Chronic obstructive pulmonary disease (COPD) is an inflammatory disease of the lungs. This is a progressive and irreversible condition that often leads to breathing problems. However, treatment and lifestyle changes can help relieve symptoms and slow progression. Learn about the pathophysiology of COPD and how it affects lung function.
Chronic Obstructive Pulmonary Disease Conditions
The two main forms of COPD are chronic bronchitis and emphysema. People with COPD can have either form or both.
Chronic bronchitis is inflammation of the bronchi (bronchi), the air sacs (alveoli) that carry air in and out of the lungs. Due to inflammation, mucus builds up in the tubes, making it harder for your lungs to move air through them. Symptoms of chronic bronchitis may include:
- shortness of breath
- tightness in the chest
Healthy air sacs are stretchy and resilient, filling each air sac with air when you inhale and deflating when you exhale. In emphysema, the walls separating the air sacs (and possibly the air sac walls) are damaged, causing the air sacs to deform.
This damage causes the air sacs to not inflate and deflate properly, ultimately making it difficult for the lungs to get oxygen and carbon dioxide out of the body. Symptoms of emphysema may include:
- tightness in the chest
- shortness of breath
The main cause of chronic bronchitis and emphysema is smoking, but other risk factors include exposure to lung irritants such as air pollution, age (usually symptoms begin in people 40 or older), and genetics.
The thoracic cavity contains two lungs: one on the right side of the chest and one on the left side. Each lung is made up of different parts called lobes. The right lung has three lobes; the left has only two. Each leaf is further divided into segments and leaflets.
The space between the lungs that contains the heart, great blood vessels, and esophagus is called the mediastinum. A set of tubes, or airways, carry oxygen to each part of the lungs.
When you breathe, air enters your respiratory system through your nostrils (nostrils). It then passes through the nasopharynx (the area of the throat behind the nose) and the oropharynx (the area of the throat behind the mouth).
These structures make up the upper airway, which is lined with ciliated mucosa.This is a protective moist tissue layer containing tiny hair-like protrusions (cilia) Helps heat and humidify inhaled oxygen and help remove foreign bodies and excess mucus.
Air continues through the larynx (voice box)—a structure that connects the upper and lower airways—and down through the trachea (trachea), which connects the larynx to the bronchi. The bronchi are the larger airways in the lungs that end in smaller airways called bronchioles. The bronchi and bronchioles together make up the bronchial tree.
Bronchioles terminate in alveolar ducts, forming alveolar sacs composed of millions of alveoli. The alveoli are the primary gas exchange structures in the lungs, where oxygen enters the blood and carbon dioxide is removed. All of these structures work together as your respiratory system.
Anatomy of the Lung
Purpose of the lungs
The lungs are made up of spongy elastic fibers that expand and contract when we inhale and exhale, respectively. The role of the lungs is twofold: to transport oxygen (O2) to the cells and tissues of the body, and to remove carbon dioxide (CO2), the waste product of breathing, from the blood.
Oxygen is the most important nutrient for the human body, it helps your body convert the food you eat into energy, and similar to car exhaust, carbon dioxide is removed from your body every time you exhale.
COPD isn’t the only inflammation that affects the lungs. Inflamed lungs can also develop due to infection or damage to the lung’s structure. In addition to autoimmune diseases, genetic diseases such as cystic fibrosis can also cause inflammation in the lungs. Lung inflammation caused by a mild infection like the flu or an injury like a broken rib or stab wound usually resolves with time and treatment.
However, for those who have inflammation of the lung structures due to persistent smoking habits, exposure to irritants, or genetic diseases such as cystic fibrosis, inflammation can become a chronic problem and can affect the lung structures cause irreversible damage. This damage can lead to health complications because the lungs cannot effectively remove oxygen and carbon dioxide from the body.
Chronic smoking is the number one cause of COPD, but repeated exposure to secondhand smoke, air pollution, and occupational exposure (coal, cotton, grains) are also important risk factors.
Chronic inflammation plays a major role in the pathophysiology of COPD. Smoking and other airway irritants can cause neutrophils, T lymphocytes, and other inflammatory cells to build up in the airways. Once activated, they set off an inflammatory response in which molecules called inflammatory mediators flood the site in an attempt to destroy and remove inhaled foreign debris.
Under normal conditions, the inflammatory response is useful and leads to healing. In fact, without it, the body would never recover from an injury. In COPD, repeated exposure to airway irritants triggers a persistent inflammatory response that never seems to shut itself off. Over time, this process causes structural and physiological changes in the lungs, which gradually deteriorate.
As the inflammation continues, the airways constrict and become excessively narrow and swollen. This leads to excess mucus and poorly functioning cilia—a combination that makes airway clearance especially difficult. When people with COPD are unable to clear their secretions, they develop the hallmark symptoms of COPD, including chronic production of phlegm, wheezing, and difficulty breathing.
Finally, the buildup of mucus attracts large numbers of bacteria that thrive in the warm, moist airways and lungs.
Regardless of the type of COPD, the main goals of COPD treatment are to improve quality of life, slow disease progression, control COPD symptoms, and prevent COPD from getting worse.
No other factor is more important than smoking cessation in slowing the progression of COPD. Other treatment options include antibiotics (for patients with evidence of bacterial infection), inhaled bronchodilators, corticosteroids, aerosol therapy, pulmonary rehabilitation, oxygen therapy (for patients with hypoxia), influenza vaccine, and sometimes, especially those with Patients with end-stage COPD, surgical intervention.
Since smoking is the leading cause of COPD, the best way to prevent COPD is to quit smoking or never start smoking. Additionally, avoiding exposure to lung irritants such as secondhand smoke, air pollution, environmental or occupational chemicals, and dust can reduce your chances of developing COPD. Some ways to avoid irritating exposures include:
- Stay indoors when air pollution rises
- No smoking at home and workplace
- If exposed to occupational chemicals, use body and respiratory protective equipment such as masks, gloves and goggles
COPD is usually preventable. While quitting smoking can be difficult, there are ways to quit if you do. Also, try to avoid lung irritants. If you learn you have COPD, thoroughly discuss with your doctor the many treatment options available to control symptoms and slow progression.
Frequently Asked Questions
What are the four stages of COPD?
The Global Initiative for Chronic Obstructive Pulmonary Disease (GOLD) devised a classification system for COPD severity:
- Stage 1: Mild
- Stage 2: Moderate
- Stage 3: Severe
- Stage 4: Very serious
How is COPD Diagnosed?
Tests commonly used to diagnose COPD include functional lung tests, chest X-rays, and blood tests. Your healthcare professional will also look at your symptoms and your and your family’s medical history.
How long can you live with COPD?
Life expectancy for people with COPD depends on factors such as age, overall health and severity of the condition. A system called the BODE index calculates likely life expectancy by measuring body maximal index (BMI), airway obstruction, dyspnea, and exercise tolerance.