A PEP module is provided for producing and transmitting oscillations of expiratory air to the lungs and airways of a user to thereby loosen and mobilize mucus obstructions. The PEP module includes an external device housing having a mouthpiece at a first end thereof and a cover at an opposite second end thereof configured for providing resistance to the airflow of the expiratory air. The PEP module further includes a valve assembly contained within the external housing and disposed medially between the mouthpiece and the cover. The valve assembly includes a valve housing and a valve moveably mounted on the valve housing. The valve rapidly and repeatedly oscillates relative to the valve housing as the user exhales to produce oscillations in the expiratory air that are transmitted to the lungs and airways of the user to loosen and mobilize the mucus obstructions.
