What Is Asthma? Definition
Asthma is a chronic lung disorder that can make breathing difficult. It features narrow, inflamed airways (bronchial tubes). "Asthma" is an ancient Greek word meaning "short breath," and as the name implies, it can leave you gasping for air. One of the telltale signs of an asthma attacks is wheezing with difficulty breathing. Other asthma symptoms include chest tightness, coughing, and shortness of breath.
When the breathing tubes of the lungs become chronically inflamed, they can become sensitive to inhaled environmental allergens and irritants that can trigger asthma. These environmental triggers include pollen, pollution, and tobacco smoke. Exercise can also be an asthma trigger for some.
Who Gets Asthma?
About 25 million people in the U.S. have asthma; about 6 million of these are children. The condition affects men and women equally.
Asthma Can Be Deadly
Asthma causes over 14 million visits to doctors each year and nearly 2 million emergency room visits. And, tragically, asthma can kill. Most people who die from asthma are over age 50, but children sometimes die of the condition.
Asthma Treatment: Inhalers
Asthma inhalers and nebulizers have advantages over oral medications and injections in that they deliver medicine directly to your airways. They also have fewer side effects than other forms of asthma medication.
The most common treatment for asthma involves a device called an inhaler. An inhaler is a small device that delivers asthma medicine directly to the airways. Inhalers come in two types:
- Metered Dose Inhalers (MDI): MDIs are the most common type of inhaler. They spray medicine from the inhaler like an aerosol can.
- Dry powder inhalers: Dry powder inhalers deliver a powdered medicine that does not spray from the inhaler. Instead, the user must inhale the medicine quickly and forcefully.
Sometimes MDIs are used along with a device called a spacer. Spacers help coordinate breathing with the release of the asthma medicine, and use smaller droplets of medicine, making it easier to breath them in.
An inhaler cannot be used for babies and very young children. For them, a nebulizer can be used. Nebulizers are powered by electricity to turn asthma medicine into a fine mist.
The Respiratory System: How It Should Work
Respiration is the process by which our bodies inhale oxygen and express carbon dioxide. This process becomes more difficult during an asthmatic attack.
When you inhale, air passes through your windpipe (trachea). Meanwhile your diaphragm contracts and moves downward creating air space in your chest cavity. The air enters your lungs, passing through the bronchial tubes and finally into tiny air sacs (alveoli).
Oxygen from the air passes from the alveoli and into the bloodstream through tiny blood vessels called capillaries. Capillaries deliver this oxygen-rich blood to pulmonary veins, which pass it to the left side of your heart. The heart then pumps the oxygen-rich blood to the rest of your body.
When you exhale, air that is rich in carbon dioxide (CO2) passes out of your lungs, through your windpipe, and out your body through your nose and/or mouth.
How Does Asthma Affect Breathing?
During an asthma attack, airways become inflamed and sensitive. Swelling narrows the airways, making breathing difficult, often leading to panting and gasping fits. Three factors cause this narrowing:
- Hyperreactivity (Asthma Triggers)
Causes of Asthma: Inflammation
Inflammation is the main cause of airway narrowing during asthma episodes. It makes airways more swollen and sensitive. When airways are inflamed, air has a smaller passageway. In addition, the surrounding muscles of the airways may tighten during an asthma attack, further narrowing the opening for airflow.
When airways react to inflammation, they also produce more mucus. This thick, sticky liquid can clump together and also narrow air passages.
Moreover, certain allergy and inflammation cells (white blood cells, including eosinophils) accumulate at the site of the inflammation, causing tissue damage further narrowing airways. This chain reaction causes the breathing difficulty associated with an asthma attack.
What Causes Asthma? Bronchospasm
The larger tubes that split off from your trachea and into your lungs are called your bronchial tubes. These tubes are surrounded by muscles. When the muscles of your bronchial tubes contract in asthma, they obstruct your airways, a process referred to as bronchospasm.
Coughing and wheezing may be symptoms of bronchospasm, and bronchospasm can occur when the airways are irritated by cold air. Bronchospasm may come on suddenly. It can be treated by medicines called bronchodilators.
What Causes Asthma? Asthma Triggers
People with asthma may become overly sensitive (hyperreactive) to certain inhaled allergens or irritants. These are called triggers of asthma, and these triggers can cause inflammation and narrowing of your airways. This occurs because some people's bodies are immunologically inclined to overreact to certain substances. The precise substance that may cause such a reaction varies from person to person. In the next three slides, we'll review asthma triggers in more detail.
Asthma Trigger Types
Things that can initiate an asthma attack are referred to as "triggers." Not everyone with asthma has the same triggers. Triggers can be allergens or irritants. People with asthma need to learn what their triggers are to optimally manage and avoid them.
Recognizing and avoiding triggers can help you prevent further asthma attacks. Allergists and immunologists are medical doctors who specialize in helping patients identify irritants and allergies that cause problems like asthma. They can help develop a plan to avoid asthma triggers to optimize daily health.
Asthma Triggers: Allergens
Asthma can have both allergic and nonallergic triggers. Allergic asthma triggers include many allergens. Some of these allergens include:
- Some foods, including peanuts, egg, dairy, soy, and fish
Asthma Triggers: Irritants
Nonallergic asthma triggers include many irritants. Some of these come from environmental toxins, including tobacco smoke, smog, and various chemicals, dusts, and occupational gases. They can also come from medications, such as over-the-counter painkillers and beta-blockers. Sometimes respiratory infections can trigger asthma, and so can GERD. Exercise can also bring on asthma attacks.
Asthma Symptoms in Adults and Kids
Asthma can develop at any age. However, asthma does tend to start in children ages 2-6. At this age, asthma is commonly triggered by allergens such as dust mites, tobacco smoke, and dust mites. In young children, asthma may first be diagnosed as reactive airway disease (RAD).
Adults can also develop asthma, and only about 30% of adult-onset asthma triggers are related to allergies. 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 (extrinsic) asthma is the type triggered by an allergic reaction. This is an example of your immune system responding to an irritant. Allergic asthma is the most common form, affecting more than half of all sufferers. It can often be managed with medication, and tends to be less severe than other forms.
Types of Asthma: Non-Allergic (Intrinsic)
Non-allergic (intrinsic) asthma is caused by factors other than allergies, such as exercise, stress, inhaling cold air, smoke, viral infections, and other irritants. This type of asthma is less common, develops more often in adults, and is more difficult to treat than allergic (extrinsic) asthma. In many cases this type seems to be more severe.
Symptoms and Signs of Asthma
Different people experience asthma in different ways. When asthma is under control, you may have fewer symptoms or no symptoms. Symptoms of asthma are the same for both allergic and non-allergic types. They include
- Shortness of breath
- Chest tightness
- Heavy mucus production
Not everyone with asthma will experience every symptom, and the severity of symptoms can vary depending on the individual—even in an individual symptoms may vary over time.
Asthma: Mild to Severe
The National Asthma Education and Prevention Program classifies asthma based on a patient's symptoms and lung function tests into these four categories:
- Mild intermittent
- 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 excess mucus production. These can lead to symptoms such as
- Difficulty breathing
- Shortness of breath
- Interference with daily activities
Frequently, asthma attacks can be controlled with inhalers (inhaled bronchodilators). When that is ineffective, the patient should call 911 or be taken to an emergency room immediately. When asthma does not respond to initial treatment it can result in a life-threatening reaction called status asthmaticus.
Asthma Exams & Tests
There are several tests that can determine whether you have asthma and how severe it is. Lung (pulmonary) function tests measure how functional your lungs are. These may include spirometry or peak flow meter tests.
A bronchial challenge test helps the doctor determine how reactive your lungs are to environmental triggers. This testing includes a methacholine challenge test, a histamine challenge test, and bronchoprovocation.
Blood tests measure the IgE antibodies that are released during an allergic reaction. Other tests may be used to rule out other causes of shortness of breath, including acid reflux and sleep apnea. Sometimes chest x-rays or EKGs are performed to detect a foreign object in the lungs or another condition.
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:
- Montelukast, oral medicine that helps prevent wheezing and shortness of breath
- Inhaled corticosteroids
- Cromolyn, taken using a nebulizer or inhaler
- Omalizumab (anti-IgE), given as an injection
- Long-acting beta2-agonists (bronchodilators)
- Leukotriene modifiers, taken by mouth
- Theophylline, taken by mouth
Quick-relief medications include:
- Albuterol and other short-acting beta2-agonists (bronchodilators)
Common medications used with inhalers and nebulizers include the following three types:
- Inhaled Corticosteroids: Inhaled corticosteroids reduce airway inflammation. Sometimes these medicines are used even for people who don’t have any asthma symptoms, as they can help prevent future asthma attacks.
- Short-Acting Bronchodilators: Bronchodilators have no steroids. They work by relaxing the tiny muscles that can tighten airways during asthma attacks. Short-acting bronchodilators relieve asthma symptoms quickly.
- Long-Acting Bronchodilators: Long-acting bronchodilators are taken daily to help control asthma and prevent future asthma attacks. Types of long-acting bronchodilators include salmeterol and formoterol.
Asthma Recap: Fast Facts
- 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; 6 million of those are children.
- Asthma is diagnosed based on the physical exam and the patient's history. It is confirmed with breathing tests.
- Asthma is caused by three major factors: inflammation, bronchospasm, and hyperreactivity.
- Allergy plays a role in some, but not all asthma cases.
- Allergens and irritants can cause asthma attacks. When they do, they are called "triggers."
- The best way to manage asthma is to try to avoid triggers, which are different for everyone with asthma.
- Medications can reverse or prevent bronchospasm.