Swallowing physiology and pathophysiology.

Many disturbances in oropharyngeal physiology can result in aspiration. Poor tongue movement in chewing or in the oral swallow can cause food to fall into the pharynx and into the open airway before swallowing. A delay in triggering the pharyngeal swallow can result in food falling into the airway during the delay when the airway is open. Reduced peristalsis in the pharynx, whether unilateral or bilateral, will cause residue in the pharynx after the swallow that can fall or be inhaled into the airway. Reduced laryngeal elevation causes food to catch at the top of the airway. This residual food is then easily aspirated during the inhalation after the swallow. Reduced laryngeal closure may result in food penetrating the larynx during the pharyngeal swallow. Cricopharyngeal dysfunction can result in material remaining in the pyriform sinus, with aspiration of material into the airway after the swallow. Aspiration may also occur because food returns or is refluxed from the stomach or esophagus back into the pharynx. Each of these causes of aspiration can occur in a variety of patients, including those with neurologic impairment or structural damage. Each of these causes of aspiration has a different treatment. Thus, accurate and in-depth evaluation of swallowing anatomy and physiology in the oral-pharyngeal region as well as in the esophagus is necessary in successful re-establishment of oral nutrition in the dysphagic patient. Currently, such thorough evaluation requires radiographic graphic techniques, that is, videofluoroscopy and often manometry as well.