lung abscess

Lung Abscess

Definition

Lung abscess is an acute or chronic infection of the lung, marked by a localized collection of pus, inflammation, and destruction of tissue.

Description

Lung abscess is the end result of a number of different disease processes ranging from fungal and bacterial infections to cancer. It can affect anyone at any age. Patients who are most vulnerable include those weakened by cancer and other chronic diseases; patients with a history of substance abuse, diabetes, epilepsy, or poor dental hygiene; patients who have recently had operations under anesthesia; and stroke patients. In children, the most vulnerable patients are those with weakened immune systems, malnutrition, or blunt injuries to the chest.

Causes and symptoms

The immediate cause of most lung abscesses is infection caused by bacteria. About 65% of these infections are produced by anaerobes, which are bacteria that do not need air or oxygen to live. The remaining cases are caused by a mixture of anaerobic and aerobic (air breathing) bacteria. When the bacteria arrive in the lung, they are engulfed or eaten by special cells called phagocytes. The phagocytes release chemicals that contribute to inflammation and eventual necrosis, or death, of a part of the lung tissue. There are several different ways that bacteria can get into the lung.

Aspiration

Aspiration refers to the accidental inhalation of material from the mouth or throat into the airway and lungs. It is responsible for about 50% of cases of lung abscess. The human mouth and gums contain large numbers of anaerobic bacteria; patients with periodontal disease or poor oral hygiene have higher concentrations of these organisms. Aspiration is most likely to occur in patients who are unconscious or semiconscious due to anesthesia, seizures, alcohol and drug abuse, or stroke. Patients who have problems swallowing or coughing, or who have nasogastric tubes in place are also at risk of aspiration.

Bronchial obstruction

The bronchi are the two branches of the windpipe that lead into the lungs. If they are blocked by tissue swelling, cancerous tumors, or foreign objects, a lung abscess may form from infection trapped behind the blockage.

Spread of infection

About 20% of cases of pneumonia that cause the death of lung tissue (necrotizing pneumonia) will develop into lung abscess. Lung abscess can also be caused by the spread of other infections from the liver, abdominal cavity, or open chest wounds. Rarely, AIDS patients can develop lung abscess from Pneumocystis carinii and other organisms that take advantage of a weakened immune system.Lung abscess is usually slow to develop. It may take about two weeks after aspiration or bronchial obstruction for an abscess to produce noticeable symptoms. The patient may be acutely ill for two weeks to three months. In the beginning, the symptoms of lung abscess are difficult to distinguish from those of severe pneumonia. Adults will usually have moderate fever (101-102 °F/38-39 °C), chills, chest pain, and general weakness. Children may or may not have chest pain, but usually suffer weight loss and high fevers. As the illness progresses, about 75% of patients will cough up foul or musty-smelling sputum; some also cough up blood.Lung abscess can lead to serious complications, including emphysema, spread of the abscess to other parts of the lung, hemorrhage, adult respiratory distress syndrome, rupture of the abscess, inflammation of the membrane surrounding the heart, or chronic inflammation of the lung.

Diagnosis

The diagnosis is made on the basis of the patient's medical history (especially recent operations under general anesthesia) and general health as well as imaging studies. Smears and cultures taken from the patient's sputum are not usually very helpful because they will be contaminated with bacteria from the mouth. The doctor will first use a bronchoscope (lighted tube inserted into the windpipe) to rule out the possibility of lung cancer. In some cases of serious infection, the doctor can use a fiberoptic bronchoscope with a protected specimen brush to take material directly from the patient's lungs, for identification of the organism. This technique is time-consuming and expensive, and requires the patient to be taken off antibiotics for 48 hours. It is usually used only to evaluate severely ill patients with weakened immune systems.In most cases, the doctor will use the results of a chest x ray to help distinguish lung abscess from empyema, cancer, tuberculosis, or cysts. In patients with lung abscess, the x ray will show a thick-walled unified clear space or cavity surrounded by solid tissue. There is often a visible air-fluid level. The doctor may also order a CT scan of the chest, in order to have a clearer picture of the exact location of the abscess.Blood tests cannot be used to make a diagnosis of lung abscess, but they can be useful in ruling out other conditions. Patients with lung abscess usually have abnormally high white blood cell counts (leukocytosis) when their blood is tested, but this condition is not unique to lung abscess.

Treatment

Lung abscess is treated with a combination of antibiotic drugs, oxygen therapy, and surgery. The antibiotics that are usually given for lung abscess are penicillin G, penicillin V, and clindamycin. They are given intravenously until the patient shows signs of improvement, and then continued in oral form. The patient may need to take antibiotics for a month or longer, until the chest x ray indicates that the abscess is healing. Oxygen may be given to patients who are having trouble breathing.

Surgical treatment

Most patients with lung abscess will not need surgery. About 5% of patients-usually those who do not respond to antibiotics or are coughing up large amounts of blood (500 mL or more)—may have emergency surgery for removal of the diseased part of the lung or for insertion of a tube to drain the abscess. Antibiotic treatment is considered to have failed if fever and other symptoms continue after 10-14 days of treatment; if chest x rays indicate that the abscess is not shrinking; or if the patient has pneumonia that is spreading to other parts of the lung.

Supportive care

Because lung abscess is a serious condition, patients need quiet and bed rest. Hospital care usually includes increasing the patient's fluid intake to loosen up the secretions in the lungs, and physical therapy to strengthen the patient's breathing muscles.

Follow-up

Patients with lung abscess need careful follow-up care after the acute infection subsides. Follow-up usually includes a series of chest x rays to make sure that the infection has cleared up. Treatment with antibiotics may continue for as long as four months, to prevent recurrence.

Prognosis

About 95% of lung abscess patients can be treated successfully with antibiotics alone. Patients who need surgical treatment have a mortality rate of 10-15%.

Prevention

Some of the conditions that make people more vulnerable to lung abscess concern long-term lifestyle behaviors, such as substance abuse and lack of dental care. Others, however, are connected with chronic illness and hospitalization. Aspiration can be prevented with proper care of unconscious patients, which includes suctioning of throat secretions and positioning patients to promote drainage. Patients who are conscious can be given physical therapy to help them cough up material in their lungs and airways. Patients with weakened immune systems can be isolated from patients with pneumonia or fungal infections.

Resources

Books

Stauffer, John L. "Lung." In Current Medical Diagnosis and Treatment, 1998, edited by Stephen McPhee, et al., 37th ed. Stamford: Appleton & Lange, 1997.

Key terms

Abscess — An area of injured body tissue that fills with pus, as in lung abscess.Anaerobe — A type of bacterium that does not require air or oxygen to live. Anaerobic bacteria are frequent causes of lung abscess.Aspiration — Inhalation of fluid or foreign bodies into the airway or lungs. Aspiration often happens after vomiting.Bronchoscope — A lighted, flexible tube inserted into the windpipe to view the bronchi or withdraw fluid samples for testing. Bronchoscopy with a protected brush can be used in the diagnosis of lung abscess in severely ill patients.Bronchus — One of the two large tubes connecting the windpipe and the lungs.Leukocytosis — An increased level of white cells in the blood. Leukocytosis is a common reaction to infections, including lung abscess.Necrotizing pneumonia — Pneumonia that causes the death of lung tissue. It often precedes the development of lung abscess.Sputum — The substance that is brought up from the lungs and airway when a person coughs or spits. It is usually a mixture of saliva and mucus, but may contain blood or pus in patients with lung abscess or other diseases of the lungs.

lung

[lung] either of two large organs lying within the chest cavity on either side of the heart; they supply the blood with oxygen inhaled from the outside air and dispose of waste carbon dioxide in the exhaled air, as a part of the process known as respiration. Other functions include filtration of blood, serving as reservoirs to store blood, and playing a role in metabolic activities. See also color plates.
The lungs are made of elastic tissue filled with interlacing networks of tubes and sacs carrying air, and with blood vessels carrying blood. The bronchi" >bronchi, which bring air to the lungs, branch out within the lungs into many smaller tubes, the bronchioles" >bronchioles, which culminate in clusters of tiny air sacs called alveoli" >alveoli, whose total runs into millions. The alveoli are surrounded by a network of capillaries. Through the thin membranes of the capillaries, the air and blood make their exchange of oxygen and carbon dioxide.
The lungs are divided into lobes, the left lung having two (the left upper lobe and the left lower lobe) and the right having three (the right upper lobe, the right middle lobe, and the right lower lobe); these are further subdivided into bronchopulmonary segments, of which there are about 20. Protecting each lung is the pleura, a two-layered membrane that envelops the lung and contains lubricating fluid between its inner and outer layers.Mechanics of Inflation and Deflation. The lungs are inflated by action of the diaphragm and the intercostal muscles. The diaphragm, a large dome-shaped muscle, forms the bottom of the thoracic cage. As it contracts it flattens, increasing the diameter of the thorax and elevating the lower ribs. Both of these actions increase the space for expansion of the lungs. The external intercostal muscles provide flexibility to the thoracic cage and allow more room for lung expansion by elevating the anterior end of each rib, thereby increasing the anterior-posterior diameter of the chest wall.
Deflation of the lungs is chiefly a passive maneuver. The major muscles involved in exhalation are the abdominal muscle group. As these muscles contract, they depress the lower ribs, and, through an increase in abdominal pressure, move the diaphragm upward.
As the lungs are compressed and distended by the respiratory muscles, the pressure within the alveoli (intra-alveolar pressure) rises and falls. During inhalation the pressure becomes slightly negative (−3 mm Hg) in relation to atmospheric pressure. During exhalation the intra-alveolar pressure rises to approximately +3 mm Hg. The effect of negative pressure within the alveoli is to cause air under atmospheric pressure to flow into the lungs (inhalation). The condition of positive pressure creates the opposite effect, causing air to flow outward (exhalation).
The lungs are surrounded by an airtight compartment, the pleural space within the pleural membrane. The intrapleural pressure is less than atmospheric pressure and is expressed as negative pressure. Normally the intrapleural pressure is about −4 mm Hg. When the lungs are fully expanded this pressure may be as great as −9 mm Hg. Under normal conditions, however, the intrapleural pressure fluctuates between −4 and −6 mm Hg.
If anything should penetrate the walls of the pleura, the negative pressure is lost as air rushes into the pleural cavity in response to atmospheric pressure. This condition is called pneumothorax. The walls of the alveoli also must remain intact in order to maintain normal intrapleural pressure. If a lesion causes a break in the alveolar membranes, air enters the pleural cavity through the break and produces pneumothorax. Relief of pneumothorax and collapse of the lung from accumulations of either air or fluids within the pleural space may be provided by aspiration of the air or fluid from the thoracic cavity (thoracentesis) or by insertion of chest tubes to provide for a gradual reexpansion of the lung. (Specific tests to determine pulmonary volume and capacities are discussed under pulmonary function tests.)Disorders of the Lungs. The air brought to the lungs is filtered, moistened, and warmed on its way along the respiratory tract but it can nevertheless bring irritants and infectious organisms, and when the body resistance is low for any reason the lungs may suffer diseases of some seriousness. Such diseases include tuberculosis and pneumonia. Other disorders of the lungs include edema" >pulmonary edema, pleurisy, asthma, bronchiectasis, atelectasis, emphysema, and pneumoconiosis. Still other diseases enter the lungs via pathogens in the circulation, and the lungs may also be affected by embolism" >pulmonary embolism and chronic obstructive pulmonary disease.

Structure of the lung. From Applegate, 2000.lung abscess an infection of the lung, characterized by a localized accumulation of pus and destruction of tissue. It may be a complication of pneumonia or tuberculosis. A lung abscess may also follow a period of excessive drinking by an alcoholic. Infected matter that has been aspirated (usually in a drunken stupor) may lodge in a bronchiole and produce inflammation. Lung cancer may also be responsible for formation of an abscess.
The first symptoms include a dry cough and chest pain. Later these may be followed by fever, chills, productive cough, headache, perspiration, foul-smelling sputum, and sometimes dyspnea. If the abscess is a complication of pneumonia, the symptoms tend to be moderated to an exaggeration of the pneumonia symptoms.
When a lung abscess forms, it is in the acute stage and treatment with antibiotics usually is effective. postural drainage may be prescribed to assist in drainage of exudate from lungs and bronchioles. In most cases, this treatment produces a cure. If the abscess becomes chronic, surgery may be necessary and usually involves removal of the portion of the lung containing the abscess.accessory lung pulmonary sequestration.bird breeder's lung pigeon breeder's lung.black lung coal workers' pneumoconiosis.brown lung byssinosis.lung cancer malignant growths of the lung. Although the exact cause of lung cancer is not known, inhaled carcinogens are known to be important predisposing causes. Cancer in the lungs may also be a metastasis of malignancy elsewhere in the body. Many years ago it was realized that miners of certain ores who inhaled the mine dust developed lung cancer much more often than workers in other occupations. Later, other carcinogens of lung tissue, such as air polluted by fumes from burning fuels or motor exhausts, were singled out as probable causes of the increasing number of cases of the disease in urban and industrial areas. The most obvious carcinogen, however, and the one most widely encountered, is tobacco smoke, especially cigarette smoke, which is much more frequently and deeply inhaled than the smoke of pipes or cigars.
A study based on autopsies of the lungs of individuals who had died from many varied causes, but whose smoking history was known, showed that unrecognized cancer and precancerous changes in tissue were numerous among smokers and rare among nonsmokers. These findings led the Surgeon General of the United States to appoint an investigative committee, which ultimately issued a report stating that “cigarette smoking is a health hazard of sufficient importance in the United States to warrant appropriate action.”
Since the factors causing lung cancer act slowly and may produce a tumor near the periphery of the lung, early symptoms are vague or may not appear at all, and nearly a third of the cases are in an advanced stage when they are discovered. The earliest and most common symptom is a cough. Dry at first, this cough later produces sputum, which eventually becomes blood-streaked. An isolated persistent wheeze in the chest is frequently a symptom and indicates a partial obstruction in a bronchus. Chest pains, weakness, and loss of weight are later symptoms, as is dyspnea.
Diagnosis depends on a careful physical examination, including a chest x-ray. If a suspicious density is seen on the x-ray, samples of sputum will be examined microscopically for the presence of malignant cells. bronchoscopy is also done, and at the same time a specimen for biopsy can be obtained or the bronchial secretions can be washed out and the cells stained and examined.
When examination indicates lung cancer, prompt treatment is essential. This may involve the surgical removal of the lobe of the lung containing the cancer or of an entire lung if the malignant cells have spread. A significant number of persons affected by lung cancer can be cured by such operations if the surgery is performed in time. In some cases of widespread involvement surgery is not possible; these patients are treated with radiation therapy and antineoplastic drugs.
Carcinogens that can trigger lung cancer must be avoided and, when possible, eliminated. Mine workers should take adequate precautions to avoid inhaling harmful dusts. Public health authorities and industry must act more effectively to control air pollution. The most important step toward protection against lung cancer is elimination of cigarette smoking. State and local units of the American Lung Association are excellent sources of information about lung disease and its prevention.
Lung cancer clinical guidelines have been published in both the United States and Canada. In Canada they are available at the web site of Cancer Care Ontario, http://www.cancercare.on.ca. and in the United States they are available at the web site of the National Guideline Clearinghouse, http://www.guideline.gov.coal miner's lung coal workers' pneumoconiosis.farmer's lung hypersensitivity pneumonitis caused by inhalation of moldy hay dust.iron lung popular name for Drinker respirator.pigeon breeder's lung hypersensitivity pneumonitis caused by inhalation of particles of bird feces, seen in those who work closely with pigeons or other birds; it may eventually result in pulmonary fibrosis.shock lung acute respiratory distress syndrome.wet lung 1. pulmonary edema.2. acute respiratory distress syndrome.

lung abscess

(lŭng), an abscess in the lung parenchyma, diagnosed as such by cavitation, bronchial communication, and replacement of some air by pus.

lung abscess

A lung infection with organisms such as Staphylococcus aureus or Klebsiella pneumoniae which has proceeded to tissue destruction, suppuration and the formation of a pus-filled cavity lined with condensed inflammatory tissue. Lung abscesses commonly rupture into a bronchus so that pus is coughed up.

单词	lung abscess
释义	lung abscess lung abscess An area of lung tissue that has broken down and become a pus-filled cavity. It is usually caused by inhalation of foreign material that gets trapped in the lung tissue, causing infection and inflammation. It causes coughing, fever, and chest pain, and can lead to blood poisoning. Treatment is usually with antibiotic drugs. EncyclopediaSeelung lung abscess Lung Abscess Definition Lung abscess is an acute or chronic infection of the lung, marked by a localized collection of pus, inflammation, and destruction of tissue. Description Lung abscess is the end result of a number of different disease processes ranging from fungal and bacterial infections to cancer. It can affect anyone at any age. Patients who are most vulnerable include those weakened by cancer and other chronic diseases; patients with a history of substance abuse, diabetes, epilepsy, or poor dental hygiene; patients who have recently had operations under anesthesia; and stroke patients. In children, the most vulnerable patients are those with weakened immune systems, malnutrition, or blunt injuries to the chest. Causes and symptoms The immediate cause of most lung abscesses is infection caused by bacteria. About 65% of these infections are produced by anaerobes, which are bacteria that do not need air or oxygen to live. The remaining cases are caused by a mixture of anaerobic and aerobic (air breathing) bacteria. When the bacteria arrive in the lung, they are engulfed or eaten by special cells called phagocytes. The phagocytes release chemicals that contribute to inflammation and eventual necrosis, or death, of a part of the lung tissue. There are several different ways that bacteria can get into the lung. Aspiration Aspiration refers to the accidental inhalation of material from the mouth or throat into the airway and lungs. It is responsible for about 50% of cases of lung abscess. The human mouth and gums contain large numbers of anaerobic bacteria; patients with periodontal disease or poor oral hygiene have higher concentrations of these organisms. Aspiration is most likely to occur in patients who are unconscious or semiconscious due to anesthesia, seizures, alcohol and drug abuse, or stroke. Patients who have problems swallowing or coughing, or who have nasogastric tubes in place are also at risk of aspiration. Bronchial obstruction The bronchi are the two branches of the windpipe that lead into the lungs. If they are blocked by tissue swelling, cancerous tumors, or foreign objects, a lung abscess may form from infection trapped behind the blockage. Spread of infection About 20% of cases of pneumonia that cause the death of lung tissue (necrotizing pneumonia) will develop into lung abscess. Lung abscess can also be caused by the spread of other infections from the liver, abdominal cavity, or open chest wounds. Rarely, AIDS patients can develop lung abscess from Pneumocystis carinii and other organisms that take advantage of a weakened immune system.Lung abscess is usually slow to develop. It may take about two weeks after aspiration or bronchial obstruction for an abscess to produce noticeable symptoms. The patient may be acutely ill for two weeks to three months. In the beginning, the symptoms of lung abscess are difficult to distinguish from those of severe pneumonia. Adults will usually have moderate fever (101-102 °F/38-39 °C), chills, chest pain, and general weakness. Children may or may not have chest pain, but usually suffer weight loss and high fevers. As the illness progresses, about 75% of patients will cough up foul or musty-smelling sputum; some also cough up blood.Lung abscess can lead to serious complications, including emphysema, spread of the abscess to other parts of the lung, hemorrhage, adult respiratory distress syndrome, rupture of the abscess, inflammation of the membrane surrounding the heart, or chronic inflammation of the lung. Diagnosis The diagnosis is made on the basis of the patient's medical history (especially recent operations under general anesthesia) and general health as well as imaging studies. Smears and cultures taken from the patient's sputum are not usually very helpful because they will be contaminated with bacteria from the mouth. The doctor will first use a bronchoscope (lighted tube inserted into the windpipe) to rule out the possibility of lung cancer. In some cases of serious infection, the doctor can use a fiberoptic bronchoscope with a protected specimen brush to take material directly from the patient's lungs, for identification of the organism. This technique is time-consuming and expensive, and requires the patient to be taken off antibiotics for 48 hours. It is usually used only to evaluate severely ill patients with weakened immune systems.In most cases, the doctor will use the results of a chest x ray to help distinguish lung abscess from empyema, cancer, tuberculosis, or cysts. In patients with lung abscess, the x ray will show a thick-walled unified clear space or cavity surrounded by solid tissue. There is often a visible air-fluid level. The doctor may also order a CT scan of the chest, in order to have a clearer picture of the exact location of the abscess.Blood tests cannot be used to make a diagnosis of lung abscess, but they can be useful in ruling out other conditions. Patients with lung abscess usually have abnormally high white blood cell counts (leukocytosis) when their blood is tested, but this condition is not unique to lung abscess. Treatment Lung abscess is treated with a combination of antibiotic drugs, oxygen therapy, and surgery. The antibiotics that are usually given for lung abscess are penicillin G, penicillin V, and clindamycin. They are given intravenously until the patient shows signs of improvement, and then continued in oral form. The patient may need to take antibiotics for a month or longer, until the chest x ray indicates that the abscess is healing. Oxygen may be given to patients who are having trouble breathing. Surgical treatment Most patients with lung abscess will not need surgery. About 5% of patients-usually those who do not respond to antibiotics or are coughing up large amounts of blood (500 mL or more)—may have emergency surgery for removal of the diseased part of the lung or for insertion of a tube to drain the abscess. Antibiotic treatment is considered to have failed if fever and other symptoms continue after 10-14 days of treatment; if chest x rays indicate that the abscess is not shrinking; or if the patient has pneumonia that is spreading to other parts of the lung. Supportive care Because lung abscess is a serious condition, patients need quiet and bed rest. Hospital care usually includes increasing the patient's fluid intake to loosen up the secretions in the lungs, and physical therapy to strengthen the patient's breathing muscles. Follow-up Patients with lung abscess need careful follow-up care after the acute infection subsides. Follow-up usually includes a series of chest x rays to make sure that the infection has cleared up. Treatment with antibiotics may continue for as long as four months, to prevent recurrence. Prognosis About 95% of lung abscess patients can be treated successfully with antibiotics alone. Patients who need surgical treatment have a mortality rate of 10-15%. Prevention Some of the conditions that make people more vulnerable to lung abscess concern long-term lifestyle behaviors, such as substance abuse and lack of dental care. Others, however, are connected with chronic illness and hospitalization. Aspiration can be prevented with proper care of unconscious patients, which includes suctioning of throat secretions and positioning patients to promote drainage. Patients who are conscious can be given physical therapy to help them cough up material in their lungs and airways. Patients with weakened immune systems can be isolated from patients with pneumonia or fungal infections. Resources Books Stauffer, John L. "Lung." In Current Medical Diagnosis and Treatment, 1998, edited by Stephen McPhee, et al., 37th ed. Stamford: Appleton & Lange, 1997. Key terms Abscess — An area of injured body tissue that fills with pus, as in lung abscess.Anaerobe — A type of bacterium that does not require air or oxygen to live. Anaerobic bacteria are frequent causes of lung abscess.Aspiration — Inhalation of fluid or foreign bodies into the airway or lungs. Aspiration often happens after vomiting.Bronchoscope — A lighted, flexible tube inserted into the windpipe to view the bronchi or withdraw fluid samples for testing. Bronchoscopy with a protected brush can be used in the diagnosis of lung abscess in severely ill patients.Bronchus — One of the two large tubes connecting the windpipe and the lungs.Leukocytosis — An increased level of white cells in the blood. Leukocytosis is a common reaction to infections, including lung abscess.Necrotizing pneumonia — Pneumonia that causes the death of lung tissue. It often precedes the development of lung abscess.Sputum — The substance that is brought up from the lungs and airway when a person coughs or spits. It is usually a mixture of saliva and mucus, but may contain blood or pus in patients with lung abscess or other diseases of the lungs. lung [lung] either of two large organs lying within the chest cavity on either side of the heart; they supply the blood with oxygen inhaled from the outside air and dispose of waste carbon dioxide in the exhaled air, as a part of the process known as respiration. Other functions include filtration of blood, serving as reservoirs to store blood, and playing a role in metabolic activities. See also color plates. The lungs are made of elastic tissue filled with interlacing networks of tubes and sacs carrying air, and with blood vessels carrying blood. The bronchi" >bronchi, which bring air to the lungs, branch out within the lungs into many smaller tubes, the bronchioles" >bronchioles, which culminate in clusters of tiny air sacs called alveoli" >alveoli, whose total runs into millions. The alveoli are surrounded by a network of capillaries. Through the thin membranes of the capillaries, the air and blood make their exchange of oxygen and carbon dioxide. The lungs are divided into lobes, the left lung having two (the left upper lobe and the left lower lobe) and the right having three (the right upper lobe, the right middle lobe, and the right lower lobe); these are further subdivided into bronchopulmonary segments, of which there are about 20. Protecting each lung is the pleura, a two-layered membrane that envelops the lung and contains lubricating fluid between its inner and outer layers.Mechanics of Inflation and Deflation. The lungs are inflated by action of the diaphragm and the intercostal muscles. The diaphragm, a large dome-shaped muscle, forms the bottom of the thoracic cage. As it contracts it flattens, increasing the diameter of the thorax and elevating the lower ribs. Both of these actions increase the space for expansion of the lungs. The external intercostal muscles provide flexibility to the thoracic cage and allow more room for lung expansion by elevating the anterior end of each rib, thereby increasing the anterior-posterior diameter of the chest wall. Deflation of the lungs is chiefly a passive maneuver. The major muscles involved in exhalation are the abdominal muscle group. As these muscles contract, they depress the lower ribs, and, through an increase in abdominal pressure, move the diaphragm upward. As the lungs are compressed and distended by the respiratory muscles, the pressure within the alveoli (intra-alveolar pressure) rises and falls. During inhalation the pressure becomes slightly negative (−3 mm Hg) in relation to atmospheric pressure. During exhalation the intra-alveolar pressure rises to approximately +3 mm Hg. The effect of negative pressure within the alveoli is to cause air under atmospheric pressure to flow into the lungs (inhalation). The condition of positive pressure creates the opposite effect, causing air to flow outward (exhalation). The lungs are surrounded by an airtight compartment, the pleural space within the pleural membrane. The intrapleural pressure is less than atmospheric pressure and is expressed as negative pressure. Normally the intrapleural pressure is about −4 mm Hg. When the lungs are fully expanded this pressure may be as great as −9 mm Hg. Under normal conditions, however, the intrapleural pressure fluctuates between −4 and −6 mm Hg. If anything should penetrate the walls of the pleura, the negative pressure is lost as air rushes into the pleural cavity in response to atmospheric pressure. This condition is called pneumothorax. The walls of the alveoli also must remain intact in order to maintain normal intrapleural pressure. If a lesion causes a break in the alveolar membranes, air enters the pleural cavity through the break and produces pneumothorax. Relief of pneumothorax and collapse of the lung from accumulations of either air or fluids within the pleural space may be provided by aspiration of the air or fluid from the thoracic cavity (thoracentesis) or by insertion of chest tubes to provide for a gradual reexpansion of the lung. (Specific tests to determine pulmonary volume and capacities are discussed under pulmonary function tests.)Disorders of the Lungs. The air brought to the lungs is filtered, moistened, and warmed on its way along the respiratory tract but it can nevertheless bring irritants and infectious organisms, and when the body resistance is low for any reason the lungs may suffer diseases of some seriousness. Such diseases include tuberculosis and pneumonia. Other disorders of the lungs include edema" >pulmonary edema, pleurisy, asthma, bronchiectasis, atelectasis, emphysema, and pneumoconiosis. Still other diseases enter the lungs via pathogens in the circulation, and the lungs may also be affected by embolism" >pulmonary embolism and chronic obstructive pulmonary disease.Structure of the lung. From Applegate, 2000.lung abscess an infection of the lung, characterized by a localized accumulation of pus and destruction of tissue. It may be a complication of pneumonia or tuberculosis. A lung abscess may also follow a period of excessive drinking by an alcoholic. Infected matter that has been aspirated (usually in a drunken stupor) may lodge in a bronchiole and produce inflammation. Lung cancer may also be responsible for formation of an abscess. The first symptoms include a dry cough and chest pain. Later these may be followed by fever, chills, productive cough, headache, perspiration, foul-smelling sputum, and sometimes dyspnea. If the abscess is a complication of pneumonia, the symptoms tend to be moderated to an exaggeration of the pneumonia symptoms. When a lung abscess forms, it is in the acute stage and treatment with antibiotics usually is effective. postural drainage may be prescribed to assist in drainage of exudate from lungs and bronchioles. In most cases, this treatment produces a cure. If the abscess becomes chronic, surgery may be necessary and usually involves removal of the portion of the lung containing the abscess.accessory lung pulmonary sequestration.bird breeder's lung pigeon breeder's lung.black lung coal workers' pneumoconiosis.brown lung byssinosis.lung cancer malignant growths of the lung. Although the exact cause of lung cancer is not known, inhaled carcinogens are known to be important predisposing causes. Cancer in the lungs may also be a metastasis of malignancy elsewhere in the body. Many years ago it was realized that miners of certain ores who inhaled the mine dust developed lung cancer much more often than workers in other occupations. Later, other carcinogens of lung tissue, such as air polluted by fumes from burning fuels or motor exhausts, were singled out as probable causes of the increasing number of cases of the disease in urban and industrial areas. The most obvious carcinogen, however, and the one most widely encountered, is tobacco smoke, especially cigarette smoke, which is much more frequently and deeply inhaled than the smoke of pipes or cigars. A study based on autopsies of the lungs of individuals who had died from many varied causes, but whose smoking history was known, showed that unrecognized cancer and precancerous changes in tissue were numerous among smokers and rare among nonsmokers. These findings led the Surgeon General of the United States to appoint an investigative committee, which ultimately issued a report stating that “cigarette smoking is a health hazard of sufficient importance in the United States to warrant appropriate action.” Since the factors causing lung cancer act slowly and may produce a tumor near the periphery of the lung, early symptoms are vague or may not appear at all, and nearly a third of the cases are in an advanced stage when they are discovered. The earliest and most common symptom is a cough. Dry at first, this cough later produces sputum, which eventually becomes blood-streaked. An isolated persistent wheeze in the chest is frequently a symptom and indicates a partial obstruction in a bronchus. Chest pains, weakness, and loss of weight are later symptoms, as is dyspnea. Diagnosis depends on a careful physical examination, including a chest x-ray. If a suspicious density is seen on the x-ray, samples of sputum will be examined microscopically for the presence of malignant cells. bronchoscopy is also done, and at the same time a specimen for biopsy can be obtained or the bronchial secretions can be washed out and the cells stained and examined. When examination indicates lung cancer, prompt treatment is essential. This may involve the surgical removal of the lobe of the lung containing the cancer or of an entire lung if the malignant cells have spread. A significant number of persons affected by lung cancer can be cured by such operations if the surgery is performed in time. In some cases of widespread involvement surgery is not possible; these patients are treated with radiation therapy and antineoplastic drugs. Carcinogens that can trigger lung cancer must be avoided and, when possible, eliminated. Mine workers should take adequate precautions to avoid inhaling harmful dusts. Public health authorities and industry must act more effectively to control air pollution. The most important step toward protection against lung cancer is elimination of cigarette smoking. State and local units of the American Lung Association are excellent sources of information about lung disease and its prevention. Lung cancer clinical guidelines have been published in both the United States and Canada. In Canada they are available at the web site of Cancer Care Ontario, http://www.cancercare.on.ca. and in the United States they are available at the web site of the National Guideline Clearinghouse, http://www.guideline.gov.coal miner's lung coal workers' pneumoconiosis.farmer's lung hypersensitivity pneumonitis caused by inhalation of moldy hay dust.iron lung popular name for Drinker respirator.pigeon breeder's lung hypersensitivity pneumonitis caused by inhalation of particles of bird feces, seen in those who work closely with pigeons or other birds; it may eventually result in pulmonary fibrosis.shock lung acute respiratory distress syndrome.wet lung 1. pulmonary edema.2. acute respiratory distress syndrome. lung abscess (lŭng), an abscess in the lung parenchyma, diagnosed as such by cavitation, bronchial communication, and replacement of some air by pus. lung abscess A lung infection with organisms such as Staphylococcus aureus or Klebsiella pneumoniae which has proceeded to tissue destruction, suppuration and the formation of a pus-filled cavity lined with condensed inflammatory tissue. Lung abscesses commonly rupture into a bronchus so that pus is coughed up.
随便看	battalion leadership team battalion level differential model battalion level indirect fire system battalion-level training battalion level training model battalion logistics control point battalion maintenance office battalion maintenance officer battalion maintenance supervisor battalion maintenance technician battalion mentorship program battalion military liaison battalion mobile production center battalion mortar & davy crockett platoon battalion motor officer battalion motor sergeant battalion nuclear warfare battalion officer of the watch battalion operation center battalion orderly officer battalion orderly room battalion orderly sergeant battalion orderly warrant battalion personnel administration center battalion quartermaster sergeant