Gastroesophageal Pressure Gradients in Gastroesophageal Reflux Disease: Relations With Hiatal Hernia, Body Mass Index, and Esophageal Acid Exposure

OBJECTIVES The roles of intragastric pressure (IGP), intraesophageal pressure (IEP), gastroesophageal pressure gradient (GEPG), and body mass index (BMI) in the pathophysiology of gastroesophageal reflux disease (GERD) and hiatal hernia (HH) are only partly understood. METHODS In total, 149 GERD patients underwent stationary esophageal manometry, 24-h pH-metry, and endoscopy. RESULTS One hundred three patients had HH. Linear regression analysis showed that each kilogram per square meter of BMI caused a 0.047-kPa increase in inspiratory IGP (95% confidence interval [CI] 0.026–0.067) and a 0.031-kPa increase in inspiratory GEPG (95% CI 0.007–0.055). Each kilogram per square meter of BMI caused expiratory IGP to increase with 0.043 kPa (95% CI 0.025–0.060) and expiratory IEP with 0.052 kPa (95% CI 0.027–0.077). Each added year of age caused inspiratory IEP to decrease by 0.008 kPa (95% CI –0.015–−0.001) and inspiratory GEPG to increase by 0.008 kPa (95% CI 0.000–0.015). In binary logistic regression analysis, HH was predicted by inspiratory and expiratory IGP (odds ratio [OR] 2.93 and 2.62, respectively), inspiratory and expiratory GEPG (OR 3.19 and 2.68, respectively), and BMI (OR 1.72/5 kg/m2). In linear regression analysis, HH caused an average 5.09% increase in supine acid exposure (95% CI 0.96–9.22) and an average 3.46% increase in total acid exposure (95% CI 0.82–6.09). Each added year of age caused an average 0.10% increase in upright acid exposure and a 0.09% increase in total acid exposure (95% CI 0.00–0.20 and 0.00–0.18). CONCLUSIONS BMI predicts IGP, inspiratory GEPG, and expiratory IEP. Age predicts inspiratory IEP and GEPG. Presence of HH is predicted by IGP, GEPG, and BMI. GEPG is not associated with acid exposure.