Hidden risks of endoscope storage cabinets

Methods of protecting endoscopes that have undergone high-level disinfection (HLD) or liquid chemical sterilization (LCS) from damage and contamination during storage have changed over the years. Not long ago, healthcare organizations stored patient-ready endoscopes in a variety of transport bins (sometimes in bags), in their original endoscope boxes with foam inserts, and upright in cabinets (with and without airflow). These methods were viewed as appropriate at the time and as a means of keeping processed endoscopes from becoming recontaminated and accidentally damaged. Over time, those processes changed and eventually moved to storage cabinets more appropriately designed for this purpose.  

  In March 2022, the Association for the Advancement of Medical Instrumentation (AAMI) released ANSI/AAMI ST91:2021 flexible and semi-rigid endoscope processing in health care facilities. This updated standard reflects current research and advancements in endoscope processing and recommends two types of storage cabinets for HLD- and LCS-processed endoscopes. The first is a drying cabinet specifically designed for flexible endoscope storage. ST91:2021, 11.2.2.1, defines endoscope drying cabinets as closed cabinets designed for storage of flexible endoscopes that circulate HEPA-filtered or instrument air through the cabinet and each endoscope channel at continuous positive pressure. The collective evidence shows that drying cabinets provide effective storage of flexible endoscopes to facilitate drying, decrease the potential for contamination, and provide protection from environmental contaminants (AORN, 2018 [367]). Within the drying cabinet, internal and external surfaces of the endoscope are intermittently or continuously dried, suppressing microbial growth. Studies related to the efficacy of drying cabinets compared with other methods of storage showed that drying cabinets effectively limited bacterial proliferation during storage of potentially incompletely dried endoscopes (Saliou, 2015 [284]; Perumpail, 2019 [254]).  A second storage option is closed cabinets that circulate HEPA-filtered or instrument air through the cabinet passively or via continuous positive pressure, but do not include forced air through endoscope channels. There is no clear consensus at this time among professional organizations regarding which type of cabinet is best; however, drying cabinets have been shown in scientific studies to reduce the risk of retained moisture and microbial contamination.  Endoscopes hung in HEPA-filtered storage cabinets that do not have drying capabilities should be dried thoroughly following manufacturers’ instructions for use (IFU) prior to storage or immediate reuse. Note: Per ST91, before storage, the channels of the HLD endoscope should be dry to help prevent bacterial growth and the formation of biofilm (see 8.2.5). If a drying cabinet is not used, dryness can be checked with dryness indicators.
Endoscopy departments and Sterile Processing professionals who routinely manage flexible and semi-rigid endoscopes and are considered subject matter experts may be surprised at what they may uncover when looking more closely at their processes. While building a digestive health program across three campuses of a large teaching hospital located in the western half of the U.S. the endoscopy unit director (Scott Pasternak) and I (David Taylor) recently reviewed the new ST91 updates and decided to do routine checks to validate our compliance with the new recommendations. We noticed our endoscopy endoscope cabinets at one of the campuses needed attention. Of the four storage cabinets in place, one cabinet door did not close properly and the fan systems in each cabinet were inoperable. The management team at that location was unaware of the situation and the employees had not reported any problems. After replacing the damaged door and installing new HEPA-filtered fans, we then investigated the storage cabinets at the other two campuses. Those cabinets appeared to be in order—until the unit director examined the insides of the fan unit and found an excessive amount of dust on the internal components and dust accumulation on the ceiling above the cabinets. This was perplexing because the cabinets are cleaned routinely (daily). Additionally, if dust was to accumulate, it would do so at the top external portion of the cabinet and not internally. After careful investigation, we discovered the filtered fans were installed improperly by the manufacturer, reversing the airflow from the floor through the cabinet’s grommets, past the stored endoscopes, and out the top. The manufacturer was notified of the problem, new fans with the appropriate HEPA filters were ordered and installed, and all endoscopes were reprocessed. Airflow now travels correctly, originating from the top of the cabinet, through the HEPA filter, past the endoscopes, and out the bottoms of the cabinet (through the grommets).  

Conclusion

It is easy to see why endoscope storage cabinets can be taken for granted and may be perceived as low risk; however, improper or inadequate maintenance and cleaning steps can eventually lead to serious problems. Leaders should take time to review their current processes and modify their practices as needed to comply with the latest guideline updates and/or changes to the IFU. ST91:2021 has added clarity and will help leaders ensure safe and proper endoscope processing and storage.

Original photo courtesy Bayhealth SPD, HPN's 2021 SPD of the Year, with affects added by generative AI.
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