Asthma, General | May 13, 2015 | Author: The Super Pharmacist
Pneumothorax is a condition in which air comes between the lungs and the inside of the chest cavity.1 Pneumothorax is also called a “collapsed lung” because the lung on the affected side appears deflated on x-ray. A particular kind of pneumothorax, called tension pneumothorax, is a life-threatening, medical emergency in which air inside the chest cavity presses on the lungs and heart.
Under normal circumstances, there is virtually no space between the lung and the inside of the chest cavity. The thin covering over the lungs, called the visceral pleura is separated from the lining of the chest cavity (parietal pleura) by a thin layer of liquid. As the diaphragm at the base of the lungs contracts, the chest cavity expands. Because the visceral and parietal pleura are so tightly associated with one another, the lungs expand. This creates a vacuum that draws air into the lungs. Exhalation is a passive process, air rushes out of the lungs as the diaphragm and muscles of the chest relax.
If air gets between the lung and the chest cavity (between the parietal and visceral pleura), the lung no longer expands as the chest expands. There is no vacuum between the two pleura, and the lung cannot inflate during inspiration. Therefore, pneumothorax usually causes shortness of breath that comes on quickly. Along with shortness of breath, the patient usually experiences pleuritic chest pain, which is a sharp chest pain that is made worse by breathing or coughing.1
Spontaneous pneumothorax simply refers to a collapsed lung that occurs without any obvious trauma to the lungs. The condition is sometimes further subdivided into primary and secondary pneumothorax. Primary pneumothorax is a collapsed lung that occurs without any apparent lung disease. Secondary pneumothorax, on the other hand, occurs as a result of some underlying disease of the lung. Primary Spontaneous Pneumothorax Primary spontaneous pneumothorax, or a collapsed lung in someone without apparent lung disease, usually occurs during late teens and 20s. It is much less common by the time a person reaches age 40.2 Cigarette smoking is a major risk factor for primary spontaneous pneumothorax. The risk of a spontaneous collapsed lung is seven times greater in someone who smokes half a pack a day than in a non-smoker.3 Moreover, pneumothorax is 21 times higher in someone who smokes up to a pack a day, and an astonishing 102 times more likely in someone who smokes more than a pack of cigarettes per day.3 People with certain genetic predisposition or conditions are at greater risk for primary spontaneous pneumothorax. The condition is more likely in people who have Marfan syndrome, homocysteine urea, and Birt-Hogg-Dube syndrome.4,5 This form of pneumothorax is believed to occur from inflammation in the lungs. Abnormalities in the lungs called blebs or bullae rupture and allow air to move from the lungs into the chest cavity, within the pleural space. This collapses the lung and causes pneumothorax. This process is truly spontaneous since most cases occur while people are at rest.6 Secondary Spontaneous Pneumothorax Secondary spontaneous pneumothorax occurs in the presence of lung disease. More than 50% of cases occur in individuals with chronic obstructive pulmonary disease or COPD.1 In fact, the risk of this form of collapsed lung increases as COPD gets worse.7 Secondary spontaneous pneumothorax may also be caused by asthma, cystic fibrosis, lung cancer, tuberculosis of the lungs, and other interstitial lung disease.7 Thoracic endometriosis or catamenial pneumothorax can be considered a form of secondary spontaneous pneumothorax, but only affects women of childbearing age.8
During spontaneous pneumothorax, the air between the lung and the chest wall is at the same pressure as the air within the lung. This simply keeps the lung from inflating. However, if air pressure in the pleural space increases beyond the air pressure in the lungs, it is called tension pneumothorax.9 This occurs when a tear or hole in the lungs creates a one-way valve, air can move into the pleural space but not back into the lungs. Therefore, with each breath more and more pressure builds up inside the chest cavity and presses on the other lung, heart, esophagus, and other tissues within the neck and chest. Tension pneumothorax may be caused by trauma to the chest or it may be a complication of a spontaneous pneumothorax.9
The first set of treatments for pneumothorax involves stabilisation. Therefore, initial treatment is tailored to the severity of the condition. A person with a small pneumothorax (the lung is no greater than 3 cm away from the interior chest wall) may be treated with supplemental oxygen and monitored in a hospital setting.10 As the lung heals, it will "re-inflate" and rejoin the inside of the chest wall. This approach assumes that the patient is clinically stable, which means the patient has good blood pressure, good blood oxygenation, and is in mild clinical distress. Complete resolution of a small pneumothorax usually takes about 10 days. A person with a large pneumothorax (lung is greater than 3 cm away from the interior chest wall) may require a procedure called needle aspiration.11 A needle aspiration is a procedure in which a large bore needle is passed through the chest into the chest cavity and air is released from the pleural space.12 Needle aspiration may also be used for people who are experiencing moderate or severe shortness of breath and/or chest pain. Clinically unstable patients may require a procedure called a tube thoracostomy. In this procedure, a small tube is placed through the chest wall (using local anesthesia) and into the pleural space. The tube is then placed under suction to draw air out of the pleural space and help "re-inflate" the lung. Tension pneumothorax is usually treated with urgent needle aspiration. In this case, a large bore needle is placed into the affected chest and the air inside rushes out. This is followed up with the insertion of a chest tube, under suction.
If people are experiencing their first pneumothorax, little else is done the side stabilisation and observation. However, in people with repeated instances of pneumothorax or pneumothorax related to lung disease (e.g., COPD), more permanent steps may be taken. The goal of these treatments is to help the two sides of the pleura to better stick together. This can be done in one of several ways. The most common way is a process called chemical pleurodesis.13 In chemical pleurodesis, a substance is placed between the parietal and visceral pleura that causes a scarring of the membranes. As the membranes heal, they stick together and it becomes less likely for them to separate if a future pneumothorax were to occur. Common agents used for chemical pleurodesis include talc, doxycycline, and minocycline.14 Physical or mechanical pleurodesis is another option for long-term management of recurrent pneumothorax. The patient undergoes video-assisted thoracoscopic surgery (VATS) during which a surgeon physically abrades the pleura. This may be done using dry gauze, cellulose mesh, or lasers. New research suggests that mechanical produces does not reduce the risk of spontaneous pneumothorax, however15. It is unclear how this will affect clinical practice. If the air leak in the lungs is occurring in one specific location, that area may be removed in a procedure called a pleurectomy.16
The prognosis for primary spontaneous pneumothorax is fair to good. As many as one in three individuals with primary spontaneous pneumothorax will have a recurrence within five years. On the other hand, nearly half of all people with secondary spontaneous pneumothorax will have a recurrence. Smoking cessation can substantially improve prognosis and reduce recurrence.17 Chemical pleurodesis, mechanical pleurodesis, and pleurectomy all appear to greatly reduce the risk of recurrence of pneumothorax.18 Individuals with tension pneumothorax need to be evaluated by trained medical staff immediately and treated definitively to avoid life-threatening complications. If a person with tension pneumothorax is treated promptly and effectively, his or her prognosis is similar to that of spontaneous pneumothorax.9