Chronic obstructive pulmonary disease (COPD) is a disease state characterized by airflow limitation that is not fully reversible. The most recent definition of COPD provided by the Global Initiative for Chronic Obstructive Lung Disease (GOLD), is a broad description that better explains this disease condition and its signs and symptoms defined by a persistent defined poor gas exchange and airflow as a result of a degeneration and breakdown of lung tissue as well as dysfunction of the small airways which typically worsens over time.
Chronic obstructive pulmonary diseasesmay include diseases that cause airflow obstruction (emphysema and chronic bronchitis) or any combination of these disorders. Other diseases such as cystic fibrosis, bronchiectasis and asthma were previously classified as types of chronic pulmonary disorders. However, asthma is now considered as a separate disorder and is further classified as an abnormal airway condition characterized primarily by reversible inflammation. Moreover, COPD can coexist with asthma since both of the diseases have the same major symptoms.
Pathophysiology of chronic obstructive pulmonary disease
Cases of chronic obstructive pulmonary disease, the airflow limitation is both progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases. The inflammatory response occurs throughout the airways, lung parenchyma and pulmonary vasculature. Since all inflammation response activate the body’s immune system response in an attempt to repair the injury and maintain homeostasis, over time, this injury-and-repair process causes scar tissue formation and narrowing of the airway lumen of the underlying lung tissue.
Early in the course of COPD, the inflammatory response causes pulmonary vasculature changes that are characterized by thickening of the vessel wall. These changes may result from; exposure to cigarette smoke, use of tobacco products and the release of inflammatory mediators necessary for the activation of the immune response.
Chronic obstructive pulmonary disease: Chronic Bronchitis
Chronic Bronchitis is a disease of the airways which is defined as the presence of cough and sputum production for at least three months in each of two consecutive years. In many cases, smoke or other environmental pollutants irritate the airways, resulting in hyper secretion of mucus and inflammation. This constant irritation causes the mucus-secreting glands and goblet cells to increase in number. Ciliary function is also significantly reduced and more mucus is produced. The bronchial walls become thickened, the bronchial lumen narrows and mucus eventually plugs the airways. Alveoli adjacent to the bronchioles may become damaged and fibrosed, resulting in altered function of the alveolar macrophages. A wide range of viral and bacterial infections can produce acute episodes of bronchitis. Exacerbations of chronic bronchitis are most likely to occur during cold seasons.
Chronic obstructive pulmonary disease: Emphysema
In emphysema, impaired gas exchange and carbon dioxide exchange results
from destruction of the walls of over distended alveoli. Emphysema is a pathologic term that describes an abnormal distention of the air spaces beyond the terminal bronchioles with the destruction of the walls of the alveoli. Emphysema is generally the end process of the permanent damage that has progressed slowly for many years. As the walls of the alveoli are destroyed, the alveolar surface area in direct contact of the pulmonary capillaries continually decreases causing an increase in dead space (lung area where no gas exchange can occur). This type of chronic obstructive pulmonary disease is irreversible which often leads to hypoxemia and eventually cardiac failure.