Phonatory vocal fold function in the excised canine larynx.

The development of valid objective measurements of vocal cord vibration during phonation is a goal of current research in laryngeal physiology. An excised canine larynx was used to study the effects of vocal cord tension, air flow rate, and glottic width on glottographic parameters. The electroglottographic and photoglottographic wave-forms were simultaneously recorded as the vocal cord tension, glottic width, and air flow rate were systematically varied. These glottographic waveforms were analyzed to determine the open quotient and speed quotient. Multiple regression analysis of the data obtained from 10 larynges showed the open quotient to be directly related to vocal fold tension (p less than 0.001), glottic width (p less than 0.01), and fundamental frequency (p less than 0.001). Speed quotient was inversely related to glottic width and and subglottic pressure (p less than 0.05). Regression analysis also showed frequency of vibration to be directly related to tension (p less than 0.001) and inversely related to glottic width (p less than 0.001), with different combinations of glottic tension and width capable of producing the same frequency. The open and speed quotients thus reflect the changes in the vibratory patterns of the vocal folds produced by alterations in tension and width. The clinical implications of these results will be discussed, with emphasis on glottography as an objective assessment of the various laryngeal framework procedures being performed.