24-hour pH monitoring

24-hour pH monitoring is a test to measure how much acid is in the esophagus. The esophagus is the tube that carries food from the mouth to the stomach. The "pH" of a substance is a measurement of how acidic it is.

The test involves putting a small tube (catheter) through the nose and down the throat. One end of the tube sits in the esophagus. The other end is attached to a small device that can be worn around the waist or over the shoulder. The tube is taped to parts of the face to keep it from getting in the way during daily activities like eating.