Robert E. Hillman

Clinical implementation of laryngeal high-speed videoendoscopy: Challenges and evolution

High-speed videoendoscopy (HSV) captures the true intracycle vibratory behavior of the vocal folds, which allows for overcoming the limitations of videostroboscopy for more accurate objective quantification methods. However, the commercial HSV systems have not gained widespread clinical adoption because of remaining technical and methodological limitations and an associated lack of information regarding the validity, practicality, and clinical relevance of HSV. The purpose of this article is to summarize the practical, technological and methodological challenges we have faced, to delineate the advances we have made, and to share our current vision of the necessary steps towards developing HSV into a robust tool. This tool will provide further insights into the biomechanics of laryngeal sound production, as well as enable more accurate functional assessment of the pathophysiology of voice disorders leading to refinements in the diagnosis and management of vocal fold pathology. The original contributions of this paper are the descriptions of our color high-resolution HSV integration, the methods for facilitative playback and HSV dynamic segmentation, and the ongoing efforts for implementing HSV in phonomicrosurgery, as well as the analysis of the challenges and prospects for the clinical implementation of HSV, additionally supported by references to previously reported data.

Temporal and spectral estimations of harmonics-to-noise ratio in human voice signals

The quantity, harmonic-to-noise ratio (HNR), has been used to estimate the level of noise in human voice signals. HNR estimation can be accomplished in two ways: (1) on a time-domain basis, in which HNR is computed directly from the acoustic waveform; and (2) on a frequency-domain basis, in which HNR is computed from a transformed representation of the waveform. An algorithm for computing HNR in the frequency domain was modified and tested in the work described here. The modifications were designed to reduce the influence of spectral leakage in the computation of harmonic energy, and to remove the necessity of spectral baseline shifting prescribed in one existing algorithm [G. de Krom, J. Speech Hear. Res. 36, 254-266 (1993)]. Frequency-domain estimations of HNR based on this existing algorithm and our modified algorithm were compared to time-domain estimations on synthetic signals and human pathological voice samples. Results indicated a highly significant, linear correlation between frequency- and time-domain estimations of HNR for our modified approach.

Glottal airflow and transglottal air pressure measurements for male and female speakers in low, normal, and high pitch

Summary Measurements on the inverse filtered airflow waveform and of estimated average transglottal pressure and glottal airflow were made from syllable sequences in low, normal, and high pitch for 25 male and 20 female speakers. Correlation analyses indicated that several of the airflow measurements were more directly related to voice intensity than to fundamental frequency (F 0 ). Results suggested that pressure may have different influences in low and high pitch in this speech task. It is suggested that unexpected results of increased pressure in low pitch were related to maintaining voice quality, that is, avoiding vocal fry. In high pitch, the increased pressure may serve to maintain vocal fold vibration. The findings suggested different underlying laryngeal mechanisms and vocal adjustments for increasing and decreasing F 0 from normal pitch.

Mobile Voice Health Monitoring Using a Wearable Accelerometer Sensor and a Smartphone Platform

Many common voice disorders are chronic or recurring conditions that are likely to result from faulty and/or abusive patterns of vocal behavior, referred to generically as vocal hyperfunction. An ongoing goal in clinical voice assessment is the development and use of noninvasively derived measures to quantify and track the daily status of vocal hyperfunction so that the diagnosis and treatment of such behaviorally based voice disorders can be improved. This paper reports on the development of a new, versatile, and cost-effective clinical tool for mobile voice monitoring that acquires the high-bandwidth signal from an accelerometer sensor placed on the neck skin above the collarbone. Using a smartphone as the data acquisition platform, the prototype device provides a user-friendly interface for voice use monitoring, daily sensor calibration, and periodic alert capabilities. Pilot data are reported from three vocally normal speakers and three subjects with voice disorders to demonstrate the potential of the device to yield standard measures of fundamental frequency and sound pressure level and model-based glottal airflow properties. The smartphone-based platform enables future clinical studies for the identification of the best set of measures for differentiating between normal and hyperfunctional patterns of voice use.

Aerodynamic and acoustic voice measurements of patients with vocal nodules: variation in baseline and changes across voice therapy.

An important clinical issue concerns the efficacy of current voice therapy approaches in treating voice disorders, such as vocal nodules. Much research focuses on finding reliable methods for documentation of treatment results. In this second treatment study of ten patients with vocal nodules, who participated in a behaviorally based voice therapy program, 11 aerodynamic (transglottal air pressure and glottal waveform) and acoustic (spl, f0, and spectrum slope) measures were used. Three pretherapy baseline assessments were carried out, followed by one assessment after each of five therapy phases. Measurements were made of two types of speech materials: Strings of repeated /pae/ syllables and sustained /ae/ phonations in two loudness conditions: comfortable loudness and loud voice. The data were normalized using z-scores, which were based on data from 22 normal subjects. The results showed that the aerodynamic measures reflected the presence of vocal pathology to a higher degree than did the acoustic spectral measures, and they should be useful in studies comparing nodule and normal voice production. Large individual session-to-session variation was found for all measures across pretherapy baseline recordings, which contributed to nonsignificant differences between baseline and therapy data.

Ambulatory monitoring of disordered voices

Objectives: Recently developed systems for ambulatory monitoring of voice use employ miniature accelerometers placed at the base of the anterior neck to sense phonation. As it is hoped that such systems will help improve the clinical assessment and management of voice disorders, this study was undertaken to determine the impact of dysphonia severity on the accuracy of accelerometer-based estimates of vocal function. Methods: Simultaneous recordings were made of oral acoustic (microphone) and neck skin acceleration signals for 6 normal speakers and 18 patients with voice disorders (mild to severe dysphonia) as they performed several speech tasks. Measures of phonation time, fundamental frequency, and sound pressure level were extracted from the Two types of signals and compared. Results: It was generally demonstrated that accelerometer-based measures closely approximated corresponding measurements obtained from a microphone signal across all levels of dysphonia severity. Furthermore, there was evidence that in some cases the accelerometer may actually represent a more robust approach for estimating phonation parameters in disordered voices. Conclusions: The results generally support the recent application of accelerometers as phonation sensors in ambulatory voice monitoring systems that can be used in the clinical assessment and management of voice disorders.

Phonomicrosurgery in singers and performing artists: treatment outcomes, management theories, and future directions.

Phonomicrosurgery in performing artists has historically been approached with great trepidation, and vocal outcome data are sparse. The vocal liability of surgically disturbing the superficial lamina propria (SLP) and epithelium must be balanced with the inherent detrimental vocal effect of the lesion(s). A prospective investigation was performed on 185 performing artists who underwent phonomicrosurgical resection of 365 lesions: 201 nodules, 71 polyps, 66 varices and ectasias, 13 cysts, 8 keratotic lesions. 2 granulomas, 2 Reinkes edema, and 2 papillomas. Nearly all patients with SLP lesions reported improvement in their postsurgical vocal function. This subjective result was supported by objective acoustic and aerodynamic measures. All postsurgical objective vocal function measures fell within normal limits, including a few that displayed presurgical abnormalities. However, given the relative insensitivity of standard objective measures to assess higher-level vocal performance-related factors, it is even more noteworthy that 8 of 24 objective measures displayed statistically significant postsurgical improvements in vocal function. Such changes in objective measures mostly reflect overall enhancement in the efficiency of voice production. Phonomicrosurgical resection of vocal fold lesions in performing artists is enjoying an expanding role because of a variety of improvements in diagnostic assessment, surgical instrumentation and techniques, and specialized rehabilitation. Most of these lesions are the result of phonotrauma and arise within the SLP. Successful management depends on prudent patient selection and counseling, ultraprecise technique, and vigorous vocal rehabilitation. Furthermore, an understanding of the vocal function and dysfunction of this high-performance population provides all otolaryngologists who manage laryngeal problems with valuable information that they can extrapolate for use in their practices.

Voice and treatment outcome from phonosurgical management of early glottic cancer.

Phonosurgical management of early glottic cancer has evolved considerably, but objective vocal outcome data are sparse. A prospective clinical trial was done on 32 patients with unilateral cancer (T1a in 28 and T2a in 4) who underwent ultranarrow-margin resection; 15 had resection superficial to the vocal ligament, and 17 deep to it. The subepithelial infusion technique facilitated selection of these patients for the appropriate procedure. All are cancer-free without radiotherapy or open surgery. Involvement of the anterior commissure (22/32) or the vocal process (15/32) of the arytenoid cartilage did not influence local control. Nine of 17 patients had resection of paraglottic musculature, and all underwent medialization reconstruction by lipoinjection and/or Gore-Tex laryngoplasty. Eight of the 17 had resections deep to the vocal ligament, but without vocalis muscle, and 1 of the 8 underwent medialization. Posttreatment vocal function measures were obtained for all patients. A clear majority of the patients displayed normal values for average fundamental frequency (72%) during connected speech, and normal noise-to-harmonics ratio (75%) and average glottal airflow (91%) measures during sustained vowels. Smaller majorities of patients displayed normal values for average sound pressure level (SPL; 59%) during connected speech and for maximum ranges for fundamental frequency (56%) and SPL (59%). Fewer than half of the patients displayed normal values for sustained vowel measures of jitter (45%), shimmer (22%), and maximum phonation time (34%). Almost all patients had elevated subglottal pressures and reduced values for the ratio of SPL to subglottal pressure (vocal efficiency). There were significant improvements in a majority of patients for most vocal function measures after medialization reconstruction. Normal or near-normal conversation-level voices were achieved in most cases, regardless of the disease depth, by utilization of a spectrum of resection and reconstruction options. These favorable results are based on establishing aerodynamic glottal competency and preserving the layered microstructure of noncancerous glottal tissue.

Stroboscopic Assessment of Vocal Fold Keratosis and Glottic Cancer

Disruption of the normal viscoelastic properties of the superficial lamina propria (SLP) results in aberrant vocal fold vibration and mucosal wave propagation. Therefore, an investigation was performed to determine whether stroboscopy is a reliable method for 1) differentiating invasive glottic carcinoma from intraepithelial atypia or 2) determining the depth of cancer invasion. An analysis was done on the preoperative vocal fold vibration characteristics of 62 keratotic (intraepithelial, 45; cancer, 17) lesions that were subsequently resected by means of microlaryngoscopy. Histopathology and intraoperative mapping were used to specify the depth of invasion. A panel of 4 blinded judges was used to assess the amplitude of vocal fold vibration and the magnitude of mucosal wave activity in the region of the lesion from videostroboscopic recordings. The final comparative data set comprised only those ratings that achieved at least 75% interjudge agreement. Of the 28 intraepithelial lesions that could be reliably evaluated for amplitude of vocal fold vibration, only 2 were normal, with the amplitude reduced in 24 and absent in 2. Of the 30 intraepithelial lesions in which mucosal wave activity could be reliably assessed, only 2 were normal, with the wave reduced in 24 and absent in 4. Furthermore, amplitude of vocal fold vibration and magnitude of mucosal wave propagation were absent in 2 of 4 carcinomas in which the depth of microinvasion did not reach the vocal ligament. According to the findings herein, reduced amplitude of vocal fold vibration and/or mucosal wave propagation associated with keratosis did not reliably predict the presence of cancer or the depth of cancer invasion into the laminae propriae. However, the presence of a flexible mucosal wave probably indicates that there is not extensive vocal ligament invasion. Reductions in the amplitude of vocal fold vibration and in mucosal wave magnitude were usually noted in intraepithelial atypia, despite the fact that there was no invasion into the SLP. The reduced epithelial pliability could be due to bulky keratosis and/or alteration of the SLP occurring as a result of inflammation or fibrovascular scarring.

Teflon Granuloma of the Larynx: Etiology, Pathophysiology, and Management

Intralaryngeal Teflon injection for correction of unilateral vocal cord paralysis is known to produce a foreign body giant cell reaction. In our practice, we have seen increasing numbers of patients who had developed dysphonia related to Teflon injection. This patient series was reviewed, as were the surgical technique to correct this condition, voice results, and acoustic analysis of a subset of the patient series. We conclude that dysphonia, secondary to Teflon injection, can be either from overinjection of Teflon or inappropriate injection, or from the proliferative granulomatous response of the larynx to the Teflon. Our technique of laser incision into the superior aspect of the Teflon implant, followed by vaporization and preservation of a margin of mucosa of the cord medially, resulted in improved voice in 8 of 11 patients treated in this manner. Acoustic and aerodynamic analyses reveal significant deficits in vocal function that may persist after procedures used to correct this condition.