Pathophysiology of the Respiratory System - Asthma - Essay Example

Download file to see previous pages However, asthma can be defined by presence of certain features. Presence of respiratory symptoms (wheeze, bronchoconstriction, breathlessness, cough, chest tightness etc.), chronicity, episodic nature, an inflammatory component and airflow obstruction which is at least partially reversible with treatment are some of these features (SIGN 2012, p. 4). Recent guidelines have strongly emphasised on the inflammatory nature of the disease (Lougheed et al 2012, GINA 2011). Treatment involves management of the chronic disease as well as acute exacerbations, with subtle differences in the management of adult and paediatric patients. 1.1 Epidemiology and prevalence Prevalence of asthma is higher in the developed nations like USA, UK, Australia and north-west Europe but it is increasing in Asia and Africa (Global initiative for asthma, GINA 2011). The trend in UK is increasing from 10% in 1960s to more than 20% in early 2000s (Anderson et al 2007). Nearly 2 million people in Australia suffer from asthma (Australian Centre for Asthma Monitoring 2011). Before puberty, asthma is more prevalent in boys but the trend reverses after puberty. Prevalence is higher in urban areas and metropolitan cities. Socioeconomic status also has an effect with higher prevalence in poor and malnourished individuals. Highest life-time prevalence has been found among school aged children (Simpson & Sheikh 2010). One important trend so far as treatment is concerned has been greater use of inhaled corticosteroids for prevention which has led to decreased mortality and hospital admission rates, while the prevalence has remained constant or increased(Anderson et al 2007). 2.0 Pathophysiology 2.1 Basic pathology behind asthma Asthma is characterized by hyperreactive airways associated with partially or completely reversible airway obstruction. There is chronic and recurrent inflammation of the airways. Airway obstruction mainly results because of the narrowing of the airways caused by smooth muscle contraction in response to various stimuli. Additional obstruction occurs because of plugging of airways with mucous plugs (GINA 2012; NHLBI 2007, p. 16). Because the airways are hyperreactive, a large number of otherwise normal stimuli start instigating a cycle of inflammatory cells activation. These can be common environmental allergens such as pollens, dust, smoke, exhaust fumes & other irritants, respiratory infection, cold, exercise and certain drugs. When any of these stimuli are encountered by the susceptible airways, recruitment of inflammatory cells primarily mast cells, macrophages and eosinophils occur. As an immediate reaction, mast cells with IgE release inflammatory mediators (leukotrienes and cytokines) which are responsible for bringing about smooth muscle contraction, mucosal edema and mucous formation, all of which compromise lumen of the airways. Sequentially, other lymphocytes are recruited escalating the chain of sequences leading to bronchospasm and other clinical manifestations (Mitchell et al 2006, p. 382). 2.2 Role of hypersensitivity and immune system There is a role of immune response in producing and regulating inflammation in asthma. There occurs an imbalance between T1 and T2 helper cells. ‘Hygiene hypothesis’ links asthma to a persistence of T2 helper cytokine pattern that was present in the new born, which later on leads to production of IgE ...Download file to see next pagesRead More