A pneumothorax is collection of air in the pleural space between the lung and the chest wall. Symptoms typically include sudden onset of sharp, one-sided chest pain and shortness of breath. In a minority of cases, a one-way valve is formed by an area of damaged tissue, in which case the air pressure in the space between chest wall and lungs can be higher; this has been historically referred to as a tension pneumothorax, although its existence among spontaneous episodes is a matter of debate. This can cause a steadily worsening oxygen shortage and low blood pressure, leading to a potentially-fatal obstructive shock unless reversed. Very rarely, both lungs may be affected by a pneumothorax. It is often called a "collapsed lung", although that term may also refer to atelectasis. A primary spontaneous pneumothorax is one that occurs without an apparent cause and in the absence of significant lung disease. Its occurrence is fundamentally a nuisance. A secondary spontaneous pneumothorax occurs in the presence of existing lung disease. Smoking increases the risk of primary spontaneous pneumothorax, while the main underlying causes for secondary pneumothorax are COPD, asthma, and tuberculosis. A traumatic pneumothorax can develop from physical trauma to the chest (including a blast injury) or from a complication of a healthcare intervention. Diagnosis of a pneumothorax by physical examination alone can be difficult (particularly in smaller pneumothoraces). A chest X-ray, computed tomography (CT) scan, or ultrasound is usually used to confirm its presence. Other conditions that can result in similar symptoms include a hemothorax (buildup of blood in the pleural space), pulmonary embolism, and heart attack. A large bulla may look similar on a chest X-ray. A small spontaneous pneumothorax will typically resolve without treatment and requires only monitoring. This approach may be most appropriate in people who have no underlying lung disease. In a larger pneumothorax, or if there is shortness of breath, the air may be removed with a syringe or a chest tube connected to a one-way valve system. Occasionally, surgery may be required if tube drainage is unsuccessful, or as a preventive measure, if there have been repeated episodes. The surgical treatments usually involve pleurodesis (in which the layers of pleura are induced to stick together) or pleurectomy (the surgical removal of pleural membranes). Conservative management of primary spontaneous pneumothorax is noninferior to interventional management, with a lower risk of serious adverse events. About 17–23 cases of pneumothorax occur per 100,000 people per year. They are more common in men than women.
Signs and symptoms A primary spontaneous pneumothorax (PSP) tends to occur in a young adult without underlying lung problems, and usually causes limited symptoms. Chest pain and sometimes mild breathlessness are the usual predominant presenting features. In newborns tachypnea, cyanosis and grunting are the most common presenting symptoms. People who are affected by a PSP are often unaware of the potential danger and may wait several days before seeking medical attention. PSPs more commonly occur during changes in atmospheric pressure, explaining to some extent why episodes of pneumothorax may happen in clusters. It is rare for a PSP to cause a tension pneumothorax. Secondary spontaneous pneumothoraces (SSPs), by definition, occur in individuals with significant underlying lung disease. Symptoms in SSPs tend to be more severe than in PSPs, as the unaffected lungs are generally unable to replace the loss of function in the affected lungs. Hypoxemia (decreased blood-oxygen levels) is usually present and may be observed as cyanosis (blue discoloration of the lips and skin). Hypercapnia (accumulation of carbon dioxide in the blood) is sometimes encountered; this may cause confusion and – if very severe – may result in comas. The sudden onset of breathlessness in someone with chronic obstructive pulmonary disease (COPD), cystic fibrosis, or other serious lung diseases should therefore prompt investigations to identify the possibility of a pneumothorax. Traumatic pneumothorax most commonly occurs when the chest wall is pierced, such as when a stab wound or gunshot wound allows air to enter the pleural space, or because some other mechanical injury to the lung compromises the integrity of the involved structures. Traumatic pneumothoraces have been found to occur in up to half of all cases of chest trauma, with only rib fractures being more common in this group. The pneumothorax can be occult (not readily apparent) in half of these cases, but may enlarge – particularly if mechanical ventilation is required. They are also encountered in people already receiving mechanical ventilation for some other reason. Upon physical examination, breath sounds (heard with a stethoscope) may be diminished on the affected side, partly because air in the pleural space dampens the transmission of sound. Measures of the conduction of vocal vibrations to the surface of the chest may be altered. Percussion of the chest may be perceived as hyperresonant (like a booming drum), and vocal resonance and tactile fremitus can both be noticeably decreased. Importantly, the volume of the pneumothorax may not be well correlated with the intensity of the symptoms experienced by the victim, and physical signs may not be apparent if the pneumothorax is relatively small.
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