Esophageal motility refers to contractions in the esophagus. Electric impedance from the body volume conductor such as bolus, organ wall, and body fluids can be recorded through electrodes on the catheter. Each volume conductor has their own characteristic value and phase of contraction waves. Impedance changes as logarithmic function of the bolus thickness changes. As the conductive bolus travels through, the electricity travels between two adjacent electrodes. The electrical signal between two electrodes gives information about material through which the electricity travels. This allows us to evaluate functional stages of contraction waves in the esophagus.