Asthma: An Overview
What is asthma?
Asthma is a disease of the bronchial tubes or airways of the lungs. Air is normally taken into the body through the nose and windpipe and into the bronchial tubes. At the end of these tubes are tiny air sacs (alveoli) that deliver fresh air (oxygen) to the blood. The air sacs also collect stale air (carbon dioxide), which is exhaled out of the body.
During normal breathing, the bands of muscle that surround the airways are relaxed and air moves freely. During an asthma episode or "attack," there are three main changes that stop air from moving easily through the airways:
- The bands of muscle that surround the airways tighten and make the airways narrow. This tightening is called bronchospasm.
- The lining of the airways becomes swollen or inflamed.
- The cells that line the airways produce more mucus, which is thicker than normal.
All of these factors - bronchospasm, inflammation, and mucus production - cause symptoms such as:
- Difficulty breathing
- Activity intolerance
What are the most common symptoms of asthma?
Not every person with asthma experiences the same symptoms in the same way. You may not have all of these symptoms, or you may have different symptoms at different times. Symptoms may also vary from one asthma episode to the next, being mild during one asthma episode and severe during another.
The most common symptoms include:
- Frequent coughing, especially at night
- Shortness of breath
- Chest tightness, pain, or pressure
Who is affected by asthma?
Asthma affects 22 million Americans, of which approximately 6 million are children under age 18. Asthma may occur at any age, although onset is more likely in younger individuals (people under age 40).
People who have a family history of asthma have an increased risk of developing the disease. Asthma is also more common in people who have allergies or who are exposed to tobacco smoke. However, anyone can develop asthma at any time. Some people may have asthma all of their lives, while others may develop it as adults.
What causes asthma?
Asthma is a problem in the airways, but we don't know exactly why. The airways in a person with asthma are very sensitive and react to many things, or "triggers." Contact with these triggers brings on asthma symptoms. Reactions to triggers are different for each person and vary from time to time. One of the most important parts of asthma control is avoiding triggers.
Common asthma triggers include:
- Infections (colds, viruses, flu, sinus infections)
- Exercise (very common in children)
- Weather (cold air, changes in temperature)
- Tobacco smoke and air pollution
- Allergens (dust mites, pollens, pets, mold spores, foods, and cockroaches)
- Strong odors from chemical products
- Strong emotions such as crying or laughing hard
How is asthma diagnosed?
To diagnose asthma, your physician will first review your medical history, family history, and symptoms. Your physician will be interested in any past history of breathing problems you may have had, as well as a family history of asthma, allergies, eczema, or other lung disease. It is important that you describe your symptoms in detail (cough, wheeze, shortness of breath, chest tightness) including when and how often these symptoms have been occurring.
The doctor will also perform a physical examination and listen to your heart and lungs. There are numerous tests your physician may perform including pulmonary function tests, peak expiratory flow, methacholine challenge tests, allergy tests, blood tests, and chest and sinus x-rays. All of these tests help your physician determine if asthma is indeed present and if there are other conditions affecting it.
How is asthma classified?
Asthma is classified into four categories based upon frequency of symptoms and objective measures, such as peak flow measurements and/or spirometry results. These categories are:
- Mild intermittent
- Mild persistent
- Moderate persistent
- Severe persistent
Your physician will determine the severity and control of your asthma based on the frequency of daytime and nighttime symptoms and lung function tests. It is important to note that a person's asthma symptoms can fluctuate from one category to another.
Mild intermittent asthma
- Symptoms occur less that two times a week and night-time symptoms occur less than two times per month
- Asthma episodes are brief (few hours to a few days)
- Lung function tests are > 80% of predicted
Mild persistent asthma
- Symptoms occur more than two times per week but not every day
- Lung function tests are > 80% of predicted
Moderate persistent asthma
- Symptoms occur daily
- Asthma episodes affect activity, occur more than one times per week and may last for days
- There is a reduction in lung function, with a lung function test range of 60% to 80% of predicted
Severe persistent asthma
- Symptoms occur continuously with frequent night-time symptoms
- Activities are limited
- Lung function is decreased to less than 60%
How is asthma treated?
Asthma can be controlled, but not cured. Having frequent symptoms, trouble sleeping, or difficulty completing tasks is not normal! Good asthma control will stop these symptoms and end visits to the emergency room and hospital.
Properly using medication, as prescribed by your doctor, is the basis of good asthma control, in addition to avoiding triggers and monitoring daily asthma symptoms. There a two main types of asthma medications:
- Anti-inflammatories: These are the most important type of medications for most people with asthma. Anti-inflammatory medications reduce swelling and mucus production in the airways. As a result, airways are less sensitive and less likely to react to triggers. These medications need to be taken daily and may need to be taken for several weeks before they will begin to control asthma. Anti-inflammatories lead to a reduction in symptoms, better airflow, less sensitive airways, less airway damage, and fewer asthma episodes. If taken every day, they control or prevent asthma symptoms.
- Bronchodilators: These medications relax the muscle bands that tighten around the airways. This action rapidly opens the airways, letting more air in and out of the lungs and improving breathing. Bronchodilators also help clear mucus from the lungs. As the airways open, the mucus moves more freely and can be coughed out more easily. In short-acting forms, bronchodilators relieve or stop asthma symptoms and are very helpful during an asthma episode. In long-acting forms, bronchodilators provide control of asthma symptoms and prevent asthma episodes.
Asthma medications can be taken in a variety of ways. Inhaling the medications -- using a metered dose inhaler, dry powder inhaler, or nebulizer -- are one way of taking asthma medications. Oral medications (pills or liquids you swallow) may also be prescribed.
An important part of treatment is keeping track of how well the lungs are functioning. Asthma symptoms are monitored using a peak flow meter. The meter can alert you to changes in the airways that may be a sign of worsening asthma. By taking daily peak flow readings, you can learn when to adjust medications to keep asthma under good control. Your doctor can also use this information to adjust your treatment plan.
Asthma action plan
Based on your history and the severity of asthma, your physician will develop a care plan called an asthma action plan. The asthma action plan describes when and how to use asthma medications, actions to take when asthma worsens, and when to seek emergency care. Make sure you understand this plan; if not, ask your asthma care provider any questions you may have.
Your asthma action plan is one of the keys to successfully controlling asthma. Keep it readily available to remind you of the daily asthma management plan, as well as to guide you when symptoms occur.
Goals of asthma therapy
Listed below are the goals of asthma treatment. If you are unable to achieve all of these goals it means asthma is not in good control. You should contact your asthma care provider for advice.
- Live an active, normal life
- Prevent chronic and troublesome symptoms
- Attend work or school every day
- Perform daily activities without difficulty
- Stop urgent visits to the doctor, emergency room, or hospital
- Use and adjust medications to control asthma with little or no side effects
By learning about asthma and how it can be controlled, you take an important step toward managing this disease. We encourage you to work closely with your asthma care team to learn all you can about your asthma, how to avoid triggers, what your medications do and how to correctly take them. With proper care, you can live free of asthma symptoms and maintain a normal, healthy lifestyle.