High-resolution manometry (HRM) was conceived by Ray Clouse to overcome gaps in esophageal pressure data acquisition, display and interpretation. HRM utilizes closely spaced circumferential sensors on an esophageal manometry catheter to collect pressure recordings. Software programs interpolate best fit data between acquired raw pressure data and assign colors to amplitudes to generate seamless topographic plots of pressure phenomena (Figure 1A). The topographic color plots are known as â€œClouseâ€ plots in Ray Clouseâ€™s honor.1
Before high-resolution manometry there was conventional manometry, with five to eight data sensors displaying point pressure in the form of stacked line tracings. A prominent disadvantage was the stationary pull-through maneuver, the process of locating the esophagogastric junction and its components. Modern HRM systems eliminate this maneuver, as pressure activity from the entire esophagus is visible and catheter position can be modified in real time to ensure the esophagogastric junction is traversed. The dynamic respiratory pressure signature of the lower esophageal sphincter (LES) and the crural diaphragm define esophagogastric junction morphology, and esophageal length can also be easily determined.2
A profound advantage of HRM over conventional manometry lies in the utilization of software tools to interrogate pressure data, particularly at the esophagogastric junction. The integrated relaxation pressure (IRP) measures nadir pressure during swallow induced lower esophageal sphincter relaxation. The LES can be followed proximally when the esophagus shortens, ensuring that the IRP is always measured appropriately (Figure 1B), enhancing identification of esophageal outflow obstruction. Esophageal body software tools assess vigor of smooth muscle contraction (distal contractile integral, DCI) and timing of the peristaltic sequence (distal latency, DL). Using these three software tools, esophageal motor processes have been classified into disorders with EGJ outflow obstruction (including achalasia), major motor disorders not encountered in health, and minor motor disorders with transit abnormalities that are not pathognomonic of disease states. This socalled Chicago Classification has brought uniformity to nomenclature and reporting of esophageal motor phenomena.3 New software metrics such as the EGJ contractile integral (EGJ-CI) are under study for evaluation of the EGJ barrier. Provocative measures, including multiple rapid swallows, free-water drinking or test meals, stress the esophagus when symptoms are not easily explained, and can uncover motor patterns not evident with routine water swallows.2,3 Finally, 3D HRM (higher sensor density in a short catheter segment that allows sector averaging of recorded pressures) generates a three-dimensional pressure profile of selected areas, particularly the EGJ where distinct EGJ asymmetry has been identified at rest and during inspiration. These software tools and provocative options cannot be utilized in a similar fashion with conventional manometry.
Non-manometric alternatives to evaluating esophageal symptoms provide additional information that can complement but not replace HRM. For instance, endoscopy with biopsy and endoscopic ultrasound can help exclude a structural basis for esophageal outflow obstruction, especially when esophageal body motor patterns are not typical for achalasia. Barium studies, particularly with solid bolus swallows, can cause structural esophageal lesions. Additional barium findings of clinical value include abnormal esophageal emptying, barium column height in the upright position (i.e. timed upright barium study) and EGJ morphology (i.e., hiatus hernia, achalasia, strictures). The addition of impedance and impedance planimetry to topographic representation of esophageal pressure phenomena continue to be studied as adjuncts to standard HRM. Impedance planimetry using the functional luminal imaging probe can measure cross sectional areas, providing information on elasticity and compliance. The functional luminal imaging probe can assess adequacy of EGJ disruption in achalasia, compliance of the EGJ in reflux disease (especially following fundoplication) and esophageal sensitivity to distension.
HRM represents a distinct advance over previously utilized motility systems, and continues to evolve.
For the uninitiated, high-resolution manometry may seem challenging, another new complicated technique to master. While even experts may not agree on the subtleties of the Chicago Classification of motor disorders, novice and intermediate trainees preferred high-resolution manometry to conventional manometry when offered studies in both formats following a tutorial describing the two methods.4 Pattern recognition allows for easy recognition of achalasia and major motor disorders, and indeed, such recognition was retained at a three-month follow-up assessment.4 Another study comparing the two methods reported much higher accuracy with high-resolution manometry compared to conventional manometry in both novice and expert reviewers.5 Intermediate and novice trainees could identify normal from abnormal motor patterns with management recommendations after teaching and supervised review of 15 to 25 studies.6 The role of the operator in obtaining pristine, artifact-free studies is crucial, and visual review of the motor patterns is essential in corroborating diagnoses suggested by an automated and computerized review of studies. High-resolution manometry therefore represents a distinct advance over previously utilized motility systems, and continues to evolve. The accuracy of high-resolution manometry interpretation may be tempered by the quality of the studies (which is directly related to the skill of the operator), the corroboration of automated analysis with direct visual review, and the diligence of the motility expert in identifying abnormalities that can explain symptoms. Nevertheless, high-resolution manometry is here to stay, and there is no viable alternate method of evaluating esophageal motor function that can replace it in the near term.
Dr. Gyawali serves as a consultant for Medtronic, Valiant Quintiles and AbbVie. He has lectured on behalf of Forest-Ironwood, Salix and AbbVie, and has received research support from Given Imaging/Medtronic.
1.Gyawali CP. High resolution manometry: the Ray Clouse legacy. Neurogastroenterol Motil 2012;24 Suppl 1:2-4.
2. Gyawali CP, Bredenoord AJ, Conklin JL, et al. Evaluation of esophageal motor function in clinical practice. Neurogastroenterol Motil 2013;25:99-133.
3. Kahrilas PJ, Bredenoord AJ, Fox M, et al. The Chicago Classification of esophageal motility disorders, v3.0. Neurogastroenterol Motil 2015;27:160-74.
4. Soudagar AS, Sayuk GS, Gyawali CP. Learners favour high resolution oesophageal manometry with better diagnostic accuracy over conventional line tracings. Gut 2012;61:798- 803.
5.Carlson DA, Ravi K, Kahrilas PJ, et al. Diagnosis of Esophageal Motility Disorders: Esophageal Pressure Topography vs. Conventional Line Tracing. Am J Gastroenterol 2015;110:967-77.
6.Gaddam S, Reddy CA, Munigala S, et al. The Learning Curve for Interpretation of Esophageal High Resolution Manometry (HRM) After a Standardized Teaching Curriculum: A Prospective Interventional Cohort Study. Gastroenterology 2015;148:S806-7.