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AGA technical review on the clinical use of esophageal manometry

2005; Elsevier BV; Volume: 128; Issue: 1 Linguagem: Inglês

10.1053/j.gastro.2004.11.008

1528-0012

John E. Pandolfino, Peter J. Kahrilas,

Dysphagia Assessment and Management

This literature review and the recommendations therein were prepared for the American Gastroenterological Association Clinical Practice Committee. The paper was approved by the Committee on October 2, 2004, and by the AGA Governing Board on November 7, 2004. This literature review and the recommendations therein were prepared for the American Gastroenterological Association Clinical Practice Committee. The paper was approved by the Committee on October 2, 2004, and by the AGA Governing Board on November 7, 2004. The utility of esophageal manometry in clinical practice resides in 3 domains: (1) to accurately define esophageal motor function, (2) to define abnormal motor function, and (3) to delineate a treatment plan based on motor abnormalities. Since the first American Gastroenterological Association technical review on esophageal manometry published 10 years ago,1An American Gastroenterological Association medical position statement on the clinical use of esophageal manometry. American Gastroenterological Association.Gastroenterology. 1994; 107: 1865Google Scholar, 2Kahrilas P.J. Clouse R.E. Hogan W.J. American Gastroenterological Association technical review on the clinical use of esophageal manometry.Gastroenterology. 1994; 107: 1865-1884Abstract Full Text PDF PubMed Google Scholar advances have been made within each of these domains. By and large, these advances have not been the result of major technological changes but rather a reflection of improved manometric technique and research. With this in mind, the goal of this second technical review on the clinical use of esophageal manometry is to summarize what has been learned during the past 10 years and discuss how this has modified the clinical management of esophageal disorders. Thus, we performed a literature search for all English-language articles dealing with manometric evaluation of the esophagus from 1994 to 2003. The databases searched included MEDLINE, PreMEDLINE, and PubMed using general terms related to manometric technique (sleeve, topography) and equipment (water perfused, solid state), esophageal symptoms (dysphagia, chest pain, heartburn), esophageal disorders and procedures (gastroesophageal reflux disease, achalasia, diffuse esophageal spasm, nutcracker esophagus, hypertensive LES, nonspecific motor disorders, ineffective esophageal motility, fundoplication, myotomy, dilation), and terms focused on esophageal motor function (upper esophageal sphincter, lower esophageal sphincter, esophageal body, peristalsis). Additional references were identified from references of reviewed manuscripts. Manometry is by nature a highly technical evaluation, more akin to physiologic studies than to endoscopic or radiographic ones. When optimally utilized and providing that physical principles and equipment characteristics are respected, a manometric examination provides an accurate description of esophageal contractile function. In general, manometric data are only as valid as the methodology used to acquire them. The frequency content of esophageal contractile waves defines the required characteristics of a manometric recording device. The frequency response required to reproduce esophageal pressure waves with 98% accuracy is 0–4 Hz, while that required for reproducing pharyngeal pressure waves is 0–56 Hz.3Orlowski J. Dodds W.J. Linehan J.H. Dent J. Hogan W.J. Arndorfer R.C. Requirements for accurate manometric recording of pharyngeal and esophageal peristaltic pressure waves.Invest Radiol. 1982; 17: 567-572Crossref PubMed Scopus (44) Google Scholar Expressed in terms of maximal recordable ΔP/Δt, 300 mm Hg/s will suffice for the mid or distal esophagus versus 4000 mm Hg/s for the pharynx. Because the overall characteristics of the manometric system are only as good as those of the weakest element within that system, high-fidelity recordings require that each element (pressure sensor, transducer, recorder) meet or exceed these response characteristics. Modern computer polygraphs and pressure transducers, essentially unchanged in the past 10 years, have response characteristics greatly exceeding those required for esophageal manometry. Thus, most of the methodological evolution that has occurred during the past 10 years has been in the domains of manometric assembly design and data analysis; each of these will be reviewed. The pressure sensor/transducer components of a manometric assembly function as a matched pair and are available in 2 general designs: water-perfused catheters with volume displacement transducers or strain gauge transducers with solid-state circuitry. Major advantages of water-perfused systems are cost and versatility. A major disadvantage is that the equipment is fickle and proper maintenance requires skilled personnel. Illustrative of the versatility possible with perfused manometric assemblies, the past 10 years have witnessed the introduction of multilumen, autoclavable, miniature silicone extrusions that can be configured with nearly infinite variety. Faithful recording of sphincter pressure for extended periods of time or during swallow-related esophageal shortening requires that the pressure sensor maintain a constant position within the high-pressure zone. Sleeve sensors were devised to meet these requirements. However, sleeve sensors were originally made of molded silicone and, before 1994, manometric extrusions were made of polyvinyl chloride. Thus, the sleeve sensor needed to be joined to the end of the polyvinyl extrusion with a complex joint involving metal stents and suture. Although functional, the resultant assembly probably would not meet current requirements for reuse mandated by the need for restoring sterility. On the other hand, the multilumen silicone extrusions currently available (Mui Scientific, Mississauga, Canada; formerly Dentsleeve) can incorporate sleeve sensors directly onto the extrusion, making the resultant assembly both more durable and autoclavable. These catheters have undergone rigorous reuse evaluation and have been deemed safe for reuse by both the Food and Drug Administration (via the 510k mechanism) and EU regulators (CE marked and monitored). An alternative to perfused manometric systems is a manometric assembly incorporating miniature strain gauge sensors and solid-state electronic components. The microtransducers directly interface with the recorder, and the resultant system has a vastly expanded frequency response suitable for pharyngeal recording. On the negative side, solid-state systems are much more expensive, are less modifiable, are more delicate, and do not yet have the versatility of assembly design permissive of either a sleeve sensor or topographic data presentation (see following text). Improvements in design are currently under way, and it is likely that high-resolution solid-state systems will be available in the near future. One other appeal of solid-state systems is that they are not subject to hydrostatic effects and can be miniaturized, factors that make them more suitable for extended ambulatory studies. Having said that, recent research has shown successful use of a portable water-perfusion pump with a sleeve assembly and the resultant publications have provided substantial insight into the pathogenesis of reflux4Schoeman M.N. Tippett M.D. Akkermans L.M. Dent J. Holloway R.H. Mechanisms of gastroesophageal reflux in ambulant healthy human subjects.Gastroenterology. 1995; 108: 83-91Abstract Full Text PDF PubMed Scopus (296) Google Scholar and the mechanisms of reflux in patients with and without a hiatus hernia.5van Herwaarden M.A. Samsom M. Smout A.J. Excess gastroesophageal reflux in patients with hiatus hernia is caused by mechanisms other than transient LES relaxations.Gastroenterology. 2000; 119: 1439-1446Abstract Full Text Full Text PDF PubMed Scopus (248) Google Scholar Given that most manometric recording systems are computer based, the potential exists for automated analysis. Automated analysis of manometric tracings is an appealing concept because it could lead to standardization of what has otherwise been a highly operator-dependent evaluation. However, the pitfalls of interpreting esophageal manometric tracings are plentiful. For example, pressure thresholds established to distinguish contractions from miscellaneous artifacts may ignore hypotensive peristaltic contractions below that threshold. Similarly, the ability of automated analysis to accurately characterize the adequacy of lower esophageal sphincter (LES) relaxation or to differentiate isobaric common cavities from spastic contractions has not been adequately validated. These subtle distinctions can be absolutely crucial in establishing an accurate diagnosis. Thus, although currently available programs may be useful adjuncts in the interpretation of (normal) manometric recordings, automated analysis has not yet matured to a degree that it can replace manual inspection by an experienced clinician. Guidelines for performance of esophageal manometry and standardized reporting are crucial to decrease the degree of subjective interpretation between clinicians. Although not covered in this review, detailed methods regarding these issues were recently published by members of the American Motility Society and the European Society of Neurogastroenterology and Motility Working Group on Esophageal Manometry.6Murray J.A. Clouse R.E. Conklin J.L. Components of the standard oesophageal manometry.Neurogastroenterol Motil. 2003; 15: 591-606Crossref PubMed Scopus (81) Google Scholar An offshoot of the introduction of multilumen miniature extrusions has been the application of topographic data presentation to manometric recordings. Topographic analysis is a method of axial data interpolation derived from computerized plotting of data from multiple, closely spaced recording sites.7Clouse R.E. Staiano A. Alrakawi A. Development of a topographic analysis system for manometric studies in the gastrointestinal tract.Gastrointest Endosc. 1998; 48: 395-401Abstract Full Text Full Text PDF PubMed Scopus (58) Google Scholar The interpolated pressure information is plotted as either a 3-dimensional surface plot or a 2-dimensional contour plot in which pressure amplitude is represented by concentric rings or color gradients with an appropriate scale (Figure 1). The advantage of this presentation is that it provides a complete, dynamic representation of peristalsis at every axial position along the esophagus, as opposed to the fragmented data presented in conventional manometric tracings. However, even though this technique has provided significant insight into the physiology of peristalsis and has the potential to redefine the way we evaluate sphincter relaxation, it is debatable as to whether or not it has yet demonstrated any clear advantage over conventional manometry in clinical practice.8Holloway R.H. Topographical clinical esophageal manometry a better mousetrap or manometric overkill?.Am J Gastroenterol. 2000; 95: 2677-2679Crossref PubMed Google Scholar Although manometric apparatus has not changed significantly in the past 10 years, there has been significant interest in combining manometry with a newly evolving technology, intraluminal impedance monitoring. Impedance monitoring works by quantifying the impedance between pairs of metal rings dispersed along the combined manometry/impedance assembly. Air, fluid bolus, and the esophageal wall each have unique impedance characteristics, thereby allowing definition of which resides between each pair of electrodes. Defining impedance changes over adjacent pairs of rings defines bolus transit within the esophagus.9Fass J. Silny J. Braun J. Heindrichs U. Dreuw B. Schumpelick V. Rau G. Measuring esophageal motility with a new intraluminal impedance device. First clinical results in reflux patients.Scand J Gastroenterol. 1994; 29: 693-702Crossref PubMed Scopus (111) Google Scholar, 10Nguyen H.N. Silny J. Albers D. Roeb E. Gartung C. Rau G. Matern S. Dynamics of esophageal bolus transport in healthy subjects studied using multiple intraluminal impedancometry.Am J Physiol. 1997; 273: G958-G964PubMed Google Scholar, 11Srinivasan R. Vela M.F. Katz P.O. Tutuian R. Castell J.A. Castell D.O. Esophageal function testing using multichannel intraluminal impedance.Am J Physiol Gastrointest Liver Physiol. 2001; 280: G457-G462PubMed Google Scholar Studies using combined fluoroscopy and impedance have validated the convention that liquid bolus entry is signaled by a 50% decrease in impedance at the recording site, while bolus exit is signaled by a return to at least 50% of baseline12Simren M. Silny J. Holloway R. Tack J. Janssens J. Sifrim D. Relevance of ineffective oesophageal motility during oesophageal acid clearance.Gut. 2003; 52: 784-790Crossref PubMed Scopus (204) Google Scholar, 13Sifrim D. Castell D.O. Dent J. Kahrilas P.J. Gastro-oesophageal reflux monitoring review and consensus report on detection and definitions of acid, non-acid and gas reflux.Gut. 2004; 53: 1024-1031Crossref PubMed Scopus (693) Google Scholar (Figure 1). Currently, impedance monitoring is predominantly used in research as an alternative to fluoroscopy for assessing esophageal transit and emptying. Its role in the clinical evaluation of esophageal motor disorders has not yet been formally assessed. The muscular elements of the upper esophageal sphincter (UES) are the cricopharyngeus, adjacent esophagus, and adjacent inferior constrictor. The cricopharyngeus inserts bilaterally to the inferior-lateral margins of the cricoid lamina, and the zone of maximal UES pressure is ≈1 cm in length at precisely this location.14Kahrilas P.J. Dodds W.J. Dent J. Logemann J.A. Shaker R. Upper esophageal sphincter function during deglutition.Gastroenterology. 1988; 95: 52-62PubMed Google Scholar The closed sphincter has a slit-like configuration, with the cricoid lamina anterior and the cricopharyngeus making up the lateral and posterior walls. Thus, it is not surprising that resting UES pressure is markedly asymmetric, with greatest values anteriorly and posteriorly.15Welch R.W. Luckmann K. Ricks P.M. Drake S.T. Gates G.A. Manometry of the normal upper esophageal sphincter and its alterations in laryngectomy.J Clin Invest. 1979; 63: 1036-1041Crossref PubMed Scopus (132) Google Scholar Because the only insertion of the cricopharyngeus is to the cricoid cartilage, the sphincter and larynx are obliged to move in unison. Manometric evaluation of UES function is difficult because it is a short, complex anatomic zone that moves briskly during swallowing. Furthermore, measurement of UES pressure is heavily influenced by recording methodology due to both its marked asymmetry and the fact that the measurement, in and of itself, stimulates sphincter contraction. The less movement applied to the recording catheter and the smaller the measuring device, the lower the recorded pressures.2Kahrilas P.J. Clouse R.E. Hogan W.J. American Gastroenterological Association technical review on the clinical use of esophageal manometry.Gastroenterology. 1994; 107: 1865-1884Abstract Full Text PDF PubMed Google Scholar In an extreme demonstration of this, a recent study using a microsleeve sensor in healthy volunteers demonstrated periods of negligible resting pressure in all subjects.16Dire C. Shi G. Manka M. Kahrilas P.J. Manometric characteristics of the upper esophageal sphincter recorded with a microsleeve.Am J Gastroenterol. 2001; 96: 1383-1389Crossref PubMed Google Scholar Thus, it is not surprising that there is great variability in reported “normal” ranges of UES pressure, and it is currently impossible to define a meaningful normal range.2Kahrilas P.J. Clouse R.E. Hogan W.J. American Gastroenterological Association technical review on the clinical use of esophageal manometry.Gastroenterology. 1994; 107: 1865-1884Abstract Full Text PDF PubMed Google Scholar UES relaxation during swallowing also poses substantial recording challenges. Relaxation occurs during swallow-associated laryngeal elevation.14Kahrilas P.J. Dodds W.J. Dent J. Logemann J.A. Shaker R. Upper esophageal sphincter function during deglutition.Gastroenterology. 1988; 95: 52-62PubMed Google Scholar However, movement of the sphincter and the transnasally positioned catheter are dyssynchronous. The UES may move 2–3 cm proximally during swallowing, whereas the sensor may move only 1 cm.14Kahrilas P.J. Dodds W.J. Dent J. Logemann J.A. Shaker R. Upper esophageal sphincter function during deglutition.Gastroenterology. 1988; 95: 52-62PubMed Google Scholar Given the short length of the high-pressure zone, this dissociation simulates relaxation with a focal sensor. Although positioning the recording site at the proximal aspect of the UES to anticipate subsequent movement appears to be a logical solution,17Castell J.A. Castell D.O. Modern solid state computerized manometry of the pharyngoesophageal segment.Dysphagia. 1993; 8: 270-275Crossref PubMed Scopus (81) Google Scholar movement of both the UES and the catheter may vary among individuals and certainly among various disease conditions, making such an approach unreliable. Given the methodological challenges detailed above, the utility of UES manometry in clinical practice has been questioned. Illustrative of this, a recent retrospective review of 435 manometric studies with adequate evaluation of the UES and pharynx reported that 80 patients had one or more UES abnormality detected.18Malhi-Chowla N. Achem S.R. Stark M.E. DeVault K.R. Manometry of the upper esophageal sphincter and pharynx is not useful in unselected patients referred for esophageal testing.Am J Gastroenterol. 2000; 95: 1417-1421Crossref PubMed Google Scholar Among these subjects, 17 patients were known to have or suspected of having an oropharyngeal problem whereas in 58 patients the finding was unexpected. In only 3 subjects with purely UES/pharyngeal abnormalities was there a change in therapy based on the manometric findings; 2 were instructed on dietary modifications and one had swallow therapy initiated. The investigators concluded that routine UES/pharyngeal manometry is of limited clinical utility. Although routine UES and pharyngeal manometry is of questionable use, studies combining UES and pharyngeal manometry with concurrent fluoroscopy have provided significant insight into the pathogenesis of cricopharyngeal bars and Zenker’s diverticula. Using a manometric catheter with 3-cm spacing and exacting videofluoroscopy, Dantas et al questioned the prevailing notion that cricopharyngeal bars were caused by impaired UES relaxation (so-called “cricopharyngeal achalasia”) and instead demonstrated the problem to be of reduced compliance and impaired sphincter opening.19Dantas R.O. Cook I.J. Dodds W.J. Kern M.K. Lang I.M. Brasseur J.G. Biomechanics of cricopharyngeal bars.Gastroenterology. 1990; 99: 1269-1274Abstract PubMed Google Scholar More recently, sophisticated analysis of this relationship has been performed using high-resolution, high-fidelity perfused micromanometry to create a topographic mapping of the space-time patterns of hypopharyngeal intrabolus pressure.20Pal A. Williams R.B. Cook I.J. Brasseur J.G. Intrabolus pressure gradient identifies pathological constriction in the upper esophageal sphincter during flow.Am J Physiol Gastrointest Liver Physiol. 2003; 285: G1037-G1048PubMed Google Scholar This work beautifully illustrated that the location and magnitude of the intrabolus pressure gradient correlated with the location of maximal UES constriction (Figure 2). Thus, quantifying pressure gradient characteristics and location may serve as a useful clinical indicator for pathologic constriction of the cricopharyngeus muscle and also may define treatment parameters. The body of the esophagus is a 20–22-cm tube, with the muscularis propria comprised of an inner circular layer and an outer longitudinal layer. Primary peristalsis is initiated by swallowing and is evident shortly after the pharyngeal contraction traverses the UES, progressing distally at a velocity of 2–4 cm/s. Secondary peristalsis can be elicited at any esophageal level in response to luminal distention and progresses from the point of stimulation distally. The mechanical effect of peristalsis is a stripping wave that milks the esophagus clean. Progression of the stripping wave corresponds closely with that of the manometric contraction such that the point of the inverted “V” seen fluoroscopically at each esophageal locus coincides with the upstroke of the pressure wave.21Kahrilas P.J. Dodds W.J. Hogan W.J. Effect of peristaltic dysfunction on esophageal volume clearance.Gastroenterology. 1988; 94: 73-80PubMed Google Scholar However, the recent application of topographic analysis to esophageal peristalsis has clearly demonstrated that progression through the esophageal body is not seamless. Rather, it is comprised of a sequence of contractile events occurring in 4 discrete pressure segments (Figure 1). The first segment represents the striated muscle component of the proximal esophagus and extends from the UES to the first pressure trough in the region of the aortic arch. The distal portion of the esophagus is separated into 2 overlapping neuromuscular segments. This observation elegantly explains the double peaked contractions that are found in 10%–15% of healthy subjects. The second pressure peak of the double peak essentially arises from the third topographic segment overlapping with the second segment and initiating its own contraction with a slight delay. The fourth contractile segment encompasses the LES. This segmental configuration was not appreciated by conventional manometry and underscores the strength of topographic analysis of manometric data.22Clouse R.E. Staiano A. Topography of the esophageal peristaltic pressure wave.Am J Physiol. 1991; 261: G677-G684PubMed Google Scholar, 23Clouse R.E. Staiano A. Topography of normal and high-amplitude esophageal peristalsis.Am J Physiol. 1993; 265: G1098-G1107PubMed Google Scholar, 24Clouse R.E. Staiano A. Alrakawi A. Topographic analysis of esophageal double-peaked waves.Gastroenterology. 2000; 118: 469-476Abstract Full Text Full Text PDF PubMed Scopus (49) Google Scholar The efficacy of distal esophageal emptying is inversely related to peristaltic amplitude such that emptying becomes progressively impaired with peristaltic amplitudes ≤30 mm Hg.21Kahrilas P.J. Dodds W.J. Hogan W.J. Effect of peristaltic dysfunction on esophageal volume clearance.Gastroenterology. 1988; 94: 73-80PubMed Google Scholar This threshold amplitude was initially determined using simultaneous videofluoroscopy and manometry on a relatively small number of subjects. Recently, multichannel intraluminal impedance has been utilized to assess the efficacy of esophageal emptying as a function of peristaltic amplitude in a much greater number of swallows and subjects.25Tutuian R. Castell D.O. Clarification of the esophageal function defect in patients with manometric ineffective esophageal motility studies using combined impedance-manometry.Clin Gastroenterol Hepatol. 2004; 2: 230-236Abstract Full Text Full Text PDF PubMed Scopus (155) Google Scholar Receiver operating characteristic curve analysis of combined manometric/impedance data showed that a 30–mm Hg cutoff for distal esophageal peristaltic amplitude had a sensitivity of 85% and a specificity of 66% for identifying incomplete bolus transit. With diminishing peristaltic amplitudes, the sensitivity progressively decreased and the specificity progressively increased (Figure 3). This analysis nicely illustrates the complementary nature of manometry and impedance testing and could potentially develop into a valuable clinical tool for the assessment of dysphagia. However, one must be cautious in directly applying the results of Figure 3 to disease or postsurgical conditions. To fully describe the efficacy of esophageal emptying, outflow resistance must also be quantified because this will surely vary with disease or postsurgical conditions. Conventional manometry can, for the most part, accurately define the peristaltic waveform of the tubular esophagus. However, there are important limitations inherent in the methodology itself. Manometric assemblies are unable to quantify longitudinal muscle contraction or axial movement. Additionally, manometry alone is insufficient to determine whether an intraluminal pressure waveform is the result of an intrabolus pressure or squeeze pressure within a closed lumen. In general, these limitations can be overcome by using complementary methodologies such as fluoroscopy, impedance monitoring, or topographic analysis (Figure 3). Currently, however, these methods are not routinely used in clinical practice. Physiologically, the esophagogastric junction (EGJ) is a 2- to 4-cm-long asymmetric high-pressure zone attributable to a composite of both the LES and the surrounding right crus of the diaphragm. Manometric and intraluminal ultrasound studies suggest that axial asymmetry of the pressure profile is attributable to the varying thickness of the circular layer of the muscularis propria, while the radial pressure asymmetry results from asymmetric extrinsic compression by the surrounding diaphragmatic crus.26Liu J. Parashar V.K. Mittal R.K. Asymmetry of lower esophageal sphincter pressure is it related to the muscle thickness or its shape?.Am J Physiol. 1997; 272: G1509-G1517PubMed Google Scholar, 27Kahrilas P.J. Lin S. Chen J. Manka M. The effect of hiatus hernia on gastro-oesophageal junction pressure.Gut. 1999; 44: 476-482Crossref PubMed Scopus (261) Google Scholar Intrinsic LES tone is a property of the smooth muscle itself and its autonomic innervation.28Goyal R.K. Sangree M.H. Hersh T. Spiro H.M. Pressure inversion point at the upper high pressure zone and its genesis.Gastroenterology. 1970; 59: 754-759PubMed Google Scholar, 29Holloway R.H. Blank E.L. Takahashi I. Dodds W.J. Dent J. Sarna S.K. Electrical control activity of the lower esophageal sphincter in unanesthetized opossums.Am J Physiol. 1987; 252: G511-G521PubMed Google Scholar Intra-abdominal pressure, gastric distention, hormones, various foods, and medications alter the intrinsic LES pressure, which typically ranges from 10 to 45 mm Hg.2Kahrilas P.J. Clouse R.E. Hogan W.J. American Gastroenterological Association technical review on the clinical use of esophageal manometry.Gastroenterology. 1994; 107: 1865-1884Abstract Full Text PDF PubMed Google Scholar The contribution of the crural diaphragm to EGJ pressure is evident by the direct correlation between intraluminal EGJ pressure and integrated electromyographic spike activity of the crural diaphragm.30Mittal R.K. Rochester D.F. McCallum R.W. Electrical and mechanical activity in the human lower esophageal sphincter during diaphragmatic contraction.J Clin Invest. 1988; 81: 1182-1189Crossref PubMed Scopus (173) Google Scholar Mainly as a result of the diaphragmatic contribution, normal EGJ pressure ranges from 15 ± 11 mm Hg at end expiration to 40 ± 13 mm Hg at end inspiration, measured from the same manometric tracings.31Richter J.E. Wu W.C. Johns D.N. Blackwell J.N. Nelson III, J.L. Castell J.A. Castell D.O. Esophageal manometry in 95 healthy adult volunteers. Variability of pressures with age and frequency of “abnormal” contractions.Dig Dis Sci. 1987; 32: 583-592Crossref PubMed Scopus (502) Google Scholar Thus, similar to the case of the UES, reported ranges of normal EGJ pressure are highly dependent on methodology. The most meaningful statement that can be made regarding isolated measurement of EGJ pressure is that it is abnormal to have an extremely low value (≤5 mm Hg). The manometric evaluation of LES relaxation is arguably the most important measurement made during clinical esophageal manometry. Relaxation of the LES occurs with swallowing, esophageal distention, and transient LES relaxation (tLESR). However, before the publication of the first technical review, there was a paucity of quantitative data regarding LES relaxation. The deficiency was mostly attributable to the lack of standardized recording methodology and data interpretation. Recognizing this void, recent studies have quantified normal deglutitive EGJ relaxation with techniques suited to study a mobile anatomic zone: either a water-perfused sleeve sensor that spans the sphincteric region or high-resolution manometry with topographic data analysis. Shi et al used a standardized methodology of sleeve sensor recording and computer-assisted data analysis and concluded that the best single assessment of EGJ relaxation was mean relaxation pressure (Table 1).32Shi G. Ergun G.A. Manka M. Kahrilas P.J. Lower esophageal sphincter relaxation characteristics using a sleeve sensor in clinical manometry.Am J Gastroenterol. 1998; 93: 2373-2379Crossref PubMed Scopus (34) Google Scholar Using the 95th percentile value of controls (12 mm Hg) as the upper limit of normal, this parameter had a sensitivity and positive predictive value of 92% and 88%, respectively, for a diagnosis of achalasia. However, some manometrists measure LES relaxation pressure during end expiration to exclude the contribution of the crural diaphragm.33Holloway R.H. Penagini R. Ireland A.C. Criteria for objective definition of transient lower esophageal sphincter relaxation.Am J Physiol. 1995; 268: G128-G133PubMed Google Scholar Although this technique is technically a more accurate assessment of the intrinsic sphincter, it is more difficult to standardize the measurement and, hence, a more subjective measurement than the mean LES relaxation pressure. In another study aimed at defining the optimal criteria for incomplete EGJ relaxation, Staiano and Clouse utilized high-resolution manometry with and without topographic analysis.34Staiano A. Clouse R.E. Detection of incomplete lower esophageal sphincter relaxation with conventional point-pressure sensors.