and Development of HRM: The Way It Works

Fig. 4.1

In the conventional manometry intraluminal pressures are recorded from widely spaced sensors (3- to 5-cm). (a) In this two-dimensional display pressure is on the y-axis, time is on the x-axis, and pressure tracings are stacked vertically. (b) Tracings are displayed three-dimensionally: pressure remains on the y-axis and time on the x-axis but sensor position is on the z-axis with the gastric sensor at the front and the pharynx sensor at the back

../images/475577_1_En_4_Chapter/475577_1_En_4_Fig2_HTML.png — Fig. 4.2

(a) Application of pressure contour lines with isobaric pressure lines (5-mmHg). Colors are linked to a specific color profile plot: cooler colors for lower pressures and warmer colors for higher pressures. (b) Esophageal manometry: The definitive and commonly used display obtained by rotating plot until the direction of eyes is parallel to y-axis. Pressure axis (y) collapses and it is replaced by a color contour for a handier two-dimensional surface

Using such a novel computerized plotting method, the pressure changes are viewed from clinically useful and visually attractive three-dimensional graphic displays rather than as a series of isolated waves [9, 10]. Considerations of both time and space relationships of pressure data acquired from intraluminal recording have revealed more accurate information regarding the direction of the wave movement, and the evaluation of all pressure events occurring over a length of studied organ has revealed more information about the neuromuscular mechanisms involved in local motility [10]. Moreover, the developed system requires no manipulation or summation of the pressure data, thus enabling to determine abnormalities identified in isolated time windows that may not be occurring “on the average,” and provides a simplified and rapid method of analyzing pressure data from several visual perspectives.

Overall, with the advent of high-resolution manometry, the pressure sensors are closely spaced, and the overall number of pressure sensors is increased. With these modifications, much more information can be acquired, as data are not lost in the gaps that are typically present in a conventional catheter, which typically has 4–8 pressure sensors placed 3–5 cm of each other. Moreover, this novel technology provides color-countered topographic plots based on amplitude, distance, and time, depicting a continuum of dynamic pressure changes along lengths and time; data are presented in a simplified manner, in contrast to the use of linear plots of amplitude signals alone in conventional manometry.

Over time, the most intuitive visualization, that is commonly used today during manometric examinations, has become more and more established. This kind of visualization (Fig. 4.2b) has been obtained by rotating plot so that the operator looks down on it from directly above, with the direction of his/her eyes parallel to y-axis. In this way the pressure axis (y) breaks down and instead of a three-dimensional color contour we obtain a handier two-dimensional surface in which pressure is represented by colors. At this point sensor location is on the y-axis, and time is on the x-axis [7]. These novel techniques have already proven useful in both research and clinical settings, giving greater insight into normal and abnormal motor function than conventional manometric methods [11].

Although these measurement and analysis methods were first used in the esophagus, they are applicable in other parts of the gastrointestinal tract. High-resolution anorectal manometry (HRAM) was introduced in 2008, followed by high-definition anorectal manometry (HDAM), to achieve more precise measurements of anorectal pressure using densely arranged catheter sensors, and thus, to improve our diagnostic yield for anorectal disorders [12–14]. Indeed, whereas the conventional catheters have 4–8 unidirectional sensors, HRAM or HDAM catheters have multiple pressure sensors that straddle the entire anal canal and more proximal sensors inside a balloon placed in the rectum. Therefore, HRAM and HDAM catheters provide better spatial resolution of the sphincter pressure profile than conventional catheters. Station pull-through maneuvers are not required, which minimize movement related artifacts and shorten the procedure duration (Fig. 4.3) [7]. Furthermore, even if a contraction can occur with an upward displacement (e.g., during bearing down), the spatial resolution of the catheter allows the register also this event, providing more information. Also, there is now the theoretical possibility to test patient in the defecatory position, permitting new insights in a more physiological way.