The larger the amount of ventilation and the colder the air inspired, the greater becomes the probability of airway narrowing. There are two prominent theories on how airway narrowing leads to bronchoconstriction. One involves that the increase in osmolarity in the airway mucosa produced by airway drying and cooling stimulated the release of inflammatory mediators from mast cells, including histamine and leukotriene that cause bronchoconstriction (Navarra 332). While in the other mechanism, airway cooling does not directly cause bronchoconstriction, instead it is the rapid rewarming of the airway, after an activity like exercise, which causes smooth-muscle contraction. It is believed that with rapid rewarming, there is a “vascular phenomenon” of reactive hyperemia, with sudden blood flow and vascular permeability, leading to edema and airway obstruction (Navarra 332). Allergen-induced acute bronchoconstriction results from an IgE-dependent release of mediators from mast cells including histamine, tryptase, leukotrienes, and prostaglandins that directly contract airway smooth muscle (Navarra 332). In some patients acute airflow obstruction may be caused by Aspirin or any other nonsteroidal anti-inflammatory drugs (National Asthma Education and Prevention Program 11). This is a non IgE-dependent response, which involves the mediator release of airway cells (National Asthma Education and Prevention Program 11). Asthma exacerbation may also be caused by stress, and its mechanism involves enhanced generation of pro-inflammatory cytokines (Navarra 332). Airway Edema: Airway edema or “fluid in the airway” is caused by micro-vascular leakage in response to inflammatory mediators (Navarra 332). This may be reversible by...
Understanding the Pathophysiologic causes, types and symptoms of Asthma
Definition of Asthma: The International Consensus Report on Diagnosis and Management described Asthma as “A chronic inflammatory disorder of the airways in which many cells play a role, including mast cells, eosinophils, T lymphocytes, macrophages, neutrophils, and epithelial cells. In susceptible individuals this inflammation causes symptoms that are usually associated with widespread but variable airflow obstruction, that is often reversible and causes an increase in airway responsiveness to a variety of stimuli”. According to this definition Asthma could be understood as a disease of the airways characterized by inflammation and reversible bronchospasm. This definition doesn't only emphasize on the importance of inflammation in the etiology of asthma, but also establishes the fact that this inflammation causes the airways to be hypersensitive to external stimuli. The clinical manifestations and severity of asthma is determined by the interaction of these features. Pathophysiological causes of Asthma: Pathologically, the airflow obstruction in asthma is due to combinations of bronchial smooth-muscle contraction, mucosal edema and inflammation, and viscid mucus secretion. Some patients may never develop the symptom of wheezing but instead experience coughing as an initial symptom.
Dyspnea, shortness of breath, tightness in the chest, a lot of mucus in the throat, coughing attacks after laughing or crying, and coughing attacks at nights are some other common symptoms of asthma.