Typing vocal fold vibratory patterns in excised larynx experiments via digital kymography

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

PURPOSE

Voice abuse is known to be a common risk factor of voice disorders and prolonged; high-intensity phonation has been shown to damage the vocal fold epithelium. We aim to evaluate the effects of phonation on the integrity and barrier function of vocal fold epithelium using a porcine laryngeal model.

METHODS

Ex vivo porcine larynges were phonated at low intensity or high intensity for 15, 30, or 60 min within 4 h after harvest. Vocal fold epithelium was visualized using transmission electron microscopy (TEM). The barrier function of vocal fold epithelium was evaluated by measuring the permeability to model molecules, fluorescein (376 Da), and fluorescein isothiocyanate (FITC)-dextrans of 4000 and 10,000 Da (FD4, FD10), in a Franz diffusing cell.

RESULTS

Cell death and dilated intercellular space after phonation were observed using TEM. Thickness of vocal fold epithelium was significantly reduced after low-intensity phonation for 30 and 60 min and high-intensity phonation for 15, 30, and 60 min. Epithelial permeability to fluorescein was significantly increased after low-intensity phonation for 30 and 60 min, and high-intensity phonation. Permeability to FD4 was significantly increased after high-intensity phonation for 30 and 60 min. Phonation did not alter the permeability to FD10 significantly.

CONCLUSION

Long-duration phonation destroys the integrity and barrier function of vocal fold epithelium. These effects likely make vocal folds more vulnerable to other environmental irritants, such as tobacco smoke, reflux components, allergens, and inhaled pollutants. Destroyed barrier function may be an important factor in the pathogenesis of voice lesions related to voice abuse.

Establishment and Analysis of False Vocal Folds Hypertrophy Model in Excised Canine Larynges

OBJECTIVE

This study aimed to investigate the role of false vocal folds (FVFs) medialization in phonation and the acoustic impact of ventricular hypertrophy by establishing an FVF hypertrophy model.

STUDY DESIGN

A prospective in vitro experiment was carried out.

SETTING

The study was carried out using a pseudolung platform with high-speed camera in a soundproof room.

MATERIALS AND METHODS

Control, degree I, and degree II FVFs hypertrophy were simulated in 10 excised larynges via fructose injection of 0.1 mL for degree I and 0.25 mL for degree II. Mean flow rate (MFR), fundamental frequencies (F0), formants, and sound pressure level were measured with a subglottal pressure of 1.5 kPa and 2.5 kPa, respectively.

RESULTS

When the subglottal pressure was controlled at both at 1.5 kPa and at 2.5 kPa, the degree of FVF hypertrophy significantly influenced the distribution of the formants, F0, and MFR in excised canine larynges. Increasing the degree of hypertrophy was associated with a decrease in F0 and an increase in MFR. In degree II FVF hypertrophy models, the sound pressure level and the first formant were significantly higher (P < 0.05) than in normal models.

CONCLUSION

Hypertrophy of the FVFs has a significant influence on the distribution of sound energy and is associated with changes in sound quality.

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.

State of the art laryngeal imaging: research and clinical implications

PURPOSE OF REVIEW

This study provides a review of the latest advances in videostroboscopy, videokymography and high-speed videoendoscopy, and outlines the development of new laryngeal imaging modalities based on optical coherence tomography, laser-depth kymography, and magnetic resonance imaging (MRI), published in the past 2 years.

RECENT FINDINGS

Videostroboscopy and videokymography: Image quality has improved and several image processing and measurement techniques have been published. High-speed videoendoscopy: Significant progress has been made through increased sensitivity and frame rates of the cameras, and the development of facilitative playbacks, phonovibrography and several image segmentation and measurement methods. Clinical evidence was presented through applications in phonosurgery, comparisons with videostroboscopy, normative data, and better understanding of voice production. Optical coherence tomography: Latest developments allow the capture of dynamic high-resolution cross-sectional images of the vibrating vocal fold mucosa during phonation. Depth kymography: New laser technique allowing recording of the vertical movements of the vocal folds during phonation in calibrated spatial values. Laryngeal magnetic resonance: New methods allow high-resolution imaging of laryngeal tissue microstructure, or measuring of dynamic laryngeal structures during phonation.

SUMMARY

The endoscopic laryngeal imaging techniques have made significant advances increasing their clinical value, whereas techniques providing new types of potentially clinically relevant information have emerged.

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.

Vocal fold vibration amplitude, open quotient, speed quotient and their variability along glottal length: kymographic data from normal subjects

Abstract Quantitative knowledge about healthy vocal fold vibration characteristics provides the basis for an objective assessment of vocal fold vibrations. In this study, using high-speed videolaryngoscopy the alterations of the relative vibration amplitudes, open quotients, and speed quotients were analyzed along the glottal length in 30 male and 30 female healthy subjects. The maximum vibration amplitude was identified at 41.1% ± 10.8% and 46.5% ± 18.0% of the visible glottal length in females and males, respectively. The average open quotients decreased in females and males from posterior to anterior, while the speed quotients did not change systematically. The reported normative values can be used to distinguish normal and abnormal vibrations in clinical practice when aiming at quantitative diagnosis of functional voice disorders.

Experiments on Analysing Voice Production: Excised (Human, Animal) and In Vivo (Animal) Approaches

Experiments on human and on animal excised specimens as well as in vivo animal preparations are so far the most realistic approaches to simulate the in vivo process of human phonation. These experiments do not have the disadvantage of limited space within the neck and enable studies of the actual organ necessary for phonation, i.e., the larynx. The studies additionally allow the analysis of flow, vocal fold dynamics, and resulting acoustics in relation to well-defined laryngeal alterations.

PURPOSE OF REVIEW

This paper provides an overview of the applications and usefulness of excised (human/animal) specimen and in vivo animal experiments in voice research. These experiments have enabled visualization and analysis of dehydration effects, vocal fold scarring, bifurcation and chaotic vibrations, three-dimensional vibrations, aerodynamic effects, and mucosal wave propagation along the medial surface. Quantitative data will be shown to give an overview of measured laryngeal parameter values. As yet, a full understanding of all existing interactions in voice production has not been achieved, and thus, where possible, we try to indicate areas needing further study.

RECENT FINDINGS

A further motivation behind this review is to highlight recent findings and technologies related to the study of vocal fold dynamics and its applications. For example, studies of interactions between vocal tract airflow and generation of acoustics have recently shown that airflow superior to the glottis is governed by not only vocal fold dynamics but also by subglottal and supraglottal structures. In addition, promising new methods to investigate kinematics and dynamics have been reported recently, including dynamic optical coherence tomography, X-ray stroboscopy and three-dimensional reconstruction with laser projection systems. Finally, we touch on the relevance of vocal fold dynamics to clinical laryngology and to clinically-oriented research.

Multiparameter comparison of injection laryngoplasty, medialization laryngoplasty, and arytenoid adduction in an excised larynx model

OBJECTIVES/HYPOTHESIS

Evaluate the effect of injection laryngoplasty (IL), medialization laryngoplasty (ML), and ML combined with arytenoid adduction (ML-AA) on acoustic, aerodynamic, and mucosal wave measurements in an excised larynx setup.

STUDY DESIGN

Comparative case study using ex vivo canine larynges.

METHODS

Measurements were recorded for eight excised canine larynges with simulated unilateral vocal fold paralysis before and after vocal fold injection with Cymetra. A second set of eight larynges was used to evaluate medialization laryngoplasty using a Silastic implant without and with arytenoid adduction.

RESULTS

IL and ML led to comparable decreases in phonation threshold flow (PTF), phonation threshold pressure (PTP), and phonation threshold power (PTW). ML-AA led to significant decreases in PTF (P = .008), PTP (P = .008), and PTW (P = .008). IL and ML led to approximately equal decreases in percent jitter and percent shimmer. ML-AA caused the greatest increase in signal-to-noise ratio. ML-AA discernibly decreased frequency (P = 0.059); a clear trend was not observed for IL or ML. IL significantly reduced mucosal wave amplitude (P = 0.002), whereas both ML and ML-AA increased it. All procedures significantly decreased glottal gap, with the most dramatic effects observed after ML-AA (P = 0.004).

CONCLUSIONS

ML-AA led to the greatest improvements in phonatory parameters. IL was comparable to ML aerodynamically and acoustically, but caused detrimental changes to the mucosal wave. Incremental improvements in parameters recorded from the same larynx were observed after ML and ML-AA. To ensure optimal acoustic outcome, the arytenoid must be correctly rotated. This study provides objective support for the combined ML-AA procedure in tolerant patients.