What causes pneumothorax?Under normal conditions, the pressure in the pleural space, the area around the lungs, is lower than the pressure inside the lungs. However, if air is able to enter the pleural space, the pressure outside the lungs becomes too great, causing part or all of a lung to collapse. The lungs are located inside the chest cavity, which is a hollow space. Air is drawn into the lungs by the diaphragm (a powerful abdominal muscle). The pleural cavity is the region between the chest wall and the lungs. If air enters the pleural cavity, either from the outside or from the lung, the lung collapses and it becomes mechanically
impossible for the injured person to breathe, even with a patent airway. If a piece of tissue forms a one-way valve that allows air to enter the pleural cavity from the lung but not to escape, overpressure can build up with every breath; this is known as tension pneumothorax. It may lead to severe shortness of breath as well as circulatory collapse, both life-threatening conditions. Small pneumothoraces often resolve spontaneously and may require no other treatment than clinical observation. A large pneumothorax or tension pneumothorax is a medical emergency and may require surgery.
A pneumothorax is usually caused by an injury to the chest, such as a broken rib or puncture wound. It may also occur suddenly without an injury (spontaneous pneumothorax). Spontaneous pneumothorax can result from damage to the lungs caused by conditions such as chronic obstructive pulmonary disease (COPD), asthma, cystic fibrosis, and pneumonia. There are several types of pneumothorax, which are classified by cause. Spontaneous pneumothorax is the occurrence of pneumothorax without a clear cause. Primary spontaneous pneumothorax occurs when there is no known underlying lung disease. It is thought to be caused by the rupture of a small, air-filled sac in the lung called a bleb or a bulla. The disease affects tall, thin men between 20 and 40 years old most frequently. Cigarette smoking and family history are contributing factors. Secondary spontaneous pneumothorax is a complication of underlying pulmonary (lung) disease, such as COPD, asthma, cystic fibrosis, tuberculosis, and whooping cough. Traumatic pneumothorax results from a traumatic injury to the chest. The trauma may be penetrating (stab wound, gunshot) or blunt (blow from a motor vehicle accident). Pneumothorax may complicate certain medical procedures. Tension pneumothorax is caused when excessive pressure builds up around the lung, forcing it to collapse. The excessive pressure can also prevent the heart from pumping blood effectively, leading to shock.