In assessment of distal esophageal pH, the sensor is placed 5 cm above upper border of the lower esophageal sphincter (LES) determined by esophageal manometry. To measure proximal esophageal acid exposure the second sensor is placed 1-5 below the lower border of the upper esophageal sphincter (UES). The Bravo pH capsule is placed either transnasally based on manometric measurements, or following endoscopy.