Data sharing not applicable to this article as no datasets were generated or analyzed during the development of this review. Asthma is the most common respiratory disorder in Canada. Despite significant improvement in the diagnosis and management of this disorder, the majority of Canadians with asthma remain poorly controlled. In most patients, however, control can be achieved through the use of avoidance measures and appropriate pharmacological interventions. Inhaled corticosteroids ICS represent the standard of care for the majority of patients. Biologic therapies targeting immunoglobulin E or interleukin-5 are recent additions to the asthma treatment armamentarium and may be useful in select cases of difficult to control asthma.

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Asthma is a common long-term inflammatory disease of the airways of the lungs. Asthma is thought to be caused by a combination of genetic and environmental factors. There is no cure for asthma. In , million people globally had asthma, up from million in Asthma is characterized by recurrent episodes of wheezing , shortness of breath , chest tightness , and coughing.

A number of other health conditions occur more frequently in people with asthma, including gastro-esophageal reflux disease GERD , rhinosinusitis , and obstructive sleep apnea. Cavities occur more often in people with asthma. Asthma is caused by a combination of complex and incompletely understood environmental and genetic interactions. Many environmental factors have been associated with asthma's development and exacerbation, including, allergens, air pollution, and other environmental chemicals.

Exposure to indoor volatile organic compounds may be a trigger for asthma; formaldehyde exposure, for example, has a positive association. The majority of the evidence does not support a causal role between acetaminophen paracetamol or antibiotic use and asthma. Asthma is associated with exposure to indoor allergens. The hygiene hypothesis attempts to explain the increased rates of asthma worldwide as a direct and unintended result of reduced exposure, during childhood, to non-pathogenic bacteria and viruses.

Use of antibiotics in early life has been linked to the development of asthma. Family history is a risk factor for asthma, with many different genes being implicated. Even among this list of genes supported by highly replicated studies, results have not been consistent among all populations tested. Some genetic variants may only cause asthma when they are combined with specific environmental exposures. Endotoxin exposure can come from several environmental sources including tobacco smoke, dogs, and farms.

Risk for asthma, then, is determined by both a person's genetics and the level of endotoxin exposure. A triad of atopic eczema , allergic rhinitis and asthma is called atopy. There is a correlation between obesity and the risk of asthma with both having increased in recent years. Beta blocker medications such as propranolol can trigger asthma in those who are susceptible.

Some individuals will have stable asthma for weeks or months and then suddenly develop an episode of acute asthma. Different individuals react to various factors in different ways.

Home factors that can lead to exacerbation of asthma include dust , animal dander especially cat and dog hair , cockroach allergens and mold.

Both viral and bacterial infections of the upper respiratory tract can worsen the disease. This might reflect a combination of factors, including poor treatment adherence, increased allergen and viral exposure, and altered immune tolerance. There is limited evidence to guide possible approaches to reducing autumn exacerbations, but while costly, seasonal omalizumab treatment from four to six weeks before school return may reduce autumn asthma exacerbations.

Asthma is the result of chronic inflammation of the conducting zone of the airways most especially the bronchi and bronchioles , which subsequently results in increased contractability of the surrounding smooth muscles.

This among other factors leads to bouts of narrowing of the airway and the classic symptoms of wheezing. The narrowing is typically reversible with or without treatment. Occasionally the airways themselves change. Chronically the airways' smooth muscle may increase in size along with an increase in the numbers of mucous glands.

Other cell types involved include: T lymphocytes , macrophages , and neutrophils. There may also be involvement of other components of the immune system including: cytokines , chemokines , histamine , and leukotrienes among others. Figure A shows the location of the lungs and airways in the body. Figure B shows a cross-section of a normal airway. Figure C shows a cross-section of an airway during asthma symptoms. Obstruction of the lumen of a bronchiole by mucoid exudate, goblet cell metaplasia , and epithelial basement membrane thickening in a person with asthma.

While asthma is a well-recognized condition, there is not one universal agreed upon definition. The chronic inflammation is associated with airway hyper-responsiveness 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".

There is currently no precise test for the diagnosis, which is typically based on the pattern of symptoms and response to therapy over time. Spirometry is recommended to aid in diagnosis and management. It however may be normal in those with a history of mild asthma, not currently acting up. 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. 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.

Asthma is clinically classified according to the frequency of symptoms, forced expiratory volume in one second FEV 1 , and peak expiratory flow rate. 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 and emphysema.

An acute asthma exacerbation is commonly referred to as an asthma attack. The classic symptoms are shortness of breath , wheezing , and chest tightness.

Signs occurring 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. Acute severe asthma , previously known as status asthmaticus, is an acute exacerbation of asthma that does not respond to standard treatments of bronchodilators and corticosteroids.

Brittle asthma is a kind of asthma distinguishable by recurrent, severe attacks. Type 2 brittle asthma is background well-controlled asthma with sudden severe exacerbations.

Exercise can trigger bronchoconstriction both in people with or without asthma. Asthma as a result of or worsened by workplace exposures is a commonly reported occupational disease. 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.

Alcohol may worsen asthmatic symptoms in up to a third of people. There is negative skin test to common inhalant allergens and normal serum concentrations of IgE. Often it starts later in life, and women are more commonly affected than men.

Usual treatments may not work as well. 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 , laryngotracheomalacia , vascular rings , enlarged lymph nodes or neck masses.

In both populations vocal cord dysfunction may present similarly. 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. The evidence for the effectiveness of measures to prevent the development of asthma is weak.

Early pet exposure may be useful. Dietary restrictions during pregnancy or when breast feeding have not been found to be effective at preventing asthma in children and are not recommended. While there is no cure for asthma, symptoms can typically be improved. This plan should include the reduction of exposure to allergens, testing to assess the severity of symptoms, and the usage of and adjustments to medications. 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. 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, a leukotriene antagonist or a mast cell stabilizer by mouth is recommended.

For those who have daily attacks, a higher dose of inhaled corticosteroids is used. In a moderate or severe exacerbation, corticosteroids by mouth are added to these treatments. People with asthma have higher rates of anxiety , psychological stress , and depression. Improving people's knowledge about asthma and using a written action plan has been identified as an important component of managing asthma. These interventions may also reduce the number of days children experience asthma symptoms and may lead to small improvements in asthma-related quality of life.

However, there is no evidence regarding the use in these instances. Avoidance of triggers is a key component of improving control and preventing attacks. The most common triggers include allergens , smoke from tobacco or other sources , air pollution, non selective beta-blockers , and sulfite-containing foods. Overall, exercise is beneficial in people with stable asthma.

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.

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.


Guidelines for diagnosis and management of bronchial asthma: Joint ICS/NCCP (I) recommendations

Asthma is a common long-term inflammatory disease of the airways of the lungs. Asthma is thought to be caused by a combination of genetic and environmental factors. There is no cure for asthma. In , million people globally had asthma, up from million in Asthma is characterized by recurrent episodes of wheezing , shortness of breath , chest tightness , and coughing.


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