4. Airway oscillation. Various devices have been developed to superimpose an oscillatory wave flow over normal breathing. The oscillating pressure wave is intended to help mobilise secretions and expand atelectatic areas of the lung. This can be achieved by an external vibrating vest or delivered directly to the airway through a face mask. Prospective study of the vibrating vest showed that it had no benefit(19). However, research exists that oscillation via mask is beneficial both in short(20) and longer term studies(21).