Effect of Different Viscosities on Pharyngeal Pressure During Swallowing: A Study Using High-Resolution Manometry

Objectives: To investigate and compare the mechanism of swallowing with respect to the viscosity of ingested material between patients with and without dysphagia.

Design: Prospectively collected and retrospectively analyzed clinical study.

Setting: General teaching hospital, rehabilitation unit.

Participants: We retrospectively reviewed the high-resolution manometry (HRM) results of 35 patients with dysphagia symptoms (N=35). Additionally, we included 18 patients without dysphagia. Based on videofluoroscopic swallowing study results, we classified the patients into 2 groups: one with aspiration and the other without aspiration.

Intervention: Swallowing of a 5-mL thin liquid and 5-mL honey-like liquid in all patients.

Main outcome measure: HRM of various variables during the swallowing process.

Results: There was no significant difference between the thin liquid and honey-like liquid with respect to parameters for HRM in the patients without dysphagia and in the nonaspiration and aspiration groups. However, in a comparison between thin liquid and honey-like liquid with respect to visuospatial and timing variables, the degree of differences in the maximal pressure of the velopharynx in the aspiration group was significantly larger than the patients without dysphagia and the nonaspiration group (P<.05).

Conclusions: Our results indicate that there is a clear difference in the degree of adaptation to viscosity between the 3 groups-patients without dysphagia, patients with aspiration, and patients without aspiration. These differences may provide an explanation for the mechanism of swallowing, which may be useful for the treatment of dysphagia.