Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.
Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
Esophageal pH (pH is a measure of the acidity or alkalinity of a solution) monitoring is a procedure for measuring the reflux (regurgitation or backwash) of acid from the stomach into the esophagus that occurs in gastroesophageal reflux disease (GERD).
When is esophageal pH monitoring used?
Esophageal pH monitoring is used to diagnose GERD effects, to determine the effectiveness of medications that are given to prevent acid reflux, and to determine if episodes of acidic reflux are causing episodes of chest pain. Monitoring esophageal pH also can be used to determine if acid is reaching the pharynx (lower throat) and is possibly responsible for such symptoms as
cough, hoarseness, and sore throat.
How is esophageal pH monitoring performed?
Esophageal pH monitoring is performed by passing a thin plastic catheter a sixteenth of an
inch in diameter through one nostril, down the back of the throat, and into the
esophagus as the patient swallows. The tip of the catheter contains a sensor
that senses acid. The sensor is positioned in the esophagus so that it is just
above the lower esophageal sphincter, a specialized area of esophageal muscle
that lies at the junction of the esophagus and stomach and prevents acid from
refluxing back up into the esophagus. In this position the sensor records each
reflux of acid. The catheter protruding from the nose is connected to a recorder
that registers each reflux of acid.
The patient is sent home with the catheter
and recorder in place and returns the next day to have them removed. During the
24 hours that the catheter is in place, the patient goes about his or her usual
activities, for example, eating, sleeping, and working. Meals, periods of sleep, and symptoms are
recorded by the patient in a diary and/or by pushing buttons on the
recorder. After the catheter is removed, the recorder is attached to
a computer so that the data it has gathered can be downloaded into
the computer where it is analyzed and put into graphic form. The procedure can
be modified by placing the sensor in the upper esophagus or pharynx to determine
if refluxed acid is reaching the pharynx.
The most recently-developed device for monitoring esophageal pH uses a capsule.
The capsule contains an acid sensing probe, a battery, and a transmitter. The probe monitors the acid in
the esophagus and transmits the information to a recorder that is worn by the patient on a belt. The capsule
is introduced into the esophagus on a catheter through the nose or mouth and is attached to the lining of the
esophagus with a clip. The catheter then is detached from the capsule and removed. Thus, there is no catheter
protruding from the nose. The capsule transmits for two days or three days, and then the battery dies. Five to seven days later,
the capsule falls off of the esophageal lining and is passed in the stool as the capsule is not reusable.
The advantages of the capsule device
are related to the absence of a catheter connecting the probe to the recorder. There is greater comfort without a
catheter in the back of the throat, and patients are more likely to go to work and do more
of their normal activities without feeling self-conscious about the appearance
of the catheter to others. The disadvantages of the capsule are that it cannot
be used in the pharynx (where it would be impossibly uncomfortable) and, so far,
it has not been used in the stomach.