The Effect Of Vocal Process On Vocal Pitch And Glottal Phonation

Objective:The vocal cord process affects the pronunciation by fixing the vocal cord during the adduction of arytenoid cartilage,but the effect of vocal process on voice factors such as tone and pronunciation ability of larynx is not clear.In this study,the isolated dog larynx model with bilateral vocal cord process was established to understand the changes of acoustic and aerodynamic parameters such as sound signal,vocal cord vibration amplitude,subglottic pressure,subglottic air flow rate,etc.The effect of vocal process on pronunciation was discussed through the histological changes of vocal cord after resection of vocal process.To further understand the value of vocal process in the diagnosis and treatment of voice diseases.Methods:25 male isolated dog larynx（beagle dog）,14 normal isolated larynx model（the control group）and 11 bilateral vocal process resection isolated larynx model（the experimental group）were used.In the experimental group,the dogs were reared for 6months after bilateral vocal process was resected under general anesthesia,and then the isolated larynx was made.In a bad environment of sound insulation,use warm and humid air to blow the throat to make a steady sound.The aerodynamic parameters including threshold pressure PTP,airflow PTF and energy threshold PTW,were collected by microphone（Xion,Germany）.Acoustic parameters（sound intensity,fundamental frequency F₀,jitter,shimmer,HNR）and vibration amplitude of vocal cords were collected.Independent sample T-test analysis was used to compare the differences of acoustic signal parameters,aerodynamic parameters and vibration amplitude between the two groups.The vocal process and vocal cords of the two groups were partially resected,and Van-Gieson staining and immunohistochemistry（antibody Collagen I+III）were performed.ResultsCompared with the control group,the changes of PTF and PTW in the experimental group were significant（P<0.05）.PTF and PTW increased with the complete healing of vocal process resection,but there was no significant difference in PTP（P>0.05）.The acoustic parameters such as sound intensity,F₀,Jitter and Shimmer changed significantly,F₀and sound intensity decreased,Jitter and Shimmer increased,HNR decreased（P<0.05）.The amplitudes of the posterior middle and posterior joint of the vocal cords were statistically significant（P<0.05）.The resection of the vocal process had an effect on the membrane vibration of the posterior vocal cords,but there was no significant change in the amplitudes of the anterior middle of the vocal cords and the middle of the vocal cords（P>0.05）.Analysis of Van Gieson staining results:the control group showed cartilage tissue and normal lamina propria collagen tissue.In the experimental group,the density of stained collagen fibers basically increased,the arrangement varied from neat to disordered,and the fiber bundles basically increased.Semi-quantitative immunohistochemical analysis showed that there was no significant difference in the expression of collagen fibers between the control group and the experimental group.Conclusion:A comparative study on the effect of vocal process on pronunciation can be established through an in vitro animal model.After the vocal process resection completely healed,the tone decreased and the tone became worse,which may be that the expression of collagen fibers basically stopped 6 months after the resection of the vocal process,forming a stable scar state.the original hard cartilage tissue was replaced by relatively soft scar tissue to produce vocal cord vibration,the vibration length became longer and the tone decreased;the vibration was aperiodic and the tone became worse.After the complete healing of the vocal process resection,the pronunciation ability decreased and the sound intensity decreased,which may be caused by the posterior glottic insufficiency after the resection of the vocal process.