Manometry study technique and protocol
The HRM assembly
High‐resolution manometry assemblies are commercially available through several different manufacturers, each with proprietary analysis software to generate EPT plots and facilitate analysis. Regardless of manufacturer, each HRM assembly entails 30–36 pressure sensors spaced 1–2 cm apart incorporated into a flexible catheter. Because differences in catheter and pressure‐sensor technologies affect the performance characteristics of the device, it is important that clinical interpretation should be based upon normative values generated with the specific apparatus utilized. These differences in performance are particularly relevant with measurement of deglutitive lower esophageal sphincter (LES) relaxation, i.e. the integrated relaxation pressure (IRP); see Table 8.1 [8].
Table 8.1 Normal values by HRM assembly manufacturer. Values reflect 5 ml liquid bolus swallows performed in the supine patient position.
Source: Based on Herregods, Roman, Kahrilas, et al. [8].
| HRM | Sierra‐vintage | MMS – Unisensor AG | Sandhill – Unisensor AG | Starlet – Unisensor AG |
|---|---|---|---|---|
| N, asymptomatic controls | 75 [22, 33, 35] | 52 [94] | 69 [95] | 97 [96] |
| IRP (mmHg) 95th percentile | 15 | 28 | 23.5 | 20 |
| Basal EGJ pressure * (mmHg) 5th–95th percentile | 5–32 | 9–51 | 8–62 | 15–48 |
| DCI (mmHg•s•cm) 5th–95th percentile | 448–4721 | 186–3408 | 606–4998 | 1413–6844 |
| Distal latency (seconds) 5th percentile | 4.3 | 5 | 5.1 | 5.8 |
* At end‐expiration.
High‐resolution impedance manometry (HRIM) catheters additionally incorporate serially spaced impedance channels, generally with 2 cm spacing. Impedance measurements relate to the content of the esophagus such that impedance decreases with intraluminal liquid and increases with intraluminal air. Hence, high‐resolution impedance recordings can detect the entrance of an esophageal bolus by a decrease in impedance and bolus clearance when the impedance signal returns to baseline [9]. Utilization of HRIM then provides a method to objectively assess bolus transit, bolus clearance, intrabolus pressure, and relationships between esophageal pressure and bolus flow [10–13]. However, despite this additional information, the clinical utility of impedance manometry beyond what is learned from HRM remains a topic of debate. Further discussion of the utilization of HRIM follows.
Patient selection and preparation
Since a primary objective of HRM is to detect primary esophageal motor disorders, it should follow an evaluation for mechanical obstruction (e.g. stricture, severe erosive esophagitis, large hiatal hernia, tumor). While identification of any of these often negates the need for esophageal manometry, if manometry is completed, the interpretation should so specify, reporting any findings as secondary motor findings. Previous foregut surgery (e.g. fundoplication, adjustable gastric band, LES‐myotomy, etc.) may also induce secondary motor abnormalities, making the surgical history an essential element of the interpretation. Similarly, medications such as anticholinergics, nitrates, calcium channel blockers, and opioids can have effects on esophageal motility [14, 15]. Hence, a medication list should be reviewed prior to manometry, and, if possible, non‐essential medications with potential for impact on esophageal motility should be held prior to manometry.
The manometry test is performed after at least a 6 hr fast; longer fasting periods or a liquid diet for one or two days prior to the manometry should be considered in patients with suspected achalasia or significant esophageal retention. Immediately prior to the manometry test, the manometry assembly should be calibrated according to manufacturer instructions. All test materials should be organized within close reach; this includes tape strips to secure the manometry catheter, substances for test swallows (liquid, bread) and delivery (syringe, straw), and also an emesis basin (cough, gagging, spitting, and vomiting sometimes occur). The patient’s chest should be covered with a chux pad or gown. We have the patient hold a cup of water with a straw to drink from, to assist in placing the manometry catheter.
Manometry catheter placement
Transnasal intubation of the manometry catheter is often the least pleasant component of the test for patients. Patients should be asked if they have a preference for which nostril to place the catheter, as anatomic conformation (e.g. deviated septum) or other factors such as piercings may make one side preferable to the other. A topical anesthetic (e.g. 2% lidocaine jelly) should be applied to the inside of the nostril, aided by a cotton‐tipped swab; instructing the patient to sniff deeply while the swab is in place can help further anesthetize the nasal passage.
The tip of the manometry catheter should then be lubricated and slowly passed through the nasal passage. As the catheter reaches the nasopharynx, we instruct the patient to start taking small sips of water while the catheter continues to be slowly advanced. Having the patient tuck their chin may aid passage as well. Some mild resistance may be encountered with passage through the pharynx, but if passage through one nare is difficult, the alternate nare can be anesthetized and placement reattempted. Once the upper esophageal sphincter (UES) is traversed, the catheter should be advanced until the HRM catheter traverses the EGJ by 3–5 cm, which can be visualized in real time on the EPT display. Correct catheter placement traversing the EGJ is paramount to accurately assess EGJ pressures. Positioning of the HRM catheter across the diaphragmatic hiatus can be confirmed by identifying the pressure inversion point: the point at which the negative intra‐thoracic pressures associated with inspiration inverts to the positive intra‐abdominal pressure. Instructing the patient to take several deep breaths or perform a straight leg raise can improve identification of the pressure inversion point by exaggerating intra‐thoracic and intra‐abdominal pressures as well as augmenting the EGJ pressure.
In certain scenarios, adequate placement of the manometry catheter may not be possible. This can occur with abnormal esophageal anatomy, e.g. achalasia with tortuous esophagus and non‐relaxing LES, or with some patients unable to tolerate awake transnasal intubation despite topical anesthetic. In these situations,