Effect of forced expirations on mucus clearance in patients with chronic airflow obstruction: effect of lung recoil pressure.

Spontaneous mucus clearance and the effect of forced expirations and coughing on mucus clearance were investigated in eight patients with chronic airflow obstruction and low elastic recoil pressure (emphysema group: mean FEV1 45% predicted) and in seven patients with chronic airflow obstruction and normal elastic recoil pressure (chronic bronchitis group: mean FEV1 57% predicted). Mucus clearance was measured in a central and a peripheral lung region by a radioactive aerosol tracer technique. Spontaneous mucus clearance from the peripheral lung region was higher in the patients with emphysema than in those with chronic bronchitis. There was no difference in central mucus clearance between the two groups. Mucus clearance from the peripheral lung region increased significantly during forced expirations and coughing in the patients with chronic bronchitis but not in those with emphysema. It is concluded that in patients with chronic airflow obstruction and regular sputum production spontaneous peripheral mucus clearance is greater in those with decreased elastic recoil pressure. Physiotherapy that includes forced expirations and coughing can enhance mucus clearance in such patients when elastic recoil pressure is normal but is unlikely to be effective when elastic recoil pressure is decreased.