A characteristic sequence of sounds is produced during infant suckle-feeding and can be readily detected through the skin over the larynx. The sounds are consistent between swallows and are used clinically in diagnosis of gross feeding impairment. However, their evaluation is at present empirical. Recent analysis of these sequences has identified brief discrete high-frequency sounds suitable as templates for a computer recognition system, so that an automatic recognition and analysis system is now a possibility. These discrete sounds occur at the junction of swallow and breath and thus contain information on coordination at crucial phases of the swallow-breathing activity. Analysis of the sounds could provide a non-invasive method of study at high time resolution of the activity of pharyngeal structures during swallowing in patients with suspected swallowing impairment. Identification of the source of the sounds is an important step in the development of such a system, but the methods required are too invasive for human investigation. This project will use the newborn lamb as an appropriate model for the study of suckle feeding. Minor surgery will be performed to implant EMG electrodes in muscles of the larynx and pharynx, and impedance electrodes bilaterally across the larynx at the level of the vocal folds and across the esophagus at the upper esophageal sphincter. After recovery the lambs will be bottle-fed on a regular schedule, while recording EMG, impedances, pharyngeal and oral pressures, breathing, and sounds of swallow from a microphone attached to the neck. Data will be taped for later analysis. By examining the relationship between different components of the sounds, bolus movement as revealed by impedance and pressure changes, and airway closure and opening as shown by EMG and impedance records, it should be possible to associate the sounds with specific events in the swallow sequence. In addition, analysis of the recorded pharyngeal sounds will be performed in order to correlate variations in their characteristics with physiological variations in the coordination of swallowing and breathing.
