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Medical Author:

George Schiffman, MD, FCCP

George Schiffman, MD, FCCP

Dr. Schiffman received his B.S. degree with High Honors in biology from Hobart College in 1976. He then moved to Chicago where he studied biochemistry at the University of Illinois, Chicago Circle. He attended Rush Medical College where he received his M.D. degree in 1982 and was elected to the Alpha Omega Alpha Medical Honor Society. He completed his Internal Medicine internship and residency at the University of California, Irvine.

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Medical Author:

Alan Szeftel, MD

Alan Szeftel, MD

Dr. Szeftel received his Medical Degree from the University of Cape Town Medical School in South Africa. His clinical training was at Groote Schuur Hospital. He completed his Internal Medicine residency at Brigham & Women's Hospital and Harvard University. He is board certified in Internal Medicine, Pulmonary Diseases, Critical Care and Allergy and Immunology.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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In this Article

• Myths, facts, and statistics about asthma
• What is asthma?
• From the past to the present
• The scope of the problem
• Normal bronchial tubes
• How does asthma affect breathing?
• The importance of inflammation
• Which triggers cause an asthma attack?
• The many faces of asthma
• Types: allergic (extrinsic) and nonallergic (intrinsic) asthma
• Typical asthma symptoms and signs
• Acute asthma attack
• What medications are used in the treatment of asthma?
• Asthma At A Glance
• Asthma FAQs
• Patient Comments: Asthma - Symptoms
• Patient Comments: Asthma - Effective Treatments
• Find a local Asthma & Allergy Specialist in your town
• Asthma Index

Asthma is now the most common chronic illness in children, affecting one in every 15. In North America, 5% of adults are also afflicted. In all, there are about 1 million Canadians and 15 million Americans who suffer from this disease.

The number of new cases and the yearly rate of hospitalization for asthma have increased about 30% over the past 20 years. Even with advances in treatment, asthma deaths among young people have more that doubled.

Allergy fact

There are about 5,000 deaths annually from asthma in the U.S. and about 500 deaths per year in Canada.

Before we can appreciate how asthma affects the bronchial airways, we should first take a quick look at the structure and function of normal bronchial tubes.

The air we breathe in through our nose is processed to prepare it for presentation to our lower respiratory tract. This air is moistened, heated, and cleansed prior to passage through the vocal cords (larynx) and into the windpipe (trachea). Dry or cold air presented to our trachea can cause coughing and wheezing as a normal response to this type of irritation. The air then enters the lungs by way of two large air passages (bronchi), one for each lung. The bronchi divide within each lung into smaller and smaller air tubes (bronchioles), just like branches of an inverted tree. Inhaled air is brought through these airways to the millions of tiny air sacs (alveoli) that are contained in the lungs. Oxygen (O₂) passes from the air sacs into the bloodstream through numerous tiny blood vessels called capillaries. Similarly, the body's waste product, carbon dioxide (CO₂), is returned to the air sacs and then eliminated upon each exhalation.

Normal bronchial tubes allow rapid passage of air in and out of the lungs to ensure that the levels of O₂ and CO₂ remain constant in the bloodstream. The outer walls of the bronchial tubes are surrounded by smooth muscles that contract and relax automatically with each breath. This allows the required amount of air to enter and exit the lungs to achieve this normal exchange of O₂ and CO₂. The contraction and relaxation of the bronchial smooth muscles are controlled by two different nervous systems that work in harmony to keep the airways open.

The inner lining of the bronchial tubes, called the bronchial mucosa, contains: (1) mucus glands that produce just enough mucus to properly lubricate the airways; and (2) a variety of so-called inflammatory cells, such as eosinophils, lymphocytes, and mast cells. These cells are designed to protect the bronchial mucosa from the microorganisms, allergens, and irritants we inhale, and which can cause the bronchial tissue to swell. Remember, however, that these inflammatory cells are also important players in the allergic reaction. Therefore, the presence of these cells in the bronchial tubes causes them to be a prime target for allergic inflammation.