pH Tests

Intra-esophageal testing is an excellent way to detect episodes of Gastro Esophageal Reflux (GERD) when stomach acid flows back up into the esophagus. We can measure when reflux occurs and under what circumstances (i.e. only after meals or when lying down), and how often.

The device is a long thin plastic tube which is sensitive to changes in acid concentration. It is connected to a notebook-sized data collection device, which is usually attached to the patient's belt. The tube remains in place for up to 24 hours.

Indications of Probe Testing

Probe testing can be used to:

  1. assess the degree of acid reflux into the esophagus;
  2. assess whether acid in the esophagus is a cause of a patient's symptoms;
  3. assess whether acid reflux is a cause of problems such as hoarse voice, wheezing, or asthma;
  4. determine whether a medication to suppress acidity is working adequately.


The patient is asked not to ingest anything for 4–8 hours. Usually anti-reflux medications are discontinued for 3‐7 days.


On arrival (or immediately after esophageal manometry testing), the pH probe is placed via the nose, so that the tip is 5cm above the lower esophageal sphincter (which separates the esophagus from the stomach). We frequently use a tube with two sensors, especially when trying to evaluate whether a patient's hoarse voice or breathing problems are due to reflux.

Once the position of the probe is satisfactory, it is taped to the nose and connected to the recording device. The patient is given a diary to record certain events which may affect reflux such as position, meals or symptoms. The patient is instructed to resume usual activities and to avoid getting the device wet. We prefer avoidance of very acidic foods (i.e. fruit, fruit juice, tomato-based foods, and sauerkraut) as they can occasionally give false readings. Smoking can be continued.

The patient returns to our unit after 16 to 24 hours, and the tube is removed. The recording device is downloaded onto a computer. The results are analyzed and correlated with the patient's diary. The results indicate the severity and associations of reflux, and help decide appropriate treatment. The test is simple and entirely safe.