Bronchitis mucus hypersecretion

The rate of removal of mucus from the airways is determined by such factors as mucus viscosity, the amount of mucus produced, and the degree of ciliary activity. These processes may be influenced by a variety of diseases, including asthma, cystic fibrosis, and chronic bronchitis [82,83], In patients suffering from cystic fibrosis or chronic bronchitis, mucus hypersecretion is evident and mucociliary function is impaired. The failure to clear mucus from the airways leads to airway obstruction and to chronic colonization of the airways with bacterial organisms (which leads to lung infections and airway inflammation and damage). In asthmatic subjects, airway mucus is more viscous and ciliary transport mechanisms are inhibited [82,83]. In these diseases, the therapeutic objective is to improve mucus clearance from the airways. For example, aerosols of water or saline (especially hypertonic saline) promote clearance of mucus by... 

Chronic mucus hypersecretion, which causes persistent cough with sputum and fits with the original definition of simple chronic bronchitis. This condition arises chiefly in the large airways, usually clears up when the subject stops smoking and does not on its own carry any substantial risk of death. 

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. 

The primary alteration of the respiratory tract of patients with cystic fibrosis is the hypersecretion of mucus. It is not known whether the mucus is normal or contains excessive amounts of electrolytes. In any case, the mucus secretion is not properly evacuated. It first occludes the smaller bronchi. If the occlusion is incomplete, the alveoli become distended, the inspired air cannot be expired, and emphysematous blebs develop. If the obstruction is complete, atelectasis occurs. The changes in the bronchi and the pulmonary parenchyma favor infection, especially by staphylococci. Pulmonary abscesses, bronchial pneumonia, bronchitis, and pneumonia develop in fact, children with cystic fibrosis often die from respiratory infection. Pneumothorax, hemoptysis, and emphysema are rare complications of the pulmonary disturbance observed in cystic fibrosis (see Fig. 4-46). 

In normal conditions, secretion production is small and voluntary coughing is unproductive. However, when disease is present (such as in acute bronchitis), the molecular components change, production increases considerably, and sputum is formed from mucus, inflammatory cells, cell debris, and bacteria. Disruption of normal secretion or mucociliary clearance impairs pulmonary function and lung defense and increases risk of infection (14). However, it is not clear whether hypersecretion is only a marker of inflammation or a cause of pathological changes. There is even some evidence that stasis of mucus protects against inhaled material (15). 

---