The effect of subglottal resonance upon vocal fold vibration

An experiment with excised larynges was undertaken to investigate theinteraction between acoustic pressures in a pseudotrachea and the amplitude of vibration of the vocal folds. Pressure was measured beneath the vocal folds at three specific moments of the vibratory cycle: (a) when the superior margin of the vocal folds began to separate, (b) when the vocal folds were maximally apart, and (c) when the inferior margin of the vocal folds began to touch. Results indicate that in half the larynges investigated, the maximum amplitude of vibration increased as a function of: (a) increased positive pressure at the moment of opening, and (b) reduced subglottal pressure when the vocal folds were maximally apart. The implications of these experiments regarding involuntary register transitions related to trachea resonance are discussed in light of a previously proposed register theory.     

Investigation of vocal fold impact stress in human subjects

The primary purpose of the study was to explore a methodology for measuring vocal fold impact stress (SI) in awake humans, and to provide information about the general magnitude of SIs that may occur at the midpoint of the membranous vocal folds during phonation. A secondary purpose was to examine the potential use of the electroglottographic closed quotient (EGG CQ) to indirectly reflect SI. Seven male and 13 female adults were enrolled as subjects, of whom 18 had normal larynges and normal voices, 1 had nodules, and 1 had vocal fold paresis and bowing. Subjects attempted to produce 3 different voice types (pressed, normal, breathy), at 3 different pitches (low, medium, high) and 3 different loudness levels (quiet, medium, loud). For a first set of trials, only EGG data were collected. For a second set, a sensor was also introduced to the midmembranous glottis for the collection of SI data. The primary findings were that (1) endolaryngeal sensor placement was achieved during phonation trials for 17 of 20 subjects; however, grossly consistent anteroposterior positioning was accomplished, and analyzable data were obtained, for only 7 subjects; (2) SIs ranged from less than 1 kPa to about 3 kPa for those 7 subjects; and (3) no relation was detected between simultaneous CQs and SIs for individual data, although a relation was reported in a prior canine study. One possible reason for the failure to show such a relation in the present study was subtle variations in vertical as well as anteroposterior positioning of the sensor during the trials. Future studies should focus on developing a methodology for ensuring invariant 3-dimensional sensor positioning between the membranous folds, so that the stability of both SI and simultaneous CQ data can be improved.     

Allergies and vocal fold edema: A preliminary report

This paper describes different tools to rule out the etiology of vocal fold edema. A complete voice assessment is used in our Voice Center. This includes patient history, acoustic analysis, laryngeal video-stroboscopy, otolaryngology consultation, allergy testing from our Allergy Clinic, and gastroenterology consultation as appropriate. Inhalant allergy can be a hidden, yet very common cause of chronic laryngitis. Respiratory allergies can also cause decreased pulmonary function; excessive secretions in either the lower airway, trachea, bronchi or in the upper airway of the pharynx; edema of the vocal folds themselves; and unusual resonance characteristics of the pharynx or nasal cavity due to congestion of the membrane in those areas. Voice patients with a history of seasonal hay fever, a history of allergic reactions around cats or dogs, or a strong family history of allergies should be allergy tested. Screening tests for allergies are available, which include a screening radioallergosorbent test or a screening panel of scratch or intradermal skin tests. Once specific allergens are identified, recommendations for therapy or other intervention can be made. Straining the voice, in combination with the above conditions, can increase the voice problem. The histories, allergy test results, and voice laboratory evaluations of several patients are described. Identifying these voice patients and treating their allergies are important in keeping these patients healthy and maintaining a clear, good voice quality. The multidisciplinary approach in voice disorders is indispensable in diagnosis and treatment of these disorders.     

Phonomicrosurgical management of vocal fold polyps: The subepithelial microflap resection technique

Vocal fold polyps are typically caused by acute and chronic trauma to the microvasculature of the superficial lamina propria (SLP). Shearing stresses that are induced by hyperfunctional glottal sound production lead to bleeding into the SLP and malformed neo-vascularized masses. Because the primary process does not involve the epithelium, the authors designed a technique to resect hemorrhagic polyps by epithelial cordotomy with partial or complete preservation of the vocal fold epithelium. This approach is different from the traditional microsurgical resection of hemorrhagic polyps by amputation with or without the carbon dioxide laser. Forty patients who underwent microlaryngoscopic resection of hemorrhagic polyps from 1996 through 1998 were reviewed retrospectively. Thirty-six of the 40 procedures were by epithelial cordotomy and subepithelial removal of the polyp contents. Sixteen of 36 were assisted by a subepithelial infusion of saline and epinephrine, and all were 3 mm to 6 mm. Four of 40 polyps were amputated; all of these were less than 3 mm and were pedicled on a narrow base. Cold instruments were used exclusively in all 40 patients. Postoperative laryngeal stroboscopy within 2 weeks revealed improved mucosal wave propagation and improved glottal closure in all 33 patients in whom postoperative strobovideolaryngoscopy was available. The epithelial cordotomy technique was introduced to minimize disturbance of normal SLP and epithelium. Despite the hemorrhagic nature of these lesions, cold instruments could be used exclusively with facility due to careful microdissection between the polyp and the residual normal SLP and the enhanced hemostasis provided by the subepithelial infusion of saline and epinephrine. The rapid return to improved glottal function is the result of this ultra tissue-sparing technique.     

Videokymography: High-speed line scanning of vocal fold vibration

A digital technique for high-speed visualization of vibration, called videokymography, was developed and applied to the vocal folds. The system uses a modified video camera able to work in two modes: high-speed (nearly 8,000 images/s) and standard (50 images/s in CCIR norm). In the high-speed mode, the camera selects one active horizontal line (transverse to the glottis) from the whole laryngeal image. The successive line images are presented in real time on a commercial TV monitor, filling each video frame from top to bottom. The system makes it possible to observe left-right asymmetries, open quotient, propagation of mucosal waves, movement of the upper and, in the closing phase, the lower margins of the vocal folds, etc. The technique is suitable for further processing and quantification of recorded vibration.     

Interstitial protein alterations in rabbit vocal fold with scar

Fibrous and interstitial proteins compose the extracellular matrix of the vocal fold lamina propria and account for its biomechanic properties. Vocal fold scarring is characterized by altered biomechanical properties, which create dysphonia. Although alterations of the fibrous proteins have been confirmed in the rabbit vocal fold scar, interstitial proteins, which are known to be important in wound repair, have not been investigated to date. Using a rabbit model, interstitial proteins decorin, fibromodulin, and fibronectin were examined immunohistologically, two months postinduction of vocal fold scar by means of forcep biopsy. Significantly decreased decorin and fibromodulin with significantly increased fibronectin characterized scarred vocal fold tissue. The implications of altered interstitial proteins levels and their affect on the fibrous proteins will be discussed in relation to increased vocal fold stiffness and viscosity, which characterizes vocal fold scar.     

Ultrastructural study of muscle in vocal fold: postmortem damage observations

Various authors have published results related to the ultrastructure of vocal folds in specific areas proceeding from human cadavers. Nevertheless, starting from the premise that a fundamental principle of sampling and the samples should be a true representative of the whole, the authors decided to examine vocal folds from human cadavers and compare them to normal vocal folds from the guinea pig (Cavia porcellus). The findings of these authors demonstrated clearly that the conclusion of Rhodin (1954) is correct, that a biological sample must be preserved immediately after blood circulation ceases, and that the intermediary time between biopsy and fixation cannot be more than 3 minutes. Cells fixed a few hours after death appeared disaggregated, and many of their endocellular components were profoundly altered. The results obtained by the authors suggests that ultrastructural studies with cadaverous material may lead to serious risks or doubts about the accuracy of the results and consequently result in dubious interpretations.     

Strobophotoglottographic transillumination as a method for the analysis of vocal fold vibration patterns

The purpose of this exploratory study was to determine if laryngeal transillumination in combination with stroboscopy (strobophotoglottography; SPGG) is useful for (1) the visualization of vocal fold vibration (VFV) opening patterns, (2) the localization of initial vocal fold opening in horizontal glottal thirds (anterior, midmembranous, and posterior), (3) determination of the temporal correspondence of the so-called electroglottography (EGG)-knee and initial vocal fold separation, and, finally, (4) automatized quantitative measurements of glottal area function within endoscopic images. With stroboscopic transillumination, initial inferior vocal fold separation was detectable during the "closed" phase, where the vocal folds were still closed in the upper portion and therefore initial inferior vocal fold separation could not be visualized with usual laryngoscopy techniques. In the horizontal plane within similar fundamental frequencies in modal voice registers in two male subjects, localization of initial glottal opening depended on the voice types used (soft, normal, or pressed phonation). We found zipperlike posterior-to-anterior openings, initial midmembranous openings, initial anterior openings, as well as simultaneous initial opening of all three portions in the two healthy male adults examined. This technique proved to add temporal and spatial information to vocal fold opening patterns and extends our examination techniques to the very beginning of vocal fold opening at the inferior portion. Simultaneous electroglottogram tracking and comparison with bidirectionally illuminated stroboscopic images revealed a time-locked correspondence of the EGG-knee with the aforementioned initial inferior vocal fold separation. Bidirectional illumination combined with digital color extraction techniques allowed for image separation of subglottally and supraglottally illuminated structures. This facilitated vocal fold contour detection and automatized image processing, for example, for determination of glottal area function, and is considered to be a further step to objective automatized quantitative measurements within endoscopic images.     

Long-term preservation of voice improvement following surgical medialization and reinnervation for unilateral vocal fold paralysis

In June of 1996, we reported improved functional voice results when reinnervation was combined with surgical medialization for unilateral vocal fold paralysis. In addition, it was noted that further wasting of the reinnervated vocal fold was prevented in 96% of these patients beyond 2 years' follow-up. The study reported here compares the long-term preservation of voice improvement achieved by surgical medialization alone with that resulting from combined medialization and nerve-muscle pedicle reinnervation. Further significant wasting of the paralyzed vocal fold with voice deterioration from that achieved by surgical medialization alone was noted between 6 months and 2 years postoperatively in 28% of patients, while only 4% of those undergoing combined reinnervation demonstrated this finding at a minimum of 2 years' follow-up.     

Rhabdomyoma of the true vocal fold

Rhabdomyomas of the larynx are exceedingly rare. The incidence, sites of occurrence in the larynx, and treatment of these benign striated muscle tumors are reviewed. A case of rhabdomyoma involving the vocalis muscle is presented with magnetic resonance imaging and video-stroboscopic documentation.     

Correspondence of electroglottographic closed quotient to vocal fold impact stress in excised canine larynges

The purpose of this study was to explore the possible use of the electroglottographic closed quotient (EGG CQ) as a noninvasive estimate of vocal fold impact stress (SI). Two excised canine larynges were used. Each larynx was mounted and vocal fold oscillation was induced using a humidified air source. Twentyseven experimental trials were conducted for each larynx. Trials involved variations in vocal process gap, vocal fold elongation, and subglottic pressure. Simultaneous measures were made of vocal fold SI at the midpoint of the membranous vocal folds, and EGG CQ (dimensionless ratio). The results indicated that when threshold and saturation effects were excluded, the SI and the CQ were strongly related (linear correlation r = .83 and .96 for the two individual larynges, and .81 for the combined data). Within the region of linear relation, an increase of .15 in the CQ corresponded to about 1 kPa increase in SI for the combined data. Discussion focuses on possible clinical implications and the likely reasons for threshold and saturation phenomena.     

Determining the etiology of mild vocal fold hypomobility

The prevalence of mild vocal fold hypomobility is unknown. In a study by Heman-Ackah et al, vocal fold hypomobility in a population of singing teachers was found to be associated more frequently with vocal complaints than was the presence of vocal fold masses.¹ The etiology of mild vocal fold hypomobility has not been previously explored. In the present study, a retrospective chart review was performed of 134 patients who presented to a tertiary laryngology referral center over a 6-month period for evaluation of vocal complaints. Of the 134 patients, 61 (46%) were found to have mild vocal fold hypomobility previously undiagnosed by the referring otolaryngologist. Imaging studies and laboratory tests to evaluate for structural, metabolic, and infectious causes of the decreased mobility had been ordered. Forty-nine patients completed the work-up. Of these, 41 out of 49 (84%) were found to have imaging or laboratory findings that could explain the hypomobility. Thyroid abnormalities were found to be associated with vocal fold hypomobility in 21 out of 49 (43%) of those with a complete evaluation. Other causes of vocal fold hypomobility included idiopathic (8 of 49, 16%), viral neuritis (5 of 49, 10%), central nervous system abnormality (4 of 49, 8%), neural tumor (3 of 49, 6%), joint dysfunction (3 of 49, 6%), iatrogenic nerve injury (2 of 49, 4%), myopathy (2 of 49, 4%), and noniatrogenic traumatic nerve injury (1 of 49, 2%), This study shows that unilateral vocal fold hypomobility often is associated with a physiologic process, and a complete investigation to determine the etiology is warranted in all cases.     

The effects of preventive vocal hygiene education on the vocal hygiene habits and perceptual vocal characteristics of training singers

The purpose of the present study was to determine the effects of vocal hygiene education on the vocal hygiene behaviors and perceptual vocal characteristics of untrained singers. Eleven adult untrained singers served as subjects. They attended four 1-hour class sessions on vocal hygiene, including anatomy and physiology of the phonatory mechanism, vocally abusive behaviors, voice disorders commonly seen in singers, and measures to prevent voice disorders. Pre- and postinstruction surveys were used to record subjects' vocal abuses and their perceptions of their speaking and singing voice. They also rated their perceived value of vocal hygiene education. Results revealed minimal changes in vocal hygiene behaviors and perceptual voice characteristics. The subjects did report a high degree of benefit and learning, however.     

Laryngeal function and vocal fatigue after prolonged reading in individuals with unilateral vocal fold paralysis

The purpose of the present study was to examine the effect of prolonged loud reading, intended to induce fatigue, on vocal function in adults with unilateral vocal fold paralysis (UVFP). Subjects were 20 adults, 37–60 years old, with UVFP secondary to recurrent laryngeal nerve paralysis. Subjective ratings and instrumental measures of vocal function were obtained before and after reading. Statistical analysis revealed subjects rated their vocal quality and physical effort for voicing more severely following prolonged loud reading, whereas expert raters did not detect a significant perceptual difference in vocal quality. Reading fundamental frequency (Fo) was significantly increased following prolonged loud reading, as were mean airflow rates at all pitch conditions. Maximum phonation times for comfort and low pitches significantly decreased during posttests. Multiple regression analyses revealed significant associations between ratings of posttest physical effort and select posttest measures. Interpretation of results indicates the prolonged loud reading task was successful in vocally fatiguing most of the UVFP subjects. Key physiologic correlates of vocal fatigue, in individuals with UVFP, include further reduction of glottic efficiency, resulting in decreased regulation of glottic airflow and a temporary destabilization of speaking fundamental frequency.     

Collagen injection in the scarred vocal fold

Scar tissue in the vocal fold can impair vibration and voice quality. The association of scarring and glottic insufficiency prompted our use of injectable bovine collagen in a variety of pathologic conditions exhibiting vocal fold scarring. Incremental augmentation and improved glottic function in several treated patients seemed to be facilitated by softening of scar tissue. Although the use of bioimplants in the larynx is associated with immunologic risks, the proclivity to soften scar tissue is one potential benefit of such materials. The biological activity of injectable collagen seems to alter local collagen metabolism by promoting ingrowth of host fibroblasts that are active in collagen degradation and synthesis. Further research to study the mechanisms whereby injectable collagen promotes remodeling of connective tissue might have significant therapeutic implications in the management of laryngeal scarring.     

Endoscopic microsuture repair of vocal fold defects

The presence of a nonvibratory segment of vocal folds after microlaryngeal surgery is often a cause of poor voice result. The etiology of a nonvibratory segment is due to full thickness epithelial defect followed by secondary wound closure and scar contracture. To reduce scar contracture and nonvibratory segment of the vocal folds, primary repair with a 6-0 chromic endo-knot suture technique was used to close defects and approximate microflaps of the vocal folds. This was done in 18 patients with epithelial defects after resection of benign vocal fold lesions. The pathologic findings included severe polypoid degeneration (n = 7), fusiform laryngeal polyps (n = 5), sulcus vocalis (n = 2), cyst (n = 2), and keratosis (n = 2). Voice was improved in all patients after surgery. Comparison of vocal fold vibration before and after surgery showed improvements in configuration, amplitude, and mucosal wave. Vocal folds that were sutured all had good vibratory characteristics; none had a nonvibrating segment at the site of suture placement. Voice and healing after microsuture technique were near normal by Day 10 and return of mucosal wave was often complete by Day 14. Endoscopic microsuture closure of microflaps of the vocal folds edge is safe and affords the surgeon an opportunity for primary repair with improved functional result.     

Performance demands and the performer's vocal capabilities

Performers could benefit by knowing in advance and by objective means, what vocal requirements for a particular role or performance are potentially harmful to them. By combining the concept of the “phonetogram” (F₀ — SPL Profile) with automatic pitch extraction of vocal performances, a contour of the vocal performance demands can be superimposed on the profile of the individual's vocal capabilities. Vocal productions that are near to or exceeding the vocal capabilities of a performer can be presumed to be potentially hazardous. Likewise, performance demands that are clearly within the profile of a given individual can be presumed to be nonhazardous with respect to pitch and amplitude range.     

The effects of excessive vocalization on acoustic and videostroboscopic measures of vocal fold condition

Although dysphonia is a recognized consequence of acute vocal abuse, associated changes in vocal fold appearance and function are not well understood. To document these presumed effects of vocal abuse, audio recordings of sustained vowel production were obtained from 42 drill sergeants daily during the first 6 days of a vocally demanding training exercise. Acoustic analysis showed abnormal levels of jitter and shimmer on Day 1 in 16 of the 42 subjects. Considering only the 26 subjects who showed normal voice acoustics on Day 1, the median levels of jitter and shimmer varied little over the course of training, and significant increases in jitter and shimmer were not seen during the study period. However, the distributions for both jitter and shimmer became more positively skewed and showed a greater number of positive outliers over the course of training. This trend was attributed to 11 subjects who showed two or more instances of abnormal voice acoustics over Days 2 through 6. Laryngeal videostroboscopic recordings of sustained vowel production also were obtained prior to and following training. Perceptual ratings of these recordings by 2 observers revealed significant increases in vocal fold edema, erythema, and edge irregularity, and decreases in vocal fold mucosal wave and amplitude of excursion following the 5-day training period. In general, there was considerable intersubject variability in the extent of acoustic and videostroboscopic effects over the course of training. Of the two types of data, videostroboscopy appears to provide a more sensitive indication of the effects of excessive vocalization.     

Laser Doppler Measurements of the Vocal Fold Blood Micro-Circulation

The authors have developed a laser Doppler method, referred to as LDF+LS (laser Doppler flowmetry by laryngostereometry), for measuring the vocal fold micro-circulation. The vocal folds of 103 patients were examined during general anesthesia. A laser Doppler probe was placed on defined positions at the vocal fold edge: midmembranous position (MP), 2 mm and 4 mm behind, and 1 mm anterior to MP. Three parameters were derived, ie, the concentration (CMBC) and velocity (V) of moving blood cells, and the product of both resulting in perfusion: P = CMBCxV. The results of 53 subjects with normal vocal fold status showed that the V at MP was significantly lower than 2 mm behind MP (P < 0.05). Men had significantly higher velocity than women (P < 0.05). Subjects older than 65 years had higher perfusion and CMBC as compared with younger subjects (P < 0.01). Smokers with normal vocal folds had higher velocity than non-smokers (P < 0.05). Measurements of healthy vocal folds were compared with benign vocal fold pathology. Vocal fold polyps had significantly higher perfusion than normal vocal folds (P < 0.01). In conclusion, the laser Doppler measurement is a sensitive tool estimating superficial blood flow in both normal and pathological vocal folds. The blood flow in normals differs with respect to gender and age probably due to variations in micro-circulation of the mucosa and lamina propria. Vocal fold pathology and external factors such as smoking result in blood flow changes.     

The effect of viscosity changes in the vocal folds on the range of oscillation

Changes in vocal fold oscillation threshold pressure were induced in excised canine larynges by experimentally causing fluid movement into and out of the vocal folds. The transport was facilitated by exposing the vocal folds to various osmotic solutions, and it was assumed that changes in hydration caused changes in the internal tissue viscosity. A range of oscillation threshold pressures was measured for each condition of hydration by varying length and glottal width. The oscillation threshold pressure shifted as predicted. Decreased hydration (increased viscosity) raised the threshold of oscillation, and increased hydration (decreased viscosity) lowered the threshold of oscillation. This apparently represents the first in vitro model for the study of the effect of viscosity changes of the internal environment of the vocal folds on phonation.