More Slideshows from eMedicineHealth
What Is Asthma?
Asthma is a chronic lung disorder that can make breathing difficult. It causes inflammation, swelling, and narrowing of the airways (bronchial tubes).
Chronically inflamed bronchial tubes become very sensitive to inhaled allergens or irritants such as pollen, pollution, tobacco smoke, or triggers such as exercise.
The Scope of the Problem
About 25 million people in the U.S have asthma; 7 million of those are children. Asthma causes over 14 million visits to doctors each year and nearly 2 million visits to emergency departments. Over 3,300 people die each year from asthma.
Normal Bronchial Tubes
When we inhale, air passes into our windpipe (trachea), our diaphragm contracts and moves downward creating air space in our chest cavity. The air enters the lungs, passing through the bronchial tubes and finally to the air sacs (alveoli). Oxygen from the air passes from the alveoli and into the bloodstream through the tiny blood vessels called capillaries. The capillaries deliver this oxygen-rich blood to your pulmonary vein, which goes to the left side of the heart. Your heart then pumps the oxygen-rich blood to the rest of the body. When you exhale, air that is rich in carbon dioxide (CO2) passes out of your lungs, through the windpipe, and out your nose or mouth.
How Does Asthma Affect Breathing?
When a person has asthma, the airways become inflamed and sensitive. This swelling narrows the airways, making breathing difficult. Three factors: inflammation, bronchospasm, and hyperreactivity cause this narrowing and will be discussed in the following slides.
Inflammation that airways (bronchial tubes) swollen and sensitive is the main factor that causes them to narrow. Inflamed bronchial tubes result in a smaller space for air to pass through. In addition, the muscles surrounding the airways may tighten, further narrowing the space for airflow.
When the airways react they can also produce more mucus, which is a sticky and thick liquid substance that can clump together and even further narrow air passages. On top of that certain allergy and inflammation cells (eosinophils and white blood cells) accumulate at the site of the inflammation, causing tissue damage and even further narrowing airways.
This chain reaction can result in difficulty breathing and asthma symptoms.
During an asthma attack, people may experience bronchospasm, where the muscles surrounding the airways (bronchial tubes) tighten and further narrow the airways. Cough and wheezing may be symptoms of bronchospasm, and bronchospasm can occur when the airways are irritated by cold air.
People with asthma may become hyperreactive, or sensitive, to certain inhaled allergens or irritants. These are called triggers, and these triggers can cause even more inflammation and narrowing of the airways.
Which Triggers Cause an Asthma Attack?
Things that can cause an asthma attack are referred to as "triggers." Not everyone with asthma has the same triggers. People with asthma need to learn what their triggers are so they can manage or avoid them.
Asthma triggers include allergens such as:
- common foods including peanuts, egg, dairy, soy, and fish
Asthma triggers include irritants such as:
- tobacco smoke
- viral upper respiratory infections
- environmental pollutants such as smog or vehicle fumes
- indoor irritants such as perfumes, detergents, and paints
- work-related exposure to chemicals, dusts, and gases
- drugs such as aspirin or NSAIDs (nonsteroidal anti-inflammatory drugs), and beta-blockers
- GERD (gastroesophageal reflux disorder)
Who Can Develop Asthma?
Asthma seems to be caused by both hereditary (genetic) and environmental factors. While asthma can develop at any age, it tends to most commonly start in children age 2-6 years. At this age, asthma is triggered by allergens such as dust mites, tobacco smoke, and viral upper respiratory infections
Adults can also develop asthma, and only about 30% of the triggers are related to allergies such as to pets, mold, dust, or perfumes. Risk factors for adult-onset asthma include being female, obesity, hormonal fluctuations such as those experienced during or after pregnancy or menopause, and viral or other infections.
Types of Asthma: Allergic (Extrinsic)
Allergic, or extrinsic, asthma is that which is triggered by an allergic reaction. It is an immune system response to an irritant. This is the most common form of asthma, affecting more than half of all sufferers. It can often be managed with medication.
Types of Asthma: Non-allergic (Intrinsic)
Non-allergic, or intrinsic, asthma is caused by factors other than allergies, such as exercise, stress or anxiety, inhaling cold air, smoke, viral infections, and other irritants. This type of asthma is less common, it develops more often in adults, and is more difficult to treat than allergic (extrinsic) asthma.
Symptoms and Signs of Asthma
Symptoms of asthma, both allergic and non-allergic, include:
- Shortness of breath
- Chest tightness
Not everyone with asthma will experience all symptoms and the severity of symptoms can vary depending on the individual, and even in an individual may vary over time.
How Is Asthma Classified?
The National Asthma Education and Prevention Program classifies asthma into four categories, determined by the patient's symptoms and lung function tests:
- Mild persistent
- Moderate persistent
- Severe persistent
Acute Asthma Attack
An "asthma attack" is an acute worsening of asthma symptoms. During an acute asthma attack, there is inflammation, bronchospasm, and mucus produced, leading to symptoms such as difficulty breathing, shortness of breath, wheezing, coughing, and even interference with daily activities. Many times asthma attacks can be controlled with inhalers (inhaled bronchodilators). If that does not work, the patient should call 911 or be taken to an emergency room immediately. When patients do not respond to initial treatment it can result in a life-threatening reaction called status asthmaticus.
Asthma Exams and Tests
To diagnose asthma, first a doctor will take a history and do a physical exam. Tests may be performed such as:
- lung (pulmonary) function tests including a spirometer, or peak flow meter to measure lung function
- blood tests to measure levels of IgE, antibodies that are released during allergic reactions
- bronchoprovocation to measure how sensitive your airways are
- tests to rule out other conditions such as reflux disease or sleep apnea
- chest x-rays or EKG to find out if a foreign object or another condition is causing your symptoms
Medical Treatment of Asthma
Asthma medications are classified as either for long-term control, or quick relief. Most are inhaled rather than taken in tablet or liquid form, to act directly on the airways where the breathing problems start.
Long-term control medications include:
- Inhaled corticosteroids
- Cromolyn, taken using a nebulizer
- Omalizumab (anti-IgE), given as an injection
- Inhaled long-acting beta2-agonists
- Leukotriene modifiers, taken by mouth
- Theophylline, taken by mouth
Quick-relief medications include:
- Inhaled long-acting beta2-agonists
Asthma At A Glance
- Asthma is a chronic lung disorder that can make breathing difficult. It causes inflammation, swelling, and narrowing of the airways (bronchial tubes).
- About 25 million people in the U.S have asthma; 7 million of those are children.
- Asthma involves narrowing of the airways caused by three major factors: inflammation, bronchospasm, and hyperreactivity.
- Allergy plays a role in some, but not all, asthma patients.
- Allergens and irritants can cause asthma attacks.
- Asthma symptoms include shortness of breath,
- Asthma is diagnosed based physical exam, patient history, and confirmed with breathing tests.
- The best way to manage asthma is to try to avoid triggers such as allergens or irritants.
- Medications can reverse or prevent bronchospasm in patients with asthma.