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Gastroenterology. 2001 Jun;120(7):1599-606.

Simultaneous intraesophageal impedance and pH measurement of acid and nonacid gastroesophageal reflux: effect of omeprazole.

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Department of Medicine, Graduate Hospital, Philadelphia, Pennsylvania 19146, USA.



Nonacid reflux may explain symptoms in acid-suppressed patients. Simultaneous intraesophageal impedance and pH measurement was used to evaluate the frequencies of postprandial acid and nonacid reflux before and after omeprazole administration.


Twelve heartburn patients underwent two 2-hour studies of intraesophageal impedance and pH in the right lateral decubitus position after a refluxogenic meal; session 1 without medication, session 2 after 7 days of omeprazole twice daily. Acid and nonacid reflux were quantified.


Two hundred seventeen reflux episodes were detected before and 261 after omeprazole treatment (P > 0.05). Percentage of acid reflux decreased (from 45% to 3%, P = 0.02) and nonacid reflux increased (from 55% to 97%, P = 0.03) after omeprazole. Heartburn and acid taste were more commonly linked to acid reflux but were also produced by nonacid reflux. Regurgitation was reported equally in acid and nonacid reflux. Delta(pH) > 1 did not help predict the presence of symptoms during nonacid reflux.


During treatment with omeprazole, postprandial reflux becomes predominantly nonacid. Symptoms are more common with acid reflux but are also produced by nonacid reflux. Simultaneous intraesophageal impedance and pH may be useful in evaluating the role of nonacid reflux in symptoms that persist despite adequate acid suppression.

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