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 Healthy Steps for Healthy Lungs
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Breathing for most of us is something we do without being aware of
it. We pay no attention to this continuous activity as we work, play,
or sleep. Our lungs are responsible for this essential natural
function that gets oxygen into the bloodstream so that it can be
delivered to the cells of our body.
During a normal day, we breathe nearly 25,000 times. The more than
10,000 liters of air we inhale is mostly oxygen and nitrogen. In
addition, there are small amounts of other gases, floating bacteria,
and viruses. It also contains the products of tobacco smoke,
automobile exhaust, and other pollutants from the atmosphere in
varying amounts.
Air pollutants can affect our lungs in many ways. They may simply
cause irritation and discomfort. But sometimes inhaled materials can
cause illness or death. The lungs have a series of built-in mechanical
and biological barriers that keep harmful materials from entering the
body. In addition, specific defense mechanisms can inactivate some
disease-causing materials.
However, sometimes the normal lung defenses and barriers in the
lungs do not work as well as they should. Medical problems at birth or
during infancy and growth can affect lung development. Later in life
the lungs may be damaged by smoking, occupational exposures, or
accidents. These abnormalities allow air pollutants to break through
the lung’s defenses. The result can be respiratory problems or
diseases.
The lungs are shaped like cones and textured like a fine grained
sponge that can be inflated with air. They sit within the thoracic
cage where they stretch from the trachea (windpipe) to below the
heart. About 10 percent of the lung is solid tissue, the remainder is
filled with air and blood.
This unique structure of the lung is delicate enough for gas
exchange and yet strong enough to maintain its shape and enable it to
perform the many functions vital for keeping us healthy. Two
“plumbing” systems, the airways for ventilation (exchange of air
between the lungs and the atmosphere) and the circulatory system for
perfusion (blood flow), are coordinated by special muscles and nerves.
This arrangement enables the lung to perform its primary function of
rapidly exchanging oxygen from inhaled air with the carbon dioxide
from the blood.
Lung Diseases: How They Begin
The most common clinical signs of lung diseases are cough, chest
pain, chest tightness, shortness of breath (dyspnea), and abnormal
breathing patterns. When any of these symptoms appear, it may signal
that some vital functions of the lung have been disturbed. Because
most individuals have enormous reserves of lung tissue, the
disturbances in lung defenses or function may have begun some time
before the clinical symptoms begin to appear.
Respiratory problems can have a number of causes. They usually
arise from acute or chronic inhalation of toxic agents in the
workplace or other settings, accidents, or harmful lifestyles such as
smoking. Infections, genetic factors, or anything else that directly
or indirectly affects lung development and function can also cause
respiratory symptoms. In some lung diseases, the lung itself has been
damaged. Others result from diseases of the nervous system or the
muscles. These disorders interfere with the normal function of the
respiratory muscles so that, although the lung itself is normal,
breathing is difficult.
Estimates of the number of known lung diseases vary from a few
dozen to several hundred. Lung diseases are classified and counted
either as individual, specific diseases, or as groups of diseases that
share common features. These features may be their sites, etiologies
(initiating events), pathophysiology (abnormalities of function), or
clinical features (signs and symptoms).
Most doctors find it convenient to deal with lung diseases in
groups, based on the particular pulmonary (lung) component that is
diseased. Examples are diseases of the airways, diseases of the
interstitium (the space between tissues), or disorders of the
pulmonary circulation, the ventilatory apparatus, or gas exchange.
Often, many of these diseases occur together, particularly if they are
caused by infection, inflammation, or cancer. In such cases they
present an overlapping, progressive series of a mixture of clinical
symptoms.
Diseases of the Airways
Airways diseases are lung disorders that are primarily due to a
continuing obstruction of airflow. Acute or chronic airflow
obstruction or limitation can be caused by a variety of structural
changes in the airways. Asthma, chronic bronchitis, emphysema,
bronchiolitis, cystic fibrosis, and bronchiectasis are some common
airways diseases.
The term chronic obstructive pulmonary disease (COPD) is commonly
used for chronic bronchitis and emphysema that exist together in many
patients and in which the airway obstruction is mostly irreversible.
COPD is the fourth most common and the most rapidly increasing cause
of death in the United States.
- In asthma, reversible airway obstruction is caused by
inflammation, contraction of the airway smooth muscle, increased
mucus secretion, and plugging of the bronchioles (smaller air
passages).
- In chronic bronchitis, airway obstruction results from chronic
and excessive secretion of abnormal airway mucus, inflammation,
bronchospasm, and infections.
- In emphysema, a structural element (elastin) in the terminal
bronchioles is destroyed leading to collapse of the airway walls and
inability to exhale “stale” air.
- Bronchiolitis in children is due to viral infections that
cause obstructive inflammatory changes in the bronchioles.
- Cystic fibrosis is a genetic disease in which thickened airway
mucus, pulmonary infections, and inflammation lead to bronchiectasis
and airway obstruction.
- In bronchiectasis, airway obstruction is due to chronic
abnormal dilation (stretching) of the bronchi (larger air passages)
and the destruction of the elastic and muscular components of the
bronchial walls; it is usually caused by repeated lung infections.
Diseases of the Interstitium
The interstitium (the space between tissues) of the lungs includes
portions of the connective tissue of the blood vessels and air sacs.
Major chronic diseases of the lower respiratory tract in which
fibrosis (scarring of the lung tissue) occurs affect the interstitial
tissue. Sarcoidosis and pulmonary fibrosis are examples of the more
than 150 interstitial lung diseases. Another term for these diseases
is “stiff lung” disease. The most common symptoms are shortness of
breath after exercise and a nonproductive cough. Some patients with
interstitial lung diseases have fever, fatigue, muscle and joint pain,
and abnormal chest sounds. As these diseases advance, heart function
is affected.
Some interstitial lung diseases are caused by occupational or
environmental exposure to inorganic dusts. Workers who inhale
particles of silica are at risk for silicosis; similarly, workers in
beryllium mines may develop berylliosis. Interstitial lung diseases
may also be caused by inhaling organic dusts such as bacteria. Lung
disease that results from breathing in animal proteins is called
hypersensitivity pneumonitis. Drugs, poisons, infections, and
radiation have also been known to cause these diseases. However,
approximately two-thirds of the cases of interstitial lung diseases
have no known cause and are therefore termed “idiopathic.”
Interstitial lung diseases begin with inflammation of the lung
cells. This may be caused by an immune response or injury. The lungs
stiffen as a result of inflammation of the air sacs (alveolitis) and
scarring (fibrosis).
Disorders of Gas Exchange and Blood Circulation
Pulmonary edema occurs when excess fluid collects in the
tissues and air spaces of the lungs. The fluid interferes with gas
exchange, thus causing the patient to be short of breath and to
possibly have wheezing and a persistent cough. Pulmonary edema may
result from diseases of the heart or may occur as complications of
other illnesses such as widespread viral or other infections, drug
toxicity, exposure to high altitudes, kidney failure, or hemorrhagic
shock.
Pulmonary embolism is the sudden blocking of the blood flow in
one of the arteries in the lung. The highly branched network of blood
vessels in the lung filters the blood as it flows through it.
Sometimes the blood carries a blood clot, a fat globule, an air
bubble, or a piece of tissue that is large enough to block a blood
vessel leading to the lung’s network of capillaries. Gas exchange then
can no longer occur in this section of the lung. The result is
shortness of breath or even heart failure. The most common form of
pulmonary embolism is a thromboembolism. It occurs when a blood clot
travels from the legs or pelvis to the pulmonary blood vessels.
Respiratory failure is the inability of the lungs to perform
gas exchange. It occurs either when the muscles of the ventilatory
system fail or when the structures that perform gas exchange are
unable to function. Patients with neuromuscular diseases such as
muscular dystrophy and polio may have normal lungs, but they can
develop respiratory failure because their disease-weakened muscles are
unable to pump air into their lungs. When gas exchange is impaired,
not enough oxygen gets into the blood to fuel the body’s metabolic
activity. This condition is called hypoxemia. Chronic hypoxemia
causes the blood vessels in the lung to contract; the result is
pulmonary hypertension. Hypoxemia may also weaken the heart and the
circulatory system. Any lung disease, if not adequately treated, can
lead to respiratory failure.
Adult or acute respiratory distress syndrome (ARDS) was once
called “shock lung.” It is a type of pulmonary edema that is not
related to heart problems. It has many causes such as severe
infections, exposure to toxic fumes, circulatory collapse, sepsis
(presence of disease-causing organisms or their toxic products in
blood or other tissues), shock following severe blood loss, and bone
fractures. During ARDS, there is severe damage to the alveolar
surfaces, the blood-air barrier becomes leaky, and protein-containing
fluid fills the alveoli so that they can no longer conduct gas
exchange.
Respiratory distress syndrome of the newborn (RDS) is a type of
respiratory failure that develops most commonly in premature or low
birth weight babies whose lungs have not yet made enough surfactant.
The surfactant is critical for opening the baby’s alveoli with its
first breath and keeping them open. As the lungs collapse, respiratory
distress occurs.
Pulmonary hypertension is a disorder in which the blood
pressure in the pulmonary arteries is abnormally high. In severe
pulmonary hypertension, the right side of the heart must work harder
than usual to pump blood against the high pressure. When this
continues for long periods, the right heart enlarges and functions
poorly, and fluid collects in the ankles (edema) and the belly.
Eventually the left side of the heart begins to fail. Heart failure
caused by pulmonary disease is called cor pulmonale. The most
common causes of cor pulmonale are various combinations of emphysema,
chronic bronchitis, and/or fibrosis. When pulmonary hypertension
occurs in the absence of any other disease, it is called primary
pulmonary hypertension. It affects more women than men; its cause is
not known.
Pulmonary hypertension that results from another disease of the
heart or lungs (for example, congenital heart disease, pulmonary
thromboembolism, COPD, or interstitial fibrosis) is called secondary
pulmonary hypertension.
Lung Disorders From Unusual Atmospheric Pressure
At high altitudes, the air pressure is less than at sea level, and
the air contains less oxygen. Some individuals traveling to high
altitudes experience a variety of symptoms while they adapt to changes
in the atmosphere. The symptoms are probably due to excess fluid
accumulation in the tissues.
- Acute mountain sickness causes dizziness, headache, and
drowsiness; lethargy, shortness of breath, and nausea and vomiting
may also occur.
- High altitude cerebral edema (fluid in brain tissue) is
diagnosed when a person has symptoms of severe headache, confusion,
nausea, and vomiting. Seizures may occur that can lead to coma and
even death.
- High altitude pulmonary edema (fluid in the lung tissue) may
cause cough and shortness of breath on exercise or, when severe,
progressive shortness of breath even at rest, suffocation, and
death.
When people dive into deep water below sea level, they become
exposed to increased atmospheric pressures. This causes greater than
normal amounts of nitrogen to become dissolved in their blood. If the
diver returns too quickly to the surface, the excess nitrogen leaves
the blood in the form of bubbles that lodge in the blood vessels of
vital organs, causing necrosis (cell death) in surrounding tissue.
Although this condition (decompression sickness) typically involves
the limbs near a joint and is known as the bends, it can also occur in
the chest, lung, or brain.
Disorders of the Pleura (membrane that surrounds the lungs and
lines the thoracic cavity)
Pleural effusion means an accumulation of fluid in the pleural
space. It may result from heart failure, cancer, pulmonary embolism,
or inflammation. If the pleurae themselves are inflamed, the condition
is called pleurisy. Pleurisy causes severe chest pain with every
breath and may occur with pleural effusion. If blood is the
accumulating fluid, the condition is referred to as hemothorax. If the
accumulating liquid is pus, it is called empyema.
When air accumulates in the pleural spaces, the condition is called
pneumothorax. Mechanical injuries or diffuse diseases of the lung that
distort lung architecture can lead to pneumothorax. Such diseases
include emphysema, asthma, and cystic fibrosis. The most common
symptom of pneumothorax is sudden pain on one side of the lung
accompanied by shortness of breath.
Infections
Infections are a major cause of respiratory illness. They can be
caused by bacteria or viruses and can affect not only the lung but
also the nose, sinuses, ears, teeth, and gums. Infections may also
complicate other lung diseases.
Pneumonia, or inflammation of the lungs, is the most common
type of infectious disease of the lung. Infectious pneumonias are
usually identified by naming the cause of the infection or the pattern
of the infection in the respiratory tract. More than half the cases of
pneumonia are caused by the bacterium, Streptococcal pneumoniae (pneumococcus)
and are called pneumococcal pneumonia. Influenza A is the cause
of a significant number of cases of pneumonia in the elderly during
the winter months. Another well known form of pneumonia is
Legionnaires’ disease, which is caused by the organism,
Legionella pneumophila.
The inflammatory response of the lung in pneumonia varies depending
on the type of infection, and might include:
- lobar consolidation: solidification of the lung as air spaces
are filled with fluid and cellular material, and
- interstitial inflammation.
Pneumonia is sometimes accompanied by:
- necrosis: tissue changes accompanying cell death,
- cavitation: hollow spaces walled off by scar tissue,
- abscess: pus formation, and
- granuloma formation: production of tumor-like masses of
different kinds of cells due to a chronic inflammatory response.
Tuberculosis is a granulomatous infectious disease caused by an
organism called Mycobacterium tuberculosis.
Lung Cancer
Deaths from lung cancer were virtually unknown in the United States
until 1900, but have steadily increased since then. Currently, lung
cancer is responsible for almost one-third of all cancer deaths in
this country. The incidence of lung cancer may have reached its peak
in men, but it is continuing to rise in women. More than 90 percent of
patients with lung cancer are, or have been, cigarette smokers.
Smoking marijuana increases the risk of cancer for cigarette smokers.
Quitting cigarette smoking reduces the incidence of lung cancer, but
the level of risk reaches that of a nonsmoker only after the person
has remained a nonsmoker for 10 to 15 years.
Types of Lung Cancer: Cancers of the cells that line the major
bronchi or their primary branches are called squamous cell
carcinomas. This type of cancer metastasizes (spreads) mostly to
other sites within the thorax. Adenocarcinomas are cancers of
the glandular cells that line the respiratory tract. They most often
start at the outer edges of the lungs and spread to the brain, the
other lung, liver, and bones. Large cell carcinomas usually
begin in the outermost parts of the lung. By the time they are
diagnosed, they are often seen as large, bulky tumors. Small cell
carcinomas, also called “oat cell” cancers, usually begin in the
bronchi. Small cell carcinomas metastasize widely to the mediastinum,
liver, bones, bone marrow, central nervous system, and pancreas.
Because respiratory problems are so often caused by environmental
exposure to irritants and infectious agents, smoking tobacco, and
occupations that involve inhaling dangerous substances, many lung
diseases can be prevented by following some simple guidelines:
- Do not smoke tobacco or other products.
- Avoid exposure to dusts and irritants that can harm your
lungs.
- Wear proper protective devices if you must work in
environments that contain respiratory irritants.
- Understand that chronic cough, shortness of breath and other
lung symptoms are not normal.
- Get you flu shots. Get pneumococcal pneumonia and flu shots if
you’re over 65 or in a high risk group.
Lung damage is permanent! Take care of your lungs!
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