Development of New Diagnostic Method for Detecting Swallowing Disorders

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This study was designed to evaluate quantitatively the expiratory sounds after swallows as a method for distinguishing dysphagic from normal swallows.[Subjects and Methods] Forty three mixed pre- and post-surgical head and neck cancer patients were examined. Before the examination, all patients were instructed to make clear soft expiratory sunds (SES) without harsh or wet breating. Patients cleared any residual secretions in the pharyngo-laryngeal region by voluntary cough until they could make SES.For some patients, suctioning was required to meet this requirement. Patients swallowed 5 ml of barium (180%w/v) several times. SES after the swallows were detected using our method and fed to a VHS video recorder with videofluorographic (VE) images of these swallows and expiratory events. Acoustic signals of SES were analyzed by our computed acoustic analyzing system to obtain an averaged magnitude of each frequency band from 0 to 4 kHz using the 250 Hz, 500 Hz and 1 octave band analyzes. Five to seven SESs were evaluated for each subject.[Results and Conclusions] From the VF data, 92 SESs were produced after the swallow without aspiration or penetration (SESwoAP), 102 SESs were produced after dysphagic swallows with aspiration (SESwA), and 16 SESs were produced after dysphagic swallows with penetration (SESwP). The averaged magnitudes from 0 to 1000 Hz bands of SESwAs were significantly greater than those of SESwoAPs (p<01 by Mann- Whitney U test). Comparison of the averaged magnitude from 0 to 250 Hz band of SESs with the VF data (woAP/wA) showed significant agreement in both areas. Sensitivity was 83.2%, specificity 82.6% and percent agreement was 82.9% (critical magnitude : 26.0 dB). These results support using SES as a clinical tool for detecting aspiration.