Flail Chest

What Is It, Causes, Symptoms, and More

Author:Corinne Tarantino, MPH

Editors:Alyssa Haag,Ian Mannarino, MD

Illustrator:Jessica Reynolds, MS

Copyeditor:David G. Walker

What is flail chest?

Flail chest is defined as three or more adjacent ribs that are fractured in at least two places. Less commonly, flail chest can occur when two ribs on both sides of the chest are detached from the sternum, called bilateral costochondral separation. The thoracic cage has 12 pairs of ribs, seven of which are attached to the sternum. The ribs and sternum create the chest wall shape and protect internal structures (e.g., heart and lungs) from injury. Therefore, rib fractures in flail chest injuries require immediate critical care.

Breathing occurs in two stages based on the movements of the diaphragm and the intercostal muscles, which are located between each set of ribs. During inhalation, the diaphragm contracts and moves downward, while the intercostal muscles also contract to move the rib cage outwards. Therefore, the volume of the chest cavity increases while the pressure inside the thoracic cavity decreases. The pressure change subsequently pulls air into the lungs. In contrast, during exhalation, the diaphragm and intercostal muscles relax, decreasing the volume and increasing the pressure of the chest cavity. Air subsequently exits the lungs. In a flail chest, the fractures on adjacent ribs separate them from the rest of the chest wall. As a result, paradoxical motion of the ribs occurs. For example, the affected area may move inward (sucked in by the negative pressure change in the thoracic cavity) while the rest of the chest wall moves outward. This altered movement can consequently impair breathing.

What causes flail chest?

The primary cause of a flail chest is blunt thoracic trauma, or chest trauma, which is an injury caused by a forceful impact with a dull object or surface. Blunt traumas can occur by falls, abuse, car crashes, or as a result of pressure on the sternum and chest during cardiopulmonary respiration (CPR). Individuals are at increased risk for experiencing blunt trauma if they are intoxicated or participate in contact sports. Other individuals who are at an increased risk for flail chest injuries are those of advanced age and who are assigned male at birth.

Flail chest itself can cause several complications. The most common complications are pulmonary contusions, or injuries to the lung parenchyma. This can lead to alveoli collapse (i.e., atelectasis), inhibiting their ability to participate in gas exchange. As a result, blood is unable to become fully oxygenated, called shunting. Individuals experiencing shunting typically develop refractory hypoxemia, where their blood oxygen doesn’t improve even after they are given higher supplemental oxygen concentrations. Ultimately, respiratory distress syndrome (ARDS) or respiratory failure can occur. These individuals are also at an increased risk of developing pneumonia due to trouble breathing or coughing. Sometimes a flail chest may cause air to enter the pleural cavity that surrounds the lung, called a pneumothorax, preventing proper lung expansion. In other cases of flail chest, the fractured ribs can injure the diaphragm or internal organs (e.g., heart, spleen, or liver).

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What are the signs and symptoms of flail chest?

Typically, the signs and symptoms of flail chest include paradoxical breathing, where the chest moves in the opposite direction when breathing (i.e., expanding on inhalation); and pain at fracture sites which intensifies when moving the chest in any way, including during breathing, coughing, or sneezing. 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 (i.e., grinding or crunching sounds). In severe cases of flail chest, individuals can experience shortness of breath, cyanosis, or refractory hypoxemia. They may also develop hemodynamic instability and unstable blood pressure, which can cause arrhythmias, hypotension, or tachycardia. 

How is flail chest diagnosed?

Diagnosis of flail chest begins with a thorough medical examination, including assessment of signs and symptoms, medical history, and a physical examination. This exam is often followed by imaging, most commonly a chest CT scan. Sometimes, a chest X-ray can also be used.

How is flail chest treated?

Treatment of flail chest initially involves splinting (i.e., direct pressure over the affected area), IV fluids, supplemental oxygen, and pain management (i.e., NSAIDs, acetaminophen, nerve blocks, or opioids). To improve lung function and breathing and to prevent pneumonia, chest physiotherapy and pulmonary hygiene (adequate mucus and secretion clearance) is often recommended. Chest tubes may also be necessary. 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. If further intervention is needed, surgery can be performed to stabilize any displaced ribs.

What are the most important facts to know about flail chest?

Flail chest is when three or more adjacent ribs are fractured in at least two places, causing paradoxical motions in the chest. The primary cause of flail chest is blunt chest trauma. Signs and symptoms typically include paradoxical breathing and pain in the affected area that increases with movement. Flail chest is usually diagnosed by medical evaluation and a chest CT scan. Treatment options typically involve splinting, or direct pressure to the chest; supplemental oxygen; IV fluids; pulmonary hygiene and physiotherapy; and pain management.

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Related links

Chest trauma: Clinical practice
Anatomy clinical correlates: Thoracic wall
Respiratory distress syndrome: Pathology review
Compliance of lungs and chest wall

Resources for research and reference

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