Asthma is a common long term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include episodes of wheezing, coughing, chest tightness, and shortness of breath. These episodes may occur a few times a day or a few times per week. Depending on the person they may become worse at night or with exercise.
Asthma is thought to be caused by a combination of genetic and environmental factors. Environmental factors include exposure to air pollution and allergens.[ Other potential triggers include medications such as aspirin and beta blockers. Diagnosis is usually based on the pattern of symptoms, response to therapy over time, and spirometry. Asthma is classified according to the frequency of symptoms, forced expiratory volume in one second (FEV1), and peak expiratory flow rate. It may also be classified as atopic or non-atopic where atopy refers to a predisposition toward developing a type 1 hypersensitivity reaction.
There is no cure for asthma. Symptoms can be prevented by avoiding triggers, such as allergens and irritants, and by the use of inhaled corticosteroids. Long-acting beta agonists (LABA) or antileukotriene agents may be used in addition to inhaled corticosteroids if asthma symptoms remain uncontrolled. Treatment of rapidly worsening symptoms is usually with an inhaled short-acting beta-2 agonist such as salbutamol and corticosteroids taken by mouth. In very severe cases, intravenous corticosteroids, magnesium sulfate, and hospitalization may be required.
In 2013, 242 million people globally had asthma up from 183 million in 1990. It caused about 489,000 deaths in 2013, most of which occurred in the developing world. It often begins in childhood. The rates of asthma have increased significantly since the 1960s.Asthma was recognized as early as Ancient Egypt. The word asthma is from the Greek ἅσθμα, ásthma which means "panting".
People with a family history of allergies or asthma are more prone to developing asthma. Many people with asthma also have allergies. This is called allergic asthma.
Occupational asthma is caused by inhaling fumes, gases, dust or other potentially harmful substances while on the job.
Childhood asthma impacts millions of children and their families. In fact, the majority of children who develop asthma do so before the age of five.
There is no cure for asthma, but once it is properly diagnosed and a treatment plan is in place you will be able to manage your condition, and your quality of life will improve.
An allergist / immunologist is the best qualified physician in diagnosing and treating asthma. With the help of your allergist, you can take control of your condition and participate in normal activities.
Asthma is characterized by recurrent episodes of wheezing, shortness of breath, chest tightness, and coughing. Sputum may be produced from the lung by coughing but is often hard to bring up. During recovery from an attack, it may appear pus-like due to high levels of white blood cells called eosinophils. Symptoms are usually worse at night and in the early morning or in response to exercise or cold air.[24] Some people with asthma rarely experience symptoms, usually in response to triggers, whereas others may have marked and persistent symptoms.
Causes
Asthma is caused by a combination of complex and incompletely understood environmental and genetic interactions. These factors influence both its severity and its responsiveness to treatment. It is believed that the recent increased rates of asthma are due to changing epigenetics (heritable factors other than those related to the DNA sequence) and a changing living environment. Onset before age 12 is more likely due to genetic influence, while onset after 12 is more likely due to environmental influence.Spirometry is recommended to aid in diagnosis and management. It is the single best test for asthma. If the FEV1 measured by this technique improves more than 12% following administration of a bronchodilator such as salbutamol, this is supportive of the diagnosis. It however may be normal in those with a history of mild asthma, not currently acting up. As caffeine is a bronchodilator in people with asthma, the use of caffeine before a lung function test may interfere with the results. Single-breath diffusing capacity can help differentiate asthma from COPD. It is reasonable to perform spirometry every one or two years to follow how well a person's asthma is controlled.
The methacholine challenge involves the inhalation of increasing concentrations of a substance that causes airway narrowing in those predisposed. If negative it means that a person does not have asthma; if positive, however, it is not specific for the disease.
Other supportive evidence includes: a ≥20% difference in peak expiratory flow rate on at least three days in a week for at least two weeks, a ≥20% improvement of peak flow following treatment with either salbutamol, inhaled corticosteroids or prednisone, or a ≥20% decrease in peak flow following exposure to a trigger. Testing peak expiratory flow is more variable than spirometry, however, and thus not recommended for routine diagnosis. It may be useful for daily self-monitoring in those with moderate to severe disease and for checking the effectiveness of new medications. It may also be helpful in guiding treatment in those with acute exacerbations.
Prevention
The evidence for the effectiveness of measures to prevent the development of asthma is weak.[117] Some show promise including: limiting smoke exposure both in utero and after delivery, breastfeeding, and increased exposure to daycare or large families but none are well supported enough to be recommended for this indication.[117] Early pet exposure may be useful.[118] Results from exposure to pets at other times are inconclusive[119] and it is only recommended that pets be removed from the home if a person has allergic symptoms to said pet.[120] Dietary restrictions during pregnancy or when breast feeding have not been found to be effective and thus are not recommended.[120] Reducing or eliminating compounds known to sensitive people from the work place may be effective.[104] It is not clear if annual influenza vaccinations effects the risk of exacerbations.[121] Immunization; however, is recommended by the World Health Organization.[122] Smoking bans are effective in decreasing exacerbations of asthma.[123]Management
While there is no cure for asthma, symptoms can typically be improved.[124] A specific, customized plan for proactively monitoring and managing symptoms should be created. This plan should include the reduction of exposure to allergens, testing to assess the severity of symptoms, and the usage of medications. The treatment plan should be written down and advise adjustments to treatment according to changes in symptoms.[125]The most effective treatment for asthma is identifying triggers, such as cigarette smoke, pets, or aspirin, and eliminating exposure to them. If trigger avoidance is insufficient, the use of medication is recommended. Pharmaceutical drugs are selected based on, among other things, the severity of illness and the frequency of symptoms. Specific medications for asthma are broadly classified into fast-acting and long-acting categories.[126][127]
Bronchodilators are recommended for short-term relief of symptoms. In those with occasional attacks, no other medication is needed. If mild persistent disease is present (more than two attacks a week), low-dose inhaled corticosteroids or alternatively, an oral leukotriene antagonist or a mast cell stabilizer is recommended. For those who have daily attacks, a higher dose of inhaled corticosteroids is used. In a moderate or severe exacerbation, oral corticosteroids are added to these treatments.[14]
Lifestyle modification
Avoidance of triggers is a key component of improving control and preventing attacks. The most common triggers include allergens, smoke (tobacco and other), air pollution, non selective beta-blockers, and sulfite-containing foods.[128][129] Cigarette smoking and second-hand smoke (passive smoke) may reduce the effectiveness of medications such as corticosteroids.[130] Laws that limit smoking decrease the number of people hospitalized for asthma.[131] Dust mite control measures, including air filtration, chemicals to kill mites, vacuuming, mattress covers and others methods had no effect on asthma symptoms.[51] Overall, exercise is beneficial in people with stable asthma.[132] Yoga could provide small improvements in quality of life and symptoms in people with asthma.[133]Medications
Medications used to treat asthma are divided into two general classes: quick-relief medications used to treat acute symptoms; and long-term control medications used to prevent further exacerbation.[126]Fast–acting
Salbutamol metered dose inhaler commonly used to treat asthma attacks.
- Short-acting beta2-adrenoceptor agonists (SABA), such as salbutamol (albuterol USAN) are the first line treatment for asthma symptoms.[14] They are recommended before exercise in those with exercise induced symptoms.[134]
- Anticholinergic medications, such as ipratropium bromide, provide additional benefit when used in combination with SABA in those with moderate or severe symptoms.[14] Anticholinergic bronchodilators can also be used if a person cannot tolerate a SABA.[87] If a child requires admission to hospital additional ipratropium does not appear to help over a SABA.[135]
- Older, less selective adrenergic agonists, such as inhaled epinephrine, have similar efficacy to SABAs.[136] They are however not recommended due to concerns regarding excessive cardiac stimulation.[137]
Long–term control
Fluticasone propionate metered dose inhaler commonly used for long-term control.
- Corticosteroids are generally considered the most effective treatment available for long-term control.[126] Inhaled forms such as beclomethasone are usually used except in the case of severe persistent disease, in which oral corticosteroids may be needed.[126] It is usually recommended that inhaled formulations be used once or twice daily, depending on the severity of symptoms.[138]
- Long-acting beta-adrenoceptor agonists (LABA) such as salmeterol and formoterol can improve asthma control, at least in adults, when given in combination with inhaled corticosteroids.[139] In children this benefit is uncertain.[139][140] When used without steroids they increase the risk of severe side-effects[141] and even with corticosteroids they may slightly increase the risk.[142][143]
- Leukotriene receptor antagonists (such as montelukast and zafirlukast) may be used in addition to inhaled corticosteroids, typically also in conjunction with a LABA.[13][126] Evidence is insufficient to support use in acute exacerbations.[144][145] In children they appear to be of little benefit when added to inhaled steroids,[146] and the same applies in adolescents and adults.[147] They are useful by themselves.[148] In those under five years of age, they were the preferred add-on therapy after inhaled corticosteroids by the British Thoracic Society in 2009.[149] A similar class of drugs, 5-LOX inhibitors, may be used as an alternative in the chronic treatment of mild to moderate asthma among older children and adults.[13][150] As of 2013 there is one medication in this family known as zileuton.[13]
- Mast cell stabilizers (such as cromolyn sodium) are another non-preferred alternative to corticosteroids.[126]
Delivery methods
Medications are typically provided as metered-dose inhalers (MDIs) in combination with an asthma spacer or as a dry powder inhaler. The spacer is a plastic cylinder that mixes the medication with air, making it easier to receive a full dose of the drug. A nebulizer may also be used. Nebulizers and spacers are equally effective in those with mild to moderate symptoms. However, insufficient evidence is available to determine whether a difference exists in those with severe disease.[151]Adverse effects
Long-term use of inhaled corticosteroids at conventional doses carries a minor risk of adverse effects.[152] Risks include the development of cataracts and a mild regression in stature.[152][153]Others
When asthma is unresponsive to usual medications, other options are available for both emergency management and prevention of flareups. For emergency management other options include:- Oxygen to alleviate hypoxia if saturations fall below 92%.[154]
- Oral corticosteroid are recommended with five days of prednisone being the same 2 days of dexamethasone.[155]
- Magnesium sulfate intravenous treatment increases bronchodilation when used in addition to other treatment in moderate severe acute asthma attacks.[15][156][157] In adults it results in a reduction of hospital admissions.[158]
- Heliox, a mixture of helium and oxygen, may also be considered in severe unresponsive cases.[15]
- Intravenous salbutamol is not supported by available evidence and is thus used only in extreme cases.[154]
- Methylxanthines (such as theophylline) were once widely used, but do not add significantly to the effects of inhaled beta-agonists.[154] Their use in acute exacerbations is controversial.[159]
- The dissociative anesthetic ketamine is theoretically useful if intubation and mechanical ventilation is needed in people who are approaching respiratory arrest; however, there is no evidence from clinical trials to support this.[160]
Alternative medicine
Many people with asthma, like those with other chronic disorders, use alternative treatments; surveys show that roughly 50% use some form of unconventional therapy.[165][166] There is little data to support the effectiveness of most of these therapies. Evidence is insufficient to support the usage of Vitamin C.[167] There is tentative support for its use in exercise induced brochospasm.[168]Acupuncture is not recommended for the treatment as there is insufficient evidence to support its use.[169][170] Air ionisers show no evidence that they improve asthma symptoms or benefit lung function; this applied equally to positive and negative ion generators.[171]
Manual therapies, including osteopathic, chiropractic, physiotherapeutic and respiratory therapeutic maneuvers, have insufficient evidence to support their use in treating asthma.[172] The Buteyko breathing technique for controlling hyperventilation may result in a reduction in medication use; however, the technique does not have any effect on lung function.[127] Thus an expert panel felt that evidence was insufficient to support its use.
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