Ventilation/ perfusion mismatch can develop with increasing severity of the disease, leading to variations in gas exchange; hence, the expired minute ventilation and the ratio of dead space to tidal volume together with blood gases should be measured to monitor such changes. Since a direct effect of mucoactive drugs on pulmonary function is not expected, measurement of pulmonary function should not represent a primary end point. Although statistically significant changes can be demonstrated, their clinical relevance should be carefully addressed.
Mucoactive drugs are supposed to exert an indirect effect on such lung functions, probably mediated by a change in mucus clearance. The rate of mucus clearance can be measured in vivo in human subjects using inhaled radiolabelled aerosols and monitoring loss of radioactivity from the chest over time or by monitoring movement of inert particles deposited in the trachea via fiberoptic bronchoscopy. It is important that the deposition of the radiolabelled or inert particles is comparable at the beginning of the clearance measurement. canadian health mall
Chronic bronchitis is characterized by chronic cough and expectoration, chest discomfort, and in the case of associated airway obstruction, by progressing dyspnea. Increase in airway secretion reduces mucociliary transport together with cough frequency and efficiency; it alters the ciliated epithelium leading to airways congestion and chest discomfort. Patients may complain of difficulty in bringing up airway secretions and of recurrent bronchial infections. A frequent complication of CB is acute exacerbation characterized by worsening of symptoms, such as an increase in cough severity and frequency, an increase in airway secretions, alteration in macroscopic appearance (purulence) and physical properties, and chest discomfort often associated with dyspnea because of increased airway obstruction, sometimes also associated with malaise and/or fever.