Esophageal pressure topography plot of achalasia subtypes in the Chicago Classification

In each case, the 30 mmHg isobaric contour is highlighted in black and there is impaired EGJ relaxation evident by the EGJ never relaxing to less than 30 mmHg in any panel. With type I achalasia, there is minimal contractile activity between the UES and EGJ. Type II is defined by ≥20 percent of swallows (supine posture, 5 mL water) with panesophageal pressurization to ≥30 mmHg. With type III, there is ≥20 percent of swallows with either premature contractions or fragments of peristalsis.