EMPHYSEMA
Emphysema is a progressive COPD. The alveoli become enlarged and damaged,
trapping air in the over expanded alveoli preventing an adequate exchange of
oxygen and carbon dioxide.
Emphysema is caused by smoking cigarettes, by inhaling contaminants from
the environment, or by the lack of the alpha 1 -antitrypsin protein. The lung con-
tains bacteria that release proteolytic enzymes that destroy alveoli. The alpha 1 -
antitrypsin protein inhibits proteolytic enzymes and protects the alveoli.
Excess mucus as well as the residue from cigarette smoking and airborne pol-
lutants find their way down the airways and plug the terminal bronchioles. The
network of alveoli then loses their fiber and become inelastic and unable to
spring back to size after expanding during inspiration. Alveoli enlarge as many
of the alveolar walls are destroyed. Air becomes trapped in the overexpanded
alveoli leading to inadequate gas exchange (O 2 and CO 2 ).
ASTHMA
Acute asthma is a reactive airway disease (RAD) that occurs when lung tissue is
exposed to extrinsic (environmental) or intrinsic (internal) factors that stimulate
the bronchoconstrictive response. This causes bronchospasms that result in the
patient wheezing and having difficulty breathing. More than 500,000 patients
are hospitalized and 5000 die from asthma each year making acute asthma the
third leading cause of preventable hospitalizations in the United States.
There are a variety of allergens (something that causes an allergic reaction)
that can trigger an asthma attack. These include humidity, air pressure changes,
temperature changes, smoke, fumes (exhaust, perfume), stress, emotional upset,
and allergies to animal dander, dust mites, and drugs such as aspirin, indometh-
acin, and ibuprofen.
Allergens attach to mast cells and basophils in connective tissues causing an
antigen-antibody reaction to occur. Mast cells stimulate release of chemical
mediators. These chemicals constrict the bronchi, increase mucous secretions,
stimulate the inflammatory response, and cause pulmonary congestion.
Chemical mediators include histamines (proteins that are potent vasodilators),
cytokines (small proteins that mediate and regulate the immune system, inflam-
matory response and hematopoiesis [red cell production]), serotonin (CNS
neurotransmitter), ECF-A (eosinophil chemotatic factor of anaphylaxis) and
leukotrines. Histamine and ECF-A are strong bronchoconstrictors that stimulate
the contraction of bronchial smooth muscles. Cyclic adenosine monophosphate
(cyclic AMP or cAMP) maintains bronchodilation. Histamines, ECF-A, and
CHAPTER 14 Respiratory Diseases^263