- Email: [email protected]
Estimating phonation threshold pressure via alrflow interruption
Otolaryngology Head and Neck Surgery Volume 117 Number 2
Three larynges each from dogs, monkeys, and pigs were compared with three ex vivo human larynges. Microflap surgery was performed on one VF from each larynx. Both the operated and nonoperated VFs were examined histologically by using a Movats stain specific for elastin, mature collagen and younger, more delicate collagen. The distribution of these fibers was found to differ among the species. Unlike the human VF, which has a higher elastin concentration in the deeper layers of the lamina propria, both the pig and the dog had a thin band of elastin concentrated just deep to the basement membrane. Beneath this thin band of elastin, the collagen was less mature, and there was no elastin concentration comparable to that found in the human intermediate layer of the lamina propria. The monkey VF had a very thin mucosal layer with no significant elastin concentration in any layer. The microflap dissections in the dog, pig, and human VFs were similar, located within that portion of the lamina propria where the elastin and mature collagen are less concentrated. The microflap plane in the monkey was located deeper near the vocalis fibers. Despite the different location of elastin, the microflap plane was found to be similar in humans, dogs, and pigs. Videostroboscopy was then performed on two dogs and two pigs after first performing a tracheotomy for ventilation and airflow through the glottis. Arytenoid adduction sutures were placed to facilitate vocal fold adduction. These sutures may remain in place for survival studies and follow-up stroboscopy. The canine anatomy was much more suitable for microsuspension laryngoscopy and stroboscopic examination. Acknowledging that no animal's laryngeal anatomy is identical to that of the human, the dog is believed to be a more suitable animal model for studies on VF surgery based on both the histologic and stroboscopic results. Poster 53
Estimating Phonalion Threshold Pressure Via Airflow Interruption JACK JIANG, MD, PhD, TIMOTHY O'MARA, BS (presenter), KIMBERLY FISHER,PhD, and DAVID G. HANSON, MD, Chicago and Evanston, III.
Objective: Existing methods to measure phonation threshold pressure are clinically impractical because they are invasive or require very soft, steady phonation. An airflow interruption system was therefore developed to allow noninvasive estimation of phonation threshold pressure (PTP) at different levels of vocal intensity. We hypothesized that PTP would be elevated during loud phonation due to the potential for high levels of vocal fold adduction and increased mucosal wave velocity. Methods: Six males with normal voice repeatedly produced a steady vowel/a/with controlled soft, medium, and loud phonation: 75, 80, and 85 dB, respectively. Phonatory airflow was collected by a face mask and directed through a pipe that contained a balloon valve. During phonation, the valve was closed unexpectedly (400 msec) during which time
Research Forum--Monday
P101
the airflow was obstructed, intraoral pressure was increased, and phonation was momentarily interrupted. At the moment phonation ceased, oral pressure was taken as the PTP estimate. Timing of flow and voice cessation were determined by pneumotachography and acoustic voice recording. Results: The estimated mean PTP values were 7.09 cm H20 at 75 dB, 8.77 cm H20 at 80 dB, and 13.82 cm H20 at 85 dB (ANOVA: p < 0.0001). Conclusions: Unlike the other commonly used methods, airflow interruption during a sustained vowel allows estimation of PTP at a variety of vocal intensity levels glottal configurations. The increase in phonation threshold pressure with vocal intensity was consistent with that expected for different glottal widths and lengths. (This work supported by P60 DC 94-002-02 NIDCD/NIH, R01 DC 00254-11 NIDCD/NIH, and T32 DC 0015-15 NIDCD/NIH.) Poster 54
Botulinurn Toxin Injection of the Thyroarytenoid Muscle in Experimental Laryngeal Paralysis R. TODD SNOWDEN, MD (presenter), DAVID OSBORN, MD, ARNE HENGESTEG,JEROME THOMPSON, MD, MBA, and GAYLE E. WOODSON, MD, Memphis, Tenn.
Objective: To determine the effect on laryngeal resistance of botulinum injection into the thyroarytenoid (TA) muscle in experimental laryngeal paralysis. Design: Randomized placebo control trial. Subjects: Nine mongrel cats. Interventions: We sectioned the left recurrent laryngeal nerve in seven cats. After 7 weeks, we injected 10 U of botulinum toxin (botox) into the left TAs of four experimental subjects and saline into three controls. Two intact cats also received botox injections. Two weeks after injection, animals were anesthetized for measurement of subglottic flow and pressure, videolaryngoscopy, and bilateral electrical stimulation of the recurrent nerves to deplete glycogen. Larynges were harvested for histologic analysis. Results: In intact animals 10 U botox significantlyreduced vocal fold adduction. Mean laryngeal resistance was highest in the control group. There was no appreciable difference in resistance between botox-treated and intact animals. Histologic analysis revealed diffuse glycogen depletion on the intact Side in all groups and in the TA muscle of both experimental and control groups, indicating significant TA reinnervation. No significant effect of botox on staining could be detected. Glycogen staining was patchy in the left LCA and PCA muscles, indicating incomplete reinnervation. Conclusions: Injection of botulinum toxin was associated with lower laryngeal resistance in cats with experimental RLN paralysis. Glycogen depletion analysis indicated preferential reinnervation of the TA, which may explain the tendency of the paralyzed vocal fold to medialize over time. Clinical studies would be needed to assess the clinical utility of botulinum toxin in management of patients with bilateral laryngeal paralysis.
t,)
o,) t/~
Three larynges each from dogs, monkeys, and pigs were compared with three ex vivo human larynges. Microflap surgery was performed on one VF from each larynx. Both the operated and nonoperated VFs were examined histologically by using a Movats stain specific for elastin, mature collagen and younger, more delicate collagen. The distribution of these fibers was found to differ among the species. Unlike the human VF, which has a higher elastin concentration in the deeper layers of the lamina propria, both the pig and the dog had a thin band of elastin concentrated just deep to the basement membrane. Beneath this thin band of elastin, the collagen was less mature, and there was no elastin concentration comparable to that found in the human intermediate layer of the lamina propria. The monkey VF had a very thin mucosal layer with no significant elastin concentration in any layer. The microflap dissections in the dog, pig, and human VFs were similar, located within that portion of the lamina propria where the elastin and mature collagen are less concentrated. The microflap plane in the monkey was located deeper near the vocalis fibers. Despite the different location of elastin, the microflap plane was found to be similar in humans, dogs, and pigs. Videostroboscopy was then performed on two dogs and two pigs after first performing a tracheotomy for ventilation and airflow through the glottis. Arytenoid adduction sutures were placed to facilitate vocal fold adduction. These sutures may remain in place for survival studies and follow-up stroboscopy. The canine anatomy was much more suitable for microsuspension laryngoscopy and stroboscopic examination. Acknowledging that no animal's laryngeal anatomy is identical to that of the human, the dog is believed to be a more suitable animal model for studies on VF surgery based on both the histologic and stroboscopic results. Poster 53
Estimating Phonalion Threshold Pressure Via Airflow Interruption JACK JIANG, MD, PhD, TIMOTHY O'MARA, BS (presenter), KIMBERLY FISHER,PhD, and DAVID G. HANSON, MD, Chicago and Evanston, III.
Objective: Existing methods to measure phonation threshold pressure are clinically impractical because they are invasive or require very soft, steady phonation. An airflow interruption system was therefore developed to allow noninvasive estimation of phonation threshold pressure (PTP) at different levels of vocal intensity. We hypothesized that PTP would be elevated during loud phonation due to the potential for high levels of vocal fold adduction and increased mucosal wave velocity. Methods: Six males with normal voice repeatedly produced a steady vowel/a/with controlled soft, medium, and loud phonation: 75, 80, and 85 dB, respectively. Phonatory airflow was collected by a face mask and directed through a pipe that contained a balloon valve. During phonation, the valve was closed unexpectedly (400 msec) during which time
Research Forum--Monday
P101
the airflow was obstructed, intraoral pressure was increased, and phonation was momentarily interrupted. At the moment phonation ceased, oral pressure was taken as the PTP estimate. Timing of flow and voice cessation were determined by pneumotachography and acoustic voice recording. Results: The estimated mean PTP values were 7.09 cm H20 at 75 dB, 8.77 cm H20 at 80 dB, and 13.82 cm H20 at 85 dB (ANOVA: p < 0.0001). Conclusions: Unlike the other commonly used methods, airflow interruption during a sustained vowel allows estimation of PTP at a variety of vocal intensity levels glottal configurations. The increase in phonation threshold pressure with vocal intensity was consistent with that expected for different glottal widths and lengths. (This work supported by P60 DC 94-002-02 NIDCD/NIH, R01 DC 00254-11 NIDCD/NIH, and T32 DC 0015-15 NIDCD/NIH.) Poster 54
Botulinurn Toxin Injection of the Thyroarytenoid Muscle in Experimental Laryngeal Paralysis R. TODD SNOWDEN, MD (presenter), DAVID OSBORN, MD, ARNE HENGESTEG,JEROME THOMPSON, MD, MBA, and GAYLE E. WOODSON, MD, Memphis, Tenn.
Objective: To determine the effect on laryngeal resistance of botulinum injection into the thyroarytenoid (TA) muscle in experimental laryngeal paralysis. Design: Randomized placebo control trial. Subjects: Nine mongrel cats. Interventions: We sectioned the left recurrent laryngeal nerve in seven cats. After 7 weeks, we injected 10 U of botulinum toxin (botox) into the left TAs of four experimental subjects and saline into three controls. Two intact cats also received botox injections. Two weeks after injection, animals were anesthetized for measurement of subglottic flow and pressure, videolaryngoscopy, and bilateral electrical stimulation of the recurrent nerves to deplete glycogen. Larynges were harvested for histologic analysis. Results: In intact animals 10 U botox significantlyreduced vocal fold adduction. Mean laryngeal resistance was highest in the control group. There was no appreciable difference in resistance between botox-treated and intact animals. Histologic analysis revealed diffuse glycogen depletion on the intact Side in all groups and in the TA muscle of both experimental and control groups, indicating significant TA reinnervation. No significant effect of botox on staining could be detected. Glycogen staining was patchy in the left LCA and PCA muscles, indicating incomplete reinnervation. Conclusions: Injection of botulinum toxin was associated with lower laryngeal resistance in cats with experimental RLN paralysis. Glycogen depletion analysis indicated preferential reinnervation of the TA, which may explain the tendency of the paralyzed vocal fold to medialize over time. Clinical studies would be needed to assess the clinical utility of botulinum toxin in management of patients with bilateral laryngeal paralysis.
t,)
o,) t/~