Biomedical subjects

I R Titze

Publications and source records attributed to I R Titze.

At least 37 records · Page 2Linked to original sources

PubMed2000

Biomechanical and histologic observations of vocal fold fibrous proteins.

This article discusses the molecular composition of the vocal fold and the relationship of fibrous molecules to the biomechanical and physiological performance of the tissue. The components of the extracellular matrix may be divided into fibrous proteins and interstitial proteins. The fibrous proteins, consisting of collagens and elastins, are the focus of this report. Elastin concentration varies by tissue depth in the vocal folds. Variation of elastin by age is reported, but some controversy exists. The biomechanical terms of stress and strain (and stress-strain curves of human vocal folds) are related to the fibrous proteins of the vocal folds. The fibrous proteins, their role in stress, and their effect on the dynamic range of vocal pitch are presented.

Aging↗

PubMed2000

Three-dimensional anatomic characterization of the canine laryngeal abductor and adductor musculature.

The biomechanics of vocal fold abduction and adduction during phonation, respiration, and airway protection are not completely understood. Specifically, the rotational and translational forces on the arytenoid cartilages that result from intrinsic laryngeal muscle contraction have not been fully described. Anatomic data on the lines of action and moment arms for the intrinsic laryngeal muscles are also lacking. This study was conducted to quantify the 3-dimensional orientations and the relative cross-sectional areas of the intrinsic abductor and adductor musculature of the canine larynx. Eight canine larynges were used to evaluate the 3 muscles primarily responsible for vocal fold abduction and adduction: the posterior cricoarytenoid, the lateral cricoarytenoid, and the interarytenoid muscles. Each muscle was exposed and divided into discrete fiber bundles whose coordinate positions were digitized in 3-dimensional space. The mass, length, relative cross-sectional area, and angle of orientation for each muscle bundle were obtained to allow for the calculations of average lines of action and moment arms for each muscle. This mapping of the canine laryngeal abductor and adductor musculature provides important anatomic data for use in laryngeal biomechanical modeling. These data may also be useful in surgical procedures such as arytenoid adduction.

Animals↗

PubMed1999

Time-of-day effects on voice range profile performance in young, vocally untrained adult females.

Time-of-day effects on voice range profile performance were investigated in 20 vocally healthy untrained women between the ages of 18 and 35 years. Each subject produced two complete voice range profiles: one in the morning and one in the evening, about 36 hours apart. The order of morning and evening trials was counterbalanced across subjects. Dependent variables were (1) average minimum and average maximum intensity, (2) Voice range profile area and (3) center of gravity (median semitone pitch and median intensity). In this study, the results failed to reveal any clear evidence of time-of-day effects on voice range profile performance, for any of the dependent variables. However, a reliable interaction of time-of-day and trial order was obtained for average minimum intensity. Investigation of other subject populations, in particular trained vocalists or those with laryngeal lesions, is required for any generalization of the results.

Adolescent↗

PubMed1999

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.

Adult↗

PubMed1999

Vocal fold proteoglycans and their influence on biomechanics.

OBJECTIVE/HYPOTHESIS: To examine the interstitial proteins of the vocal fold and their influence on the biomechanical properties of that tissue. STUDY DESIGN: Anatomic study of the lamina propria of human cadaveric vocal folds combined with some viscosity testing. METHODS: Identification of proteoglycans is performed with histochemical staining. Quantitative analysis is performed using an image analysis system. A rheometer is used for viscosity testing. Three-dimensional rendering program is used for the computer images. RESULTS: Proteoglycans play an important role in tissue biomechanics. Hyaluronic acid is a key molecule that affects viscosity. DISCUSSION: The proteoglycans of the lamina propria have important biological and biomechanical effects. The role of hyaluronic acid in determining tissue viscosity is emphasized. Viscosity, its effect on phonatory threshold pressure and energy expended due to phonation is discussed. CONCLUSION: Proteoglycans, particularly hyaluronic acid, play important roles in determining biomechanical properties of tissue oscillation. Future research will likely make these proteins of important therapeutic interest.

Adult↗

PubMed1999

Hyaluronic acid (with fibronectin) as a bioimplant for the vocal fold mucosa.

OBJECTIVES: To measure the viscoelastic shear properties of hyaluronic acid, with and without fibronectin, and to compare them with those of the human vocal fold mucosa and other phonosurgical biomaterials. METHODS: Viscoelastic shear properties of various implantable biomaterials (Teflon, gelatin, collagen, fat, hyaluronic acid, and hyaluronic acid with fibronectin) were measured with a parallel-plate rotational rheometer. Elastic and viscous shear properties were quantified as a function of oscillation frequency (0.01-15 Hz) at 37 degrees C. RESULTS: The shear properties of hyaluronic acid were relatively close to those of human vocal fold mucosal tissues reported previously. Hyaluronic acid at specific concentrations (0.5%-1%), with or without fibronectin, was found to exhibit viscous shear properties (viscous shear modulus and dynamic viscosity) similar to those of the average male and female vocal fold mucosa. CONCLUSIONS: According to a theory that establishes the effects of tissue shear properties on vocal fold oscillation, phonation threshold pressure (a measure of the ease of phonation) is directly related to the viscous shear modulus of the vibrating vocal fold mucosa. Therefore, our findings suggest that hyaluronic acid, either by itself or mixed with fibronectin, may be a potentially optimal bioimplant for the surgical management of vocal fold mucosal defects and lamina propria deficiencies (e.g., scarring) from a biomechanical standpoint.

Biocompatible Materials↗

PubMed1999

Messa di voce: an investigation of the symmetry of crescendo and decrescendo in a singing exercise.

A classical vocal exercise called "messa di voce" (Italian for "placing the voice") was used to study the symmetry of intensity increase and decrease in six trained singers. Ideally, the exercise is performed as a symmetric triangle, a linear increase in loudness, followed by a linear decrease. Given that some physiologic variables, like lung volume, undergo unidirectional change rather than a symmetric reversal, there is reason to believe that symmetries may not exist. It was found that highly trained singers who use large SPL ranges tend to abbreviate the decrescendo phase in comparison with the crescendo phase. In a few other cases, a plateau in SPL is reached, but an increase in loudness may still be perceived on the basis of a stronger vibrato or changes in timbre.

Adult↗

PubMed1999

Viscoelastic shear properties of human vocal fold mucosa: measurement methodology and empirical results.

A standard method for the empirical rheological characterization of viscoelastic materials was adopted to measure the viscoelastic shear properties of human vocal-fold mucosal tissues (the superficial layer of lamina propria). A parallel-plate rotational rheometer was employed to measure shear deformation of viscoelastic tissue samples, which were deformed between two rigid circular plates rotating in small-amplitude sinusoidal oscillations. Elastic and viscous shear moduli of the samples were then quantified as a function of oscillation frequency (0.01 to 15 Hz) based on shear stresses and strains recorded by the rheometer. Data were obtained from 15 excised human larynges (10 male and 5 female). Results showed that the elastic shear modulus mu and the damping ratio zeta of human vocal-fold mucosa were relatively constant across the range of frequencies observed, while the dynamic viscosity eta decreased monotonically with frequency (i.e., shear thinning). Intersubject differences in mu and eta as large as an order of magnitude were observed, part of which may reflect age-related and gender-related differences. Some molecular interpretations of the findings are discussed.

Adult↗

PubMed1999

Experimental approaches to vocal fold alteration: introduction to the minithyrotomy.

Treatment of challenging laryngeal disorders, such as lamina propria loss or neuromuscular dysfunction, may require novel approaches and techniques. This paper discusses an evolution of experimental techniques for treatment of lamina propria loss and use of the minithyrotomy. These techniques have been used for surgical access for lamina propria substitution, as well as placement of stimulating electrodes. The minithyrotomy is tolerated well by patients, provides access for microscopic instruments with the surgeon's hand close to the tissue of interest, avoids intralaryngeal mucosal incisions, and lines up the direction of dissection in an anterior-to-posterior orientation. This orientation is favorable for particular situations herein discussed. We present anatomic and physiologic concepts relevant to the surgical treatment of lamina propria dysfunction, as well as presenting our clinical experience. This paper is not intended to state how these difficult problems should be handled, but rather, to present our experience in techniques that may prove useful through further development.

Adipose Tissue↗

PubMed1999

Geometric structure of the human and canine cricothyroid and thyroarytenoid muscles for biomechanical applications.

The geometric structure of the cricothyroid (CT) muscle and thyroarytenoid (TA) muscle was quantified in 6 human and 3 canine larynges. Each muscle was divided into a series of fiber bundles. With a 3-dimensional micrometer probe, the coordinates of the origin and insertion of each bundle were measured before dissection. It was found that the mass of the CT muscle in the dog was 1.463+/-0.280 g, which was significantly greater than the 0.9423+/-0.123 g found in the human. This was a result of the cross-sectional area of the canine CT muscle being 105.3+/-11.6 mm2 instead of the 73.8+/-7.4 mm2 found for the human. However, the ratios of CT/TA mass and cross-sectional area between the two groups were not significantly different, suggesting that the two muscles grow proportionally.

Adult↗

PubMed1998

Suitability of minidisc (MD) recordings for voice perturbation analysis.

A new digital recording format, Minidisc (MD), shows promise for high-quality voice recordings. It is available in a portable size and uses magneto-optical recording techniques on a miniature compact disc. The disc can be recorded an unlimited number of times with essentially the same playback life span: however, the digital recording technique uses a data compression algorithm that may interfere with acoustic voice perturbation analysis. This study investigated what effects this compression may have and whether the MD format is viable for use in this application. The MD format was evaluated by traditional synthetic test signals used on recording devices. In addition, human phonation recorded on Digital Audio Tape (DAT) was used as the input to the MD. The output of the MD was then compared to the original DAT recording. The two signals were analyzed for long- and short-term perturbation measures, and their waveforms were visually inspected. The results indicated that the MD format performed as well as the DAT format in all areas of standard tests, with the exception of signal-to-noise (S/N) ratio. S/N ratio for the MD was approximately 10 dB less than for the DAT under normal operating conditions; however, in comparing perturbation measures on normal human vowels, there were no significant differences between the two formats, i.e., no distortions in voice perturbation were introduced by the MD record/playback process.

Female↗

PubMed1998

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. Twenty-seven 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.

Animals↗

PubMed1998

Viscosities of implantable biomaterials in vocal fold augmentation surgery.

Vocal fold vibration depends critically on the viscoelasticity of vocal fold tissues. For instance, phonation threshold pressure, a measure of the "ease" of phonation, has been shown to be directly related to the viscosity of the vibrating mucosa. Various implantable biomaterials have been used in vocal fold augmentation surgery, with implantation sites sometimes close to or inside the mucosa. Yet their viscosities or other mechanical properties are seldom known. This study attempts to provide data on viscosities of commonly used phonosurgical biomaterials. Using a parallel-plate rotational rheometer, oscillatory shear experiments were performed on implantable polytetrafluoroethylene (Teflon or Polytef; Mentor Inc., Hingham, MA), collagen (Zyderm; Collagen Corp., Palo Alto, CA), glutaraldehyde crosslinked (GAX) collagen (Phonagel or Zyplast; Collagen Corp.), absorbable gelatin (Gelfoam; Upjohn Co., Kalamazoo, MI), and human abdominal subcutaneous fat. Samples of human vocal fold mucosal tissues were also tested. Under sinusoidal oscillatory shear at 10 Hz and at 37 degrees C, the dynamic viscosity was 116 Pascal-seconds (Pa-s) for polytetrafluoroethylene, 21 Pa-s for gelatin, 8-13 Pa-s for the two types of collagen, 3 Pa-s for fat, and 1 to 3 Pa-s for vocal fold mucosa. Results extrapolated to 100 Hz also show similar differences among the biomaterials, but all values are an order of magnitude lower because of the typical inverse frequency relation (shear thinning effect) for polymeric and biologic materials. The data suggest that the use of fat for vocal fold augmentation may be more conducive to the "ease" of phonation because of its relatively low viscosity, which is closest to physiologic levels. This implication is probably the most relevant in predicting initial outcome of the postoperative voice before there is any significant assimilation (e.g., resorption and fibrosis) of the implanted biomaterial.

Abdomen↗

PubMed1998

Vocal tract area functions for an adult female speaker based on volumetric imaging.

Magnetic resonance imaging (MRI) was used to acquire vocal tract shapes of ten vowels /i, I, [symbol: see text] a, [symbol: see text], o, [symbol: see text] u/ and two liquid approximants /3[symbol: see text], 1/ for a 27-year-old adult female. These images were complemented with additional images acquired with electron beam computed tomography (CT) of /i/ and /a/. Each 3-D shape was condensed into a set of cross-sectional areas of oblique sections perpendicular to the centerline of the vocal tract's long axis, resulting in an "area function." Formant frequencies computed for each area function showed reasonable similarity to those determined from the natural (recorded) speech of the imaged subject, but differences suggest that some of the imaged vocal tract shapes were articulated differently during imaging than during recording of natural speech, and also that imaging procedures may have compromised some accuracy for a few shapes. The formant calculations also confirmed the significant effect that the piriform sinus can have on lowering the formant frequencies. A comparison is made between area functions derived using both MRI and CT methods for the vowels /i/ and /a/. Additionally, the area functions reported in this study are compared with those from two previous studies and demonstrate general similarities in shape but also obvious differences that can be attributed to anatomical differences of the imaged subjects and to differences in imaging techniques and image processing methods.

Adult↗

PubMed1997

Populations in the U.S. workforce who rely on voice as a primary tool of trade: a preliminary report.

The United States Bureau of Labor Statistics and other sources were consulted about the percentages of the working population that we identified as professional voice users. The largest percentage may be in sales and sales-related occupations (13%), but the exact breakdown of those who approach their clients vocally rather than by mail is still uncertain. The second largest population is teachers, who comprise 4.2% percent of the U.S. workforce (1994 statistic). Teachers have been identified as having the greatest incidence of voice disorders. Population data are also given for professional voice users who could present a significant hazard to public safety if their vocal communication skills were severely impaired.

Employment↗

PubMed1997

The dynamics of length change in canine vocal folds.

The time courses of vocal fold elongation and contraction have been measured as a function of intrinsic laryngeal muscle activity. The superior and recurrent laryngeal nerves of anesthetized canines were stimulated supramaximally (on-off in all combinations) while the vocal folds were surgically exposed and illuminated for conventional and higher speed (300 frames per second) video recording. Microsutures were placed on various points on the vocal folds to measure elongation and contraction. Vocal fold strain, defined as elongation divided by rest length, ranged from -17% to +45%. The typical time constant for exponential increase or decrease in strain was about 30 ms. This reflects primarily the intrinsic muscle activation times rather than a passive (inertial or viscoelastic) response of cricothyroid joint rotation or translation.

Adult↗

PubMed1997

The effect of subglottal resonance upon vocal fold vibration.

An experiment with excised larynges was undertaken to investigate the interaction 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.

Acoustics↗

PubMed1997

Conversion of a head-mounted microphone signal into calibrated SPL units.

A method is reviewed for conversion of a microphone signal into calibrated Sound Pressure Level (SPL) units. The method follows American National Standards Institute (ANSI) standard for S1.4 SPL meters and requires an accurate SPL meter and an accurate calibration sound source for conversion. Accuracy and validation data from test signals and human phonation are provided. The results indicate that under typical speech conditions, an absolute accuracy of plus or minus 1.6 dB (type 1 SPL meter) can be obtained with a miniature head-mounted microphone.

Amplifiers, Electronic↗