EFHSS Questions and Answers - Question Q00543

I am trying to determine the most appropriate test method for evaluation of air removal and steam penetration in small steam sterilisers.

Can anyone tell me whether it is appropriate to use only a hollow load A process challenge device ( ie a helix) as a means to evaluate air removal and steam penetration in a class b (or S) sterilization cycle used to process both packaged and hollow items?

Or if you process these types of loads, do you also need to use a porous load process challenge device in addition to the helix?

Thanks in anticpation of some clarification.

Terry

If the load you intend to sterilize has charectaristics of tubes or capilars like dental hand-pieces, test the air removal with Helix Test Device.
If your load is porous, and/or it is rigids, paper or textile wrapped or packed, test it with BD Test (pack).
There is no reason to over-stress the machine.
Keep it (annually) calibrated and validated, record the processes, and maintain the device acc. to the manufacturer instruction.
Why do you care if it is a S class or B class. The intended use is the importance!

and to your 2nd question.
BD and Helix CI (Chemical Indicators) are Class 2 indicators. Special once for a unique task.
When you want to challenge a cycle you need an Indicator that will proove that sterilization conditions were transformed from the sterilizer to the load. Meaning that correct temperature / pressure / time was given to the load. These are Class 4 Indicators.
The Australian Standarts (AS 4187, 4815, 2182) and others can guide you in a very good way.

miki

Hi Miki, thanks for the response. However, I think I may not have been clear enough in the way I phrased the question.

Firstly -I dont care whether the steriliser is a B or S -as both types may be used to process both packaged and hollow (cannulated/lumened) items -the S class only where this is the intended use specified by the manufacturer -I understand this very well.

So what I am saying -or let me put this as a hypothectical -if I intended to package (whether it is in a non-woven wrap or in a paper/laminate [steripeel] )a dental handpiece or other similarly lumend or cannulated item, which particular performance test should I select for my steriliser - the bowie dick type test or the helix type test?

For example if I process both porous items and packaged cannulated items routinely in my steriliser -which is the appropriate test?

The second part of my question wasnt about chemical indicators -it was just trying to elaborate on what I meant by the first part of the question.

Thanks for telling me about the applicable Australian Standards. I am actually on the technical committee for 4187 and 4815 -so I really was hoping someone in EFHSS would be able to enlighten me as to which of the two options -helix or BD is used in the cases of sterilisers processing both types of items.

Looking forward to hearing from you.

Hi Terry.

My answers present my own quality and technical approach. Not commercial.
"Intended use" and "normal use" are fundamental assumption.
Purchasing a Table top is a "big deal" for the customer. He must be advised on the options as well as the difficulties. Shall he sterilize non wrapped? (cheap device, but without storing). Shall he wrap? for what shelf life? will it be transported? shall he wrap single instrument? a set? single wrap? double? paper/paper bag? laminate? pouch? shall it be a B class or S? What does the customer understand. He just is forced to purchase an autoclave.
BD or Helix? The Helix was developed to challenge the Hand piece sterilization cycle.
As far as I studied, lumens is a challenge similar to porous load, - use BD.

best regards
miki

Terry,

The standard for routine testing of "B" and "S" type sterilisers is EN 867 part 5. This standard also gives the appropriate cycle pfofiles for these types of table top sterilisers.
To sterilise any hollow instruments, the only way to achieve this, is to utilise a steriliser that has a vacuum pump that removes air from within the hollow instrument, and a "B type steriliser is the only unit that will achieve this. "S" and "N" type sterilisers that do not have a vacuum pump cannot facilitate air removal and steam penetration of hollow instruments and therefore cannot sterilise them.
To answer your question.... if you are sterilising mixed loads, wrapped or unwrapped, hollow or porous, then the correct test is the helix device which is the only way that you can monitor the most important aspect of the cycle, and that is the air removal phase. If you can't achieve air removal, then you do cannot have steam penetration, and subsquently the hollow content of the mixed load cannot be guaranteed as sterile. You cannot monitor air removal from a hollow instrument using a porous test pack and this will be reflected in the revised edition of EN 285 where testing of hollow instruments will be caried out with a hollow PCD and a porous load to be monitored with a porous PCD.
Chemical indicators are old technology and are a hangover from the old downward displacement sterilising cycles where it was necessary to ensure that the temperature inside each pack in the load or batch was the same as the temperature in the chamber free space.A chemical indicator can never monitor air removal and is only capable of monitoring time and temperature at the location where it is placed

Kind regards,
Bill

Dear Terry

Just a comment on some of the facts you have been given as I am sure by now you have the picture !! Any wrapped item being a hollow lumen or not represents a porous load - and therefore should be subjected to a porous load test - however this is not as simple as it seems as through extensive research we have found that to get a truely accurate BD test FOR TYPE B sterilizers, these BD tests need to be individually calibrated to each manufacturers cycle - In other words a BD which is sterilizer manufacture specific ie W&H, Getinge etc these are however available - but as you can imagine costly.
Secondly Mr Davis' comment that Chemical indicators are old technology and are a hangover from the days of downward displacement sterilizers could not be further from the truth as it is a universally accepted fact the the BD test cannot be conducted in a downward displacement sterilizer and was only designed specifically for vacuum sterilizers as, I am sure you are aware, - To state that chemical indicators can only monitor time and temperature is again a miss conception as, modern technology enables those with advanced capabilities, to monitor so much more as is well documented - in any case whether you are conducting a BD test or a Helix test both are reliant on the interpretation of a chemical indicator as Miki stated.

I hope this helps
Kind regards
Peter

Terry,

This is our response to Mr Newson's (Brownes UK) comments which we found to be very confusing.
What picture is Mr Newson talking about? Is this reality or is it commercially driven!!
Mr Newson states that "Any wrapped item being a hollow lumen or not represents a porous load"
How can a hollow lumen possibly be classed as a porous load?More to the point, how can a porous test determine air removal and steam penetration in to that hollow lumen?
Mr Newson is also confusing a B/D test with a stand alone chemical indicator. A B/D test comprises of a chemical indicator in combination with a test load. The aspect of a B/D test having two components is often overlooked.
Mr Newson appears to be linking the stand alone chemical indicator (class 4/5/6) with a B/D test.
We totally agree with Mr Newson's comment that it is universally accepted that a B/D test cannot be used in a downward displacement steriliser( as it does not pull a vacuum), however, it is also universally accepted that chemical indicators class 4/5/6, are acceptable for the monitoring of downward displacement sterilisers and over pressure cycles. eg Most "S' and all "N" type benchtop sterilisers.
A class 4 chemical indicator as referred to by Mikki (like a class 4/5/6 indicator) cannot, under any circumstances recognise air or non condensable gases, so for monitoring air removal from hollows, a helix device according to EN 867 part 5 is the recommended option to be used for routine monitoring in a "B" or an "S" type steriliser.

Just a short note in response to Mr Davis' comments - we are all entitled to our own opinions and these can only lead to good debate however I am not sure whether this is the right forum for this.

By refering to the picture!! I was refering directly to the question Terry had originally asked and believe that the answers given by Miki and Mr Davis to a large extent answered the question. There was No subversive commercial message in any shape or form. As Mr. Davis' is well aware, Browne actually have designed,developed and launched a hollow lumen PCD (helix device) specifically for EN 867-5 therefore ultimately we are able to offer both solutions to the end user - therefore there is no commercial benefit to be gained.

Mr Davis is right that there are two componants to a BD test as is the case with all PCD's (including helix devices) at no stage was I confused about the diference between a class 2 indicator (ie one designed for a specific test) and a class 4/5 or 6 indicator - the original question refers to the PCD either porous or hollow lumen not stand alone indicators (which are a seperate issue and one that has been continually debated). Again it is well documented and proven that through technology different fail indicator patterns on indicator sheets used in someBD tests are able to indicate to the end - user -poor steam quality, non- condensible gases and air - there are currently a number of different BD test manufacturers who are able to offer this technology.

Finally when on the subject general chemical indicators again Mr Davis is correct in saying that a class 4,5 or 6 chemical indicator cannot monitor non- condensible gases or air, however according to the classifications in ISO 11140 - 1 class 5 & 6 chemical indicators must monitor all the critical parameters of the sterilization process which in the case of steam sterilization would be Time, temperature and steam - the only way to achieve an effective pass using one of these indicators is through the presence of steam - which in turn proves the lack of air / non - condensible gases.

Mr Davis and I have had many discussions before in Australia and I trust that we will again in the future. My comments are in no way meant to be confrontational but to show the diversity of thinking between different manufacturers - hopefully this ultimately benefits the end-user

Kind regards

Peter
(Browne international)

Gentleman,

Thankyou all for taking the time to respond to my query. I think this issue very worthy of debate because, in my opinion, this is an issue that has been and will continue to be contentious.

Let me point out that as an educator -I have no commercial interests or affiliations. Therefore my question was posed to elicit what is current thinking in the industry. Being from Australia, we may be somewhat isolated from the plethora of forums for discussing issues generated form the publication of various EN standards.

Firstly -Bill, can you please clarify for me exactly where in EN 867-5 it actually states the air removal profiles specific to B and S type cycles? All I can find is Annexes B, C and D that refer to test cycles for the evaluation indicator systems used in either hollow or porous load process challenge devices. Similarly, in EN 13060 -I cannot find any specifc information stating the air removal mechanism to be used that immediately categorises the machine (or more accurately sterilisation cycle) as being B, S or N.

As for Peter -I agree with you that any item that is wrapped represents a porous item -however -I also acknowledge the need to verify air removal and steam penetration from lumens.

Why then, does EN867-5 specify both types of process challenge devices -if, in many people's opinions -either a porous PCD or a Hollow PCD (depending on which side of the fence you sit) are equivalent to both situations? What I mean by that is -if they truly are representative of both porous and hollow items, then why make a distinction in this standard (EN867-5)? Further, why is there no guidance as to which type of test is most applicable for small steam sterilisers used to process all types of items, packaged or hollow in either EN867-5 or EN13060?

Watch out everyone -I think some worms are about to escape -(ha ha)

Looking forward to some interesting discussion!

Dear Terry

Unfortunately there is no simple answer to this - the issue is that the two devices are not necessarily equivalent, hence why both are stated in EN 867-5.

To start with we need to go back to the validation procedure which as you are aware would include performance qualification (PQ) - however with the plethora of different loads / instruments and packages sterilized in a B type sterilizer it is virtually impossible to achieve complete performance qualification.

Therefore it is generally agreed that worse case loads are used to measure the effectiveness of the process. Historically and particularly in large steam sterilizers the Bowie and Dick test has always been used as a worst case. However bearing in mind a) the places we generally find type B sterilizers i.e. primary healthcare facilities, dental practices etc where there is high usage of Minimally Invasive Surgical (MIS) instruments etc. and B) the fact that in many of these facilities items are unwrapped and therefore do not represent a porous load it is logical that an alternative form of testing should also represent the worst case load - this is the hollow lumen PCD.

So does that answer you question - well no it doesn\'t as the ultimate use of either or is determined by the loads being sterilized. Legally in Europe, there is an obligation on the instrument manufacturer to state how the devices should be processed. Equally there is a legal requirement for the sterilizer manufacturer to state what the sterilizer can sterilize. There is obviously a place for each form of PCD and possibly therein lies your answer. Both the Porous and Hollow lumen PCD should be offered as options for the daily test. But please ensure that they are validated and suitable for their specific purpose.

I hope this helps
Peter
Browne International

Terry,

Please refer to my initial response to the question you originally asked as it answers the query that you expressed.
As to where you can locate the cycle profiles and in which standard they are, I have detailed below the relevant information.
Firstly, what determines the cycle is the load or goods that are to be processed.
The air removal characteristics are the same for both small and large sterilisers, ie Trans atmospheric - Sub atmospheric (generically referred to as Pre-vacuum cycles) and Super atmospheric which traditionally and historically, are the downward or gravity dispalcement cycles.
The types of loads and the respective sterilisers for processing these goods is clearly defined on page 4 in EN 13060.
EN 867 part 5 defines the specification for indicator systems and process challenge devices for use in performance testing for small sterilisers Type "B" and Type "S".
This standard clearly defines the performance and requirements of the indicators and the PCDs and the performance testing for the indicators and PCDs is also clearly defined in annex B of of this standard
The three PCDs, are for hollow A loads, hollow B loads and porous loads as defined in EN 103060.
Hollow A and hollw B PCDs are intended for use with hollow and complex instruments ie MIS instruments
Porous PCDs are intended for use with porous loads and, while the Bowie Dick test can be a porous PCD, it is a stand alone test and should not be used for routine monitoring of a process.
A wrapped pack containing hollow or lumend instruments is not a porous load and should be monitored with either a hollow A or a hollow B PCD.
The cycle profiles for Type"B" and Type "S" sterilisers can be located in annex B of EN867 part 5 and is both written and in graph form and are specified to the performance testing of the indicators and PCDs for use in Type "B" and Type"S" sterilisers as indicated in the title of this standard. If the multi vacuum and steam pulses are at the correct depths and pressures, then air removal and steam penetration of the load is ensured.
In Europe these multi pulse cycles are referred to as Fractionated vacuum cycles.
Type "N" sterilisers are required to sterilise and process unwrapped goods and solid instruments and therefore do not require the same air removal and steam penetration characteristics as the Type"B" and Type "S" cycle profiles. Type "N" cycles are a single vacuum cycle or a gravity (downward) displacement cycles which operate in positive pressure.
We agree with Terry in regard to why EN 867 part 5 makes the distinction that suggest that a hollow PCD is able to monitor both hollow and porous loads. Why then do you require two PCDs?
This is of course a very good question and we believe that the answer would need to come from the committee of EN 867 part 5 who formulated this standard. Our opinion is that the standard is giving the option to the end user to choose a porous PCD or a hollow PCD in the case of Type"B" and Type"S" sterilisers (again it is important to stess that any Bowie & Dick test should not be used for rountine monitoring) depending on the load configuration. This is as you know, applies to all pre-vaccum (multi vacuum/steam pulse) sterilisers irrespective of their size.
Terry, we hope we have answered your original and subsequent questions.

Kind regards
Bill Davis
gke Australia