Configuration of vocal folds during and after tube phonation in patients with voice disorders: A computerized tomographic study

Abstract

Purpose: The study aims to observe whether any systematic change in vocal fold configuration occurs during and after phonation into a tube using computerized tomography (CT). Materials and Methods: Ten participants diagnosed with functional dysphonia were included in the study. CT was performed when participants produced the sound (a:), phonated into a drinking straw and when repeating (a:) after the exercise. Similar procedure was performed with a stirring straw after 20 min of vocal rest. Anatomic variables included: (1) glottal area, (2) glottal width, (3) vertical vocal fold thickness, (4) vocal fold area, and (5) vocal fold length. Each vocal fold was separately analyzed. Results: Only glottal area for stirring straw was statistically different throughout the three time points. This variable increased during tube phonation compared to conditions pre- and post-tube. Discussion: Since vocal fold length did not change during tube phonation, the increment in glottal area was likely due to increased amplitude of vibration. Increased vibratory amplitude has been found in previous studies with high-speed imaging, suggesting an increased subglottic pressure. From the physiologic point of view, transglottal pressure plays an important role in vocal fold amplitude of vibration. Conclusions: Tube phonation seems to cause increased glottal area during exercise. This change is more prominent during exercise with a higher degree of airflow resistance. Therefore, the degree of flow resistance is an important clinical variable to be considered when choosing the right voice exercises regarding the voice status/phonatory pattern of patients during voice therapy.