Medical Market Laboratory EMEA Space for 3M Montage Penetration tests according to the ISO 11140 Josephus P.C.M van Doornmalen Gomez Hoyos Croatia, March 27, 2009
Outline Purpose penetration tests Original Bowie and Dick test Alternatives for original Bowie and Dick test Norms Conclusions 2
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 fibres Inside of tubes 3
The task of the BDT 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 Steam? Air 4
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 5
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) 6
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 7
The original "Huckaback Towel Pack" as set up by Dr. J. H. Bowie and Mr. J. Dick THE BOWIE AND DICK AUTOCLAVE TAPE TEST, The Lancet, (1963), S.586 8
Reasons for BDT failure Bad vacuum Leak Non-condensable gases 250 ml residual air 9
Process: Vacuum assisted sterilisers Pressure Phase 1: Conditioning Phase 2: Sterilization Phase 3: Drying and pressure equilibration Time 10
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% CEN Towel Pack 11
EN 285:2006+A1:2008 (E) Bowie and Dick package and test defined Dimensions Material Way of folding Conditioning 12
Bowie and Dick package simplified 25 cm 30 cm 22 cm 13
Steam sterilization process Steam injection Start of sterilization phase Steam sterilization condition Pressure Time 14 Suction
Air (gas mix) removal Pressure Time 15
Steam injection Pressure Time 16
Steam penetration and condensation Condensation front Gases sucked out, textile stays wet Good penetration 17 Time
Insufficient deep vacuum Condense front will not disappear 18
Effect NCG s Steam Injection (Steam with NCG s) O 2, N 2, CO 2, H 2 O Steam injection, pressure increasing Condensation of water 19
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 Oxygen (O 2 ), Nitrogen (N 2 ), Carbon dioxide (CO 2 ) Possibilities of introduced in the steam: Feed water Too small dimension of steam boiler Leak in pipe work, vessel 20
Non-condensable gases steam steam steam steam NCG s do not change their volume during condensation. 21
The temperature depression Example Temperature: 130 C Temperature depression 5 K Temperature: 135 C 22 Drain
The Air Pocket Animation The air pocket s form is not a perfect ball, but egg shaped. 23 At 10 cm height at 4,5 cm height
Slow warming up Pressure Phase 1: Conditioning Phase 2: Sterilization Phase 3: Drying and pressure equilibration Time 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 25
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. 26
Alternative Products Alternative Bowie & Dick Test products Increased reproducibility Constant test conditions Performance requirements are covered by a dedicated standard (EN ISO 11140-4) 31300 Disposable Test Pack 27
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 Helix schematically Tube Receptacle Lumen 30
Lumen as representative for lumen Lumen Dimension of the tube: Length of the tube Radius of the tube Thickness of the tube Material of lumen Multi layers of different materials Heat transfer Heat capacity Dimension (length tube, radius tube) 31
Penetration in lumen Pressure Time Length = L 32 Length = L Closed end
Configuration of instruments Relatively difficult to penetrate Relatively easy to penetrate 33
Swirl Swirl Well known and described phenomena Axial dispersion and flow phenomena in helically coiled tubular reactors for flow analysis and chromatography, R. Tijssen, Analytica Chimica Acta, 114, 1980, 71-89: 34
Wall thickness Wall thickness More heat capacity (e.g., more condensation) Heat transfer Research ongoing 35
Dimensions of tube Radius Length r Research ongoing 36
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 S 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 37
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 35 11 12 13 14 15 16 17 18 19 21 20 22 24 25 26 27 28 29 30 31 32 33 34 36 38 37 39 40 41 42 43 44 45 46 47 23 38
Hollow A and helix Is the hollow A of Helix a good representation of your instruments with narrow lumen? Is a postulated test Postulates for small sterilizers type B and S 39
Current situation At this moment there only: B&D test or alternative big sterilizers Postulated test for small sterilizers 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 40
Conclusions Penetration is a daily equipment test Penetration tests must fulfil ISO 11140 part 3 or part 4 Documented evidence for alternative tests must be available fore end-users: Experiments Data Research and data are needed 41