Technical aspects of duodenoscope design that contribute to infections and where we can make a difference in mitigating/preventing infections

Dr. Chapman is an Assistant Professor of Medicine and Director of Bariatric and Metabolic Endoscopy at UChicago Medicine.

ERCP is a technically challenging procedure that provides significant therapeutic benefits to patients, however the design of traditional fixed endcap duodenoscopes can make manual and automated disinfection challenging and increase the risk of infection transmission.
Recent efforts to optimize the design and mitigate the risk of infection have included the implementation of innovative disposable components designed to make reprocessing easier, more effective or unnecessary and include disposable end caps, protective end sheaths, and fully disposable, single use duodenoscopes.
The transition to disposable components and fully disposable duodenoscopes is underway but full adoption will require continued investigation and technical development balancing the ability to safely perform these complex procedures, while remaining cost effective and minimizing waste.

Introduction

Endoscopic retrograde cholangiopancreatography (ERCP) is an established therapeutic option for benign and malignant pancreaticobiliary conditions accounting for over 500,000 procedures annually in the United States1. It remains arguably one of the most complex and higher-risk endoscopic procedures requiring specialized training as well as the use of uniquely designed duodenoscopes that contain a cable actuated elevator in the distal tip. Despite the therapeutic benefits of ERCP, recent reports of exogenous, patient-to-patient multi-drug resistant organism (MDRO) infection transmission leading to fatal outbreaks have raised significant concerns about the design of the traditional fixed endcap duodenoscope.

The Scope of the Problem

In 2013, the Center for Disease Prevention and Control (CDC) warned the Food and Drug Administration (FDA) of the potential association between MDRO infections and duodenoscopes. Since that time, the FDA has closely tracked reports of adverse events with duodenoscopes and between January 2015 to mid-2019, identified a total of 553 reports of patient infections and a total of 79 death reports associated with patient infection, exposure or device contamination involving duodenoscopes 2. The trend in reported FDA data indicate a decrease in the number of reported infections (247 in 2015 to 55 in the first half of 2019) and death reports (25 in 2015 to less than 5 in first half of 2019). Although the decrease in rates of infection and deaths may be indicative that mitigating efforts have been partially successful, surveillance contamination data strongly indicate on-going risk. In fact, duodenoscope manufacturer post-market surveillance data identified high concern organisms remaining in up to 5% of post-reprocessed duodenoscopes3. Although controversially used as a surrogate for infection risk, bacterial contamination rates have been reported to be as high as 15% to 22% in reprocessed, “patient-ready” duodenoscopes 4-5. Thus, additional improvements are necessary to even further decrease the risk of infection and efforts to address design limitations of the traditional, fixed endcap duodenoscope has emerged as a primary target.

Design Limitations of Traditional, Fixed Endcap Duodenoscopes

There are currently three manufacturers that produce reusable duodenoscopes for use in the United States: Fujifilm, Olympus and Pentax. Traditional fixed endcap duodenoscopes produced by these companies require the user to perform high level disinfection reprocessing between uses. Several design limitations of fixed endcap duodenoscopes have been identified that can make manual and automated disinfection challenging including the presence of microscopic crevices in the elevator area, the use of adhesives to permanently affix an end cap to the distal tip and, in some duodenoscopes, the presence of an open elevator wire channel.

As mentioned above, duodenoscopes are uniquely complex in design due to the presence of the elevator mechanism. Microscopic crevices in the elevator such as the O-ring can be exposed to microbial fluid that cannot be readily accessed by a brush or disinfectant solution. Fixed endcap duodenoscopes also have a permanently glued plastic or rubber cap to the metal edges around the distal tip to prevent gastrointestinal trauma. However, when permanently fixed with an adhesive, the endcaps limit the accessibility to clean the recessed areas, including the underside of the elevator. Furthermore, repeated use and reprocessing can result in adhesive cracking and the development of additional microscopic crevices that are inaccessible to reprocessing. The limited access for cleaning leads to the development of microbial biofilms and persistent contamination of bacteria after standard reprocessing.

In addition to the elevator and fixed endcap, the elevator wire channel may also increase the risk of bacterial contamination. In order to control the elevator, a long thin wire extends from the scope handle to the distal tip. This wire is located within a narrow channel called the elevator wire channel. In some models of duodenoscopes, the channel is “open” allowing microbial containing fluids to enter the channel and thus requires flushing of the channel with disinfectant solutions. Currently only the Olympus TJF-160VF/F, the Olympus JF-140F, and the Olympus PJF160 have open elevator wire channels. Newer models including the Olympus TJF-Q180V (K143153, cleared in January 2016), Fujifilm ED530XT (K152257, cleared in July 2017) and Pentax ED-3490TK (K161222 cleared in February 2018, previously cleared in K092710) have made design changes to have a “closed” or sealed elevator wire channel. In these models, specific reprocessing of the elevator wire channel is unnecessary.

Innovative Duodenoscope Designs to Enhance Safety

In 2019, the FDA recommended transitioning to “duodenoscopes with innovative designs to enhance safety” reporting that the FDA “believes the best solution to reducing the risk of disease transmission by duodenoscopes is through innovative device designs that make reprocessing easier, more effective, or unnecessary.⁶” As of today, the FDA has cleared six duodenoscopes with disposable components that facilitate reprocessing and one protective end-sheath device including¹:

duodenoscope cleared under K201098)
Boston Scientific Corporation, EXALT Model D Single-Use Duodenoscope (fully disposable duodenoscope cleared under K193202)
Fujifilm Corporation, Duodenoscope model ED-580XT (disposable endcap duodenoscope cleared under K181745)
Olympus Medical Systems, Evis Exera III Duodenovideoscope Olympus TJF-Q190V (disposable endcap duodenoscope cleared under K193182)
Pentax Medical, Duodenoscope model ED34-i10T (disposable endcap duodenoscope cleared under K163614 and K181522)
Pentax Medical, Duodenoscope model ED34-i10T2 (disposable elevator duodenoscope cleared under K192245)
GI Scientific LLC, ScopeSeal (endoscopic contamination prevention sheath cleared under K183171)

Disposable End Caps

Novel duodenoscopes with disposable end caps combine the benefits of high-definition endoscopic visualization and scope responsiveness with improved visualization of and access to the distal end for manual cleaning and disinfection. Disposable end cap duodenoscopes have been produced by all three manufacturers, however the latest Pentax model ED34-i10T2 disposable end cap is the first and only to also include a disposable elevator. Although the ability to remove the end cap theoretically allows better access to the elevator mechanism to minimize bacterial contamination, data remains limited for demonstrating reduced risk of duodenoscope contamination. The Fujifilm ED-580XT duodenoscope with disposable endcap was compared for post-high level disinfection bacterial contamination (via rapid adenosine triphosphate, ATP) with the cap removed and with the cap maintained⁷. Removal of the cap (and allowing enhanced access for disinfection) resulted in reduced bacterial contamination and organic residue 37.0 % vs. 75.9 % (P < 0.001). Additional FDA mandated post-marketing surveillance culture studies are awaited to verify if the new disposable end cap designs will reduce bacterial contamination rates. Studies that assess risk of patient-to-patient infection transmission or provide comparison between disposable end cap duodenoscopes to traditional, fixed end cap duodenoscopes are also anticipated.

In addition to demonstrating efficacy in reducing bacterial contamination, further reports assessing endoscopist acceptance and safety are starting to emerge. The prospective multi-center DECap trial using the Pentax model ED34-i10T2 demonstrated comparable performance characteristics to traditional, fixed end duodenoscopes as rated by 97% of providers⁸. Further data on safety of these devices will also be critical as an FDA update in April 2020 noted 10 reports of device malfunctions, such as removable caps or ends falling off during ERCPs however, but no known instances of patient injury⁶.

End Sheath

In 2019, the FDA granted clearance to ScopeSeal (GI Scientific LLC, Arlington, Va, USA) for use with the Olympus TJF-Q180V duodenoscope. The ScopeSeal is a single use device that seals the distal end of traditional, fixed endcap duodenoscopes while preserving the optics and providing a plastic sheath (working channel extension) that fits into the biopsy channel. To date, only benchtop testing including leak testing and microbial challenges have been published9 with no in-vivo data currently available.

Single-Use Duodenoscope

Given the fact that it currently remains unclear if the disposable end caps will sufficiently reduce or eliminate the risk of bacterial contamination, some companies are pursuing fully disposable, single use duodenoscopes that will eliminate the need for reprocessing and along with it, any risk of infection transmission. Currently there are 2 disposable, single use duodenoscopes cleared by the FDA: the EXALT Model D (Boston Scientific Corporation, Marlborough, Mass, USA) and the aScope Duodeno (Ambu Inc, Columbia, Md, USA).

To date there have been three peer reviewed studies assessing the functionality of the EXALT Model D single use duodenoscope. Similar results were identified in two separate United States10 and European11 prospective consecutive case series – in which the EXALT Model D was successful in 96.7% and 95% of ERCP procedures, respectively, and overall physician satisfaction was rated 9 out of 10 by both US and European expert endoscopists.

There has been one randomized study that compared the performance of the EXALT Model D with reusable duodenoscopes in 98 patients with native papilla undergoing low complexity ERCP12. 95.8% were successfully cannulated with the single use duodenoscope and the median number of attempts to achieve successful cannulation was significantly lower for single-use cohort (2 vs 5, p=0.013). Although the overall technical performance and safety profile were similar between single-use and reusable duodenoscopes, the ease of passage into stomach, image quality, image stability, and air-water button functionality were rated as worse with the single use duodenoscope.

Conclusion

Although controversy remains on whether the FDA reported decline in duodenoscope associated infections is secondary to the success of mitigating practices including enhanced reprocessing measures, surveillance protocols, and routine maintenance or simply an issue of under reporting, it is now widely accepted by providers, the public and governmental agencies that the design of the duodenoscope must be further optimized for patient safety. The transition to disposable components and fully disposable duodenoscopes will require continued investigation and technical development balancing the ability to perform these complex procedures effectively (without trade-offs), while remaining cost effective and minimizing waste though recycling. Despite these challenges, continued innovation in duodenoscope design will ultimately achieve our goal of prioritizing patient safety and keeping our patients free from nosocomial infection.

Disclosures

Dr. Chapman has received consulting fees from Boston Scientific and Olympus Corporation. He has been a speaker for Apollo Endosurgery and Aspire Bariatrics. He has served as an advisor for BFKW, LLC, Erbe, and Nitinotes Surgical.

Christopher G. Chapman, MD

References

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