Tracheo-bronchial soft tissue and cartilage resonances in the subglottal acoustic input impedance

Abstract

This paper offers a re-evaluation of the mechanical properties of the tracheo-bronchial soft tissues and cartilage and uses a model to examine their effects on the subglottal acoustic input impedance. It is shown that the values for soft tissue elastance and cartilage viscosity typically used in models of subglottal acoustics during phonation are not accurate, and corrected values are proposed. The calculated subglottal acoustic input impedance using these corrected values reveals clusters of weak resonances due to soft tissues (SgT) and cartilage (SgC) lining the walls of the trachea and large bronchi, which can be observed empirically in subglottal acoustic spectra. The model predicts that individuals may exhibit SgT and SgC resonances to variable degrees, depending on a number of factors including tissue mechanical properties and the dimensions of the trachea and large bronchi. Potential implications for voice production and large pulmonary airway tissue diseases are also discussed.

Subglottal resonances of American English speaking children

“…where N 2 {1,2,3}, c N is the propagation velocity of the wave for the Nth SGR, h is the height of the speaker, and k a is a scaling factor relating the acoustic length of the subglottal system (l a ) to speaker height (l a ¼ h/k a ). It was noted that in adults, while the wave propagation velocity for Sg2 and Sg3 was approximately the speed of sound at body temperature, c 0 ¼ 35 900 cm/s, the wave propagation velocity for Sg1 was larger than c 0 due to the inertive properties of the subglottal system tissue walls in the Sg1 frequency range (Lulich et al, 2011a;Lulich and Arsikere, 2015). The value of c 1 was denoted as c w for the "walls" of the subglottal system.…”

Mechanical, Cellular, and Proteomic Properties of Laryngotracheal Cartilage

“…44 Variations in the tensile moduli and the coefficient of viscosity between tracheal cartilages have been found to impact subglottal acoustic input impedance, which can be observed empirically in subglottal acoustic spectra. 15 Therefore, tissue engineered laryngotracheal cartilage should be similar to native tracheal cartilage in these features.…”

“…4,[9][10][11][12][13][14] Furthermore, many of the properties of cartilage are determined by their cellular composition and density, and the proteomic/glycomic composition of the extracellular matrix (ECM). 15,16 In this review, the literature of the mechanical, cellular, and proteomic properties of the laryngotracheal cartilages will be examined in order to provide a baseline of knowledge and illustrate gaps in the literature. As outlined, regenerative medicine of the airway has been trachea focused, and the mechanical and protein compositions of tracheal cartilage have been investigated.…”

Simulation of bronchial airway acoustics in healthy and asthmatic subjects

“…The inverted trend at the level of the trachea can be possibly explained by considering that in the range between 380 and 560 Hz [11,29,30] resonance phenomena associated with the soft tissue component of trachea and main bronchi can occur, possibly affecting the results. The location of the resonance peak is dependent both on thickness and radius variations [12] and subject to a certain inter-variability. The increase in wall thickness and the reduction in diameter determined by the asthma pathology might have shifted the soft tissue resonance to lower frequencies thus explaining the observed inversion.…”

“…Dai et al [8] and Yeng et al [9,10]studied both numerically and experimentally the sound transmission in the lungs. Lulich et al [11,12] focused on the analysis of resonance phenomena and wave propagation velocities in the lower respiratory tract. Henry et al [13] further extended the approach in [8,14] to account for image-based geometries in healthy subjects and proposed a simplified approach to specific pathological conditions.…”