Equipment Preparation

HRM catheters are made by several manufacturers, and can be either solid-state or water-perfused. Manufacturer instructions need to be followed for catheter calibration before initiation of the study. Water-perfused catheters need to be flushed with degassed water, and pressure measurements calibrated to the zero position, which is, the level of the esophagus with the patient lying on the stretcher. With solid-state catheters, pressure calibration is performed before each study by applying known pressure to pressure sensors to ensure pressure readings are accurate; this is typically an automated process using a pressurized chamber into which the catheter is inserted. Because solid-state sensors can be affected by temperature, intermittent calibration using a water bath at 37°C is recommended, so that a pressure correction can be calculated for pressures recorded at body temperature when calibration is performed at room temperature. This thermal compensation is applied at the end of the procedure.

Supplies needed for esophageal manometry include syringes with distilled or tap water for test swallows, a cup with a drinking straw containing water, a kidney tray and towels in case the patient retches or vomits, cotton-tipped swabs, KY jelly for catheter lubrication, lidocaine jelly for topical anesthesia of the nasal passages, and tape for securing the catheter after intubation. If viscous or solid boluses are to be administered, appropriate food items (eg, viscous jelly, yogurt, bread, marshmallows) need to be at hand.

Some manufacturers of HRM catheters recommend using a protective sheath over the solid-state catheter to simplify disinfection protocols between procedures; these cannot be used with catheters containing impedance sensors.

Patient Preparation

Esophageal manometry is best performed in a well-lit room with a comfortable ambience. The patient changes into a gown that covers the chest and torso. Preprocedure symptom questionnaires and requisition forms are completed as the catheter and equipment are readied. The HRM operator first explains the procedure to the patient, and describes why the procedure is being performed. The operator reassures and engages the patient, describes what the patient can expect, and uses distractive measures in case there is oropharyngeal discomfort or gagging. Knowledge of anatomic abnormalities, such as hiatal hernia, suspicion of a dilated esophagus, and prior foregut surgery, may assist in preparing for and performing the procedure.

Patients should have nothing to eat or drink for at least 6 hours (clear liquids for 2–3 days may be needed if achalasia is suspected) before the HRM study to prevent aspiration of gastric or esophageal contents. Medications that affect esophageal motility (caffeine-containing medications, prokinetics, nitrates, calcium-channel blockers, anticholinergics, opiates, and tricyclic antidepressants) are best avoided whenever possible, and should be decided on a case-by-case basis in the context of the clinical indication for the study and potential impact on patient management. Allergies to analgesics must be documented, as topical anesthesia with lidocaine spray and/or viscous lidocaine is used in the nasal passages in many centers to minimize discomfort and maximize the success of nasal intubation.

Patient Positioning

The esophageal motility catheter is best inserted with patients sitting upright and facing the operator. The head is tilted up slightly to allow the operator to visualize the nasal passages before insertion. After adequate positioning of the catheter, the patient is asked to lie down in a supine position, as esophageal peristalsis is traditionally assessed without the effect of gravity on bolus transit. Furthermore, with conventional manometry using pneumohydraulic pumps, pressure needed to be zeroed to the position of the catheter, which required a horizontal position. The head end of the bed is typically tilted upward by 10° to 15°, and the patient is asked to lean slightly to the left to assist with swallowing of water boluses that are squirted into the mouth.

Upright patient positioning is now possible using HRM, as zeroing of pressure to patient position is not necessary. The upright, seated position may be better tolerated by patients with severe esophageal dysmotility, thereby minimizing the risk of regurgitation and aspiration in comparison with the supine position. Normative upright pressure values exist, and have been compared with the supine position. Peristalsis is more coordinated and vigorous, with a slower contraction front velocity in the supine position. Motor diagnoses are reported to be generally concordant in more than 70% of cases between supine and upright positions; discordant cases were mostly accounted for by an excess of hypomotility disorders in the upright position. However, numeric reduction in IRP and contraction vigor is seen in the sitting position, with others reporting reclassification of esophageal outflow obstruction in approximately 10%, leading some investigators to suggest performing up to 5 swallows in the upright position in most patients.

Catheter Insertion

A cup containing water, with a straw for sipping, is provided to the patient, as swallowing of water during catheter advancement reduces patient discomfort. The catheter tip is lubricated and passed through the nasal passages with the chin tilted slightly upward. When the patient feels the catheter at the back of the throat, the neck can be flexed and the catheter inserted into the esophagus while the patient takes small sips of water to maintain relaxation of the UES and, subsequently, the LES. Having patients open their mouths, watch the Clouse plots on the screen, or squeeze a soft ball can help focus attention away from discomfort or gagging.

Catheter Positioning

When properly positioned, the HRM catheter extends from the pharynx to the stomach, with at least 1 sensor in the pharynx and 3 sensors in the stomach. In the normal setting, the UES and LES/esophagogastric junction (EGJ) are visible as 2 bands of pressure ( Fig. 2 ). The HRM operator is trained in identification of anatomic landmarks, including the UES, LES, and diaphragmatic crural impression. The diaphragmatic crural impression together with the LES constitutes the EGJ. The location of the diaphragmatic crura can be assessed by identifying pressure inversion with respiration; intrathoracic pressure is more negative during inspiration, whereas intra-abdominal pressure is more negative during expiration (see Fig. 2 ). If the diaphragmatic crural impression is not easily identified, the patient can be asked to take a deep breath, which will magnify these pressure changes. If the EGJ is not traversed by the HRM catheter, these pressure changes with breathing will not be seen; instead, a “butterfly” or mirror image may be seen, indicating that the catheter is curled up in the esophagus and requires repositioning ( Fig. 3 ). Separation between the LES and diaphragmatic crura indicates the presence of a hiatus hernia.

Relationships between LES and esophagogastric junction (EGJ). ( A ) Normal EGJ (type I), with overlapping LES and diaphragmatic crura, and no separation between the two. ( B ) Type II hiatus hernia (HH) in which LES and diaphragmatic crura are not overlapping, but separation is less than 2 cm. ( C ) Type III: separation between LES and diaphragmatic crura; in this instance, the diaphragmatic crura have not been traversed. ( D ) LES is not traversed. When in doubt, this can be recognized when the patient is asked to swallow. D, diaphragm; E, esophagus.

Butterfly patterns generated by curling of the catheter in the esophagus or within a hiatus hernia. Arrows point to site where the catheter curls back up. ( A ) The catheter is curled up in the esophageal body in a patient with achalasia, with mirroring of esophageal body contraction above and below where the catheter curls. ( B ) The catheter traverses the LES and curls up within a hiatus hernia, with retrograde movement back up into the esophagus through the LES.

If a pressurization pattern is seen that extends from the contraction front all the way to the bottom of the screen, air may be present in the catheter sheath if the Given HRM system is being used. The operator should remove the catheter and replace the sheath if the tracing looks unusual.

An inability to traverse the LES is a critical imperfection that needs to be recognized by the HRM operator in real time. Although this difficulty occurs most often in achalasia, the diagnosis of achalasia may still be made with similar frequency (up to 94%) as with perfect studies if the clinical context and other tests are reviewed. Straightening and lengthening the esophagus by asking the patient to stand up, repositioning the catheter, or having the patient gulp water (which may allow the LES to relax) may help maneuver the catheter through the LES. Regardless, several maneuvers can be used to attempt to traverse the LES ( Box 2 ).

By contrast, not traversing the diaphragmatic crura is a noncritical imperfection. This difficulty typically occurs with large hiatal hernias. In this setting, if the LES is traversed there remains a small risk that LES metrics may be inaccurate if there is pressure compartmentalization within the hiatal hernia. However, esophageal body peristalsis and LES function can typically be ascertained adequately. Insertion with the patient standing up may assist with traversing the diaphragm, as the hiatus hernia may reduce in this position. Alternatively, placing the HRM catheter under endoscopic guidance can be considered.

Once the resting pressures generated by the UES and LES are identified, the catheter is fixed in place by taping to the nose, and the patient is allowed to accommodate to the HRM catheter before initiating the study. This interval avoids artificial elevations of resting UES pressure and repeated dry swallowing.