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  • Respiratory Disorders
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What are lung diseases?

Lung diseases are conditions that keep the lungs from working properly. Lung diseases may affect one or more of the following:

  • The airways through which oxygen and other gases enter and leave the lungs
  • The tissues and structures that allow the efficient uptake of oxygen and removal of carbon dioxide (e.g., the alveoli, the tiny air sacs within the lungs)
  • The muscles and bones in the chest, the nerves in the chest and lungs, or the two thin layers of tissue (pleura) that protect and cushion the lungs
  • The blood vessels (arteries and veins) that carry blood into and out of the lungs

About Lung Diseases

Overview of the Lungs

The lungs are part of the respiratory (breathing) system and are located in the chest, inside the rib cage and above the diaphragm (a muscle that assists with breathing). Lungs are complex organs that consist of spongy, elastic tissue equipped with structures that fill our blood with fresh oxygen while removing carbon dioxide.

Air (containing oxygen) enters the lungs when we inhale a breath. It is distributed throughout the lungs by a system called the bronchial tree, with branches of decreasing diameter (called bronchi and bronchioles). The bronchial tree carries air to small sacs (alveoli) deep within the lungs, where oxygen from air moves from the lung into the bloodstream, and carbon dioxide, a byproduct of metabolism, moves from the blood into the lung to be exhaled. The intake of oxygen and its delivery to the body’s tissues by the blood is necessary for all the cells in our body to function. The removal of carbon dioxide is necessary to maintain the blood’s pH at an appropriate level, which is part of the body’s acid-base balance system.

Since the air we breathe contains many components from the environment, such as dust, pollens, bacteriavirusesfungi, smoke, and harmful chemicals, the lungs maintain a system of defense against these potentially toxic invaders. The lungs’ defense system includes immune cells, immunoglobin A (IgA), and the production of mucus to contain and remove this unwanted foreign matter from the lungs.

Examples of Common Lung Diseases

A wide range of conditions can affect the lungs and their ability to work properly. Below are some common examples.

Asthma is a chronic lung disease marked by inflammation of the bronchi and bronchioles, thickened mucus, bronchoconstriction, and episodes of airway blockage.

  • People with asthma may be sensitive to a variety of substances that do not cause the same reaction in other people. Episodes may be triggered by cold air, exercise, cigarette smoke, or other particles in the air such as dust, mold, or allergens. The triggers for each person may be different.
  • During an attack, the lining of the airways swells and the muscles surrounding the bronchi contract, causing the airways to narrow.
  • Mucus secretion can further block the flow of air, making breathing difficult and causing the affected person to wheeze.
  • Most episodes do not cause permanent lung damage, but they often require immediate medical attention since lack of oxygen and build-up of carbon dioxide can be life-threatening.
  • According to the American Lung Association, asthma is the most common chronic disorder in childhood. The number of people with asthma continues to grow with about 26 million Americans currently affected. It is estimated that 6.1 million children younger than age 18 in the U.S. have asthma.

Chronic obstructive pulmonary disease (COPD) is a term used for both emphysema and chronic bronchitis.

  • With chronic bronchitis, the bronchial tubes become inflamed and scarred and become clogged with thick mucus.
  • With emphysema, the air sacs (alveoli) in the lungs are slowly destroyed.
  • With both disorders, those affected experience increasing difficulty exhaling and getting enough oxygen.
  • Smoking is the biggest risk factor for COPD. Smoking causes about 85-90% of the deaths associated with COPD.
  • Other risk factors include repeated exposure to air pollution, second-hand smoke, dust, chemicals, and fumes.
  • According to the American Lung Association, COPD is the third leading cause of death in the United States.

Pulmonary fibrosis is a lung disease marked by damage and scarring to the tissues of the lungs, including those between and supporting the air sacs. In many cases, the cause of the inflammation and stiffening is unknown but may include:

  • Job-related or environmental exposure to small particles, including repeated exposure to inorganic substances such as asbestos, coal, beryllium, and silica
  • Repeated exposure to organic substances, such as moldy hay, animal droppings, and grain dust that causes hypersensitivity pneumonitis, an allergic reaction, that eventually leads to pulmonary fibrosis
  • Chemicals and drugs that are toxic to the lungs
  • Previous radiation treatment
  • Sarcoidosis
  • Scleroderma and other autoimmune disorders
  • Unknown (idiopathic)

Pleurisy is inflammation—often due to infection—of the thin layers of tissue that surround the lungs and line the chest cavity (pleura). The space between these layers is called the pleural space and it is normally filled with a small amount of fluid that helps the layers move smoothly across each other as you breathe.

  • If the layers become inflamed, they may rub against each other, causing sharp pains.
  • If fluid builds up in the pleural space, the pain may lessen, but the fluid can compress the lungs, causing difficulty breathing and possibly a collapsed lung.
  • A healthcare practitioner may remove some of the fluid using a procedure called a thoracentesis and the pleural fluid may be tested to help determine the cause of fluid build-up.

Lung infections can develop quickly (acute) or can be long-lasting (chronic). They can be caused by bacteriavirusesfungi or more rarely, parasites. Some examples of more common lung infections include:

  • Influenza (flu) is a viral illness that causes acute respiratory symptoms, which can be severe.
  • Croup is an infection of the windpipe and airways leading to the lungs that causes hoarseness and a cough that sounds like a seal or dog. Some cases of croup are caused by respiratory syncytial virus (RSV). An RSV infection can lead to more severe lung problems in infants, older adults, and those with weakened immune systems.
  • Acute bronchitis is what we think of when someone has a “chest cold.” Infection causes the lining of the airways (bronchi) to become inflamed, leading to shortness of breath, chest tightness and, often coughing up mucus.
  • Pneumonia is an infection of the lower-respiratory tract that can be caused by a variety of microbes.
  • Tuberculosis and nontuberculous mycobacteria (NTM) are chronic infections. Although anyone can get tuberculosis, the active disease is most common in people with weakened immune systems (such as those with HIV/AIDS). The infections caused by mycobacteria develop slowly and can be confined to the lungs or affect the body as a whole (systemic).

Lung cancer is the uncontrolled growth of abnormal cells within the lungs, usually in the layers of cells that line the air passages. These abnormal cells do not go through the natural stages of growth, division, and dying that normal cells do. They multiply without limit, often forming one or more masses of cells (tumors). Tumors can damage healthy tissue and grow large enough to interfere with breathing. Lung cancer can eventually spread (metastasize) beyond the lungs into nearby lymph nodes, tissues, and other organs. For more details, read the article on Lung Cancer.

Pulmonary hypertension is a disorder marked by a narrowing of the arteries in the lungs. This increases pressure in the arteries and forces the right side of the heart to work harder to pump blood into the lungs. This condition may co-exist and worsen a variety of lung diseases and can lead to heart failure.

Pulmonary embolism is a blood clot that usually forms in the veins of the legs or pelvis and travels to the lungs, where it blocks a blood vessel, causing chest pain, acute shortness of breath, and coughing. This condition can be life threatening and requires prompt medical attention.

Bronchopulmonary dysplasia (BPD) is caused by irritation or injury to a newborn infant’s lungs. It can occur in any infant but is most common in those born prematurely. Because their lungs might not be fully developed when they are born, most premature infants need oxygen therapy. The high amounts of oxygen delivered and/or the pressure used by a machine (ventilator) to push oxygen into a baby’s lungs can irritate or damage these babies’ airways.

Respiratory distress syndrome (RDS) of the newborn is a life-threatening breathing problem that may develop in premature infants. These babies’ lungs are not able to produce an adequate amount of the protective liquid substance called surfactant. Without sufficient surfactant, the lungs are not able to expand or inflate properly and the babies have difficulty breathing in enough oxygen.

Acute respiratory distress syndrome (ARDS) is the rapid onset of severe breathing difficulties due to extensive lung inflammation and the lungs filling with fluid. It is a sometimes-fatal condition that can be brought on by many types of injury to the lungs, including serious viral or bacterial infection, sepsis, trauma, multiple blood transfusions, drug overdose, or inhalation of substances such as salt water or smoke.

Cystic fibrosis (CF) is an inherited disease that affects the lungs and other organs. It is marked by salty sweat and the production of thick mucus that can obstruct breathing and lead to repeated respiratory infections. It is more common in Caucasians than other ethnic groups and is usually diagnosed in infancy. According to the Cystic Fibrosis Foundation, about 1,000 new cases are diagnosed in the U.S. each year.

Alpha-1 antitrypsin deficiency is an inherited disorder resulting in the lack of a protein that provides protection to the lungs. Without this protection, the lungs become progressively damaged and the person is at a greatly increased risk of developing early-onset emphysema. Other organs can also be affected. The National Organization for Rare Disorders estimates that about 100,000 Americans have this deficiency and as many as 25 million are genetic carriers of the disease.

Disorders that affect the muscles and bones in the chest, the nerves in the chest and lungs, and the heart may result in breathing difficulty or the improper exchange of gases. They include a variety of conditions, such as neuromuscular diseases like muscular dystrophy, polio, myasthenia gravisGuillain-Barré syndrome, and amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease), as well as disorders that result in abnormal spinal formation or rib cage movement, which can restrict lung expansion. [Specific testing and treatment for these non-lung disorders are not covered in this article.]

Signs and Symptoms

Signs and symptoms of lung diseases depend on the specific condition. They can vary from person to person and change over time. With chronic conditions, signs and symptoms often emerge gradually and grow worse over time. With acute conditions, they can develop quickly and may be mild to severe.

While each lung condition has its own features, there are some common signs and symptoms that are seen with many lung disorders. Examples include:

  • Persistent cough
  • Shortness of breath or labored breathing (dyspnea)
  • Wheezing, gasping for breath
  • Coughing up mucus, blood or sputum
  • Chest pain
  • Trouble exhaling, sometimes described as “like trying to breathe through a straw” (in cases of obstructive lung conditions such as COPD)
  • Skin with a bluish tint (due to lack of oxygen)
  • In cases of long-term oxygen deficiency, clubbing (enlargement) of fingertips and abnormal fingernail growth


The goals of testing are to diagnose lung diseases, determine their cause(s) where possible, evaluate their severity, and guide and monitor treatment.

  • The search for the cause of your signs and symptoms typically begins with a physical exam. As part of the exam, your healthcare practitioner will listen to your lungs for abnormal breath sounds that may indicate a lung condition.
  • Healthcare practitioners may initially order lab tests such as blood gases to evaluate oxygen and carbon dioxide levels and blood acidity (pH), one or more imaging tests, and/or pulmonary function tests to evaluate the structure and function of your lungs.
  • Depending on initial results and suspected cause of lung damage or disease, follow-up testing may be performed to help diagnose a specific condition and guide treatment.

General Laboratory Tests
Some tests may be performed to help determine your health status and how well your lungs are working. Examples include:

Specialized Tests
Depending on the lung condition suspected, some specialized tests may be performed to help make a diagnosis. Some examples include:

Non-Laboratory Tests

Lung function tests (pulmonary function tests, PFT)
A few of the more common lung function tests are listed below. For more complete information, visit the National Heart, Lung and Blood Institute website.

  • Spirometry – measures the amount and rate of air exhaled you blow into a tube; it is performed to evaluate narrowed or blocked airways.
  • Pulse oximetry – estimates the percent of hemoglobin in your blood that carries oxygen using a small device that is placed on one of your fingers.
  • Lung volume – measures the quantity of air you inhale into their lungs and how much is left in the lungs after exhalation; it helps evaluate the elasticity of the lungs, the movement of the rib cage, and the strength of the muscles associated with respiration.
  • Lung diffusion capacity – tests how well gasses from the air you breathe gets into your blood. For this test, you will breathe in and out through a tube for several minutes. You also may need to have blood drawn to measure the level of gas attached to hemoglobin in your blood.

Imaging studies

  • Chest x-ray – to look at lung structure and chest cavity
  • CT (computed tomography) scan – a more detailed evaluation of lung structure
  • MRI (Magnetic resonance imaging) – detailed pictures of organs and vessels in the chest
  • Ultrasound – used to detect fluid between the pleural membranes
  • Nuclear lung scanning – used to help detect pulmonary embolism and, rarely, to evaluate the effectiveness of lung cancer treatment
  • Positron emission tomography (PET) scans – used to help diagnose lung cancer

For more on these, see the RadiologyInfo.org website.


There are steps you can take to protect the health of your lungs and minimize your risk of lung diseases. Some examples include:

  • Not smoking and not vaping
  • Testing your home for radon, a major cause of lung cancer, as recommended by the Environmental Protection Agency (EPA). Read the EPA’s A Citizen’s Guide to Radon.
  • Limiting or protecting yourself from exposure to particulates such as asbestos, coal, beryllium, silica, molds, grain dust, from smoky or polluted air, and from chemicals and drugs known to affect the lungs
  • Protecting yourself from infections that can affect the lungs by:
    • Getting recommended vaccines such as a pneumococcal vaccine and an annual influenza vaccine
    • Limiting your exposure to people who are sick with infections such as influenza
    • Washing hands frequently


Treatment depends on your specific condition. For example:

  • For infections, the aim of treatment is to relieve symptoms and to cure and prevent spread of the infection. Antibiotics may be used to treat bacterial infections and anti-viral medications may be used to treat infections caused by influenza, for example.
  • Asthma attacks can be treated with rescue inhalers, and steroids may be used for long-term management of the disease.
  • COPD cannot be cured, but its symptoms can be managed with oxygen therapy and a variety of medications.

New therapies for lung diseases continue to be developed and your treatment may change over time. If you have been diagnosed and are living with a lung disease, talk to your healthcare practitioner about the treatment that is right for you.

For additional details on treatment, see the links in Related Content.

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