COPD Pathophysiology and How the Lungs Work

Understanding How COPD Develops and Affects Your Lung Structures

Chronic obstructive pulmonary disease (COPD) pathophysiology is a term used to describe the functional changes that occur in the lungs as a result of the disease process. In order to better understand the lung abnormalities that are present in COPD, learn about normal lung functioning.

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How Your Lungs Work

The chest cavity contains two lungs: one on the right side of the chest and one on the left side. Each lung is composed of different sections called lobes. The right lung has three lobes; 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 you breathe, air enters your respiratory system through your nares. It then passes through the nasopharynx (area of the throat behind the nose) and the oropharynx (area of the throat behind the mouth). These structures make up the upper airways, which are lined with ciliated mucosa. This is a protective, moist tissue layer containing tiny hair-like projections that help warm and humidify inhaled oxygen and assist in the removal of foreign particles and excess mucus.

Air continues on through the larynx (voice-box)—a structure that connects the upper and lower airways—and then 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. All of these structures function together as your respiratory system.

The Purpose of the Lungs

The lungs are made up of spongy, elastic fibers that 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 and tissues of the body and to remove carbon dioxide (CO2), the waste product of respiration, from the blood. Oxygen, the body's most important nutrient, helps your body turn the food that you eat into energy and, similar to car exhaust, CO2 is removed from your body every time you exhale.

Understanding COPD Pathophysiology

COPD is characterized by airflow limitation that is poorly reversible. Cumulative, chronic exposure to cigarette smoking is the number one cause of the disease, but repeated exposure to secondhand smoke, air pollution, and occupational exposure (to coal, cotton, grain) are also important risk factors.

Chronic inflammation plays a major role in COPD pathophysiology. Smoking and other airway irritants cause neutrophils, T-lymphocytes, and other inflammatory cells to accumulate in the airways. Once activated, they trigger an inflammatory response in which an influx of molecules, known as inflammatory mediators, navigate to the site in an attempt to destroy and remove inhaled foreign debris.

Under normal circumstances, the inflammatory response is useful and leads to healing. In fact, without it, the body would never recover from injury. In COPD, repeated exposure to airway irritants perpetuates an ongoing inflammatory response that never seems to shut itself off. Over time, this process causes structural and physiological lung changes that get progressively worse.

As inflammation continues, the airways constrict, becoming excessively narrow and swollen. This leads to excess mucus production and poorly functioning cilia—a combination that makes airway clearance especially difficult. When people with COPD can't clear their secretions, they develop the hallmark symptoms of COPD, including a chronic productive cough, wheezing, and dyspnea. Finally, the build-up of mucus attracts a host of bacteria that thrive and multiply in the warm, moist environment of the airway and lungs.

COPD Treatment

The main goal of COPD treatment, no matter which type of COPD, is to improve the 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.

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3 Sources
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