The Bowie and Dick Type The Bowie and Dick Type TestTest

Does size and penetration Does size and penetration really matter?really matter?

Presented byPresented byTerry McAuleyTerry McAuleySterilisation and Infection Control Sterilisation and Infection Control ConsultantConsultant

Discuss the purpose of the Bowie Dick type testDiscuss the purpose of the Bowie Dick type test Examine the applicable European Norms (EN) & Examine the applicable European Norms (EN) &

International Standards Organisation (ISO) International Standards Organisation (ISO) standards that refer to Bowie-Dick type testsstandards that refer to Bowie-Dick type tests

Outline the basic requirements in the EN & ISO Outline the basic requirements in the EN & ISO standards that can be used to evaluate claims of standards that can be used to evaluate claims of test conformancetest conformance

Explain the correct method for performance, Explain the correct method for performance, interpretation and documentation of the Bowie-Dick interpretation and documentation of the Bowie-Dick type testtype test

It’s a matter of physical It’s a matter of physical chemistry…..chemistry….. A Bowie-Dick is a physical test uses a A Bowie-Dick is a physical test uses a

chemical indicator to demonstrate that chemical indicator to demonstrate that steam penetration has been adequate by steam penetration has been adequate by showing a uniform colour change in the showing a uniform colour change in the indicatorindicator– In order for the indicator to change colour a In order for the indicator to change colour a

chemical reaction must occur at certain chemical reaction must occur at certain temperatures in the presence of moisture temperatures in the presence of moisture

– By default, a satisfactory result translates into an By default, a satisfactory result translates into an assumption that air removal was adequateassumption that air removal was adequate

Size matters……..Size matters……..

Required for the test:Required for the test:– Huckaback towels (36” x 24” ) folded to give 8 thicknesses Huckaback towels (36” x 24” ) folded to give 8 thicknesses

of cloth of cloth 25-29 were required to create a stack of the right height25-29 were required to create a stack of the right height

– Two 12” strips of autoclave tape placed in the form of a Two 12” strips of autoclave tape placed in the form of a cross on a 10” x 8” sheet of unglazed papercross on a 10” x 8” sheet of unglazed paper These sheets could be inserted at various levels throughout These sheets could be inserted at various levels throughout

the stack, although one sheet in the centre of the pack was the stack, although one sheet in the centre of the pack was acceptableacceptable

– Huckaback towels in a 10”-11” high stack were then Huckaback towels in a 10”-11” high stack were then placed in a rectangular dressing casket, cardboard box or placed in a rectangular dressing casket, cardboard box or were wrapped in fabricwere wrapped in fabric

– Bowie et al (1963)Bowie et al (1963)

In their own words….In their own words….

““This test is essentially a test of steam This test is essentially a test of steam penetration, not of time-at-temperature”penetration, not of time-at-temperature”

““A satisfactory test will indicate rapid steam A satisfactory test will indicate rapid steam penetration, adequate air removal and penetration, adequate air removal and freedom from significant air leaks.”freedom from significant air leaks.”

““A uniform colour change may be obtained A uniform colour change may be obtained without adequate initial air removal if the without adequate initial air removal if the holding time is artificially extended”holding time is artificially extended”

– Beyond 3 ½ minutes@ 134Beyond 3 ½ minutes@ 13400C C – Bowie et al (1963)Bowie et al (1963)

In their own words….In their own words….

““In some sterilisers In some sterilisers (where steam is admitted during (where steam is admitted during

vacuum phases) vacuum phases) penetration will occur and the penetration will occur and the load temperature will rise before the end of load temperature will rise before the end of the prevacuum period. In such sterilisers a the prevacuum period. In such sterilisers a satisfactory result indicates adequate steam satisfactory result indicates adequate steam penetration but does not necessarily confirm penetration but does not necessarily confirm a suitable degree of air tightness …a suitable degree of air tightness …..therefore an air leakage test may be ..therefore an air leakage test may be needed in addition.” needed in addition.”

– Bowie et al (1963)Bowie et al (1963)

Change is inevitable….Change is inevitable….

That was then…That was then…– Single deep vacuum Single deep vacuum

phase +/- conditioningphase +/- conditioning– Majority of items Majority of items

processed were porous processed were porous in naturein nature

– Surgical instruments Surgical instruments mostly constructed of mostly constructed of metalmetal

– Very few multi-part or Very few multi-part or cannulated devicescannulated devices

This is now…This is now…– Superatmospheric, Superatmospheric,

transatmospheric or transatmospheric or subatmospheric pulsingsubatmospheric pulsing

– Majority of items Majority of items processed are non-processed are non-porousporous

– Surgical instruments Surgical instruments constructed of a variety constructed of a variety of materialsof materials

– Large percentage of Large percentage of multi-part and long-multi-part and long-lumened deviceslumened devices

Is the Bowie & Dick test Is the Bowie & Dick test still relevant?still relevant?

What do you think?What do you think?

What do we need to What do we need to check for?check for?

Chamber integrity – to ensure no air Chamber integrity – to ensure no air leakage is present at any stage of the leakage is present at any stage of the sterilisation cyclesterilisation cycle

Ability of the vacuum pump to eliminate air Ability of the vacuum pump to eliminate air from the chamber and loadfrom the chamber and load

Steam qualitySteam quality

Performance Testing of Performance Testing of Steam SterilisersSteam Sterilisers Air Leakage TestAir Leakage Test

– Establishes that no air leakage will occur Establishes that no air leakage will occur during vacuum stages of the sterilisation during vacuum stages of the sterilisation cyclecycle

Leak rate tests are now an automatic Leak rate tests are now an automatic test cycle on most modern steriliserstest cycle on most modern sterilisers

Performance Testing of Performance Testing of Steam SterilisersSteam Sterilisers Air detectorsAir detectors

– Commonly fitted to most modern Commonly fitted to most modern steriliserssterilisers

– Samples the conditions present in the Samples the conditions present in the steriliser chamber after the air removal steriliser chamber after the air removal stage and during steam admission, in stage and during steam admission, in every cycleevery cycle

– Is set to cause the cycle to abort if Is set to cause the cycle to abort if temperature differences ≥ 2temperature differences ≥ 20 0 C are C are detecteddetected

Performance Testing of Performance Testing of Steam SterilisersSteam Sterilisers Air removal and steam penetration Air removal and steam penetration

testtest– Establishes efficacy of vacuum system Establishes efficacy of vacuum system

and can give an indication of steam and can give an indication of steam quality –i.e. presence of non-condensable quality –i.e. presence of non-condensable gasesgases

Commercially available alternatives to Commercially available alternatives to the original Bowie & Dick test are in the original Bowie & Dick test are in widespread usewidespread use

What Standards are there What Standards are there that refer to B&D tests?that refer to B&D tests?

LOTS!!!!!!LOTS!!!!!!

Which Standards?Which Standards?

EN 867-3:1997 EN 867-3:1997 EN 867-4:2001EN 867-4:2001 ISO 15882:2003ISO 15882:2003 EN 285 / prEN285 (2006)EN 285 / prEN285 (2006) prEN ISO/FDIS 17665-1prEN ISO/FDIS 17665-1 ISO/CD 17665-2ISO/CD 17665-2 ISO 11140 Parts 1-5ISO 11140 Parts 1-5

Just to name the most relevant few………….

ISO 11140 ISO 11140 Sterilisation of Health Sterilisation of Health Care Products – Chemical Care Products – Chemical indicatorsindicators All of these documents are currently under All of these documents are currently under

review…..review…..

– ISO 11140 -3 2000ISO 11140 -3 2000– Part 3 Class 2 indicators for – Part 3 Class 2 indicators for steam penetration teststeam penetration test sheets sheets

– ISO 11140 -4 2001ISO 11140 -4 2001– Part 4 Class 2 indicators – Part 4 Class 2 indicators for steam penetration test for steam penetration test packspacks

– ISO 11140 -5 2000ISO 11140 -5 2000– Part 5 Class 2 indicators for – Part 5 Class 2 indicators for air removal test sheets and packsair removal test sheets and packs

ISO/DIS 11140-3ISO/DIS 11140-3– Specifications only for test indicator Specifications only for test indicator

sheets that are to be used in conjunction sheets that are to be used in conjunction with a standard test pack as described in with a standard test pack as described in EN 285 EN 285

– (Equivalent to original BD pack)(Equivalent to original BD pack)

– This Standard specifies the performance This Standard specifies the performance of the indicator, but not that of the test of the indicator, but not that of the test pack itselfpack itself

ISO/DIS 11140-4ISO/DIS 11140-4– Specifies the performance of the indicator Specifies the performance of the indicator

system in combination with the test load with system in combination with the test load with which it is intended to be usedwhich it is intended to be used May be single or multi-use with a new indicator each May be single or multi-use with a new indicator each

time of usetime of use– Intended to indicate that steam penetration has Intended to indicate that steam penetration has

been inadequate in the case of a number of been inadequate in the case of a number of different causes for fault cyclesdifferent causes for fault cycles

– Does not include test methods to establish the Does not include test methods to establish the suitability of the indicators for use in sterilisers suitability of the indicators for use in sterilisers that that do notdo not use a vacuum stage for air removal use a vacuum stage for air removal

ISO/DIS 11140-5ISO/DIS 11140-5– Specifies the requirements for an indicator and Specifies the requirements for an indicator and

alternative test system used to evaluate the alternative test system used to evaluate the effectiveness of air removal during the effectiveness of air removal during the prevacuum phase of prevacuum steam prevacuum phase of prevacuum steam sterilisation cycles or during the pulsing stage of sterilisation cycles or during the pulsing stage of positive pulsing cyclespositive pulsing cycles

– Failure of the test could be due to retention of Failure of the test could be due to retention of air, an air leak or non-condensable gases during air, an air leak or non-condensable gases during the air removal stagethe air removal stage

Summary of the Summary of the differences differences (ISO 15882)(ISO 15882)

7kg pack7kg pack 7kg pack 4kg pack

Fail condition per 11140-5 (inadequate air removal)

T0 in chamber drain

Fail condition per 11140-3 (Original Bowie & Dick result)

Fail conditions per 11140-4 (Range of Causes)

ISO 15882, Annex A

Which test is right for my Which test is right for my steriliser?steriliser? What air removal system does your steriliser What air removal system does your steriliser

have?have?– SubatmosphericSubatmospheric

– Pulses occur all below atmospheric conditionsPulses occur all below atmospheric conditions

– TransatmosphericTransatmospheric– Pulses occur above and below atmospheric Pulses occur above and below atmospheric

conditionsconditions

– SuperatmosphericSuperatmospheric– Initial vacuum pulses followed by Initial vacuum pulses followed by

superatmospheric pulsessuperatmospheric pulses Check both the steriliser and BD test Check both the steriliser and BD test

manufacturer’s recommendationsmanufacturer’s recommendations

What are you using the What are you using the Bowie and Dick test to do?Bowie and Dick test to do? Check only for adequate air removal?Check only for adequate air removal?

– Select a test compliant with ISO 11140-5Select a test compliant with ISO 11140-5

Check for both air removal and steam Check for both air removal and steam penetration?penetration?– Select a test sheet compliant with ISO11140-3Select a test sheet compliant with ISO11140-3

Check for both air removal, steam Check for both air removal, steam penetration and possible failures due to penetration and possible failures due to other causesother causes– Select a test compliant with ISO11140-4Select a test compliant with ISO11140-4

What to look for in a What to look for in a test…test… Conformance to the applicable EN or Conformance to the applicable EN or

ISO StandardsISO Standards– Independent certification of conformance Independent certification of conformance

in preference to self certificationin preference to self certification– Clear instructions on how to store, Clear instructions on how to store,

handle, use and interpret the testhandle, use and interpret the test– Information on the reliability in Information on the reliability in

maintaining end point changemaintaining end point change

What to look for in a test..What to look for in a test..

The indicator sheetThe indicator sheet– Reagent must cover ≥ 30% of the sheet with no Reagent must cover ≥ 30% of the sheet with no

more than 20mm gap between areas of reagentmore than 20mm gap between areas of reagent– The pattern must enable clear interpretation of The pattern must enable clear interpretation of

the colour changethe colour change– The edges must be able to be compared with The edges must be able to be compared with

the centre and be of A4 size the centre and be of A4 size (ISO 11140-3 only)(ISO 11140-3 only)

– The dye must be non-toxic and non-transferableThe dye must be non-toxic and non-transferable– The indicator itself or the pre-assembled pack The indicator itself or the pre-assembled pack

must allow writing to be made on itmust allow writing to be made on it

Clear colour changeClear colour changeUnprocessed Processed (Pass)

Edges can be compared Edges can be compared to the centreto the centre

Processed (Examples of Failures)

Writing can be made on Writing can be made on the pack or the test sheetthe pack or the test sheet

How to perform the testHow to perform the test

Empty chamber except for chamber Empty chamber except for chamber furniture and the test itselffurniture and the test itself

Locate the test in the geometric centre of Locate the test in the geometric centre of the horizontal plane of the usable chamber the horizontal plane of the usable chamber space between 100-200mm from the space between 100-200mm from the chamber base (EN 285)chamber base (EN 285)– This may or may not be over the chamber drainThis may or may not be over the chamber drain

This is NOT how to use a This is NOT how to use a BD type test !BD type test !

How to perform the testHow to perform the test

The sterilising stage of the cycle must The sterilising stage of the cycle must be no longer than 3 ½ minutesbe no longer than 3 ½ minutes– Many sterilisers now incorporate a pre-set Many sterilisers now incorporate a pre-set

air removal and steam penetration test air removal and steam penetration test cyclecycle

– Drying times should not be extendedDrying times should not be extended

How to interpret the How to interpret the resultresult Standard Procedure to Standard Procedure to

be followedbe followed All staff trained to All staff trained to

interpret the result interpret the result according to according to manufacturer’s manufacturer’s instructionsinstructions

Flat surface and clear Flat surface and clear overhead lightingoverhead lighting

Compare edges to Compare edges to centrecentre

Record KeepingRecord Keeping

There is no specified guidance with There is no specified guidance with respect to the length of time to keep a respect to the length of time to keep a chemical indicator result, even a BD chemical indicator result, even a BD indicatorindicator– ISO 15882 states that users may record ISO 15882 states that users may record

the outcome or result of the indicator, or the outcome or result of the indicator, or choose to retain it for varying periods of choose to retain it for varying periods of time according to local requirementstime according to local requirements

In conclusion…In conclusion…

““We hope that others will use it, We hope that others will use it, perhaps in conjunction with more perhaps in conjunction with more refined methods, to examine refined methods, to examine sterilisers…and in doing so….they will sterilisers…and in doing so….they will collect much needed information about collect much needed information about the current status of sterilisers…”the current status of sterilisers…”

– Bowie et al (1963)Bowie et al (1963)

References and Further References and Further ReadingReading Bowie, J. H., Kelsey, J. C., Thompson, G. R. (1963) Bowie, J. H., Kelsey, J. C., Thompson, G. R. (1963)

The Bowie and Dick Autoclave Tape Test. The Bowie and Dick Autoclave Tape Test. The The Lancet, pp586-587Lancet, pp586-587

Bowie, J. (1984) Bowie, J. (1984) Dr John Bowie on the Bowie and Dr John Bowie on the Bowie and Dick test.Dick test. Journal HSPD March/April Vol 2 No.2 pp Journal HSPD March/April Vol 2 No.2 pp 26-2826-28

Mayworm, D. (1984) Mayworm, D. (1984) The Bowie-Dick type test…Are The Bowie-Dick type test…Are there alternative ways? there alternative ways? Journal HSPDJournal HSPD Vol 2, No. 2Vol 2, No. 2 pp 31-34pp 31-34

Ryan, P. (1984) Ryan, P. (1984) The Bowie-Dick type test…The The Bowie-Dick type test…The discrepancies between theory and practice.discrepancies between theory and practice. Journal Journal HSPD March/April Vol 2, No.2. pp20-24HSPD March/April Vol 2, No.2. pp20-24

References and Further References and Further ReadingReading EN 285 EN 285 Large steam sterilisersLarge steam sterilisers EN 867-3:1997 EN 867-3:1997 Non-biological systems for use in Non-biological systems for use in

sterilisers. Part 3: Specification for Class B sterilisers. Part 3: Specification for Class B indicators for use in the Bowie and Dick test.indicators for use in the Bowie and Dick test.

EN 867-4:2001 EN 867-4:2001 Non-biological systems for use in Non-biological systems for use in sterilisers. Part 4 : Specification for indicators as an sterilisers. Part 4 : Specification for indicators as an alternative to the Bowie and Dick test for detection alternative to the Bowie and Dick test for detection of steam penetration.of steam penetration.

EN EN 867-5:2001 867-5:2001 Non-biological systems for use in Non-biological systems for use in sterilisers. Part 5: Specification for indicator sterilisers. Part 5: Specification for indicator systems and process challenge devices for use in systems and process challenge devices for use in performance testing for small steam sterilisers Type performance testing for small steam sterilisers Type B and Type S.B and Type S.

References and Further References and Further ReadingReading Borchers, U. & Mielke, M. (2004) Borchers, U. & Mielke, M. (2004) How How

material, length, wall thickness and material, length, wall thickness and diameter of hollow devices affect the diameter of hollow devices affect the inactivation of biological indicators when inactivation of biological indicators when subjected to moist heat treatment. subjected to moist heat treatment. Zentral Zentral Sterilisation Vol. 12 (5) pp314-322Sterilisation Vol. 12 (5) pp314-322

Eifler, P. (2004) Eifler, P. (2004) Is the steam OK? The air Is the steam OK? The air detector knows the answer.detector knows the answer. Zentral Zentral Sterilisation Vol. 12 (4) pp279-281Sterilisation Vol. 12 (4) pp279-281

References and Further References and Further ReadingReading ISO 11140 -1 2005 ISO 11140 -1 2005 Sterilisation of Health Care Sterilisation of Health Care

Products – Chemical indicators – Part 1 General Products – Chemical indicators – Part 1 General RequirementsRequirements– ISO 11140 -3 2000ISO 11140 -3 2000– Sterilisation of Health Care Products – – Sterilisation of Health Care Products –

Chemical indicators – Part 3 Class 2 indicators for steam Chemical indicators – Part 3 Class 2 indicators for steam penetration testpenetration test sheets sheets

– ISO 11140 -4 2001ISO 11140 -4 2001– Sterilisation of Health Care Products – – Sterilisation of Health Care Products – Chemical indicators – Part 4 Class 2 indicators for steam Chemical indicators – Part 4 Class 2 indicators for steam penetration test penetration test packspacks

– ISO 11140 -5 2000ISO 11140 -5 2000– Sterilisation of Health Care Products – – Sterilisation of Health Care Products – Chemical indicators – Part 5 Class 2 indicators for Chemical indicators – Part 5 Class 2 indicators for air air removal test sheets and packsremoval test sheets and packs

References and Further References and Further ReadingReading ISO 11139 (draft 2005) ISO 11139 (draft 2005) Sterilisation of Sterilisation of

health care products – Vocabulary 2health care products – Vocabulary 2ndnd editionedition

ISO 15882:2003 ISO 15882:2003 Sterilisation of Health Care Sterilisation of Health Care Products – Chemical indicators – Guidance Products – Chemical indicators – Guidance for selection, use and interpretation of for selection, use and interpretation of resultsresults

ISO 15882 (draft 2005) ISO 15882 (draft 2005) Sterilisation of Sterilisation of health care products – Chemical indicators – health care products – Chemical indicators – Guidance for the selection, use and Guidance for the selection, use and interpretation of results.interpretation of results.

References and Further References and Further ReadingReading ISO/DIS 17665-1ISO/DIS 17665-1 Sterilisation of health Sterilisation of health

care products –Moist Heat – Part 1 care products –Moist Heat – Part 1 Requirements for the development, Requirements for the development, validation and routine control of a validation and routine control of a sterilisation process for medical devicessterilisation process for medical devices

ISO/CD 17665-2 ISO/CD 17665-2 Sterilisation of health care Sterilisation of health care products – Moist Heat – Part 2 Guidance products – Moist Heat – Part 2 Guidance on the application of ISO 17665-1.on the application of ISO 17665-1.

AS 1410 – 2003 AS 1410 – 2003 Sterilisers-Steam-Sterilisers-Steam-PrevacuumPrevacuum