Multiple rib fractures may cause flail chest: a portion of the chest wall “caves” in, which causes a loss of chest wall integrity and prevents adequate lung inflation. Bruised skin, extreme pain caused by rib fracture and disfigurement, paradoxical chest movements, and rapid, shallow respirations are all signs and symptoms of flail chest, as are tachycardia, hypotension, respiratory acidosis, and cyanosis.

Flail chest can also cause tension pneumothorax, a condition in which air enters the chest but can’t be ejected during exhalation; life-threatening thoracic pressure buildup causes lung collapse and subsequent mediastinal shift. The cardinal signs and symptoms of tension pneumothorax include tracheal deviation (away from the affected side), cyanosis, severe dyspnea, absent breath sounds (on the affected side), agitation, jugular vein distention, and shock.

When a rib lacerates lung tissue or an intercostal artery, hemothorax occurs, causing blood to collect in the pleural cavity, thereby compressing the lung and limiting respiratory capacity. It can also result from rupture of large or small pulmonary vessels.

Massive hemothorax is the most common cause of shock following chest trauma. Although slight bleeding occurs even with mild pneumothorax, such bleeding resolves very quickly, usually without changing the patient’s condition.

Rib fractures may also cause pulmonary contusion (resulting in hemoptysis, hypoxia, dyspnea and, possibly, obstruction), large myocardial tears (which can be rapidly fatal), and small myocardial tears (which can cause pericardial effusion).

Myocardial contusions produce electrocardiogram (ECG) abnormalities. Laceration or rupture of the aorta is nearly always immediately fatal. In rare
cases, aortic laceration may develop 24 hours after blunt injury, so patient observation is critical.