Asthma

Asthma is a chronic condition involving the respiratory system in which the airway occasionally constricts, becomes inflamed, and is lined with excessive amounts of mucus, often in response to one or more triggers. These episodes may be triggered by such things as exposure to an environmental stimulant (or allergen) such as cold air, warm air, perfume, moist air, exercise or exertion, or emotional stress. In children, the most common triggers are viral illnesses such as those that cause the common cold. This airway narrowing causes symptoms such as wheezing, shortness of breath, chest tightness, and coughing. The airway constriction responds to bronchodilators.

Causes:
Many environmental risk factors have been associated with asthma, but a few stand out as well-replicated or that have a meta-analysis of several studies to support their direct association.

* Poor air quality, from traffic pollution or high ozone levels, has been repeatedly associated with increased asthma morbidity and has a suggested association with asthma development that needs further research.
* Environmental tobacco smoke, especially maternal cigarette smoking, is associated with high risk of asthma prevalence and asthma morbidity, wheeze, and respiratory infections.
* Viral respiratory infections at an early age, along with siblings and day care exposure, may be protective against asthma, although there have been controversial results, and this protection may depend on genetic context.
* Antibiotic use early in life has been linked to development of asthma in several examples; it is thought that antibiotics make one susceptible to development of asthma because they modify gut flora, and thus the immune system (as described by the hygiene hypothesis).
* Caesarean sections have been associated with asthma when compared with vaginal birth; a meta-analysis found a 20% increase in asthma prevalence in children delivered by Caesarean section compared to those who were not. It was proposed that this is due to modified bacterial exposure during Caesarean section compared with vaginal birth, which modifies the immune system (as described by the hygiene hypothesis).
* Psychological stress on the part of a child's caregiver has been associated with asthma, and is an area of active research. Stress can modify behaviors that affect asthma, like smoking, but research suggests that stress has other effects as well. There is growing evidence that stress may influence asthma and other diseases by influencing the immune system.

Symptoms:

In some individuals asthma is characterized by chronic respiratory impairment. Some or all of the following symptoms may be present in those with asthma: dyspnea, wheezing, stridor, coughing, an inability for physical exertion. Some asthmatics who have severe shortness of breath and tightening of the lungs never wheeze or have stridor and their symptoms may be confused with a COPD (chronic obstructive pulomonary disease)-type disease. An acute exacerbation of asthma is commonly referred to as an asthma attack.
The clinical hallmarks of an attack are shortness of breath (dyspnea) and either wheezing or stridor (high pitched sound produced due to blockade of epiglottis).
Signs of an asthmatic episode include wheezing, prolonged expiration, a rapid heart rate (tachycardia), rhonchous lung sounds (audible through a stethoscope), the presence of a paradoxical pulse (a pulse that is weaker during inhalation and stronger during exhalation), and over-inflation of the chest. During a serious asthma attack, the accessory muscles of respiration (sternocleidomastoid and scalene muscles of the neck) may be used.
During very severe attacks, an asthma sufferer can turn blue from lack of oxygen, and can experience chest pain or even loss of consciousness. Just before loss of consciousness, there is a chance that the patient will feel numbness in the limbs and palms may start to sweat.The person's feet may become icy cold.

Treatment:
The most effective treatment for asthma is identifying triggers, such as pets or aspirin, and limiting or eliminating exposure to them. Desensitization is currently the only known "cure" to the disease. Other forms of treatment include relief medication, prevention medication, long-acting β2-agonists, and emergency treatment.
Trigger avoidance-smoking is believed to adversely affect asthmatics in several ways, including an increased severity of symptoms. Asthmatics who smoke or who live near traffic typically require additional medications to help control their disease.
Medical treatment-The specific medical treatment recommended to patients with asthma depends on the severity of their illness and the frequency of their symptoms. Specific treatments for asthma are broadly classified as relievers, preventers and emergency treatment. Bronchodilators are recommended for short-term relief in all patients. For those who suffer daily attacks, a higher dose of glucocorticoid in conjunction with a long-acting inhaled β-2 agonist may be prescribed; alternatively, a leukotriene modifier or theophylline may substitute for the β-2 agonist. In severe asthmatics, oral glucocorticoids may be added.
Relievers-Short-acting, selective beta2-adrenoceptor agonists, such as salbutamol (albuterol), levalbuterol, terbutaline and bitolterol. Selective adrenergic agonists, such as inhaled epinephrine and ephedrine tablets, have also been used. Anticholinergic medications, such as ipratropium bromide may be used instead. Inhaled glucocorticoids are usually considered preventive medications.