Several studies involving excised animal larynges have been performed to simulate the structural and physiological properties of the human larynx. The most common way to preserve the laryngeal tissue being studied is by immersing it in a 0.9% isotonic saline solution and then flash freezing it. Isotonic saline is used empirically to replenish the potential ion loss that occurs postmortem. Each larynx is flash frozen so it can be used at a more convenient time while still maintaining the integrity of the tissue. However, the preservation methods found in previous studies tend to vary and no consensus had been reached about which method of preservation is ideal. This study sought to investigate the effects of solution and storage on phonation threshold pressure (PTP). Phonation threshold pressure is commonly used to investigate mucosal wave of the vocal folds, prephonatory glottal width, and vocal fold cover. This study involved a prospective, mixed experimental design with three groups, including a control group and two experimental groups. Each group consisted of 10 bench-mounted porcine larynges. The control group was immersed in 0.9% isotonic saline, flash frozen with liquid nitrogen within 24 hours postmortem, and thawed overnight before the experiment. The second group was immersed in 0.9% isotonic saline and the third group was submersed in Ringer's solution. Each of these groups was kept in their solution in a refrigerator for approximately 15 hours and was used for the experiment within 24 hours postmortem. Each larynx was mounted on a bench on a tabletop with three micropositioners to adduct and elongate the vocal folds. A pseudolung connected to the trachea directed humidified air to the vocal folds subglottally until phonation was achieved. The larynges in all three groups underwent these phonatory trials with 5-minute desiccation trials between each until phonation could no longer be achieved. Phonation threshold pressure was then observed and compared within groups and between groups. The signals were obtained using MATLAB. The results indicated that PTP was lowest for the frozen versus fresh groups. PTP values increased slightly for the frozen group, but the frozen group demonstrated less variability across specimens as compared to the fresh groups. Collectively, these results indicate that there are substantial differences between fresh and frozen specimens. These differences should be considered when designing tissue studies for purposes of generalization to human phonation.
College and Department
David O. McKay School of Education; Communication Disorders
BYU ScholarsArchive Citation
Pipkin Litster, Chelsea Savannah, "Effects of Larynx Preservation Method on Phonation Threshold Pressure in an Excised Porcine Benchtop Model" (2018). Theses and Dissertations. 7433.
Larynx preservation, bench model, phonation threshold pressure, Ringer's solution, laryngeal desiccation