Asthma is a chronic respiratory condition in which inflammatory airway constriction reduces the flow of air to the lungs, causing shortness of breath, wheezing and coughing. An asthma attack is a physiological process that occurs when a person with asthma comes into contact with a triggering substance. During an asthma attack, a chain of events is triggered, leading to airway constriction and breathing difficulty. People with asthma typically use medication to reduce the frequency and severity of attacks, and they use additional medication during attacks to prevent airways from becoming dangerously constricted.
Globally, asthma is the most common chronic disease of childhood. It is a common chronic disease across all age groups. An estimated 2 percent to 10 percent of the population is affected in industrialized nations. Worldwide, approximately 300 million people have the disease.
Several types of cells of the immune system, including mast cells, macrophages, neutrophils and eosinophils, play a role in the pathophysiology of asthma. These cells are involved in mediating acute and chronic inflammatory reactions, and they are central to the development of asthma and the inflammation that occurs during an asthma attack. Many substances can trigger an attack, including dust, pollen, mold, smoke, animal hair, animal dander and chemical fumes.
When someone with asthma comes into contact with a trigger substance, his or her immune system is triggered to mount a reaction that is virtually immediate. This reaction is an asthma attack, during which the immune reaction to the trigger substance causes the airways to swell and become narrower. Several immune cell types secrete pro-inflammatory substances, and the airway muscles begin to contract strongly, causing greater constriction. At the same time, airway cells begin producing excess mucus, which further narrows the airways and causes congestion. All of these events serve to constrict and congest the airways and make breathing difficult.
The goals of asthma treatment are to reduce the frequency of attacks and reduce the severity of attacks that do occur. This is achieved with medications such as anti-inflammatories and bronchodilators. Anti-inflammatory medications help reduce chronic symptoms of asthma, such as coughing and wheezing, by reducing inflammation. During an asthma attack, bronchodilators are used to widen the airways and make breathing easier.
Many people with asthma find that attacks are more frequent in the mornings or evenings. In addition, someone with asthma is at greater risk of an attack if he or she has a respiratory infection. The frequency of attacks can be reduced by avoiding known trigger substances. In particular, avoiding cigarette smoke is an important preventative measure for children with asthma.