Esophageal pH monitoring is the current
gold standard
A gold standard is a monetary system in which the standard economic unit of account is based on a fixed quantity of gold. The gold standard was the basis for the international monetary system from the 1870s to the early 1920s, and from the l ...
for diagnosis of
gastroesophageal reflux disease
Gastroesophageal reflux disease (GERD) or gastro-oesophageal reflux disease (GORD) is one of the upper gastrointestinal chronic diseases where stomach content persistently and regularly flows up into the esophagus, resulting in symptoms and/ ...
(GERD). It provides direct physiologic measurement of acid in the
esophagus
The esophagus ( American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to ...
and is the most objective method to document reflux disease, assess the severity of the disease and monitor the response of the disease to medical or surgical treatment. It can also be used in diagnosing
laryngopharyngeal reflux
Laryngopharyngeal reflux (LPR) is the retrograde flow of gastric contents into the larynx, oropharynx and/or the nasopharynx. LPR causes respiratory symptoms such as cough and wheezing and is often associated with head and neck complaints such a ...
.
Background
The importance of refluxed gastric contents in the
pathogenesis
Pathogenesis is the process by which a disease or disorder develops. It can include factors which contribute not only to the onset of the disease or disorder, but also to its progression and maintenance. The word comes from Greek πάθος ''pat ...
of
GERD Gerd or GERD may refer to:
* Gerd (given name), a list of people with the given name or nickname
* Gerd (moon), a moon of Saturn
* Gerd Island, South Orkney Islands, Antarctica
* Gastroesophageal reflux disease, a chronic symptom of mucosal damage ...
was emphasized by Winkelstein who introduced the term "
peptic esophagitis
Esophagitis, also spelled oesophagitis, is a disease characterized by inflammation of the esophagus. The esophagus is a tube composed of a mucosal lining, and longitudinal and circular smooth muscle fibers. It connects the pharynx to the stomach; s ...
" and by Bernstein and Baker who reported the symptom of
heartburn
Heartburn, also known as pyrosis, cardialgia or acid indigestion, is a burning sensation in the central chest or upper central abdomen. Heartburn is usually due to regurgitation of gastric acid (gastric reflux) into the esophagus. It is the m ...
following instillation of
hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
in the distal
esophagus
The esophagus ( American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to ...
in what was then became known as the
acid perfusion test
Acid perfusion test, also called the Bernstein test, is a test done to reproduce the pain when the lower esophagus is irrigated with an acid solution in people with GERD (gastroesophageal reflux disease).
There will be a negative result in normal ...
. Formal measurement of
acid in the
esophagus
The esophagus ( American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to ...
was first described in 1960 by Tuttle. He used a glass
pH probe to map the gastroesophageal pH gradient, and demonstrated a sharp gradient in normal subjects and a gradual, sloping gradient in patients with esophagitis. Four years later, Miller used an indwelling esophageal pH electrode to continuously measure esophageal and gastric pH for a period up to 12 hours. This technique required that the patient keep their hands immersed in saline to serve as a reference. Prolonged monitoring became feasible in 1974 when Johnson and
DeMeester developed a dependable external reference electrode. Using this technique to monitor esophageal acid exposure patients for periods up to 24 hours, DeMeester and Johnson were able to identify the most important parameters of esophageal acid exposure, and they developed a composite pH score to quantify gastroesophageal reflux. The initial 24-hour pH studies required hospitalization until the introduction of
microcircuits in the 1980s that allowed portable esophageal pH monitoring in an outpatient setting.
Clinical application
Gastroesophageal reflux disease
Gastroesophageal reflux disease (GERD) or gastro-oesophageal reflux disease (GORD) is one of the upper gastrointestinal chronic diseases where stomach content persistently and regularly flows up into the esophagus, resulting in symptoms and/ ...
(GERD) is a common disease in western countries. In the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
, 7% of the population experiences
heartburn
Heartburn, also known as pyrosis, cardialgia or acid indigestion, is a burning sensation in the central chest or upper central abdomen. Heartburn is usually due to regurgitation of gastric acid (gastric reflux) into the esophagus. It is the m ...
daily and 44% at least once a month.
Heartburn
Heartburn, also known as pyrosis, cardialgia or acid indigestion, is a burning sensation in the central chest or upper central abdomen. Heartburn is usually due to regurgitation of gastric acid (gastric reflux) into the esophagus. It is the m ...
occurs when esophageal mucosa is exposed to the acidic gastric content, but the complaint of
heartburn
Heartburn, also known as pyrosis, cardialgia or acid indigestion, is a burning sensation in the central chest or upper central abdomen. Heartburn is usually due to regurgitation of gastric acid (gastric reflux) into the esophagus. It is the m ...
is not always a reliable guide to the presence of acid reflux in the esophagus. Further, only half of the patients with increased esophageal acid exposure will have
esophagitis
Esophagitis, also spelled oesophagitis, is a disease characterized by inflammation of the esophagus. The esophagus is a tube composed of a mucosal lining, and longitudinal and circular smooth muscle fibers. It connects the pharynx to the stomach; s ...
. Therefore, the diagnosis of
gastroesophageal reflux disease
Gastroesophageal reflux disease (GERD) or gastro-oesophageal reflux disease (GORD) is one of the upper gastrointestinal chronic diseases where stomach content persistently and regularly flows up into the esophagus, resulting in symptoms and/ ...
(GERD) on the basis of symptoms or endoscopic findings is problematic.
Although there remains no gold standard for the diagnosis of GERD, ambulatory esophageal
pH monitoring can provide data to guide further evaluation and treatment of patients with GERD-associated symptoms. In the past, an indwelling nasoesophageal
catheter
In medicine, a catheter (/ˈkæθətər/) is a thin tubing (material), tube made from medical grade materials serving a broad range of functions. Catheters are medical devices that can be inserted in the body to treat diseases or perform a surgi ...
was the only way to measure esophageal acid exposure. Because this method is associated with
nasal and
pharyngeal discomfort and
rhinorrhea
Rhinorrhea, rhinorrhoea, or informally runny nose is the free discharge of a thin mucus fluid from the nose; it is a common condition. It is a common symptom of allergies ( hay fever) or certain viral infections, such as the common cold or CO ...
, patients may have limited their activity and become more sedentary during the monitored period. This may have resulted in less acid reflux and a false negative test. A catheter-free radio
telemetric
Telemetry is the in situ collection of measurements or other data at remote points and their automatic transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Greek roots ''tele'', "remote", and ...
system allows a longer period of monitoring and may be better tolerated.
Techniques
Esophageal pH monitoring is currently performed using one of the following three techniques:
# Single sensor pH monitoring using a pH catheter
# Dual sensor pH monitoring using a pH catheter
# Wireless pH monitoring using Bravo pH capsule or OMOM pH monitoring capsule
The duration of the test is 24 hours in the first and second techniques and 48 hours for the Bravo capsule or more (96 hours) for OMOM capsule.
pH sensor location and probe placement
In assessment of distal esophageal pH, the sensor is placed 5 cm above the upper border of the
lower esophageal sphincter
The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the ...
(LES) determined by
esophageal manometry
An esophageal motility study (EMS) or esophageal manometry is a test to assess motor function of the upper esophageal sphincter (UES), esophageal body and lower esophageal sphincter (LES).
Indications
An EMS is typically done to evaluate suspect ...
. To measure
proximal
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...
esophageal acid exposure, the second sensor is placed 1-5 below the lower border of the
upper esophageal sphincter
The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the ...
(UES). The Bravo pH capsule is placed either transnasally based on manometric measurements, or following
endoscopy
An endoscopy is a procedure used in medicine to look inside the body. The endoscopy procedure uses an endoscope to examine the interior of a hollow organ or cavity of the body. Unlike many other medical imaging techniques, endoscopes are inse ...
. In transnasal placement, the capsule is placed 5 cm above the upper border of the LES, and in endoscopic placement 6 cm above
the gastroesophageal junction. The same applies to OMOM pH monitoring capsule.
Components of esophageal pH monitoring
A reflux episode is defined as esophageal pH drops below four. Esophageal pH monitoring is performed for 24 or 48 hours and at the end of recording, a patient's tracing is analyzed and the results are expressed using six standard components. Of these 6 parameters, a pH score called Composite pH Score or DeMeester Score has been calculated, which is a global measure of esophageal acid exposure. A Demeester score > 14.72 indicates reflux.
Multichannel intraluminal impedance (MII) pH monitoring
The widespread prescription of
proton pump inhibitors
Proton-pump inhibitors (PPIs) are a class of medications that cause a profound and prolonged reduction of stomach acid production. They do so by irreversibly inhibiting the stomach's H+/K+ ATPase proton pump.
They are the most potent inhibitor ...
(PPI) by primary care physicians has resulted in a change in pattern of GERD in patients who use these medications. Quite often gastroenterologist and foregut surgeons receive consultations to assess patients with persistent reflux symptoms despite the fact that patients is on acid suppression medications. This is due to the fact that symptoms of these patients are the results of weak acid or non-acid reflux.
In 1991 Silny was the first investigator who described Multichannel Intraluminal Impedance (MII), a technique which detects intraesophageal bolus transport. This method is based on measuring the resistance to alternating current (i.e., impedance) of the content of the esophageal lumen. MII- pH monitoring was then developed by several clinical investigators. The clinical application of this technique is mainly in GERD patients who have persistent symptoms despite medical therapy.
pH monitoring in laryngopharyngeal reflux
Retrograde flow of gastric contents to the upper aerodigestive tract causes a variety of symptoms such as
cough
A cough is a sudden expulsion of air through the large breathing passages that can help clear them of fluids, irritants, foreign particles and microbes. As a protective reflex, coughing can be repetitive with the cough reflex following three ph ...
,
asthma
Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, co ...
and
hoarseness
A hoarse voice, also known as dysphonia or hoarseness, is when the voice involuntarily sounds breathy, raspy, or strained, or is softer in volume or lower in pitch. A hoarse voice, can be associated with a feeling of unease or scratchiness in the ...
. These respiratory manifestations of the reflux disease are commonly called
laryngopharyngeal reflux
Laryngopharyngeal reflux (LPR) is the retrograde flow of gastric contents into the larynx, oropharynx and/or the nasopharynx. LPR causes respiratory symptoms such as cough and wheezing and is often associated with head and neck complaints such a ...
(LPR) or extraesophegeal reflux disease (EERD). Distal esophageal pH monitoring has been used as an objective test to establish reflux as the cause of the atypical reflux symptoms, but its role in causally associating patients' symptoms to GERD is controversial. In an effort to improve diagnostic accuracy of testing, a catheter with two pH sensors has been used to measure the degree of esophageal acid exposure in both distal and proximal esophagus. The ideal location for pH measurement to confirm the diagnosis of the laryngopharyngeal reflux is the
pharynx
The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its st ...
and new studies have focused on the development of a new pH sensor which can function in the challenging environment of the oropharynx.
See also
*
Heidelberg test
References
{{Digestive system procedures
Diagnostic gastroenterology
Medical monitoring