Quantitative assessment of swallowing in healthy adults.

Swallowing has hitherto been evaluated during physical examination, radiologic barium studies, manometry, and cervical auscultation. Radiography principally demonstrates qualitative aspects of oral and pharyngeal function, whereas quantitative aspects have primarily been documented by manometry. To evaluate swallowing quantitatively, without using invasive methods or radiation, we have applied a combined test of water drinking, i.e., the Repetitive Oral Suction Swallow test (ROSS). The test provides reliable measurements of suction pressure, bolus volume, timing of important events in oral and pharyngeal swallow, and respiration. The test is described and results from 292 healthy, non-dysphagic subjects are presented. We found a mean bolus volume of 25.6 +/- 8.5 ml during single swallow and 21.1 +/- 8.2 ml during stress (forced, repetitive swallow). During forced, repetitive swallow, the bolus volume was more strongly associated with suction time (r2 = 0.55) than with peak suction pressure (r2 = 0.04), indicating that suction time is more important than suction pressure in determining the bolus volume. The oral-pharyngeal transit time decreased: single swallow 0.56 +/- 0.36 sec, forced repetitive swallow 0.23 +/- 0.11 sec, as did the coefficient of variation (48% and 64%, respectively) indicating a more automatic neural process for pharyngeal function in forced, repetitive swallow. The postswallow respiration started with inspiration in 10% of studied individuals, but did not correlate with deviations in other variables in the test. Thus, postswallow inspiration must be considered as normal. The ROSS test offers a rapid and easy quantitative assessment of swallowing.