We aimed to model esophageal bolus
transit based on esophageal pressure topography (EPT) landmarks,
concurrent intrabolus pressure (IBP), and esophageal diameter as
defined with fluoroscopy. Ten healthy subjects were studied with
high-resolution impedance manometry and videofluoroscopy. Data
from four 5-ml barium swallows (2 upright, 2 supine) in each subject
were analyzed. EPT landmarks were utilized to divide bolus transit
into four phases: phase I, upper esophageal sphincter (UES) opening;
phase II, UES closure to the transition zone (TZ); phase III, TZ to
contractile deceleration point (CDP); and phase IV, CDP to completion
of bolus emptying. IBP and esophageal diameter were analyzed
to define functional differences among phases. IBP exhibited distinct
changes during the four phases of bolus transit. Phase I was associated
with filling via passive dilatation of the esophagus and IBP reflective
of intrathoracic pressure. Phase II was associated with auxotonic
relaxation and compartmentalization of the bolus distal to the TZ.
During phase III, IBP exhibited a slow increase with loss of volume
related to peristalsis (auxotonic contraction) and passive dilatation in
the distal esophagus. Phase IV was associated with the highest IBP
and exhibited isometric contraction during periods of nonemptying
and auxotonic contraction during emptying. IBP may be used as a
marker of esophageal wall state during the four phases of esophageal
bolus transit. Thus abnormalities in IBP may identify subtypes of
esophageal disease attributable to abnormal distensibility or neuromuscular
dysfunction.