key: cord-0759343-6s33o874 authors: Dumonceau, Jean-Marc title: Gas leakage from the biopsy valve: Does it matter in the era of COVID-19? date: 2021-02-19 journal: Endosc Int Open DOI: 10.1055/a-1339-1259 sha: 6d239160423eb1f8904ffdb65c8c23f18dfd548f doc_id: 759343 cord_uid: 6s33o874 nan analysis, half the stool samples from patients with COVID-19 tested positive for virus RNA; worryingly, two-thirds of these patients had virus RNA detected even after respiratory specimens tested negative [9] . Data on the risk of SARS-CoV-2 transmission to health care workers in gastrointestinal endoscopy are contradictory. In two studies from Italy and the U.K. that included a total of 60 endoscopy centers, fewer than 4 % of health care workers tested positive for SARS-CoV-2. Of note, almost 90 % of infections occurred before the introduction of safety measures, such as use of personal protective equipment (PPE) and case selection/reduction in gastrointestinal endoscopy [10, 11] . In contrast, a worldwide survey found that one-third of 163 endoscopy centers reported positive cases of SARS-CoV-2 infection among their healthcare workers despite the large use of PPE [12] . In this context, the research on previously unreported potential pathways of contamination during gastrointestinal endoscopy presented in the current issue of Endoscopy International Open may be critical [13] . The experiment design was simple: Urakawa et al. inserted, ex vivo, a colonoscope in a porcine rectal segment, then inflated the bowel, submerged the colonoscope in a water bath, and finally they passed various instruments through the biopsy valve in the working channel of the endoscope. During these maneuvers, gas frequently leaked at the level of the biopsy valve at low pressures and at the level of the handle of various endoscopy instruments, including snares, clips, and knifes, at higher pressures. Future work should investigate several points: ▪ The volume of the gas leak. The dead space in the working channel of the endoscope used by the authors is approximately 9 cm 3 . These 9 cm 3 are filled with air from the room and are the first ones to escape through the biopsy valve. These are likely irrelevant in terms of contamination. ▪ Intraluminal pressures measured during standard endoscopy only should be used. In the current study, inflation pressures up to 75 mm Hg were used in some of the experiments. Although an "average of maximum intraluminal pressure" > 100 mm Hg was reported in a study cited by Urakawa et al., this pressure corresponded to contractions of the circumferential circular muscles of the colon haustrations on a sensor (no endoscopy was performed in that study) [14] . Pressures of 8 to 16 mm Hg are more commonly used for endoscopy [15] . ▪ Finally, the significance of these gas leaks, as assessed by the presence of aerosols or the detection of viral RNA in it, should be investigated. Various instruments such as particle sizers may be used to detect particles in aerosols and measure some of their characteristics, such as their number, concentration, and size distribution during endoscopic procedures. Knowing if aerosols are generated when introducing an endoscopy instrument through the biopsy valve is important because all of the precautions described to reduce the dispersion of aerosols during upper gastrointestinal endoscopy consist of interposing a barrier between the patient and the environment but none has taken the endoscope into account. Proposed barriers consist of fabric or masks with a hole applied to the patient's face [16, 17] , a transparent plastic bag or plexiglass box placed around the patient's face [18, 19] , or a sheet covering the whole patient and stretcher down to the ground [20] . If the authors' findings are confirmed to be significant in terms of contamination, they have the potential to impact the design of endoscopy accessories. Currently, to mitigate the risks, one could: (1) choose biopsy valves and endoscopy instruments that tend to leak less; (2) insert/remove endoscopy instruments quickly, at a low inflation pressure, without changing the insertion angle of the device; and (3) place a barrier with a hole on the biopsy valve when inserting an endoscopy instrument. For the time being, triage of patients for urgent procedures, pre-endoscopy patient screening based on symptoms and/or testing for the presence of SARS-CoV-2 (point-of-care tests), segregation of clean and contaminated zones in endoscopy suites, physical distancing, rigorous sanitization procedures, and use of PPE remain the cornerstones for prevention of contamination. 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