The effect of increased bolus viscosity on esophageal peristaltic function was studied in six healthy volunteer subjects. Intraluminal pressure events were measured with an infused catheter system and lower esophageal sphincter pressure was monitored continuously with a Dent sleeve. Boluses with viscosities of 2.5, 8.7, 48, and 860 centipoise (cP) were compared with a water bolus. Increasing bolus viscosity to 48 and 860 cP elicited a slowing of wave velocity, an increase in wave duration, and a prolongation of lower esophageal sphincter relaxation. The initial change noted at lower viscosities was an increased duration of contraction wave. Maximal changes were noted at the 48 cP bolus. In conclusion, increased bolus viscosity significantly alters human esophageal peristalsis. These changes may be mediated by esophageal stretch reflexes or by the intrinsic properties of the esophageal musculature or both.

Previous studies have demonstrated that nonviscous liquids traverse the esophagus more rapidly with the subject in the upright rather than the supine position. Conversely, similar studies have shown that viscous liquids traverse the esophagus at similar rates for both upright and supine positions. Our purpose was to define the motor correlates of these differing responses. Six normal volunteers were studied with an infused catheter system incorporating a Dent sleeve for monitoring lower esophageal sphincter pressure. The subjects were given a series of swallows of a water and a viscous (52 centipoise) bolus in both the supine and upright positions. In the upright position, the water bolus caused an increased velocity of propagation in the proximal esophageal segment that was associated with a shortening of lower esophageal sphincter relaxation time and reductions in amplitude and duration of contraction. No significant changes in the peristaltic wave were noted with the viscous bolus during alterations of body position. We conclude that the more rapid transit of a nonviscous water bolus through the esophagus in the upright position is reflected in specific alterations of esophageal peristaltic parameters. The possible mechanisms for these differing responses are discussed.