Occupational
Main article: Occupational asthma
Asthma as a result of (or worsened by) workplace exposures, is a commonly reported occupational disease.[86] Many cases however are not reported or recognized as such.[87][88]It is estimated that 5–25% of asthma cases in adults are work–related. A few hundred different agents have been implicated with the most common being: isocyanates, grain and wood dust, colophony, soldering flux, latex, animals, and aldehydes. The employment associated with the highest risk of problems include: those who spray paint, bakers and those who process food, nurses, chemical workers, those who work with animals, welders, hairdressers and timber workers.[86]
Differential diagnosis
Many other conditions can cause symptoms similar to those of asthma. In children, other upper airway diseases such as allergic rhinitis and sinusitis should be considered as well as other causes of airway obstruction including: foreign body aspiration, tracheal stenosis or laryngotracheomalacia, vascular rings, enlarged lymph nodes or neck masses. In adults, COPD, congestive heart failure, airway masses, as well as drug-induced coughing due to ACE inhibitors should be considered. In both populations vocal cord dysfunctionmay present similarly.[89]
Chronic obstructive pulmonary disease can coexist with asthma and can occur as a complication of chronic asthma. After the age of 65 most people with obstructive airway disease will have asthma and COPD. In this setting, COPD can be differentiated by increased airway neutrophils, abnormally increased wall thickness, and increased smooth muscle in the bronchi. However, this level of investigation is not performed due to COPD and asthma sharing similar principles of management: corticosteroids, long acting beta agonists, and smoking cessation.[90] It closely resembles asthma in symptoms, is correlated with more exposure to cigarette smoke, an older age, less symptom reversibility after bronchodilator administration, and decreased likelihood of family history of atopy.[91][92]
Prevention
The evidence for the effectiveness of measures to prevent the development of asthma is weak.[93] 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.[93] Early pet exposure may be useful.[94] Results from exposure to pets at other times are inconclusive[95] and it is only recommended that pets be removed from the home if a person has allergic symptoms to said pet.[96] Dietary restrictions during pregnancy or when breast feeding have not been found to be effective and thus are not recommended.[96] Reducing or eliminating compounds known to sensitive people from the work place may be effective.[86]
Management
While there is no cure for asthma, symptoms can typically be improved.[97] 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 treament according to changes in symptoms.[98]
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.[99][100]
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.[9]
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.[101][102] Cigarette smoking and second-hand smoke (passive smoke) may reduce the effectiveness of medications such as corticosteroids.[103] Dust mite control measures, including air filtration, chemicals to kill mites, vacuuming, mattress covers and others methods had no effect on asthma symptoms.
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.[99]
• Short-acting beta2-adrenoceptor agonists (SABA), such as salbutamol (albuterol USAN) are the first line treatment for asthma symptoms.[9]
• Anticholinergic medications, such as ipratropium bromide, provide additional benefit when used in combination with SABA in those with moderate or severe symptoms.[9] Anticholinergic bronchodilators can also be used if a person cannot tolerate a SABA.[72]
• Older, less selective adrenergic agonists, such as inhaled epinephrine, have similar efficacy to SABAs.[104] They are however not recommended due to concerns regarding excessive cardiac stimulation.[105]
• Corticosteroids are generally considered the most effective treatment available for long-term control.[99] Inhaled forms such asbeclomethasone are usually used except in the case of severe persistent disease, in which oral corticosteroids may be needed.[99] It is usually recommended that inhaled formulations be used once or twice daily, depending on the severity of symptoms.[106]
• 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.[107] In children this benefit is uncertain.[107][108] When used without steroids they increase the risk of severe side-effects[109] and even with corticosteroids they may slightly increase the risk.[110][111]
• Leukotriene antagonists (such as montelukast and zafirlukast) may be used in addition to inhaled corticosteroids, typically also in conjunction with LABA.[99] Evidence is insufficient to support use in acute exacerbations.[112][113] In children under five years of age, they are the preferred add-on therapy after inhaled corticosteroids.[114]
• Mast cell stabilizers (such as cromolyn sodium) are another non-preferred alternative to corticosteroids.[99]
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 or not a difference exists in those severe symptomatology.[115]
Adverse effects
Long-term use of inhaled corticosteroids at conventional doses carries a minor risk of adverse effects.[116] Risks include the development of cataracts and a mild regression in stature.[116][117]
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%.[118]
• Magnesium sulfate intravenous treatment has been shown to provide a bronchodilating effect when used in addition to other treatment in severe acute asthma attacks.[10][119]
• Heliox, a mixture of helium and oxygen, may also be considered in severe unresponsive cases.[10]
• Intravenous salbutamol is not supported by available evidence and is thus used only in extreme cases.[118]
• Methylxanthines (such as theophylline) were once widely used, but do not add significantly to the effects of inhaled beta-agonists.[118] Their use in acute exacerbations is controversial.[120]
• 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.[121]
For those with severe persistent asthma not controlled by inhaled corticosteroids and LABAs bronchial thermoplasty may be an option.[122] It involves the delivery of controlled thermal energy to the airway wall during a series of bronchoscopies.[122] While it may increase exacerbation frequency in the first few months it appears to decrease the subsequent rate. Effects beyond one year are unknown.[123] Evidence suggests that sublingual immunotherapy in those with both allergic rhinitis and asthma improve outcomes.[124]
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.[125][126]There is little data to support the effectiveness of most of these therapies. Evidence is insufficient to support the usage of Vitamin C.[127] Acupuncture is not recommended for the treatment as there is insufficient evidence to support its use.[128][129] Air ionisers show no evidence that they improve asthma symptoms or benefit lung function; this applied equally to positive and negative ion generators.[130]
"Manual therapies", including osteopathic, chiropractic, physiotherapeutic and respiratory therapeutic maneuvers, have insufficient evidence to support their use in treating asthma.[131] The Buteyko breathing technique for controlling hyperventilation may result in a reduction in medications use however does not have any effect on lung function.[100]Thus an expert panel felt that evidence was insufficient to support its use.[128]
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