A method for treating chest wall injuries, including rib fractures, flail chest injuries or surgical incisions. The method comprising creating a localized airtight compartment external to the chest wall and fully covering the area of injury, varying the pressure within the compartment, and providing dynamic real-time counter forces that act reciprocal to the intrathoracic pressure changes that occur during ventilation. In a preferred embodiment, the apparatus has the capability of sensing the patient's chest wall motion created by ventilation, a pressure control component capable of varying the pressure within the airtight compartment such that it opposes pressure changes within the chest. Said apparatus would be particularly useful in preventing the paradoxical movement of flail chest injuries. The method would also lessen pain experienced by patients with thoracic injuries such as rib fractures and post operative suffering.