Biomechanics for Human Upper Airways - myassignmenthelp.com

Question: Discuss about theBiomechanics for Human Upper Airways. Answer: Introduction The Human Upper Airways system is a multifunctional, complicated and ever changing neuromechanical system and its patency require a coordination which is time-to-time of the mechanical and neural behavior that is a factor of the posture(Doblare 2015, p. 456). The human upper airway is an everchanging structure which permits speech, swallowing and respiratory functions. It mechanical behavior and neural control is determined by the evolutionary compromise between these functions hence the system tends to respond rapidly and in a way that is controlled dynamically. There are variations that are experienced in the system during the respiratory cycle which ranges from being awake and asleep and between the stages of sleep. Apneas or hypopneas are a condition that may result from failure of continuous coordination and recruitment of the dilator muscles that are responsible for the counterbalancing of the forces acting to close the airway. An alteration of the passive mechanical behavior of the upper airway may result in its collapse. Such alterations or variations can be due to obesity or variations in the anatomy for example retrognathia. This behavior is a factor of the mechanical behavior of each of the tissues of the mechanical airway in isolation, their physiological interactions as well as their geometric arrangements. The respiratory cycle experiences the different movement of the soft tissue as illustrated by measurements of deformations related to respiration. It is not possible to predict the biomechanical behavior of the human upper airway just from the electromyography activities of its muscles(Fung 2014, p. 367). Mechanical Models of the Human Upper Airway System The pharynx is in most cases thought to be a floppy tube. Mechanical models of collapsible tubes including Starling resistor are used in relating intraluminal pressure, perypharyngeal pressure as well as airflow(Griffiths 2016, p. 287). These relations have provided a basis for the analysis of limitations of flow mechanism when takes place when the rising negative pressure in the epiglottis does not manage to control airflow and how collapse can be encouraged by additional peripharyngeal tissue. The patency of the upper airway has been perceived and understood to be dependent on a balance between activities of the muscles and the pressure of the airway as conceptualized by Isono and the colleagues. This group conceptualized that the airway was balancing on a pivot which represents the intrinsic behavior of the upper airway. Another conceptual model by the same group was involving a balance between intramandibular volume and the soft tissue that gave an explanation on how the posture of the head, jaw, and neck and obesity are able to lower the volume of the oral cavity and the pharynx(Kharmanda 2017, p. 697). The response of the upper airway tissue to a deformation or applied load defines its passive stiffness and is normalized by the area over which the load is applied. This is similar to the modulus of elasticity concept, commonly referred to as Young's modulus which is an expression of the force acting per unit area divided by strain i.e. change in length per unit area. The modulus of elasticity in the upper airways is a factor of the rate of loading, the quantity of load applied and the direction of application of the load. An increase in the load quantity increases the modulus of elasticity and is usually a nonlinear elasticity(Mow 2015, p. 209). This means that in case any of the upper airways tissues are slack or tend to be slack then small pressure variations culminate into enormous deformation of the walls of the airways. Under constant conditions of pressure and force, the tissues are likely to deform over time. On the other hand, application of a constant stretch decreases the tension over time making the tissues to relax even though there is usually a residual stress that is left in the tissue. Tissues tend to be stiffer when the rate of application of the load is higher. These characteristics define the viscoelasticity of the soft tissues of the upper airway. Important to note as well is that muscles are normally stiffer in the direction of the fascicles of the muscles as opposed to perpendicular to them(Bilston 2011, p. 759). This means loads applied in varied anatomical directions end up in different movements. The biochemical responses of the upper airway are influenced by the geometric or anatomical characteristics of the airway. This has been used in explaining the reason for increases OSA rates in males since they have longer pharynx as compared to their female counterparts. This is influenced by two factors. The airway surface area tends to be larger in a longer structure thereby air pressure is applied over a larger area and thus greater force is produced. Another reason is that a longer structure is found to be significantly more flexible than a shorter structure with similar cross section(Middleton 2009, p. 568). References Berme, N 2013, Biomechanics of Normal and Pathological Human Articulating Joints, 3rd edn, Springer Science Business Media, New York. Bilston, LE 2011, Neural Tissue Biomechanics, 10th edn, Springer Science Business Media, Manchester. Doblare, M 2015, Biomechanics, 4th edn, EOLSS Publications, Chicago. Fung, YC 2014, Biomechanics: Circulation, 2nd edn, Springer Science Business Media, Beijing. Griffiths, IW 2016, Principles of Biomechanics Motion Analysis, 5th edn, Lippincott Williams Wilkins, London. Kharmanda, G 2017, Biomechanics: Optimization, Uncertainties, and Reliability, 5th edn, John Wiley Sons, London. Knudson, D 2013, Fundamentals of Biomechanics, 6th edn, Springer Science Business Media, Chicago. Middleton, J 2009, Computer Methods in Biomechanics and Biomedical Engineering 2, 5th edn, CRC Press, London. Mow, VC 2015, Basic Orthopaedic Biomechanics Mechano-biology, 5th edn, Lippincott Williams Wilkins, Manchester. Robertson, G 2013, Research Methods in Biomechanics, 2E, 2nd edn, Human Kinetics, New York.