Historical Background of Asthma:
Asthma originates from Greek word meaning "Shortness of breath". Later in 19th century, asthma was defined by Dr. Salter as the disease in which smooth muscles of airway contract resulting in constricted airways. Later, Dr. Osler the father of modern medicine described the inflammatory process, excessive smooth muscle constriction and hyper mucosal secretion that defined the basis for pharmacological management. In 1970's and 80's clinical trials and evidence suggested the basis for airway remodeling due to persistent exacerbations and allergen or irritant stimuli in the instigation of allergic asthma. These discoveries led to better understanding of patho-physiology of disease and later drug therapy (Holgate, 2010)
Recent research suggests that asthma affects 5% of the total population (Porth, 2010) with the incidence rate of 15 million in U.S (Sherwood, 2012). In Australia, an estimated 2.2 million population suffers from asthma with incidence rate of 14-16% and 10-12% in children and adults respectively (NAC, 2006). According to Brenner (2007), it is one of the most common chronic childhood disease affecting about 5-6 million children annually. This makes it the fourth leading cause of disability in U.S. It accounts for 1.5-2 million emergency department visits per year (Brenner, 1999).
The prevalence of asthma is reportedly higher in socio-economically disadvantaged background. Studies indicate the risk of asthma development in children is related to lower socio-economic status and poverty (ACAM, 2008). 3.2 Mortality and Morbidity: Although occurrence of asthma is reportedly doubled in past several years however, the morbidity and mortality rates have dramatically decreased due to successful management with patient education, self-monitoring, combination drug therapy and asthma action plan (Porth, 2010). Overall, a sharp decline in mortality rate (69%) is witnessed in the past twenty years. In Australia, 0.30% of the mortality is attributed to asthma alone. Risk factor of death from asthma increases with age. Majority of deaths caused by asthma are attributed to respiratory infections (ACAM, 2008). Other risk factors for mortality due to asthma include severe exacerbation, more than two recent hospitalization episodes, lower socio-economic status, and failure to perceive and implement asthma action plan, illicit drug use, psychiatric issues, chronic lung and cardiovascular diseases (NAEPP, 2007). 4. Etiology: The common factor responsible for all types of asthma is hyper-responsiveness to certain stimuli. Research suggests that the occurrence of inflammatory cells (eosinophils, mast cella tc) contribute to pathogenesis of disease (Porth, 2010). Risk factors for the development of asthma include history of atopy (genetic tendency to develop IgE), viral respiratory infections, gene-environment interaction etc. A number of patients experience constant variations in airway structure like fibrosis, mucous hyper-secretion and smooth muscle hypertrophy may attribute to asthma development (NAEPP, 2007). There is strong relation between asthma and allergy. Evidence suggests that more than 80% people suffering from asthma have allergic disorders such as eczema, allergic rhinitis etc. 5. Pathophysiology: 5.1 Physiology of respiratory system: Respiratory process is a complex and intricate process that is mainly involves