NURS 251 Pharmacology Module 5
Module 5
5.1 : Introduction to Pulmonology
The main function of the respiratory system is two-fold: (1) to deliver
... [Show More] oxygen to the cells of the body and (2) remove
carbon dioxide from the body. This is accomplished through the combination of the upper respiratory tract working in
communication with the lower respiratory tract. A diagram of the anatomy of the respiratory tract is shown in Figure 5.1.
The upper respiratory tract (URT) is outside the chest cavity and includes the nose, and nasopharynx (down to the
larynx). The lower respiratory tract (LRT) includes the organs within the chest including the trachea, bronchial tree, and
lungs. When a person breathes in air, oxygen diffuses across the alveoli (microscopic sacs) in the lungs where it is
exchanged for carbon dioxide. The diffused oxygen is then taken to the rest of the body through the circulatory system.
Figure 5.1 Anatomy of the Respiratory Tract. Above is a diagram of the anatomy of the respiratory tract broken down between the
Upper Respiratory Tract (URT) and the Lower Respiratory Tract (LRT).
There are several common diseasesthat affect the airways and this exchange of gas, the most common of which are
asthma and chronic obstructive pulmonary disease (COPD).
Asthma is the general term for recurrent and reversible shortness of breath resulting from the narrowing of the bronchi
and bronchioles.
COPD consists of both emphysema and chronic bronchitis.
Emphysema is a disease process involving inflammation of the alveoli.
Chronic Bronchitis is characterized by chronic inflammation or irritation on the lower respiratory tract,specifically the
bronchi.
The primary drugs used in the treatment of both asthma and COPD include bronchodilators and a variety of antiinflammatory and antiallergic agents.
Pathophysiology
All three of these diseases have one primary similarity in that they all involve obstruction of airflow through the airways.
Chemical Mediators are defined as a substance released from mast cells and white blood cells during inflammation and
allergic reactions. As such, chemical mediators are responsible for most of the symptoms and complications associated
with asthma and COPD. The only chemical mediator with a known involvement where drug therapy has been shown to
help patient symptoms is leukotrienes. Leukotrienes are potent bronchoconstrictors with a long duration of action. They
stimulate receptors responsible for bronchoconstriction, edema and other inflammatory actions. There is a class of drugs
called leukotriene inhibitors that inhibit these actions and have an important role in treating asthma specifically.
Asthma
The narrowing of the bronchioles can be caused by bronchospasm, inflammation, edema and the production of mucus.
This ultimately obstructs airflow meaning that the carbon dioxide cannot get out and the oxygen cannot get in.
There are different types of asthma. Some asthma is caused by outside factors such as allergens; this is often referred to
as allergic asthma. Conversely, intrinsic asthma is caused by unknown factors. In some cases, certain factors have
precipitated the asthma attack such asrespiratory infections, stress, or cold weather. It is not fully understood why some
people seem to be predisposed to asthma attacks. [Show Less]