Impact of nadir lower oesophageal sphincter pressure on bolus clearance assessed by combined manometry and multi-channel intra-luminal impedance measurement.

This study aimed to assess the relationship between nadir lower oesophageal sphincter pressure (LOSP) and wave amplitude (WA) in oesophageal bolus clearance. Concurrent oesophageal manometry and impedance were performed in 146 subjects [41 healthy, 24 non-obstructive dysphagia (NOD) and 81 gastro-oesophageal reflux (GOR)]. Patients with achalasia and diffuse oesophageal spasm were excluded. Swallow responses were categorized by nadir LOSP. For each category of nadir LOSP, WA at the distal 2 recording sites were grouped into bins of 10 mmHg and the proportion of waves in each bin associated with a normal bolus presence time (BPT) was determined. Nadir LOSP, distal BPT, total bolus transit time and the proportion of impaired oesophageal clearance in patients with NOD were greater than those of healthy subjects and patients with GOR. Overall, responses with impaired oesophageal clearance had significantly lower WA (54 +/- 1 vs 81 +/- 1 mmHg; P < 0.0001) and higher nadir LOSP (2.7 +/- 0.4 vs 1.0 +/- 0.1 mmHg, P < 0.001). For each level of nadir LOSP, there was a direct relationship between distal WA and successful bolus clearance of both liquid and viscous boluses from the distal oesophagus. As nadir LOSP increased, the relationship between WA and bolus clearance shifted to the right and higher amplitudes were required to achieve the same effectiveness of clearance. Hypotensive responses with nadir LOSP > or = 3 mmHg were less likely to clear than those with nadir LOSP < 3 mmHg, for both liquid (7/29 vs 162/276; P < 0.001) or viscous boluses (11/46 vs 176/279; P < 0.0001). Nadir LOSP is an important determinant of bolus clearance from the distal oesophagus, particularly in patients with NOD.