The effect of a sitting vs supine posture on normative esophageal pressure topography metrics and Chicago Classification diagnosis of esophageal motility disorders

Abstract

Background: Although, the current protocol for high resolution manometry (HRM) using the Chicago Classification is based on the supine posture, some practitioners prefer a sitting posture. Our aims were to establish normative esophageal pressure topography data for the sitting position and to determine the effect of applying those norms to Chicago Classification diagnoses.

Methods: Esophageal pressure topography studies including test swallows in both a supine and sitting position of 75 healthy volunteers and 120 patients were reviewed. Integrated relaxation pressure (IRP), distal contractile integral (DCI), contractile front velocity (CFV), and distal latency were measured and compared between postures. Normative ranges were established from the healthy volunteers and the effect of applying sitting normative values to the patients was analyzed.

Key results: Normative values of IRP, DCI, and CFV all decreased significantly in the sitting posture. Applying normative sitting metrics to patient studies [27% reduction in IRP (15 to 11 mmHg), 69% reduction in DCI (8000-2500 mmHg-s-cm)] reclassified 13/120 (11%) patients as having abnormal esophagogastric junction relaxation and 26/120 (22%) as hypercontractile. Three patients with an abnormal supine IRP normalized when sitting with elimination of a vascular artifact.

Conclusions & inferences: Clinical HRM studies should include both a supine and sitting position to minimize misdiagnoses attributable to anatomical factors. However, until outcome studies demonstrating the significance of isolated abnormalities of IRP or DCI in the sitting position are available, the Chicago Classification of esophageal motility disorders should continue to be based on supine swallows using normative data from the supine posture.

Figure 1

Examples of the effect of changing the IRP cutoff value on Chicago Classification diagnosis. Panels A and B were swallows from the same patient in supine (left) and sitting (right) position. The mean IRP was 19.5 mmHg in the supine posture but only 7.9 mmHg in the sitting position making the Chicago Classification diagnosis EGJ outflow obstruction when based on the supine position or weak peristalsis when based on the sitting position. Similarly, the patient in Panels C and D was reclassified as EGJ outflow obstruction in the sitting position due to the increased of mean IRP to greater than 11 mmHg. Panels E and F illustrate a patient in whom EGJ outflow obstruction would be diagnosed in only in the sitting posture due to the lower cutoff value in IRP (11 mmHg).

Figure 2

Individual patients with discordant normal/abnormal mean IRP values depending on whether the supine or sitting cutoff values were applied. Seven patients were borderline abnormal cases when studied supine (blue) that became abnormal in the sitting posture based on the lower cutoff of abnormality (11 mmHg). Six patients had an IRP increase in the sitting position attributable to a vascular artifact or hiatus hernia (green). There were an additional 3 patients with elevated supine values and normal sitting values secondary to vascular artifact or hiatus hernia only in the supine position (black).

Figure 3

Effect of the DCI cutoff value on Chicago Classification diagnosis. Panels A and B were swallows obtained from the same patient in supine (left) and sitting (right) position. Hypercontractility was diagnosed based on the DCI greater than 8000 mmHg-s-cm in the supine position; the diagnosis was not changed in the upright position applying the cutoff value of 2500 mmHg-s-cm, although the maximal DCI changed from 14496 to 5731. Panels C and D illustrate a patient with normal peristalsis in the supine position with the maximal DCI of less than 5000 mmHg-s-cm and hypercontractile esophagus in the sitting position with the maximal DCI of 9390 mmHg-s-cm.

Figure 4

Individual patients with discordant normal/abnormal maximal DCI values depending on whether the supine or sitting cutoff values were applied. One patient (blue) was reclassified as hypercontractile in the sitting posture due to the increase of maximal DCI to greater than 8000 mmHg-s-cm. Twenty-five patients were reclassified as “hypercontractile” in the sitting position due to the change of cutoff value (black). Three patients were diagnosed with hypercontractile esophagus in both the supine position and sitting position (green).