Assessment of 24‐h oesophageal pH monitoring should be divided to awake and asleep rather than upright and supine time periods*

Oesophageal acid exposure analysis is divided to upright and supine, based on the assumption that the supine-awake period is similar to the supine-asleep period. To determine if the principal acid-reflux characteristics of supine-awake are closer to supine-asleep or upright period. Patients with heartburn underwent an upper endoscopy and pH testing. The patients were instructed to carefully document their upright, supine-awake and supine-asleep periods. A total of 64 patients were enrolled into this study (M/F 35/29; mean age 52.4 +/- 13.3). The mean percentage total time pH <4, frequency of acid-reflux events (per h) and number of sensed reflux events was not different between upright and the supine-awake period (P = ns). In contrast, the mean percentage total time pH <4, frequency of acid-reflux events and number of sensed reflux events was significantly higher in both upright and supine-awake periods vs supine-asleep (4.3 +/- 6.9, 1.86 +/- 2.7 and 0.01 +/- 0.05, P < 0.0001, respectively). The principal characteristics of the acid-reflux events in the supine-awake period are closer to the upright period than to the supine-asleep period.