US Patent 6910479 Airway treatment apparatus with bias line cancellation

An airway clearance system and method produces high frequency chest wall oscillations (HFCWO) and increased airflow velocities through the air passages to clear the lungs of mucus. The system includes a chest wall force applicator to produce the HFCWO by applying an oscillating force component and a steady state (or bias line) force component. An air pressure input mouthpiece system that supplies airflow to a mouthpiece with a steady state, air component which tends to counteract or cancel the bias line force component.