Positional effects on gastric pressures and esophagogastric pressure gradients in patients with gastroesophageal reflux

Introduction Most mechanistic research on gastroesophageal reflux disease (GERD) focuses on LES pressure (LESP) and not the gastric-LESP gradient required to facilitate regurgitation. Our study focuses on gastric pressures (GP) during high-resolution manometry (HRM) and the magnitude and pressure gradient direction across the LES in patients with normal, upright, and supine GERD at baseline and with swallows.Methods Our study is a retrospective study evaluating patients who underwent HRM and 24 h impedance and categorized as patients with normal, upright, and supine esophageal acid exposure. Data was collected from the electronic medical record at our institution. GP was measured 2 centimeters (cm) below the LES at baseline and before and during swallows. Results were measured as means, medians, and standard deviations for continuous variables between the three groups.Results 42 patients were evaluated, including 22 normal (14F), 10 upright (8F), and 10 (8F) supine refluxers. Normal patients had a total acid exposure time of 1.4% (IQR 0.8-2.8%), upright had 6.4% (4.6-7.8%), and supine had 11.4% (7.8-21%). At baseline, the LESP was 35.59 mmHg, 31.97 mmHg, and 25.38 mmHg while the mean GP was 20.90 mmHg, 19.49 mmHg, and 21.80 mmHg, for normal, upright, and supine patients, respectively. No differences were seen in the mean GP during supine and upright swallow positions within any of the phenotypic groups, or when comparing differences in GP between upright vs. supine swallows across the three groups (Kruskal-Wallis P = 0.25). During upright swallows, the maximum GP was 15.8 mmHg (12.5-19.4), 17.2 (13.7-21.1), and 16.4 (14.1-22.7); LESP was 34.6 mmHg (IQR 27.4-47.2), 34.1 (25.3-36), and 21.7 (16.4-28.1); and integrative relaxation pressure (IRP) was 14.0 (10.6-17.3), 11.8 (10.6-15.5), and 8.8 (5.6-14.4) for the normal, upright and supine groups respectively. For normal patients, LESP consistently exceeded mean GP; during supine swallows, one patient in the normal group had median GP > LESP. For the upright group, 15/48 and 28/48 swallows had GP > IRP in the upright and supine positions, respectively. For the supine group, 24/48 and 32/48 swallows had GP > IRP upright and supine positions, respectively. During upright swallows, the median within-individual pressure gradient (IRP minus GP) was +6.2 mmHg (+3.9 to +11.3) for normal patients without reflux, +5.7 (+1.1 to +7.3) for patients with upright reflux, and + 1.4 (-0.3 to +5.0) for patients with supine reflux; during supine swallows, the same within-individual pressure gradient was +6.7 (+2.7 to +9.1), +4.0 (+2.4 to +6.3), and - 0.8 (-4.6 to +4.8) for the groups respectively.Conclusion This study demonstrates that the magnitude of LES-GP gradient decrease is related to the positional phenotype of gastroesophageal reflux with the lowest gradient seen in supine refluxers. It is This suggests that measuring the LES-GP gradient could be useful in characterizing patients with GERD.