The use of cervical auscultation in the evaluation of the pharyngeal swallow may become a part of the clinical evaluation of dysphagic patients. Though its use is based on subjective evaluation, an acoustic analysis of swallowing sounds might establish more objective criteria in the detection of swallowing disorders. The present study sought to investigate three aspects of the methodology for detecting swallowing sounds: (1) the type of acoustic detector unit suited to an acoustic analysis of the pharyngeal swallow, (2) the type of adhesive suited for the attachment of the detector, and (3) the optimal site for sound detection of the pharyngeal swallow. An accelerometer with double-sided paper tape was selected as the appropriate detector unit because of its wide range of frequency response and small attenuation level. Using this detector unit, swallowing sounds and noise associated with simulated laryngeal elevation and the carotid pulse were acquired at 24 sites on the neck in 14 normal subjects; these signals were acoustically analyzed. The determination of the optimal site for detecting swallowing sounds was based on the signal-to-noise ratio. The site over the lateral border of the trachea immediately inferior to the cricoid cartilage is the optimal site for detection of swallowing sounds because this site showed the greatest signal-to-noise ratio with the smallest variance. The site over the center of the cricoid cartilage and the midpoint between the site over the center of the cricoid cartilage and the site immediately superior to the jugular notch were also considered to be the most appropriate sites.

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In order to undertake a quantitative evaluation of balance occlusal load, the use of the Dental Prescale System was investigated. The method uses a test sheet that undergoes a colour-developing chemical reaction, for detecting contact area, and a computerized analysis system, for evaluating the balance of occlusal load. Twenty natural dentate subjects and 10 hemimaxillectomy patients participated in the study. Each subject bit a test sheet as hard as possible for 3 s. The balance of occlusal load was expressed as a percentage of the load on the side with the lesser occlusive load (%OLR). The %OLR ranged from 39.7% to 49.4% in the natural dentate subjects, and from 0% to 31.3% in the hemimaxillectomy patients at their resection site. The patients' low %OLRs were attributed to loss of sustaining structure and subjective occlusal adjustment by clinicians. Combining technical simplicity, relatively high reproducibility, and diverse analysis capability, this system is useful for quantitative evaluation of balance of occlusal load in clinical situations.

Cervical auscultation is being used more frequently in the clinical assessment of dysphagic patients. The present study was designed to assess symmetry and the reproducibility of swallowing sounds detected simultaneously from bilateral cervical sites. Symmetry of the swallowing sounds acquired using our method was verified because no significant differences were found for any parameters in both time and frequency domain analyses between swallowing sounds detected bilaterally. This result supports the use of a "unilateral" site for the detection of swallowing sounds. The reproducibility of swallowing sounds was assessed by a coefficient of variation. Results of this analysis suggest that one should evaluate the acoustic characteristics of swallowing sounds from repeated swallows rather than from one swallow.