Bronchiectasis and Atelectasis
Both bronchiectasis and atelectasis result from damage to a portion of the respiratory tract. In bronchiectasis, the bronchi (the airways that branch off the trachea) are damaged. In atelectasis, part of a lung contracts because of a loss of air.
Bronchiectasis is an irreversible widening (dilation) of portions of the bronchi resulting from dam-age to the bronchial wall.
Bronchiectasis isn't a single disease; it's produced in several ways and results from several conditions that injure the bronchial wall either directly or indirectly by interfering with its defenses. The condition may be diffuse, or it may appear in only one or two areas. Typically, bronchiectasis causes dilation in medium-sized bronchi, but often the smaller bronchi below them become scarred and obliterated. Occasionally, a form of bronchiectasis affecting larger bronchi occurs in allergic bronchopulmonary aspergillosis, a condition caused by an immune response to the Aspergillus fungus.
Normally, the bronchial wall is made up of several layers that vary in thickness and composition in different parts of the airways. The inner lining (mucosa) and the region below it (submucosa) contain cells that help protect the airways and lungs from potentially harmful substances. These cells include mucus-secreting cells, ciliated cells with hairlike projections that help sweep particles and mucus up and out of the airways, and many other cells that play a role in immunity and the defense of the body against invading organisms and other harmful substances. Elastic and muscle fibers and a cartilage layer give the air-ways structure, yet allow the diameter to vary as needed. Blood vessels and lymphoid tissue aid in nourishing and defending the bronchial wall.
In bronchiectasis, areas of the bronchial walls are destroyed and chronically inflamed, the ciliated cells are damaged or destroyed, and mucus production increases. Also, the normal tone of the wall is lost: The affected area becomes wider and flabby and may develop outpouchings or sacs that resemble tiny balloons. The increased mucus promotes the growth of bacteria, often obstructs the bronchus, and leads to pooling of infected secretions and further damage to the bronchial wall. The inflammation can extend to the small air sacs of the lungs (alveoli) and produce broncho-pneumonia, scarring, and a loss of functioning lung tissue. In severe cases, scarring and a loss of blood vessels in the lung ultimately can strain the heart. Also, inflammation and an increase in blood vessels in the bronchial wall can cause a person to cough up blood. Blockage of the damaged air-ways can lead to abnormally low levels of oxygen in the blood.
Many conditions can cause bronchiectasis. The most common cause is infection-either chronic or recurring. Abnormal immune responses, birth abnormalities affecting the structure of the air-ways or the ability of cilia to clear mucus, and mechanical factors such as bronchial obstruction may predispose a person to infections that lead to bronchiectasis. A small number of cases probably result from inhaling toxic substances that injure the bronchi.
Symptoms and Diagnosis
Although bronchiectasis can develop at any age, most often the process begins in early child-hood. However, symptoms may not appear until much later, or they may never appear. Symptoms begin gradually, usually after a respiratory tract infection, and tend to worsen over the years. Most people develop a long-standing cough that produces sputum; the amount and type of sputum depend on how extensive the disease is and whether there's a complicating infection. Often the person has coughing spells only early in the morning and late in the day. Coughing up blood is common and may be the first or only symptom.
Frequent bouts of pneumonia may also be a clue that a person has bronchiectasis. People with widespread bronchiectasis may develop wheezing or shortness of breath; they also may have chronic bronchitis, emphysema, or asthma. Very severe disease, which occurs more commonly in less developed countries, may strain the heart and lead to heart failure - a condition that may cause swelling (edema) of the feet or legs, fluid accumulation in the abdomen, and more difficult breathing, especially when the person is lying down.
Bronchiectasis may be suspected because of a person's symptoms or the presence of another condition associated with it. However, x-ray studies are needed to confirm the diagnosis and assess the extent and location of the disease. Standard chest x-rays may be normal, but sometimes they detect the lung changes caused by bronchiectasis. High resolution computed tomography (CT) can usually confirm the diagnosis and is especially helpful in determining the extent of the disease when surgical treatment is being considered.
After bronchiectasis is diagnosed, tests often are performed to check for diseases that may be causing it. Such tests may include measuring the immunoglobulin levels in blood, measuring the salt levels in sweat (which are abnormal in cystic fibrosis), and examining nasal, bronchial, or sperm specimens to determine if the cilia are structurally or functionally defective. When bronchiectasis is limited to one area-for example, a lung lobe or segment-doctors often perform fiber-optic bronchoscopy (an examination using a viewing tube passed into the bronchi) to deter-mine whether an inhaled foreign object or lung tumor is the cause. Other tests maybe performed to identify underlying diseases, such as allergic bronchopulmonary aspergillosis.
Childhood immunizations against measles and whooping cough have helped reduce the number of people who develop bronchiectasis. Annual influenza vaccines help prevent the destructive damage of flu viruses. The pneumococcal vaccine can help prevent specific types of pneumococcal pneumonia with their severe complications. Taking antibiotics early in the course of infections such as pneumonia and tuberculosis may also prevent bronchiectasis or reduce its severity. Receiving immunoglobulin for an immunoglobulin deficiency syndrome may prevent complicating, recurring infections. Appropriate use of anti-inflammatory drugs such as corticosteroids, especially in those with allergic bronchopulmonary aspergillosis, may prevent the bronchial damage that results in bronchiectasis.
Avoiding the inhalation of noxious fumes, gases, smoke (including tobacco smoke), and injurious dusts (such as silica or talc) also helps prevent bronchiectasis or reduce its severity. Inhalation (aspiration) of foreign objects into the airways may be prevented by carefully checking to see what children put in their mouth, avoiding oversedation from drugs or alcohol, and seeking medical care for neurologic symptoms, such as impaired consciousness, or gastrointestinal symptoms, such as difficulty in swallowing or regurgitation or coughing after eating. Also, oily drops or mineral oil shouldn't be placed in the mouth or nose at bedtime because they can be inhaled into the lungs. Bronchoscopy can be used to detect and treat a bronchial obstruction before severe damage occurs.
Drugs that suppress coughing may worsen the condition and generally shouldn't be used. For people with large amounts of secretions, postural drainage and chest percussion A several times a day help drain the mucus and are essential in managing bronchiectasis.
Infections are treated with antibiotics. Sometimes antibiotics are prescribed for a long period to prevent infections from recurring frequently. Anti-inflammatory drugs such as corticosteroids and mucolytics (drugs that thin the pus and mucus) may also be given. If the blood oxygen level is low, oxygen therapy may help prevent complications such as cor pulmonale (heart disease related to lung disease). If the person has heart failure, diuretics can alleviate some of the swelling. If the person has wheezing or shortness of breath, bronchodilator drugs often help.
Rarely, part of a lung is surgically removed. Such surgery is an option only if the disease is confined to one lung, or preferably to one lung lobe or segment. Surgery may be considered for people who have repeated infections despite treatment or who cough up large amounts of blood. Alternatively, a doctor may deliberately obstruct a bleeding vessel to control bleeding.
Atelectasis is a condition in which part of the lung becomes airless and contracts.
The main cause of atelectasis is an obstruction of a bronchus, one of the two main branches of the trachea leading directly to the lungs. Smaller airways can also become blocked. The obstruction may be caused by a plug of mucus, a tumor, or an inhaled object inside the bronchus. Or the bronchus may be blocked by something pressing from the outside, such as a tumor or enlarged lymph nodes. When an airway becomes blocked, the air in the alveoli is absorbed into the blood-stream, causing the alveoli to shrink and retract. The collapsed lung tissue commonly fills with blood cells, serum, and mucus and becomes infected.
After surgery-especially chest or abdominal surgery-breathing is often shallow, and the lower parts of the lung don't expand properly. Surgery as well as other causes of shallow breathing can lead to atelectasis.
In middle lobe syndrome, a type of long-standing atelectasis, the middle lobe of the right lung con-tracts, usually because of pressure on the bronchus from a tumor or enlarged lymph glands but sometimes without bronchial compression. The blocked, contracted lung may develop pneumonia that fails to clear up completely and leads to chronic inflammation, scarring, and bronchiectasis.
In acceleration atelectasis, which occurs in jet fighter pilots, the high forces generated by high-speed flying close small airways, leading to the collapse of alveoli.
In patchy or diffuse microatelectasis, the surfactant system of the lung is impaired. Surfactant is the substance that coats the lining of the alveoli and reduces surface tension of the alveoli, pre-venting them from collapsing. When premature babies have a surfactant deficiency, they develop neonatal respiratory distress syndrome. Adults can also develop microatelectasis from excessive oxygen therapy, a severe generalized infection (sepsis), or many other factors that injure the lining of the alveoli.
Symptoms and Diagnosis
Atelectasis can develop slowly and cause only slight shortness of breath. People with middle lobe syndrome may have no symptoms at all, al-though many have a hacking cough.
If a large area of a lung develops atelectasis quickly, a person may become blue or ashen and have sharp pain on the affected side and extreme shortness of breath. If there's an accompanying infection, the person also may have a fever and a rapid heart rate; occasionally, the person may have seriously low blood pressure (shock).
Doctors suspect atelectasis based on a per-son's symptoms and the physical examination findings. A chest x-ray that shows the airless area confirms the diagnosis. A computed tomography (CT) scan or fiber-optic bronchoscopy may be performed to find the cause of the blockage.
Prevention and Treatment
People can take steps to avoid atelectasis after surgery. Although people who smoke have a greater risk of developing atelectasis, they can decrease the risk if they stop smoking 6 to 8 weeks before the operation. After an operation, people should be encouraged to breathe deeply, cough regularly, and move about as soon as possible. Breathing devices and exercises may help.
People with chest deformities or neurologic conditions that cause shallow breathing for long periods may benefit from mechanical devices that assist their breathing. The machines apply continuous pressure to the lungs so that even at the end of a breath, the airways can't collapse.
The main treatment for sudden, massive atelectasis is the removal of the underlying cause. If a blockage can't be removed by coughing or by suctioning the airways, it often can be removed by bronchoscopy. Antibiotics are given for any infec-tion. Long-standing atelectasis often is treated with antibiotics because infection is almost inevitable. In certain cases, the affected part of the lung may be removed when recurrent or persistent infection becomes disabling or bleeding is significant. If a tumor is blocking the airway, alleviating the obstruction by surgery or other means may prevent atelectasis from progressing and re-current obstructive pneumonia from developing.
G.D. SNIDER, MD
The author is a Professor of Medicine in USA.
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