Transient lower esophageal sphincter relaxation (TLESR) is the major contributor to esophageal acid exposure during the day. At night, the major contributor is reflux during absent basal lower esophageal sphincter (LES) pressure. R.C.H. Scheffer, MD, and colleagues investigated the relationship between esophageal acid exposure time and the underlying manometric motor events in patients with gastroesophageal reflux disease (GERD). Postprandial esophageal motility and pH were evaluated in 31 patients. Additionally, 10 patients underwent 24-hour ambulatory manometry and pH recording.

In the 3-hour postprandial study, there were 367 reflux episodes; 79% were associated with TLESR, 14% with absent basal LES pressure, and 7% with other mechanisms. These results represented 62%, 28%, and 10% of the acid exposure time, respectively. Acid reflux duration per motor mechanism was longer for absent basal LES pressure than for TLESR (189 ± 23 sec and 41 ± 5 sec, respectively; P <.001).

In the 24-hour ambulatory study, the contributions of TLESR to reflux frequency compared with acid exposure time were 65% versus 54% interprandially and 74% versus 53% postprandially. During the night, absence of basal LES pressure accounted for 36% of reflux events, representing 71% of acid exposure time. These results suggested that the duration of esophageal acid exposure after TLESR is shorter than reflux during absent basal LES pressure. (The findings were reported in Neurogastroenterology and Motility, October 2005.)