The Transdiaphragmatic Pressure Gradient and the Lower Esophageal Sphincter in the Pathophysiology of Gastroesophageal Reflux Disease: an Analysis of 500 Esophageal Function Tests

BACKGROUND

Gastroesophageal reflux disease (GERD) pathophysiology is multifactorial. Greater importance has been attributed to a defective lower esophageal sphincter (LES) in comparison to an altered transdiaphragmatic pressure gradient (TPG). This study aims to evaluate the role of the TPG and LES disfunction in GERD pathogenesis.

METHODS

Five hundred consecutive esophageal function tests from patients with clinically suspected GERD were reviewed. Patients were classified according to the pH monitoring in GERD positive or GERD negative. Abdominal pressure, thoracic pressure, TPG (abdominal-thoracic pressures), LES resting pressure (mid-respiratory, expiratory, and EGJ-CI), and LES retention pressure (LES resting pressure-TPG) were determined.

RESULTS

GERD was present in 296 (59%) individuals. GERD-positive patients were mostly males. LES resting pressure (by all parameters) and thoracic pressure were not different between groups. Abdominal pressure and TPG were higher in GERD-positive patients. LES retention pressure (by all parameters) was lower in GERD-positive patients. DeMeester score had a positive correlation with LES resting pressure, TPG, and LES retention pressure (by all parameters) but not with abdominal pressure and thoracic pressure.

CONCLUSIONS

LES valvular competency as measured by absolute resting pressure was not reliable to predict GERD; however, it was associated with GERD severity. Relative LES pressure (LES retention pressure) predicted GERD presence and severity, but no parameter showed superiority. TPG plays an important role in the pathophysiology of GERD since it is related to GERD presence and severity; still TPG is altered mostly based on a higher abdominal pressure.

The Role of the Transdiaphragmatic Pressure Gradient (TGP) in the Pathophysiology of Proximal Reflux

INTRODUCTION

An increased transdiaphragmatic pressure gradient (TGP) is a main element for distal gastroesophageal reflux disease (GERD). The role of TGP for proximal reflux is still unclear. This study aims to evaluate the presence, severity, and importance of proximal reflux in relationship to the TGP, comparing healthy volunteers, obese individuals, and patients with chronic obstructive pulmonary disease (COPD).

METHODS

We studied 114 individuals comprising 19 healthy lean volunteers, 47 obese individuals (mean body mass index 45 ± 7 kg/m²), and 48 patients with COPD. All patients underwent high-resolution manometry and dual-channel esophageal pH monitoring. Esophageal motility, thoracic pressure (TP), abdominal pressure (AP), TGP, DeMeester score, and % of proximal acid exposure time (pAET) were recorded.

RESULTS

Pathologic distal GERD was found in 0, 44, and 57% of the volunteers, obese, and COPD groups, respectively. pAET was similar among groups, only higher for obese individuals GERD + as compared to obese individuals GERD - and COPD GERD -. pAET did not correlate with any parameter in healthy individuals, but it correlated with AP in the obese, TP in the COPD individuals, and TGP and DeMeester score in both groups. When all individuals were analyzed as a total, pAET correlated with AP, TGP, and DeMeester score. DeMeester score was the only independent variable that correlated with pAET.

CONCLUSIONS

Our results show that (a) TGP is an important mechanism associated with distal esophageal acid exposure and this fact is linked with proximal acid exposure and (b) obesity and COPD both seem to be primary causes for GERD but not directly for proximal reflux.