A Biomechanical Model of the Upper Airways for Simulating Laryngoscopy

This paper describes a three-dimensional finite element model of the human upper airways during rigid laryngoscopy. In this procedure, an anaesthetist uses a rigid blade to displace and compress the tongue of the patient, and then inserts a tube into the larynx to allow controlled ventilation of the lungs during an operation. A realistic model of the main biomechanical aspects involved would help anaesthetists in training and in predicting difficult cases in advance. For this purpose, the finite element method was used to model structures such as the tongue, ligaments, larynx, vocal cords, bony landmarks, laryngoscope blade, and their inter-relationships, based on data extracted from X-ray, MRI, and photographic records. The model has been used to investigate how the tongue tissue behaves in response to the insertion of the laryngoscope blade, when it is subjected to a variety of loading conditions. In particular, the mechanical behaviour of the soft tissue of the tongue was simulated, from simple linear elastic material to complex non-linear viscoelastic material. The results show that, within a specific set of tongue material parameters, the simulated outcome can be successfully related to the view of the vocal cords achieved during real laryngoscopies on normal subjects, and on artificially induced difficult laryngoscopy, created by extending the upper incisors teeth experimentally.     

An alternative method of endotracheal intubation of common marmosets (Callithrix jacchus)

Endotracheal intubation was carried out in 11 common marmosets (Callithrix jacchus). A commercially available tilting stand and a Miller laryngoscope blade were used to visualize the larynx. Anaesthesia was induced with alphaxalone (10.6 ± 1.6 mg/kg intramuscularly, followed by 3.2 ± 1.2 mg/kg intravenously). The diameter of the proximal trachea easily fitted an endotracheal tube made from readily available material (a 12 G 'over the needle' catheter). Once the tip of the endotracheal tube was at the level of the vocal folds, the tube had to be gently rotated through a 180° angle in order to pass through the larynx into the trachea. Assessment of the dimensions of the larynx and trachea, and comparison with external anatomical features of the animals (n = 10) showed that the length of the trachea could be predicted by multiplying the craniosacral length of the marmoset by a factor of 0.42.     

Structure of the larynx of the tokay gecko (Gekko gecko), with particular reference to the vocal cords and glottal lips

The ability to vocalize is well-known in gekkonid lizards but relatively little attention has been paid to the structure of the vocal apparatus. In this study we briefly review the structure of the larynx and associated musculature of the tokay gecko as a baseline for a comparative survey of the family. The cricoid and arytenoid cartilages form the skeleton of the larynx and are controlled by constrictor and dilator muscles. The gross morphology of the vocal cords and glottal lips is then described, the structure being elucidated by way of dissection, histology, and scanning electron microscopy. The vocal cords run between the arytenoid and cricoid cartilages, are highly elastic, and bear a highly folded mucosa. The lips of the glottis have a structure reminiscent of erectile tissue. The respiratory mucosa of the larynx varies according to position and may be related to the tonal aspects of sound production. The structure of the larynx is compared with that of other vertebrates, and the relationship between morphology and phonation is considered.     

Alterations in the release calls of six European anura (amphibia) after partial or total extirpation of the vocal cords

In the interior of the larynx of Ranidae there are two sturdy vocal cords. The Bufonidae have more delicate vocal cords, and in addition paired cushions of tissue anterior to the cords and paired folds posterior to the cords.In the three ranids Rana esculenta, Rana ridibunda and Rana temporaria, partial or total extirpation of the vocal cords results in loss of voice or atypical release calls. In such remnants of calls as are retained, the frequency composition is little affected, whereas the intensity is always greatly reduced. The most severe impairment is evident in the formation of sound pulses and in the rhythmicity of the pulse sequence.In the three bufonids Bufo bufo, Bufo calamita and Bufo viridis loss of voice is a less common result of the various operations than in the ranids. The most marked deterioration follows removal of all or part of the vocal cords. The tissue cushions and the posterior folds participate, along with the vocal cords, in production of the release calls. Post-operative alterations in the release calls are therefore quite variable.     

Finite element modeling of the left atrium to facilitate the design of an endoscopic atrial retractor

With the worldwide prevalence of cardiovascular diseases, much attention has been focused on simulating the characteristics of the human heart to better understand and treat cardiac disorders. The purpose of this study is to build a finite element model of the left atrium (LA) that incorporates detailed anatomical features and realistic material characteristics to investigate the interaction of heart tissue and surgical instruments. This model is used to facilitate the design of an endoscopically deployable atrial retractor for use in minimally invasive, robotically assisted mitral valve repair. Magnetic resonance imaging (MRI) scans of a pressurized explanted porcine heart were taken to provide a 3D solid model of the heart geometry, while uniaxial tensile tests of porcine left atrial tissue were conducted to obtain realistic material properties for noncontractile cardiac tissue. A finite element model of the LA was constructed using ANSYS Release 9.0 software and the MRI data. The Mooney-Rivlin hyperelastic material model was chosen to characterize the passive left atrial tissue; material constants were derived from tensile test data. Finite element analysis (FEA) models of a CardioVations Port Access retractor and a prototype endoscopic retractor were constructed to simulate interaction between each instrument and the LA. These contact simulations were used to compare the quality of retraction between the two instruments and to optimize the design of the prototype retractor. Model accuracy was verified by comparing simulated cardiac wall deflections to those measured by MRI. FEA simulations revealed that peak forces of approximately 2.85 N and 2.46 N were required to retract the LA using the Port Access and prototype retractors, respectively. These forces varied nonlinearly with retractor blade displacement. Dilation of the atrial walls and rigid body motion of the chamber were approximately the same for both retractors. Finite element analysis is shown to be an effective tool for analyzing instrument/tissue interactions and for designing surgical instruments. The benefits of this approach to medical device design are significant when compared to the alternatives: constructing prototypes and evaluating them via animal or clinical trials.     

白暨豚上呼吸道的解剖和组织学的研究

白鱀豚上呼吸道具有前庭囊、鼻额囊及前颌囊三对气囊,没有副囊和连接囊。三对囊均右大于左,其中又以前庭囊最为显著。喉由甲状软骨、环状软骨、会厌软骨及一对杓状软骨组成,从喉腔壁的组织学观察发现有室皱襞(假声带)的存在。       

Tracheal length changes during zebra finch song and their possible role in upper vocal tract filtering

Sounds produced in the avian vocal organ may be modified by filter properties of the upper vocal tract. Possible mechanisms to actively control filter characteristics include movements of the beak, tongue, and larynx and adjustments of tracheal length. We investigated whether length changes of the trachea are a likely mechanism for adjusting upper vocal tract filter properties during song in the zebra finch (Taeniopygia guttata). Tracheal length was monitored at the basal end using sonomicrometry and was recorded together with subsyringeal air sac pressure and acoustic output. Tracheal shortening occurred at the onset of song bouts, and during each motif the tracheal length decreased during expiratory pressure pulses and increased during the short inspirations. A bilateral tracheal syringeal nerve cut confirmed that the initial shortening at the onset of the song bout is an active shortening of the trachea (i.e., mediated by syringeal muscle activity). The modulation of length during the motif was not affected by the denervation and is most likely driven by the pressurization of the interclavicular air sac. The absolute length change during the motif was small (<0.2 mm) and not clearly related to acoustic features of the song. For example, some high-frequency syllables, which are generated during inspiration, were accompanied by tracheal elongation. Because this elongation shifts tube resonances to lower frequencies, it is inconsistent with an active adjustment of length to enhance high frequency sounds. The small magnitude and inconsistent nature of dynamic tracheal length changes during song make it unlikely that they significantly affect vocal tract filter properties if the trachea is modeled as a rigid tube.     

Modeling mechanical stresses as a factor in the etiology of benign vocal fold lesions

Vocal fold tissue lesions such as nodules and polyps are thought to develop in response to mechanical stress that occurs during vocal fold collision. Two computational models of vocal fold collision during voice production are used to investigate this hypothesis. A one-dimensional lumped mass model, whose parameters are derived from vocal fold tissue dimensions and material properties, predicts stress perpendicular to the direction of impact (normal stress). A previously published three-dimensional finite element model that incorporates the same dimensions and properties predicts the entire stress tensor. The hypothesis is supported by predictions from the finite element model that three components of normal stress and one component of shear stress are increased during collision in the typical location of lesions (i.e. the center of the superior medial edge of the vocal fold in the middle of the vibrating and contact region). The lumped mass model predicts that mechanical stress is negatively correlated with mucosal thickness (increased by voice warm-up and hydration), is positively correlated with driving force (proportional to voice intensity), and is affected by voice production method. These relationships are consistent with clinical observations of vocal fold lesion risk factors and have implications for improving prevention and treatment of benign vocal fold lesions.     

A Cervid Vocal Fold Model Suggests Greater Glottal Efficiency in Calling at High Frequencies

Male Rocky Mountain elk (Cervus elaphus nelsoni) produce loud and high fundamental frequency bugles during the mating season, in contrast to the male European Red Deer (Cervus elaphus scoticus) who produces loud and low fundamental frequency roaring calls. A critical step in understanding vocal communication is to relate sound complexity to anatomy and physiology in a causal manner. Experimentation at the sound source, often difficult in vivo in mammals, is simulated here by a finite element model of the larynx and a wave propagation model of the vocal tract, both based on the morphology and biomechanics of the elk. The model can produce a wide range of fundamental frequencies. Low fundamental frequencies require low vocal fold strain, but large lung pressure and large glottal flow if sound intensity level is to exceed 70 dB at 10 m distance. A high-frequency bugle requires both large muscular effort (to strain the vocal ligament) and high lung pressure (to overcome phonation threshold pressure), but at least 10 dB more intensity level can be achieved. Glottal efficiency, the ration of radiated sound power to aerodynamic power at the glottis, is higher in elk, suggesting an advantage of high-pitched signaling. This advantage is based on two aspects; first, the lower airflow required for aerodynamic power and, second, an acoustic radiation advantage at higher frequencies. Both signal types are used by the respective males during the mating season and probably serve as honest signals. The two signal types relate differently to physical qualities of the sender. The low-frequency sound (Red Deer call) relates to overall body size via a strong relationship between acoustic parameters and the size of vocal organs and body size. The high-frequency bugle may signal muscular strength and endurance, via a ‘vocalizing at the edge’ mechanism, for which efficiency is critical.     

声带曲菌病6例报告

目的探讨声带曲菌病的实验诊断和治疗方法。方法分析我院门诊2007年3月～2008年9月间6例声带曲菌病患者的临床资料,总结经验教训。结果本文6例门诊患者声带活检,标本分别作真菌检验和病理检验。真菌直接镜检阳性1例,培养有4例烟曲菌生长和2例黄曲菌生长;病理检验均显示声带坏死组织中大量中性粒细胞、浆细胞及淋巴细胞浸润,4例可见大量菌丝,呈45。分支透明有隔菌丝。嘱患者禁声3d,停用抗生素。予伊曲康唑胶囊0．2g,口服2次／d,14d后减量为0．1g,口服1次／d,7d后停药。患者服药3～4d后能够发声,10d后声音嘶哑症状消失。1—3个月后复查电子喉镜均显示：假膜消失,声带光滑,闭合正常。随访1个月-1年半,6例声音完全恢复正常,声带光滑,声带无充血现象,无复发。结论治疗声带曲菌病应要求患者禁声并停用抗生素,同时予抗真菌药物治疗至关重要。     

一种喉部疾病口语声诊断新方法

本文提出了声带的三质量块模型,并应用这模型模拟病噪产生的嘶哑语声,这些嘶声包括有声带闭合不全,声带小结,声带麻痹,喉炎,声带淀粉样变和声门癌等十六种典型情况。采用快速傅里叶变换,线性预测,倒谱技术和离荼余弦变换等分析各类喉病引起的嘶哑语声,实验结果表明声带模型分析法是喉病诊断的一种有效方法。     

Resistance and reactance of the excised human larynx, trachea, and main bronchi

We investigated the impedance of excised preparations of the human larynx before and after resection of the vocal cords and of the trachea whether or not in connection with the main bronchi for steady (75-700 ml.s-1) and oscillatory flows (4-64 Hz). To simulate the influence of respiratory flow on oscillatory resistance (Rosc), oscillatory and steady flow were superimposed. This resulted in a marked increase of Rosc, dependent on the value of steady flow, a change of the frequency dependence of Rosc, and a decrease of the reactance. The latter effects were particularly pronounced in the preparations of the larynx, especially with a narrow glottis opening. The influence of steady flow on oscillatory resistances is probably the expression of interactions of steady and oscillatory flow regimes in the larynx. Similar but less pronounced interactions are also met in the trachea. These effects lead to a systematic overestimation of upper airway resistance when measured during spontaneous breathing by means of a forced oscillation technique.     

Design of a mechanical larynx with agarose as a soft tissue substitute for vocal fold applications

Mechanical and computational models consisting of flow channels with convergent and oscillating constrictions have been applied to study the dynamics of human vocal fold vibration. To the best of our knowledge, no mechanical model has been studied using a material substitute with similar physical properties to the human vocal fold for surgical experimentation. In this study, we design and develop a mechanical larynx with agarose as a vocal fold substitute, and assess its suitability for surgical experimentation. Agarose is selected as a substitute for the vocal fold as it exhibits similar nonlinear hyperelastic characteristics to biological soft tissue. Through uniaxial compression and extension tests, we determined that agarose of 0.375% concentration most closely resembles the vocal fold mucosa and ligament of a 20-year old male for small tensile strain with an R(2) value of 0.9634 and root mean square error of 344.05±39.84?Pa. Incisions of 10 mm lengthwise and 3 mm in depth were created parallel to the medial edge on the superior surface of agar phantom. These were subjected to vibrations of 80, 130, and 180 Hz, at constant amplitude of 0.9 mm over a period of 10 min each in the mechanical larynx model. Lateral expansion of the incision was observed to be most significant for the lower frequency of 80 Hz. This model serves as a basis for future assessments of wound closure techniques during microsurgery to the vocal fold.     

Some aspects of dimorphism and human speech

The production of human speech involves thre supralaryngeal airway filtering the acoustic energy generated by either laryngeal or noise sources. Both the supralaryngeal vocal tract and the larynx are subject to sexual dimorphism in anatomically modernHomo sapiens, yielding acoustic signals that can convey a speaker’s sex. Formant frequencies can be lower because the adult male supralaryngeal vocal tract is often longer. The fundamental frequency of phonation also can be lower because of the enlargement of the thyroid cartilage of the larynx and concomitant increases in the length and mass of the vocal cords. Secondary, learned supralaryngeal vocal tract maneuvers can also lower or raise formant frequencies. These acoustic effects yield male-female «microphonetic» dialects that are ultimately related to the average dimorphism found in the adult population. The dimorphism anatomy of the supralaryngeal vocal tract and larynx of fossil hominoids can be inferred from their skulls.     

Sexually dimorphic laryngeal morphology in Rana pipiens

The sexually dimorphic vocal characteristics of Rana pipiens release calls suggest that there may be differences in the anatomical components of the larynx. The volumes of the arytenoid cartilage, surrounding muscle masses, vocal cords, supporting bronchial process, and the release-call amplitudes of six males and five females were measured in same-sized animals and sexual differences assessed. No qualitative differences in laryngeal morphology were observed, but all features measured except vocal cords were significantly larger in males. The implications of an increased laryngeal size are discussed in relation to differences previously observed in the vocalizations of this and other species and in relation to prior suggestions regarding the developmental basis of anuran sexual dimorphisms.     

Air trapping and arboreal locomotor adaptation in primates: a review of experiments on humans

A review was made of experiments on humans in which air trapping by glottis closure during three-dimensional movements were examined in four subjects including former Olympic gymnasts. In brachiation and horizontal bar exercises, the behaviour of the larynx was monitored with a fiberoptic endoscope, and EMG-data were recorded from shoulder muscles. The results revealed that immobilization of the polyaxial connection between the shoulder girdle and the thorax by air trapping occurs in phases of extreme loading of the upper limbs. The closure of the airway by the larynx in humans serves three functions: first, the prevention of errors in deglutition; second, the production of vocal sounds; third, the retention of air inside the thoracic cavity. The latter function, air trapping, allows the immobilization of the rib cage for the muscular fixation of the shoulder blade on the trunk in movements that imply unusually high external forces acting on the upper limbs. This morphological-functional innovation probably has been made when early mammals invaded the three dimensional arboreal habitat, because it gave the tree-dwelling early primates the device to anchor themselves by the arms alone and to avoid falling out of trees. The specific functional characteristic of primates is the hermetic closure of the vocal and vestibular folds by rapidly contracting muscles in the folds. So the closure of the glottis, which in humans seems primarily an adaptation to the production of vocal tones, seems to go back to the adaptation of Tertiary arboreal primates to movements in a three-dimensional environment. Our conclusions are in agreement with the results of other contributions to this volume.     

Snoring source identification and snoring noise prediction

This paper investigates the snoring mechanism of humans by applying the concept of structural intensity to a three-dimensional (3D) finite element model of a human head, which includes: the upper part of the head, neck, soft palate, hard palate, tongue, nasal cavity and the surrounding walls of the pharynx. Results show that for 20, 40 and 60Hz pressure loads, tissue vibration is mainly in the areas of the soft palate, the tongue and the nasal cavity. For predicting the snoring noise level, a 3D boundary element cavity model of the upper airway in the nasal cavity is generated. The snoring noise level is predicted for a prescribed airflow loading, and its range agrees with published measurements. These models may be further developed to study the various snoring mechanisms for different groups of patients.     

A nonlinear viscoelastic finite element model of polyethylene

A nonlinear viscoelastic finite element model of ultra-high molecular weight polyethylene (UHMWPE) was developed in this study. Eight cylindrical specimens were machined from ram extruded UHMWPE bar stock (GUR 1020) and tested under constant compression at 7% strain for 100 sec. The stress strain data during the initial ramp up to 7% strain was utilized to model the "instantaneous" stress-strain response using a Mooney-Rivlin material model. The viscoelastic behavior was modeled using the time-dependent relaxation in stress seen after the initial maximum stress was achieved using a stored energy formulation. A cylindrical model of similar dimensions was created using a finite element analysis software program. The cylinder was made up of hexahedral elements, which were given the material properties utilizing the "instantaneous" stress-strain curve and the energy-relaxation curve obtained from the experimental data. The cylinder was compressed between two flat rigid bodies that simulated the fixtures of the testing machine. Experimental stress-relaxation, creep and dynamic testing data were then used to validate the model. The mean error for predicted versus experimental data for stress relaxation at different strain levels was 4.2%. The mean error for the creep test was 7% and for dynamic test was 5.4%. Finally, dynamic loading in a hip arthroplasty was modeled and validated experimentally with an error of 8%. This study establishes a working finite element material model of UHMWPE that can be utilized to simulate a variety of postoperative arthroplasty conditions.     

Sound Production in the Salientia: Mechanism and Evolution of the Emitter

Frog sounds involve expulsion of air through the larynx. Inmating, release, rain, and territorial calls, the air vibratesvocal cords and/or arytenoid cartilages. Sound is amplifiedand radiated by the distended buccal cavity and vocal sacs.Distress calls are emitted with open mouth, with minimum laryngealmodulation. The trunk is filled by inflation cycles, but airis driven out by synchronized contractions of the body wallmusculature. The pressure levels are more than five times thoseduring ventilation. In the release call of Bufo valliceps the dilatators and constrictorsof the larynx fire simultaneously keeping the larynx closed.As the pulmonary pressure reaches a peak they cease firing.The arytenoids then separate and vibrate, as do the vocal cords.The dilatators terminate the sound pulse by pulling vibratorsout of the air stream, hence the very sharp termination. Prolongedrelease call sequences include interpulse Teinflations thatreturn air from buccal cavity to lung. Frogs apparently evolved from amphibians too small to use aspirationbreathing. Vocalization represented a critical factor in theirsocial organization and its importance locked these animalsinto reliance upon pulse-pumping rather than the more efficientaspiration breathing.     

OSAHS患者上气道和软腭的流固耦合有限元模型的建立

目的:重建OSAHS患者上气道和软腭的流固耦合有限元模型,研究OSAHS患者上气道及软腭气流动力学特征,为进一步探讨OSAHS的的发病机制奠定基础。方法:对一名中度OSAHS患者的上气道及周围组织进行MRI扫描,将以DICOM格式存储的扫描数据导入Mimics15.0软件中进行预处理,得到上气道和软腭的模型;再利用逆向工程软件Geomagic Studio 2013建立了2 mm气道壁;然后在3-D重建软件NX中,生成气道壁和气道以及软腭之间的组合模型;最后将该组合模型导入ANSYS Workbench13.0软件中,通过网格划分、定义材料属性、设定模型的边界条件操作建立了上气道和软腭的流固耦合有限元模型。结果:利用Mimics、Ansys等软件建立了完整的上气道和软腭的流固耦合有限元模型。共得到气道:2806835单元和529281个节点;气道壁:2304348单元和3487609个节点;软腭:131855单元和204784个节点。结论:本研究建立的上气道及软腭的流固耦合有限元模型符合人体的生物力学特点,为下一步的数值模拟实验提供了一个更真实、可靠的模型。