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Browne International 2006Browne International 2006

Relevance of the BowieRelevance of the Bowieand Dick Test today ??and Dick Test today ??

Peter NewsonPeter Newson

Albert Browne InternationalAlbert Browne International


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ObjectivesObjectives

Daltons law and the Bowie and Dick testDaltons law and the Bowie and Dick test Practical experiments conducted inPractical experiments conducted in

Sterilization Research LabsSterilization Research Labs

Independent Certification and ValidationIndependent Certification and Validation

ConclusionConclusion


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DaltonDaltons Laws Law

In theory, it is possible to detect theIn theory, it is possible to detect thepresence of air in steam by measuringpresence of air in steam by measuringand comparing the pressure andand comparing the pressure and

temperaturetemperature 1 bar of steam + 1 bar of steam = 2 bar1 bar of steam + 1 bar of steam = 2 bar

temperature = 134temperature = 134CC

1 bar of air + 1 bar of steam = 2 bar1 bar of air + 1 bar of steam = 2 bar

temperature 13temperature 13C coolerC cooler


4/39Browne International 2006Browne International 2006

SteamSteam

0

0.5

1

1.5

2

2.5

100 121 134

Temperature (C)

Pressure

(Bar)

Phase boundary line



The Bowie Dick TestThe Bowie Dick Test

50 Years On50 Years On



Origins of the Bowie DickOrigins of the Bowie DickTestTest

Published in 1963 in the Lancet byPublished in 1963 in the Lancet byBowie, Kelsey and ThompsonBowie, Kelsey and Thompson

Devised by Bowie and DickDevised by Bowie and Dick

Inspired by work by Scott, Henry andInspired by work by Scott, Henry and

Savage, dated back to preSavage, dated back to pre--19371937


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Bowie Dick Test TodayBowie Dick Test Today

Is the Bowie Dick test still relevantIs the Bowie Dick test still relevanttoday?today?

We donWe dont sterilize packs of towels liket sterilize packs of towels like

we used to!we used to!

Does the Bowie Dick test accuratelyDoes the Bowie Dick test accurately

assess steam penetration?assess steam penetration?


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Experimental DetailsExperimental Details


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Experimental DetailsExperimental Details Inject air into a sterilizerInject air into a sterilizer

Measure the effect inMeasure the effect in 1 Empty chamber1 Empty chamber

2 Chamber loaded with a tray of surgical2 Chamber loaded with a tray of surgical

instrumentsinstruments 3 Chamber loaded with 4 trays of surgical3 Chamber loaded with 4 trays of surgical

instrumentsinstruments

4 Chamber loaded with 7 kg towel pack4 Chamber loaded with 7 kg towel pack 5 Chamber loaded with Bowie Dick pack5 Chamber loaded with Bowie Dick pack


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Empty ChamberEmpty Chamber

Research sterilizerResearch sterilizer Chamber volume 400 litresChamber volume 400 litres

Rather thanRather thanleakleak air into the chamber,air into the chamber,

air wasair was injectedinjected into the chamber at ainto the chamber at adefined pointdefined point

The quantity of air injected wasThe quantity of air injected wasgradually increasedgradually increased


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Air Injection PointAir Injection Point

Air injection


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ResultsResults Empty ChamberEmpty Chamber

No air injectedNo air injectedTemperature and pressure were asTemperature and pressure were as

dictated by steam tables i.e. correct fordictated by steam tables i.e. correct for

saturated steamsaturated steam

As the volume of air was increased,As the volume of air was increased, nono

fault could be detectedfault could be detected bybytemperature vs. pressure comparisonstemperature vs. pressure comparisons


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Single TraySingle Tray Sterilizer loaded withSterilizer loaded with single tray ofsingle tray of

instrumentsinstruments used commonly in hospitalsused commonly in hospitals

Trays wrapped inTrays wrapped in

NonNon--woven paper (Westfield Medical)woven paper (Westfield Medical) Woven PTFE textileWoven PTFE textile

SpunSpun--bonded polypropylene (Kimberly Clark)bonded polypropylene (Kimberly Clark)

Wrapping techniques used as recommendedWrapping techniques used as recommendedby wrap manufacturerby wrap manufacturer


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ResultsResults Single TraySingle TrayThe paper tray wrap producedThe paper tray wrap produced 2 or 32 or 3C ofC of

superheatsuperheat, so it was difficult to compare, so it was difficult to comparetemperature vs. pressure.temperature vs. pressure.

With the other materials, locations within theWith the other materials, locations within thetray near to the instruments aftertray near to the instruments after 1% air1% airinjection showed temperature / pressureinjection showed temperature / pressure

variationsvariations slightly largerslightly larger than Daltonthan Daltons Laws Lawwould suggestwould suggest


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ConclusionsConclusions Single TraySingle TrayThe tray contents areThe tray contents are drawing steamdrawing steam, and, and

with it, airwith it, air

TheThe concentrated airconcentrated air (rather than evenly(rather than evenly

distributed) would account for thedistributed) would account for the nonnon--DaltonDaltonbehaviourbehaviour

It is not uncommon that hydrophilic materialsIt is not uncommon that hydrophilic materials

such as cotton and paper produce smallsuch as cotton and paper produce smallamounts ofamounts ofexothermic superheatexothermic superheat


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MultitrayMultitray

Thermocouples were placed throughoutThermocouples were placed throughoutthe chamber and traysthe chamber and trays

Cycles were run firstly with no air, thenCycles were run firstly with no air, then

with varying quantities of air injectedwith varying quantities of air injected


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ResultsResults -- MultitrayMultitray Again the paper tray wraps produced 2 orAgain the paper tray wraps produced 2 or

33C of superheat, so it was difficult toC of superheat, so it was difficult tocompare temperature vs. pressure.compare temperature vs. pressure.

No air injectedNo air injected Temperature and pressure were as dictated byTemperature and pressure were as dictated by

steam tables i.e. correct for saturated steamsteam tables i.e. correct for saturated steam

As the volume of air was increased,As the volume of air was increased, no faultno faultcould be detectedcould be detected by temperature vs.by temperature vs.pressure comparisonspressure comparisons


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ConclusionsConclusions -- MultitrayMultitray

Air is beingAir is being sharedshared, or distributed,, or distributed,amongst the 4 traysamongst the 4 trays

No fault was evidentNo fault was evident


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ResultsResults 7kg Towel Pack7kg Towel Pack WithWith

no air injectedno air injected, pressure and, pressure and

temperature monitoring showedtemperature monitoring showed nonodeviationdeviation from normalfrom normal

When injecting air, volumes as small asWhen injecting air, volumes as small as0.02%0.02% (i.e. 50 times smaller than for a(i.e. 50 times smaller than for a

single tray) of the chamber volumesingle tray) of the chamber volumecreated significant fault conditionscreated significant fault conditions


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ConclusionsConclusions 7 kg Towel7 kg TowelPackPack

The 7 kg towel pack isThe 7 kg towel pack is highly efficienthighly efficientat concentrating any available airat concentrating any available air

This concentration easily showsThis concentration easily shows

discrepancies between temperaturediscrepancies between temperature

and pressure readingsand pressure readings


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Bowie Dick Test PackBowie Dick Test Pack

Single Use Bowie Dick Test Pack,Single Use Bowie Dick Test Pack,validated to EN867validated to EN867 4, was placed in4, was placed in

the chamber as indicated by thethe chamber as indicated by the

manufacturermanufacturer


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ResultsResults -- Bowie Dick TestBowie Dick TestPackPack

When no air was injected, the resultWhen no air was injected, the resultwas pass resultwas pass result

When air injection of 0.02% of chamberWhen air injection of 0.02% of chamber

volume was injected, a large fail resultvolume was injected, a large fail result

was obtained.was obtained.


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ConclusionsConclusions -- Bowie DickBowie DickTest PackTest Pack

The disposable Bowie Dick Pack isThe disposable Bowie Dick Pack iscalibrated against the 7kg towel pack,calibrated against the 7kg towel pack,

so it is not surprising that it performsso it is not surprising that it performs

similarly to itsimilarly to it


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Research ConclusionsResearch Conclusions

In an empty chamber,In an empty chamber, air is veryair is verydifficult to detectdifficult to detect as it is randomlyas it is randomlydistributed throughout the chamberdistributed throughout the chamber

A single tray of instruments willA single tray of instruments will attractattracta significant amount of aira significant amount of air towardstowards

the tray, suppressing the temperaturethe tray, suppressing the temperatureby severalby several CC


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Research ConclusionsResearch Conclusions

Air will be distributed betweenAir will be distributed between

severalseveraltraystrays, and will be difficult to detect by, and will be difficult to detect bytemperature/pressure measurementstemperature/pressure measurements

AA 7 kg towel pack7 kg towel pack still remains one ofstill remains one ofthethe most demanding challengesmost demanding challenges for afor aporous load sterilizerporous load sterilizer

The performance of a validated BowieThe performance of a validated BowieDick Pack matches the towel packDick Pack matches the towel pack


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Research ConclusionsResearch Conclusions It isIt is not possible to show presence ofnot possible to show presence ofairair in a steam environment unless thein a steam environment unless thepressure and temperature probes havepressure and temperature probes have

identical (rapid) response times and canidentical (rapid) response times and canaccurately measure less thanaccurately measure less than 0.3 mbar0.3 mbar

Air will only be detected if there isAir will only be detected if there isa load or challenge to concentratea load or challenge to concentratethe airthe air


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The Bowie Dick TestThe Bowie Dick Test

It can be seen that it is theIt can be seen that it is the principleprinciple ofofthe Bowie Dick test which is importantthe Bowie Dick test which is importantbecause the same principles for steambecause the same principles for steam

sterilization still apply today, just as theysterilization still apply today, just as theydid in the 1930did in the 1930ss


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StandardsStandards

In order to ensure that Alternative BowieIn order to ensure that Alternative BowieDick tests and other chemical indicatorsDick tests and other chemical indicators

comply to minimum requirements, wecomply to minimum requirements, we

have standards.have standards.


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Importance of StandardsImportance of Standards Standards define important minimumStandards define important minimum

safety factors for productssafety factors for products

EN 867EN 867--4 specifies these requirements4 specifies these requirements

for disposablefor disposable--type Bowie Dick teststype Bowie Dick tests EN 867EN 867--1 and ISO 111401 and ISO 11140 1 & 21 & 2

But conformance to these standards areBut conformance to these standards aredeclared by the product manufacturersdeclared by the product manufacturersthemselvesthemselves


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Limitations of standardsLimitations of standards

Self certifyingSelf certifying No overseeing bodyNo overseeing body

Opportunity for fraudulent claimsOpportunity for fraudulent claims

What is the solution for REAL peace ofWhat is the solution for REAL peace of

mindmind


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Independent ValidationIndependent Validation& Certification& Certification


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New productsNew products

The user or purchaser of a product mayThe user or purchaser of a product maytake one of 3 options:take one of 3 options:

assume that it could not be sold unless itassume that it could not be sold unless it

was satisfactorywas satisfactory take the word of the manufacturer ortake the word of the manufacturer or

suppliersupplier

seek independent verificationseek independent verification


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A DeclarationA Declaration

A declaration about a product or serviceA declaration about a product or servicemay be :may be :

self certifiedself certified

i.e a declaration made by the producti.e a declaration made by the productmanufacturer or service providermanufacturer or service provider

independentindependent

i.e the product or service has been assessedi.e the product or service has been assessed

by aby a recognisedrecognised test house andtest house and

a certificate appropriately issueda certificate appropriately issued


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Self CertificationSelf Certification Relies on the manufacturer or serviceRelies on the manufacturer or service

provider to give an accurate and honestprovider to give an accurate and honestclaimclaim

There is potential for abuseThere is potential for abuse generally used for products that do notgenerally used for products that do not

have a significant safety elementhave a significant safety element


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Independent CertificationIndependent Certification

Cannot be abused as the manufacturerCannot be abused as the manufactureror service provider has no inputor service provider has no input

Often required when the product orOften required when the product or

service has a strong safety elementservice has a strong safety element


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Independent assessorsIndependent assessors

Often called test houses, accreditationOften called test houses, accreditation

bodies or notified bodiesbodies or notified bodies

They are regulated and controlled byThey are regulated and controlled by

competent authoritiescompetent authorities


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EN 45011EN 45011 -- General requirementsGeneral requirementsfor bodies operating productfor bodies operating product

certification systemscertification systems

Services available to all applicantsServices available to all applicants

Be impartialBe impartial

Have a documented structureHave a documented structure Have a quality systemHave a quality system

Be free from any commercial or financialBe free from any commercial or financial

pressurespressures Award a quality certificate and internationallyAward a quality certificate and internationally

recognised quality markrecognised quality mark


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SummarySummary

The Bowie Dick pack isThe Bowie Dick pack is scientificallyscientificallyprovenproven as still being relevant andas still being relevant and

accurate for the demands of today'saccurate for the demands of today's

Sterile Services Managers.Sterile Services Managers.


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ConclusionConclusion

You all validate and document theYou all validate and document the

processes in your department.processes in your department.

Ensure that the products you are usingEnsure that the products you are using

are Validated.are Validated.

If you donIf you dont ask the question no onet ask the question no one

else will !else will !Be a demanding customerBe a demanding customer

Date post:	03-Apr-2018
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