Lung airway passages

Ahmadi and McLaughlin describe biomedical applications of particle transport and deposition. Special attention is given to recent advances in the use of computational models for predicting the transport, dispersion, and deposition of particles in the human airway passages. These include airflow and particle transport in the nose, oral airways, lung bifurcation, and alveolar cavities. In addition, an overview of advances in blood flow simulations in various arteries is presented. 

Asthma is a common chronic inflammatory disorder that affects the airway passages of the lungs. Primarily, asthma is characterized by reversible, episodic narrowing of the airway s smooth muscle secondary to hypersecretion of mucus, hyper-reactivity, and mucosal edema. The narrowing may be of sudden or prolonged onset, which accounts for the varying degrees of airway obstruction seen in this disease. The hallmark of airway obstruction is a reduction in the forced expiratory volume in 1 second (FEV and the ratio of FEVj to the forced vital capacity (FVC). 

Q9 Bronchoconstriction, airway oedema and breakdown of alveolar walls all contribute to airflow obstruction. Air cannot be easily moved out of the lung during expiration and becomes trapped in the alveoli and small air passages. The air remaining in the lung following a maximal expiration (residual volume) therefore increases. This extra volume of air contributes to an increase in total lung capacity, and over the years alters both the volume and shape of the chest. 

Many, perhaps most, chemical agents exert their lethal effects because of effects on the respiratory system and thus the provision of breathing support is essential. This is because toxic agents produce effects that cause blockage of the air passages, depression and failure of the respiratory control centres in the brain or paralysis of the muscles of respiration. To overcome these combined effects, the emergency medical response must include the ability to be able to clear and support the airway and also to be able to ventilate the lungs artificially when there is respiratory deficiency or arrest. This support is now part of a standard response for advanced life support in both conventional and toxic trauma and is termed TOXALS (Baker, 1996 Department of Health, 2003) (see Box 3). 

Zafirlukast is an oral leukotriene receptor antagonist (LTRA) for the treatment of asthma, often used in conjunction with an inhaled steroid and/or long-acting bronchodilator. Zafirlukast blocks the action of the cysteinyl leukotrienes on the CysLTl receptors, thus reducing constriction of the airways, build-up of mucus in the lungs and inflammation of the breathing passages. 

Airborne particles in order to have an effect on human health have to come into contact with cells and tissues of the human body. The main route of intake is inhalation. To a certain amount inhaled particles will be deposited at the smface of the extra- and intra-thoracic airways and in the alveoli of the lung. The amoimt and site of deposition depends on the aerodynamic and thermodynamic properties of the particles inhaled, particularly on their size and shape. On the contrary the interaction of the particle with the cells and tissues of the body is determined by its physical, chemical and biological properties. During their passage through the airways small hydrophilic particles adsorb immediately water vapoiu and grow significantly in size. 

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