Asthma overview
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Editor(s)-in-Chief: C. Michael Gibson, M.S., M.D. [1] Phone:617-632-7753; Philip Marcus, M.D., M.P.H. [2]
Overview
Asthma is a chronic inflammatory disease that is characterized by a hyper-responsive airway and a resultant reversible airway obstruction. Approximately 5% of the total population have been diagnosed with asthma. Asthma affects one in four urban children.[1][2] Asthmatics, a term used to characterize an individual affected with asthma, develop intermittent airway constriction and subsequent inflammation that is lined with excessive amounts of mucus as a response to one or more triggers. Environmental stimulants such as dust, cold air, mold, pollen and exercise or stress can trigger an asthmatic episode; however, in children, viral illness such as common cold remains the most common trigger.[3] The classic symptoms include prolong expiratory wheeze, cough and shortness of breath secondary to airway obstruction that promptly responds to bronchodilator therapy. Between episodes most patients remain either, asymptomatic or have mild symptoms and may remain short of breath for longer periods after exercise. A positive bronchodilator response is strongly suggestive of asthma. Short-acting beta-2 agonist, inhaled anti-cholinergics and systemic steroids may be used for immediate symptomatic relief; however, long-term symptom control may be achieved with long-acting beta-2 agonists, mast cell stabilizers, leukotriene inhibitors and/or steroids.
Pathophysiology
Asthma is the result of an immune response in the bronchial airways.[4]. During an asthma episode, inflamed airways react to the introduction of environmental triggers, such as smoke, dust, or pollen. The airways narrow and produce excess mucus, making it difficult to breathe.
The airways of asthmatics are "hypersensitive" to certain triggers, also known as stimuli. In response to exposure to these triggers, the bronchi (large airways) contract into spasm (an "asthma attack"). Inflammation soon follows leading to a further narrowing of the airways and excessive mucus production, this can lead to coughing and other breathing difficulties.
Epidemiology and Demographics
Approximately 300 million people around the world currently have asthma[5] and the number is estimated to increase by additional 100 million by the year 2025. Prevalence of asthma is high among children and females in industrialized nations. The International Study of Asthma and Allergies in Childhood (ISAAC), a study which measured the global prevalence and severity of asthma symptoms in children, demonstrated that the high rates of asthma were noted in countries whose predominant language is English[6]. Puerto Rican people have the highest prevalence of asthma in USA[7]. Asthma accounts for 217,000 emergency room visits and 10.5 million physician office visits every year[8].
Natural History, Complications and Prognosis
Wheezing may occur early in childhood. In the majority of cases, unless severely asthmatic or predisposed to asthmatic symptoms, wheezing may not persist into adulthood. Asthma progression during childhood varies with gender and may sometimes regress completely. In contrast, in some cases, a patient may experience adult onset asthma. Prognosis of asthma, in the absence of other co-morbidities, is generally positive with treatment and life expectancy being similar to that of the comparable general population. Complications of asthma may include status asthmaticus, respiratory failure, candidiasis and cardiac dysfunction.
Diagnosis
Physical Examination
The characteristic physical signs of asthma include loud prolong polyphonic expiratory wheeze and adventitious sounds such as rhonchi. Presence of wheeze is indicative of airway narrowing; however, the absence of wheeze indicates a silent lung characteristic of status asthmaticus delineated by widespread obstruction that results in significant airflow reduction and insufficient enough to produce a wheeze.
Chest X-ray
Chest x-ray in asthmatics is often normal. Chest x-ray is often used to exclude other causes of wheeze and to diagnosis complications such as atelectasis and pneumonia[9].
References
- ↑ Akinbami LJ, Schoendorf KC (2002) Trends in childhood asthma: prevalence, health care utilization, and mortality. Pediatrics 110 (2 Pt 1):315-22. PMID: 12165584
- ↑ Lilly CM (2005) Diversity of asthma: evolving concepts of pathophysiology and lessons from genetics. J Allergy Clin Immunol 115 (4 Suppl):S526-31. DOI:10.1016/j.jaci.2005.01.028 PMID: 15806035
- ↑ Zhao J, Takamura M, Yamaoka A, Odajima Y, Iikura Y (2002) Altered eosinophil levels as a result of viral infection in asthma exacerbation in childhood. Pediatr Allergy Immunol 13 (1):47-50. PMID: 12000498
- ↑ Maddox L, Schwartz DA. The Pathophysiology of Asthma. Annu. Rev. Med. 2002, 53:477-98. PMID 11818486
- ↑ Masoli M, Fabian D, Holt S, Beasley R, Global Initiative for Asthma (GINA) Program (2004). "The global burden of asthma: executive summary of the GINA Dissemination Committee report". Allergy. 59 (5): 469–78. doi:10.1111/j.1398-9995.2004.00526.x. PMID 15080825.
- ↑ Lai CK, Beasley R, Crane J, Foliaki S, Shah J, Weiland S; et al. (2009). "Global variation in the prevalence and severity of asthma symptoms: phase three of the International Study of Asthma and Allergies in Childhood (ISAAC)". Thorax. 64 (6): 476–83. doi:10.1136/thx.2008.106609. PMID 19237391.
- ↑ Akinbami LJ, Moorman JE, Liu X (2011). "Asthma prevalence, health care use, and mortality: United States, 2005-2009". Natl Health Stat Report (32): 1–14. PMID 21355352.
- ↑ Pitts SR, Niska RW, Xu J, Burt CW (2008). "National Hospital Ambulatory Medical Care Survey: 2006 emergency department summary". Natl Health Stat Report (7): 1–38. PMID 18958996.
- ↑ National Asthma Education and Prevention Program (2007). "Expert Panel Report 3 (EPR-3): Guidelines for the Diagnosis and Management of Asthma-Summary Report 2007". J Allergy Clin Immunol. 120 (5 Suppl): S94–138. doi:10.1016/j.jaci.2007.09.043. PMID 17983880.