Respiratory System PDF

RESPIRATORY SYSTEM PROF. RAFAEL DE JESUS, RXT, RRT, RPO  The major role of the respiratory system is the oxygenation of blood and the removal of waste products of the body in the form of carbon dioxide.  The trachea, bronchi, and bronchioles are tubular structures responsible for conductin...

RESPIRATORY SYSTEM PROF. RAFAEL DE JESUS, RXT, RRT, RPO  The major role of the respiratory system is the oxygenation of blood and the removal of waste products of the body in the form of carbon dioxide.  The trachea, bronchi, and bronchioles are tubular structures responsible for conducting air from outside of the body into the lungs.  The single trachea branches out into two bronchi and then on to progressively smaller bronchioles to produce a structure termed the “bronchial tree”.  The tracheobronchial tree is lined with a mucous membrane containing numerous hairlike projections called “cilia”. The cilia act as miniature sweepers to prevent dust and foreign particles from reaching the lungs.  The vital gas exchange within the lungs within the alveoli, extremely thin-walled sacs surrounded by blood capillaries, which represents the true parenchyma of the lung.  Oxygen in the inhaled air diffuses from the alveoli into the blood capillaries, where it attaches to hemoglobin molecules in red blood cells and is carried to the various tissues of the body.  Respiration is controlled by a center in the medulla at the base of the brain. The respiratory center is regulated by the level of carbon dioxide in the blood. Even a slight increase in the amount of carbon dioxide in the blood increases the rate and depth of breathing, as when an individual exercise  The accumulation of waste gases that must be removed from the body (as well as the body's need for additional oxygen) causes the respiratory center to stimulate the muscles of respiration--the diaphragm and the intercostal muscles between the ribs.  The lungs are encased by a double membrane consisting of two layers of pleura. The visceral pleura covers the lung, and the parietal pleura lines the inner chest wall (thoracic cavity). INFLAMMATORY DISORDERS PNEUMONIA Acute pneumonia is a form of acute respiratory in infection of the lung that can be caused by a variety of organisms, most commonly bacteria and viruses. Regardless of the cause, pneumonias tend to produce one of three basic radiographic patterns. ALVEOLAR or AIR-SPACE PNEUMONIA Exemplified by pneumococcal pneumonia, is produced by an organism that causes an inflammatory exudate that replaces air in the alveoli so that the affected part of the lung is no longer air containing but rather appears solid. The inflammation spreads from one alveolus to the next by way of communicating channels and may involve a whole lobe or even the entire lung. BRONCHOPNEUMONIA Bronchopneumonia, typified by staphylococcal infection, is primarily an inflammation that originates in the airways and spreads to adjacent alveoli Because alveolar spread in the peripheral air spaces is minimal, the inflammation tends to produce small patches of consolidation that may be seen throughout the lungs but are separated by an abundance of air containing lung tissue. Bronchial inflammation causing airway obstruction, leads to atelectasis with loss of lung volume; air bronchograms are absent. INTERSTITIAL PNEUMONIA It is most commonly produced by viral mycoplasmal infections. In this type of pneumonia the inflammatory process predominantly involves walls of the alveoli and the interstitial supporting structures of the lungs, producing an non linear or reticular pattern. ASPIRATION PNEUMONIA The aspiration of esophageal or gastric contents into the lung can lead to the development of pneumonia. Aspiration of esophageal material can occur in patients with esophageal obstruction (tumor, stricture, achalasia), diverticula (Zenker's), or neuromuscular disturbances in swallowing. Aspiration of liquid gastric contents is most often related to general anesthesia, tracheostomy, coma, or trauma. Both types of aspiration cause multiple alveolar densities, which may be distributed widely and diffusely throughout both lungs. LUNG ABSCESS Lung abscess is a necrotic area of pulmonary parenchyma containing purulent (puslike) material. A lung abscess may be a complication of bacterial pneumonia, bronchial obstruction, aspiration, a foreign body, or the hematogenous spread of organisms to the lungs either in a patient with diffuse bacteremia or as a result of septic emboli. The earliest radiographic finding of lung abscess is a spherical density that characteristically has a dense center with a hazy, poorly defined periphery. TUBERCOLOSIS Tuberculosis is caused by Mycobacterium tuberculosis, a rod-shaped bacterium with a protective waxy coat that permits it to live outside the body for a long time. Tuberculosis spreads mainly by droplets in the air, which are produced in huge numbers by the coughing of an infected patient. Therefore it is essential that respiratory precautions be followed when radiographing patients with active disease. The organisms may be inhaled from sputum that has dried and been changed into dust. They are rapidly killed by direct sunlight but may survive a long time in the dark. PRIMARY TUBERCOLOSIS Primary pulmonary tuberculosis has traditionally been considered a disease of children and young adults. However with the dramatic decrease in the prevalence of tuberculosis (especially in children and young adults), primary pulmonary disease call develop at any age. There are four basic radiographic patterns of primary pulmonary tubercolosis.  The infiltrate may be seen as a lobar or segmental air-space consolidation that is usually homogenous, dense and well defined.  Associated enlargement of hilar and mediastinal lymph nodes without discreet parenchymal infiltrate.  Combination of a focal parenchymal lesion and enlarged hilar and mediastinal nodes produces the classic primary complex, an appearance strongly suggestive of primary tuberculosis. Pleural effusion is common, especially in adults.  Miliary tuberculosis refers to dissemination of the disease by way of the blood-stream. Radiographically, this produces innumerable fine discrete nodules distributed uniformly throughout the lungs. SECONDARY TUBERCOLOSIS Reactivation of organisms from previously dormant tubercles is termed a "secondary lesion." At times, the tuberculosis bacillus may remain inactive for may years before a secondary lesion develops, often because of a decrease in the body's immune defense. TUBERCOLOMA A tuberculoma is a sharply circumscribed parenchymal nodule, often containing viable tuberculosis bacilli, that can develop in either primary or secondary disease. Although the residual localized caseation may remain unchanged for a long period or permanently, a tuberculoma is potentially dangerous because it may break down at any time and lead to dissemination of the disease. Radiographically, tuberculomas appear as single or multiple pulmonary nodules, usually 1 to 3 cm in diameter. They can occur in any part of the lung but are most common in the periphery and in the upper lobes. HISTOPLASMOSIS Caused by the fungus Histoplasma capsulatum, is a common disease that often produces a radiographic appearance simulating that of tuberculosis. The primary form of histoplasmosis is usually relatively benign and often passes unnoticed. Chest radiographs may demonstrate single or multiple areas of pulmonary infiltration that are most often in the lower lung and are frequently associated with hilar lymph node enlargement. BRONCHIECTASIS Bronchiectasis refers to permanent abnormal dilation of one or more large bronchi as a result destruction of the elastic and muscular component of the bronchial wall. The origin of the destructive process is nearly always a bacterial infection, which may either be a severe necrotizing pneumonia or result of a local or systemic abnormality that impair the bod's defense mechanisms and promotes bac the a growth. Since the advent of antibiotic therapy, the incidence of bronchiectasis has substantially decreased. CROUP Croup is primarily a viral infection of young children that produces inflammatory obstructive swelling localized to the subglottic portion of the trachea. EPIGLOTTITIS Epiglottitis is an inflammatory condition of the epiglottis and/or nearby structures including the arytenoids, aryepiglottic folds, and vallecula. Epiglottitis is a life-threatening infection that causes profound swelling of the upper airways which can lead to asphyxia and respiratory arrest. DIFFUSE LUNG DISEASE CHRONIC OBSTRUCTIVE PULMONARY DISEASE Chronic obstructive pulmonary disease (COPD) includes several conditions in which chronic obstruction of the airways leads to an ineffective exchange of respiratory gases and difficulty breathing. COPD NORMAL CHRONIC BRONCHITIS Chronic inflammation of the bronchi leads to severe coughing with the production of sputum. Bronchitis may be a complication of respiratory infection or be the result of long-term exposure to air pollution of cigarette smoking. EMPHYSEMA Emphysema is a crippling and debilitating condition in which obstructive and destructive changes in small airways lead to a dramatic increase in the volume of air in the lungs. In many patients, the development of emphysema is closely associated with heavy cigarette smoking. Other predisposing factors are chronic bronchitis, air pollution, and long-term exposure to irritants of respiratory tract. ASTHMA Asthma is a very common disease in which widespread narrowing of the airways develops because of an increased responsiveness of the tracheobronchial tree to various substances (allergens). Common allergens include house dust, pollen, molds, animal dander, certain fabrics, and various foods. The hypersensitivity reaction to one or more of these allergens leads to swelling of the mucous membranes of the bronchi, excess secretion of mucus, and spasm of the smooth muscle in the bronchial walls, all of which lead to severe narrowing of the airways. This makes breathing (especially expiration) difficult and results in the characteristic wheezing sound that is produced by air passing through the narrowed bronchial tubes. PNEUMOCONIOSIS Prolonged occupational exposure to certain irritating dusts can cause severe pulmonary disease and a spectrum of radiographic findings. These inhaled dusts cause a chronic interstitial inflammation that leads to pulmonary fibrosis and a diffuse nonspecific radiographic pattern of linear streaks and nodules throughout the lungs. The most common of the pneumoconioses are silicosis, asbestosis, and coal worker's disease. Other causes include exposure to such dusts as tin, iron oxide, barium, and beryllium. SILICOSIS The inhalation of high concentrations of silicon dioxide primarily affects workers engaged in mining, foundry work, and sandblasting. Although acute silicosis can develop within 10 months of exposure in workers exposed to sandblasting in confined spaces, 15 to 20 years of long-term, relatively less intense exposure is required to produce radiographic changes. ASBESTOSIS Asbestosis may develop in improperly protected workers engaged in the manufacture of asbestos or in those handling building materials or insulation that is composed of asbestos. The radiographic hallmark of asbestosis is involvement of the pleura. Initially, pleural thickening appears as linear plaques of opacification, which are most often along the lower chest wall and diaphragm. COAL WORKER'S PNEUMOCONIOSIS Coal miners, especially those working with anthracite (hard coal), are susceptible to developing pneumoconiosis by inhaling high concentrations of coal dust. Initially, multiple small, irregular opacities produce a reticular pattern similar to that of silicosis. However, the nodules tend to be somewhat less well defined than those of silicosis and are of a granular density, unlike the homogeneous density of silicosis nodules. With advanced discase, the pattern of progressive massive fibrosis can develop. VASCULAR DISEASE PULMONARY EMBOLISM Pulmonary embolism is a potentially fatal condition that is by far the most common pathologic process involving the lungs of hospitalized patients. In about 80% of patients with this disorder, the condition does not cause symptoms and is thus unrecognized because the emboli are too small or too few to occlude blood flow to a substantial portion of the lung. Even when symptomatic, pulmonary embolism may be difficult to diagnose. More than 95% of pulmonary emboli arise from thrombi that develop in the deep venous system of the lower extremities because of venous stasis SEPTIC EMBOLISM Septic embolism refers to a shower of bacteria that enter the pulmonary circulation and are trapped within the lung. Septic emboli primarily arise from either the heart (bacterial endocarditis) or the peripheral veins (septic thrombophlebitis). Many patients have a history of intravenous drug abuse. Septic emboli are almost always multiple and appear radiographically as ill-defined, round or wedge shaped opacities in the periphery of the lung. PULMONARY ARTERIOVENOUS FISTULA Pulmonary arteriovenous fistula is an abnormal vascular communication from a pulmonary artery to a pulmonary vein. Pulmonary arteriovenous fistulas are multiple in about one third of patients; up to two thirds of patients with these pulmonary malformations have similar arteriovenous communications elsewhere (hereditary hemorrhagic telangiectasia  NEOPLASM BRONCHIAL ADENOMA Bronchial adenomas are neoplasms of low-grade malignancy that constitute about 1% off all bronchial neoplasms. They are at least as common in women as in men and are found in a younger age group than bronchogenic carcinoma. Hemoptysis and recurring pneumonia are the most common symptoms. BRONCHOGENIC CARCINOMA Primary carcinoma of the lung arises from the mucosa of the bronchial tree. Although the precise cause is unknown, bronchogenic carcinoma is closely linked to smoking and to the inhalation of cancer causing agents (carcinogens) such as air pollution, exhaust gases, and industrial fumes. Bronchogenic carcinoma produces a broad spectrum of radiographic abnormalities that depend on the site of the tumor and its relation to the bronchial tree. The tumor may appear as a discrete mass or be undetectable and identified only by virtue of secondary post obstructive changes caused by tumor within or compressing the bronchus. PULMONARY METASTASES Up to one third of patients with cancer develop pulmonary metastases; in about half of these patients, the only demonstrable metastases are confined to the lungs. Pulmonary metastases may develop from hematogenous or lymphatic spread most commonly from musculoskeletal sarcomas, myeloma, and carcinomas of the breast, urogenital tract, thyroid, and colon. MISCELLANEOUS LUNG DISORDERS ATELECTASIS Atelectasis refers to a condition in which there is diminished air within the lung associated with reduced lung volume. It is most commonly the result of bronchial obstruction, which may be attributable to a neoplasm, foreign body (peanut, coin, or tooth), or mucus plug. CYSTIC FIBROSIS Cystic fibrosis (mucoviscidosis) is a hereditary disease characterized by the secretion of excessively viscous mucus by all the exocrine glands. In the lungs, thick mucus secreted by the trachea and bronchi blocks the air passages and leads to focal areas of lung collapse. Recurrent pulmonary infections are common, since bacteria that are normally carried away by mucosal secretions adhere to the sticky mucus produced in this condition. HYALINE MEMBRANE DISEASE Hyaline membrane disease is one of the most common causes of respiratory distress in the newborn. It primarily occurs in premature infants, especially those who have diabetic mothers or who have been delivered by cesarean section. Hypoxia and increasing respiratory distress may not be immediately evident at birth but almost always appear within 6 hours of delivery. ADULT RESPIRATORY DISTRESS SYNDROME The term adult respiratory distress syndrome (ARDS) is used to describe a clinical picture of severe, unexpected, and life-threatening acute respiratory distress that develops in patients who have a variety of medical and surgical disorders but no major underlying lung disease. It occurs most commonly in patients with nonthoracic trauma who develop hypotension and shock and thus is often called "shock lung." INTRABRONCHIAL FOREIGN BODIES The aspiration of solid foreign bodies into the tracheobronchial tree occurs almost exclusively in young children. Although some foreign bodies are radiopaque and easily detected on plain chest radiographs, most aspirated foreign bodies are non opaque and can be diagnosed only by observation of secondary signs in the lungs caused by partial or complete bronchial obstruction. The lower lobes are almost always involved, the right more often than the left. MEDIASTINAL EMPHYSEMA (PNEUMOMEDIASTINUM) Air within the mediastinal space may appear spontaneously or be the result of chest trauma; perforation of the esophagus or tracheobronchial tree; or the spread of air along fascial planes from the neck, peritoneal cavity, or retroperitoneal space. Spontaneous pneumomediastinum usually results from a sudden rise in intra-alveolar pressure (e.g., severe coughing, vomiting, or straining) that causes alveolar rupture and the dissection of air along blood vessels in the interstitial space to the hilum and mediastinum. SUBCUTANEOUS EMPHYSEMA Subcutaneous emphysema is caused by penetrating or blunt injuries that disrupt the lung and parietal pleura so that air is forced into the tissues of the chest wall. The resulting radiographic appearance is bizarre, with streaks of lucency outlining muscle bundles.  DISORDERS OF THE PLEURA PNEUMOTHORAX Pneumothorax refers to the presence of air in the pleural cavity that results in a partial or complete collapse of the lung. It most commonly results from rupture of a subpleural bulla, either as a complication of emphysema or as a spontaneous event in an otherwise healthy young adult. Other causes of pneumothorax include trauma (stabbing, gunshot, or fractured rib), iatrogenic causes (after lung biopsy or the introduction of a chest tube for thoracentesis), and as a complication of neonatal hyaline membrane disease requiring prolonged assisted ventilation. PLEURAL EFFUSION The accumulation of fluid in the pleural space is a nonspecific finding that may be caused by a wide variety of pathologic processes. The most common causes include congestive heart failure, pulmonary embolism, infection (especially tuberculosis), pleurisy, neoplastic disease, and connective tissue disorders. Pleural effusion also can be the result of abdominal disease, such as recent surgery, ascites, subphrenic abscess, and pancreatitis. EMPYEMA Empyema refers to the presence of infected liquid or frank pus in the pleural space. Usually the result of the spread of an adjacent infection (bacterial pneumonia, subdiaphragmatic abscess, lung abscess, esophageal perforation), empyemas may also occur after thoracic surgery, trauma, or instrumentation of the pleural space. Since the development of antibiotics, empyemas are rare.   MEDIASTINAL MASSES Because various types of mediastinal masses tend to occur predominantly in specific locations, the mediastinum is often divided into anterior, middle, and posterior compartments. The anterior compartment extends from the sternum back to the trachea and the anterior border of the heart. The middle mediastinum contains the heart and great vessels, the central tracheobronchial tree and lymph nodes, and the phrenic nerves. The posterior compartment is composed of the space behind the pericardium.  DISORDERS OF THE DIAPHRAGM The diaphragm is the major muscle of respiration that separates the thoracic and abdominal cavities. Radiographically, the height of the diaphragm varies considerably with the phase of respiration. On full inspiration, the diaphragm is usually about the level of the tenth posterior intercostal space. On expiration, it may appear two or three intercostal spaces higher. The average range of diaphragmatic motion with respiration is 3 to 6 cm, but in patients with emphysema this may be substantially reduced. The level of the diaphragm falls as the patient moves from a supine to an upright position. In an erect patient, the dome of the diaphragm tends to be about half an interspace higher on the right than on the left. However, in about 10% of normal individuals the hemidiaphragms are at the same height, or the left is higher than the right. DIAPHRAGMATIC PARALYSIS Elevation of one or both leaves of the diaphragm can be caused by paralysis resulting from any process that interferes with the normal function of the phrenic nerve. This paralysis may be attributable to accidental surgical transection of the phrenic nerve, involvement of the nerve by primary bronchogenic carcinoma or metastatic malignancy in the mediastinum or a variety of intrinsic neurologic diseases. EVENTRATION OF THE DIAPHRAGM Eventration of the diaphragm is a rare congenital abnormality in which one hemidiaphragm (very rarely both) is poorly developed and is too weak to permit the upward movement of abdominal contents into the thoracic cage. This leads to the radio-graphic appearance of a localized bulging or generalized elevation of the diaphragm.The condition is usually asymptomatic and is most common on the left. An eventration must be distinguished from a diaphragmatic hernia, through which abdominal contents are displaced into the chest. 