Figure 3.

Evaluation of esophagogastric junction (EGJ) function during swallowing. The top panel is an esophageal pressure topography (EPT) of normal EGJ function following a wet swallow. As you can see pressure at the EGJ normally drops ahead of the advancing peristaltic pressure wave. It is not a direct measure of lower esophageal sphincter (LES) relaxation, but pressure in the swallowed bolus as it opens and traverses the EGJ. Esophagogastric junction function during swallowing is determined by a measurement called the 4-second integrated relaxation (residual) pressure (IRP). It is determined within a "deglutitive relaxation window," a window that straddles the EGJ and stretches for 10 seconds after opening of the upper esophageal sphincter (UES) (black brackets). This is the spatial and temporal domain within which EGJ function is evaluated. A tool called the eSleeve™ is used to set the spatial extent of the window, which is 6 cm in length by default. The eSleeve determines the highest pressure within the deglutitve relaxation window at each point in time. The 4-second IRP algorithm takes these pressures and averages the lowest of them over four continuous or discontinuous seconds (white boxes). This discontinuous measurement avoids inclusion of elevated pressures produced by contraction of the crural diaphragm (*) or cardiovascular structures in the calculation of IRP. The lower panel is an example of an abnormal IRP seen in achalasia. In this case, pressure at the EGJ results from failed LES relaxation and pressurization of the swallowed bolus above the LES (**).