Esophageal Manometry

Esophageal manometry measures the different factors that play a role in the motility and function of the upper esophageal sphincter (UES), the body of the esophagus, and the lower esophageal sphincter (LES).[1, 2]

The esophagus can be affected by a variety of disorders that may be intrinsic or secondary to another pathologic process, but the resulting symptoms are usually not pathognomonic for a specific problem, making diagnosis somewhat challenging.

Although detailed history taking, review of symptoms, and physical examination can orient the clinician in the right direction, further tests, including esophageal manometry, are sometimes necessary for establishing a diagnosis. The first attempts to test esophageal function date back to 1883,[3, 4]  but the technology that would allow a proper recording of esophageal pressure dynamics was not developed until the 1970s.

Esophageal manometry is indicated for the following situations:

• Evaluation of noncardiac chest pain or esophageal symptoms not diagnosed by endoscopy (or after  gastroesophageal reflux disease [GERD] has been excluded)
• Evaluation for  achalasia ^[5]  or another type of nonobstructive  dysphagia
• Preoperative evaluation for patients undergoing corrective surgery for GERD, particularly if an alternative diagnosis like  scleroderma or achalasia is being considered ^[6]
• Postoperative evaluation of dysphagia in patients who underwent corrective surgery for reflux or after treatment of achalasia
• Prior to esophageal pH monitoring to assess the location of the LES for proper electrode positioning
• Evaluation of esophageal motility problems associated with systemic diseases

According to the Lyon Consensus,[7] high-resolution manometry (HRM) is not useful for the direct diagnosis of GERD but can be useful in the setting of GERD by providing adjunctive information (eg, on esophagogastric junction [EGJ] barrier function, esophageal body motor function, contractile function, or EGJ obstruction). American College of Gastroenterology (ACG) guidelines do not recommend HRM solely as a diagnostic test for GERD.[6]

A study of patients who underwent protocolized videoesophagography (VEG) and manometry in preparation for foregut surgery found that routine manometry was not warranted in patients with normal VEG and suggested that it should be reserved for patients with abnormal VEG.[8]

Esophageal manometry is contraindicated in the following situations:

• Patients with altered mental status or obtundation
• Patients who cannot understand or follow instructions
• Suspected or known pharyngeal or upper esophageal obstruction (eg, tumors)

Procedural planning

Some conditions can lead to technical difficulties when performing esophageal manometry, such as achalasia, large hiatal hernias, intrathoracic stomach, and patients with prior esophageal surgery, among others. Knowledge about these conditions can help the technician prepare beforehand for difficulties that may arise. A variety of problems can affect the esophagus and produce multiple symptoms; this can give some insight into what the diagnosis may be and how to tailor the procedure to the suspected affected area.

Complication prevention

If one encounters problems or resistance that cannot be overcome with reasonable pressure while trying to pass the manometry catheter through the nostrils (particularly in patients with prior nasal surgery, deformation, or small nares), the catheter can instead be introduced through the mouth. This will avoid lesions caused by forcing the catheter against resistance.

One of the key aspects of a successful esophageal manometry study is to thoroughly explain the procedure beforehand to patients so as to bring down their anxiety levels. The prospect of having a tube passed through the nose and into the stomach can generate apprehension that can interfere with the technical quality of the study. Patients need to be assured that although they may be uncomfortable, it is not a painful study and they will not choke.

The patient should not have anything to eat or drink for at least 4 hours before the procedure (diabetic patients should take nothing orally after midnight the night before).

Regular medications can be taken with a small amount of water. Although some medications may alter esophageal motility (eg, antispasmodics, prokinetic agents, analgesics, opiates, or sedatives), if the patient is taking them on a daily basis for a chronic condition, it may make sense to perform the study while the patient is on these medications, so as to factor in their systemic effects in the test results and decide on possible further therapy. Because it is difficult to interpret abnormalities in the setting of these medications, repeat procedures off therapy may be required.

Equipment for esophageal manometry includes the following:

• Manometry catheter - High-resolution manometry (HRM) is the current standard ^[9] ; solid-state systems are acceptable if no other equipment is available
• Manometer software with computer monitor
• Lidocaine spray
• Water-based lubricant
• Glass of water with straw
• Syringe, 60 mL
• Normal saline solution (if performing manometry with impedance)
• High ionic gel-consistency solution (for patient to swallow for impedance measurements)
• Tape such as Transpore 3M ^TM (to secure the manometry catheter to the patient's nose throughout the procedure)
• Tissues (to offer to patient as needed throughout the procedure)

As a side note, it is recommended that all liquids and disposable items be kept on a movable cart away from computer and electronic equipment.

Equipment is shown in the image below.

Anesthesia

Because the purpose of esophageal manometry is to record esophageal pressures for further understanding of esophageal motility and function, the procedure must be done in a patient who is fully awake and conscious. The areas through which the manometry catheter will be passed are anesthetized with a topical anesthetic, such as lidocaine spray for the pharynx and viscous lidocaine for the sinuses.

Positioning

With the patient sitting upright, the pharynx and the nostril are anesthetized. In the same position, the catheter is passed through the nose, down the throat, and through the esophagus into the stomach while the patient takes small sips (see Technique).

Afterward, the patient is asked to lay down; motility testing of the lower esophageal sphincter (LES) and esophageal body function should always be performed in a supine patient. Although some esophageal motility laboratories continue to perform this study in the upright position, no set of upright normal values exists that could be comparable to established supine normal values.

The patient can resume his or her regular diet after the procedure. Any sore throat or discomfort can be alleviated by over-the-counter lozenges. The patient can usually expect a few days to pass before being notified of the results; the study must be analyzed and interpreted by the technician, the gastroenterologist, or both.

During the 1950s, different types of water-filled catheters were used for esophageal manometry studies. Although the initial technology was limited, it evolved in ways that allowed further understanding of esophageal motility and subsequent development of more sophisticated catheters.

This system was used exclusively until the 1970s, when the first solid-state transducer was developed and slowly started to replace water-filled catheters as the preferred method. During the next 20 years, a number of studies were performed to try to establish what would be considered normal values for esophageal pressure dynamics.

Before studies are performed, the esophageal manometry catheter must be measured against a ruler to verify accuracy. The most distal recording point represents the zero point; usually, when the catheter is introduced into the patient, the number seen at the nose corresponds to the measured distance to the zero point. The specific distances between the different transducers must also be known; in current practice, modern computer software extrapolates the information regarding the space between the transducers.[10]

Another step to be performed prior to the study is calibration—that is, applying a known pressure to the transducers of the solid-state system by placing the catheter within a mercury manometer and seeing what number is actually displayed on the screen. The water-perfusion catheter is calibrated by recording pressures generated as air within the system is compressed. Failure to display the expected pressures should warrant further investigation prior to the study.[11]

Help take the procedure off the patient's mind by actively involving him or her in the process. With the patient sitting up (having already anesthetized the nostril and the throat a couple of minutes before), have the patient hold a cup of water with a straw in one hand and the catheter connector in the other.

Apply a water-based lubricant to the first 5 cm of the catheter tip. With the chin slightly tilted down, begin to pass the catheter slowly through the sinuses. Point the catheter tip towards the patient's contralateral earlobe as if crossing the floor of the sinuses. After the catheter has been passed about 12 cm, the tip will likely be at the level of the hypopharynx, where it usually will not generate a gag reflex. It is at this point that the patient may feel the catheter in the back of the throat.

Next, have the patient keep the shoulders down (to control gagging), and have him or her start taking small but continuous sips of water through the straw with relaxed swallows. Slowly start advancing the catheter, 3-4 cm at a time. Drinking water in this fashion will help maintain relaxation of the lower esophageal sphincter (LES) while contractile activity in the esophageal body is inhibited.

The catheter will have reached the stomach when the most distal transducer shows an increase in pressure as it passes the LES, with a subsequent drop. Afterward, place the patient in the supine position. Confirm that the transducers are in the stomach by asking the patient to take a deep breath; inspiration causes pressure in the abdominal cavity to rise, whereas expiration causes pressure to go down.

At this point, withdraw the catheter from the stomach, 1 cm at a time, keeping watch for an increase in pressure that will signal when the transducer is crossing the LES. The tracing must be marked each time the catheter is moved.

When the ManoScan high-resolution manometry (HRM) system (Medtronic, Minneapolis, MN) is used, visualization of the LES and the upper esophageal sphincter (UES) on the computer screen and noting the catheter position at the nares will allow the procedure to move forward. The catheter should then be taped to the nose to keep it in place.

With the inSIGHT Ultima HRM system (Diversatek, Milwaukee, WI), a gastric baseline is obtained, and the catheter must then be withdrawn and positioned on a horizontal line, which is displayed on the computer screen. As with the other system, at this time the study can move forward with swallows.

With the most distal circumferential transducer in the LES, give ten 5-mL water swallows to the patient with 20-30 seconds in between to evaluate the LES relaxation pattern and the contraction of the smooth-muscle distal esophagus. After these sips, pull the catheter out further, 0.5 cm at a time, allowing the patient to take a few breaths between moves without swallowing (keeping the mouth slightly open suppresses the need to swallow).

In HRM, the catheter remains in place; however, readers are encouraged to follow their system guidelines. With either of the aforementioned HRM systems, some transducers will remain in the stomach; thus, it is not the most distal transducer that is providing readings at the LES. 

The proximal LES border is at the point where the pattern changes to show thoracic pressures (decrease with inspiration, increase on expiration). This decrease in pressure with inspiration is known as the respiratory or pressure inversion point. 

When the area of maximal UES pressure is reached, manipulate the catheter so as to place the most proximal transducer 1 cm below the sphincter. This time, give five 5-mL water swallows; this allows evaluation of the skeletal muscle. In HRM, no movement of the catheter is necessary to gather these data.

Being able to pinpoint the location of the UES also aids in determining the length of the esophagus for subsequent pressure interpretation and possible pH probe positioning. To study the UES itself and the pharynx, the patient is then placed in an upright sitting position. The catheter is withdrawn in the same fashion as mentioned above until the distal transducer is located at the high-pressure zone of the UES.

When the catheter reaches the proximal border of the sphincter, the pressure will drop. At this time, six 5-mL water swallows are performed. An M-shaped configuration pattern should be observed with each swallow as the UES elevates onto the transducer (first pressure spike), then relaxes (first pressure fall), closes (second pressure spike), and finally descends onto its original starting position (second pressure fall).

Once the study is complete, the recorded pressures coupled with the knowledge of the distance between the recording points allow analysis of the results.

For example, assume that the proximal LES is found at 46 cm and the distal LES at 50 cm. In this case, the LES is approximately 4 cm long (50 – 46 = 4 cm). Swallows are then performed with the distal transducer in the LES high-pressure zone at 47 cm, and with the transducers 5 cm apart within one another, the distal esophagus is studied with transducers at 42, 37, and 32 cm (ie, at 5, 10, and 15 cm above the LES).

Suppose that the UES is then located at 18 cm from the nares and the proximal esophagus was studied at 19, 24, 29, and 34 cm (ie, 1, 6, 11, and 16 cm below the UES). By mapping out these locations, the esophageal length is calculated to be 28 cm by subtracting the proximal LES position from the UES location (46 – 18 = 28 cm).

In plotting the transducer positions, one is able to see that some overlapped during the study, and numbers obtained from them should be comparable. Esophageal length usually ranges between 18 and 28 cm and LES length between 3 and 5 cm.

Once the values are recorded within their anatomic locations, further analysis is carried out. Given that manometric result recording is largely computer-based, the option for automated analysis would be beneficial, in that it could potentially lead to a decrease in interoperator variability and further standardization of results. However, this has not been perfected to the point where it could substitute for expert clinician analysis; clear cutoffs do not exist in certain areas where artifact could be distinguished from true peristaltic contractions.[12]

Analysis of manometric data has been enhanced by topographic data presentation through HRM (see the image below). As the name implies, HRM is a method of axial data interpolation derived from information obtained from multiple recording sites. The information is then presented as a three-dimensional[13] or two-dimensional contour plot in which ranges of pressure amplitude are represented by color or grayscale gradient or concentric rings.[14] This provides a snapshot and allows dynamic representation of motility and peristalsis along the body of the esophagus.

Another technology that has been combined with manometry is intraluminal electrical impedance monitoring. This consists of pairs of metal rings dispersed along the catheter that quantify the impedance between them. Because air, fluids, and solids have unique impedance characteristics, the information provided allows the clinician to assess the effectiveness of intraluminal clearance and esophageal motor activity.

Manometric evaluation of the UES is complicated by its asymmetric and complex anatomy and by its movement during swallowing. The presence of the catheter itself also stimulates its contraction. Proximal esophageal contractions can be assessed for amplitude, but the normal values are not known; the clinical utility of this evaluation is therefore somewhat limited. However, when this is combined with concurrent fluoroscopy, it provides added insight into the understanding and evaluation of problems like Zenker diverticula and cricopharyngeal bars.

Regarding the esophageal body, manometry has shown that bolus transit through the esophageal body does not occur in a single smooth wave; rather, it reflects a sequence of contractions that occur within four pressure segments extending from the UES to the LES. Associated with proper distal esophageal emptying is a peristaltic amplitude of greater than 30 mm Hg; this cutoff has a specificity of 66% and a sensitivity of 85% for identifying incomplete bolus transit.

The esophagogastric junction (EGJ) pressures are a result of the combination of the intrinsic LES tone with pressure contributed by the right crus of the diaphragm; this allows for a wide range in what is considered normal values within end inspiration and end expiration. However, a significantly low value (< 5 mm Hg) is definitely considered abnormal.

Additionally, the most important measurement obtained during esophageal manometry is probably the value of LES relaxation; great advances in determining what is considered normal values have been achieved after the introduction of HRM. (See the image below.)

Table 1 below summarizes some values used to determine normal esophageal function and primary motility disorders.

Table 1. Criteria for Normal Esophageal Function and Primary Motility Disorders (Open Table in a new window)

Chicago classification

Version 4.0 of the Chicago Classification for esophageal motility disorders provides a simplified and standardized way of analyzing the data from an HRM study to diagnose these disorders.[15]  The main measurements obtained by HRM that are used to make diagnoses are as follows:

• Integrated relaxation pressure (IRP)
• Distal contractile integral (DCI)
• Contractile wavefront integrity at 20 mm Hg isobaric contour setting
• Distal latency (DL)

The first decision point centers on evaluating the IRP as either normal (supine, < 15 mm Hg for Medtronic and < 22 mm Hg for Diversatek; upright, < 12 mm Hg for Medtronic and < 15 mm Hg for Diversatek) or abnormal (above the aforementioned values).[15] Conditions with an abnormal IRP include the following:

• Type I, II, and III achalasia
• EGJ outflow obstruction

Conditions with a normal IRP include hypercontractile esophagus (jackhammer), distal esophageal spasm (DES), absent contractility, and ineffective esophageal motility (IEM).[15]

The Chicago Classification broadly classifies esophageal motility disorders as disorders of EGJ outflow (achalasia, EGJ outflow obstruction) or disorders of peristalsis (absent contractility, DES, hypercontractile esophagus, IEM), and it no longer distinguishes between major and minor disorders of peristalsis.[15] The former diagnoses of hypertensive LES, nutcracker esophagus, hypotensive LES, and hypocontractile LES have been eliminated; fragmented peristalsis is now incorporated into the diagnosis of IEM.

Gastroesophageal reflux disease

Although one would assume that gastroesophageal reflux disease (GERD) should be consistently associated with low EGJ pressure, more than 95% of these patients have a basal LES pressure higher than 10 mm Hg.[16]  This is probably related to the fact that transient LES relaxation episodes can occur outside the timeframe within which the study is performed. Esophageal body peristalsis can also be impaired, with failed contractions of less than 30 mm Hg leading to impaired volume clearance (ie, ineffective esophageal motility). However, although these abnormalities are associated with GERD, they are not pathognomonic.

As regards management, manometry is used in determining proper probe positioning for esophageal pH monitoring and aids in the preoperative and postoperative evaluation of antireflux surgery. However, there is a poor correlation between the results of preoperative manometry and the postoperative success and resolution of symptoms; manometry is mainly used to rule out other causes of symptoms if an alternative diagnosis is being considered.[17] After surgery, manometry can help determine whether the cause of dysphagia is related to an underlying motility problem or to a surgical complication.

Achalasia

The classic manometric findings of achalasia include smooth-muscle esophageal aperistalsis and impaired relaxation of the LES/EGJ. The intramural myenteric plexus neurons that are absent in this condition promote LES relaxation and propagation of peristalsis, which explains these findings. Of note, a few manometric pattern variants of this condition exist, which show its complex nature, as follows.

In achalasia type I (see the image below), there is no significant esophageal body pressurization; this subtype is more likely to present with endoscopic evidence of esophageal dilation. The Chicago classification categorized type I achalasia as having an abnormal median IRP and failed peristalsis with all swallows.[15]

The manometric pattern of achalasia type II (see the image below) shows compartmentalized esophageal pressurization, which can span the whole length of the esophageal body. Of the three types of achalasia, type II is considered to have the best rate of response to treatment. The Chicago classification categorized type II achalasia as having an abnormal median IRP with 100% failed peristalsis with panesophageal pressurization in at least 20% of swallows.[15]

Achalasia type III (see the image below) is characterized by spastic contractions, which can even obliterate the esophageal lumen; this type is considered to be predictive of a lower treatment response than is seen with types I and II.[18]  The Chicago classification categorized type III achalasia as having an abnormal median IRP with no normal peristalsis and at least 20% of swallows with premature contractions.[15]

Further studies regarding the subclassification of achalasia are necessary to fully understand the different diagnostic and treatment strategies and the impact it has on patients' symptoms and disease course.[19]

Isobaric simultaneous contractions and elevated intraesophageal pressure support the diagnosis of achalasia; however, these manometric findings are undistinguishable from Chagas disease. The presence of impaired LES relaxation differentiates achalasia from other conditions in which esophageal aperistalsis can be present (eg, diabetes and GERD), but is unable to distinguish it from Chagas disease.

Esophagogastric junction outflow obstruction

EGJ outflow obstruction is characterized by a an elevated median IRP in the primary and secondary positions and at least 20% swallows with elevated intrabolus pressure in the supine position, with evidence of peristalsis.[15]  The etiology of EGJ outflow obstruction has been postulated to be secondary to early achalasia or infiltrative disorders or to represent the manometric findings of a hiatal hernia.

Distal esophageal spasm

DES still has an unclear etiology, but what is known is that it is associated with intermittent abnormal esophageal contractions that can cause dysphagia, chest pain, or both. Although the presence of simultaneous contractions is characteristic, as many as 20% of healthy volunteers are found to have them in the absence of symptoms (probably because of their low amplitude).

Some have proposed that a minimum amplitude of 20 mm Hg should be necessary for diagnosis.[20]  The Chicago classification defined this condition as having a normal median IRP with at least 20% of swallows characterized by premature (DL < 4.5 s) contractions with a DCI higher than 450 mm Hg⋅s⋅cm.[15]

A further debate that has risen, however, is whether DES should be considered a motor disorder in and of itself. If one limits the definition to meeting exactly all the criteria, it would be a very rare condition. If the defining parameters are broadened, it would be overdiagnosed.

Hypercontractile esophagus

The category of hypercontractile motility disorders has included nutcracker esophagus (increased mean amplitude >180 mm Hg with normal peristalsis and prolonged distal esophageal contraction) and hypertensive LES (resting pressure greater than 45 mm Hg with possible impaired relaxation). (See the image below.) On the basis of the Chicago classification, the diagnosis of nutcracker esophagus has been eliminated and replaced by jackhammer esophagus.[15]

As the name suggests, the main problem in hypercontractile motility disorders stems from excess contractility of the LES, the esophageal body, or both. These disorders are not fixed and may therefore vary and evolve into another form of motility disorder over time.

Jackhammer esophagus

Jackhammer esophagus has been defined as a normal median IRP with at least two swallows with a DCI greater than 8000 mm Hg⋅s⋅cm (see the image below). The DCI is measured from the transition zone to the proximal LES; however, in instances where the hypercontractility appears to involve the LES, the DCI should be extended to include the LES to obtain the accurate diagnosis.[15]

Absent contractility

Absent contractility is defined as a normal median IRP with 100% failed peristalsis.[15] In situations when the IRP is close to 15, it is prudent to consider type I achalasia as a diagnosis. Additionally, when the DL is less than 4.5 seconds and the DCI is less than 450 mm Hg⋅s⋅cm, a diagnosis of failed peristalsis should be considered. Absent contractility is considered to be a major disorder of peristalsis.

Ineffective esophageal motility

IEM is defined as a normal median IRP and more than 70% ineffective swallows (DCI ≥100 mm Hg•s•cm and < 450 mm Hg⋅s⋅cm) or at least 50% failed peristalsis (DCI < 100 mm Hg•s•cm).[15]

Multisystem/collagen vascular diseases

The pattern observed in these cases include aperistalsis in the distal two thirds of the esophagus (smooth muscle) and diminished or absent LES tone. In contrast, UES tone and proximal esophageal function are preserved. However, this constellation is not pathognomonic for diagnosis and can be sometimes seen in other conditions, such as GERD.

Esophageal manometry is a generally safe procedure, and complications are usually few and mild (eg, gagging and watery eyes during the catheter insertion, sore throat, rhinorrhea, and epistaxis). More severe complications occur rarely and may include arrhythmias, vasovagal episodes, bronchospasm, and aspiration. To our knowledge, there has only been a single report of esophageal perforation with this procedure.[21]

In situations where manometry must be performed despite the presence of relative contraindications, precautions such as endoscopic or radiologic guidance must be performed to decrease the risk of complications.