Prolonged phonation impairs the integrity and barrier function of porcine vocal fold epithelium: a preliminary study

Does Vocal Fatigue Negatively Affect Low Vocal Range in Professional, Female Opera Singers? A Survey Study and Single-Subject Pilot Study

OBJECTIVE

1. To survey how vocal fatigue manifests itself in the vocal range of a sample of professional, female opera singers. 2. To assess laryngeal videostroboscopic changes of one professional, female opera singer before and after extended operatic singing.

METHODS

Survey study: 296 professional, female opera singers were recruited to participate in an anonymous research survey querying the temporary impact of vocal fatigue in professional, female opera singers. 46.3% of participants described themselves as singing mainstage roles at large, A-level opera houses. Singers were asked to report where in their vocal range they experienced the effects of vocal fatigue and could choose more than one response. Single-subject study: One professional, female opera singer (the author) underwent two laryngeal videostroboscopic exams pre and post vocal loading. The exams were evaluated and compared independently by two blinded laryngologists.

RESULTS

The results of the survey found that 42.9% of the total responses from professional, female opera singers indicated a temporary impact on the lower middle range (≈C4-F4) as a result of vocal fatigue. 36.5% of participants experienced a temporary impact on their lowest range (≈below C4) and 19.6% reported a temporary impact on their higher range due to vocal fatigue. The results of the single-subject study showed reduced glottal closure pattern in the postloading, lower middle range, head voice condition.

CONCLUSIONS

A large proportion (64.9%) of the professional, female opera singers surveyed reported increased difficulty navigating their lower middle range and/or lowest range after extended operatic singing. These results support the single-subject study, which found that after vocal loading, there was a decrease in glottal competence while singing in head voice in the lower middle range.

Eliciting and Characterizing Porcine Vocalizations: When Pigs Fly

BACKGROUND/OBJECTIVES

While voice-related therapeutic interventions are often researched preclinically in the porcine model, there are no well-established methods to induce porcine glottic phonation. Described approaches, such as training animals to phonate for positive reinforcement are time-consuming and plagued by inherent variability in the type of phonation produced and contamination of background noise. Thus, a reliable method of assessing glottic phonation in the porcine model is needed.

METHODS

In this study, we have created a novel pulley-based apparatus with harness for "pig-lifting" with surrounding acoustic insulation and high-directional microphone with digital recorder for recording phonation. Praat and Matlab were used to analyze all porcine vocalizations for fundamental frequency (F0), intensity, duration of phonation and cepstral peak prominence (CPP). Glottic phonation was detected using F0 (≥2000 hz), duration (≥3 seconds) and researcher perceptual judgment. Partial-glottic phonations were also analyzed. Reliability between researcher judgment and acoustic measures for glottic phonation detection was high.

RESULTS

Acoustic analysis demonstrated that glottic and partial-glottic phonation was consistently elicited, with no formal training of the minipigs required. Glottic vocalizations increased with multiple lifts. Glottic phonation continued to be elicited after multiple days but became less frequent. Glottic and partial-glottic phonations had similar CPP values over the 6 experimental days.

CONCLUSION

Our cost-effective, reliable method of inducing and recording glottic phonation in the porcine model may provide a cost effective, preclinical tool in voice research.

The integrity and barrier function of porcine vocal fold epithelium: its susceptibility to damage by deoxycholic acid compared with pepsin

PURPOSE

In this study, we aim to systematically evaluate the damaging role of gastric (pepsin and acid) and duodenal ingredients (bile acids) on vocal fold epithelium in excised porcine larynges.

METHODS

Fresh ex vivo porcine larynges were exposed to one of five experimental conditions for 1 h. These conditions will be referred to as alkaline deoxycholic acid, acidic pepsin, acid pH3 only, acid pH5 only, and control, respectively. A Franz diffusing cell was used to evaluate the barrier function of vocal fold epithelium by measuring the permeability to fluorescein isothiocyanate dextran of 4 kDa. Histological changes were observed using transmission electron microscopy.

RESULTS

After immersing the fresh porcine larynges in the five solution groups, we found that the vocal fold epithelium in the deoxycholic acid group had more permeability to FD4 than the pepsin group (P < 0.001). Fragmentation and desquamation of dead cell layers were observed in both the pepsin and deoxycholic acid groups, but were more severe in the deoxycholic acid group than the pepsin group. The thickness of the dead epithelial cell layer gradually increased with increasing acid concentration (P < 0.05). Additionally, the thickness of the dead epithelial cell layer in the deoxycholic acid group was significantly higher than that in the pepsin group (P < 0.01).

CONCLUSION

Deoxycholic acid in a weakly acidic condition is more likely than pepsin to induce apoptosis in ex vivo porcine vocal fold epithelium, destroy the link proteins between epithelial cells, and affect their integrity and barrier function.