High resolution manometry: the Ray Clouse legacy

Esophageal manometry assesses pressure phenomena, peristalsis and bolus transit in the esophagus. Older ‘conventional’ manometry techniques recorded esophageal peristalsis using 5–8 widely spaced water perfused channels in an esophageal motility catheter. Two significant advances in the 1990s, an increase in pressure sensors along the catheter, and use of spatiotemporal plots for data display, led to what is now recognized as high-resolution manometry (HRM).1,2 HRM was the concept and innovation of a remarkable esophagologist, researcher and educator, the late Ray Eugene Clouse, MD. HRM has its roots in conventional perfused manometry. Clouse decided that the esophagus was holding secrets between the widely spaced recording points of his conventional manometry catheter. He tested his hypothesis by continuing the pull through maneuver 1 cm at a time till the last recording channels reached the upper esophageal sphincter (UES), obtaining at least one wet swallow at each station.1 When the swallows were aligned, the jumble of tracings he obtained could not be easily interpreted. It was time for another Clouse innovation – the spatiotemporal contour plot. Clouse, along with Annamaria Staiano, MD, digitized the tracings using a hand held digitizer, and assigned colors to amplitude levels.1,2 Software programs provided best fit data points in between the recording sites. The final result was a smooth topographic map of the esophageal peristaltic wave. Since amplitudes were color coded, topographic contours could be viewed from above as a spatiotemporal plot (Fig. 1). We now recognize these plots as a characteristic of HRM. The concept of high resolution manometry (HRM). Closely spaced recording sensors on an esophageal motility catheter (A) generate multiple recordings throughout the esophagus (B). Dashed arrows point to pressure recordings from individual sensors. Computer software fills in best fit data between the recording sensors 1 cm apart, and color codes amplitude levels (C). Finally, the image is smoothed out electronically, and displayed as a topographic contour plot (D) representing the peristaltic sequence when viewed from above. The contour plots are termed Clouse plots in honor of Ray Clouse, who developed HRM. Next, Clouse worked on streamlining the process of data acquisition. Collaboration with Dentsleeve resulted in a 0.4 cm extruded, 21 lumen silicon water perfused catheter, and complementary software was developed by Medical Measurement Systems (MMS, Enschede, Holland).2,3 The manometry procedure remained cumbersome, the pull through maneuver had not been eliminated, and only 75–80% of the esophagus could be interrogated at a time. Nevertheless, there were significant advances in our understanding of esophageal peristalsis, which was now shown to consist of a chain of contracting segments separated by troughs.4 We quickly learned that esophageal smooth muscle consisted of not one but two contracting segments.5 These segments merged together in hypercontractile states, and demonstrated wide troughs and low amplitudes in hypomotility disorders.4–6 We also learned that esophageal shortening could move the lower esophageal sphincter (LES) proximal to even sleeve LES sensors, and that HRM provided higher accuracy in achalasia diagnosis because LES excursion could be followed and abnormal relaxation documented despite this shortening.7,8 Many motor disorders were associated with recognizable HRM patterns, and diagnoses could be made with just pattern recognition in many instances. But the system was not yet optimal for widespread clinical use, and more work is needed to be done. As technology progressed toward solid state pressure sensors, Clouse found a key collaborator in Thomas Parks, PhD, who formed a new company, Sierra Scientific, Inc. to advance the field. The new millennium heralded a collaborative effort which culminated in the development of a solid state catheter, with 36 high fidelity circumferential sensors.9 The stationary pull through maneuver was now obsolete, as the entire esophagus from pharynx to stomach could be viewed real time. New software programs were written, and an electronic sleeve was developed to interrogate LES post swallow residual pressures (ManoView™, eSleeve™, Sierra Scientific, Inc., Los Angeles, CA, USA).9,10 These baby steps in the early 2000s have been augmented exponentially in the past 5 years, as HRM technology moved from St. Louis to Chicago and beyond.11,12 HRM systems are now available from a handful of companies, for not just esophageal manometry (sometimes combined with stationary impedance), but also anorectal, colonic and antroduodenal manometry. An even higher definition technique (3D HRM) uses tactile sensors, and has been introduced for anorectal manometry; it is being researched for detailed interrogation of esophageal sphincters.13,14 The following articles only begin to describe the potential this new technology has uncovered in the evaluation of gut motility. Ray Clouse was a remarkable innovator, with the ability to conceptualize in an abstract and geometric fashion, traits that almost took him to a career in architecture.15 He developed HRM to simplify esophageal manometry, improve its clinical utility, and to develop uniformity in data collection and analysis. He envisioned that HRM would make a major impact on clinical and research fronts within esophagology (Table 1), but passed away from terminal cancer before he could fully appreciate the impact of his innovation. The direction HRM has taken in recent years, especially the new clinical classification scheme debuted in this supplement,16 fulfills many of Clouse’s original intent, and would have pleased him immensely. It is only fitting that the HRM plots are now universally termed ‘Clouse plots’ in his honor. This is the Ray Clouse legacy.