Sterilization of narrow channels: how to ensure effectiveness in daily routine? Dr.ir. Josephus Paulus Clemens Maria Van Doornmalen Gomez Hoyos

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1 April 2015 Sterilization of narrow channels: how to ensure effectiveness in daily routine? Dr.ir. Josephus Paulus Clemens Maria Van Doornmalen Gomez Hoyos 3M Deutschand GmbH, IPD, Decontamination University of Technology Eindhoven, department of physics Dutch delegate in standard committees on decontamination Contents Steam sterilization conditions Physical validation Steam penetration Non condensable gases Porous loads and hollow channels Experiments + calculations for tubes Alternatives for the Bowie & Dick test Helices? 1

Eindhoven, department of physics Dutch delegate in standard committees on decontamination Contents Steam sterilization conditions

2 Vessel with only water molecules Superheated (surfaces not wet) saturated p T diagram of steam Supersaturated (wet loads afterwards) Data of Perkins can be used if the steam is close enough to saturation Accepted values of Perkins Steam quality in hospitals Safety margins time (min) Perkins temperature [ C] time (min) MRC temperature [ C] Working Party on Pressure Steam Sterilizers of the Medical Research Council. Sterilisation by steam under increased pressure. Lancet 1959; 28:

margins time (min) Perkins temperature [ C] 2 132 8 125 12 121 time (min) MRC temperature [ C] 3 134 10 127 15 121 4 Working Party on

3 From traditional instruments to hollow instruments Surface Stean Sterilization conditions Saturated steam, e.g., 134 C for 3 minutes On all surfaces Pressure Phase 1: Conditioning Phase 2: Sterilization Phase 3: Drying and pressure equilibration Time 3

, 134 C for 3 minutes On all surfaces Pressure Phase 1:

4 Process: removing air atmospheric pressure time residual air instrument with lumen in steam sterilizer Process: steam inlet atmospheric pressure time steam residual air instrument with lumen in steam sterilizer 4

sterilizer Process: steam inlet atmospheric pressure

5 Process: sterilization atmospheric pressure time Interface broadens by diffusion 1 1 s 50 1 h instrument with lumen in steam sterilizer Steam penetration in a tube Experiments with optical sensor Model with convection, diffusion no condensation on inner surface of tube 5

sterilizer Steam penetration in a tube Experiments with optical sensor

6 Steam penetration in a tube Steam penetration in a tube 3 vacuum pulses p v = 10 kpa Bowie & Dick test gives a pass result Sufficient steam penetration only for tube lengths < 20 cm J. Phys. D: Appl. Phys. 46, (2013) 6

7 Steam penetration in a tube Helix: a good test? In principle measures steam penetration Large chamber at end of tube is a problem Flow in tube may be disturbed Indicator may not be accurate Chemical indicators often used Helix schematically Tube Receptacle 7

tube is a problem Flow in tube may be disturbed Indicator may

8 Helix: a good test? Chamber enhances steam fraction at the tube end effect on tube of 2 mm diameter Helix: a good test? Examples Helix schematically Tube Receptacle 8

9 Test of Hollow A PCD Hollow A PCD according to ISO TC 198 WG Standard test pack CI with complete 134 C, 3 min. Temperature depression T c T p < 2 C Test of Hollow A PCD p v is varied Tests in a small (11 liter) and large (340 liter) sterilizer 9

Temperature depression T c T p < 2 C Test of Hollow A PCD p v is

10 Test of Hollow A PCD Small (11 liter) sterilizer Color change around 35 kpa Test of Hollow A PCD Large (342 liter) sterilizer Color change around 35 kpa 10

11 Steam penetration in a tube 3 vacuum pulses p v = 10 kpa open tube of 10 cm No condensation within tube J. Phys. D: Appl. Phys. 46, (2013) 11

12 Heat capacity and condensation length 10 cm both ends open stainless steel 5x1 mm PTFE 0.5 or 5 mm Model calculations including condensation Standard process with 3 vacuum pulses p v = 10 kpa Ideal steam quality assumed: air fraction in chamber below 10-3 Effect of air: Δp= 0.3kPa, ΔT= 0.04 C PTFE outer tube 0.5 mm T = 90 C at last p v Sufficient steam penetration 12

$v = 10 kpa Ideal steam quality assumed: air fraction in chamber below 10-3 Effect of air:$

13 PTFE outer tube 0.5 mm T = 90 C at last p v Aimed sterilization temperature reached PTFE outer tube 0.5 mm T = 90 C at last p v Film thickness ~ 60µm 13

14 PTFE outer tube 5 mm T = 90 C at last p v Insufficient steam penetration PTFE outer tube 5 mm T = 90 C at last p v Aimed sterilization temperature not reached 14

PTFE outer tube 5 mm T = 90 C at last p v Film thickness ~ 0.6mm Danger of clogging Standards ISO 17665 part 2

15 PTFE outer tube 5 mm T = 90 C at last p v Film thickness ~ 0.6mm Danger of clogging Standards ISO part 2 EN 285 clause note The hollow load test complements these tests and should be regarded as an addition to, and not asareplacementtothem. EN 867-5: Small sterilizers unable to accommodate a sterilization module (600 mm x 300 mm x 300 mm) cannot be tested using the tests described in EN 285:1996 for large sterilizers for wrapped goods and porous loads either because the chamber size is unable to accommodate the standard test packs or because the efficacy of the tests is impaired when the test pack occupies a large proportion of the chamber volume. 15

EN 867-5: Small sterilizers unable to accommodate a sterilization module (600 mm x 300 mm x 300 mm) cannot be tested using the tests described in EN 285:1996 for large

16 Process Challenge Devices and load control At this moment: No PCDs are defined in standards German standard DIN 58921:2011 Test method to demonstrate the suitability of a medical device simulator during steam sterilisation -Medical device simulator testing; Text in German and English. Is NOTa European or ISO standard A NWIP (ISO part 6) amy be in progress to replace the EN 867 part 5. (In voting). (This standard will not specify a every load PCD) Conclusions Measuring steam penetration by a standard helix has some serious drawbacks large volume of measurement chamber unclear / wrong indicator results It is possible to predict and measure how steam penetrates in narrow tubes Develop appropriate steam penetration tests (e.g., including properties of materials, orientation and conditioning ) Measure steam penetration directly Measure amount of NGC s (ETS?) Rev. Sci. Instrum. 84, (2013) Current state of the art is a BI in a test pack 16

Penetration tests according to the ISO 11140

Space for 3M Montage Penetration tests according to the ISO 11140 Josephus Paulus Clemens Maria van Doornmalen Gomez Hoyos Outline Purpose penetration tests ETS Alternatives for original Bowie and Dick