Airway clearance: assessment of techniques.

Mucus hypersecretion and retention of mucus are common in patients with pulmonary disease. In order to reduce mucus retention, airway clearance techniques are used. The most commonly used outcome parameter in clinical situations--pulmonary function testing--is probably not very useful. For research purposes measurement of the transport rate of mucus in the airway using a radioactive tracer technique is probably the most direct outcome parameter. The course and progression of the disease could be used as long-term outcome parameters.