Flail chest is a serious consequence of blunt force trauma to the chest wall, representing a severe structural injury that compromises a person’s ability to breathe effectively. The condition is a life-threatening medical emergency because it destabilizes the protective cage around the heart and lungs. When a portion of the rib cage loses its connection to the rest of the chest, the mechanical forces required for proper respiration are dramatically impaired. This instability places the patient at immediate risk of respiratory failure and requires prompt intervention.
How the Injury Occurs
Flail chest results from a high-impact injury that causes a specific pattern of fractures in the rib cage. For the condition to occur, at least three adjacent ribs must be broken, and each of those ribs must be fractured in two or more separate places. This segmental fracturing isolates a section of the chest wall, effectively turning it into a “floating” segment.
The force required to cause this degree of damage is substantial, indicating significant kinetic energy transfer to the torso. Motor vehicle collisions are the most common cause, accounting for a majority of cases. Falls from significant heights or severe crushing injuries are also frequent causes, especially in older adults whose bones may be more susceptible to fractures due to osteoporosis. The severity of the trauma means that underlying structures, particularly the lungs, are almost always injured.
Key Symptoms and Paradoxical Movement
The clinical presentation of a flail chest is marked by intense, localized chest wall pain and significant respiratory distress. The pain itself limits the patient’s ability to take deep breaths, leading to rapid, shallow breathing, known as tachypnea and dyspnea. The most distinctive and defining sign of a flail chest is the paradoxical movement of the injured segment during respiration.
Paradoxical respiration occurs because the detached rib segment is no longer supported by the surrounding bone structure and instead responds to internal pressure changes within the chest cavity. During inhalation, the diaphragm contracts and the rest of the chest expands outward, which creates a negative pressure inside the thorax to draw air into the lungs. This negative pressure pulls the floating segment inward, opposite the movement of the intact chest wall.
Conversely, during exhalation, the chest wall moves inward, increasing the pressure inside the thorax. This positive pressure pushes the flail segment outward, moving in the opposite direction of the normal chest wall contraction. This inefficient movement compromises the amount of air exchanged and increases the work of breathing, placing considerable strain on the patient’s respiratory system.
Emergency Treatment and Stabilization
Flail chest requires immediate medical intervention, with the primary goals being pain control, respiratory support, and stabilization of the chest wall. Aggressive pain management is primary because intense pain prevents the patient from taking the deep breaths necessary to clear secretions and prevent lung collapse. Regional anesthesia techniques, such as intercostal nerve blocks or epidurals, are often employed to provide sustained, targeted pain relief.
A major concern in flail chest is the associated pulmonary contusion, or lung bruising, which is often a greater cause of respiratory failure than the bony instability itself. The blunt force trauma damages the lung tissue, causing bleeding and fluid accumulation that impairs gas exchange. Supportive care for the contusion includes careful monitoring of fluids and supplemental oxygen, often delivered via a face mask.
For patients experiencing respiratory failure or who cannot be adequately oxygenated, mechanical ventilation may be necessary to support breathing and stabilize the internal pressure dynamics. The use of positive pressure ventilation can internally “splint” the lung, which helps eliminate the paradoxical movement of the flail segment. Surgical stabilization of the rib fractures (SSRF) may be performed. This procedure uses plates and screws to physically reattach the broken segments, which can reduce the time spent on a ventilator and improve long-term outcomes.