Figure 4: Multichannel intraluminal impedance (MII) patterns for bolus transport. (a) Normal bolus transport. A decrease in basal impedance measurement and subsequent return to basal levels is noticed in all channels (proximal, medium, and distal). (b) Abnormal bolus transport. All channels display a low basal impedance level unchanged by swallow. This may be explained by fluid repletion of the esophagus? It is a common pattern in achalasia patients. (c) Abnormal bolus transport. The proximal channel shows a normal bolus propagation. More distal channels display a retention of the bolus distally. This may be explained by outflow resistance at the esophagogastric junction. (d) Abnormal bolus transport. Retention of the bolus is noticed in the midesophagus. This may be explained by segmental aperistalsis.