Health Technical Memorandum 01-06: Decontamination of ... · Health Technical Memorandum 01-06: Decontamination of flexible endoscopes: Part E – Testing methods Preface Introduction

Health Technical Memorandum 01-06: Decontamination of flexible endoscopesPart E: Testing methods

March 2016

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Health Technical Memorandum 01-06: Decontamination of flexible endoscopes: Part E – Testing methods

Health Technical Memorandum 01-06: Decontamination of flexible endoscopesPart E: Testing methods

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Preface

IntroductionThis HTM supersedes the Choice Framework for local Policy and Procedures (CFPP) series, which was a pilot initiative by the Department of Health.

The CFPP series of documents are reverting to the Health Technical Memorandum title format. This will realign them with HTM 00 – ‘Policies and principles of healthcare engineering’ and ‘HTM 01-05: Decontamination in primary care dental practices’ and the naming convention used for other healthcare estates and facilities related technical guidance documents within England. It will also help to address the recommendation to align decontamination guidance across the four nations.

In 01-01 and 01-06 DH will be retaining the Essential Quality Requirements and Best Practice format, this maintains their alignment with HTM 01-05 and the requirement of ‘The Health and Social Care Act 2008: Code of Practice on the prevention and control of infections and related guidance’ which requires that “decontamination policy should demonstrate that it complies with guidance establishing essential quality requirements and a plan is in place for progression to best practice”. We are aware that policy within the devolved nations differs on this particular issue but the aim is that the technical content should be consistent and able to be adopted by the devolved nations so that the requirements of the ACDP-TSE Subgroup’s amended guidance can be met.

The purpose of HTM is to help health organisations to develop policies regarding the management, use and decontamination of reusable medical devices at controlled costs using risk control.

This HTM is designed to reflect the need to continuously improve outcomes in terms of:

•patient safety;

• clinical effectiveness; and

•patient experience.

Essential Quality Requirements and Best PracticeThe Health Act Code of Practice recommends that healthcare organisations comply with guidance establishing Essential Quality Requirements and demonstrate that a plan is in place for progression to Best Practice.

Essential Quality Requirements (EQR), for the purposes of this best practice guidance, is a term that encompasses all existing statutory and regulatory requirements. EQRs incorporate requirements of the current Medical Devices Directive and Approved Codes of Practice as well as relevant applicable Standards. They will help to demonstrate that an acute provider operates safely with respect to its decontamination services.

Local policy should define how a provider achieves risk control and what plan is in place to work towards Best Practice.

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Best Practice is additional to EQR. Best Practice as defined in this guidance covers non-mandatory policies and procedures that aim to further minimise risks to patients; deliver better patient outcomes; promote and encourage innovation and choice; and achieve cost efficiencies.

Best Practice should be considered when developing local policies and procedures based on the risk of surgical procedures and available evidence. Best Practice encompasses guidance on the whole of the decontamination cycle, including, for example, improved instrument management, where there is evidence that these procedures will contribute to improved clinical outcomes.

The HTM 01 suite is listed below.

•HTM 01-01: Management and decontamination of surgical instruments (medical devices) used in acute care

•HTM 01-04: Decontamination of linen for health and social care

•HTM 01-05: Decontamination in primary care dental practices

•HTM 01-06: Decontamination of flexible endoscopes.

Note

This guidance remains a work in progress which will be updated as additional evidence becomes available; each iteration of the guidance is designed to help to incrementally reduce the risk of cross-infection.

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Abbreviations

ACDP: Advisory Committee on Dangerous Pathogens

ACDP-TSE [Subgroup]: Advisory Committee on Dangerous Pathogens – Transmissible Spongiform Encephalopathies [Subgroup]

AE(D): Authorising Engineer (Decontamination)

BS: British Standard

CJD: Creutzfeldt-Jakob disease

CQC: Care Quality Commission

DH: Department of Health

DIPC: Director of Infection Prevention and Control

EN: European norm

EWD: endoscope washer-disinfector

HCAI: healthcare-associated infections

HCAI Code of Practice: DH’s ‘Health and Social Care Act 2008: Code of Practice for the NHS on the prevention and control of healthcare associated infections and related guidance’

ISO: International Standards Organisation

MHRA: Medicines and Healthcare products Regulatory Agency

sCJD: sporadic Creutzfeldt-Jakob disease

TSEs: transmissible spongiform encephalopathies

vCJD: variant Creutzfeldt-Jakob disease

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Executive summary

Health Technical Memorandum (HTM) 01-06 provides best practice guidance on the management and decontamination of flexible endoscopes (principally gastrointestinal scopes and bronchoscopes). In addition, this guidance also provides advice on the management and handling of an endoscope following use on a patient at increased risk of vCJD.

This document covers flexible endoscope management and decontamination only. Clinical issues relating to endoscopy or the manufacture of EWDs are not discussed. In addition this document does not cover the processing of flexible endoscopes used to examine sterile body tissues. These endoscopes should be sterile, possibly using low temperature gas sterilization (for compatible processes, see HTM 01-01 Part E).

HTM 01-06 is divided into five parts:

•Part A ‘Policy and management’ sets the Department of Health’s (DH) policy context and discusses the Essential Quality Requirements and Best Practice recommendations for an endoscope decontamination service. Transmissible spongiform encephalopathy (TSE) infectious agents are discussed and guidance is given on the management and handling of an endoscope after it has been used on a patient at increased risk of vCJD.

•Part B ‘Design and installation’ gives guidance on the design and fitting of endoscope reprocessing units.

•Part C ‘Operational management’ gives guidance on operational responsibility together with advice on the procurement and operation of an endoscope washer-disinfector (EWD).

•Part D ‘Validation and verification’ highlights the types of tests and maintenance procedures that are needed to ensure that decontamination has been achieved.

•Part E ‘Testing methods’ discusses the principles and methods that are used in the tests described in this HTM and the tests detailed in BS EN ISO 15883-4.

Why has the guidance been updated?HTM 01-06 has been updated to take account of changes to the ACDP-TSE Subgroup’s general principles of decontamination (Annex C). In relation to the decontamination of flexible endoscopes, paragraphs C5 and C20 from the Annex state:

Paragraph C5:

For endoscopes, the bedside clean should take place immediately after the procedure has been carried out, and it is recommended that the endoscopes should be manually cleaned according to the manufacturer’s recommendations and passed through an Endoscope Washer Disinfector as soon as possible after use.

Paragraph C20:

A routine test for washer disinfectors could be developed to measure the cleaning efficacy at validation and routine testing, such as daily or weekly tests. This method could be based on a process challenge device system that will monitor the optimised wash cycles; the results must be quantifiable and objective.

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/427855/Annex_C_v3.0.pdf

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/427855/Annex_C_v3.0.pdf

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Essentially, therefore, this update focuses on improving the washing and cleaning process, reducing the time from patient use to the decontamination process, and monitoring the cleaning efficacy of endoscope washer-disinfectors.

It is also important to point out that the ACDP-TSE Subgroup’s Annex C deprecates the use of ninhydrin in the detection of protein levels because of its insensitivity. Alternative available technologies should be considered for the detection of residual proteins on the internal surfaces of flexible endoscopes following reprocessing. Therefore reprocessing units should:

a. consider the available technologies and make a risk-based decision on the methodology to be adopted (for example BS EN ISO 14971);

b. use technologies with the best available sensitivity, consistent measurement standards and quantifiable results to measure effective control of residual protein levels;

c. use trend analysis as a tool for self-improvement to demonstrate decreasing protein levels over time both on the outside of the endoscope and the lumens using available testing technologies.

Note

This remains a work in progress which will be updated as additional evidence becomes available.

List of major changes to Part E since the 2013 edition

•CFPP 01-06 has reverted to the Health Technical Memorandum title format and now becomes Health Technical Memorandum 01-06.

• “Automatic control test” changed to daily test from weekly test to make it consistent with schedule in HTM 01-06 Part D. This was an error in the previous edition.

•New process challenge device efficacy test introduced.

•New advice on tests for residual protein detection introduced.

•Previous tests for residual soil using ninhydrin and alternative methods now removed as they are no longer applicable.

•New test given in Chapter 6 for detection of Pseudomonas aeruginosa in final rinse-water.

•All references updated.

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Acknowledgements

Andrew Bent Medicines & Healthcare products Regulatory Agenc

Anita C. Jones University of Edinburgh

Bill Keevil University of Southampton

Brian Kirk IHEEM Decontamination Technology Platform

Clive Powell Association of British Healthcare Industries

David Perrett Queen Mary University of London

Geoff Sjogren Institute of Decontamination Sciences

Geoffrey L. Ridgway, OBE, MD Clinical Microbiologist

Gerry McDonnell Association of British Healthcare Industries

Graham Stanton NHS Wales Shared Services Partnership – Facilities Services

Helen Griffiths Joint Advisory Group on gastrointestinal endoscopy (JAG)

Jackie Duggan Public Health England

James Ironside University of Edinburgh

Jimmy Walker Public Health England

John Singh Health Estates, Northern Ireland

Karen Chell NHS Supply Chain

Katy Sinka Public Health England

Mike Painter Public Health Physician

Mike Simmons Public Health Wales

Miles Allison British Society of Gastroenterology

Peter Hoffman Public Health England

Robert Kingston IHEEM Decontamination Technology Platform

Rod Herve University of Southampton

Sulisti Holmes Health Protection Scotland

Tony Young Southend University Hospital NHS Foundation Trust

Tracy Coates Association for Perioperative Practice

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Contents

Preface ..................................................................................................................................... iv

Abbreviations ........................................................................................................................... vi

Executive summary ................................................................................................................ vii

Acknowledgements ................................................................................................................. ix

1 Introduction ..........................................................................................................................1

2 Terminology ..........................................................................................................................2

3 Automatic control test ..........................................................................................................3

4 Drainage ................................................................................................................................4

5 Venting system .....................................................................................................................7

6 Water system ........................................................................................................................8

7 Doors and door interlocks .................................................................................................. 18

8 Chemical dosing .................................................................................................................20

9 Instrumentation fitted to an EWD ......................................................................................21

10 Load carriers .....................................................................................................................22

11 Thermometric tests ...........................................................................................................23

12 Load dryness ....................................................................................................................27

13 Chemical additive residual levels .....................................................................................28

14 Air quality ..........................................................................................................................29

15 Sound pressure test .........................................................................................................30

16 Cleaning efficacy tests .....................................................................................................31

17 Leak and patency testing .................................................................................................35

18 EWD self-disinfection test ................................................................................................39

19 Disinfectant concentration test ........................................................................................42

20 Microbiological and temperature tests of disinfection efficacy ......................................43

References ..............................................................................................................................45

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1 Introduction

1 Introduction

1.1 This volume discusses principles and methods that are used in the tests described in this HTM and those detailed in BS EN ISO 15883 Parts 1 and 4.

1.2 EWDs for flexible thermo-labile endoscopes are machines of Type 1 or 2:

• Type 1 EWDs have a single door or lid entry.

• Type 2 EWDs have two doors and a pass-through facility.

1.3 (Rigid endoscopes able to tolerate terminal steam sterilization are considered under WDs for surgical instruments.)

1.4 EWDs are characterised by a chemical disinfection stage because the endoscopes to

be processed will not withstand the high temperatures required for thermal disinfection. It is necessary to ensure that the disinfectant is removed from the endoscope before it is used on a patient; this is achieved by a post-disinfection rinsing stage. Some EWD process cycles are available that add disinfectant to the final rinse-water. The level of disinfectant at this stage should be shown to be non¬toxic to patients. The microbiological control of this stage is of critical importance to the microbial status of the reprocessed endoscope. A number of additional tests are required to ensure that this aspect of the process is properly controlled.

1.5 Periodic storage cabinet tests for flexible endoscopes are given in Chapter 6 of HTM 01-06 Part D – ‘Validation and verification’.

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2 Terminology

Cycle variables 2.1 The cycle variables are the physical and chemical properties such as time, temperature, pressure, flow rate, concentration, chemical composition that influence the efficacy of the cleaning and disinfection processes. Many of the tests described in this HTM require the values of cycle variables to be determined experimentally and then compared with specified or standard values.

2.2 An indicated value is that shown by a visual display fitted to the EWD.

2.3 A recorded value is that shown on the output of a recording instrument fitted permanently to the EWD.

2.4 A measured value is that shown on a test instrument, for example, a temperature recorder attached to the EWD for test purposes.

2.5 A noted value is that written down following personal observation of an indicated, recorded or measured value.

Disinfection conditions 2.6 The disinfection conditions are the ranges of the cycle variables that may prevail throughout the chamber and load during the holding time.

2.7 Endoscope disinfection conditions are specified by the disinfection temperature band (if above ambient) and disinfectant concentration range. The disinfection temperature band may be ambient temperature or elevated above the incoming water temperature to a defined level. A minimum acceptable temperature, known as the

disinfection temperature, and a maximum allowable temperature define the disinfection temperature band.

2.8 Flexible endoscopes can withstand temperatures up to 60°C, above which damage is likely to occur. EWDs that dilute disinfectant with water directly from the supply will vary in their operation owing to the variation in the supply water temperature and chemistry, particularly between seasons. The disinfectant contact concentration is specified by the minimum acceptable concentration in contact with the load to be disinfected and the maximum allowable concentration.

2.9 For those EWDs in which the chemical disinfection stage, or the cleaning stage, is thermostatically controlled at elevated temperature, the duration of the exposure to the chemical may be determined thermometrically. In most cases, investigation of the performance of chemical disinfection processes can only be carried out successfully using microbiological test methods in conjunction with physical testing.

2.10 The disinfection temperature band (if above ambient) may also be quoted for liquid chemical disinfection/sterilization processes, but is not a complete specification of the disinfection conditions, since the efficacy of such processes also depends on the concentration of the chemical agent.

2.11 Some EWDs use elevated temperature for the self-disinfection stage. Control of this stage is critical and should be monitored thermometrically to determine the correct conditions have been met in all parts of the EWD chamber.

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3 Automatic control test

3 Automatic control test

3.1 The automatic control test is designed to show that the operating cycle functions correctly as shown by the values of the cycle variables indicated and recorded by the instruments fitted to the EWD.

3.2 In the absence of an independent monitoring system (IMS), this test is carried out daily and is the main test for ensuring that the EWD continues to function correctly within the validated parameters. The IMS records should be checked in conjunction with the test.

Test procedure 3.3 Place a test device or a routine endoscope in the chamber. Select the routine operating cycle and start the cycle.

3.4 Ensure that a traceability record is made of the test. Note chamber temperatures (if appropriate), leak test pressure and time at all significant points of the operating cycle, for example the beginning and ending of each stage or sub-stage.

3.5 The test should be considered satisfactory if the following requirements are met:

a. A visual display indicating “cycle complete” occurs.

b. During the whole of the operational cycle, the values of the cycle variables as indicated by the instruments on the EWD or shown on the batch process record are within the limits established as giving satisfactory results either by the manufacturer or during validation.

c. If elevated temperatures are used during the routine cycle, the time for which the temperature is maintained is not less than that established during validation.

d. The door cannot be opened until the cycle is complete.

e. The person conducting the test does not observe any mechanical or other anomaly.

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4 Drainage

4.1 It is important to vent the EWD externally to prevent any hazardous fumes entering the workspace. This applies both to the drains that should be sealed within the EWD work area and to the EWD cabinet. There is no test to determine if any gas contents of the EWD chamber or drain enter the workspace. Therefore if a potentially hazardous chemical is used as the disinfectant, such as peracetic acid, gas measurements should be taken around the EWD during operation to determine whether there are any leaks in the system.

Blocked-drain protection 4.2 If the drain from the EWD chamber becomes blocked, continued operation of the EWD would allow water and suspended soil to be discharged onto the floor either during the operating cycle or, for cabinet-type EWDs with sealed door(s), by sudden discharge when the door is opened at the end of the cycle.

4.3 The purpose of blocked drain protection is to prevent unacceptable spillage and minimise the risk of cross-infection.

4.4 In the test, the drain is deliberately blocked, and successive operating cycles are run until the water level is above the level of the door seal. The test is intended for use both as a type test (and as such is a requirement of BS EN ISO 15883-4) and as an operational or installation test.

Equipment and materials 4.5 Either a solid metal sphere of diameter 10–15% greater than the internal diameter of the

trap or a large ballvalve is used to obstruct the discharge from the drain.

Method for EWDs with sealed doors 4.6 Introduce the metal sphere (or equivalent device) to block the drain, or fit a large ballvalve and close the valve.

4.7 Close the door and start the operating cycle. On completion of the operating cycle, attempt to open the EWD door using the normal release procedure.

4.8 If the door opens and the water level is below the door seal, close the door and start another operating cycle.

4.9 Repeat the operating cycle as many times as necessary for either the water level at the end of the cycle to be above the level of the door seal or a fault to be indicated.

Method for EWDs without sealed doors 4.10 Introduce the metal sphere (or equivalent device) to block the drain or ballvalve adjusted to the closed position.

4.11 Start the operating cycle. On completion of the operating cycle, if no water has been spilled from the EWD and no fault has been indicated, start another operating cycle.

4.12 Repeat the operating cycle as many times as necessary for either water to be spilled from the EWD or a fault to be indicated.

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4 Drainage

Results for EWDs with sealed doors 4.13 A fault should be indicated when, or before, the water level in the chamber reaches the level of the door seal. The door should not be capable of being opened by the normal release procedure; a tool, key or code should be required.

Results for EWDs without sealed doors 4.14 A fault should be indicated before water is spilled from the EWD. The operating cycle should be stopped preventing further inflow of water. A tool, key or code should be required to restart the EWD.

NoteThis test might not be required if the design of the EWD prevents the water level within the chamber or bowl reaching the level of the opening.

Free draining of tanks, chamber, load carriers and pipework 4.15 Residual water that does not drain from the internal pipework of the EWD may provide an environment for microbial growth; these microorganisms may recontaminate the disinfected load.

4.16 The following checks should be carried out during type-testing, works testing and installation testing to verify that – as designed, built and installed – the EWD will effectively discharge all the water from the system:

a. free draining of chamber and load carriers – test by visual observation at end of the cycle;

b. free draining of tanks – test by visual observation on draining the tanks;

c. pipework flow to discharge point – test by visual observation including use, when necessary, of a spirit level.

Efficacy of discharge through the trap 4.17 The test is intended to verify that the operating cycle is effective in purging the trap of all waste and soil.

Equipment and materials 4.18 The following equipment and materials are necessary:

• test soil appropriate to the type of EWD being tested (see guidance given in ‘Performance qualification tests’ in the ‘Validation and verification’ volume);

• sampling tube of sufficient length to reach the water trap in the drain of the EWD and a sampling pump (for example, a pipette pump or syringe).

Method 4.19 The test may be carried out as part of the cleaning efficacy test during operational testing.

4.20 On completion of an operating cycle to test the cleaning efficacy by processing a full load contaminated with an appropriate test soil, place the sampling tube into the water trap and remove a sample for examination.

4.21 Examine the water sample from the trap for residual test soil using the detection method appropriate to the test soil.

Results 4.22 The water in the trap should be free from residual soil at the same level of detection as that specified for the load items.

Residual soil in the trap may present an infection or recontamination hazard.

Estimation of dead volume of pipework 4.23 Residual water that does not drain from the internal pipework of the EWD may provide

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an environment for microbial growth; these microorganisms may then recontaminate the disinfected load.

4.24 The test is intended primarily as a type test but may also be of value, if possible, as an operational test or when investigating microbial contamination occurring in an EWD.

4.25 The test should only be carried out after completion of the checks for free drainage (see paragraph 4.15, ‘Free draining of tanks, chamber, load carriers and pipework’) have been satisfactorily completed.

Equipment 4.26 Volumetric measuring vessels of appropriate size are necessary.

Method 4.27 The pipework of the EWD that is known to be dry (either following disassembly and

reassembly or purging with dry compressed air for not less than 30 minutes) is flushed with a known volume of water (simulating the flow that would occur in normal use).

4.28 The volume of water flushed through the system should be twice that determined as the volume used per operating cycle given in the manufacturer’s data sheet. The volume of water discharged is measured, and the dead volume (estimated as the volume retained) is calculated from the difference between the two values.

4.29 When the EWD has two or more pipework systems that are entirely separate (for example, for flushing water, wash-water, rinse-water, final rinse-water), each system may be tested separately.

Results 4.30 The volume of retained water should be less than 1% of the volume of water used.

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5 Venting system

5 Venting system

Load contamination from ductwork 5.1 The evolution of water vapour from the chamber during the washing stage, disinfection stage and drying stage may result in condensation occurring in the ductwork and in the condenser (if fitted). The ducting is commonly arranged to allow this condensate to drain back into the chamber or drain. This condensate is likely to become contaminated and there is a risk that it could come in contact with the load. The ductwork should be checked at installation to confirm that any condensate from the ductwork cannot drain into the EWD chamber and onto the load.

Droplet emissions 5.2 Emissions of water droplets present a risk of transmitting infection from contaminated load items. The test is designed to be carried out as an operational test.

Equipment and materials 5.3 The following equipment is necessary: cold hand mirror.

Method 5.4 The EWD should be operated with the chamber empty except for any chamber furniture (for example, load carrier). Any chemical additives used should be replaced with water.

5.5 Close the door of the EWD. Initiate an operating cycle. The cold mirror is moved around the edge of the door or lid at a distance of 50–100 mm from the door or lid.

5.6 If the mirror shows any signs of misting or the presence of droplets, its position should be noted.

Result 5.7 There should be no misting of the mirror or droplets present. Misting or droplets on the mirror indicates the discharge from around the door or lid.

Chemical vapour emission 5.8 EWDs use chemical additives for which there may be specified exposure limits (usually disinfectants) under the COSHH Regulations. It must be ensured that emissions from the EWD do not cause personal exposure to exceed the legal limits.

Method 5.9 The method of sampling for airborne emissions and the method of analysis or detection will be specific to the chemical additive(s) being used. Advice should be sought from the EWD manufacturer, the supplier of the chemical additive(s) and/or the Health & Safety Executive (HSE) in order to determine an appropriate test method.

Results 5.10 Emissions from the EWD during normal operation and maintenance, including when opening the EWD at the end of the cycle or when changing or refilling chemical additive reservoirs, should not expose personnel to concentrations in excess of the legal maxima.

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6 Water system

6.1 A continuous supply of water of the specified chemical and microbial quality is essential to the correct functioning of all EWDs. Water that is too hard or has too high a concentration of total organic carbon may impair the activity of detergents (or require the use of increased quantities of chemical additives) and cause deposits, scaling or corrosion of the items being processed.

6.2 Water containing high numbers of microorganisms may recontaminate disinfected items. For all these tests, the water should be sampled from the water supply to each EWD or the EWD chamber/bowl. Additional samples may need to be taken from any water treatment plant when trying to identify the cause of non¬conformity.

6.3 Periodic final rinse-water tests and satisfactory results are shown in Table 1.

Table 1 Periodic final rinse-water tests: satisfactory results

Water test (click on link)

Satisfactory results

Frequency

Total organic carbon Less than 1 mg/L Yearly

Appearance Clear, bright and colourless

Yearly

pH 5.5 to 8.0 Yearly

Electrical conductivity Less than 40 µS/cm at 25ºC

Weekly

Hardness Less than 50 mg/L CaCO3

Weekly (if appropriate)

Total viable count (see also Table 3 in HTM 01-06 Part B)

Less than 10 cfu/100 mL acceptable

Weekly

Environmental mycobacteria

Non-detected in 100 mL samples

Quarterly

Pseudomonas aeruginosa Non-detected in 100 mL samples

Quarterly

Water samples 6.4 Water samples should be obtained from either:

•draw-off points installed at convenient locations within the system for testing the supply; or

• the EWD chamber or bowl for testing the water rinsing the endoscope.

6.5 The sampling containers used should be specific for the contaminants of interest. This should include, as appropriate:

a. 250 mL sterile, chemically clean, single-use containers (for determination of TOC levels and/or total viable count);

b. containers supplied by the laboratory for measurement of chemical contents, for example:

(i) 1 L acid-washed borosilicate bottles, (for determination of cations);

(ii) 1 L polypropylene bottles (for determination of anions and total dissolved solids);

(iii) 100 mL high-density polyethylene bottles (for determination of pH and conductivity).

6.6 The first 100 mL of sample taken at each sampling point should be run to waste.

6.7 Samples for TVC should be chilled and tested within four hours of collection or stored at 2–5°C and tested within 24 hours of collection.

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6 Water system

Water quality tests 6.8 The following sections describe analytical methods that may be used to determine the various biological, physical and chemical properties of water samples.

6.9 The methods of analysis required to detect chemical contaminants at low concentrations with a high level of accuracy require the use of a laboratory with appropriate expertise, facilities and experience. Other tests can be carried out on-site or with limited laboratory facilities; these lack the precision and sensitivity of laboratory tests, but are sufficient for most purposes.

6.10 This HTM contains detailed procedures for tests that may be carried out on-site or with very simple laboratory equipment at, or shortly after, the time of sampling.

6.11 The precision, accuracy, sensitivity and limits of detection of these methods are usually inferior to those of laboratory methods. They are useful, however, in that they provide evidence of any gross failure, and the results are available immediately, making them of diagnostic value during a fault-finding exercise.

Choice of method 6.12 For any given determinant there will usually be several methods that are suitable and cover the range of concentrations of interest. The methods given in this section are examples of tests that may conveniently be carried out on site.

6.13 A number of test systems are available commercially. Before adopting one of these methods, care should be taken to ensure that the test(s) provides results of sufficient accuracy and sensitivity. The User is responsible for obtaining the test data and will require the assistance of the AE(D) and AP(D) to decide how the tests are carried out and who carries them out.

6.14 It is not necessary to use experienced chemical analysis staff to undertake these on-site tests. It is, however, essential that personnel

receive appropriate training before attempting to carry out this work. Recourse to more precise analysis may be needed in the event of a dispute between two parties.

Water supply temperature 6.15 The water supplied to the various stages of the EWD operating cycle should be at an appropriate temperature. If the temperature of the water supplied to the flushing stage is too high (>45°C), there is a risk of coagulating proteinaceous soiling, which will inhibit the cleaning process. If the temperature of water supplied to the EWD is heated and its temperature is too low, washing, rinsing and disinfection stages may be greatly extended or ineffective.

6.16 Water supplied to an EWD may be limited to 30°C within the EWD; therefore, water supply pipes running parallel to a hot water supply may not be cool enough in warm weather to be acceptable.

6.17 Storage of water between 10°C and 55°C is liable to become contaminated unless good water hygiene is practised (see Health Technical Memorandum 04-01 for further guidance).

Equipment

6.18 An indicating or recording thermometer is necessary.

Method

6.19 The temperature of the water supply should be measured from a sampling point as close to the EWD as possible. Place the temperature sensor in the middle of the flowing stream as close as practicable to the sampling point. Allow the water to flow for at least a minute before the temperature is read.

Alternative method (for periodic testing)

6.20 When it is not convenient, or practicable, to run the water to waste from a sampling point close to the EWD, the water temperature may be estimated by measurement of the

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temperature of the outer surface of the supply pipe. If this method is to be used, the correlation between the temperature of the water flowing out of the pipe and the surface temperature of the pipe at a particular point should be established during installation testing. The surface temperature should be measured using a sensor designed for the purpose, and the manufacturer’s instructions for ensuring good thermal contact with the surface should be followed. The temperature should be noted or recorded during a normal operating cycle not less than 30 seconds after the start of water flow through the pipe to the EWD.

Results

6.21 The noted value should be within the temperature range specified for the installation.

Water supply pressure 6.22 If the pressure of the water supply to the EWD is below the minimum pressure specified by the manufacturer, the performance and productivity of the EWD will be adversely affected.

6.23 If the pressure of the water supply to the EWD is above the maximum pressure specified by the manufacturer, the capacity of overflow devices may be inadequate, the designed performance characteristics of valves etc may be exceeded, and in extreme cases there may be the risk of damage to components of the EWD or to the products being processed. (For example, many flexible endoscopes are likely to be damaged if subjected to internal pressures greater than 35 kPa.)

6.24 This test should be carried out as an installation and/or operational test. It should be repeated when any change is made to the water services supplying the EWD (including the connection or removal of additional machines).

Equipment

6.25 A pressure indicator or recorder (0–10 bar) is necessary.

Method

6.26 The pressure sensor should be connected to each of the water supply pipes to the EWD, as close to the EWD as may be practicable, on the supply side of the EWD isolating valve for that supply. The static pressure when the valve is closed and the pressure indicated throughout a normal operating cycle should be recorded or observed and noted. When the water service also supplies other equipment on the same supply line, the test should be run both with the other equipment operating throughout the test (or their operation simulated by an appropriate discharge to waste) and with no other equipment operating.

Results

6.27 The water pressure should remain within the supply pressure limits specified by the EWD manufacturer. The test may be repeated if there is more than one water supply (for example, mains water and pure water).

Appearance 6.28 All the water supplied to the EWD should be clean, colourless and free from visible particulate matter. The appearance of the sample is assessed visually.

Equipment

6.29 The following equipment is necessary:

• clean clear-glass bottle and stopper;

• filter paper (qualitative grade), filter funnel and holder.

Method

6.30 A water sample should be transferred to a clear colourless glass bottle, which should then be tightly stoppered. The sample should be shaken well and examined visually against a white background with a black line running through the middle, preferably in a north light.

6.31 If the sample is turbid, it should be filtered through a qualitative grade filter paper. The filter

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6 Water system

paper should be examined and a description of the retained material reported. The filtrate should then be visually examined for deposits.

6.32 The appearance should be reported in terms of both colour and the intensity of any colour. If the sample is coloured, it should be examined carefully to see whether evidence of colloidal material is present.

6.33 To determine whether there is a problem with water deposits, draw off approximately 300–500 mL of water into a clean glass beaker or jar. Allow the water to settle and any air bubbles to disperse. Then examine the sample against a white sheet with a black line across the centre under a good light. The water should appear crystal clear with a distinct line between the black and white areas. The presence of fine deposits will be seen as slight opalescence and a slightly indistinct edge to the black to white areas.

Results

6.34 All the samples tested should be clear, bright and colourless.

pH 6.35 Two suitable methods for on-site measurement of pH are available; the colour disc comparator and portable pH meter. If colour comparators are used, the operator should undertake a colour blindness test to confirm they are able to read the results.

Equipment

6.36 The following equipment is necessary:

a. pH meter:

(i) There are several commercially available small, portable pH meters. A number of these include built-in temperature compensation. Although they provide suitable accuracy for most general applications, they are not well suited to measurement of pH in solutions of low ionic strength. Their use for the determination of pH

in water of high purity may give unstable or unreliable readings.

(ii) Only those pH meters specifically designed for the measurement of low ionic strength solutions should be used for determining the pH of deionised or RO water.

b. Colour disc comparator:

(i) Colorimetric tests for pH are suitable for high purity, low conductivity, and water samples of the type to be tested.

(ii) Since colorimetric methods are being used for other field tests, this may be the more appropriate method.

(iii) The accuracy is limited and discrimination may not be better than 0.2 pH. This is, however, quite suitable for field tests.

(iv) Colour, turbidity or strong oxidants in the sample all interfere with the test.

(v) A narrow range indicator (or two for use on successive samples) should be chosen to cover the required pH range from 4 to 8. Manufacturers of colorimeters usually provide indicators to cover a range from 2 or 3. Wide range indicators should not be used because of their poor discrimination.

Method

6.37 The test kit should be operated in accordance with the manufacturer’s instructions. Particular attention should be paid to using accurate volumes of both sample and reagent, and monitoring both temperature and reaction time.

6.38 The colour of the reacted sample is matched against the calibrated colour disc viewed through a blank sample. The value in pH units is read directly from the disc.

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6.39 The calibration should be verified using standard buffer solutions made up in advance and kept in capped bottles until required. The buffer solutions should be chosen to have a pH in the midpoint of the range of calibrated colour discs to be used in the determination.

Results

6.40 The indicated value should be in the range 5.5 to 8.0.

NotePhotometric apparatus with somewhat better discrimination is also commercially available.

Electrical conductivity

Equipment and materials

6.41 A meter suitable for measuring the final rinse-water of a EWD should cover the following range:

Range Resolution Accuracy

0–199 µS/cm 0.1 µS/cm ±1% full scale

6.42 It should be temperature-compensated over the range 0–40ºC.

Method

6.43 The meter’s calibration should be verified against commercial standards or 0.0005 molar solutions of potassium chloride and pure water can be used as working standards. These give conductivities at 25ºC of 84 µS/cm and <0.06 µS/cm.

6.44 The potassium chloride solutions may be prepared by dilution of a 0.1 molar solution.

6.45 The working standards are stable for up to one week when stored in cool condition, in a well-stoppered container.

6.46 A comprehensive range of standard conductivity reference solutions, including pure water standards (also known as absolute water), are available commercially, standardised

at 25ºC and traceable to national standard reference materials.

6.47 After calibration, the sample cup, or immersion probe, should be thoroughly rinsed with pure water.

6.48 The sample should be collected in a high-density polyethylene bottle and tested as soon as practicable.

6.49 An aliquot of the sample should be poured into the sample cup of the conductivity meter or, for meters with an immersion probe, into the clean beaker. The meter manufacturer’s instructions for making the measurement should be followed; this will usually require a short stabilisation period before noting the reading.

Results

6.50 The conductivity at 25ºC should not exceed 40 µS/cm for final rinse-water in contact with the reprocessed endoscope, unless it contains a biocide.

Hardness 6.51 Hardness of water is due to the presence of dissolved salts of the alkaline earth metals (calcium, magnesium and strontium). Their presence causes limescale formation from heated or evaporated water. This may inactivate detergents and disinfectants and cause scaling on load items.

Method a: ISE method

6.52 Ion-selective electrodes (ISE) can detect calcium and divalent cations (total hardness). ISEs are not specific for a particular ion but have a relative selectivity for a particular ion or group of ions. They provide a potentiometric response to the activity of the ions in solution. The activity is proportional to the concentration for solutions of the same ionic strength.

6.53 Both analyte and calibration standard solutions should be adjusted to the same ionic strength. A high impedance millivoltmeter is

13

6 Water system

used to measure the potential between the ISE and a suitable reference electrode. The measured potential is proportional to the logarithm of the concentration of the ion(s) in solution.

6.54 The optimum working pH range is 4–9 and the ionic strength of the sample should be adjusted for ionic strength. An adjustment buffer consisting of 4 M potassium chloride solution is often used. Phosphate buffers should not be used, since the calcium activity will be lowered by complexation or precipitation.

6.55 The electrodes are free from any major interference except zinc ions. They are however poisoned by a number of biological fluids.

6.56 The calcium electrode requires a single junction reference electrode. Calibration is made against two or more standard solutions. These are commercially available.

Range

6.57 Calcium-selective electrodes should have a Nernstian response for concentrations from 1 M down to about 5 x 10–6 M and a selectivity ratio of better than 2000 against magnesium. This range is suitable for analysis of softened water and purified water (RO or deionised water).

Method b: titrimetric method

6.58 Commercially available kits for the titrimetric determination of both total hardness and calcium hardness are available. They are based on the same reaction in which divalent cations are complexed with the disodium salt of ethylenediaminetetraacetic acid (EDTA). When the reaction is carried out, at pH 10–11, with Eriochrome Black as the complexometric indicator, all the calcium and magnesium ions are chelated by the EDTA, and the absence of free calcium and magnesium ions causes a colour change in the indicator.

6.59 At pH values above 12, magnesium ions are precipitated as the hydroxide and do not react with the EDTA. Calcium hardness can be

determined using Patton and Reeder’s indicator as a complexometric indicator.

6.60 The commercially available kits often use novel titration methods instead of burettes. The test reagents are specific to each kit. The manufacturer’s instructions should be followed.

Range

6.61 Determinations within the range 5–400 mg/L can be made. The method is not applicable to purified water or condensate from clean or pure steam, which should have calcium concentrations well below the range for accurate determinations.

Results

6.62 The hardness expressed as mg/L CaCO3 should be within the following parameters:

•<50 mg/L for final rinse-water and water used to dilute chemicals;

• 50–200 mg/L for water used in the rinsing stages;

•>200 mg/L not suitable for use in an EWD (if this is the only water grade available, pre-softening is essential).

Total viable count 6.63 Endoscopes should be rinsed after the disinfection stage to remove any residual chemical toxicity. The rinse-water should be free from extraneous material, both inorganic and organic including microorganisms, which could compromise the patient. Routine total viable counts (TVCs) should be made on the final rinse-water. If this water is collected from the EWD bowl/chamber, it will have passed through the water treatment system and internal pipework of the machine. The TVC results will give an indication of the water treatment system performance and microbial colonisation of the EWD pipework. If the TVC is high, additional samples can be taken to determine the problem source.

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6.64 The following test should be carried out as an installation or operational test and as a weekly periodic test for EWDs. It should be carried out by a microbiologist or those trained in aseptic techniques.


6.65 The following equipment and materials are necessary:

a. sterile single-use containers with a volume of at least 250 mL;

b. sterile filter membranes (47 mm diameter, <0.45 µm pore size);

c. suction filtration apparatus;

d. incubator at 30±2ºC;

e. R2A agar (see BS EN ISO 15883-1, Annex D) (alternatively yeast extract agar (YEA) or tryptone soya agar (TSA) may be used;

f. f70% alcohol and non-woven wipes.

Method: sample collection

6.66 Samples of final rinse-water should be taken from the EWD using aseptic techniques following the manufacturer’s instructions. If these are not available, the advice of the AE(D) should be sought. One of the following methods may apply.

(1) From the EWD bowl – recommended

6.67 The following equipment will be required:

•A sampling tube made up of a length of heat-resistant tube from the EWD bowl to a sampling bottle held below the bowl water level. The tube should be fitted with a normally closed valve and a weight attached to one end. The tube and fittings should be sterilized before use.

•A water sampling container.

6.68 The EWD is run with an empty bowl using a special cycle that allows the cycle to be

stopped during the final rinse with the bowl full of water.

6.69 During the final-rinse stage of the EWD cycle, stop the machine and the open the lid or door. With gloved hand, remove the sterile sampling tube from its wrap and place the weighted end in the EWD bowl final rinse-water.

6.70 With the syringe pushed onto the open end of the sampling tube, draw water down the tube with the valve open. When the tube is full, close the valve and remove the syringe.

6.71 Allow water to flow from the sampling tube to waste, then open the sampling bottle and direct the water sample into the bottle. When the sample bottle is full, cap and label the container with details of the sampling point and the time and date the sample was collected.

(2) Using a sample bottle included in the EWD load

6.72 This is an alternative method of sample collection with two outlets fitted to the lid. One connection is fitted to an EWD outlet via a length of plastic tube. The other connection is fitted with a short length of tube and left open.

6.73 During the EWD cycle, the bottle is irrigated by the EWD process liquids, with the last liquid being the final rinse-water. On completion of the cycle, or if aborted at the end of the final rinse stage, the bottle is removed from the EWD and the connections removed from the bottle and the openings sealed. The full bottle of final rinse-water is labelled with details of the sampling point and the time and date the sample was collected and sent to the microbiology laboratory.

6.74 The EWD manufacturer may describe other methods of final rinse-water collection.

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6 Water system

Table 2 Total viable count results guide

Aerobic colony count in 100 mL Interpretation/action Colour grade

Less than 1 Satisfactory Green

1–9 on a regular basis Acceptable – indicates that bacterial numbers are under a reasonable level of control Yellow

10–100 Risk assessment required to investigate potential problems and super-chlorinate or repeat EWD self-disinfect Orange

Over 100 Risk assessment required to consider taking EWD out of service until water quality improved Red

Notes:

Microbiological results from weekly tests should be plotted on a graph to give a trend. This will allow the “normal” and “unusual” results to be distinguished for a particular situation. Investigation of unusual or unsatisfactory results can then be undertaken if results demand (for example, if routine results are below 10 cfu/100 mL, occasionally some of the results may be above 10 cfu/100 mL).

If a bacterial count above 10 cfu/100 mL is obtained from test water, identification of the species is advised. If a significant proportion of the microbes appear the same species from their colonial morphology, carry out an oxidase test to presumptively identify Pseudomonas spp. Then if the test is positive, further investigations are required to determine whether Pseudomonas aeruginosa is present.

Adapted from: Willis, C. (2006). “Bacteria-free endoscopy rinse water – a realistic aim?” Epidemiology and Infection. Vol. 134 No. 2, pp. 279–284.

NoteThe final rinse-water may contain antibacterial chemicals. If this is likely, a sterile neutralising agent should be added to the container before sterilization. This will prevent bacteria from dying during transport to the laboratory. As disinfectants used in EWDs contain a mixture of antibacterial agents, advice from the disinfectant manufacturer will be required to select a suitable neutralising agent.

(3) From a collection tap

6.75 Wipe the discharge surfaces of the sampling point thoroughly with 70% alcohol, and allow to evaporate to dryness.

6.76 Run off not less than 500 mL through the sampling point and discard.

6.77 Using aseptic handling techniques, collect not less than 250 mL of sample in the sterile container from running water and close the lid securely. Label the container with details of the sampling point and the time and date the sample was collected.

6.78 If a sample is to be taken from an EWD bowl, a length of sterile tube and sterile syringe

will be required. One end of the tube is anchored in the bowl that is full of test water, the other end attached to the syringe and a siphon set up so that the bowl water sample can be delivered into the test bottle without contamination.

6.79 The sample should be chilled, transferred to the laboratory and tested within four hours; if this is not possible, the sample should be stored at 2–5ºC for not more than 24 hours before testing.

Method: testing

6.80 Filter a 100 mL aliquot of the sample through a 0.45 µm filter. Aseptically transfer the filter to the surface of a R2A, TSA or YEA plate and incubate at 30±2ºC. Examine the plates after 48 hours’ incubation and at five days. If an urgent report is required, preliminary readings could be made at 48 hours’ incubation and a final report issued after five days’ incubation. Carry out the test in duplicate.

6.81 Examine the filters and record the number of colony forming units (cfu) that are visible.

Results

6.82 For EWD final rinse-water, see Table 2.

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6.83 The above levels are suggested values (see the ‘Water quality and water treatment’ section in the ‘Design and installation’ volume); if an endoscope requires a higher level of decontamination, a risk assessment will be needed.

Environmental mycobacteria 6.84 Environmental non-pathogenic mycobacteria present a particular problem when they occur in the final rinse-water of some instruments used for diagnosis. Cells of the environmental mycobacteria are easily confused, on initial detection, with pathogenic mycobacteria and may lead to misdiagnosis. Other mycobacteria that occur in water, for example Mycobacterium kansasii and M. chelonae, are opportunistic pathogens. The test is intended as a performance qualification test and periodic test. It should be carried out in a suitable microbiology laboratory.


6.85 The following equipment and materials are necessary:

• 250 mL sterile single-use containers;

• sterile filter membranes (47 mm diameter; ≤0.45 µm pore size);

• suction filtration apparatus;

• incubator at 30±2ºC;

The sample should be taken downstream of any filter or other device or equipment intended to remove or control microbial contamination in the water supply.

•Middlebrook 7H10 agar plates;

Viable counts of a test suspension on the medium of choice should not be statistically different from those obtained on a published quality control medium (Middlebrook 7H10) proven to be appropriate for environmental mycobacteria. The use of alternative media may allow for a shorter incubation time if validation data is available.

• 70% alcohol and non-woven wipes.

Method: sample collection

6.86 The sample is best collected from the EWD chamber or bowl.

Method: testing

6.87 Filter a 100 mL aliquot of the sample through a 0.45 µm filter. Aseptically transfer the filter to the surface of a Middlebrook 7H10 agar plate (or alternative media) and incubate at 30°C ± 2°C for 28 days.

6.88 Examine the cultures weekly and record the number of colony forming units that are visible.

6.89 If growth is observed, the cultures should be transferred to a laboratory with established expertise in mycobacterial identification so the strains isolated can be identified.

Results

6.90 For EWDs in which the product is rinsed after the disinfection stage, there should be no recovery of mycobacteria from 100 mL of final rinse-water.

Pseudomonas aeruginosa6.91 Pseudomonas aeruginosa is a bacterium commonly found in water but has a greater potential to cause infection, particularly in body sites that are normally sterile, than most other bacteria found in that environmental niche.

6.92 The procedure for enumeration of P. aeruginosa from EWD rinse water is based on that in the HTM 04-01 suite of documents.

6.93 A water sample should be taken and processed as for environmental mycobacteria but with the variations given in paragraphs 6.94–6.95.


6.94 The agar the filter should be transferred to is CN agar containing cetyl trimethylammonium

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6 Water system

bromide and nalidixic acid at concentrations that will inhibit the growth of bacteria other than P. aeruginosa (commercial, validated supplements for this purpose are available). Other selective and differential agars are available and acceptable if validated.

Method

6.95 The agar should be incubated at 37°C (+0/–2°C) for 2 days. Any colonies that show a blue-green pigmentation can be reported as P. aeruginosa. Should there be any doubt, colonies can be subcultured from the membrane onto milk cetrimide agar and incubated at 37°C (+0/–2°C) for 1 day. Examine the plates for growth, pigment, fluorescence and casein hydrolysis (clearing medium’s opacity around the colonies). If the pigment production is poor, expose the milk cetrimide agar to daylight at room temperature for 2–4 hours to enhance pigment production and re-examine. Other validated confirmatory testing for identification of P. aeruginosa can be used.

Results

6.96 There should be no P. aeruginosa in 100 mL of final rinse-water.

Volume of water used per stage 6.97 During type-testing, the manufacturer should be required to determine the volume of water used during each stage of the cycle. These data are used in calculations of the service requirement.

6.98 In addition, during installation or operational testing, the volume of water used for each stage should be verified. If the volume of water used is insufficient, the efficacy of the cleaning and disinfection process may be adversely affected. If the volume is greater than that specified, an unexpected heavy demand might be placed upon the water supply.


6.99 A water flowmeter (or volumetric measuring equipment) is necessary.

Method

6.100 Three methods are available for determining the volume of water used. The method chosen will depend on which is most convenient for the particular installation.

6.101 A water flowmeter may be fitted in each of the water supply pipes, consecutively or concurrently, and the flow over each period of delivery is used to calculate the total volume of water consumed during each stage of the process. The EWD should be operated with the chamber empty apart from the chamber furniture. The flowmeter manufacturer’s instructions for installation should be followed. Particular attention needs to be paid to the length of uninterrupted straight pipe required on either side of the meter.

6.102 When the EWD is supplied from a readily accessible tanked supply, the make-up to the tank may be interrupted and the water level marked. The volume of water required to restore the level after an operating cycle stage may then be determined by the addition of a measured volume of water.

6.103 For those EWDs that discharge all the water from each stage at the end of each stage, a suitable estimate of the volume used may be obtained by volumetric measurement of the discharge from the drain.

Results

6.104 The volume of water used for each stage of the cycle should be within ±5% of the volume specified by the manufacturer.

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7 Doors and door interlocks

Cycle start interlock 7.1 The interlock should prevent a cycle being started with the door or lid open.

Method 7.2 Leave the doors open and unlocked. Ensure that all services are connected. Make an attempt to initiate an operating cycle.

7.3 Close and lock the doors and make a further attempt to initiate an operating cycle.

Results 7.4 It should not be possible to initiate a cycle with the door(s) left open. With the door(s) closed it should be possible to initiate an operating cycle.

In-cycle interlock 7.5 An interlock is required to ensure that the door(s) cannot be deliberately or inadvertently opened while the EWD is in operation.

Method 7.6 Close and lock the door(s) and start the operating cycle. While the operating cycle is in progress attempt to unlock each of the doors. Where practicable, visually inspect the interlocks to verify engagement before attempting to open the door.

Results 7.7 In these circumstances it should not be possible to unlock any of the doors.

Double-ended EWDs

Method 7.8 Both during and between cycles, attempts should be made to open both the loading door and unloading door of the double-ended EWD.

Results 7.9 It should not be possible to open the unloading door after initiation of a cycle until a cycle has been completed satisfactorily.

7.10 It should not be possible for both doors to be opened at the same time.

7.11 It should not be possible to open the loading door until a cycle has been satisfactorily completed and the unloading door has been opened and closed.

On sensor failure

Method 7.12 Each sensor should be disabled in turn and an attempt made to open each of the door(s). Disabling sensors may be achieved either by disconnecting the transducer or by switching software in “engineers’ mode” to simulate a sensor fault.

Results 7.13 In each case it should not be possible to open the door(s).

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7 Doors and door interlocks

Door opening force 7.14 The mechanism for opening the EWD door should not require the use of excessive force.

Equipment 7.15 The following equipment is necessary:

a. spring balance calibrated in kilograms with a range including 0–100 kg and with an accuracy of ±1 kg over the range 0–100 kg;

b. non-extensible means of attachment of the spring balance to the door mechanism.

Method 7.16 The force required to initiate and sustain the movement of the door-opening mechanism is measured by interposing a spring balance, aligned coaxially with the direction of movement of the door-opening mechanism, between the operator and the mechanism.

7.17 Where practicable, the undertaking of checks should be avoided during an operating cycle.

7.18 Attach the spring balance to the door-opening mechanism. Open the door, note the force required to initiate the movement and to sustain the movement.

Results 7.19 The indicated value required to initiate or sustain the movement of the door-opening mechanism should not exceed 25 kg.

Failed cycle interlock 7.20 The interlock should prevent an operator from removing a load in the normal manner at the end of a failed cycle.

Method 7.21 During an operating cycle, one or more of the services to the EWD should be interrupted sufficiently to cause a cycle failure.

Results 7.22 A fault should be indicated. For double-ended EWDs it should not be possible to open the unloading door or lid; it should only be possible to open the loading door or lid by means of a special key, code or tool. Single-door or single-lid EWDs should remain locked and require the use of a special key or code for access to the chamber.

Fault indication on sensor failure 7.23 A failure of any sensor used as part of the control system of the EWD should cause a fault to be indicated by the automatic controller.

Method 7.24 Each automatic control sensor is disabled in turn to establish that a fault is indicated.

7.25 An operating cycle should be started. During or before the stage of the cycle at which the sensor is intended to provide data used to determine the control of the cycle, the sensor should be disabled.

7.26 Each sensor should be tested in both open-circuit and short-circuit failure modes.

Result 7.27 A fault should be indicated during or at the end of the cycle. It should not be possible to open the door on a single-ended EWD or the unloading door of a double-ended EWD.

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8 Chemical dosing

Reproducibility of volume admitted 8.1 The test is intended to verify the setting for the dispensed volume of chemical additive(s) and to ensure that it is reproducible within defined limits. The test should be carried out for each chemical dosing system on the EWD.

Equipment 8.2 A measuring cylinder to BS EN ISO 4788 is necessary when compatibility with the chemical additive to be measured has been established. The size of measuring cylinder should be appropriate to the volume of chemical additive to be dispensed.

8.3 Alternatively a flowmeter of appropriate range may be used.

Method a. Disconnect the supply line to the

chamber as close as possible to its discharge point into the chamber or water circulation system.

b. Actuate the dosing system and collect the discharged volume of the chemical solution in the measuring cylinder.

8.4 Repeat the test three more times. Record the volume dispensed on each test.

8.5 Take care when carrying out this test as concentrated chemical may leak. Wear gloves, full face visor and apron.

Results 8.6 Ignore the result of the first test.

8.7 The mean collected volume from the final three tests should be within ±5% of the nominal dispensed volume.

Indication of insufficient chemical additives 8.8 The use of the correct volume of chemical additive(s) is necessary for the correct functioning of the EWD. The EWD should be equipped with means to ensure that a cycle is not initiated when there is insufficient chemical additive remaining in the reservoir to complete a cycle.

8.9 The test should be carried out for each chemical dosing system on the EWD.

Method 8.10 A low level of additives is placed in the dispenser reservoir and repeated cycles are run.

8.11 Care is required since many of the concentrates used are irritant or corrosive. Water may not be an acceptable substitute because, for many dosing systems, differences in viscosity can affect the dispensed volume.

8.12 Fill an otherwise empty container with sufficient chemical for more than two, but fewer than four, operational cycles. Run the EWD on three consecutive cycles. Estimate the volume remaining at the end of each cycle (pre-marked container, dipstick, or weight).

Results 8.13 The EWD should indicate at the beginning of the third or fourth cycle that there is insufficient chemical remaining to complete a cycle and should fail to initiate a new cycle until sufficient chemical is available in the reservoir.

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9 Instrumentation fitted to an EWD

9 Instrumentation fitted to an EWD

Verification of calibration 9.1 The calibration of instrumentation, including recording systems, fitted to the EWD should be verified by comparison with calibrated test instruments during steady-state conditions, for

example the pump pressure during the wash stage.

9.2 This may be carried out concurrently with other testing, for example during the automatic control test of the quarterly periodic test (see Chapter 3, ‘Automatic control test’).

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10 Load carriers

10.1 Load carriers come in a variety of forms including cages, carriages and baskets. Their correct functioning is essential to the successful outcome of an EWD operating cycle. It is important that they cannot easily be misaligned, that they function correctly and that, when applicable, they make good connection with service supply points in the chamber and with load items (when necessary).

Method 10.2 The alignment of load carriers, their connection to water, air or chemical additive supply in the chamber (when applicable) and

their connection to endoscopes should be verified by visual observation.

10.3 Load carriers with rotary spray arms should be checked to ensure that the spray arms are free to rotate, both when the load carrier is empty and when fully loaded.

10.4 Load carriers that have lumen connections as part of their structure require special attention. The connection from the body of the EWD to the load carrier needs to be good else fluids and air may leak from the connections, invalidating system checks within the EWD.

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11 Thermometric tests


11.1 Thermometric tests are required for both thermal disinfection processes and chemical disinfection processes if elevated temperature forms part of the process cycle. If during the self-disinfect or routine cycles elevated temperatures form no part in the process, these tests do not apply.

11.2 For self-disinfection, the time/temperature of an A0 of 600 (for example, 80°C for 10 minutes) or higher is suitable (see BS EN ISO 15883-1, Annex B, for details of the A0 concept and time/temperature relationships). The disinfection temperature is measured at the coolest surface to be disinfected.

11.3 The reference test loads to be used for thermometric tests are given in paragraph 16.19, ‘Test loads’.

Chamber wall temperature for the self-disinfection cycle (if applicable)

Equipment and materials 11.4 A temperature recorder complying with the requirements specified in BS EN ISO 15883-1, clause 6.2.1, and having no fewer than 10 sensors is necessary.

Method 11.5 Thermocouples should be located one in each corner of the chamber, one in the centre of the two side walls, one in the centre of the roof of the chamber and one adjacent to the temperature sensor used as the reference sensor for chamber temperature. In addition, a probe should be positioned adjacent to the

EWD's process control sensor and a probe positioned in the centre of the chamber free space.

11.6 The temperature attained should be measured throughout three self-disinfect cycles; they should be at least 60 minutes since the machine was last used (a “cold start”).

11.7 The EWD should be operated empty except for chamber furniture (for example, load carriers).

11.8 Multi-chamber EWDs may be tested with each chamber tested consecutively or concurrently. In the latter case eight sensors will be required for each chamber.

Results 11.9 The results should be the following:

a. The temperatures recorded on the surface of the chamber should be within 0–5°C of the cleaning/disinfection temperature throughout the holding period for the cleaning/disinfection stage.

b. The temperatures recorded on the surface of the chamber should be within ±5°C of the set temperature for the relevant stage throughout the holding period for each of the other stages.

c. The temperature indicated/recorded by the EWD instruments should be within ±2°C of that recorded by the test instrument from the sensor adjacent to the reference sensor throughout the holding period for the disinfection stage.

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d. The temperature profile obtained for the operating cycle should be consistent within ±2°C for three test cycles.

Load carrier temperature during self-decontamination (if temperature used)

Equipment and materials 11.10 A temperature recorder complying with the requirements specified in BS EN ISO 15883-1, clause 6.2.1, and having no fewer than four sensors is necessary.

Method 11.11 Temperature sensors should be located at two diagonally opposite corners of the load carrier, in the approximate geometric centre of the load carrier and adjacent to the temperature sensor used as the reference sensor for chamber temperature.

11.12 The temperature attained should be measured throughout three operating cycles, which should be at least 60 minutes since the machine was last used. The EWD should be operated empty except for the endoscope carrier.

11.13 The load carrier should be replaced between cycles with a load carrier at ambient temperature.

11.14 Multi-chamber EWDs may be tested with each chamber tested consecutively using independent data-loggers to record the temperature of the load carrier. A temperature recorder with fixed sensors may be used to record the temperature adjacent to the reference sensor.

11.15 This test may be run simultaneously with the chamber wall temperature test.

Results 11.16 The results should be the following.

a. The temperatures recorded on the surface of the load carrier should be within the range 0–5°C of the disinfection temperature throughout the holding period for the disinfection stage.

b. The temperatures recorded on the surface of the load carrier should be within ±5°C of the set temperature for the relevant stage throughout the holding period for each of the other stages.

c. The temperature indicated/recorded by the EWD instruments should be within ±2°C of that recorded by the test instrument from the sensor adjacent to the reference sensor throughout the holding period for the disinfection stage.

d. The temperature profile obtained for the operating cycle should be consistent within ±2°C of the reference temperature on all test points for all three test cycles.

11.17 Three independent data-loggers and a temperature recorder having at least one sensor may be used as an alternative.

Over-temperature cut-out (when temperature is used for self-disinfection) 11.18 The EWD is fitted with an over-temperature cut-out to ensure that, in the event of the automatic control failing to control the temperature in the EWD, the temperature will not rise to a level that would damage the EWD.

11.19 This test can also be used if temperature forms part of either the wash or disinfection stage of an operating cycle. Over-temperature during these stages is likely to damage endoscopes being processed.

Equipment and materials 11.20 A temperature recorder complying with the requirements specified in BS EN 15883-1, clause 6.2.1, and having no fewer than four sensors is necessary.

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Method 11.21 Temperature sensors should be located at two diagonally opposite corners of the load carrier, in the approximate geometric centre of the load carrier and adjacent to the temperature sensor used as the reference sensor for chamber temperature.

11.22 The EWD, empty except for the load carrier, should be operated on a normal operating cycle.

11.23 During the stage of the cycle when the maximum temperature is attained, the temperature control system should be disabled.

Results 11.24 The over-temperature cut-out should operate at a temperature no more than 5ºC higher than that provided by any temperature control or temperature-limiting device.

Temperature during routine cycle 11.25 Thermometric tests are required if the EWD cycle uses temperature as part of the routine cycle, either during cleaning, rinsing or disinfection. If the EWD is not fitted with a water heater or warm water is not supplied from an external source, these tests are not required.

Equipment 11.26 Temperature sensors should comply with BS EN ISO 15883-1, clause 6.2.1. The diameter of the probes should be suitable for the internal diameter of the lumens to be tested and not reduce flow to an extent that reduces the operation of the EWD.

Method 11.27 Twelve temperature sensors are used and placed in the following positions:

•At two diagonal positions in the chamber.

•One in the geometric centre of the lid or door.

•One adjacent to each temperature control sensor.

•One adjacent to each temperature process recorder sensor.

•One attached to the endoscope control head in contact with the metal surface.

•At least one probe into a distal end lumen of the endoscope to a depth of not less than 100 mm.

•Remaining probes distributed on the outer surface on the insertion tube and umbilical cord spaced at interval of 750 mm, or less.

11.28 The probes should be positioned in good contact with the surfaces being tested. In addition probes should be positioned to monitor the slowest part of the chamber or load that has been found, by previous testing, to be the slowest to warm up.

11.29 Run the cycle used for the routine processing of flexible endoscopes. If more than one cycle is used for this purpose, and they both use elevated temperature during the process, both cycles will need to be tested.

Results 11.30 Note the maximum and minimum temperatures for each probe throughout the cycle:

a. The temperatures recorded on the surface of the chamber should be within 5°C of the cleaning/disinfection temperature throughout the holding period for the cleaning/disinfection stage.

b. The temperatures recorded on the surface of the chamber should be within ±5°C of the set temperature for the relevant stage throughout the holding period for each of the other stages.

c. The temperature indicated/recorded by the EWD instruments should be within ±2°C of that recorded by the test

26


instrument from the sensor adjacent to the reference sensor throughout the holding period for the disinfection stage.

d. The temperature profile obtained for the operating cycle should be consistent within ±2°C for three test cycles.

e. If temperature is combined with a chemical for cleaning or disinfection, the chemical manufacturer should define the minimum temperature required.

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12 Load dryness

12 Load dryness

12.1 The presence of residual water on cleaned and disinfected items may interfere with the correct functioning of the item, promote recontamination and microbial growth or prevent satisfactory subsequent disinfection.

12.2 The ability of the EWD to externally dry an endoscope may be evaluated visually, but the internal lumens and valves are hidden from view and require an additional test. If the EWD cycle claims to include a drying stage, this test should be use to determine if the EWD lumens have been adequately blown.

Method 12.3 Process the test device through a routine cycle. On completion remove the load and

connect to an air supply with a pressure of 105–120 kPa. Place the distal end of the lumen 50–100 mm above a sheet of coloured crepe paper.

12.4 Pass air down the test lumen and examine the paper for dampness denoted by dark spots on the paper.

12.5 Tests on endoscopes should be made on all lumens, with the the air supply connected from the control valve and the umbilical end.

Results 12.6 Report any water droplets that are discharged from the test device. There should be no water droplets discharge.

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13 Chemical additive residual levels

13.1 See ‘Residual chemicals’ from the ‘Operational management’ volume.

Method 13.2 The efficacy of the rinse process should be tested using the normal dose of the chemical additive on a normal operating cycle with a surrogate device to simulate an endoscope (see the ‘Performance qualification tests’ section in the ‘Validation and verification’ volume). Analysis, by the method recommended by the manufacturer, should be carried out on the final rinse-water and on the surrogate device.

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14 Air quality

14 Air quality

14.1 Many EWDs are fitted with air filters to remove particulate material from the air supplied to the drying stage. These filters are often HEPA filters (for example, EU 12/13) of the type used to remove bacterial contamination from the air supply. When they are used as general particulate filters, performance tests will not normally be required for the filter or the filter housing. If a filter is fitted to provide air free from bacterial contamination for flushing an endoscope without further processing, a certificate of conformity should be available.

14.2 Microbial sampling will not normally be required for either system unless otherwise specified.

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15 Sound pressure test

15.1 This test measures the total sound power radiated from the machine and should be performed in a specially designed and equipped test room. It is neither necessary nor practicable to repeat the test on an installed machine.

15.2 The perceived level of noise in the immediate vicinity of the equipment during operation is, however, of concern. The perceived noise level depends not only upon the sound power level of the equipment but also on the acoustic properties of the environment and other sources of noise. It should necessarily be determined with the EWD installed and working normally.

15.3 A failure of the sound pressure test need not be an indication that the machine is faulty. The problem might lie in the acoustic properties of the room in which the machine is installed.

15.4 The sound pressure test should be carried out in accordance with BS EN ISO 3746 by suitably trained and experienced personnel. The guidelines given in the following two paragraphs are intended only for additional guidance and are not the complete test method.

Method 15.5 Use the procedure specified in BS EN ISO 3746 for both the loading and unloading area if these are not common (and plantroom if present), to determine the following:

a. the mean A-weighted surface sound pressure level;

b. the peak A-weighted surface sound pressure level.

Results 15.6 The test should be considered satisfactory if the following recommendations are followed:

a. the mean A-weighted surface sound pressure level does not exceed:

(i) 55 dBA for an EWD installed in an operating suite, ward, treatment room or other noise sensitive area;

(ii) 70 dBA for and EWD installed in an endoscopy reprocessing unit;

b. in both the loading and unloading area the peak A-weighted surface sound pressure does not exceed the mean A-weighted surface sound pressure level by more than 15 dBA.

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16 Cleaning efficacy tests

16 Cleaning efficacy tests

Test soils/process challenge devices16.1 These tests are used to demonstrate the ability of the EWD to remove soil and contamination from the chamber, carriage and channels to ensure the EWD is working to a defined level of cleaning efficacy. Test soils are used to simulate naturally occurring contamination since the latter shows considerable variation and is therefore more difficult to use for standardised testing.

16.2 Process challenge devices containing cleaning efficacy indicators are used to verify that cleaning has been achieved. There are many devices available for use. It is important that manufacturers’ instructions are followed correctly to ensure the EWD is working to a defined level of cleaning efficacy. They can also be used as an independent audit tool to compare performance of processes. See also paragraphs 4.20–4.21 in HTM 01-06 Part D – 'Validation and verification'.

Note

Commercial process challenge devices are being developed whose challenge simulates the attachment of prion protein to endoscopes and whose analysis is quantitative. When these become available and have been validated, reprocessing units are advised to consider their use in addition to process challenge devices based on soils in BS EN ISO 15883-5 Annex R.

Type tests

Using the test soil given in paragraph 16.5, this test can be used as an optional test to determine the water distribution and cleaning efficiency of the chamber and load carriers to ensure a good water distribution.

16.3 Cleaning efficacy should be determined using the relevant test soil listed in ISO/TS 15883-5. This soil is used to test instruments after an EWD cycle.

16.4 The relevant test soil in ISO/TS 15883-5 or validated equivalent is applied to a reference load or surrogate device of demonstrated relevance (see BS EN ISO 15883-4 Annex F or as specified in the relevant part of BS EN ISO 15883-4).

16.5 The test soil can be made from:

•water, 50 mL;

• glycerol, 30 mL;

• horse serum, 30 mL;

•dehydrated hog mucin, 5 g;

• unbleached plain flour, 2 g;

• aqueous safranine solution, 2 % mass fraction, 1 mL.

Preparation and storage 16.6 Mix all the constituents together and agitate in a stomacher to give a liquid of uniform consistency. Use immediately or store in an airtight container at 2–5ºC for not more than

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one month or follow the manufacturer's recommendations.

Application and use 16.7 If the soil has been stored, allow it to equilibrate to room temperature before use.

16.8 The test should be carried out using water of a quality suitable for the system requirements using a detergent recommended by the EWD manufacturer. The EWD manufacturer should provide guidance on the minimum water quality suitable for the detergent recommended. All tests should be run in triplicate and for each series of tests each of the three tests should meet or exceed the minimum acceptance criteria.

Method of application 16.9 Apply soil to the inner surface of the test pieces by injecting the soil into the tubes of the surrogate device (approximately 5 mL into the 1 mm inner-diameter tube and 20 mL into each of the 2 mm inner-diameter tubes). Lay the tubes on a horizontal surface and roll them to distribute the soil over the inner surface.

16.10 Hold them vertically to allow excess soil to drain away. Apply a small amount of air to each soiled tube from a syringe full of air to blow out any residual soil. Then apply an even coat of soil to the outer surface using the paintbrush. Allow excess soil to drain from the items and allow them to dry at room temperature (15–25°C) for not less than 30 minutes and not more than two hours. To dry the inner surface of the tubes, connect each tube to a small air pump and pass air down the tubes for the drying time.

Method of use 16.11 Connect each surrogate tube to the EWD outlets with suitable connectors: one of the 2 mm inner-diameter tubes connected to the biopsy lumen; and one of the 1 mm inner-diameter tubes connected to the bridge lumen, if used. Run a routine EWD cycle. After completion of the wash cycle, the cycle should

be aborted, if possible. The test load should be removed and examined for the presence of residual soil. This test should be run in duplicate.

16.12 The manufacturer should establish worst-case conditions of temperature, detergent concentration, surrogate device configuration, based on illustrations in BS EN ISO 15883-4 Annex F, and water pressure/flow rate for use during testing.

16.13 By analysing the fraction of soil removed during the cleaning process when operated for various time periods shorter than those that will normally be used, a quantitative comparison of cleaning efficacy can be made.

16.14 The recommended minimum operating conditions given by the manufacturer should be based on these data, which should be made available to the User as part of the type-test data sheets.

Operational tests 16.15 During operational tests of cleaning efficacy with test soils, the disinfection stage and drying stage should be disabled, unless it can be demonstrated that inclusion make little difference to the results.

Test soils 16.16 The choice of test soil to be used should be that specified in the type tests or that described in paragraph 16.2, which represents a more realistic tissue residue.

16.17 Drying the deposited test soil is important, as it has an influence on the difficulty of cleaning. At least two hours plus or minus 15 minutes’ drying time is required, including lumens. The soil should be spread on such that it appears dry within the specified drying time. After soiling lumen may be dried, by passing down low pressure dry air for the required time.

16.18 These performance criteria include the following:

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17 Leak and patency testing

a. The test soil formulation should be validated as being of equal or greater difficulty to remove than the naturally occurring soils, which it is intended to simulate.

b. The method of application to give a level of soiling which is reproducible within specified limits should be validated and documented.

c. The method of detection of residual soil should be quantitative; visual assessment alone should not be regarded as satisfactory.

d. The limit of sensitivity of the detection method employed should be 30 µg of protein or below per test swab.

e. For tests on the chamber walls and load carrier and lumen, the detection method should include a validated method for quantitative detection of the residual soil in situ or a validated method of removal for example, by swabbing, for subsequent evaluation.

Test loads 16.19 The test load should consist of items of similar size, mass and materials of construction to the range of EWD it is intended to process.

16.20 A surrogate device for investigation of cleaning and disinfection may be constructed from two 1.5 m lengths of polytetrafluorethylene (PTFE) tube (2 mm inner diameter) and one 1.5 m length of PTFE tube (1 mm inner diameter). These should be bound together at intervals of approximately 15 cm. For EWDs with more than three lumens, two sets of three surrogate devices may be required so that each of the machine’s lumens can be tested. Advice from the EWD manufacture may be required to select suitable test tube diameters.

16.21 As flexible endoscopes with irrigation lumens include valve systems to control air and fluids, these need to be simulated in a test device. Examples of such devices are illustrated in BS EN ISO 15883-4 Annex F. At present

there are no standard designs for these test pieces, but a design that simulates the internal structure of a flexible endoscope would be acceptable.

Procedure for chamber walls and load carriers

16.22 The chamber walls and load carrier should be contaminated with the test soil in accordance with the instructions for the test soil.

16.23 The load surfaces are dried in air for 30–120 minutes, including lumens.

16.24 A normal operating cycle should be run.

16.25 After completion of the wash cycle and before the disinfection stage, the cycle should be aborted. The chamber walls and load carrier should be examined for the presence of residual soil by the method prescribed for the particular test soil.

16.26 It is important that the specified quantities are used.

16.27 The test should be carried out in duplicate for each type of operating cycle available on the EWD.

Procedure for reference loads

16.28 This test should be run only after satisfactory completion of the test for the efficacy of soil removal from chamber walls and load carriers. The test load should be contaminated with the test soil in accordance with the instructions for the test soil.

16.29 A normal operating cycle for the load type under test should be run.

16.30 After completion of the wash cycle and before the disinfection stage, the cycle should be aborted. The test load, lumen, chamber walls and load carrier should be examined for the presence of residual soil.

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Results

16.31 The chamber walls and load carrier should be free from the test soil to the extent specified for the test soil employed.

16.32 The test load should be free from the test soil and none should have been transferred to the chamber walls or load carrier.

Periodic tests: residual protein detection 16.33 These tests should be carried out quarterly per EWD.

16.34 Test methods previously recommended for detection of residual proteins have limited ability to remove protein from surfaces, and assays have been shown to be insensitive. Alternative available technologies should be considered for the detection of residual proteins on the internal surfaces of flexible endoscopes following reprocessing. Therefore reprocessing units should:

a. consider the available technologies and make a risk-based decision on the methodology to be adopted (for example BS EN ISO 14971);

b. use technologies with the best available sensitivity, consistent measurement standards and quantifiable results to measure effective control of residual protein levels;

c. use trend analysis as a tool for self-improvement to demonstrate decreasing protein levels over time both on the outside of the endoscope and the lumens using available testing technologies.

Note

This remains a work in progress which will be updated as additional evidence becomes available.

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Leak test 17.1 The leak test is carried out to determine if liquid can gain access to the inner cavity of an endoscope, thereby causing extensive damage. The leak test is carried out manually before the endoscope is cleaned and again by the EWD, either at the start of the process cycle or throughout the cycle. It is important that the air used to pressurise an endoscope does not exceed the limit set by the endoscope manufacturer, normally about 250 mbar.

17.2 The test described is based on the use of a test device. This device needs to represent the inner volume of the largest endoscopes in use.

Equipment 17.3 This consists of:

• Length of flexible tube approximately 1m terminated at one end to fit onto the EWD leak test connection and at the other end terminated with a flow valve.

• To construct a test device, the internal volume of the largest endoscope in use is needed; this may be obtained from the manufacturer. The internal volume of the tube is calculated and additional volume, to make up the volume equal to that of an endoscope, can be supplied by an additional pressure tight container as illustrated in Figure 1.

•A convenient way of adding additional volume to a tube is to cut the tube in half and fit a suitable T-piece. To the T-piece side arm connect a plastic bottle that is

Connector to EWDleak test port

Pressure transducer

Flow control

Volume of container plus tube – CV = internal volume of endoscope – TV

CV

Endoscope internal volume – TV

Container and tube internal volume – CV

Figure 1 Leak test surrogate device

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approximately the correct internal volume required. A bottle of internal volume 100–200 mL may be suitable.

•Pressure transducer able to read ±1 mbar (±0.1 kPa) over the range of the EWD operating pressure.

Procedure 17.4 Verify the calibration of the pressure sensor.

17.5 Connect the test piece (see Figure 1) to the EWD leak outlet port with the flow control valve fully closed. Disable the pressure regulation system on the EWD. Start a leak test. Record the pressure at which the pressure relief system operates Pmax. Continue the cycle to obtain a steady reading on the transducer Pb. Check that the readings of Pmax and Pb do not exceed the manufacturer’s recommendations.

17.6 Fault condition – connect the test device to the EWD and run a leak test. Adjust the flow control valve to give a pressure greater than that specified by the manufacturer (P1). The flow valve is opened slowly and the pressure transducer reading observed. The aim is to increase the leak so the pressure within the test device falls below P3 before time T3 is reached, i.e. a leak is present. Confirm from the readings

that an EWD fail condition has occurred and a fault has been indicated.

17.7 Pass condition – adjust the flow control valve to give a leak rate 80% less than the fail value given by the manufacturer. Connect the test device to the EWD and run a leak test. The time for the test device pressure to fall to value P3 should be greater than time T3, that is, low or no leak. From the readings confirm that a pass condition has occurred on the EWD and no fault has been indicated.

17.8 The leak test characteristics are illustrated by Figure 2, where:

•Pmax the pressure relief system should operate below this pressure;

•P1 the leak test pressure;

•T1 the start of the leak test equilibrium period;

•P2 pressure after initial equilibrium time;

•P3 pressure determined by EWD manufacturer; the level of maximum allowable leak within the leak monitoring time;

•T2 start of leak test monitoring time;

•T3 end of leak test monitoring time; ∆

Atmospheric pressure

Time

Pressure

Pmax

P1

P2

P3

T0 T1 T2 T3

Figure 2 Pressure/time graph for leak test

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•∆P/T maximum leakage rate permitted for the process to continue, i.e. just a pass.

NoteAt the start of the test the pressure should be approximately 200 mbar (120 kPa) above atmospheric pressure, unless otherwise stated by the manufacturer. The leak test monitoring period should not be less than 1 minute. The maximum leak rate should be no greater than 2.5 mbar/min (0.25 kPa/min).

Lumen patency detection test 17.9 EWDs for endoscopes should be fitted with means to ensure that each of the lumens is patent so that disinfectant and rinse solutions will flow through each lumen, even those that have a control wire. In addition a test is required to demonstrate if an endoscope lumen becomes disconnected it will be detected.

Equipment 17.10 A surrogate device should be used to demonstrate that the system for determining the patency of each lumen is function correctly. The surrogate device may be constructed by

using a 1.5 m length of PTFE tubing (1 mm inner diameter).

Method 17.11 For each lumen (air/water, biopsy, elevator as relevant), connect a 1.5 m length of tubing of the appropriate diameter and run an operating cycle. On completion of the cycle replace one of the tubes with a similar tube that has a Luer-lock male connection. A hypodermic needle of the appropriate size, with sheath attached and the end cut off for safety reasons, is attached to the 1 mm inner-diameter tube. Other small lumen test pieces may be used, attached to the 1.5 m tube, as long as they present a partial blockage to fluid flow. Another operating cycle should then be run. Repeat the test, changing the position of the partially obstructed tube on each test.

NoteEach make of EWD and each lumen may require a different size needle to obtain a partial obstruction indication. Some EWDs may have a very sensitive lumen blocking system. In addition the pressure of fluid down each lumen may be different; this will affect the partial blockage detection system. Some EWDs use air to detect blockage with different sizes of needles from those that use fluid flow for operation.

17.12 Needles from size 21 to 32 will be required to determine at commissioning which size is suitable for each lumen to give an indication of partial blockage. Figure 3 gives an illustration of a suitable test piece.

Sheath with end cut off glued to needleneedle

1 mm interior diameter tube

Figure 3 Test piece for the partial blockage test

(P2 –P3)(T3 –T2)

P /T

or(P1 –P3)(T3 –T1)

P /T

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Results17.13 The EWD should indicate a fault for any lumen to which the appropriate partially obstructed surrogate device is fitted.

Lumen disconnection detection test 17.14 To demonstrate if an EWD can detect disconnected lumens, fit a surrogate device to each lumen of the EWD and confirm that the EWD can run a routine cycle.

Method 17.15 Disconnect each lumen in turn and run a process cycle. If the EWD can detect several lumen disconnections in one cycle and record the event, more than one lumen disconnection can be tested for each process cycle.

Results 17.16 A satisfactory result is when the EWD fails due to lumen disconnections and can indicate which lumens are affected.

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18 EWD self-disinfection test


18.1 This test is a type test to verify that the EWD’s “machine disinfection” mode will disinfect those parts of the EWD that come into contact with fluids that are intended to, or may, contact the load. The type test will be carried out by the manufacturer on the chemicals selected as suitable for the EWD cycle. If a chemical is chosen that is not listed on the type-test list, the following test scheme will be required. It is not recommended that live organisms are used as test material on EWDs, as there is a risk to patient safety.

18.2 The process is intended to deal with the situation where an EWD has become contaminated and is routinely carried out at the start of each working day. The piping used to convey rinse-water to the endoscope, if contaminated, may easily develop a layer of biofilm containing many microorganisms in a state, which is highly resistant to chemical disinfection. This tubing should normally be replaced at the interval specified by the manufacturer.

18.3 Biofilm may also develop in EWD tubes during storage after production and testing before the machine is installed. The change of pipework before commissioning may well save time trying to clean existing tubes.

Thermal disinfection 18.4 Thermal disinfection systems should be evaluated by thermometric monitoring of the system with sensors placed at the parts of the system most remote from the heat source. The entire system should attain the required disinfection time/temperature of values that

have been validated against a test biofilm in a similar manner to chemical disinfection (see below).

Chemical disinfection 18.5 For chemical disinfection systems a microbiological test will be required. The test is designed to ensure that the self-disinfection cycle will disinfect contaminated tubing by evaluating the effect of the cycle against a biofilm containing Pseudomonas aeruginosa.

Production of biofilm test pieces

Equipment and materials 18.6 The following equipment and materials are necessary:

a. peristaltic pump;

b. The EWD may be equipped with auto- or manually-selected self-disinfect mode. The method may be thermal or chemical and in the latter case may be the same or a different germicide from that used for chemical disinfection of the load. The preferred method is thermal disinfection or, if this is not possible, the use of a different germicide. The use of the same germicide carries the risk of allowing organisms resistant to that particular germicide to proliferate.

c. incubator at 30ºC ± 2ºC;

d. 1 L sterile conical flask fitted with rubber bung, air vent and two sterile glass tubes;

40


e. sterile connecting tubing;

f. 1.5 m length of sterile 6 mm inner-diameter PTFE tubing;

g. nutrient agar supplemented with 1 g/L sodium desoxycholate;

h. 0.025 g/L of 2.4.4’-trichloro-2’-hydroxydiphenylether;

i. Pseudomonas aeruginosa (ATCC number 15442);

j. liquid growth medium: phosphate buffer (containing 1.2 g/L sodium phosphate, dibasic; and 0.5 g/L potassium phosphate, monobasic);

k. containing 0.25 g/L sodium glutamate and 0.1 g/L citric acid.

Method 18.7 A petri dish containing supplemented nutrient agar should be inoculated with Pseudomonas aeruginosa(ATCC number 15442) and incubated at 30ºC ± 2ºC for 36–48 hours.

18.8 A 1 L conical flask containing 500 mL of the sterile liquid growth medium is inoculated with mucoid colonies of Pseudomonas aeruginosafrom the agar plate and incubated at 30ºC ± 2ºC for 18–24 hours. The flask is then fitted with a bung through which passes an air vent, filtered to 0.22 m, and two glass tubes, one of which reaches to the bottom of the flask and the other terminating above the level of liquid in the flask.

18.9 The sterile glass tubes are connected, via a peristaltic pump and short lengths of sterile flexible tubing, to 1.5–2.0 m sterile PTFE tubing (6 mm inner diameter). The culture is pumped round the tubing system at 50–75 mL/min throughout the incubation period. The system is maintained in an incubator at 30ºC ± 2ºC for 72– 96 hours.

Evaluation of the self-disinfection cycle 18.10 This test forms part of the type-test scheme. The disinfectants tested by this method will be detailed in the EWD manufacturer’s data. Therefore select a chemical from the manufacturer’s list; otherwise, the following test will need to be carried out.

18.11 A 30 cm section of the tubing, suitably identified (for example, T1), prepared with biofilm is subjected to the test procedure described below:

a. A section of the piping in the endoscope lumen irrigation system of the EWD is removed and replaced with the test system. The test system consists of two 30 cm lengths of the biofilm test piece tubing connected via isolating valves and Y-piece connectors in place of the removed section of pipework.

b. It may be more convenient to connect the test tubes, with isolating valves to the biopsy lumen irrigation outlet on the EWD. It should be confirmed that disinfectant flows down this lumen during self-decontamination.

c. With the valves open, the EWD is set to operate a self-disinfect cycle. During the test the EWD door or lid should be open; this may require the EWD to operate in “engineers’ mode” and require the assistance of the manufacturer.

d. At the end of any wash stage, and immediately before the start of the chemical disinfection stage, close the valves isolating one of the test pieces (T2). On completion of the disinfection stage and any subsequent rinse stage, remove both test pieces (T2 and T3) and carry out the recovery procedure described below.

e. Replace the test pieces with two more sections of the tubing with biofilm and

41


carry out a further self-disinfect cycle. Isolate one of the test pieces (T4) at the end of the disinfection stage and before any rinsing process. On completion of the cycle, remove both test pieces (T4 and T5) and carry out the recovery procedure described below.

Recovery procedure 18.12 The 30 cm length of tube should be cut into six portions, each approximately 5 cm in length. Three of these should be transferred into individual universal containers containing nutrient broth and incubated at 30ºC ± 2ºC.

18.13 The remaining three sections should be cut in half longitudinally, and each pair transferred to 10 mL of quarter-strength Ringer’s solution containing 0.05% polysorbate 80 in a thin-walled universal container.

18.14 The container should be ultrasonicated for 10 minutes at between 30 and 50 kHz. Tenfold serial dilutions should be prepared of the eluate obtained, and these should be used for enumeration of the surviving organisms by the spread plate technique or other appropriate viable counting method. All determinations should be carried out in duplicate.

Results 18.15 The data obtained give the following information:

• T1 – recoverable population on the original test piece;

• T2 – recoverable population after the washing stage;

• T3 – recoverable population after wash, disinfect and rinse stages;

• T4 – recoverable population after wash and disinfect stages;

• T5 – recoverable population after wash, disinfect and rinse stages;

• T3 and T5 should have the same population within the limits of

experimental error; the difference between them is a measure of the reproducibility of the system;

• T1 – T2 is the loss during the washing stage;

• T3 – T4 and T5 – T4 are the losses during the post-disinfection rinse;

• T2 – T4 is the loss due to the disinfection process.

18.16 On testing the full self-disinfect cycle, there should be no recovery of organisms from T3, T4 and T5. When this is the case, the test should be repeated with the exposure time reduced to half the normal disinfection time. This will require the manufacturer’s assistance, and the EWD will need to be operated in “engineers’ mode”. The reduced exposure time should give a reduction of at least 103 in the number of recoverable microorganisms (T2 – T4 ≥ 103).

18.17 An alternative method is described in BS EN ISO 15883-4, clause 6.12.3.1.

18.18 For the purposes of periodic testing, a water sample taken from the bowl/chamber after self-decontamination examined for the presence of bacteria should be sufficient to determine whether the process has killed or removed organisms from the pipe circuit.

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19 Disinfectant concentration test

19.1 EWDs employing a chemical disinfection stage may reuse the chemical disinfectant a number of times (multi-use). Guidance on the number of cycles for which a particular disinfectant can be used is provided by the chemical manufacturer. Owing to the variable nature of the load, it is difficult to determine exactly how many cycles the disinfectant will remain active for. If a cycle counter is used to indicate the exhaustion of the disinfectant, the number of cycles should be set at a lower number than recommended to allow for endoscope variation and dilution of the chemical by residual water.

19.2 When the disinfectant is used only once and discarded, a disinfectant concentration test is not required.

19.3 When such a system is employed, the EWD should be equipped with means to establish that the concentration of the active ingredient(s) in the disinfectant is above the concentration specified as the minimum acceptable. (This may be in the form of a test kit.)

19.4 The disinfectant concentration test is carried out to establish that the means provided is effective.

19.5 The full strength solution, unused (and if necessary freshly prepared or activated), should be prepared according to the manufacturer’s

instructions. When this requires the addition of water, only distilled or purified water should be used.

19.6 A dilution series should be prepared using distilled or purified water.

19.7 If the concentration of fresh disinfectant is C1 and the minimum concentration of usable disinfectant is C2,the following dilutions should be prepared:

a. C2 + [(C1 – C2)/10]

b. C2

c. C2 – [(C1 – C2)/10]

19.8 For EWDs with an automated disinfectant detection system, the test is carried out by transferring dilute disinfectant to the disinfectant reservoir and attempting to start an operating cycle. The EWD should indicate when the concentration is insufficient.

19.9 For EWDs where there is no in-built disinfection concentration measurement, the User has responsibility for taking a sample from the EWD’s diluted disinfectant tank. This test should be undertaken outside the EWD.

19.10 The automated system or the User test should indicate an unsuitable disinfectant concentration for dilution (c) and a satisfactory disinfectant concentration for dilution (a).

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20 Microbiological and temperature tests of disinfection efficacy

20 Microbiological and temperature tests of disinfection efficacy

20.1 Disinfection efficacy should be verified during type testing using the test described in BS EN ISO 15883-4, clause 6.12.6.2. The test should not be carried out until the adequacy of the EWD self-disinfection cycle has been established.

20.2 If temperature forms part of the disinfection process, the thermometric test for assessment of temperature control throughout the disinfection stage should be completed satisfactorily before commencing microbiological tests as described in BS EN ISO 15883-4, clause 6.9.

Disinfection efficacy 20.3 Disinfection efficacy should have been tested during type-testing with a surrogate device (BS EN ISO 15883-4, clause 6.12.6). When necessary the adequacy of the disinfection process may be verified by using the method given below, which is included to provide additional information should disinfection problems occur.

Endoscope lumen sampling 20.4 The endoscope should be brushed through with a sterile disposable long-stemmed cleaning brush after processing. The brush end should be aseptically cut from the stem and aseptically transferred to 10 mL of sterile peptone water containing 0.05% polysorbate 80 and ultrasonicated at between 30 and 50 kHz for 10 minutes. The eluate should then be filtered through a 47 mm diameter 0.45 m filter

and then the filter placed onto a R2A agar plate and incubated at 30±2°C for up to five days. The number of colony forming units (cfu) counted will give an indication of the adequacy of the disinfection process.

20.5 A result of less than 10 cfu per brush sample should be obtained if the endoscope has been satisfactorily disinfected

20.6 This is the preferred method of lumen sampling. An additional less satisfactory test that may be useful to measure the microbiological performance of the EWD cycle, manual cleaning and possibly the drying cabinets is to examine an endoscope after it has been used, decontaminated and dried. The test involves passing liquid down the endoscope lumens, collecting the effluent and subjecting it to bacteriological counting.

20.7 The following apparatus is necessary:

• sterile water;

• sterile 10 mL syringe;

• sterile collection bottles;

• lengths of sterile tube to connect the syringe to each endoscope port in turn;

• sterile gloves.

20.8 A suitable procedure is the following (use of sterile gloves and aseptic techniques are essential to obtain good results):

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Biopsy lumen:

a. Attach a length of sterile tube of suitable diameter to a syringe and the other end to the biopsy lumen port.

b. Flush 10 mL of water down the lumen and collect into a sterile sample bottle at the distal end.

Suction lumen:

a. Attach a length of sterile tube of suitable diameter to a syringe and the other end to the suction port on the light guide connector.

b. Depress the biopsy/suction feed button (red trumpet valve on the control box) and flush 10 mL of water the entire length of the suction lumen.

c. Collect the liquid expressed from the distal end of the endoscope into a sterile sample bottle.

Air lumen

a. Attach a length of sterile tube of suitable diameter to a syringe and the other end to the air inlet port on the light guide connector.

b. Cover the water port (blue trumpet valve on the control box) and the water lumen on the light guide connector with a finger

while flushing the water along the air lumen.


Water lumen

a. Attach a length of sterile tube of suitable diameter to a syringe and the other end to the water inlet on the light guide connector.

b. Depress the air/water trumpet valve (blue) on the control box and cover the air lumen on the light guide connector with a finger while flushing the water along the water lumen.


20.9 In a microbiology laboratory, examine the chilled samples collected within four hours of collection if stored at room temperature, or within 24 hours if stored at 2– 5°C. Carry out a total bacterial count/mL on each sample using R2A (BS EN ISO 15883-1 Annex D), TSA or YEA media and incubation at 30±2°C for up to five days.

20.10 The results should be below 10 cfu/100 mL as detailed in Table 1 of Chapter 6, ‘Water system’.

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References

References

BS EN ISO 15883-4.

COSHH Regulations.

Health Technical Memorandum 04-01 Part A.

Health Technical Memorandum 04-01 Part B.

Willis, C. (2006). “Bacteria-free endoscopy rinse water – a realistic aim?” Epidemiology and Infection. Vol. 134 No. 2, pp. 279–284.

BS EN ISO 15883-1.

BS EN ISO 4788.

BS EN ISO 3746.

ISO/TS 15883-5.

http://shop.bsigroup.com/en/ProductDetail/?pid=000000000030197956

http://www.legislation.gov.uk/uksi/2002/2677/pdfs/uksi_20022677_en.pdf

http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=408481&fulltextType=RA&fileId=S0950268805005066



http://shop.bsigroup.com/ProductDetail/?pid=000000000030197944



http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=41175

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