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. 2020 May 21;70(1):30–39. doi: 10.1136/gutjnl-2020-320772

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© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY. Published by BMJ.

This is an open access article distributed in accordance with the Creative Commons Attribution 4.0 Unported (CC BY 4.0) license, which permits others to copy, redistribute, remix, transform and build upon this work for any purpose, provided the original work is properly cited, a link to the licence is given, and indication of whether changes were made. See: https://creativecommons.org/licenses/by/4.0/.

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Oesophageal acidification patterns observed during pH-impedance monitoring. (A) Acid reflux with normal clearance: rapid pH drop to below 4, drop rate ≥1 pH unit per second, lasting between 10 s and 5 min. (B) Acid reflux with delayed clearance: rapid pH drop to below 4, drop rate ≥1 pH unit per second, lasting longer than 5 min. (C) Acid fermentation: slow pH drop to below 4, drop rate <1 pH unit per minute, lasting longer than 5 min. (D) Stasis of recently ingested acidic food or drink: pH drop to below 4 during meal/drink, pH below 4 persisting longer than 5 min after meal/drink. The pink-coloured area indicates meal/drink ingestion. (E) Unclassified: pH drop to below 4 not meeting criteria for any of the acid patterns described above.