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D H Slavit

Publications and source records attributed to D H Slavit.

26 records · Page 2Linked to original sources
PubMed1991

Regulation of phonatory efficiency by vocal fold tension and glottic width in the excised canine larynx.

An excised canine larynx was used to assess the effects of glottic width and vocal fold tension on acoustic power, aerodynamic power, and vocal efficiency. Multiple regression analysis of the data obtained from 10 larynges revealed that with increased vocal fold tension there is a logarithmic decline in radiated acoustic power, while aerodynamic power remains constant (p less than .05). Vocal efficiency has a similar logarithmic decrease with increased tension (p less than .05). With narrowing of the glottis, the acoustic power increases more than the aerodynamic power delivered to the larynx, and the efficiency increases. The inverse relationships glottic width has with acoustic power and vocal efficiency are best described by a reciprocal model (p less than .01). There is a negative linear relationship between glottic width and aerodynamic power. These results suggest that within the larynx the energy conversion is regulated by glottic aperture and longitudinal vocal fold tension. The optimal width for efficiency appears to be the narrowest width that produces phonation within the modal register, whereas increased tension decreases the efficiency of the glottis.

Animals↗
PubMed1991

Study of phonation in the excised canine larynx.

Previous studies have demonstrated that the laryngeal muscles responsible for pitch variation and vocal efficiency are the cricothyroid muscles, affecting longitudinal tension of the vocal folds, and the thyroarytenoid muscles, controlling the lateral stiffness of the vocal folds. Longitudinal tension in the vocal fold is easily simulated in the excised canine larynx. The effect of the thyroarytenoid muscle, however, has not been adequately analyzed. To simulate the effect of the thyroarytenoid muscle, small balloons were placed in the paraglottic space at the level of the vocal folds in 10 excised canine larynges. These balloons (Fogarty catheters) could be inflated in increments to simulate the effect of the thyroarytenoid muscle contraction in altering the lateral stiffness of the vocal fold. During phonation subglottic pressure, vocal fold longitudinal tension and balloon size were systematically varied. The photoglottographic and electroglottographic signals, sound intensity, and airflow rate were measured. Multiple regression analysis showed that sound intensity was directly related to subglottic pressure (p less than 0.001) and inversely related to balloon size (p less than 0.001). Vocal efficiency was directly related to subglottic pressure (p less than 0.001). Frequency of vibration was directly related to balloon size (p less than 0.05), vocal fold tension (p less than 0.001), and subglottic pressure (p less than 0.001). Open quotient was directly related to vocal fold tension (p less than 0.01) and inversely related to balloon size (p less than 0.001). Clinical implications of these results will be discussed.

Animals↗
PubMed1991

Effect of superior laryngeal nerve on vocal fold function: an in vivo canine model.

Assessment of laryngeal framework surgery requires an awareness of the effect of vocal fold mass, stiffness, and position on voice production. The vibratory pattern of vocal folds during phonation depends on the subglottic pressure as well as the mass and stiffness of the folds. To assess the effect of variations in vocal fold tension with contraction of the cricothyroid muscle on phonation, eight mongrel dog larynges were studied in vivo. Photoglottography, electroglottography, and subglottic pressure were simultaneously recorded as airflow rate and superior laryngeal nerve (SLN) stimulation were varied. Stimulation of the SLN was modified by varying the frequency and voltage of the stimulating electrical signal. Multiple regression analysis of the data revealed a direct relationship between the voltage of SLN stimulation and frequency of vibration (p less than 0.001) at constant subglottic pressure. Increases in the stimulating voltage to the SLN also led to an increase in open quotient (p less than 0.001), but no statistically significant change in speed quotient, subglottic pressure, or sound intensity. Changing the frequency of SLN stimulation had only a modest effect on the frequency of vibration. These results are consistent with the reported findings of an increase in frequency and open quotient with increased tension in an in vitro canine model. The glottographic measurement open quotient appears to be an estimator of cricothyroid contraction and longitudinal vocal fold tension, and may be clinically applicable to the assessment of superior laryngeal nerve injuries and laryngeal framework procedures.

Animals↗
PubMed1990

Glottographic analysis of phonation in the excised canine larynx.

An excised canine larynx model of phonation was developed to assess the effect of vocal fold length and tension on glottographic waveforms. The canine larynx in an experimentally produced phonatory model vibrated in a two-mass system comparable to human voice production. The recorded glottographic waveforms for the excised canine larynx were similar to signals recorded in humans in the chest register. Vocal fold length, longitudinal vocal fold tension, glottic width, and airflow rate were varied while simultaneous measurements were made of the subglottic pressure, electroglottographic signal, photoglottographic signal, and acoustic signal. The model used is illustrated and discussed, with emphasis on the method of simulating the actions of all of the intrinsic laryngeal muscles, including the thyroarytenoid muscles. The open quotient and speed quotient, calculated from the glottographic signals, were dependent on vocal fold length and tension and glottic width. These results suggest that glottographic analysis, particularly speed quotient and open quotient, provide valuable information on vocal fold vibration during phonation, and may be important in assessing laryngoplasty procedures.

Animals↗
PubMed1990

Rhinolift operation in the treatment of the aging nose.

Disturbance of the normal relationship between the caudal border of the upper lateral cartilage and the cephalic margin of the lobular cartilage--the so-called "cul-de-sac" area--can result in alar collapse and nasal airway obstruction. This may be caused by either the aging process or trauma, both surgical and nonsurgical. Rhinolift is a surgical procedure that was developed for the treatment of the aging ptotic nasal tip. We have applied this technique to patients with nasal airway obstruction resulting from alar collapse. Elevation of the cephalic margin of the lobular cartilage to a position superficial to the upper lateral cartilage restores the normal relationship between these two structures. The upper lateral cartilage then assists in stenting the vestibule open, and thereby improves nasal breathing. Over the past 10 years, 20 patients have had rhinolifts at our institution for the relief of nasal airway obstruction. Concomitant surgery included nasal septal reconstruction in 12 patients, polypectomy in one patient, and placement of a silicone rubber septal prosthesis for closure of a large septal perforation in three patients. Rhinolift was the sole procedure used for the correction of valvular pathology in 10 patients. The other 10 patients had modifications made in their upper lateral cartilage along with the rhinolift. Five patients described restoration of normal nasal breathing, while 14 patients showed partial symptomatic improvement. One patient reported no improvement in nasal breathing. Rhinolift is a safe effective surgical technique for functional improvement of nasal breathing in patients with alar collapse resulting from inadequate cartilaginous support.

Adult↗
PubMed1990

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.

Air↗
PubMed1990

Physiologic assessment of Isshiki type III thyroplasty.

Isshiki type III thyroplasty is a laryngeal framework surgical procedure that lowers a patient's pitch. To objectively assess the procedure, preoperative and postoperative voice recordings, as well as electroglottography and photoglottography were performed. Jitter, shimmer, and glottographic quotients were measured to assess changes in vibratory pattern. The mean and range of frequencies in contextual speech was also determined. Analysis of the preoperative and postoperative data from two patients with over 1 year follow-up showed a decrease in frequency of vibration. Postoperatively, the vocal folds still vibrated in a regular pattern as described by the myoelastic-aerodynamic theory. There was no increase in jitter or shimmer quotient. The Isshiki type III thyroplasty appears capable of lowering fundamental frequency of speech without adversely affecting the vibratory mode of the vocal folds.

Adult↗