Chapter 3: The Respiratory System
Key Terms and Concepts
Alveoli: The functioning unit of the respiratory system
Asthma: A common disorder that begins in childhood. There is secretion and edema of the
bronchial mucosa and bronchiolar muscle spasm. This narrows the lumen of the bronchi and
traps air in the alveoli. The overall appearance of the lungs will show as opacity of the lung field
because of the increased mucus
Atelectasis: The collapse of a lung or a portion of it. It is not a disease but rather a condition of
some other pathology. Since there is no air in the lung, it will be radiodense because the walls are
opposed to each other
Bronchitis: A condition in which excessive mucus is secreted in the bronchi. The chest image
reveals hyperinflation and increased vascular markings, especially in the lower lungs
Bronchiectasis: Chronic dilation of smaller bronchi or bronchioles of the lung. The patient will
have a chronic productive cough. This is diagnosed best through bronchoscopy
Bronchogenic carcinoma: Malignant neoplasm that arises from the major bronchus of one or
both lungs. It will eventually narrow and obstruct the lumen of the bronchus. The chest
radiographic image will show a rounded opacity without calcification in the lung. This nodule is
known as a “coin” lesion
Chronic obstructive pulmonary disease: A disease in which the lungs have difficulty expelling
carbon dioxide. Since all the space in the lungs is taken up by carbon dioxide, there is no room
for the fresh oxygen
Croup: A viral infection occurring in very young children. Labored breathing and a sharp, harsh
cough are characteristic. Soft-tissue neck radiographs will show the characteristic smooth,
tapered, narrowing of the subglottic airway
Cystic fibrosis: An inherited disease of the exocrine glands involving the lungs, pancreas, and
sweat glands. It affects more than 30,000 children and young adults in the United States. Heavy
secretions of abnormally thick mucus clog the bronchi and bronchioles, leading to frequent and
progressive pulmonary infections. The radiographic image shows hyperinflation and
consolidation in the middle and upper lungs
Emphysema: Common chronic lung disease and part of a process known as COPD. It is
characterized by increased air spaces and tissue destruction leading to hypoxia. This condition
causes dyspnea. The patient will have a barrel chest and low diaphragms. Since air is trapped in
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the over-distended air spaces of the lungs, the radiographer must decrease the technical factors so
as not to overexpose the radiograph
Hamartoma: The most common solitary benign pulmonary nodule. It is an unorganized tissue
mass found in the lung periphery. The characteristic “popcorn” appearance may be seen on a
radiographic image but the HRCT will be best to diagnose it
Perfusion: Blood flow through a tissue that allows an exchange of gas. See ventilation–perfusion
scan
Pleural effusion: Fluid in the pleural cavity. Congestive heart failure is the most common cause
of bilateral or right-sided pleural effusion. A lateral chest radiograph shows fluid accumulated in
the posterior costophrenic angles. On the PA radiograph, the fluid is seen in the sulcus. The
opacity “blunts” the normally sharp costophrenic angles by displaying an upper concavity known
as the “meniscus” sign
Pneumoconiosis: A chronic interstitial pneumonia caused by irritation of certain dusts
encountered in industrial occupations. Silicosis, asbestosis, and coal workers pneumoconiosis.
Silicosis and asbestosis will have the characteristic “eggshell” appearance on the radiograph.
Asbestosis involves the pleura as well as the lungs
Pneumonia: An inflammation of the lungs. The lungs are filled with fluid causing opacity on the
image; therefore, the technologist should increase the technical factors to penetrate the lungs.
There are various types of pneumonia, aspiration, bronchopneumonia, lobar, and viral.
Pneumothorax: Air in the pleural cavity. An upright expiration chest radiograph will show a
lung that is collapsed, demonstrating the “lung edge.” There will be no lung markings seen in the
area of the pneumothorax. An expiration chest film is best to demonstrate a pneumothorax
Pulmonary edema: Excess fluid within the lung. It usually occurs from left ventricular failure,
causing a backup of blood in the lungs. There is a diffuse increase in density of the hilar regions
Pulmonary emboli: The most common pulmonary complication of hospitalized patients. Most
pulmonary emboli result in no abnormalities on the chest image. The appearance of an infiltrate
is usually delayed by 8 to 12 hours after the embolus has occurred. The involvement almost
always occurs in the lower lung zones, especially the costophrenic angles. The radiographic
appearance of an inverted wedge-shaped area of opacity is suggestive of a pulmonary infarct
Respiratory distress syndrome (RDS) (ARDS, adult RDS): Also known as hyaline membrane
disease. In premature infants, there is a deficiency in surfactant that coats the alveoli. This makes
inhalation difficult. Chest radiography will show increased density throughout the lung in a
granular pattern and a well-defined “air bronchogram” sign
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Respiratory syncytial virus (RSV): This type of virus causes a type of viral pneumonia in
children under the age of 3. It can cause atelectasis of the lungs. It is contagious
Tuberculosis: A disease caused by Mycobacterium tuberculosis. It is spread through inhalation
of infected material from someone who already has TB. Primary TB and reactivation TB occur
in different places of the lungs. In both types, apical-lordotic chest views and CT are helpful in
demonstrating the cavitations and calcifications of the lesion
Ventilation: Movement of gas into and out of the lungs. The act of respiration
Ventilation–perfusion scan: A lung function nuclear medicine test useful in the diagnosis of
pulmonary embolism. The isotope is inhaled for ventilation (air) and injected in perfusion
(blood)
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