Know about asthma

Asthma most of the time is not a life threatening disease but it can make your life miserable and sometimes it is lethal. It happens due to certain changes in your airways that prevents enough air to enter or exit from your lungs. It is an emergency and demands quick management and life-long follow up.

Asthma is a medical condition characterized by hypersentivity of airways to different kinds of triggers e.g. dust, pollens, cold air, stress, heavy excercise, sulphur dioxide and other irritant gases, some drugs like β-blockes etc. As a result of this the airways get narrows and airflow is obstructed. Many people suffering from asthma have a genetic tendency to develop allergic conditions like allergic rhinitis or atopic dermatitis. This is called atopy.

Development of asthma has a particular pathology. Some of the cells which perform a protective function in our body become hyperactive in the airway mucosa of asthmatics. These cells are eosinophils and T-lymphocytes. Mucosal mast cells also get activated. This condition is called Asthma inflamation. The basement membrane of the airway mucosa gets thickened due to deposition of collagen in sub-epithelial region of the basement membrane. Thickening of basement membrane and swelling of mucosa (called oedema) along with bronchoconstriction leads to obstruction of airways. Epithelium is often shed off and along with mucous plug clogs airways which makes the condition very severe.

An important problem for physicians and pathologist had been how the inflammatory cells like eosinophils, T-lymphocytes and mast cells interact among themselves which ultimately results in inflammation. Identifying these mediators became important because if these could be inactivated then the inflammatory process could be stopped or at least slowed. Not all mediators have been identified but we already know about histamin, leukotriene, cytokines, kinins and many others. They lead to bronchospasm, mucous secretion, exudation of plasma and ultimately airway remodelling.

Since there is no permanent cure for asthma aim of treatment is to alleviate severe emergencies and then to reduce symptoms as much as possible. But since the disease develops gradually medicines must be used juduciously. Long term management of asthma is done with bronchodialators. These drugs work on the smooth muscles of bronchus and relieve bronchoconstriction. β2-agonists are drugs that works on β2- adrenergic receptors of bronchial smooth muscles which get relaxed thus relieving bronchoconstriction. β2-agonists are of two types- short acting and long-acting. Albuterol and terbutaline are short acting beta2 agonists. They are used to relieve asthma symptoms quickly but their effect does not last for long. For that long acting β2 agonists like salmeterol or formoterol are used. Anti-cholinergics like ipratropium and tiotropium are used to reduce mucous secretion and bronchoconstriction but they are less effective that bronchodialators. Theophyllines and aminophyllines are less used as bronchodilators now since they have adverse effect on heart. Inhaled corticosteroides are by far the most effective therapy for asthma. They reduce inflammation by reducing the number of active inflammatory cells. They are given intravenously in acute severe asthma, can be taken orally and for long term management are taken through an inhaler. Prednisolone and budesonide are steroids that are given intravenously or orally. Fluticasone is inhaled.

Several drugs have been manufactured that inhibit the mediators of bronchial inflammation. These are anti-leukotrienes like montelukast or zafirlukast, anti-IgE drugs like omalizumab, cromolyn sodium that inhibit mast cells etc.