A respiratory treatment device having an inlet configured to receive exhaled air into the device, an outlet configured to permit exhaled air to exit the device, a valve moveable in response to a threshold exhalation pressure at the inlet between a closed position where the flow of air from the inlet to the outlet is restricted, and an open exhalation position where the flow of air from the inlet to the outlet is less restricted, and a valve brace configured to support the valve, wherein a position of the valve brace relative to the valve is selectively adjustable to increase or decrease the threshold exhalation pressure.
