Medical Market Laboratory EMEA

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Medical Market Laboratory EMEA

Penetration tests in according to the ISO 11140

Josephus P.C.M van Doornmalen Gomez Hoyos

Croatia, March 27, 2009

2


Medical Markets Laboratory (Europe)

Outline

� Purpose penetration tests

� Original Bowie and Dick test

� Alternatives for original Bowie and Dick test

� Norms

� Conclusions

3



Sterilization conditions

� Sterilization conditions:

� 100 % saturated steam

� At the aimed temperature, e.g., 134 °C

� For the right amount of time, e.g., 134 °C for 3 minutes

� On all surfaces

� Textile fibers

� Inside of tubes

4



• The task of the BDT is to check pre-vacuum sterilisers

independently from their own gauges etc. for:

• Air removal

• Steam penetration

• Routine (Daily) test

for (steam) sterilizer

AirAir

SteamSteam

??

The task of the BDT

5



The History of the Bowie and Dick Test

• First mentioned in 1961:

"Recent Developments in the Sterilization of Surgical

Materials";

Report of a symposium organised by the Pharmaceutical

Society of Great Britain

• Description of the Test in 1963:

"THE BOWIE AND DICK

AUTOCLAVE TAPE TEST"

THE LANCET, March 16, 1963

6



The original Bowie and Dick Test Pack

• 29 "Huckaback-Towels"

• Each 36 x 24 inch in size (91 x 61 cm)

• Washed prior to the test

• Unfolded and aired prior to a test for at least one hour

• Folded 3 times to give 8 layers

• Stack 11 inch high (28 cm)

7



The original Bowie and Dick Test Pack

• 2 lengths of 12 inch (30 cm)

autoclave tape, "type 1222"(Minnesota Mining and Manufacturing Company)

• In the form of a

St. Andrew’s cross on

a sheet of unglazed paper

• In the middle of the stack

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THE BOWIE AND DICK AUTOCLAVE TAPE TEST, The Lancet, (1963), S.586

The original "Huckaback Towel Pack" as set up byDr. J. H. Bowie and Mr. J. Dick

9



250 ml

residual air

Reasons for BDT failure

• Bad vacuum

• Leak

• Non-condensable

gases

10



Time

Pressure

Phase 1:

Conditioning

Phase 2:

Sterilization

Phase 3:

Drying and

pressure equilibration

Process: Vacuum assisted sterilisers

11



CEN Towel Pack

Bowie and Dick: CEN Towel Pack

• EN 285 (26.1)

• Plain, bleached cotton

sheets

• Size: 90 x 120 cm

• Threads: warp 30 +/- 6

weft 27 +/- 5

• Stack size: 22 x 30 x 25 cm

• Wrapped in similar fabric

• Weight: 7 kg +/- 10%

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EN 285:2006+A1:2008 (E)

� Bowie and Dick package

and test defined

� Dimensions

� Material

� Way of folding

� Conditioning

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Bowie and Dick package simplified

30 cm

22 cm

25 cm

14



Steam sterilization process

Time

Pressure

Start of sterilization phase

Steam sterilization condition

Suction

Steam injection

15



Air (gas mix) removal

Time

Pressure

16



Steam injection

Time

Pressure

17



Steam penetration and condensation

Time

Condensation front

Gases sucked out, textile stays wet

Good penetration

18



Insufficient deep vacuum

� Condense front will not disappear

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None condensable gases in steam

� Water vapour condenses on surfaces colder than the

vapour

� Gases that will not condense in similar conditions are called

None Condensable Gases

� Oxigen (O2), Nitrogen (N2), Carbon dioxide (CO2)

� Possibilties of introduced in the steam:

� Feed water

� Too smal dimension of steam boiler

� Leak in pipe work, vessel

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Effect NCG’s

O2, N2, CO2, H2O

Steam Injection

(Steam with NCG’s)

Condensation of water

Steam injection, pressure increasing

21



steam

steam

steam

steam

NCG’s do not change their volume

during condensation.

Non-condensable gases

22



The temperature depression

Drain

Temperature:

135°C

Temperature:

130°C

Example

Temperature

depression

5 K

23



The Air Pocket

at 4,5 cm height

The air pocket’s form is not a perfect ball,

but egg shaped.

At 10 cm height

Animation

24



When to perform a penetration test

� EN 554

� 6.3.4 Process control and monitoring: "If the sterilization process includes air removal from the product, a steam penetration test shall be carried out at the commencement of each day the sterilizer is to be used."

� A.4.3 Routine monitoring and testing:"e) a steam penetration test (when specified).Note. A suitable penetration test for a saturated steam process is being prepared by CEN/TC 102.

� CEN/TC102 WG7 prepared EN 867-4

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EN ISO 17665

� 12.1.6 Process control and monitoring: "If the sterilization process relies on the removal of air from the sterilizer chamber in order to achieve rapid and even penetration of steam into the sterilizer load, a steam penetration test shall be carried out each day before the sterilizer is used."

� A.6.2 Routine monitoring and testing:"An alternative test pack may be used providing the challenge to the sterilization process has been demonstrated to be equal to or greater than the challenge from the standard test pack described in A.3.”

� Statements to the same effect can be found in EN 554 which will be replaced by EN ISO 17665.

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31300 Disposable Test

Pack

Alternative Products

• Alternative Bowie & Dick

Test products

• Increased reproducibility

• Constant test conditions

• Performance requirements

are covered by a

dedicated standard

(EN ISO 11140 - 4)

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What the norms say

� Towel pack according to EN 285 with:

an Indicator test sheet in compliance with EN ISO 11140-3

or

alternative indicators according to EN ISO 11140-4

28



Examples hollow instruments

Lumen

29



Helix Examples

Lumen

Helix schematically

Tube Receptacle

30



Time

Pressure

Length = L

Length = ½L Closed end

Penetration in lumen

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Relatively easy to penetrate

Relatively difficult to penetrate

Configuration of instruments

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Lumen as representative for lumen

� Material of lumen

� Multi layers of different materials

� Heat transfer

� Heat capacity

� Dimension (length tube, radius tube,

� Dimension of the tube:

� Length of the tube

� Radius of the tube

� Thickness of the tube

Lumen

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Wall thickness

Wall thickness

More heat capacity

(e.g., more condensation)Research ongoing

Heat transfer

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Dimensions of tube

Radius

rLenghth

Research ongoing!

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Swirl

� Well known and described phenomena

Axial dispersion and flow phenomena in helically ciled tubular reactors for flow analysis and

chromatography, R. Tijssen, Analytica Chimica Acta, 114, 1980, 71-89:

Swirl

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EN ISO 11140-4 and EN 867-5

� The helix or hollow A is postulated in the EN867-5 and is to

be used in small sterilizers (type B and N processes

according to EN13060)

� Steam penetration test for large sterilizers (EN285) should

be a Bowie & Dick test or an alternative, as described in the

EN ISO 11140-4

� So far, no scientific proof has been found in literature (1).

(1) Publications in a scientific journal with an impact factor

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Proving for alternative tests

� Show that the alternative test is reacting as the original

Bowie and Dick test.

� Experimental data Bowie and Dick test

� Experimental data for alternative

� Comparison between data Bowie and Dick test and alternative

test

11111212 1313 1414

1515 16161717 1818 1919

23232525 2626

2727 2929 31313333

35353939 4040 4141

4242 434345454444 4646

4747

20202424

2121

28283434

2222

30303232

3636 37373838

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Hollow A and helix

� Is the hollow A of Helix a good representation of your

instruments with narrow lumen?

� Is a postulated test

� Is for small sterilizers type B and S

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Current situation

� ISO working group is started to write ISO 11140 part 6

� This standards is meant to address Process Challenge

devices

� Research concerning penetration in lumen is on going

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Conclusions

� Penetration is an daily equipment test

� Penetration tests must fulfil ISO 11140 part 3 or part 4

� Documented evidence must be available foe end users

� Experiments

� Data

Documents

Medical Market Laboratory EMEA