Effect of dynamic extrathoracic airway obstruction

Effects of forced expiration and inspiration in dynamic extrathoracic airway obstruction. Left panel, during forced expiration, intratracheal pressure (P_tr) exceeds the pressure around the airway (P_atm), lessening the obstruction. Right panel, during forced inspiration, when P_tr falls below P_atm, the obstruction worsens resulting in flow limitation.