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

Abstract  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.