The passage velocity of various types of food in the pharynx when healthy individuals swallowed was measured by the ultrasonic pulse Doppler method in order to clarify the relationship between the rheological property of each type of food and the relative difficulty of aspiration.
The food types tested were divided into two categories; one comprised food that patients with dysphagia could aspirate easily (EA category) and the other comprised food that was more difficult to aspirate (DA category). The mean velocity (V_MEAN), maximum velocity (V_MAX), degree of velocity dispersion (spectrum area : SA), and the time for swallowing (ST) in the pharynx were compared between the two food categories.
As a result, V_MEAN and V_MAX values for each food in the DA category were significantly lower, while SA was significantly lower than each food in the EA category (p< 0.01). ST was 0.9-1.1 (s), but bore no relationship with the difficulty of aspiration. The food in the EA category was statistically distinguishable from that in the DA category by a cluster analysis.
The results show a close relationship between the passage velocity of food in the pharynx and the difficulty of aspiration to the trachea for the food.