Figure 6 - Simultaneous manometry and fluoroscopy of barium swallow in a normal subject.

Fluoroscopy shows that on swallowing, the barium column moves down the esophagus. Such barium movement occurs largely due to passive forces in the esophagus and is very marked in the upright position. The tail of the barium column moves down the esophagus by the peristaltic contraction. Note that the onset of peristalsis corresponds with the tail of the barium column. Also note that onset of peristaltic contraction at level 1 occurred at 8.5 sec after a swallow, at which time the barium column is pushed down to the lower 1 cm of the esophagus. (Source: Modified from Dodds WJ, Christensen J, Dent J, Arndorfer RC, Wood JD. Pharmacologic investigation of primary peristalsis in smooth muscle portion of opossum esophagus. Am J Physiol 1979;237(6):E561–E566, with permission from the American Physiological Association.)