An apparatus for applying pressure and high frequency pressure pulses to the thorax of a person comprising: a garment having an air core adapted to be located on the thorax of the person for subjecting the thorax of the person to pressure and high frequency pressure pulses, a housing having an interior enclosed space, an air inlet passage for allowing air to flow into the enclosed space, and an air outlet passage for allowing air and air pressure pulses to exit from the enclosed space, a hose member connected to the garment and housing for transporting air and air pressure pulses from the air outlet passage to the air core of the garment, a first air displacer located in said enclosed space, a second air displacer located in said enclosed space, said first and second air displacers (152, 153) separating the enclosed space into first, second and third chambers, said first and second chambers being open to the air inlet passage for allowing air to flow into the first and second chambers, said third chamber being located between said first and second air displacers (152, 153) and open to the air outlet passage for allowing air and air pressure pulses to flow out of the third chamber to the hose member connected to the garment and housing, characterized in that the apparatus further comprises first pivot members pivotally mounting the first air displacer on said housing for angular movement in said enclosed space, second pivot members pivotally mounting the second air displacer on said housing for angular movement in said enclosed space, an air flow control valve mounted on each first and second air displacer (152, 153) operable to allow air to flow from the first and second chambers into the third chamber and prevent air to flow from the third chamber into the first and second chambers, a first power transmission mechanism located in said first chamber and rotatably mounted on the housing operable to angularly move said first air displacer between first and second positions, a second power transmission mechanism located in said second chamber and rotatably mounted on the housing operable to angularly move said second air displacer between first and second positions, a power transmission assembly operably connected to the first and second power transmission mechanisms (179, 189) to concurrently operate the first and second power transmission mechanisms (179, 189) to angularly move the first and second air displacers (152, 153) in opposite directions toward and away from each other to draw air into the first and second chambers and force air through the air flow control valves into the third chamber and expel air and air pressure pulses out of the third chamber for transport into the air core of the garment, and a motor for driving the power transmission assembly whereby the first and second power transmission mechanisms (179, 189) angularly move the first and second displacers (152, 153) in opposite directions toward and away from each other. a garment having an air core adapted to be located on the thorax of the person for subjecting the thorax of the person to pressure and high frequency pressure pulses, a housing having an interior enclosed space, an air inlet passage for allowing air to flow into the enclosed space, and an air outlet passage for allowing air and air pressure pulses to exit from the enclosed space, a hose member connected to the garment and housing for transporting air and air pressure pulses from the air outlet passage to the air core of the garment, a first air displacer located in said enclosed space, first pivot members pivotally mounting the first air displacer on said housing for angular movement in said enclosed space, second pivot members pivotally mounting the second air displacer on said housing for angular movement in said enclosed space, an air flow control valve mounted on each first and second air displacer (152, 153) operable to allow air to flow from the first and second chambers into the third chamber and prevent air to flow from the third chamber into the first and second chambers, a first power transmission mechanism located in said first chamber and rotatably mounted on the housing operable to angularly move said first air displacer between first and second positions, a second power transmission mechanism located in said second chamber and rotatably mounted on the housing operable to angularly move said second air displacer between first and second positions, a power transmission assembly operably connected to the first and second power transmission mechanisms (179, 189) to concurrently operate the first and second power transmission mechanisms (179, 189) to angularly move the first and second air displacers (152, 153) in opposite directions toward and away from each other to draw air into the first and second chambers and force air through the air flow control valves into the third chamber and expel air and air pressure pulses out of the third chamber for transport into the air core of the garment, and a motor for driving the power transmission assembly whereby the first and second power transmission mechanisms (179, 189) angularly move the first and second displacers (152, 153) in opposite directions toward and away from each other.