Normal Breathing and Swallowing in Healthy Volunteers

Participants will inspire deeply through the nebulizer coupled to the facemask and pneumotachograph. Each test inhalation will be separated by an interval of 2 minutes. This experimental trial consists of six (instead of 8) test solutions: 0, 25, 50, 100, 200 and 500 μM capsaicin in 80% physiological saline, 20% ethanol. Participants will inhale single vital capacity breaths of capsaicin solution via an air-powered dosimeter (KoKoDigidoser; Pulmonary Data Services Instrumentation Inc; Louisville, CO). The reflex cough test ends when the participant coughs at least 2 times in response to one inhalation dose, or receives a dose of the highest concentration (500 μM).

The swallowing systems core laboratory is fully equipped to perform videofluoroscopy with a c-arm (OEC 9900) that is dedicated solely to research purposes. Videofluoroscopy recordings will be kept to a minimum and turned on only during completion of a specific testing task. Video recording and images captured during the videofluoroscopy will be synced and saved for data analysis. Videofluoroscopy allows for time-synced, frame-by-frame data analysis for the specific measures taken during swallowing tasks. The physiological swallowing measures (temporal and kinematic of the base of tongue, oropharynx, and hyolarynx complex during swallowing) to be analyzed cannot be visualized with any other technique. All swallowing tasks will be completed using barium in order to visualize the bolus during movement of various swallowing muscles and structures.