Oesophageal wall stretch: the stimulus for distension induced oesophageal sensation

Recently, we reported a novel ultrasound technique to assess the biomechanical properties of the oesophagus in humans. To investigate whether the oesophageal sensation induced by oesophageal distension correlates with wall tension, wall stress or wall strain, we studied 20 healthy subjects using a manometry catheter equipped with a high-compliance bag and a high-frequency intraluminal ultrasound probe. Oesophageal distensions were performed by injecting 1-20 mL water into the bag for 20-30 s. Subjects scored the nature (heartburn or chest pain) and severity of sensation in response to distension, before and after atropine (15 microg kg(-1), i.v.). Ultrasound images of oesophagus were digitized and measurements were made to calculate oesophageal wall tension, stress and strain during distensions. Subjects experienced mostly heartburn, not chest pain, in response to oesophageal distension. Oesophageal wall strain and bag pressures correlated best with the oesophageal sensation. Atropine reduced bag pressure but did not affect the distension induced heartburn and chest pain. We conclude that heartburn is a common sensation in response to oesophageal distension in normal subjects. A strong correlation between wall strain and oesophageal sensation suggests that the wall stretch is the stimulus for nociceptive mechanoreceptors of the oesophagus.