Biomechanics of Human Epiglottal Movement and Inversion

This study will examine how the airway closes during swallowing to prevent food or liquid from entering the voice box or lungs while eating or drinking. It will also test whether electrical stimulation of muscles in the neck can close the airway as it would close during swallowing. The long-term goal of this research is to determine the feasibility of a new approach for helping patients with a severe and life threatening swallowing disorder.

Healthy normal volunteers between 18 and 65 years of age who can swallow normally may be eligible for this study. Candidates are screened with a medical history, physical examination, electrocardiogram and nasolaryngoscopy. For the nasolaryngoscopy, the subject's voice box and epiglottis (flap of tissue that covers the windpipe during swallowing) are examined using a thin flexible tube with a camera attached that is passed through the nose to the back of the throat. During the test, speech and other tasks such as singing and whistling are observed. The camera records the movement of the vocal cords on videotape. This procedure may be repeated another time during the study.

Participants undergo the following procedures:

• Electrical stimulation of muscles in the neck: The muscles in the neck are stimulated with brief low-level electrical currents to see if the stimulation can cause the epiglottis to fold down over the windpipe. Stimulation may be increased to a level where it feels like a small shock The subject is asked to try to do the muscle stimulation while swallowing.
• Videofluoroscopy (recording swallowing and muscle stimulation during x-ray imaging of the head): The head and neck are x-rayed while the subject swallows. After the wires have been inserted for EMG (see below), markers are glued to the tongue and a tube is inserted through the nose into the esophagus. The movements during swallowing with and without muscle stimulation are x-rayed and analyzed later to determine how the stimulation affects the movement of the epiglottis.
• Electromyography (EMG): Measurement of the electrical activity of muscles in the neck using fine wires placed through the skin into muscles in the chin.
• Manometry: During the videofluoroscopy, a manometer (tube that measures pressures) is placed through the nose and into the back of the throat at the entry point to the esophagus. This test shows whether muscle stimulation can fold down the epiglottis.
• Surface electromyography (sEMG): The tube used during the videofluoroscopy has small rings embedded in it that measure muscle activity on the surface of the inside of the throat.