Pulmonary ventilator methods and systems are provided winch include a housing having a user interface control panel; a pneumatic circuit for delivering a high frequency pressure wave from the housing to a patient lung; a variable volume disposed within the housing including a stationary plate secured to the housing and a reciprocating plate pivotably mounted with respect to the stationary plate; and a magnet assembly disposed within the housing and configured to pivot the reciprocating plate. The variable volume may also include a resiliently contractible section extending between and joining a portion of the stationary plate and a portion of the reciprocating plate, wherein the resiliently contractible section may be in the form of a bellows and/or a pleated material.