Understanding esophageal pressure-area loop patterns in different diagnostic devices

The esophagogastric junction (EGJ) acts as a valve allowing swallowed materials to enter the stomach and prevent acid reflux. The relationship between the changes in area and intraluminal pressure, during opening and closing, have been used to quantify EGJ function. Previous studies in our group have identified pressure-area loops with positive slope using the clinical data from FLIP (an endoscopic device). This indicated that the EGJ opening involves both pressurization and active tone relaxation. However, High Resolution Impedance Manometry (HRIM) clinical data revealed loops with an 'L'-shaped pattern. In this case, the area increases initially (lumen opening) while pressure remains unchanged (static) and then pressure increases (contracting) while area decreases (lumen closing). This pattern distinguishes the loops from the ones using the FLIP data. This study aims to explain this apparent discrepancy. We developed a 1D model for an elastic tube. We simulated the two scenarios with the different boundary conditions. These results provide insights into how the loop patterns differ based on problem setup and should be an important consideration in diagnostics.