Biomechanical Flow Amplification Arising From the Variable Deformation of the Subglottic Mucosa.

Objective: This study mapped the variation in tissue elasticity of the subglottic mucosa, applied these data to provide initial models of the likely deformation of the mucosa during the myoelastic cycle, and hypothesized as to the impact on the process of phonation.

Study Design: Six donor human larynges were dissected along the sagittal plane to expose the vocal folds and subglottic mucosa. A linear skin rheometer was used to apply a controlled shear force, and the resultant displacement was measured.

Quantification of change in vocal fold tissue stiffness relative to depth of artificial damage.

Objectives: To quantify changes in the biomechanical properties of human excised vocal folds with defined artificial damage.

Methods: The linear skin rheometer (LSR) was used to obtain a series of rheological measurements of shear modulus from the surface of 30 human cadaver vocal folds. The tissue samples were initially measured in a native condition and then following varying intensities of thermal damage.

The anisotropic nature of the human vocal fold: an ex vivo study.

The purpose of this study was to measure the relationship between the shear elastic properties of vocal fold with respect to the direction of applied stress. There is extensive published material that quantifies the shear viscoelastic properties of the vocal fold, but as much of these data were obtained using rotating parallel plate rheometers, which are unable to resolve out difference of the shear elastic behaviour with respect to direction, there is very little data that indicates anisotropic behaviour. To overcome this gap in knowledge, the team devised an apparatus that is capable of applying a shear stress in a known direction.

Gradation of stiffness of the mucosa inferior to the vocal fold.

During phonation, energy is transferred from the subglottal airflow through the air/mucosa interface that results in the propagation of the mucosal wave in the vocal fold. The vocal fold is soft, and the subglottal mucosa is stiff. We hypothesize that it is highly improbable that there is a rigid boundary between the tissue structures, with a sudden drop in stiffness; and that a gradual change would be more likely to support the efficient transfer of energy from the airflow to the mucosal wave.

Control of vocal fold cover stiffness by laryngeal muscles: a preliminary study.

Objectives: To perform preliminary measurements of the shear modulus of the vocal fold cover layer during intrinsic laryngeal muscle contraction.

Study Design: Shear modulus was measured in an in vivo canine larynx and an ex vivo human larynx.

Methods: Shear stress was applied to the transverse axis of the vocal fold using a modified linear skin rheometer (LSR) via an attached suction probe.

The shear modulus of the human vocal fold in a transverse direction.

The aim of this study was to measure the shear modulus of the vocal fold in a human hemilarynx, such that the data can be related to direction of applied stress and anatomical context. Dynamic spring rate data were collected using a modified linear skin rheometer using human hemilarynges, and converted to estimated shear modulus via application of a simple shear model. The measurement probe was attached to the epithelial layer of the vocal fold cover using suction.

Viscoelastic measurements of vocal folds using the linear skin rheometer.

As the number of interventions for vocal fold scar grows and with the advancement of mathematical modeling, greater accuracy and precision in the measurement of vocal fold pliability will become essential. Although indirect pliability measures have been used successfully, direct measurement of tissue pliability is essential. Indirect measurement with parallel plate technology has limitations; it requires the tissue to be removed from the surrounding framework, allows no site specificity, and offers no future for in vivo use in animals or humans.

In vivo measurement of the shear modulus of the human vocal fold: interim results from eight patients.

The shear modulus of the vocal fold is an essential parameter required to enhance our understanding of how the vocal fold operates, to develop mathematical models of phonatation, and to provide benchmarks to quantify the effectiveness of surgical procedures. The authors announced the successful deployment of an instrument to measure vocal fold elasticity in vivo last year, and now present the data taken from eight patients in vivo. The shear modulus was measured at the mid-membranous point, in a transverse direction with respect to the axis drawn between the anterior commissure and vocal process.

The shear modulus of the human vocal fold, preliminary results from 20 larynxes.

Quantification of the elastic properties of the human vocal fold provides invaluable data for researchers deriving mathematical models of phonation, developing tissue engineering therapies, and as normative data for comparison between healthy and scarred tissue. This study measured the shear modulus of excised cadaver vocal folds from 20 subjects. Twenty freshly excised human larynxes were evaluated less than four days post-mortem.

Measurements of vocal fold elasticity using the linear skin rheometer.

Objective: The linear skin rheometer (LSR), which measures skin visco-elasticity, was adapted for measurements of vocal fold properties. A series of studies was performed on animal and human excised larynges to determine if the LSR technique can be applied to the vocal fold.

Methods: In excised larynges, small patches of mucosa were driven sinusoidally at 0.

In vivo measurement of the elastic properties of the human vocal fold.

The ability to measure the biomechanical properties of the vocal fold in vivo is both an aid to diagnosis and enhances our knowledge of how the vocal folds operate. This paper details a new instrument that is capable of taking readings of the spring rate of the vocal fold in a repeatable manner. We also present three sets of readings taken from two volunteer patients.