Asthma is a disease of the bronchial tubes, or airways of the lungs, characterized by tightening of these airways. It is a chronic condition; people with asthma live with it every day and for their whole lives.

There are Three Major Features of Asthma:

  1. Airway Obstruction. During normal breathing, the bands of muscle that surround the airways are relaxed, and air moves freely. But in people with asthma, allergy-causing substances and environmental triggers make the bands of muscle surrounding the airways tighten, and air cannot move freely. Less air causes a person to feel short of breath, and the air moving through the tightened airways causes a whistling sound known as wheezing.
    (Fortunately, this airway narrowing is reversible, a feature that distinguishes asthma from other lung diseases such as bronchitis or emphysema.)
  2. Inflammation. People with asthma have red and swollen bronchial tubes. This inflammation is thought to contribute greatly to the long-term damage that asthma can cause to the lungs. And, therefore, treating this inflammation is key to managing asthma in the long run.
  3. Airway Irritability. The airways of people with asthma are extremely sensitive. The airways tend to overreact and narrow due to even the slightest triggers such as pollen, animal dander, dust or fumes.

Who Gets Asthma?

Asthma affects 12-15 million Americans, including approximately 10%-12% of children under age 18. Asthma may occur at any age, although it's more common in younger individuals (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.

What Causes Asthma?

People with asthma have very sensitive airways that react to many different things in the environment called "triggers." Contact with these triggers cause asthma symptoms to start or worsen. The following are common triggers for asthma:

What Are the Symptoms of Asthma?

People with asthma experience symptoms when their airways tighten, swell up, or fill with mucus. Common symptoms include:

To diagnose asthma, your doctor will review your medical history, family history, and symptoms. He or she will be interested in any history of breathing problems you may have had, as well as a family history of asthma, allergies, a skin disease called eczema, or other lung conditions. It is important that you describe your symptoms in detail (coughing, wheezing, shortness of breath, chest tightness), including when and how often they occur.

There are many tests your doctor may perform, including pulmonary function tests, allergy tests, blood tests, and chest and sinus X-rays. All of these tests help your doctor determine if asthma is indeed present and if there are other conditions affecting it.

Your doctor will also perform a physical examination including listening to your heart and lungs.

Pulmonary Function Tests

Pulmonary function tests (or lung function tests) include numerous procedures to assess lung function. The two most common lung function tests used to diagnose asthma are spirometry and methacholine challenge tests.

Spirometry. This is a simple breathing test that measures how much and how fast you can blow air out of your lungs. It is often used to determine the amount of airway obstruction you have. Spirometry can be done before and after you inhale a short-acting medication called a bronchodilator, such as Ventolin or Proventil. The bronchodilator causes your airways to expand allowing for air to pass through freely. By doing this, your doctor can determine if the airway obstruction is reversible with medication -- an indicator of asthma.

The test may also be done at future doctor visits to monitor your progress and help your doctor determine if and how to adjust your treatment plan.

Methacholine Challenge Test. This test is more commonly used in adults than children. It may be performed if your symptoms and screening spirometry do not clearly or convincingly establish a diagnosis of asthma.

Methacholine is an agent that, when inhaled, causes the airways to spasm and narrow if asthma is present. During this test, you inhale increasing amounts of methacholine aerosol mist before and after spirometry. The methacholine test is considered positive, meaning asthma is present, if the lung function drops by at least 20%. A bronchodilator is always administered at the end of the test to reverse the effects of the methacholine.

Preparing For Pulmonary Function Tests

Ask your doctor if there is anything you need to do to prepare for spirometry.
Before taking a methacholine challenge test, be sure to tell your doctor if you have recently had a viral infection, like a cold, or any shots or immunizations, since these may affect the test's results.

Other General Preparations to Follow Before The Test Include:

Chest X-Ray

An X-ray is an image of the body that is created by using low doses of radiation reflected on special film or a fluorescent screen. X-rays can be used to diagnose a wide range of conditions, from bronchitis to a broken bone. Your doctor may perform an X-ray exam on you in order to see the structures inside your chest, including the heart, lungs, and bones. By viewing your lungs, your doctor can see if asthma is causing your symptoms.

Evaluation of the Sinuses

The presence of nasal polyps or sinusitis may make asthma harder to treat and control. Sinusitis, also called sinus infection, is an inflammation or swelling of the sinuses due to infection. When the sinuses become blocked and filled with fluid, bacteria grow, causing infection and inflammation. Your doctor may order a special sinus X-ray, called a CT scan, to evaluate your sinuses if he suspects an infection. Once acute sinusitis is diagnosed, you will be treated with antibiotics for at least 10-12 days.
Evaluation for Heartburn and GERD

Gastroesophageal reflux disease, commonly called GERD is another condition that may worsen asthma. If your doctor suspects this problem, he or she may recommend specific tests to look for it.

Evaluation for Allergies

Allergy testing may be recommended to identify any allergies that trigger asthma symptoms.

Judging the Severity of Asthma

Based on these tests, your doctor may determine that you have asthma. The next step is for the doctor to determine the severity of asthma as this will help decide treatment. There are 4 types of asthma. They are:

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