Abstract: A valve assembly attached to a capacitor such that pressurizing the capacitor to a first positive pressure threshold induces the valve assembly to open, the pressurized air is released to the patient, and then as the pressure in the capacitor drops to a second pressure threshold the valve closes and the capacitor begins to build pressure until the first positive pressure threshold is achieved and the process repeats. Relative to the valve assembly and integrated therein, is an incrementally adjustable index knob to vary the rate of a biasing force performing work against the actionable valve face of the diaphragm functional surface to set the performance of the valve assembly, thereby increasing the potential for correct operation across a range of oscillating rates supporting a broad spectrum of patient therapies and types.