Have you even wondered what happens to your lungs when you have COPD? While COPD pathophysiology is not completely understood, there are some things that we DO know about it. But first, to get a firmer grasp on COPD pathophysiology, we must understand how the lungs function normally.
How Our Lungs Work
The chest cavity contains two lungs - one on the right side and one on the left side of the chest. Each lung is composed of sections, called lobes. The right lung has three lobes and the left, only two. Each lobe is further divided into segments and lobules. The space between the lungs that contains the heart, great vessels and esophagus is called the mediastinum. A set of tubes, or airways, delivers oxygen to each section of the lung.
As we breathe air in through our nares, the oxygen passes through the nasopharynx (area of throat behind nose) and the oropharynx (area of throat behind mouth). These structures make up the upper airways and are lined with ciliated mucosa, a protective, moist tissue layer containing tiny hair-like projections which help warm and humidify inhaled oxygen and remove foreign particles from it. Cilia also help rid the airways of excess mucus. Oxygen then passes through the larynx (voice-box), a structure that connects the upper and lower airways, down through the trachea (windpipe), which connects the larynx to the bronchi. The bronchi are larger airways of the lungs which subsequently terminate into smaller airways called bronchioles. Together, the bronchi and bronchioles make up the bronchial tree. The bronchioles end in alveolar ducts which lead to alveolar sacs made up of millions of alveoli. The alveoli are the primary, gas-exchanging structures in the lungs where oxygen enters the blood and carbon dioxide is removed. To learn more about how your lungs function, take a tour of the respiratory system.
The Purpose of the Lungs
The lungs are made up of spongy, elastic fibers which allow them to stretch and constrict when we breathe in and out, respectively. The purpose of the lungs is twofold: To deliver oxygen (O2) to the cells of the body, while removing carbon dioxide (CO2). Oxygen, the body's most important nutrient, helps our bodies turn the food that we eat into energy and, similar to the exhaust on our cars, CO2, the waste product of respiration, is removed from our bodies every time we exhale.
More About COPD
COPD is an umbrella term for a broad classification of disorders, including emphysema, chronic bronchitis, and bronchiectasis. COPD is an irreversible lung disease associated with dyspnea upon exertion and a reduction of airflow both into, and out, of the lungs. Cigarette smoking is the number one cause of COPD, but secondhand smoke, air pollution and occupational exposure (to coal, cotton, grain) are also important risk factors that contribute to its development.
COPD Pathophysiology Not Completely Understood
According to the American Academy of Family Physicians, COPD pathophysiology is not completely understood. Playing a major role is that of chronic inflammation of the cells which line the bronchial tree. Smoking, and other airway irritants, perpetuates an ongoing inflammatory response which leads to hyperactivity of the airways, whereby the smooth muscle of the airways constrict and narrow excessively. This causes the airways to become swollen, excess mucus to be produced and the cilia to function poorly. As the disease progresses, COPD patients find it increasing difficulty to clear their secretions, developing a chronic, productive cough, wheezing and dyspnea, the hallmark symptoms of COPD. To further complicate matters, as excess mucus is produced, it begins to pool in the airways, providing a perfect breeding ground for bacteria to multiply. This leads to further inflammation, the formation of diverticula (pouch-like sacs) in the bronchial tree and bacterial infections which occur frequently in COPD patients.
What About Airway Obstruction?
The airway obstruction that causes a reduction in airflow in COPD patients varies according to the disease. For example, in chronic bronchitis and bronchiectasis, blockage of the airways is a direct result of excess mucus and secretions. In emphysema, the obstruction to oxygen and carbon dioxide exchange results from the enlargement and destruction of the alveoli.
A Word About COPD Treatment
The main goal of COPD treatment, no matter which type of COPD, is to improve quality of life, slow the progression of the disease, control COPD symptoms and prevent COPD exacerbation.
No other factor carries more weight in slowing the progression of COPD than smoking cessation. Other treatment options include antibiotics (for those with evidence of bacterial infection), inhaled bronchodilators, corticosteroids, aerosol therapy, pulmonary rehabilitation, oxygen therapy (for patients who are hypoxic), flu shots, and, in those suffering from end-stage COPD who meet specific criteria, surgical intervention.
Presenting Our COPD Videos
Still unclear about COPD pathophysiology? Be sure to watch the following videos:
Smeltzer, S., Bare, B. Brunner and Sudarth's Textbook of Medical-Surgical Nursing. Eighth edition. Lippincott Publishers. Philidelphia, PA. 1996. Hunter, Melissa, M.D, King, Dana, M.D. COPD: Management of Acute Exacerbations and Chronic Stable Disease American Family Physician. 2001, August 15.
