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, 52 (6), 784-90

Relevance of Ineffective Oesophageal Motility During Oesophageal Acid Clearance

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Relevance of Ineffective Oesophageal Motility During Oesophageal Acid Clearance

M Simrén et al. Gut.

Abstract

Background: Oesophageal clearance of acid reflux consists of an initial volume clearance followed by neutralisation of the acidified mucosa by swallowed saliva (chemical clearance). Ineffective oesophageal motility (IOM), a frequent finding in patients with gastro-oesophageal reflux disease (GORD), has been claimed to underlie prolonged acid clearance by affecting oesophageal emptying and saliva transport. Intraluminal impedance allows non-radiological monitoring of movement of oesophageal liquids.

Aims: To evaluate the relevance of IOM during oesophageal volume and chemical clearance using combined pH impedance measurements.

Subjects: Impedance was validated with fluoroscopy to study volume clearance in three healthy subjects. Acid clearance tests were performed in 10 healthy subjects in the upright and supine positions, before and after oesophageal peristaltic disruption with sildenafil 50 mg.

Methods: After instillation of an acid bolus, simultaneous manometry, pH, and impedance were used to study oesophageal motility, chemical clearance, and volume clearance, respectively.

Results: Impedance allowed assessment of volume clearance accurately, showing a strong correlation with fluoroscopy (r(2)=0.89). Sildenafil provoked a graded impairment in oesophageal motility in healthy subjects without affecting saliva secretion. In the upright position, volume clearance was slightly prolonged only with severe IOM (>80% abnormal peristaltic sequences). In the supine position, severe IOM significantly prolonged chemical and volume clearance. Moderate IOM (30-80% abnormal peristalsis) had no effect. With normal peristalsis and moderate IOM, clearance times were similar in the upright and supine positions. Severe IOM however had a greater impact on clearance in the supine than in the upright position.

Conclusion: Ineffective oesophageal motility has little effect on oesophageal clearance during upright acid reflux. With supine reflux, only severe IOM is associated with prolonged oesophageal clearance.

Figures

Figure 1
Figure 1
Schematic representation of the recording assembly. Oesophageal pH and impedance were measured 5 cm proximal to the lower oesophageal sphincter (LOS) to calculate chemical and volume clearance.
Figure 2
Figure 2
Validation of oesophageal impedance for assessment of volume clearance. Fluoroscopic imaging and oesophageal impedance were recorded concurrently during barium swallows. An impedance segment was positioned 5 cm proximal to the lower oesophageal sphincter (LOS). During barium swallows fluoroscopic imaging, impedance recording, and a digital timer were simultaneously displayed on a single screen. The following parameters were compared: (a) time to complete filling with barium of the oesophageal segment; (b) time to complete disappearance of barium from the oesophageal segment; (c) time to 50% drop in impedance relative to the pre-swallow baseline; and (d) time to return of impedance to 50% of baseline
Figure 3
Figure 3
Scattergram describing the relationship between volume clearance time of a swallowed barium bolus as measured by videofluoroscopy and oesophageal intraluminal impedance.
Figure 4
Figure 4
Tracings of concurrent oesophageal manometry, pH, and intraluminal impedance before (basal) and 15 minutes after administration of sildenafil. During the clearance tests, acid bolus instillation induced immediate pH and impedance drops. Acid instillation was followed by on-demand swallow induced normal peristaltic waves. Under basal conditions, chemical clearance was detected as a stepwise recovery of oesophageal pH and volume clearance as a faster recovery of oesophageal impedance. After sildenafil, oesophageal contractions in the mid and distal oesophagus almost disappeared, provoking little effect on clearance in the upright position but a significant delay in both chemical and volume clearance in the supine position.
Figure 5
Figure 5
Correlation between the proportion of abnormal peristaltic sequences and clearance times in the upright position (pooled data).
Figure 6
Figure 6
Volume clearance in the upright and supine positions with increasing severity of ineffective oesophageal motility (IOM) in seven subjects who all had three levels of impairment of oesophageal motility. *p<0.05, **p<0.01.
Figure 7
Figure 7
Chemical clearance in the upright and supine positions with increasing severity of ineffective oesophageal motility (IOM) in seven subjects who all had three levels of impairment of oesophageal motility. **p<0.01.
Figure 8
Figure 8
Correlation between the proportion of abnormal peristaltic sequences and clearance times in the supine position (pooled data).

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