into that vessel.
The pressure will then begin to increase and the temperature along with it.

Question 16

what is the vessel of a steriliser

Answer 16

The vessel in this situation is the chamber of the steriliser where we will be loading the instrumentation.

This is considered to be a ‘pressure vessel’ and requires an annual validation and inspection by a ‘Competent Person’ from your insurance company.

Question 17

who is a competent person

Answer 17

anyone with the requisite skill set that is occupationally competent to be carrying out the work, within their designation.

Question 18

what does the vessel allow us to do

Answer 18

This allows us to increase the temperature of the steam to the required temperature banding that we are looking for (134 - 137 degrees Celsius).
Unfortunately, the process is not as simple as injecting steam into a chamber though

Question 19

describe a type-N steriliser

Answer 19

○ also referred to as a ‘Gravity Displacement Steriliser’.
○ This machine offers the most basic of sterilisation processes and has limitations on the equipment that can be processed through the machine.
○ Only unwrapped, rigid steel instruments, without channels or lumens, can be processed through this equipment.
○ The cycle differs significantly from other, more effective, sterilisation processes.

Question 20

describe a type-B steriliser

Answer 20

○ also referred to as a ‘Porous Load or Vacuum Capable’ steriliser.
○ The process in this machine is far more robust and effective than the Type - N.
○ All our equipment (providing it is not temperature sensitive) can be processed through the machine.
○ Wrapped instrumentation and channelled and lumened instrumentation can also be processed.

Question 21

describe a type-S steriliser

Answer 21

○ also referred to as a ‘Statim’ or ‘Special’ steriliser.
○ The process in these varies significantly from the other two. ○ They potentially have more processes than simply sterilising such as washing and lubrication as well.
○ We can only process the specific instrumentation mentioned in the manufacturers recommendations for use.
○ Manufacturers recommendations should be followed at all stages for this equipment, including, type of instrumentation, loading requirements and continued testing and maintenance of the machine

Question 22

what does channelled and lumened mean

Answer 22

this is in reference to instrumentation that has internal structures (water channel, air channel) and must be sterilised inside and out.
Easiest example of this would be a hand piece

Question 23

explain the process and cycle of type-N sterilisers

Answer 23

○ The main difference between this and the Type - B steriliser is this one does not have vacuum capabilities.

○ It achieves the same temperature and holds it for the same amount of time; (134 - 137 degrees Celsius for a minimum of 3 minutes)

○ but it does not have air removal due to the lack of vacuum capabilities which creates the limitations on the equipment that can be processed through this machine.

○ When we close the door on the chamber, it is filled with air.
§ On this machine the steam is created inside the chamber, almost like a pressure cooker.
§ As the steam pressure builds up it passively forces the air from the chamber.
§ This process isn’t entirely efficient and can lead to pockets of air remaining in the chamber.

○ Air does not behave the same way as steam, it does not heat well and will always be a lower temperature.
§ This is an issue for us as every part of the chamber and everything being processed must reach the required temperature, for the required amount of time.

○ Because of the lack of vacuum we cannot process wrapped instruments, as the steam cannot penetrate the wrapping to contact the instruments, or channelled/lumened instruments, as the steam will not reach all internal and external surfaces.

○ This limits the testing of the process as well

Question 24

what is the sterilisation pressure for a type-N sterilisers

Answer 24

Sterilisation pressure is 2.05 - 2.3 bar gauge (134 - 137 degrees respectively).

Question 25

what is the cycle and operation of a type-B steriliser

Answer 25

○ Again, when we close the door on the chamber, it is filled with air.
§ This time though, the first stage of the machine is to remove all of this air by using a vacuum pump.

○ Atmospheric pressure is approximately 1 bar or 1000 millibar (mb), as is the case within the chamber, when we have loaded our instrumentation.
§ Because the door and chamber are sealed together, when the vacuum process begins, it causes a drop in pressure inside the chamber, from the 1 bar at atmospheric pressure, down towards absolute zero. It is easier to express in millibar.

○ Atmospheric pressure - 1000mb.

○ Pressure during vacuum stage - 80mb.
§ That means we have a 920mb difference in pressure from atmospheric.
§ This stage physically sucks all of the air from the chamber so that it cannot interfere with our process.
§ The temperature differential can be in excess of 5 degrees Celsius if air is present within the chamber.

○ The steam is not produced in the chamber on this machine either.
§ There is a clean steam generator built into this equipment that feeds steam into the chamber.
§ As soon as the steam valve opens, because of the negative pressure inside the chamber the steam is sucked right inside, rushing in to come into contact with all surfaces.
§ There are several ‘pulses’ of steam, where steam is introduced and then drawn back out of the chamber, via the vacuum pump.
§ This is to ensure that the first bit of steam we introduce to the chamber has not condensed back into water, while waiting on us reaching our sterilisation temperature (134 - 137 degrees Celsius for minimum 3 minutes).

○ Because of the combination of air removal and high steam inlet pressure, we are able to penetrate wrappings surrounding the instruments and contact all surfaces of the instruments being processed.
§ The same applies when processing channelled and lumened instruments.
§ If we are processing a hand piece, the vacuum stage means that the steam rushes in and floods the internal surface of the hand piece, and all channels within it as well.

○ At the end of the cycle there is a another vacuum stage that allows any remaining moisture to vaporise so that it does not saturate the product.
§ By dropping the pressure it changes the boiling point of water which means any remaining moisture will turn into steam at much lower temperatures (approx. 80 degrees or less).

Question 26

what are the stages in a type-B cycle graph

Answer 26

• pretreatment = air removal by fractioned prevacuum
• sterilisation = holding time
• post-treatment = drying by post vacuum

Question 27

what is the sterilisation pressure for a type-B sterilisers

Answer 27

The pressure for sterilisation is 2.05 - 2.3 bar gauge (134 - 137 degrees respectively).

Question 28

are instruments processed in a type-B steriliser sterile at the point of use?

Answer 28

Because instruments are wrapped in semi-porous packaging before they are processed through a Type - B, as long as the packaging remains intact, the instruments will be sterile at the point of use.

The packaging has been fully sterilised on the inside, along with the instruments within it, and acts as a protective layer allowing processed equipment to be stored and remain sterile while doing so.

Question 29

are instruments that are processed in a type-N steriliser sterile at the point of use?

Answer 29

Because it is not possible to wrap instruments before processing them through a Type - N, we can only say that they have been ‘sterilised’.

Although the entire inside of the chamber (providing there is no air present) has been through the sterilisation process, the surface of the instruments is exposed to the environment ie has no wrappings/packaging.
When we open the door of the machine there is the potential to re-contaminate anything that we have processed, before it can be used again

Question 30

what tests are done on a type b steriliser

Answer 30

Due to the nature of the cycle being more complex and effective on a Type - B steriliser.
The tests that we must carry out are more in depth.
We must do a ‘Bowie-Dick’ test or ‘Steam Penetration’ test on a daily basis.

Question 31

what is a bowie-dick test

Answer 31

done before and after processing.

• It checks for steam penetration but also informs us that our temperature has been reached and there has been sufficient air removal within the chamber.

• Once the correct temperature is achieved within the machine the colour change (yellow - navy blue) takes place.
Anything less than a 100% colour change is a fail

Bowie-Dick is the industry standard and has been around for the longest period of time

Question 32

what is PCD

Answer 32

‘Process Challenge Device’ or ‘Process Control Device’.

Question 33

what general loading recommendations should be followed at all times for all equipment

Answer 33

○ no over-lapping or shadowing of equipment

○ do not overload the machine or chamber

○ utilise the space on the available load carrier or basket

○ hinged or jointed instruments should be open at the hinge

○ any assemblies should be disassembled prior to processing

○ everything should be processed to the best of your capabilities so that it maintains its position throughout processing

Question 34

what general loading recommendations should be followed specifically for the type-N steriliser

Answer 34

○ only rigid steel instruments should be processed through this machine (probes, mirrors, tweezers)

○ no channelled or lumened instruments such as hand pieces. The machine process is not capable of sterilising all surfaces inside and out

○ wrapped instrumentation cannot be processed through this machine at all

Question 35

what general loading recommendations should be followed specifically for the type-B steriliser

Answer 35

○ nearly all instrumentation can be processed through this type of equipment

○ wrapped instrumentation and porous loads (fabrics, cotton swabs) can be processed through this equipment

○ we can process channelled and lumened instruments through this equipment
it is essential we do not damage wrappings when loading the machine

Question 36

what general loading recommendations should be followed specifically for the type-S steriliser

Answer 36

○ these machines are specialist and generally designed for a specific purpose eg sterilisation of hand pieces

○ manufacturers recommendations must be followed for the loading and operation of this equipment

Question 37

what is the vacuum leak test / air leakage test

Answer 37

this is to verify the vacuum capability of the machine and is carried out on a weekly basis

Question 38

what is the helix / bowie-dick test

Answer 38

this test is for steam penetration and is carried out on a daily basis with the use of PCD’s

Question 39

what is an ADFT

Answer 39

air detector function test

this test is carried out on a weekly basis and is designed to check the safety device within the machine, for detecting air

Question 40

Are there other sterilisation temerpatures

Answer 40

There are other sterilisation temperatures that can be used but we would generally reserve these for temperature sensitive equipment ie anything that could be damaged by the process at 134 - 137 degrees

The reason we do not use these as standard is because when we effect a drop in temperature there has to be an increase in time to maintain the same level of efficacy.

Question 41

what are the sterilisation temperatures

Answer 41

○ 134 - 137 degrees Celsius for a minimum ‘stage’ hold time of 3 minutes (this is the most commonly used temperature set-point)

○ 121 - 124 degrees Celsius for a minimum ‘stage’ hold time of 15 minutes (for temperature sensitive equipment)

○ 115 - 118 degrees Celsius for a minimum ‘stage’ hold time of 60 minutes (generally lab sterilisers, rarely used in health care)

Question 42

is there stage hold time the same as the sterilisation cycle

Answer 42

no

Question 43

what is the stage time

Answer 43

• The stage time is in reference to the minimum amount of time the sterilisation stage must last for, after the required temperature has been reached
i.e. once our chamber temperature is over 134 degrees the ‘stage’ must hold that temperature for at least 3 minutes.

Question 44

what is the fast cycle

Answer 44

• The fast cycle is in reference to a cut down version of the main cycle.
The sterilisation stage will remain a constant.

• It may not produce the same level of vacuum efficiency or might have a shortened drying stage at the end of the cycle.
• This cycle could be used if we were processing a reduced number of instruments or smaller loads through the machine.

Question 45

what is a prion cycle

Answer 45

This is not accurate, don’t be fooled by it.

○ As we have previously covered, protein or prion can only be removed through a rigorous cleaning process.

○ Prion (specifically vCJD) can survive temperatures in excess of 150 degrees Celsius for hours at a time.

○ It is not feasible for us to operate a sterilisation service such as this and the set-points of this cycle would not cater for that

Question 46

how do you unload after the cycle is complete

Answer 46

• The machine will inform us when the cycle has achieved its set-points and completed successfully.
• Particular attention should be given to making sure the machine identifies the cycle has completed successfully, as this will offer us assurance that sterilisation has taken place.
• A print out, receipt or on more modern machines, a PDF document will be created to verify all cycle set-points have been achieved, and also for traceability purposes, to ensure you are operating your equipment to the required standard

Question 47

how is a type-N steriliser unloaded and packaged

Answer 47

there is still a significant amount of moisture present within the chamber of the Type - N.

The recommendations are to leave the door ajar so that any remaining moisture has the opportunity to vaporise as there can still be quite a significant amount of heat within the chamber.

This isn’t as efficient as the drying process on the Type - B steriliser, which uses a high vacuum to allow water to vaporise at lower temperatures, and also takes the same time or potentially longer.

Question 48

how long should the type-N cycle have its door left ajar for

Answer 48

When the Type - N cycle completes the door should be left ajar until the remaining moisture has lifted from the instruments and they have cooled sufficiently, then, upon opening the door, the instruments would be put into packaging.

Question 49

what can be the effects of using tap water within a steriliser

Answer 49

it has the potential to leave residue on the surface of the instruments

if none of the particulate or minerals have been removed these can potentially create deposits on the surface of instrumentation

Question 50

true or false: you can process wrapped instruments through any type of machine as long as they are dry at the end

Answer 50

false

it can only be processed through a type-B machine

Question 51

true or false: for the standard sterilisation temperature banding, the cycle time should be 3 minutes

Answer 51

false

do not confuse cycle time and stage time

Question 52

what is the first stage of a vacuum capable sterilisation cycle

Answer 52

air removal

Question 53

what is the temperature banding for our standard sterilisation cycle

Answer 53

134-137 degrees

Question 54

should we wash instruments manually

Answer 54

• Try and avoid manually washing instruments entirely if possible
• Reason we manually wash is because on equipment itself, there are limitations to the power that they have
• The force of the jets of water is the mechanical force to remove contamination
• If something comes out machine still contaminated, then we would manually wash it

Question 55

what are the concerns with manual washing

Answer 55

• Aerosol
• Cross infection
• Sharp injuries

Question 56

what are the benefits of manual washing

Answer 56

Exert more manual force than WD capable of