What is Ambulatory 24 hour pH monitoring?
Ambulatory PH monitoring measures the acid that refluxes back up from the stomach. A very thin tube is inserted up through the nostril and then down the throat and esophagus until it reaches just above the stomach. The tube has a very small probe at the end that will register any acids that are refluxed from the stomach. An x-ray is taken to make sure that the probe has been positioned correctly. The other end of the thin tube is attached to a small computer (small black box) for 12 or 24 hours. During this period you are given a diary sheet to complete, on which you should record the time of each activity that takes place, basically a running history.
PH Capsule: This is a new type of pH probe which requires no tube though the nose. It is a sensor that is attached to the lining of the esophagus, with an endoscope. Often this procedure is carried out at the same time as having an endoscopy (upper GI) performed. The pH sensor sends signals to a portable computer which collects the data about the acid exposure over the usual 24 hrs. There is no removal procedure, the sensor will slowly detach itself from the esophagus with time and is then passed though a normal stool
Impedance Study: Similar to a standard pH test, but with two probes. One sits in the stomach and the other just above the stomach. The advantage of the dual sensor is that it can detect both acid and alkaline reflux travels. The tube is inserted through the nostril (this can be placed whilst still sedated after an endoscopy), and the other end is attached to a small computer, no bigger than a Walkman