Peripheral airways mucus clearance in stable asthma is improved by oral corticosteroid therapy

Inhaled 99mTc-labelled particles have been used to assess mucus clearance from peripheral, intermediate and inner lung zones of 12 patients with stable asthma. The method of analysis relies on a ventilation image with 81mKr to estimate the distribution of radioaerosol alveolar deposition so that clearance from each zone can be related just to particles deposited in the ciliated conducting airways. In calculating clearance from intermediate and inner lung zones, allowance is made for particles transported into these zones from more distal regions of the lung. Peripheral zone clearance in the asthmatic subjects improved significantly (p less than 0.01) after four weeks of corticosteroid treatment (two weeks on 15 mg prednisolone orally each day, plus two weeks on 30 mg). No significant change occurred in clearance from the inner zone when all patients were considered together. However, the six patients who prior to treatment coughed relatively infrequently did show a significant (p less than 0.05) increase in clearance from the inner zone as well as from the peripheral zone.