Bronchoconstriction is the constriction of the airways in the
lungsdue to the tightening of surrounding smooth muscle, with consequent coughing, wheezing, and shortness of breath. Bronchoconstriction can also be due to an accumulation of thick mucus.
The condition has a number of causes, the most common being
emphysemaas well as asthma. Exerciseand allergies can bring on the symptoms in an otherwise non-symptomic individual.
With emphysema the shortness of breath due to effective bronchoconstriction from excessive very thick mucous blockage (it is so thick that great difficulty is encountered in expelling it resulting in near exhaustion at times) can bring on panic attacks unless the individual expects this and has effectively learned pursed lip breathing to more quickly transfer oxygen to the blood via the damaged alveoli resulting from the disease. The most common cause of emphysema is smoking and smoking cessation is mandatory if this incurable disease is to be treated. Prevention of bronchoconstriction by this pathway is vital for emphysema sufferers and there are several
anticholinergicmedications that can greatly improve the quality of life for these individuals. In combination with mucous thinning agents such as Guaifenesinsignificant improvement in breathing can be accomplished.
More generally termed "exercise-induced asthma", the preferred and more accurate term "exercise-induced bronchoconstriction" better reflects underlying
pathophysiology. It is also preferred due to the former term giving the false impression that asthma is caused by exercise.
In a patient with EIB, exercise initially follows the normal patterns of bronchodilation. However, by three minutes, the constriction sets in, which peaks at around 10-15 minutes, and usually resolves itself by an hour. During an episode of this type of bronchorestriction, the levels of inflammatory mediators, particularly
leukotrienes, histamine, and interleukin, increase. TH2-type lymphocytes are activated, with an increase in T cells expressing CD25 (IL-2R), and B cells expressing CD 23, causing increased production of IgE. After exercise, the conditions will fade within one to three minutes. In most sufferers of EIB, this is followed by a "refractory period", of generally less than four hours, during which if exercise is repeated, the bronchorestriction is less emphasised. This is probably caused by the release of prostaglandins.
The underlying cause of this type of bronchoconstriction appear to be the large volume of cool, dry air inhaled during strenuous exercise. The condition appears to improve when the air inhaled is more fully humidified and closer to
This specific condition, in the general population, can vary between 7 and 20 percent. This increases to around 80 percent in those with symptomatic asthma. In many cases, however, the constriction, even during or after strenuous exercise, is not clinically significant except in cases of severe to moderate emphysema.
While a different cause, this has very similar symptoms, namely the immunological reaction involving release of inflammatory mediators.
allergens in sensitized subjects develops into bronchorestriction within 10 minutes, reaches a maximum within 30 minutes, and usually resolves itself within one to three hours. In some subjects, the constriction does not return to normal, and recurs after three to four hours, which may last up a day or more. The first is named the "early asthmatic response", and the latter the "late asthmatic response".
* [http://ajrccm.atsjournals.org/cgi/content/full/161/2/S1/S68 Bronchoconstriction caused by allergen and exercise]
* [http://www.asthma.ge Pharmacotherapy of bronchoconstriction in patients with asthma by antiepileptic drugs]
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