What is emphysema?

Causes and Symptoms

Emphysema is a lung disease in which damage to the lungs causes shortness of
breath and can lead to heart or respiratory failure. A discussion of the structure
and function of the normal lung can illuminate the nature and effects of this
damage.

Air—along with gases, smoke, germs, allergens, and environmental pollutants—passes
from the nose and mouth into a large duct called the trachea. The
trachea branches into smaller ducts, the bronchi and
bronchioles (small branches of the bronchi), which lead to tiny air sacs called
alveoli. The respiratory system is like an upside-down tree: The trachea is the
trunk, the bronchi and bronchioles are similar to the branches, and the alveoli
are similar to the leaves. The blood vessels of the alveoli carry red blood cells,
which pick up oxygen and transport it to the rest of the body. The cellular waste
product, carbon dioxide, is released to the alveoli from the bloodstream and then
exhaled. The alveoli are supported by a framework of delicate elastic fibers and
give the lung a very distensible quality and the ability to “snap back,” or
recoil.

The lungs and bronchial tubes are surrounded by the chest wall, composed of bone
and muscle and functioning like a bellows. The lung is elastic and passively
increases in size to fill the chest space during inspiration and decreases in size
during expiration. As the lung (including the alveoli) enlarges, air from the
environment flows in to fill this space. During exhalation, the muscles relax, the
elasticity of the lung returns it to a normal size, and the air is pushed out. Air
must pass through the bronchial tree to the alveoli before oxygen can reach the
bloodstream and carbon dioxide can get out, because it is the alveoli that are in
contact with blood vessels. The bronchial tree has two kinds of special lining
cells. The first type can secrete mucus as a sticky protection against injury and
irritation. The second type of cell is covered with fine, hairlike structures
called cilia. These cells are supported by smooth muscle cells and elastic and
collagen fibers. The cilia wave in the direction of the mouth and act as a defense
system by physically removing germs and irritating substances. The cilia are
covered with mucus, which helps to trap irritants and germs.

When alveoli are exposed to irritants such as cigarette smoke, they produce a
defensive cell called an alveolar macrophage. These cells engulf irritants and
bacteria and call for white blood cells, which aid in the defense against foreign
bodies, to come into the lungs. The lung tissue itself also becomes a target for
the enzymes or chemical substances produced by the alveolar macrophages and
leukocytes (white blood cells). The enzymes vigorously attack the elastin and
collagen of the lungs, the lung alveoli lose their elastic recoil, and air is
trapped, making exhalation difficult.

Emphysema and a related disease, chronic bronchitis, in which the
airways of the long become chronically inflamed, often work in concert. They are
grouped together under the term chronic obstructive pulmonary disease
(COPD). Chronic bronchitis weakens and narrows the bronchi. Often, bronchial walls
collapse, choking off the vital flow of air. Air is also trapped within the
bronchial walls. Weakened by enzymes, the walls of the alveoli rupture and blood
vessels die. Lung tissue is replaced with scar tissue, leaving areas of destroyed
alveoli that appear as “holes” on an X-ray. Small areas of destroyed alveoli are
called blebs, and larger ones are called bullae.

As emphysema progresses, the patient develops a set of large, overexpanded lungs
with a weakened and partially plugged bronchial tree subject to airway collapse
and air trapping with blebs and bullae. Breathing, especially exhalation, becomes
a slow and difficult process. The patient often develops a barrel chest. The
scientific world calls the mismatching of breathing to blood distribution a
ventilation-to-perfusion imbalance; that is, when air arrives in the alveolus,
there are no blood vessels there to transport the vital gaseous cargo to the cells
(as a result of enzymatic damage). A person with COPD has a bronchial tree with a
narrow, defective trunk (chronic bronchitis) and sparse leaves (emphysema).

The loss of elasticity of the lung and alveoli is a critical problem in the
patient with emphysema. About one-half of the lungs’ elastic recoil force comes
from surface tension. The other half comes from the elastic nature of certain
fibers throughout the lungs’ structure. Emphysema weakens both of these forces
because it destroys the elastic fibers and interferes with the surface tension.
Fluid, a saline solution, bathes all the body’s cells and surfaces. In the lung,
this fluid contains a surfactant, a substance that interferes with water’s
tendency to form a spherical drop with a pull into its center (and ultimate
collapse). The tissue that gives shape to the lungs is composed of specialized
fibers that contain a protein called elastin. These elastic fibers are also found
in the alveolar walls and in the elastic connective tissue of the airways and air
sacs. The amount of elastin in lung tissue determines its behavior. Healthy lungs
maintain a proper balance between destruction of elastin and renewal. (Other parts
of the body, such as bones, do this as well.) If too little elastin is destroyed,
the lungs have difficulty expanding. If too much is destroyed, the lungs
overexpand and cannot recoil properly.

The process of elastin destruction and renewal involves complex regulation.
Specialized lung cells produce new elastin protein. Others produce elastase, an
enzyme that destroys elastin. The liver plays a role in the production of a
special enzyme known as alpha-1-antitrypsin, which controls the amount of elastase
so that too much elastin is not digested. In emphysema, these regulatory systems
fail: Too much elastin is destroyed because elastase production is no longer
controlled, apparently because alpha-1-antitrypsin production has been reduced to
a trickle. In some persons, alpha-1-antitrypsin deficiency is an
inherited condition.

The loss of elastin (and thus elastic recoil) means that the lungs expand beyond
the normal range during inspiration and cannot resume their resting size during
expiration. Thus, alveoli overinflate and rupture. This further reduces
elasticity, because the loss of each alveolus further impairs the surface tension
contribution to the lungs’ ability to recoil. Thus, a state of hyperinflation is
assumed in the patient with emphysema. This leads to stretched and narrowed
alveolar capillaries, loss of elastic tissue, and dissolution of alveolar walls.
The lungs increase in size, the thoracic (chest) cage assumes the inspiratory
position, and the diaphragm becomes low and flat instead of convex. The patient
becomes short of breath with any type of exertion. As the disease worsens, the
patient’s skin takes on a cyanotic (bluish) color as a result of poor oxygenation
and perfusion. Wheezing is often present, and coughing is difficult and
tiring. In the worst cases, even talking is enough exertion to produce a spasmodic
cough. The hyperinflated chest causes inspiration to become a major effort, and
the entire chest cage lifts up, resulting in considerable strain.

Emphysema may be diagnosed by the early symptom of dyspnea (shortness of breath)
on exertion. In advanced cases, the distended chest, depressed diaphragm,
increased blood carbon dioxide content, and severe dyspnea clearly point to the
disease.

Treatment and Therapy

The initial step in treating emphysema is to eliminate the causes of irritation:
smoke, polluted air, infection, and allergies. For smokers, smoking
cessation is critical, and bupropion may
be prescribed to help with smoking cessation. To improve dyspnea and the patient's
quality of life, pulmonary rehabilitation may be part of the treatment process,
including exercise training, nutrition counseling, and patient education. Exercise
training may include exercises to strengthen the chest muscles as well as
breathing techniques to improve air flow into the lungs.

A number of medications are useful in the treatment of emphysema, although no
medications have been shown to modify the long-term decline in lung function seen
in patients with emphysema or COPD. Instead, medications are used to decrease
symptoms and reduce complications. Bronchodilator drugs relieve bronchospasms,
reduce wheezing and dyspnea, and improve respiratory muscle function. Categories
of bronchodilators include the beta-2 agonists, which may be short-acting or
long-acting, and inhaled anticholinergics. Examples of short-acting beta-2
agonists include albuterol, terbutaline, fenoterol, and levalbuterol. Among the
long-acting beta-agonists are arformoterol and formoterol. Some side effects of
beta-agonists include nervousness, headache, nausea, and muscle cramps. Inhaled
corticosteroids may also be used in the treatment of emphysema; however, the
long-term use of corticosteroids may increase the risk of pneumonia.

Antibiotics are sometimes prescribed for patients with
emphysema to combat bacterial infections that can
dramatically worsen the effects of their condition. Furthermore, the
influenza
vaccine and pneumococcal polysaccharide vaccine are
strongly recommended to reduce serious illness and complications.

Sometimes emphysema patients are given supplemental oxygen, also called
oxygen
therapy, if their lung function is too impaired to keep the
oxygen levels in their blood sufficiently high. Portable oxygen tanks that deliver
oxygen through a tube and a mask can give patients greater mobility to carry out
tasks of daily living. In rare cases, surgery is an option for severe cases of
emphysema. The two kinds of surgery available are lung volume reduction surgery
(LVRS) and, as a last resort, a lung transplant. The aim of LVRS is to remove the
most diseased portions of the lung to give the healthier portion more room to
function. A lung transplant may be considered if a patient's lungs are in danger
of failing entirely and if the patient is determined to be strong enough to endure
the procedure and the recovery period.

Individuals with emphysema should avoid both excessive heat and excessive cold. If
body temperature rises above normal, the heart works faster, as do the lungs.
Excessive cold stresses the body to maintain its normal temperature. Smog, air
pollution, dusts, powders, and hairspray should be avoided. Finally, a healthy
diet consisting of foods high in calcium, vitamins, complex carbohydrates,
proteins, and fiber is advised for the patient with lung disease. Caloric
supplementation may improve exercise capacity in patients with COPD, especially
undernourished patients.

Perspective and Prospects

According to the US Centers for Disease Control and Prevention, chronic lower
respiratory diseases (primarily COPD) were the third leading cause of death in the
United States in 2011. The World Health Organization reported in 2014 that COPD
was also the third leading cause of death worldwide, accounting for 3.1 million
deaths in 2012. Although the death rates from COPD have declined slightly among
men from 1999 to 2010, they have stayed about the same for women, and the overall
average has barely changed. Aside from death, a disease such as emphysema can
cause long years of disability, joblessness, loss of income, depression,
hospitalization, and an inability to perform normal activities.

Smoking is, by far, the single most important risk factor for emphysema. The
prevalence of COPD among smokers is estimated to be approximately 15 percent.
Socioeconomic status also influences rates of COPD, with lower-income workers
experiencing higher rates of the disease. COPD also correlates negatively with
level of education: The rate in 2011 among those without a high school diploma was
9.5 percent; 6.8 percent among those with a high school diploma; and 4.6 percent
among those with some college. The prevalence of COPD also increases with age.

A number of economic pressures are likely to move COPD treatment from the hospital
to the home. When effectively carried out by a well-trained health team, home care
can lower medical costs. The COPD patient who finds a knowledgeable doctor and who
begins a comprehensive rehabilitation program is the one who can look forward to a
life that is more productive and more comfortable.

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