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Decontamination of flexible endoscopes
Decontamination of flexible endoscopes
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P. Hoffman Consultant Clinical Scientist, HCAI & AMR, Public Health England, London, United Kingdom
22.1 Types of endoscopes Endoscopes are tubular medical devices, parts of which enter the body to visualize internal structures for diagnostic purposes and, facilitated by this visualization, to take biopsies or carry out procedures. Structurally, endoscopes can be divided into rigid and flexible endoscopes. Rigid endoscopes are made of metal, are heat tolerant and can be cleaned in conventional surgical instrument washer-disinfectors and steam sterilized. For this reason, rigid endoscopes are classed as reprocessable surgical instruments which are dealt with in other chapters in this book. In contrast, flexible endoscopes are manufactured using thermolabile materials that cannot withstand surgical instrument washer-disinfectors or steam sterilization and present a specific set of challenges to effective decontamination. All endoscopes are centered around two core functions: (1) To illuminate internal body structures, light generated by a source outside the body is transmitted to the distal point inside the patient through a bundle of glass fibers. (2) To carry an image back out of the patient. Newer endoscopes use a photochip; older endoscopes use a glass fiber bundle with precisely the same alignment of fibers at both ends to carry the image, each light element being transmitted by an individual fiber.
22.2 Structure of endoscopes Flexible endoscopes range from those used for visualization only, e.g., nasendoscopes, to more complex devices that contain numerous channels, e.g., endoscopes used for endoscopic retrograde cholangiopancreatography (ERCP) and colonoscopy where biopsies may need to be taken. It is important that staff carrying out the decontamination procedure understand the structure of all endoscopes they are processing to ensure that all channels are accessed during decontamination. The channels in a typical endoscope occupy the entire length of the endoscope and can be as long as 2.5 m with internal diameters ranging from approximately 1 to 4 mm. The majority of flexible endoscopes have several internal lumens; one or more to pass biopsy instruments and therapeutic accessories (biopsy channel), joined at a Y junction to another lumen to remove fluid matter from obscuring the area being observed Decontamination in Hospitals and Healthcare. https://doi.org/10.1016/B978-0-08-102565-9.00022-4 © 2020 Elsevier Ltd. All rights reserved.
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(suction channel); other lumens are used to pass water to clean the visualizing lens (water channel) and to pass air to insufflate body cavities to facilitate viewing (air channel). Additional lumens for other functions may exist in more specialist endoscopes. Internal lumens can be complex and long, making their decontamination the most challenging aspect of endoscope reprocessing.
22.3 Risk assessment The standard approach to decontamination risk assessments is the approach illustrated in Table 22.1. However, for flexible endoscope decontamination this standard approach is problematic and more specific risk assessments are often required depending on the risk. Procedure types, in increasing order of risk, are given below: (a) As a minimum, endoscopes make contact with intact mucous membranes. It is impossible to guarantee that those mucous membranes will be intact. It seems reasonable to assume that, when investigating pathological conditions, there is a higher than normal chance of those mucous membranes being damaged. (b) The next stage up from this, in terms of risk, is when biopsies are taken, or surgical procedures carried out in contaminated body cavities. Here mucous membranes are intentionally breached, with the biopsy equipment used first passing through an endoscope lumen. (c) The risk scale progresses when endoscopes are used to enter body cavities that are normally sterile, such as the bladder, progressively increasing when surfaces are not intact or are entered for biopsies or procedures. (d) The highest risk category is when endoscopes are used surgically, and are in contact with normally sterile body tissues (as opposed to sterile body cavities).
For procedures in categories a, b, and c, it is important to realize that the endoscopes will either be used in an area that is naturally contaminated (e.g., colonoscopes) or will first pass through an area that is contaminated before they reach the normally sterile site (e.g., cystoscopes). In such cases, it seems unproductive to require those endoscopes to be sterile before use as they will inevitably be contaminated when they reach their point of use. With these endoscopes, the prevention of infection transmission is achieved by ensuring that pathogens acquired in the procedure on the previous Table 22.1 Risks from medical instruments, equipment, and environment. Instruments that come into contact with
Risk level
Decontamination required
Normally sterile body tissues Intact mucous membrane
High Medium
Intact skin
Low
Surfaces not normally in contact with intact skin
Minimal
Sterilize Sterilize, heat disinfect, chemical disinfect only if thermolabile Disinfect or clean (depending on patient susceptibility) Clean; disinfect only in special circumstances
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patient are eliminated and by preventing significant recontamination. Prevention of significant recontamination can be divided into three areas: (1) Prevention of contamination via the rinse water used to remove disinfectant from the endoscope, (2) prevention of replication of residual contamination within the endoscope on storage, and (3) prevention of recontamination, directly or indirectly, with contamination from other endoscopes before they are decontaminated and similarly with any patient blood or body fluid. For endoscopes used in category d (highest risk), processing in an endoscope washer-disinfector, followed by complete drying, followed by a quality assured, compatible low temperature sterilization is the preferred option. Clinical risk assessments should take account of: ●
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The risk of the procedure (see above) The susceptibility of individual patients The nature and extent of residual contamination likely to be present on an endoscope
An example of a risk assessment relating to contamination of rinse water is in Section 22.7 later in this chapter. The risk assessment should also be applied to the conditions and duration of storage of endoscopes between decontamination and reuse. Here the hazard is of the regrowth of bacteria in incompletely dried endoscope lumens leading to patient infection or misdiagnosis (e.g., mycobacteria in diagnostic samples from bronchoscopies). More details are given in Section 22.16 later. The endoscope-mediated transmission of disease associated with transmissible spongiform encephalopathies (TSEs), primarily Creutzfeldt-Jakob disease (CJD) and variant Creutzfeldt-Jakob disease (vCJD), should also form part of a risk assessment. In the United Kingdom, detailed guidance on this is given by the Advisory Committee on Dangerous Pathogens (ACDP) TSE Risk Management Subgroup [1] in Annex F of their guidance. This is updated as required and should be referred to for any detailed risk assessment; only general principles are given in this chapter. The agents of TSEs (prions) are exceptionally resistant to heat and chemical inactivation and are also thought to adhere strongly to surfaces, particularly if allowed to dry, and thus to resist removal by cleaning. Ascertainment of risk [1] comprises assessment of individuals in respect of their likely carriage of prion disease combined with the tissues the endoscope will make contact with for their potential level of prion contamination. Patients are categorized into either definite/probable prion carriage, possible or asymptomatic but at risk, or patients at no known risk. Body tissues are classified as high risk (brain and spinal cord), medium risk (olfactory epithelium for CJD or olfactory epithelium and lymphoid tissue for vCJD), or low risk for other tissues. For patients at definite/probable, possible or at risk of prion carriage, if the endoscope is in contact with high risk or medium tissues, it should be kept for reuse solely on that patient or destroyed after use (or quarantined pending final diagnosis, during which time it can be reused on the same patient). In these patients, if the endoscope is in contact with low-risk tissues, no special precautions are needed. For patients not known to be at increased prion risk, for endoscopes to be used in contact with all tissues, no additional precautions are needed.
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22.4 Flexible endoscope decontamination 22.4.1 Risk of infection The risk of infection following flexible endoscopy is considered to be low in relation to the number of procedures carried out [2], but the true infection rate remains unclear as many of the patients are examined as day cases so are not followed up. Nelson [3] and Kovaleva et al. [4] have reviewed infections attributed to endoscopes, which include: Salmonella species including S. typhi, Pseudomonas aeruginosa, Helicobacter pylori, Mycobacterium tuberculosis and other Mycobacteria, hepatitis B and C viruses, Strongyloides stercoralis, and Trichosporon species.
22.4.2 Problems Flexible endoscopes are heat sensitive, have a complex structure, and are made of various materials. The channel configuration varies depending on the type of endoscopes. Some are used for visualization only and will have few or no channels; others are for therapeutic/diagnostic procedures and will have several channels. This variation can cause problems for decontamination staff if they are unfamiliar with the structure of the endoscopes they are dealing with as it is important to access all channels during the decontamination procedure. The high cost of flexible endoscopes often means there are usually a minimal number of endoscopes available and that, coupled with the rapid throughput of patients, can put time pressures on the decontamination procedure. Ofstead et al. [5] carried out a prospective study on endoscope reprocessing which showed that a lack of time was a factor in the deviation from standard procedures. An assurance of the decontamination process is essential, and all stages should be recorded. The selection of a disinfectant requires a balance between efficacy, endoscope compatibility, and operator safety.
22.5 Decontamination process 22.5.1 Initial clean The decontamination process should start as soon as an endoscope has been removed from a patient to minimize gross contamination. This step is sometimes referred to as the “bedside clean” and should be carried out in or close to the treatment room immediately after use. For most endoscopes this would comprise wiping the insertion tube with freshly prepared detergent solution, then aspirating detergent solution through the suction/biopsy channel and through the air/water channel using a dedicated valve according to the endoscope manufacturer’s guidance. The endoscope channels should not be allowed to dry between that initial clean and the subsequent full clean, and the endoscope should be enclosed while being transported to the decontamination unit to prevent matter drying onto surfaces, making it difficult to remove.
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22.5.2 Leak test Endoscopes are easily damaged during use and transport. One of the main manifestations of damage is that an endoscope can develop external and internal holes, and previously watertight junctions where different materials meet can be disrupted. There are two main consequences from such damage. First, liquids can access those internal parts of the endoscope intended to be dry and cause corrosion. This can compromise endoscope function and is expensive to repair. The longer the damage goes undetected, the more expensive the repair required. Second, patient body fluids can enter those internal areas where they will be inaccessible for removal and disinfection. When the endoscope is used in subsequent patients, changes in internal pressures as the endoscope is manipulated can expel those fluids, along with any pathogens in them. An endoscope’s integrity needs to be assessed after every use and before any cleaning, as immersion in detergent and disinfectant would increase the damage. Such testing for endoscope integrity is known as a “leak test.” Methods for leak testing vary between endoscope manufacturers but the most common method is to pass a small volume of air into the internal space of the endoscope to pressurize it. The entire endoscope is submerged in water and any escape of air through holes is identified by bubbles emerging from the endoscope. It is important that the bending section at the distal end is angulated as some small holes will only open when the outer covering is stretched. If any damage is detected, no further decontamination should be attempted and the endoscope should be sent immediately to the manufacturer for repair.
22.5.3 Manual cleaning When the endoscope arrives at the decontamination unit, all valves and port covers are removed. The endoscope is immersed in detergent solution, the outside wiped, and a cleaning brush passed down the length of the biopsy and suction channels. The air and water channels are the narrowest channels and, in most endoscopes, cannot accommodate a brush and can only be flushed. The instructions of the endoscope manufacturer must be followed, as there is a wide range of endoscope designs each with individual features. Failure to follow procedures recommended for that specific endoscope could result in total failure to clean unidentified channels. Many of the accessories used would fulfil the criterion of a high risk item (see Table 22.1) in that they are invasive items and so would require sterilization. In the United Kingdom, most of these items are single use rather than being reprocessed. The selection of a cleaning agent needs to be considered carefully. Neutral pH detergents can give rapid action and work at a wide range of temperatures. Enzymatic detergents may be slower to clean surfaces and can be temperature dependent. Allergic reactions affecting some operators have been reported due to the use of enzymatic detergents by staff [6] and this may influence the choice of cleaning agent. Once manual cleaning is complete, the endoscope should be rinsed internally and externally before being placed in an endoscope washer-disinfector.
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22.5.4 Endoscope washer-disinfector (EWD) cycle process All lumens of an endoscope are connected to the irrigation ports of an EWD and placed in the internal bowl or cage. Once a cycle commences the EWD will proceed through a series of stages: Leak test
Pre-cleaning
Cleaning Rinsing Disinfection Final rinse Drying
to detect a leak in the lumens or outer casing of the endoscope. As this leak test does not angulate the bending section (see Section 22.5.2 earlier), this should not replace the earlier manual leak test. to remove most residual soil. This stage may also include a flow check to ensure flow of fluid down all the channels. A blockage or channel disconnection can affect the flow detergent is used to aid the fine removal of soil to remove detergent to kill any micro-organisms remaining after cleaning to remove disinfectant to reduce, but not eliminate, the amount of residual water on and in the endoscope
Provided all the process parameters have been met, a processed endoscope should be clean and disinfected when removed from the EWD and ready for immediate reuse. If reuse is delayed beyond 3 h from completion of the EWD cycle, further reprocessing will usually be considered necessary [7], or the endoscope can be stored in a drying cabinet for its validated storage period (see Section 22.16 later). Disinfectants used in EWDs are usually used once only and then discarded. Some other disinfectants are intended for multiple reuses before being discarded. If EWDs use the disinfectant more than once several problems may arise: ●
●
Cumulative dilution during each use, making continued antimicrobial efficacy uncertain toward the end of the disinfectant’s use-life Carryover of contaminating material from one cycle to the next
A disinfectant test rapid assay (kit or indicator strip) used in accordance with the manufacturer’s guidance is recommended to ensure that the reusable disinfectant concentration is still effective.
22.6 Decontamination of duodenoscopes Duodenoscopes used for ERCP are more complex than other endoscopes. In order to visualize and cannulate the bile duct as it emerges into the duodenum, they need to have a light source and a camera that function at 90 degrees from the direction of endoscope travel. They also use a retractable lever, called the “raiser bridge” to turn accessories as they emerge through 90 degrees so that they can pass into the bile duct. This assembly is covered by a smooth cap to allow nontraumatic passage through the patient. The raiser bridge is elevated clear of the recessed area into its working position at the distal end of the endoscope by a control wire running via a lumen between the distal and proximal ends of the duodenoscope.
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These complexities create two additional challenges to effective decontamination: (1) The raiser bridge and the mechanism around it create areas that are poorly accessible for cleaning, requiring removal of the cap and specific brushing of recessed areas. (2) The lumen carrying the raiser bridge control wire is very narrow and almost completely filled by the wire. This leaves very little free space for detergent and disinfectant to flow through, requiring far higher pressures to do so than the other endoscope lumens. An additional problem with some models of duodenoscope has been that the cap is not removable, making adequate cleaning of the recessed areas within the endoscope impossible [8]. For decontamination of wire-carrying endoscopes, it is important to check that the EWD and drying cabinet have the correct pressure pumps for all channels.
22.7 Rinse water Rinsing an endoscope twice during the decontamination process is important. The intermediate rinse during the process cycle removes the detergent from the endoscope and the EWD pipe work preventing any inactivating reaction with the disinfectant that follows. The final rinse, using high quality water [7] with very low bacterial contamination, removes traces of disinfectant without microbial recontamination of the endoscope. Some disinfectants are hazardous to patients, even in high dilutions. One of the most common concerns in endoscope reprocessing is the significance of bacterial contamination found in the routine testing of rinse water. Even a new EWD can become contaminated before delivery during its factory testing and subsequent storage. Newly installed EWDs should be assessed for such contamination before they are accepted as fit for use. Ideally weekly cultures of 100 mL rinse water should show an absence of contamination. Counts of 1–10 colony forming units (cfu) are generally acceptable. Counts between 10 and 100 cfu need a risk assessment as to acceptability for specific types of endoscope and counts over 100 cfu require a more stringent risk assessment with removal of the EWD from use until the contamination is resolved as an option. In such a risk assessment, it should be remembered that these are counts per 100 ml and that less than 1 ml rinse water is likely to be left on an endoscope. An example of a risk assessment: An EWD with rinse water containing a total viable count (TVC) of 70 cfu per 100 mL may be considered acceptable for lower gastrointestinal tract endoscopy but not acceptable for bronchoscopy or cystoscopy. If it is not possible to differentiate which endoscopes are to be processed by which EWD with a high TVC in its rinse water, then the minimum acceptable standard should be that required for the highest risk endoscope. If that standard is exceeded, it may be possible to carry on providing a selective service for the lower risk procedures only, rather than abandoning all procedures. Risk assessments in such cases should be informed by clinical judgement rather than rigid application of arbitrary limits. It is important not to use risk assessment as a means of accepting lower standards but as a tool for overall risk minimization pending urgent rectification of the EWD contamination.
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In addition to the weekly TVC monitoring, endoscope rinse water should be cultured for the presence of P. aeruginosa and environmental mycobacteria every 3 months. P. aeruginosa is a significant pathogen and a contaminated EWD should not be used. The problem around environmental mycobacteria is mainly one of misdiagnosis; these can contaminate samples generated by endoscopy and will be indistinguishable on microscopy from M. tuberculosis. There is also a risk of infection via endoscopes introduced into sterile body cavities.
22.8 EWD selection When setting up a new or upgraded endoscopy decontamination unit, care must be taken in the selection of the EWD machines. There are many types of EWD, all have different characteristics and operate in different ways. When replacing an existing EWD with a new machine, one of the important areas to examine is the total cycle time of the new EWD. The total number of endoscopes processed per day will be known and this number, plus additional cycles for service expansion and EWD testing, must be allowed for within the working day. The purchase of new EWDs may require the replacement of the lumen connectors; it is likely that the old connectors will not fit the new EWDs.
22.9 Testing The decontamination process, in particular the EWD, needs to be tested to demonstrate that used endoscopes are cleaned and disinfected to a minimum standard. Routine tests on an EWD should be carried out on a regular basis, with various tests done on a daily, weekly, quarterly, or annual schedule. Such testing is detailed in Health Technical Memorandum (HTM) 01-06 [7], and BS EN 15883 Parts 1 [9] and 4 [10]. Testing the efficacy of manual cleaning is not described in these and will be the subject of local assessment. If such tests are done, they should focus on those parts of an endoscope that are most difficult to clean, for example brush-based sampling of lumens.
22.9.1 Water treatment The most critical rinse water used in an EWD is that of the final rinse. This should be chemically clean and of very low bio-burden. To achieve this level of quality usually requires that water from the supply main is treated. There are several treatment options ranging from microbiological filtration to reverse osmosis, the advice of a water treatment expert should be obtained. The requirements for final rinse water are included in EN 15883 Parts 1 [9] and 4 [10] and HTM 01-06 [7].
22.9.2 Machine decontamination Despite water being supplied to an EWD via a microbial-retentive filter, there is a hazard of the rinse circuits becoming colonized with bacteria in the form of a biofilm.
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This possibly originates from backtracking of contamination from contaminated used endoscopes in the decontamination chamber of the EWD. Mature biofilms are highly resistant to chemical disinfection. Daily disinfection of the EWD’s rinse circuits helps reduce such biofilm formation. If mature biofilms have been allowed to form it is possible that only replacement of rinse circuit components can eradicate the problem.
22.10 Endoscopy accessories 22.10.1 Biopsy forceps and other endoscopy instruments Many instruments passed down the biopsy channel of an endoscope are intended for single use, i.e., they are disposed of after their initial use and are not decontaminated and reused. Single-use instruments should be clearly marked as such. Single-use instruments are either not designed for easy cleaning, such as biopsy forceps, or may be damaged by the decontamination process. Failure to remove patient-derived material gives rise to two main risks: (1) failure of disinfection and (2) the failure to remove prion protein, a spongiform encephalopathy transmission risk.
22.10.2 Endoscopy water bottles A water bottle will be attached to the endoscopy trolley; the water it contains will be used to flush endoscope channels to check the device is operating correctly and for cleaning the endoscope lens during use. This water should be sterile and the containing bottles should either be cleaned and steam sterilized or should be single use. As there is a risk of bacterial growth in previously sterile water once it is dispensed into these water bottles, they should be filled at the start of each session and changed or replaced at the end of each session, but this should not exceed 3 hours.
22.11 Tracking and traceability The ability to trace endoscopes is important in the event of contact tracing when possible endoscopic transmission of infection is investigated. Records of the endoscope used (with a unique identifier) on an individual patient and the EWD and cycle parameters for the decontamination of that particular endoscope should be recorded. This may be carried out manually or electronically (for example, by scanning a barcode on each endoscope). Any reusable items such as valves and distal hood caps should be retained with the endoscope and processed as a set. Traceability systems should also be in place for any reusable accessories that are processed by steam sterilization. Loan endoscopes must also be included in the tracking and tracing system.
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22.12 Documentation Documentation is vital so that all procedures are carried out in a standard manner and training is standardized. A policy on endoscope decontamination should be available to users of the endoscope service stating how the service will provided. Comprehensive procedures will then support the policy by describing how endoscopes safe for patient use are going to be decontaminated. Procedures are a set of instructions on how to carry out a particular task, e.g., manual cleaning, use of an EWD, and storage time of processed endoscopes. Retained forms and log books are also useful as documented evidence that testing, maintenance, and self-disinfection of the EWD have taken place. Standard operating procedures (SOPs) are required for all tasks relating to the quality of the decontamination process. They must clearly describe in an understandable form the specific tasks. SOPs are an essential tool in training.
22.13 Staff training Staff carrying out the decontamination procedures should receive comprehensive training at induction and when any parts of the procedures are changed, e.g., detergent, EWD, and/or new endoscope are brought into use. Regular updates would also be beneficial and, as it is difficult to define “regular,” a local assessment should be undertaken to determine what would be appropriate. It could be considered that review should take place at annual appraisal, when new equipment is introduced or when changes occur in a staff member’s role and that this should be documented in training records. Suggested topics to include in the training package are ●
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Principles of infection control Basics of decontamination Health and safety Anatomy/channel configuration of flexible endoscopes Manual cleaning Use of an EWD Testing and maintenance of an EWD Tracking/traceability
The training should be supported by standard operating procedures for each task carried out and all training should be documented.
22.14 Extrinsic recontamination The layout within which processed endoscopes are stored and the procedures around their handling should prevent recontamination, particularly with blood and body fluid from other endoscopes before they are decontaminated. This is mainly achieved by the layout of the decontamination facility (see Section 22.17 later) that provides reliable
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physical separation of dirty and clean areas, and the design of the endoscope drying cabinet, which should allow the addition or removal of endoscopes without touching other items.
22.15 Intrinsic recontamination No matter how well processed in a washer-disinfector, endoscopes processed by EWDs will not be sterile; very low levels of microbial contaminants will inevitably remain, predominantly within lumens. There is also the possibility of the introduction of low numbers of microbes into lumens from the final rinse water. The lumens are difficult to dry and low volumes of water will probably still be present after the “drying” phase of a washer-disinfector. Replication of bacteria is likely in this environment with the possibility of subsequent transfer of those bacteria into patients. The greater the number of bacteria inoculated into a susceptible site on a patient, the greater the chance that they will initiate an infection. There is no defined safe number of microbes on a decontaminated endoscope, but they must neither present a risk to patients nor be a cause for misdiagnosis from samples obtained via endoscopy. The longer the storage period, the greater the bacterial replication that will occur [11]. If microbes have been allowed to replicate to any significant degree, the endoscope should be decontaminated again before use. There is an arbitrary period of 3 h of storage after decontamination that is typically the divider between being able to use an endoscope with no further decontamination and having to decontaminate again before reuse. This is a pragmatic time that is easy to comply with. It reflects the length of an endoscopy session so that a decontaminated endoscope should either be used in that session or decontaminated before use in the next session. This arbitrary time could be adapted by local risk assessment, which could allow the use of low risk (e.g., lower gastrointestinal) endoscopes for a whole working day for example if that is the only endoscope type being used. Other units which use a mix of low and high risk endoscope may prefer to have a single storage time allowed for all endoscopes; that time being the minimum allowable for safety.
22.16 Storage of endoscopes Endoscopes should be stored such that they are protected from damage and extrinsic recontamination and such that their original shape is retained on long-term storage. This can be achieved by suspending the endoscope in a specific endoscope storage cabinet and allowing their full length to hang down in a straight line without contact with the base of the cabinet. Endoscopes are valuable and their storage in a secure area is a safeguard against theft. There is a range of controlled environment storage cabinets that continuously irrigate all the lumens in an endoscope with filtered air, specifications for which are detailed in BS EN 16442 [12] and details of their testing in HTM 01-06 [7]. If such irrigation dries endoscopes within 3 h, these are referred to as drying cabinets. Ensuring
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that lumens are dry prevents microbial replication and allows the time before an endoscope needs decontamination to be greatly extended. There should be an indication in the cabinet showing if there is any failure of connection or irrigation of a lumen. Cabinets should have inbuilt timers for each stored endoscope whereby there is a clear visual display of either the time of storage or the time left before an endoscope must be decontaminated again; these should indicate if a storage limit has been exceeded. It is an advantage to instrument tracking and tracing systems if the identity and storage time of an endoscope can be recorded and captured in association with each use of that endoscope. There should be means to store accessories in association with a particular endoscope. Some endoscope drying cabinets have two entry doors such that the endoscope can be loaded into the cabinet in one room and removed in an adjoining room. There is a requirement that the interior of the cabinet be at slight positive pressure to prevent the ingress of unfiltered air, but this is secondary to the continuous irrigation of lumens. The time that a particular make of drying cabinet will extend the safe storage period is determined by a manufacturer’s tests on that cabinet and ensuring that all cabinets conform to that specification both when they are installed and on periodic testing thereafter. This periodic validation should be specified by the manufacturer but should include a daily check on the inbuilt manometer that the cabinet’s internal pressure is adequate. Every 3 months a check is recommended that the air filter is not blocked. There should also be an annual verification that the airflow through each endoscope lumen is being adequately monitored and that there has been recalibration of the cabinet’s inbuilt manometer.
22.17 Design of decontamination facilities The design of an endoscope decontamination facility is one of the prime determinants for reliable decontamination. While details of individual designs will vary with throughput and local space constraints, there are generic core considerations: ●
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There should be a designated and clear flow of endoscopes from dirty, i.e., as received after use, through each stage of decontamination, through to storage prior to release for use. Such flows are required to prevent recontamination of an endoscope by contact with a surface or staff hands that are contaminated by contact with an endoscope at a prior stage in decontamination. (Example: If an endoscope is removed from an EWD and put on a surface that is used for receiving used endoscopes, it will be recontaminated). Such a clear layout of flow from dirty to clean also helps prevent incidents where an incompletely decontaminated endoscope is mistakenly taken for use on a patient in the belief that it has been fully decontaminated. There should be a double sink for leak testing, washing and then rinsing endoscopes, with draining surfaces before the wash sink and after the rinsing sink. These sinks should be dedicated for this task and not used for other purposes such as handwashing. They sink units should be designed such that they can be raised and lowered to allow staff of different heights to use them easily. There should be controlled, secure storage of decontaminated endoscopes. This will enable endoscopes to be stored with specified time limits before they are either released for use or require further decontamination and will facilitate storage in a clean local environment that
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minimized recontamination. In addition, secure storage allows endoscopes to be released in a way that enable their use to be tracked and helps prevent endoscope theft; endoscopes are valuable and tradable commodities.
The first decision in designing an endoscope decontamination facility is its location. It should be readily accessible from the points of endoscope use. Alongside this will be deciding the number of endoscope reprocessing facilities in the healthcare provider. The endoscope user will usually favor an endoscope reprocessing facility adjacent to their point of endoscope use. This can lead to multiple small endoscope reprocessing areas within a single healthcare provider and is expensive in terms of equipment duplication, maintenance, and the overall space devoted to endoscope decontamination. This approach also presents problems in training all the staff who may be involved in each decontamination facility. While less convenient for the endoscope user, it is generally seen as a higher quality assurance approach to have a single endoscope decontamination unit within a hospital where equipment and specialist staff can be dedicated to that task. If endoscope decontamination is to occur at a location remote from the hospital, transport becomes a vital element, from the perspectives of rapid transport to the facility, turnaround time, preventing physical damage, and the preservation of microbial integrity of the decontaminated endoscopes. The next consideration is the layout of the decontamination facility itself [7], starting with the decision of a one room (Fig. 22.1) or a two room (Fig. 22.2) layout. In a two-room layout, there is a physical dividing wall between the dirty and the clean areas. As decontamination is the progression of multiple processes, the dividing point between clean and dirty is to some extent an arbitrary decision. The two most common approaches are that the divider is between the dirty and clean sides of double-ended EWDs or between the entry and exit sides of double-ended endoscope storage cabinets. If the main purpose of such a division is to prevent direct or indirect contact
Double sink units with work areas either side
Reasonable access space Water treatment equipment
EWD Optional table Personal protective equipment storage Waste bins
Traceability system Clean route
Endoscope storage cabinet[s]
Storage Endoscope entry
Endoscope dispatch
Fig. 22.1 A typical endoscope decontamination single room layout.
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Dirty returns
Traceability system
Double sink units with work areas either side Traceability
Barrier
Double-ended hatch for procedure segregation
Controlled staff entrance and clean endoscope exit
Optional table
Table Personal protective equipment storage Storage unit Flow Tracebility system Bins
EWD S
EWD Double-ended endoscope drying cabinet
Double-ended pass-through EWDs
Fig. 22.2 A typical endoscope decontamination two room layout.
between fully and partially decontaminated endoscopes, the best option seems to be to have two rooms each side of double-ended EWDs. The unit’s layout and available space will often have a great influence on the selection of EWDs. If possible, double-ended EWDs should be purchased, as this allows separation of clean and dirty tasks by building the EWDs into a dividing wall. In addition, the division may provide facilities for safely storing EWD chemical supplies. The use of single-ended EWDs in the same room as manual cleaning is always a compromise and requires careful layout to prevent the path of the endoscope from dirty to clean operations from crossing.
22.17.1 Using the decontamination facility There needs to be an area where used endoscopes enter the facility, e.g., via either a hatch or a door. The area immediately behind this should have sufficient storage space, usually as benching, to store all the received endoscopes before they enter the decontamination process. The endoscopes then proceed to the leak testing and washing sink. This sink should have a means to fill it with the correct volume of water and concentration of the detergent, usually a combination of a fill line on the sink and a dispenser (manual or mechanical) for adding a specific volume of detergent, and a thermometer to display the water temperature. Diagrams of each endoscope’s lumens should be available to remind the operator of the individual internal endoscope structures that need cleaning. A selection of lumen and orifice brushes (of sizes specified by the endoscope manufacturer), and wipes should be stored within easy reach. The adjacent sink should be used for rinsing the endoscopes with fresh water. Each endoscope should then be inspected for assurance that it is clean. High-quality task lighting is required for this.
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The endoscopes will then be loaded into an EWD. There should be sufficient storage, again usually on open benches, between the sinks and the EWDs to accommodate endoscopes awaiting the EWD. Throughout this process, there should be access to protective gloves, aprons and, where necessary, face protection for staff and receptacles for their disposal. Endoscopes are unloaded from the EWD by staff wearing clean gloves and aprons. Ideally there should be separate staff in an adjacent room unloading from double-ended EWDs. The endoscopes are then put into storage, either a storage cabinet or a drying cabinet, from which there will be controlled, recorded release to users.
22.18 Reasons for decontamination failure Failure to carry out effective decontamination may lead to transmission of infection. Reported incidents and causes have been reviewed by [3] and [4]. An awareness of possible reasons for failure can assist in the formulation of decontamination procedures. These include: ●
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Failure to irrigate all channels of an endoscope due to lack of awareness of the structure of an endoscope and/or not following the manufacturer’s instructions Failure to preclean and manually clean in accordance with the manufacturer’s instructions Failure to decontaminate reused accessories such as biopsy forceps Instruments being damaged by unsuitable accessories or mishandling Use of a disinfectant which does not have the necessary spectrum of activity: bactericidal (including M. tuberculosis) and virucidal Recontamination of a processed endoscope with water-associated bacteria either from the EWD or inadequately treated water Lack of maintenance of an EWD
References [1] Advisory Committee on Dangerous Pathogens (ACDP) TSE Risk Management Subgroup. Guidelines are updated as new data become available. Available at: https://www.gov.uk/ government/publications/guidance-from-the-acdp-tse-risk-management-subgroup-formerly-tse-working-group; 2017. [2] Spach DH, Silverstein FE, Stamm WE. Transmission of infection by gastrointestinal endoscopy and bronchoscopy. Ann Intern Med 1993;118(2):117–28. [3] Nelson DB. Infectious disease complications of GI endoscopy part II – exogenous infection. Gastrointest Endosc 2003;57(6):695–711. [4] Kovaleva J, Peters FTM, van der Mei HC, Degener JE. Clin Microbiol Rev 2013;26(2):231–54. [5] Ofstead CL, Wetzler HP, Snyder AK, Horton RA. Endoscope reprocessing methods. A prospective study on the impact of human factors and automation. Gastroenterol Nurs 2010;33:3–10. [6] Adisesh A, Murphy E, Barber CM, Ayres JG. Occupational asthma and rhinitis due to detergent enzymes in healthcare. Occup Med 2011;61:364–9.
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[7] Department of Health. Health technical memorandum 01-06 decontamination of flexible endoscopes. Available at: https://www.gov.uk/government/publications/management-and-decontamination-of-flexible-endoscopes; 2016. [8] Verfaillie CJ, Bruno MJ, Voor in ’t Holt AF, Buijs JG, Poley JW, Loeve AJ, Severin JA, Abel LF, Smit BJ, de Goeij I, Vos MC. Withdrawal of a novel-design duodenoscope ends outbreak of a VIM-2-producing Pseudomonas aeruginosa. Endoscopy 2015;47:493–502. [9] British Standards Institute. BS EN 15883 part 1Washer-disinfectors. General requirements, terms and definitions and tests; 2009. [10] British Standards Institute. BS EN 15883 part 4 Washer-disinfectors: Requirements and tests for washer-disinfectors employing chemical disinfection for thermolabile endoscopes; 2018. [11] Alfa MJ, Sitter DL. In hospital evaluation of contamination of duodenoscopes: a quantitative assessment of the effect of drying. J Hosp Infect 1991;19(2):88–98. [12] British Standards Institute. BS EN 16442 Controlled environment storage cabinet for processed thermolabile endoscopes; 2015.
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P. Hoffman Consultant Clinical Scientist, HCAI & AMR, Public Health England, London, United Kingdom
22.1 Types of endoscopes Endoscopes are tubular medical devices, parts of which enter the body to visualize internal structures for diagnostic purposes and, facilitated by this visualization, to take biopsies or carry out procedures. Structurally, endoscopes can be divided into rigid and flexible endoscopes. Rigid endoscopes are made of metal, are heat tolerant and can be cleaned in conventional surgical instrument washer-disinfectors and steam sterilized. For this reason, rigid endoscopes are classed as reprocessable surgical instruments which are dealt with in other chapters in this book. In contrast, flexible endoscopes are manufactured using thermolabile materials that cannot withstand surgical instrument washer-disinfectors or steam sterilization and present a specific set of challenges to effective decontamination. All endoscopes are centered around two core functions: (1) To illuminate internal body structures, light generated by a source outside the body is transmitted to the distal point inside the patient through a bundle of glass fibers. (2) To carry an image back out of the patient. Newer endoscopes use a photochip; older endoscopes use a glass fiber bundle with precisely the same alignment of fibers at both ends to carry the image, each light element being transmitted by an individual fiber.
22.2 Structure of endoscopes Flexible endoscopes range from those used for visualization only, e.g., nasendoscopes, to more complex devices that contain numerous channels, e.g., endoscopes used for endoscopic retrograde cholangiopancreatography (ERCP) and colonoscopy where biopsies may need to be taken. It is important that staff carrying out the decontamination procedure understand the structure of all endoscopes they are processing to ensure that all channels are accessed during decontamination. The channels in a typical endoscope occupy the entire length of the endoscope and can be as long as 2.5 m with internal diameters ranging from approximately 1 to 4 mm. The majority of flexible endoscopes have several internal lumens; one or more to pass biopsy instruments and therapeutic accessories (biopsy channel), joined at a Y junction to another lumen to remove fluid matter from obscuring the area being observed Decontamination in Hospitals and Healthcare. https://doi.org/10.1016/B978-0-08-102565-9.00022-4 © 2020 Elsevier Ltd. All rights reserved.
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(suction channel); other lumens are used to pass water to clean the visualizing lens (water channel) and to pass air to insufflate body cavities to facilitate viewing (air channel). Additional lumens for other functions may exist in more specialist endoscopes. Internal lumens can be complex and long, making their decontamination the most challenging aspect of endoscope reprocessing.
22.3 Risk assessment The standard approach to decontamination risk assessments is the approach illustrated in Table 22.1. However, for flexible endoscope decontamination this standard approach is problematic and more specific risk assessments are often required depending on the risk. Procedure types, in increasing order of risk, are given below: (a) As a minimum, endoscopes make contact with intact mucous membranes. It is impossible to guarantee that those mucous membranes will be intact. It seems reasonable to assume that, when investigating pathological conditions, there is a higher than normal chance of those mucous membranes being damaged. (b) The next stage up from this, in terms of risk, is when biopsies are taken, or surgical procedures carried out in contaminated body cavities. Here mucous membranes are intentionally breached, with the biopsy equipment used first passing through an endoscope lumen. (c) The risk scale progresses when endoscopes are used to enter body cavities that are normally sterile, such as the bladder, progressively increasing when surfaces are not intact or are entered for biopsies or procedures. (d) The highest risk category is when endoscopes are used surgically, and are in contact with normally sterile body tissues (as opposed to sterile body cavities).
For procedures in categories a, b, and c, it is important to realize that the endoscopes will either be used in an area that is naturally contaminated (e.g., colonoscopes) or will first pass through an area that is contaminated before they reach the normally sterile site (e.g., cystoscopes). In such cases, it seems unproductive to require those endoscopes to be sterile before use as they will inevitably be contaminated when they reach their point of use. With these endoscopes, the prevention of infection transmission is achieved by ensuring that pathogens acquired in the procedure on the previous Table 22.1 Risks from medical instruments, equipment, and environment. Instruments that come into contact with
Risk level
Decontamination required
Normally sterile body tissues Intact mucous membrane
High Medium
Intact skin
Low
Surfaces not normally in contact with intact skin
Minimal
Sterilize Sterilize, heat disinfect, chemical disinfect only if thermolabile Disinfect or clean (depending on patient susceptibility) Clean; disinfect only in special circumstances
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patient are eliminated and by preventing significant recontamination. Prevention of significant recontamination can be divided into three areas: (1) Prevention of contamination via the rinse water used to remove disinfectant from the endoscope, (2) prevention of replication of residual contamination within the endoscope on storage, and (3) prevention of recontamination, directly or indirectly, with contamination from other endoscopes before they are decontaminated and similarly with any patient blood or body fluid. For endoscopes used in category d (highest risk), processing in an endoscope washer-disinfector, followed by complete drying, followed by a quality assured, compatible low temperature sterilization is the preferred option. Clinical risk assessments should take account of: ●
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The risk of the procedure (see above) The susceptibility of individual patients The nature and extent of residual contamination likely to be present on an endoscope
An example of a risk assessment relating to contamination of rinse water is in Section 22.7 later in this chapter. The risk assessment should also be applied to the conditions and duration of storage of endoscopes between decontamination and reuse. Here the hazard is of the regrowth of bacteria in incompletely dried endoscope lumens leading to patient infection or misdiagnosis (e.g., mycobacteria in diagnostic samples from bronchoscopies). More details are given in Section 22.16 later. The endoscope-mediated transmission of disease associated with transmissible spongiform encephalopathies (TSEs), primarily Creutzfeldt-Jakob disease (CJD) and variant Creutzfeldt-Jakob disease (vCJD), should also form part of a risk assessment. In the United Kingdom, detailed guidance on this is given by the Advisory Committee on Dangerous Pathogens (ACDP) TSE Risk Management Subgroup [1] in Annex F of their guidance. This is updated as required and should be referred to for any detailed risk assessment; only general principles are given in this chapter. The agents of TSEs (prions) are exceptionally resistant to heat and chemical inactivation and are also thought to adhere strongly to surfaces, particularly if allowed to dry, and thus to resist removal by cleaning. Ascertainment of risk [1] comprises assessment of individuals in respect of their likely carriage of prion disease combined with the tissues the endoscope will make contact with for their potential level of prion contamination. Patients are categorized into either definite/probable prion carriage, possible or asymptomatic but at risk, or patients at no known risk. Body tissues are classified as high risk (brain and spinal cord), medium risk (olfactory epithelium for CJD or olfactory epithelium and lymphoid tissue for vCJD), or low risk for other tissues. For patients at definite/probable, possible or at risk of prion carriage, if the endoscope is in contact with high risk or medium tissues, it should be kept for reuse solely on that patient or destroyed after use (or quarantined pending final diagnosis, during which time it can be reused on the same patient). In these patients, if the endoscope is in contact with low-risk tissues, no special precautions are needed. For patients not known to be at increased prion risk, for endoscopes to be used in contact with all tissues, no additional precautions are needed.
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22.4 Flexible endoscope decontamination 22.4.1 Risk of infection The risk of infection following flexible endoscopy is considered to be low in relation to the number of procedures carried out [2], but the true infection rate remains unclear as many of the patients are examined as day cases so are not followed up. Nelson [3] and Kovaleva et al. [4] have reviewed infections attributed to endoscopes, which include: Salmonella species including S. typhi, Pseudomonas aeruginosa, Helicobacter pylori, Mycobacterium tuberculosis and other Mycobacteria, hepatitis B and C viruses, Strongyloides stercoralis, and Trichosporon species.
22.4.2 Problems Flexible endoscopes are heat sensitive, have a complex structure, and are made of various materials. The channel configuration varies depending on the type of endoscopes. Some are used for visualization only and will have few or no channels; others are for therapeutic/diagnostic procedures and will have several channels. This variation can cause problems for decontamination staff if they are unfamiliar with the structure of the endoscopes they are dealing with as it is important to access all channels during the decontamination procedure. The high cost of flexible endoscopes often means there are usually a minimal number of endoscopes available and that, coupled with the rapid throughput of patients, can put time pressures on the decontamination procedure. Ofstead et al. [5] carried out a prospective study on endoscope reprocessing which showed that a lack of time was a factor in the deviation from standard procedures. An assurance of the decontamination process is essential, and all stages should be recorded. The selection of a disinfectant requires a balance between efficacy, endoscope compatibility, and operator safety.
22.5 Decontamination process 22.5.1 Initial clean The decontamination process should start as soon as an endoscope has been removed from a patient to minimize gross contamination. This step is sometimes referred to as the “bedside clean” and should be carried out in or close to the treatment room immediately after use. For most endoscopes this would comprise wiping the insertion tube with freshly prepared detergent solution, then aspirating detergent solution through the suction/biopsy channel and through the air/water channel using a dedicated valve according to the endoscope manufacturer’s guidance. The endoscope channels should not be allowed to dry between that initial clean and the subsequent full clean, and the endoscope should be enclosed while being transported to the decontamination unit to prevent matter drying onto surfaces, making it difficult to remove.
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22.5.2 Leak test Endoscopes are easily damaged during use and transport. One of the main manifestations of damage is that an endoscope can develop external and internal holes, and previously watertight junctions where different materials meet can be disrupted. There are two main consequences from such damage. First, liquids can access those internal parts of the endoscope intended to be dry and cause corrosion. This can compromise endoscope function and is expensive to repair. The longer the damage goes undetected, the more expensive the repair required. Second, patient body fluids can enter those internal areas where they will be inaccessible for removal and disinfection. When the endoscope is used in subsequent patients, changes in internal pressures as the endoscope is manipulated can expel those fluids, along with any pathogens in them. An endoscope’s integrity needs to be assessed after every use and before any cleaning, as immersion in detergent and disinfectant would increase the damage. Such testing for endoscope integrity is known as a “leak test.” Methods for leak testing vary between endoscope manufacturers but the most common method is to pass a small volume of air into the internal space of the endoscope to pressurize it. The entire endoscope is submerged in water and any escape of air through holes is identified by bubbles emerging from the endoscope. It is important that the bending section at the distal end is angulated as some small holes will only open when the outer covering is stretched. If any damage is detected, no further decontamination should be attempted and the endoscope should be sent immediately to the manufacturer for repair.
22.5.3 Manual cleaning When the endoscope arrives at the decontamination unit, all valves and port covers are removed. The endoscope is immersed in detergent solution, the outside wiped, and a cleaning brush passed down the length of the biopsy and suction channels. The air and water channels are the narrowest channels and, in most endoscopes, cannot accommodate a brush and can only be flushed. The instructions of the endoscope manufacturer must be followed, as there is a wide range of endoscope designs each with individual features. Failure to follow procedures recommended for that specific endoscope could result in total failure to clean unidentified channels. Many of the accessories used would fulfil the criterion of a high risk item (see Table 22.1) in that they are invasive items and so would require sterilization. In the United Kingdom, most of these items are single use rather than being reprocessed. The selection of a cleaning agent needs to be considered carefully. Neutral pH detergents can give rapid action and work at a wide range of temperatures. Enzymatic detergents may be slower to clean surfaces and can be temperature dependent. Allergic reactions affecting some operators have been reported due to the use of enzymatic detergents by staff [6] and this may influence the choice of cleaning agent. Once manual cleaning is complete, the endoscope should be rinsed internally and externally before being placed in an endoscope washer-disinfector.
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22.5.4 Endoscope washer-disinfector (EWD) cycle process All lumens of an endoscope are connected to the irrigation ports of an EWD and placed in the internal bowl or cage. Once a cycle commences the EWD will proceed through a series of stages: Leak test
Pre-cleaning
Cleaning Rinsing Disinfection Final rinse Drying
to detect a leak in the lumens or outer casing of the endoscope. As this leak test does not angulate the bending section (see Section 22.5.2 earlier), this should not replace the earlier manual leak test. to remove most residual soil. This stage may also include a flow check to ensure flow of fluid down all the channels. A blockage or channel disconnection can affect the flow detergent is used to aid the fine removal of soil to remove detergent to kill any micro-organisms remaining after cleaning to remove disinfectant to reduce, but not eliminate, the amount of residual water on and in the endoscope
Provided all the process parameters have been met, a processed endoscope should be clean and disinfected when removed from the EWD and ready for immediate reuse. If reuse is delayed beyond 3 h from completion of the EWD cycle, further reprocessing will usually be considered necessary [7], or the endoscope can be stored in a drying cabinet for its validated storage period (see Section 22.16 later). Disinfectants used in EWDs are usually used once only and then discarded. Some other disinfectants are intended for multiple reuses before being discarded. If EWDs use the disinfectant more than once several problems may arise: ●
●
Cumulative dilution during each use, making continued antimicrobial efficacy uncertain toward the end of the disinfectant’s use-life Carryover of contaminating material from one cycle to the next
A disinfectant test rapid assay (kit or indicator strip) used in accordance with the manufacturer’s guidance is recommended to ensure that the reusable disinfectant concentration is still effective.
22.6 Decontamination of duodenoscopes Duodenoscopes used for ERCP are more complex than other endoscopes. In order to visualize and cannulate the bile duct as it emerges into the duodenum, they need to have a light source and a camera that function at 90 degrees from the direction of endoscope travel. They also use a retractable lever, called the “raiser bridge” to turn accessories as they emerge through 90 degrees so that they can pass into the bile duct. This assembly is covered by a smooth cap to allow nontraumatic passage through the patient. The raiser bridge is elevated clear of the recessed area into its working position at the distal end of the endoscope by a control wire running via a lumen between the distal and proximal ends of the duodenoscope.
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These complexities create two additional challenges to effective decontamination: (1) The raiser bridge and the mechanism around it create areas that are poorly accessible for cleaning, requiring removal of the cap and specific brushing of recessed areas. (2) The lumen carrying the raiser bridge control wire is very narrow and almost completely filled by the wire. This leaves very little free space for detergent and disinfectant to flow through, requiring far higher pressures to do so than the other endoscope lumens. An additional problem with some models of duodenoscope has been that the cap is not removable, making adequate cleaning of the recessed areas within the endoscope impossible [8]. For decontamination of wire-carrying endoscopes, it is important to check that the EWD and drying cabinet have the correct pressure pumps for all channels.
22.7 Rinse water Rinsing an endoscope twice during the decontamination process is important. The intermediate rinse during the process cycle removes the detergent from the endoscope and the EWD pipe work preventing any inactivating reaction with the disinfectant that follows. The final rinse, using high quality water [7] with very low bacterial contamination, removes traces of disinfectant without microbial recontamination of the endoscope. Some disinfectants are hazardous to patients, even in high dilutions. One of the most common concerns in endoscope reprocessing is the significance of bacterial contamination found in the routine testing of rinse water. Even a new EWD can become contaminated before delivery during its factory testing and subsequent storage. Newly installed EWDs should be assessed for such contamination before they are accepted as fit for use. Ideally weekly cultures of 100 mL rinse water should show an absence of contamination. Counts of 1–10 colony forming units (cfu) are generally acceptable. Counts between 10 and 100 cfu need a risk assessment as to acceptability for specific types of endoscope and counts over 100 cfu require a more stringent risk assessment with removal of the EWD from use until the contamination is resolved as an option. In such a risk assessment, it should be remembered that these are counts per 100 ml and that less than 1 ml rinse water is likely to be left on an endoscope. An example of a risk assessment: An EWD with rinse water containing a total viable count (TVC) of 70 cfu per 100 mL may be considered acceptable for lower gastrointestinal tract endoscopy but not acceptable for bronchoscopy or cystoscopy. If it is not possible to differentiate which endoscopes are to be processed by which EWD with a high TVC in its rinse water, then the minimum acceptable standard should be that required for the highest risk endoscope. If that standard is exceeded, it may be possible to carry on providing a selective service for the lower risk procedures only, rather than abandoning all procedures. Risk assessments in such cases should be informed by clinical judgement rather than rigid application of arbitrary limits. It is important not to use risk assessment as a means of accepting lower standards but as a tool for overall risk minimization pending urgent rectification of the EWD contamination.
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In addition to the weekly TVC monitoring, endoscope rinse water should be cultured for the presence of P. aeruginosa and environmental mycobacteria every 3 months. P. aeruginosa is a significant pathogen and a contaminated EWD should not be used. The problem around environmental mycobacteria is mainly one of misdiagnosis; these can contaminate samples generated by endoscopy and will be indistinguishable on microscopy from M. tuberculosis. There is also a risk of infection via endoscopes introduced into sterile body cavities.
22.8 EWD selection When setting up a new or upgraded endoscopy decontamination unit, care must be taken in the selection of the EWD machines. There are many types of EWD, all have different characteristics and operate in different ways. When replacing an existing EWD with a new machine, one of the important areas to examine is the total cycle time of the new EWD. The total number of endoscopes processed per day will be known and this number, plus additional cycles for service expansion and EWD testing, must be allowed for within the working day. The purchase of new EWDs may require the replacement of the lumen connectors; it is likely that the old connectors will not fit the new EWDs.
22.9 Testing The decontamination process, in particular the EWD, needs to be tested to demonstrate that used endoscopes are cleaned and disinfected to a minimum standard. Routine tests on an EWD should be carried out on a regular basis, with various tests done on a daily, weekly, quarterly, or annual schedule. Such testing is detailed in Health Technical Memorandum (HTM) 01-06 [7], and BS EN 15883 Parts 1 [9] and 4 [10]. Testing the efficacy of manual cleaning is not described in these and will be the subject of local assessment. If such tests are done, they should focus on those parts of an endoscope that are most difficult to clean, for example brush-based sampling of lumens.
22.9.1 Water treatment The most critical rinse water used in an EWD is that of the final rinse. This should be chemically clean and of very low bio-burden. To achieve this level of quality usually requires that water from the supply main is treated. There are several treatment options ranging from microbiological filtration to reverse osmosis, the advice of a water treatment expert should be obtained. The requirements for final rinse water are included in EN 15883 Parts 1 [9] and 4 [10] and HTM 01-06 [7].
22.9.2 Machine decontamination Despite water being supplied to an EWD via a microbial-retentive filter, there is a hazard of the rinse circuits becoming colonized with bacteria in the form of a biofilm.
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This possibly originates from backtracking of contamination from contaminated used endoscopes in the decontamination chamber of the EWD. Mature biofilms are highly resistant to chemical disinfection. Daily disinfection of the EWD’s rinse circuits helps reduce such biofilm formation. If mature biofilms have been allowed to form it is possible that only replacement of rinse circuit components can eradicate the problem.
22.10 Endoscopy accessories 22.10.1 Biopsy forceps and other endoscopy instruments Many instruments passed down the biopsy channel of an endoscope are intended for single use, i.e., they are disposed of after their initial use and are not decontaminated and reused. Single-use instruments should be clearly marked as such. Single-use instruments are either not designed for easy cleaning, such as biopsy forceps, or may be damaged by the decontamination process. Failure to remove patient-derived material gives rise to two main risks: (1) failure of disinfection and (2) the failure to remove prion protein, a spongiform encephalopathy transmission risk.
22.10.2 Endoscopy water bottles A water bottle will be attached to the endoscopy trolley; the water it contains will be used to flush endoscope channels to check the device is operating correctly and for cleaning the endoscope lens during use. This water should be sterile and the containing bottles should either be cleaned and steam sterilized or should be single use. As there is a risk of bacterial growth in previously sterile water once it is dispensed into these water bottles, they should be filled at the start of each session and changed or replaced at the end of each session, but this should not exceed 3 hours.
22.11 Tracking and traceability The ability to trace endoscopes is important in the event of contact tracing when possible endoscopic transmission of infection is investigated. Records of the endoscope used (with a unique identifier) on an individual patient and the EWD and cycle parameters for the decontamination of that particular endoscope should be recorded. This may be carried out manually or electronically (for example, by scanning a barcode on each endoscope). Any reusable items such as valves and distal hood caps should be retained with the endoscope and processed as a set. Traceability systems should also be in place for any reusable accessories that are processed by steam sterilization. Loan endoscopes must also be included in the tracking and tracing system.
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22.12 Documentation Documentation is vital so that all procedures are carried out in a standard manner and training is standardized. A policy on endoscope decontamination should be available to users of the endoscope service stating how the service will provided. Comprehensive procedures will then support the policy by describing how endoscopes safe for patient use are going to be decontaminated. Procedures are a set of instructions on how to carry out a particular task, e.g., manual cleaning, use of an EWD, and storage time of processed endoscopes. Retained forms and log books are also useful as documented evidence that testing, maintenance, and self-disinfection of the EWD have taken place. Standard operating procedures (SOPs) are required for all tasks relating to the quality of the decontamination process. They must clearly describe in an understandable form the specific tasks. SOPs are an essential tool in training.
22.13 Staff training Staff carrying out the decontamination procedures should receive comprehensive training at induction and when any parts of the procedures are changed, e.g., detergent, EWD, and/or new endoscope are brought into use. Regular updates would also be beneficial and, as it is difficult to define “regular,” a local assessment should be undertaken to determine what would be appropriate. It could be considered that review should take place at annual appraisal, when new equipment is introduced or when changes occur in a staff member’s role and that this should be documented in training records. Suggested topics to include in the training package are ●
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●
●
●
●
●
Principles of infection control Basics of decontamination Health and safety Anatomy/channel configuration of flexible endoscopes Manual cleaning Use of an EWD Testing and maintenance of an EWD Tracking/traceability
The training should be supported by standard operating procedures for each task carried out and all training should be documented.
22.14 Extrinsic recontamination The layout within which processed endoscopes are stored and the procedures around their handling should prevent recontamination, particularly with blood and body fluid from other endoscopes before they are decontaminated. This is mainly achieved by the layout of the decontamination facility (see Section 22.17 later) that provides reliable
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physical separation of dirty and clean areas, and the design of the endoscope drying cabinet, which should allow the addition or removal of endoscopes without touching other items.
22.15 Intrinsic recontamination No matter how well processed in a washer-disinfector, endoscopes processed by EWDs will not be sterile; very low levels of microbial contaminants will inevitably remain, predominantly within lumens. There is also the possibility of the introduction of low numbers of microbes into lumens from the final rinse water. The lumens are difficult to dry and low volumes of water will probably still be present after the “drying” phase of a washer-disinfector. Replication of bacteria is likely in this environment with the possibility of subsequent transfer of those bacteria into patients. The greater the number of bacteria inoculated into a susceptible site on a patient, the greater the chance that they will initiate an infection. There is no defined safe number of microbes on a decontaminated endoscope, but they must neither present a risk to patients nor be a cause for misdiagnosis from samples obtained via endoscopy. The longer the storage period, the greater the bacterial replication that will occur [11]. If microbes have been allowed to replicate to any significant degree, the endoscope should be decontaminated again before use. There is an arbitrary period of 3 h of storage after decontamination that is typically the divider between being able to use an endoscope with no further decontamination and having to decontaminate again before reuse. This is a pragmatic time that is easy to comply with. It reflects the length of an endoscopy session so that a decontaminated endoscope should either be used in that session or decontaminated before use in the next session. This arbitrary time could be adapted by local risk assessment, which could allow the use of low risk (e.g., lower gastrointestinal) endoscopes for a whole working day for example if that is the only endoscope type being used. Other units which use a mix of low and high risk endoscope may prefer to have a single storage time allowed for all endoscopes; that time being the minimum allowable for safety.
22.16 Storage of endoscopes Endoscopes should be stored such that they are protected from damage and extrinsic recontamination and such that their original shape is retained on long-term storage. This can be achieved by suspending the endoscope in a specific endoscope storage cabinet and allowing their full length to hang down in a straight line without contact with the base of the cabinet. Endoscopes are valuable and their storage in a secure area is a safeguard against theft. There is a range of controlled environment storage cabinets that continuously irrigate all the lumens in an endoscope with filtered air, specifications for which are detailed in BS EN 16442 [12] and details of their testing in HTM 01-06 [7]. If such irrigation dries endoscopes within 3 h, these are referred to as drying cabinets. Ensuring
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that lumens are dry prevents microbial replication and allows the time before an endoscope needs decontamination to be greatly extended. There should be an indication in the cabinet showing if there is any failure of connection or irrigation of a lumen. Cabinets should have inbuilt timers for each stored endoscope whereby there is a clear visual display of either the time of storage or the time left before an endoscope must be decontaminated again; these should indicate if a storage limit has been exceeded. It is an advantage to instrument tracking and tracing systems if the identity and storage time of an endoscope can be recorded and captured in association with each use of that endoscope. There should be means to store accessories in association with a particular endoscope. Some endoscope drying cabinets have two entry doors such that the endoscope can be loaded into the cabinet in one room and removed in an adjoining room. There is a requirement that the interior of the cabinet be at slight positive pressure to prevent the ingress of unfiltered air, but this is secondary to the continuous irrigation of lumens. The time that a particular make of drying cabinet will extend the safe storage period is determined by a manufacturer’s tests on that cabinet and ensuring that all cabinets conform to that specification both when they are installed and on periodic testing thereafter. This periodic validation should be specified by the manufacturer but should include a daily check on the inbuilt manometer that the cabinet’s internal pressure is adequate. Every 3 months a check is recommended that the air filter is not blocked. There should also be an annual verification that the airflow through each endoscope lumen is being adequately monitored and that there has been recalibration of the cabinet’s inbuilt manometer.
22.17 Design of decontamination facilities The design of an endoscope decontamination facility is one of the prime determinants for reliable decontamination. While details of individual designs will vary with throughput and local space constraints, there are generic core considerations: ●
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There should be a designated and clear flow of endoscopes from dirty, i.e., as received after use, through each stage of decontamination, through to storage prior to release for use. Such flows are required to prevent recontamination of an endoscope by contact with a surface or staff hands that are contaminated by contact with an endoscope at a prior stage in decontamination. (Example: If an endoscope is removed from an EWD and put on a surface that is used for receiving used endoscopes, it will be recontaminated). Such a clear layout of flow from dirty to clean also helps prevent incidents where an incompletely decontaminated endoscope is mistakenly taken for use on a patient in the belief that it has been fully decontaminated. There should be a double sink for leak testing, washing and then rinsing endoscopes, with draining surfaces before the wash sink and after the rinsing sink. These sinks should be dedicated for this task and not used for other purposes such as handwashing. They sink units should be designed such that they can be raised and lowered to allow staff of different heights to use them easily. There should be controlled, secure storage of decontaminated endoscopes. This will enable endoscopes to be stored with specified time limits before they are either released for use or require further decontamination and will facilitate storage in a clean local environment that
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minimized recontamination. In addition, secure storage allows endoscopes to be released in a way that enable their use to be tracked and helps prevent endoscope theft; endoscopes are valuable and tradable commodities.
The first decision in designing an endoscope decontamination facility is its location. It should be readily accessible from the points of endoscope use. Alongside this will be deciding the number of endoscope reprocessing facilities in the healthcare provider. The endoscope user will usually favor an endoscope reprocessing facility adjacent to their point of endoscope use. This can lead to multiple small endoscope reprocessing areas within a single healthcare provider and is expensive in terms of equipment duplication, maintenance, and the overall space devoted to endoscope decontamination. This approach also presents problems in training all the staff who may be involved in each decontamination facility. While less convenient for the endoscope user, it is generally seen as a higher quality assurance approach to have a single endoscope decontamination unit within a hospital where equipment and specialist staff can be dedicated to that task. If endoscope decontamination is to occur at a location remote from the hospital, transport becomes a vital element, from the perspectives of rapid transport to the facility, turnaround time, preventing physical damage, and the preservation of microbial integrity of the decontaminated endoscopes. The next consideration is the layout of the decontamination facility itself [7], starting with the decision of a one room (Fig. 22.1) or a two room (Fig. 22.2) layout. In a two-room layout, there is a physical dividing wall between the dirty and the clean areas. As decontamination is the progression of multiple processes, the dividing point between clean and dirty is to some extent an arbitrary decision. The two most common approaches are that the divider is between the dirty and clean sides of double-ended EWDs or between the entry and exit sides of double-ended endoscope storage cabinets. If the main purpose of such a division is to prevent direct or indirect contact
Double sink units with work areas either side
Reasonable access space Water treatment equipment
EWD Optional table Personal protective equipment storage Waste bins
Traceability system Clean route
Endoscope storage cabinet[s]
Storage Endoscope entry
Endoscope dispatch
Fig. 22.1 A typical endoscope decontamination single room layout.
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Dirty returns
Traceability system
Double sink units with work areas either side Traceability
Barrier
Double-ended hatch for procedure segregation
Controlled staff entrance and clean endoscope exit
Optional table
Table Personal protective equipment storage Storage unit Flow Tracebility system Bins
EWD S
EWD Double-ended endoscope drying cabinet
Double-ended pass-through EWDs
Fig. 22.2 A typical endoscope decontamination two room layout.
between fully and partially decontaminated endoscopes, the best option seems to be to have two rooms each side of double-ended EWDs. The unit’s layout and available space will often have a great influence on the selection of EWDs. If possible, double-ended EWDs should be purchased, as this allows separation of clean and dirty tasks by building the EWDs into a dividing wall. In addition, the division may provide facilities for safely storing EWD chemical supplies. The use of single-ended EWDs in the same room as manual cleaning is always a compromise and requires careful layout to prevent the path of the endoscope from dirty to clean operations from crossing.
22.17.1 Using the decontamination facility There needs to be an area where used endoscopes enter the facility, e.g., via either a hatch or a door. The area immediately behind this should have sufficient storage space, usually as benching, to store all the received endoscopes before they enter the decontamination process. The endoscopes then proceed to the leak testing and washing sink. This sink should have a means to fill it with the correct volume of water and concentration of the detergent, usually a combination of a fill line on the sink and a dispenser (manual or mechanical) for adding a specific volume of detergent, and a thermometer to display the water temperature. Diagrams of each endoscope’s lumens should be available to remind the operator of the individual internal endoscope structures that need cleaning. A selection of lumen and orifice brushes (of sizes specified by the endoscope manufacturer), and wipes should be stored within easy reach. The adjacent sink should be used for rinsing the endoscopes with fresh water. Each endoscope should then be inspected for assurance that it is clean. High-quality task lighting is required for this.
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The endoscopes will then be loaded into an EWD. There should be sufficient storage, again usually on open benches, between the sinks and the EWDs to accommodate endoscopes awaiting the EWD. Throughout this process, there should be access to protective gloves, aprons and, where necessary, face protection for staff and receptacles for their disposal. Endoscopes are unloaded from the EWD by staff wearing clean gloves and aprons. Ideally there should be separate staff in an adjacent room unloading from double-ended EWDs. The endoscopes are then put into storage, either a storage cabinet or a drying cabinet, from which there will be controlled, recorded release to users.
22.18 Reasons for decontamination failure Failure to carry out effective decontamination may lead to transmission of infection. Reported incidents and causes have been reviewed by [3] and [4]. An awareness of possible reasons for failure can assist in the formulation of decontamination procedures. These include: ●
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Failure to irrigate all channels of an endoscope due to lack of awareness of the structure of an endoscope and/or not following the manufacturer’s instructions Failure to preclean and manually clean in accordance with the manufacturer’s instructions Failure to decontaminate reused accessories such as biopsy forceps Instruments being damaged by unsuitable accessories or mishandling Use of a disinfectant which does not have the necessary spectrum of activity: bactericidal (including M. tuberculosis) and virucidal Recontamination of a processed endoscope with water-associated bacteria either from the EWD or inadequately treated water Lack of maintenance of an EWD
References [1] Advisory Committee on Dangerous Pathogens (ACDP) TSE Risk Management Subgroup. Guidelines are updated as new data become available. Available at: https://www.gov.uk/ government/publications/guidance-from-the-acdp-tse-risk-management-subgroup-formerly-tse-working-group; 2017. [2] Spach DH, Silverstein FE, Stamm WE. Transmission of infection by gastrointestinal endoscopy and bronchoscopy. Ann Intern Med 1993;118(2):117–28. [3] Nelson DB. Infectious disease complications of GI endoscopy part II – exogenous infection. Gastrointest Endosc 2003;57(6):695–711. [4] Kovaleva J, Peters FTM, van der Mei HC, Degener JE. Clin Microbiol Rev 2013;26(2):231–54. [5] Ofstead CL, Wetzler HP, Snyder AK, Horton RA. Endoscope reprocessing methods. A prospective study on the impact of human factors and automation. Gastroenterol Nurs 2010;33:3–10. [6] Adisesh A, Murphy E, Barber CM, Ayres JG. Occupational asthma and rhinitis due to detergent enzymes in healthcare. Occup Med 2011;61:364–9.
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[7] Department of Health. Health technical memorandum 01-06 decontamination of flexible endoscopes. Available at: https://www.gov.uk/government/publications/management-and-decontamination-of-flexible-endoscopes; 2016. [8] Verfaillie CJ, Bruno MJ, Voor in ’t Holt AF, Buijs JG, Poley JW, Loeve AJ, Severin JA, Abel LF, Smit BJ, de Goeij I, Vos MC. Withdrawal of a novel-design duodenoscope ends outbreak of a VIM-2-producing Pseudomonas aeruginosa. Endoscopy 2015;47:493–502. [9] British Standards Institute. BS EN 15883 part 1Washer-disinfectors. General requirements, terms and definitions and tests; 2009. [10] British Standards Institute. BS EN 15883 part 4 Washer-disinfectors: Requirements and tests for washer-disinfectors employing chemical disinfection for thermolabile endoscopes; 2018. [11] Alfa MJ, Sitter DL. In hospital evaluation of contamination of duodenoscopes: a quantitative assessment of the effect of drying. J Hosp Infect 1991;19(2):88–98. [12] British Standards Institute. BS EN 16442 Controlled environment storage cabinet for processed thermolabile endoscopes; 2015.