Effects of surface dehydration on mucosal wave amplitude and frequency in excised canine larynges

The Efficacy of the NHS Waterpipe in Superficial Hydration for People With Healthy Voices: Effects on Acoustic Voice Quality, Phonation Threshold Pressure and Subjective Sensations

OBJECTIVES

This study examined the efficacy of the NHS waterpipe as a superficial hydration treatment in voice production in healthy young women.

STUDY DESIGN

This is a prospective, single-blind, within- and between-subject experimental design.

METHODS

Thirty six female university students (mean age 24.6 years, range 19-45 years) were recruited to the study. Participants were randomized to two experimental groups (E1 and E2) and a control group. E1 underwent hydration treatment with the NHS waterpipe filled with 0.9% saline that was immersed in a cup of heated water. E2 underwent a similar treatment but without heated immersion. The control group received no treatment. Acoustic Voice Quality Index (AVQI v03.01) and its subparameters, phonation threshold pressure, self-perceived phonatory effort and sensation of throat dryness was measured at three time points (before the intervention and immediately and 15 minutes after it).

RESULTS

The Tilt of the AVQI's subparameters increased significantly in the E1 (P = 0.027) and E2 groups (P = 0.027) after the intervention. Furthermore, the E1 group had significantly lower harmonics-to-noise-ratio values at the third measurement point compared to the E2 group (P = 0.023). These findings may result from fluid transported to the vocal fold level. The sensations of throat dryness decreased in the E1 (P = 0.001) and E2 groups (P < 0.0005) after the intervention. Perceived phonatory effort decreased statistically significantly at the final measurement point in the E1 (P = 0.002) and E2 (P = 0.031) groups. No variables changed in the control group.

CONCLUSIONS

The waterpipe seems to be efficient in hydrating vocal folds on single use. It seems to be more efficient when employed with a hot water bath, albeit slightly impairing some acoustic values in the short term. Without the heated fluid, it still seems to decrease sensations of throat dryness and affect acoustic voice quality. The waterpipe does not seem to have an effect on phonation threshold pressure, and it seems to lower self-perceived effort just as efficiently whether the waterpipe is employed using a hot water bath or not. Further research is needed to prove the efficacy of long-term usage and usage with voice patients.

Hydration State and Hyaluronidase Treatment Significantly Affect Porcine Vocal Fold Biomechanics

OBJECTIVES

The understanding of vocal fold hydration state, including dehydrated, euhydrated, rehydrated tissue, and how hydration affects vocal fold biomechanical properties is still evolving. Although clinical observations support the benefits of increasing vocal fold hydration after dehydrating events, more mechanistic information on the effects of vocal fold dehydration and the beneficial effects of rehydration are needed. Alterations to hyaluronic acid (HA), an important component of the vocal fold extracellular matrix, are likely to influence the biomechanical properties of vocal folds. In this study, we investigated the influence of hydration state and HA on vocal fold tissue stiffness via biomechanical testing.

STUDY DESIGN

Prospective, ex vivo study design.

METHODS

Fresh porcine vocal folds (N = 18) were examined following sequential immersion in hypertonic (dehydration) and isotonic solutions (rehydration). In a separate experiment, vocal folds were incubated in hyaluronidase (Hyal) to remove HA. Control tissues were not exposed to any challenges. A custom micromechanical system with a microforce sensing probe was used to measure the force-displacement response. Optical strain was calculated, and ultrasound imaging was used to measure tissue cross-sectional area to obtain stress-strain curves.

RESULTS

Significant increases (P ≤ 0.05) were found in tangent moduli between dehydrated and rehydrated vocal folds at strains of ε = 0.15. The tangent moduli of Hyal-digested tissues significantly increased at both ε = 0.15 and 0.3 (P ≤ 0.05).

CONCLUSION

Vocal fold dehydration increased tissue stiffness and rehydration reduced the stiffness. Loss of HA increased vocal fold stiffness, suggesting a potential mechanical role for HA in euhydrated vocal folds.

Self-reported voice disorders of teachers and indoor air quality in schools: a cross-sectional study in Finland

OBJECTIVE

We aimed to study the association between self-reported voice disorders among teachers and indoor air quality in school buildings.

METHODS

We performed a questionnaire study of 538 Finnish teachers working in 67 school buildings utilizing both perceived and technical evaluations; the agreement between these two assessments was also studied. The technical assessment was provided by technical experts.

RESULTS

Teachers with voice disorders reported significantly more complaints from indoor air than those without voice disorders. The results also indicated a possible connection between the technical assessment and voice disorders. After adjustment for sex, stress and asthma, the prevalence of voice disorders was 47% higher in teachers working in renovated buildings compared to those working in the non-problem buildings (aRR1.47; CI 95% 1.11-1.95). The prevalence of voice disorders was 28% higher among teachers working in buildings with problems compared to those working in non-problem buildings (aRR 1.28; 95% CI 0.99-1.64).

DISCUSSION

In our study, poor perceived indoor air was significantly associated with self-reported voice disorders in teachers and there was an agreement between the perceived and technical assessments. Our results also indicated a possible connection between the technical assessment and voice disorders. Our results imply the need for longitudinal research with technical assessment to study the effect of renovation on voice disorders.

Vocal tract discomfort in caregivers for the elderly during an interval of the COVID-19 pandemic

BACKGROUND

During the coronavirus disease 2019 (COVID-19) pandemic, professional caregivers caring for the elderly may experience more vocal tract problems in addition to regular high vocal demands while wearing face masks/coverings.

METHODS AND PARTICIPANTS

Vocal tract discomfort (VTD) was assessed in 64 caregivers in one home for the elderly (64% participation rate) in June 2020 using the German version of the VTD scale.

RESULTS

More than one-half of the participating caregivers experienced VTD, described mostly as dryness, irritability, and tightness. Approximately, 80% reported that sensations were not perceived before enhanced infection prevention standards were implemented.

CONCLUSIONS

Among caregivers caring for the elderly during the COVID-19 pandemic, special care should be focused on the voice and vocal tract well-being.

RNA sequencing identifies transcriptional changes in the rabbit larynx in response to low humidity challenge

BACKGROUND

Voice disorders are a worldwide problem impacting human health, particularly for occupational voice users. Avoidance of surface dehydration is commonly prescribed as a protective factor against the development of dysphonia. The available literature inconclusively supports this practice and a biological mechanism for how surface dehydration of the laryngeal tissue affects voice has not been described. In this study, we used an in vivo male New Zealand white rabbit model to elucidate biological changes based on gene expression within the vocal folds from surface dehydration. Surface dehydration was induced by exposure to low humidity air (18.6% + 4.3%) for 8 h. Exposure to moderate humidity (43.0% + 4.3%) served as the control condition. Ilumina-based RNA sequencing was performed and used for transcriptome analysis with validation by RT-qPCR.

RESULTS

There were 103 statistically significant differentially expressed genes identified through Cuffdiff with 61 genes meeting significance by both false discovery rate and fold change. Functional annotation enrichment and predicted protein interaction mapping showed enrichment of various loci, including cellular stress and inflammatory response, ciliary function, and keratinocyte development. Eight genes were selected for RT-qPCR validation. Matrix metalloproteinase 12 (MMP12) and macrophage cationic peptide 1 (MCP1) were significantly upregulated and an epithelial chloride channel protein (ECCP) was significantly downregulated after surface dehydration by RNA-Seq and RT-qPCR. Suprabasin (SPBN) and zinc activated cationic channel (ZACN) were marginally, but non-significantly down- and upregulated as evidenced by RT-qPCR, respectively.

CONCLUSIONS

The data together support the notion that surface dehydration induces physiological changes in the vocal folds and justifies targeted analysis to further explore the underlying biology of compensatory fluid/ion flux and inflammatory mediators in response to airway surface dehydration.

Voice perturbations under the stress overload in young individuals: phenotyping and suboptimal health as predictors for cascading pathologies

Verbal communication is one of the most sophisticated human motor skills reflecting both-the mental and physical health of an individual. Voice parameters and quality changes are usually secondary towards functional and/or structural laryngological alterations under specific systemic processes, syndrome and pathologies. These include but are not restricted to dry mouth and Sicca syndromes, body dehydration, hormonal alterations linked to pubertal, menopausal, and andropausal status, respiratory disorders, gastrointestinal reflux, autoimmune diseases, endocrinologic disorders, underweight versus overweight and obesity, and diabetes mellitus. On the other hand, it is well-established that stress overload is a significant risk factor of cascading pathologies, including but not restricted to neurodegenerative and psychiatric disorders, diabetes mellitus, cardiovascular disease, stroke, and cancers. Our current study revealed voice perturbations under the stress overload as a potentially useful biomarker to identify individuals in suboptimal health conditions who might be strongly predisposed to associated pathologies. Contextually, extended surveys applied in the population might be useful to identify, for example, persons at high risk for respiratory complications under pandemic conditions such as COVID-19. Symptoms of dry mouth syndrome, disturbed microcirculation, altered sense regulation, shifted circadian rhythm, and low BMI were positively associated with voice perturbations under the stress overload. Their functional interrelationships and relevance for cascading associated pathologies are presented in the article. Automated analysis of voice recordings via artificial intelligence (AI) has a potential to derive digital biomarkers. Further, predictive machine learning models should be developed that allows for detecting a suboptimal health condition based on voice recordings, ideally in an automated manner using derived digital biomarkers. Follow-up stratification and monitoring of individuals in suboptimal health conditions are recommended using disease-specific cell-free nucleic acids (ccfDNA, ctDNA, mtDNA, miRNA) combined with metabolic patterns detected in body fluids. Application of the cost-effective targeted prevention within the phase of reversible health damage is recommended based on the individualised patient profiling.

Consecuencias laringoscópicas, electroglotográficas, acústicas y sintomatológicas producidas por la sobrecarga vocal en mujeres con voces sanas y no entrenadas

La sobrecarga es una de las etapas del continuo de carga vocal. Actualmente, se considera que su investigación permite una mejor comprensión de la patología y sintomatología funcional de la voz. El objetivo de este trabajo fue analizar las consecuencias laringoscópicas, electroglotográficas, acústicas y sintomatológicas producidas por la sobrecarga vocal en mujeres con voces sanas y no entrenadas. Se examinó el comportamiento acústico, laringoscópico, electroglotográfico y sintomatológico de 30 mujeres que se sometieron a una tarea de sobrecarga vocal caracterizada por la lectura ininterrumpida de un texto durante 60 minutos, cuya intensidad fluctuó entre los 75 y 85 dB. A nivel laringoscópico, se observó mayor vascularización, aumento de la compresión supraglótica y cambios en la amplitud, simetría y onda mucosa. Acústicamente, se evidenció incremento significativo en la frecuencia fundamental e intensidad vocal. En la electroglotografía, el cociente de cierre y la fase abierta y cerrada disminuyeron significativamente, mientras que a nivel sintomatológico, la totalidad de la muestra expresó al menos un síntoma de fatiga vocal. En conclusión, los hallazgos observados son expresiones de la fatiga del mecanismo tiroaritenoideo y de la inflamación aguda de la cubierta cordal. 

Effects of Humidification of the Vocal Tract and Respiratory Muscle Training in Women With Voice Symptoms-A Pilot Study

OBJECTIVE

The aim of this study was to determine the efficacy of a 4-week breathing exercise intervention in participants with voice symptoms.

METHODS

Six nonsmoking women (mean age 49) experiencing voice symptoms used a novel device WellO₂ for respiratory exercises that provides counter pressure during both inspiration and expiration and warms and humidifies the breathing air. Speech samples were acoustically (Acoustic Voice Quality Index) and perceptually (grade, roughness, breathiness, asthenia, and strain scale) analyzed, and perceived voice symptoms and self-reported effort in breathing and phonation were obtained. Respiratory measurements included breathing frequency and pattern, peak expiratory flow, forced vital capacity, and forced expiratory volume in 1 minute.

RESULTS

The total scores of Acoustic Voice Quality Index and some of its subcomponents (shimmer and harmonic-to-noise ratio), and the grade, roughness, and strain of the GRBAS scale indicated significantly improved voice quality. However, neither the nature or frequency of the experienced voice symptoms nor the perceived phonatory effort changed as the function of intervention. According to the participants, their breathing was significantly less effortful after the intervention, although no significant changes were observed in the objective respiratory measurements with a spirometer.

CONCLUSION

Training with the WellO₂ device has the potential to improve voice quality. The combination of inspiratory and expiratory training and warmed, humidified air is a multifaceted entity influencing several parts in the physiology of voice production. The effects of using WellO₂ need to be confirmed by further studies with a larger number of participants.

The Effect of Vocal Fold Inferior Surface Hypertrophy on Voice Function in Excised Canine Larynges

OBJECTIVE

This study aimed to explore the changes in vocal fold inferior surface hypertrophy (VFISH) on vocal fold vibration by aerodynamic and acoustic analysis. The present study allows us to gain new insights into the subglottal convergence angle (SCA), which will change with VFISH.

STUDY DESIGN

The study is prospective, and designed for repeated measures with each excised canine larynx serving as own control.

SUBJECTS AND METHODS

Three degrees of VFISH, initial, mild, and severe, were simulated by injecting different doses of fructose injections into the inferior surface of the vocal folds of 10 excised canine larynges. Computed tomographic images of the larynx were gathered, and three-dimensional models of the airway and vocal folds were reconstructed using the Mimics software. The SCA was measured from the reconstructed models. Phonation threshold flow (PTF), phonation threshold pressure (PTP), and mean flow rate (MFR) were recorded directly in the excised canine larynx phonation setup. Glottal resistance (GR), sound pressure level (SPL), fundamental frequency (F0), and formants 1-4 (F1-4) were measured when subglottal pressure (P_sub) was at 1.5 kPa or 2.5 kPa, separately. Using ordinary one-way analysis of variance, we compared the aerodynamic outcomes and voice quality among the three groups of hypertrophy.

RESULTS

The SCA, PTP, and PTF increased with the degree of VFISH. When the P_sub was controlled at 1.5 kPa or 2.5 kPa, F0 also increased significantly with the degree of VFISH of the excised canine larynges. The MFR, GR, SPL, and F1-4 had little change between the three groups and were not significantly different.

CONCLUSION

The VFISH makes onset phonation more difficult, increases the SCA, and increases the F0 in sustained phonation.

A Computational Study of Vocal Fold Dehydration During Phonation

While vocal fold dehydration is often considered an important factor contributing to vocal fatigue, it still remains unclear whether vocal fold vibration alone is able to induce severe dehydration that has a noticeable effect on phonation and perceived vocal effort. A three-dimensional model was developed to investigate vocal fold systemic dehydration and surface dehydration during phonation. Based on the linear poroelastic theory, the model considered water resupply from blood vessels through the lateral boundary, water movement within the vocal folds, water exchange between the vocal folds and the surface liquid layer through the epithelium, and surface fluid accumulation and discharge to the glottal airway. Parametric studies were conducted to investigate water loss within the vocal folds and from the surface after a 5-min sustained phonation under different permeability and vibration conditions. The results showed that the dehydration generally increased with increasing vibration amplitude, increasing epithelial permeability, and reduced water resupply. With adequate water resupply, a large-amplitude vibration can induce an overall systemic dehydration as high as 3%. The distribution of water loss within the vocal folds was non-uniform, and a local dehydration higher than 5% was observed even under conditions of a low overall systemic dehydration (<1%). Such high level of water loss may severely affect tissue properties, muscular functions, and phonations characteristics. In contrast, water loss of the surface liquid layer was generally an order of magnitude higher than water loss inside the vocal folds, indicating that the surface dehydration level is likely not a good indicator of the systemic dehydration.

Quantifying the Subharmonic Mucosal Wave in Excised Larynges via Digital Kymography

OBJECTIVES

In this paper, a nonlinear least squares fitting method was proposed to quantify subharmonic mucosal waves.

STUDY DESIGN AND METHODS

Subharmonic mucosal waves from 10 excised canine larynges were recorded using digital kymography and analyzed using nonlinear least squares and linear least squares methods. Amplitudes of fundamental and subharmonic mucosal wave components of right-upper, right-lower, left-upper, and left-lower vocal fold lips were calculated. Lastly, phase differences of fundamental and subharmonic components of the left and right vocal folds were compared.

RESULTS

The results showed that the nonlinear least squares analysis method provides a more effective complement to the linear fitting method for subharmonic mucosal wave extraction. There was a significant difference in amplitudes between the subharmonic and the fundamental components of mucosal waves (P < 0.05). The phase differences of the fundamental and the subharmonic components of the right and left vocal folds were not significantly different.

CONCLUSIONS

The application of the nonlinear least squares analysis method in digital kymography is useful for the characterization of subharmonic mucosal waves.

Vibratory Dynamics of Four Types of Excised Larynx Phonations

OBJECTIVES

There are four types of signals that are typical representations of vocal fold vibratory patterns. Type 1 signals are nearly periodic, type 2 signals contain subharmonic properties, type 3 signals are chaotic, and type 4 signals are characterized as white noise. High-speed imaging allows detailed observation of these vocal fold vibratory patterns. Therefore, high-speed imaging can explore the vibratory mechanism behind each of the four types of signals.

METHODS

The glottal area time series of the four types of vocal fold vibrations were calculated from high-speed images of 10 excised canine larynges. Nonlinear dynamic parameters of correlation dimension (D₂) and Kolmogorov entropy (K₂) were used to quantify the characteristics of the glottal areas and acoustical signals for each voice signal type.

RESULTS

The correlation dimension and Kolmogorov entropy of the glottal areas and acoustical signals for type 1, 2, and 3 voice signals were consistent with the results of previous studies. Interestingly, there was a difference between the glottal area and acoustical signals of type 4 voice signals (P < 0.001). Both the correlation dimension and Kolmogorov entropy of the type 4 glottal area were close to 0. In contrast, the type 4 acoustical signals had an infinite correlation dimension and a Kolmogorov entropy that was close to 1.

CONCLUSIONS

Turbulence in the vocal tract creates high-frequency breathiness, causing noise in the acoustical signal of type 4 voice, proving that the acoustical signal does not represent the motion mechanism behind type 4 voice. The results of this study demonstrate that high-speed imaging can provide a more accurate representation of the type 4 vocal fold vibratory pattern, and a more effective method to explore the mechanism of type 4 signals.

Spatiotemporal Quantification of Vocal Fold Vibration After Exposure to Superficial Laryngeal Dehydration: A Preliminary Study

OBJECTIVES

The aim of the study was to evaluate the effects of a superficial laryngeal dehydration challenge on vocal fold vibration in young healthy adults using high-speed video imaging.

SUBJECTS AND METHODS

In this prospective study, the effects of a 60-minute superficial laryngeal dehydration challenge on spatial (speed quotient, amplitude quotient) and temporal measures (jitter percentage, vibratory onset time) of vocal fold vibration and phonation threshold pressure (PTP) were evaluated in 10 (male = 4, female = 6) vocally normal adults (21-29 years). All measures except the vibratory onset time were measured at the 10 (low) and 80 (high) percent level of their pitch range. The vibratory onset time was obtained at habitual pitch and loudness level. Superficial laryngeal dehydration was induced by oral breathing in low ambient humidity. Prechallenge and postchallenge differences were statistically investigated using t tests with Bonferroni correction.

RESULTS

The speed quotient at low-pitch phonation significantly decreased after oral breathing of low ambient humidity. Other spatiotemporal measures and PTP at low and high pitch were not significant after challenge.

CONCLUSIONS

Results from this initial study have implications for the use of high-speed video imaging to detect and quantify the subtle changes in vocal fold vibrations after superficial dehydration in healthy individuals. Preliminary findings indicate that superficial dehydration in healthy individuals results in spatial deviations at low pitch. However, further studies are warranted to identify additional spatiotemporal changes in vocal fold vibration after superficial dehydration in normal and disordered populations.

Anticholinergic Use Is a Major Risk Factor for Dysphonia

Objective:

We hypothesize that many cases of dysphonia of unclear etiology are a form of sicca caused by anticholinergic medication use, and we aim to determine their association.

Study Design:

This was a cross-sectional study conducted over a 6-month time period. Participants were drawn from a tertiary care laryngology practice within an academic institution.

Methods:

One hundred forty-nine patients met inclusion criteria. Patients rated the symptom of chronic hoarseness; scores were compared with participants’ medication lists, comorbidities, age, and sex, and a multivariate logistic regression model was developed. Significance was set at P < .05. As a secondary analysis, participants rated a variety of other symptoms using the Voice Handicap Index-10, Reflux Symptom Index, and the GRBAS scale, which were likewise compared to anticholinergic use.

Results:

Any patient taking at least 1 anticholinergic medication had a 2.32 increased odds ( P = .03) of experiencing hoarseness. If the patient was taking 2 or more anticholinergic medications, those odds rose to 4.52 ( P = .009).

Conclusion:

This is the first study, to our knowledge, that implicates medication use as a major risk factor for dysphonia of unclear etiology. An awareness of this association is invaluable when attributing cause to hoarseness and when considering treatment options.

Quantitative Study for the Surface Dehydration of Vocal Folds Based on High-Speed Imaging

OBJECTIVES

From the perspective of the glottal area and mucosal wave, quantitatively estimate the differences of vocal fold on laryngeal activity during phonation at three different dehydration levels.

STUDY DESIGN

Controlled three sets of tests.

METHODS

A dehydration experiment for 10 excised canine larynges was conducted at 16 cm H2O. According to the dehydration cycle time (H), dehydration levels were divided into three degrees (0% H, 50% H, 75% H). The glottal area and mucosal wave under three dehydration levels were extracted from high-speed images and digital videokymography (DKG) image sequences. Direct and non-direct amplitude components were derived from glottal areas. The amplitude and frequency of mucosal wave were calculated from DKG image sequences. These parameters in condition of three dehydration levels were compared for statistical analysis.

RESULTS AND DISCUSSIONS

The results showed a significant difference in direct (P = 0.001; P = 0.005) and non-direct (P = 0.005; P = 0.016) components of glottal areas between every two different dehydration levels. Considering the right-upper, right-lower, left-upper, and left-lower of vocal fold, the amplitudes of mucosal waves consistently decreased with increasing of dehydration levels. But, there was no significant difference in frequency.

CONCLUSIONS

Surface dehydration could give rise to complex variation of vocal fold on tissues and vibratory mechanism, which should need analyzing from multiple perspectives. The results suggested that the combination of glottal area and mucosal wave could be better to research the change of vocal fold at different dehydrations. It would become a better crucial research tool for the clinical treatment of dehydration-induced laryngeal pathologies.

Climate, vocal folds, and tonal languages: Connecting the physiological and geographic dots

We summarize a number of findings in laryngology demonstrating that perturbations of phonation, including increased jitter and shimmer, are associated with desiccated ambient air. We predict that, given the relative imprecision of vocal fold vibration in desiccated versus humid contexts, arid and cold ecologies should be less amenable, when contrasted to warm and humid ecologies, to the development of languages with phonemic tone, especially complex tone. This prediction is supported by data from two large independently coded databases representing 3,700+ languages. Languages with complex tonality have generally not developed in very cold or otherwise desiccated climates, in accordance with the physiologically based predictions. The predicted global geographic-linguistic association is shown to operate within continents, within major language families, and across language isolates. Our results offer evidence that human sound systems are influenced by environmental factors.

Objective quantification of pre- and postphonosurgery vocal fold vibratory characteristics using high-speed videoendoscopy and a harmonic waveform model

PURPOSE

The model-based quantitative analysis of high-speed videoendoscopy (HSV) data at a low frame rate of 2,000 frames per second was assessed for its clinical adequacy. Stepwise regression was employed to evaluate the HSV parameters using harmonic models and their relationships to the Voice Handicap Index (VHI). Also, the model-based HSV parameters were compared with those using conventional analysis techniques.

METHOD

Eight pairs of HSV recordings of vocal folds before and after surgery for benign lesions were investigated. Five glottal area waveform features-fundamental frequency (F0), open quotient (OQ), speed index (SI), relative glottal gap (RGG), and harmonics-to-noise ratio (HNR)-were measured using model-based and conventional approaches. The statistical analyses were conducted on the mean (M) and standard deviation (SD) of the feature measurements over 1 s during sustained phonation.

RESULTS

Two model-based HSV parameters, OQ M (ρ = .67) and HNR M (ρ = -.56), were selected and explained 55% of the VHI variation. The conventional techniques yielded a regression model with OQ SD (ρ = -.60) and F0 SD (ρ = .44), explaining 61% of the VHI variation.

CONCLUSIONS

Although the selected model-based HSV parameters explained less variation in the VHI than the conventionally computed HSV parameters, the behaviors of the model-based parameters were more consistent with expectations and theory than the conventional analysis techniques.

Preliminary results on the influence of engineered artificial mucus layer on phonation

PURPOSE Previous studies have confirmed the influence of dehydration and an altered mucus (e.g., due to pathologies) on phonation. However, the underlying reasons for these influences are not fully understood. This study was a preliminary inquiry into the influences of mucus architecture and concentration on vocal fold oscillation. METHOD Two excised human larynges were investigated in an in vitro setup. The oscillations of the vocal folds at various airflow volume rates were recorded through the use of high-speed imaging. Engineered mucus containing polymers (interconnected polymers and linear polymers) was applied to the vocal folds. From the high-speed footage, glottal parameters were extracted through the use of objective methods and were compared to a gold standard (physiological saline solution). RESULTS Variations were found for all applications of mucus. Fundamental frequency dropped and the oscillatory behavior (speed quotient [SQ], closing quotient [CQ]) changed for both larynges. The 2 applied mucus architectures displayed different effects on the larynges. The interconnected polymer displayed clear low-pass filter characteristics not found for the linear polymer. Increase of polymer concentration affected parameters to a certain point. CONCLUSION The data confirm results found in previous studies. Furthermore, the different effects-comparing architecture and concentration-suggest that, in the future, synthetic mucus can be designed to improve phonation.

Kymographic imaging of laryngeal vibrations

PURPOSE OF REVIEW

Kymographic imaging is a modern method for displaying and evaluating vibratory behaviour of the vocal folds which is crucial for voice production. This review summarizes the state of the art of this method, and focuses on the progress in this area within the last 5 years.

RECENT FINDINGS

Videokymography, using a special videocamera, offers high-speed (video)kymographic images in real time, which is advantageous in daily clinical practice. Two other methods use software to create kymograms retrospectively: digital kymography processes high-speed videolaryngoscopic recordings and offers numerous research possibilities, whereas strobovideokymography processes videostroboscopic recordings, and its use is limited to regular vibration patterns. Current studies reveal that high-speed kymographic images allow more reliable visual evaluation of vibrations than by watching video recordings. Image analysis procedures have been advanced to quantify the vibration properties of the vocal folds. New information has been obtained on asymmetry, mucosal waves, irregularities, phonation onset, and nonlinear dynamic phenomena in voice disorders, as well as in singing.

SUMMARY

High-speed kymography visualizes vibratory features which are not simply observable via traditional methods. It shows large potential in better understanding the functional origin of hoarseness and unsteady phonatory states. Further research in this area is envisioned.

Mitigation of temporal aliasing via harmonic modeling of laryngeal waveforms in high-speed videoendoscopy

High-speed videoendoscopy (HSV) enables the observation and measurement of vibratory behaviors of vocal folds by capturing the laryngeal imagery at high frame rates. The frame rates of commercially available HSVs, however, are still limited to carry out sample-based time-domain objective analyses. To mitigate the resulting lack of temporal resolution, existing studies have employed sum-of-harmonics parametric models to evaluate temporal vocal-fold behaviors. This paper focuses on the other weakness of HSV: its inherent susceptibility to temporal aliasing. Aliasing occurs when there are substantial harmonics above the Nyquist frequency of the HSV camera, and video cameras offer very little means to filter out these harmonics. Although the aliasing effect in HSV data minimally affects many of the laryngeal objective parameter measurements, some parameters, such as harmonics-to-noise ratio and derivative-based parameters, are sensitive to the aliased content. The use of a parametric model with a careful selection of the number of harmonics enables classification of the aliased harmonics as a part of the harmonic signal. Glottal area waveform examples are included to illustrate the modeling capability for cases of normal and disordered vocal folds.