Bronchial mucociliary clearance

Schlesinger, R.B., Naumann, B.D., and Chen, L.C., Physiological and histological alterations in the bronchial mucociliary clearance system of rabbits following intermittent oral or nasal inhalation of sulfuric acid mist, J. Toxicol. Environ. Health. 12, 2-3, 441, 1983. 

Mussatto, D.J., Garrad, C.S. and Lourenco, R.V (1988). The effect of inhaled histamine on human tracheal mucus velocity and bronchial mucociliary clearance. Am. Rev. Respir. Dis. 138 775-779. 

Yeates DB, Daza AV, Mussatto DM. Bronchial and alveolar allergen-induced anaphylaxis and the stimulation of bronchial mucociliary clearance in ragweed sensitized dogs. Proc Assoc Am Physicians 1997 109 440-452. 

Selective sympathomimetics cause relaxation of bronchial smooth muscle and bronchodilation by stimulating the enzyme adenyl cyclase to increase the formation of cyclic adenosine monophosphate. They may also improve mucociliary clearance. 

Clearance in the upper, or ciliated, region is governed by the rate of mucus transport along the airways. These rates have been measured in the human nose and in dogs, rats, and other species. Asmundsson and Kilbum, Hilding, and Iravani established that mucociliary clearance rates increase from the distal bronchi toward the trachea. Because bronchial openings retard mucus flow, bifurcations receive an accumulation of mucus and associated particles. The rate of mucus production and mucus thickness and velocity vary from one person to another. Thickness increases and velocity decreases greatly when some toxic elements are present in the airway. 

Barton, A. D., and R. V. Lourenqo. Bronchial secretions and mucociliary clearance. Biochemical characteristics. Arch. Intern. Med. 131 140-144, 1973. 

The pharmacologic actions of these agents include Alpha-adrenergic stimulation (vasoconstriction, nasal decongestion, pressor effects) - -adrenergic stimulation (increased myocardial contractility and conduction) and 2-adrenergic stimulation (bronchial dilation and vasodilation, enhancement of mucociliary clearance, inhibition... 

Mucociliary clearance (MCC) Ciliary dysfunction, airway caliber, mucus production >2 p,m Primary ciliary dyskinesia, bronchial disorders, lung transplantation... 

Particulates (PMio, PM -) Bronchial irritation, inflammation, increased reactivity, reduced mucociliary clearance, reduced macrophage response... 

Neutrophil elastase is implicated in the induction of bronchial disease, causing structural changes in lungs, impairment of mucociliary clearance, and impairment of host defenses. Protease inhibitors, namely, inhibitors of neutrophil elastase, are being investigated currently for the treatment of COPD. 

A common complication of persistent hypersecretion and mucus plugging is a less effective mucociliary clearance mechanism. Inhaled bacteria which are normally quickly cleared from the bronchial system have greater opportunity for tissue invasion. Chronically affected asthmatics are more likely to develop bacterial bronchitis. It is not unusual for CB to become superimposed on the asthma as a consequence of these infections. Interestingly asthmatics who get an acute bacterial bronchitis will often note an improvement of their asthmatic symptoms. 

In the various regions of the respiratory tract different physiological mechanisms exist to remove foreign material. In the extra-thoracic airways, the trachea and the bronchi there is a thick liquid lining and the synchronous movement of microscopic hairy cila at the surface of the bronchial epithelial cells rapidly moves deposited particles toward the larynx, where they are swallowed (mucociliary clearance). Normally this takes 1-3 days. Only highly soluble material moving from the air into the liquid layer will have systemic access via the blood. 

Respiratory Inhaled mannitol as a dry powder has been used to treat patients with cystic fibrosis, since it increases mucociliary clearance by rehydrating the airways. In 39 children with cystic fibrosis, aged 8-18 years, a bronchial provocation... 

In healthy individuals, mucociliary clearance and cough mechanisms are normally effective and efficient for defense on secretion encumbrance, but may become ineffective if these systems malfunction and in the presence of excessive bronchial secretions. Mucus secretion and clearance are extremely important for airway integrity and pulmonary defense. It has been estimated that mucus secretion volume is between 10 and 100 mL/day in healthy subjects (1). 

The respiratory patient evaluation includes a survey for symptoms of chronic and/or acute alveolar hypoventilation, medical history, physical examination, cough evaluation, and simple pulmonary function tests. Measurement of mucous transport through the bronchial tree by radiolabeled tracers is a technique that has been used above all to study mucociliary clearance, as well as the measurement of the volume of expectorated mucous (32). 

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