Flail Chest · What Is It, Causes, Symptoms, and More

Flail chest is a serious medical condition that occurs when a segment of the rib cage fractures and becomes detached from the rest of the chest wall. It happens when three or more adjacent ribs are fractured in at least two places, allowing a big segment of the thoracic wall to move freely. Less commonly, flail chest can occur when two ribs on both sides of the chest are detached from the sternum, called bilateral costochondral separation.  

Normally, breathing occurs in two stages. During inhalation, the diaphragm contracts and moves downward, while the intercostal muscles also contract to push the rib cage outwards. This causes the volume of the chest cavity to increase while the pressure inside the thoracic cavity decreases. The change in intrathoracic pressure is exactly what pulls air into the lungs. In contrast, during exhalation, the diaphragm and intercostal muscles relax, decreasing the volume of the chest and increasing the pressure within the chest cavity, which pushes air out of the lungs.  

In a flail chest, however, a paradoxical motion of the ribs occurs. This means during inspiration the affected area may move inward (i.e., sucked in by the negative pressure change in the thoracic cavity) while the rest of the chest wall moves outward. During expiration, the exact opposite happens; the affected area moves outward while the rest of the chest wall moves inward. This altered movement disrupts normal respiratory mechanics and can consequently impair breathing. 

The hallmark sign of flail chest is paradoxical chest wall movement, meaning the affected area moves in the opposite direction of the rest of the chest wall when breathing. This injury also causes significant pain which intensifies when moving the chest in any way, including during breathing, coughing, or sneezing. As a result, some individuals show signs of respiratory splinting, where they take short, shallow breaths to reduce pain by limiting chest movement.  

Upon examination, chest auscultation may reveal diminished breath sounds, and chest palpitation may reveal crepitus, which are grinding or crunching sounds caused by the fractured ribs.  

The forceful trauma to the chest also typically causes underlying lung injuries known as pulmonary contusions. These injuries may result in alveolar collapse, impairing gas exchange in affected areas, and leading to impaired blood oxygenation. In severe cases, this may lead to respiratory failure. Additionally, individuals with flail chest frequently experience severe pain that makes normal breathing and effective coughing difficult, increasing their risk of developing pneumonia. Flail chest may also be accompanied by a pneumothorax, or air trapped in the space around the lungs, which further compromises breathing. In some cases, the broken ribs can cause damage to nearby internal organs such as the heart, spleen, or liver, leading to potentially life-threatening complications. 

Treatment of flail chest initially involves supplemental oxygen to maintain adequate oxygen levels and pain management, which may involve medications like NSAIDs and opioids, as well as regional nerve blocks to control the pain.  

If the individual’s condition continues to worsen despite conservative treatment, they may be intubated and started on mechanical ventilation with positive end-expiratory pressure. Surgical intervention may be needed to stabilize the flail segment, reduce pain, and improve breathing, especially in cases of significant deformity or chest wall instability.  

After the acute phase, techniques like postural drainage, percussion, and assisted coughing are encouraged to help remove mucus and secretions, which accumulate due to ineffective coughing from the pain. Finally, deep breathing exercises (e.g., incentive spirometry) may help keep the alveoli open and promote ventilation in underused lung segments.