Delayed swallow reflex refers to when a person’s automatic swallow reflex—which normally kicks in when liquid or chewed food in the mouth reaches the base of the tongue—is hampered. Individuals with normal swallowing rarely notice or think about the action of their swallow reflex, but on occasion the reflex may startle a person and draw more attention to itself: for example, when a person sucks on a hard candy that inadvertently goes a little too far back in the mouth and—gulp!—it is involuntarily swallowed.

If a person’s swallow reflex is delayed, then food material may slip back to the base of the tongue and, before the swallow happens, drop down to fill the vallecula or even the pyriform sinuses. This is of particular concern when swallowing liquids because, given their low viscosity, thin liquids can easily flow downward into the larynx and trachea (aspiration). Compare this disorder with absent swallow reflex.

Delayed Swallow Reflex: Compare Blue Applesauce and Blue Water

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VESS (1 of 4)

During VESS, blue-stained applesauce falls down to the posterior base of tongue. If the swallowing reflex were normal, the patient would have swallowed before the applesauce arrived here.

Delayed swallow reflex (2 of 4)

Because of the viscosity of the material it "hangs" for a moment and does not fall down into the entrance of the larynx. Even with a delayed swallow reflex, there is still a second or two to swallow before that happens. The patient will tend to cough less with this consistency than with water.

Blue-stained water (3 of 4)

Here, blue-stained water is flowing into the right pyriform sinus (left of photo at arrow). Movement is rapid (note the blur) due to the low viscosity of water; there is less time to react and swallow than with applesauce, explaining why coughing on water is more common than purée or solid.

No residue (4 of 4)

Still, at the end of several boluses of applesauce and water, stained with blue food coloring, there is no stain or residue inside the entrance of the airway. The delayed swallowing reflex is a liability but without a risk of pneumonia.

Dysphagia / Delayed Swallow Reflex

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Laryngopharynx (1 of 3)

Panoramic view of laryngopharynx before administering blue-stained applesauce.

Dysphagia / Delayed swallow reflex (2 of 3)

Same view after first bolus of blue-stained applesauce. The vallecula fills with material before the swallow “happens”—signifying a delayed swallow reflex.

Hypopharyngeal pooling (3 of 3)

After several rapidly-administered boluses (to assess patient’s “limits”), note hypopharyngeal pooling, but none within the laryngeal vestibule.