Sensation and distribution of stress and deformation in the human oesophagus

Evaluation of the distribution of stresses and strains in relation to distension-induced sensation in the human oesophagus is valuable for understanding oesophageal biomechanics and mechano-sensation. In 12 healthy volunteers a specially designed oesophageal bag containing an endoscopic ultrasound probe was inflated to the moderate pain level. Ultrasound images, bag pressure and perceived sensation were recorded before and after pharmacological relaxation of the smooth muscle with butylscopolamine. The oesophagus was assumed to be circular and thick-walled. Distension induced a tensile circumferential stretch, radial compression and longitudinal shortening. Both circumferential strain and stress were highest at the mucosal surface and decreased throughout the wall. The stiffness increased throughout the wall and was highest at the outer surface (P < 0.001). The decrease in stiffness in response to butylscopolamine was non-significant. The infused volume (P = 0.012) and circumferential stress (P < 0.001) were most closely associated with the distension-induced sensation (adjusted R2 = 0.88). The perceived sensation was highly individual but was unaffected by butylscopolamine (P > 0.08). The present study provides a method for computation of the stress-strain distribution throughout the wall and the mechano-sensory interaction in the human oesophagus. In the future, this may be useful for understanding of mechanoreceptor responses and generation of symptoms in visceral organs in health and in disease.