Oscillating Positive Expiratory Pressure (Oscillating PEP) devices are small and portable, and are designed to help mobilize and clear mucus from the airways. When the patient exhales through the device, a one-way valve creates intermittent resistance. The resistance holds the airways open while gentle vibrations help shake the mucus loose. The vibration (or oscillation) helps to thin, dislodge and move mucus to the central or upper airways where it can be coughed out. Oscillating PEP treatments may also be combined with small volume nebulizer therapy. When used with the AEROECLIPSE Breath Actuated Nebulizer, patients receive the added benefit of having a nebulizer which creates aerosol only on inhalation. This ensures that no aerosol is lost during the long exhalation efforts required for Oscillating PEP therapy, and has been shown to have aerosol delivery substantially equivalent to using the nebulizer alone.