ASTHMA

Asthma (from the Greek άσθμα, ásthma, "panting") is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm.[1] Symptoms include wheezing, coughing, chest tightness, and shortness of breath.[2] Asthma is clinically classified according to the frequency of symptoms, forced expiratory volume in 1 second (FEV1), and peak expiratory flow rate .[3] Asthma may also be classified as atopic (extrinsic) or non- atopic (intrinsic). [4] It is thought to be caused by a combination of genetic and environmental factors. [5] Treatment of acute symptoms is usually with an inhaled short-acting beta-2 agonist (such as salbutamol).[6] Symptoms can be prevented by avoiding triggers, such as allergens[7] and irritants, and by inhaling corticosteroids. [8]Leukotriene antagonists are less effective than corticosteroids and thus less preferred.[9] Its diagnosis is usually made based on the pattern of symptoms and/or response to therapy over time. [10] The prevalence of asthma has increased significantly since the 1970s. As of 2010, 300 million people were affected worldwide. [11] In 2009 asthma caused 250,000 deaths globally. [12] Despite this, with proper control of asthma with step down therapy, prognosis is generally good. [13] Classification Asthma is defined by the Global Initiative for Asthma as "a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role. The chronic inflammation is associated with airway hyperresponsiveness that leads to recurrent episodes of wheezing, breathlessness, chest tightness and coughing particularly at night or in the early morning. These episodes are usually associated with widespread, but variable airflow obstruction within the lung that is often reversible either spontaneously or with treatment". [14] Clinical classification of severity [3] Severity in patients ≥ 12 years of age [15] Symptom frequency Night time symptoms %FEV 1 of predicted FEV 1 Variability Use of short- acting beta 2 agonist for symptom control (not for prevention of EIB) Intermittent ≤2 per week ≤2 per month ≥80% <20% ≤2 days per week Mild persistent >2 per week but not daily 3–4 per month ≥80% 20–30% >2 days/ week but not daily Moderate persistent Daily >1 per week but not nightly 60–80% >30% Daily Severe persistent Throughout the day Frequent (often 7×/ week) <60% >30% Several times per day Asthma is clinically classified according to the frequency of symptoms, forced expiratory volume in 1 second (FEV1), and peak expiratory flow rate.[3] Asthma may also be classified as atopic (extrinsic) or non-atopic (intrinsic), based on whether symptoms are precipitated by allergens (atopic) or not (non-atopic). [4] While asthma is classified based on severity, at the moment there is no clear method for classifying different subgroups of asthma beyond this system. [16] Finding ways to identify subgroups that respond well to different types of treatments is a current critical goal of asthma research.[16] Although asthma is a chronic obstructive condition, it is not considered as a part of chronic obstructive pulmonary disease as this term refers specifically to combinations of disease that are irreversible such as bronchiectasis, chronic bronchitis, and emphysema . [15] Unlike these diseases, the airway obstruction in asthma is usually reversible; however, if left untreated, the chronic inflammation of the lungs during asthma can become irreversible obstruction due to airway remodeling. [17] In contrast to emphysema , asthma affects the bronchi, not the alveoli .[18] Brittle asthma Main article: Brittle asthma Brittle asthma is a term used to describe two types of asthma, distinguishable by recurrent, severe attacks. [19] Type 1 brittle asthma refers to disease with wide peak flow variability, despite intense medication. Type 2 brittle asthma describes background well-controlled asthma, with sudden severe exacerbations . [19] Asthma attack An acute asthma exacerbation is commonly referred to as an asthma attack. The classic symptoms are shortness of breath, wheezing, and chest tightness.[20] While these are the primary symptoms of asthma,[21] some people present primarily with coughing, and in severe cases, air motion may be significantly impaired such that no wheezing is heard. [19] Signs which occur during an asthma attack include the use of accessory muscles of respiration (sternocleidomastoid and scalene muscles of the neck), there may be a paradoxical pulse (a pulse that is weaker during inhalation and stronger during exhalation), and over- inflation of the chest. [22] A blue color of the skin and nails may occur from lack of oxygen. [23] In a mild exacerbation the peak expiratory flow rate (PEFR) is ≥200 L/min or ≥50% of the predicted best. [24] Moderate is defined as between 80 and 200 L/min or 25% and 50% of the predicted best while severe is defined as ≤ 80 L/min or ≤25% of the predicted best.[24] Status asthmaticus Main article: Status asthmaticus Status asthmaticus is an acute exacerbation of asthma that does not respond to standard treatments of bronchodilators and steroids. Nonselective beta blockers (such as Timolol) have caused fatal status asthmaticus.[25] Exercise-induced Main article: Exercise-induced asthma A diagnosis of asthma is common among top athletes. One survey of participants in the 1996 Summer Olympic Games, in Atlanta , Georgia, U.S., showed that 15% had been diagnosed with asthma, and that 10% were on asthma medication.[26] There appears to be a relatively high incidence of asthma in sports such as cycling , mountain biking, and long-distance running, and a relatively lower incidence in weightlifting and diving. It is unclear how much of these disparities are from the effects of training in the sport. [26][27] Exercise-induced asthma can be treated with the use of a short-acting beta2 agonist. [15] Occupational Main article: Occupational asthma Asthma as a result of (or worsened by) workplace exposures is a commonly reported occupational respiratory disease. Still most cases of occupational asthma are not reported or are not recognized as such. Estimates by the American Thoracic Society (2004) suggest that 15–23% of new-onset asthma cases in adults are work related.[28] In one study monitoring workplace asthma by occupation, the highest percentage of cases occurred among operators, fabricators, and laborers (32.9%), followed by managerial and professional specialists (20.2%), and in technical, sales, and administrative support jobs (19.2%). Most cases were associated with the manufacturing (41.4%) and services (34.2%) industries.[28] Animal proteins, enzymes , flour, natural rubber latex, and certain reactive chemicals are commonly associated with work-related asthma. When recognized, these hazards can be mitigated, dropping the risk of disease. [29] Signs and symptoms Common symptoms of asthma include wheezing, shortness of breath , chest tightness and coughing, and use of accessory muscle. Symptoms are often worse at night or in the early morning, or in response to exercise or cold air.[30] Some people with asthma only rarely experience symptoms, usually in response to triggers, whereas other may have marked persistent airflow obstruction. [31] Gastro-esophageal reflux disease Gastro-esophageal reflux disease coexists with asthma in 80% of people with asthma, with similar symptoms. Various theories say that asthma could facilitate GERD and/or viceversa. The first case could be due to the effect of change in thoracic pressures, use of antiasthma drugs, could facilitate the passage of the gastric content back into the oesophagus by increasing abdominal pressure or decreasing the lower esophageal sphincter. The second by promoting bronchoconstriction and irritation by chronic acid aspiration, vagally mediated reflexes and others factors that increase bronchial responsiveness and irritation.