Effects of thermal burns on vocal fold biomechanics
Hunnicutt, Tracie Lynn
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Bums are injuries that affect multiple body systems. Changes in voice quality are commonly seen in bum patients; however, no systematic research has been done on the vocal fold parameters that may cause this change (Haponik & Munster, 1990). The purpose of this study was to analyze several vocal fold kinematics that are affected as a result of thermal injury. Three subjects with known inhalation injuries or at least 20% total body surface area bumed were recruited from a local burn center. Three normal subjects were matched to the bum patients by age and gender for comparison. Subjects were instructed to phonate while a rigid endoscope was positioned superiorly to the vocal folds. Images obtained were recorded, digitized and analyzed using a Kay Stroboscopy System. Results indicated differences between normal subjects and bum patients for all parameters examined. Mucosal wave was decreased in two out of three bum patients, secondary to edema formation and iatrogenic conditions (e.g., intubation granulomas). Upon visual analysis glottal area was decreased; however, measurements taken by the image processing software indicated a slight increase in glottal area of bum patients in comparison to normal subjects. Amplitude and symmetry of vocal fold movements were disturbed by damage to the superior layers of the folds, and unequal damage to each individual fold. These differences in amplitude, as well as differences in timing created aperiodic movements of the vocal folds. The current study establishes that there are differences in vocal fold biomechanics following thermal trauma and inhalation injury. This could be viewed as an introductory study in an area that previously has not been researched. Future research should address increased quantification of biomechanical and perceptual changes, as well as possible clinical applications.