1.   Common cavity episodes have been described and evaluated in detail elsewhere, and have been shown by fluoroscopy to be due to oesophageal body distention with gas.

2.   Common cavity episodes were only scored when the rise in intra-oesophageal pressure was recorded in at least two oesophageal body manometric channels.

3.   The percentage of time that such a pattern was seen during common cavity episodes was recorded.

4.   The change of basal end expiratory intraoesophageal pressure produced by a common cavity episode was measured from an oesophageal body channel.

5.   The extent of an esophageal common cavity was determined from the number of sideholes proximal to the LOS that registered the common cavity episode.

6.   For relaxations that occurred during common cavity episodes, the reference basal UOS pressure was derived from the UOS pressure values during the common cavity.

7.   The nadir of transient UOS relaxation swas the most clearcut point and so was related to the time of onset of the common cavity episode to the nearest second.

8.   Nadir pressure was referenced to the prevailing midoesophageal body pressure in that second and so took into account changes of basal oesophagela body pressure produced by common cavity episodes.

9.   The pH changes associated with each common cavity episode were evaluated by taking the pH five seconds before and five seconds after the onset of the common cavity episode.

10.   The pH nadir during the common cavity episode was also noted.