Mj. Li et al., ANALYSES OF NORMAL AND ABNORMAL ESOPHAGEAL TRANSPORT USING COMPUTER-SIMULATIONS, The American journal of physiology, 266(4), 1994, pp. 70000525-70000543
Mathematical modeling and computer simulations are combined with concu
rrent manometric and videofluoroscopic data to analyze the contractile
behavior of the esophageal wall during normal and abnormal esophageal
bolus transport. The study focuses on axial variations in intralumina
l pressure in relationship to deformations of the esophageal wall duri
ng the transport process. Four case studies of esophageal bolus transp
ort described by Kahrilas et al. (Gastroenterology 94: 73-80, 1988), o
ne normal and three abnormal, are analyzed in detail by capturing the
major elements of both the videofluoroscopic and concurrent manometric
data in the mathematical model. In all cases a strong correlation bet
ween the deformations of the luminal wall and the axial variations of
intraluminal pressure is observed. Simulation of normal bolus transpor
t shows that, whereas only gentle variations in intrabolus pressure oc
cur in the main body of the bolus due to weak frictional forces there,
large frictional forces force a rapid rise in pressure near the bolus
tail induced by circular muscle squeeze. Of particular interest is th
e analysis of incomplete clearance of bolus fluid in the aortic arch r
egion. The only physically correct model consistent both with the vide
ofluoroscopic and the manometric data implies the existence of two sep
arate contraction waves, one above and one below the transition zone.
As the proximal wave slows and decreases in strength, a new distal wav
e forms, pinching off bolus fluid as it propagates distally. We hypoth
esize that the contraction wave in the upper esophagus is associated w
ith striated circular muscle, that this wave slows, weakens, and dies
at the proximal end of the esophageal transition zone, that a separate
contraction wave is born distally due to smooth muscle in that segmen
t, and that this distal wave is responsible for transporting bolus flu
id into the lower smooth muscle-dominated esophagus. We hypothesize th
at these ''striated'' and ''smooth'' muscle contraction waves are prop
erly coordinated in normal bolus transport and that bolus retention in
the transition zone is due to a temporal and spatial ''mismatch'' of
the upper and lower peristaltic waves.