Esophageal pH Monitoring
Encyclopedia
Esophageal pH monitoring is the current gold standard for diagnosis of gastroesophageal reflux disease
(GERD). It provides direct physiologic measurement of acid in the esophagus
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
.
was emphasized by Winkelstein who introduced the term “peptic esophagitis” and by Bernstein and Baker who reported the symptom of heartburn
following instillation of hydrochloric acid in the distal esophagus
. Formal measurement of acid
in the esophagus
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.
(GERD) is a common disease in western countries. In the United States
, 7% of the population experiences heartburn
daily and 44% at least once a month . Heartburn
occurs when esophageal mucosa is exposed to the acidic gastric content, but the complaint of heartburn
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
. Therefore, the diagnosis of gastroesophageal reflux disease
(GERD) on the basis of symptoms or endoscopic findings is problematic.
Ambulatory esophageal pH
monitoring is now the gold standard for the diagnosis of gastroesophageal reflux disease.
In the past, an indwelling nasoesophageal catheter was the only way to measure esophageal acid exposure. Because this method is associated with nasal and pharyngeal discomfort and rhinorrhea, 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 system allows a longer period of monitoring and may be better tolerated.
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.
(UES). The Bravo pH capsule is placed either transnasally based on manometric measurements, or following endoscopy
. In transnasal placement the capsule is placed 5 cm above upper border of the LES, and in endoscopic placement 6 cm above gastroesophageal junction. The same applies to OMOM pH monitoring capsule.
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.
, asthma
and hoarseness. These respiratory manifestations of the reflux disease commonly called laryngopharyngeal reflux
(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 senors 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 pharynx
and new studies has focused on the development of a new pH sensor which can function in the challenging environment of the oropharynx.
Gastroesophageal reflux disease
Gastroesophageal reflux disease , gastro-oesophageal reflux disease , gastric reflux disease, or acid reflux disease is chronic symptoms or mucosal damage caused by stomach acid coming up from the stomach into the esophagus...
(GERD). It provides direct physiologic measurement of acid in the esophagus
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
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
Laryngopharyngeal reflux , also extraesophageal reflux disease refers to retrograde flow of gastric contents to the upper aero-digestive tract, which causes a variety of symptoms, such as cough, hoarseness, and asthma, among others.Although heartburn is a primary symptom among people with...
.
Background
The importance of refluxed gastric contents in the pathogenesis of GERDGerd
In Norse mythology, Gerðr is a jötunn, goddess, and the wife of the god Freyr. Gerðr is attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources; the Prose Edda and Heimskringla, written in the 13th century by Snorri Sturluson; and in the poetry of skalds...
was emphasized by Winkelstein who introduced the term “peptic esophagitis” and by Bernstein and Baker who reported the symptom of heartburn
Heartburn
Heartburn, also known as pyrosis or acid indigestion is a burning sensation in the chest, just behind the breastbone or in the epigastrium...
following instillation of hydrochloric acid in the distal esophagus
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
. Formal measurement of acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
in the esophagus
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
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 DiseaseGastroesophageal reflux disease
Gastroesophageal reflux disease , gastro-oesophageal reflux disease , gastric reflux disease, or acid reflux disease is chronic symptoms or mucosal damage caused by stomach acid coming up from the stomach into the esophagus...
(GERD) is a common disease in western countries. In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, 7% of the population experiences heartburn
Heartburn
Heartburn, also known as pyrosis or acid indigestion is a burning sensation in the chest, just behind the breastbone or in the epigastrium...
daily and 44% at least once a month . Heartburn
Heartburn
Heartburn, also known as pyrosis or acid indigestion is a burning sensation in the chest, just behind the breastbone or in the epigastrium...
occurs when esophageal mucosa is exposed to the acidic gastric content, but the complaint of heartburn
Heartburn
Heartburn, also known as pyrosis or acid indigestion is a burning sensation in the chest, just behind the breastbone or in the epigastrium...
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
Esophagitis is inflammation of the esophagus. It may be acute or chronic. The acute esophagitis can be catarrhal or phlegmonous, whereas the chronic esophagitis may be hypertrophic or atrophic.-Infectious:...
. Therefore, the diagnosis of gastroesophageal reflux disease
Gastroesophageal reflux disease
Gastroesophageal reflux disease , gastro-oesophageal reflux disease , gastric reflux disease, or acid reflux disease is chronic symptoms or mucosal damage caused by stomach acid coming up from the stomach into the esophagus...
(GERD) on the basis of symptoms or endoscopic findings is problematic.
Ambulatory esophageal pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
monitoring is now the gold standard for the diagnosis of gastroesophageal reflux disease.
In the past, an indwelling nasoesophageal catheter was the only way to measure esophageal acid exposure. Because this method is associated with nasal and pharyngeal discomfort and rhinorrhea, 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 system allows a longer period of monitoring and may be better tolerated.
Different 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 upper border of the lower esophageal sphincter (LES) determined by esophageal manometry. To measure proximal esophageal acid exposure the second sensor is placed 1-5 below the lower border of the upper esophageal sphincterUpper esophageal sphincter
The upper esophageal sphincter refers to the superior portion of the esophagus.Unlike the lower esophageal sphincter, it consists of striated muscle and yet, is not under conscious control. Opening of the UES is triggered by the swallow reflex...
(UES). The Bravo pH capsule is placed either transnasally based on manometric measurements, or following endoscopy
Endoscopy
Endoscopy means looking inside and typically refers to looking inside the body for medical reasons using an endoscope , an instrument used to examine the interior of a hollow organ or cavity of the body. Unlike most other medical imaging devices, endoscopes are inserted directly into the organ...
. In transnasal placement the capsule is placed 5 cm above upper border of the LES, and in endoscopic placement 6 cm above gastroesophageal junction. The same applies to OMOM pH monitoring capsule.
Components of esophageal pH monitoring
A reflux episode is defined as esophageal pH drop below four. Esophageal pH monitoring is performed for 24 or 48 hours and at the end of recording, patients 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.| Components of 24-h Esophageal pH Monitoring |
|---|
| Percent total time pH < 4 |
| Percent Upright time pH < 4 |
| Percent Supine time pH < 4 |
| Number of reflux episodes |
| Number of reflux episodes ≥ 5 min |
| Longest reflux episode (minutes) |
Multichannel intraluminal impedance (MII) pH monitoring
The widespread prescription of proton pump inhibitors (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 coughCough
A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...
, asthma
Asthma
Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
and hoarseness. These respiratory manifestations of the reflux disease commonly called laryngopharyngeal reflux
Laryngopharyngeal reflux
Laryngopharyngeal reflux , also extraesophageal reflux disease refers to retrograde flow of gastric contents to the upper aero-digestive tract, which causes a variety of symptoms, such as cough, hoarseness, and asthma, among others.Although heartburn is a primary symptom among people with...
(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 senors 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 pharynx
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
and new studies has focused on the development of a new pH sensor which can function in the challenging environment of the oropharynx.