Pneumatic dilation is an endoscopic therapy for achalasia. An air-filled cylinder-shaped balloon disrupts the muscle fibers of the lower esophageal sphincter, which is too tight in patients with achalasia. During an upper endoscopy, the endoscopist passes a catheter with a deflated balloon through the mouth and into the stomach. The balloon is centered over the lower esophageal sphincter and inflated with air.