Asthma as a Chronic Respiratory Disease - Essay Example

? Asthma - Asthma General Background What is Asthma Asthma is defined as a chronic respiratory disease characterised by episodes of acute airflow obstruction, increased mucous production, bronchial hypersensitivity and airway inflammation caused by a cascade of conditions and interactions. Each of the mentioned interactions is influenced to a great extent by the internal physiologic environment and external factors. The wheezing and shortness of breath experienced by an individual during an asthmatic attack are a result of physiologic interactions. The attacks are triggered by airway irritants such as cigarette smoke, allergens, and environmental pollutants. (Clark 2011, p.15-16). History of Asthma: The history of asthma is as old as antiquity. This statement can be justified by the fact that prescriptions for asthmatic patients written in hieroglyphics were found in the Egyptian Ebers Papyrus which was discovered in the 1870s. Such prescriptions included formulations of inhalations which contained mixtures of herbs intended to be heated on a brick in order to generate fumes which were to be inhaled by the patient. The Greek word azein means “-to breathe hard-” and the word asthma is derived from azein. Therefore, the literal meaning of asthma is a condition characterized by difficult breathing. (Clark 2011, p.1-2). Epidemiology: Asthma is a chronic respiratory disease and its severity ranges from severe occasional symptoms to persistent symptoms. It is one of the most common chronic diseases of children with a global prevalence of about 5%. The incidence rates of asthma can be as high as 20% in developed countries. The disease is more in developed countries than in developing countries. Recent statistics show that the incidence rate of asthma is steadily increasing both in developed and developing countries. The development of new treatment and management strategies has unfortunately had no significant effect on reducing the mortality rates associated with asthma. (Gershwin & Albertson 2008, p.232). The prevalence of asthma in the United States of America in 2009 was 8.2% that is 24.6 million individuals. A survey of patient subgroups revealed that the prevalence of asthma was more common in females compared to males. Furthermore, the National Health Statistics Reports 2005-2009 (Atkinson, Moorman & Xiang Liu 2011) reveal a higher prevalence of asthma in children, individuals of non-Hispanic Black and Puerto Rican race or ethnicity, and persons with a family income below the average poverty line. A higher prevalence was also observed in individuals residing in Northeast and Midwestern regions. Due to asthma, a total of 10.5 million school days and 14.2 million work days were missed in 2008 alone. The 2007 statistics reveal that a total of 1.75 million visits to emergency departments were related to asthma. Moreover, the 2007 statistics reveal that 456,000 asthma related hospitalisations were reported. (Akinbami, Moorman, & Liu 2011, pg.1). Etiology: The etiology of asthma is difficult to define because it is a heterogeneous disease governed by genetic and environmental factors. The non specific hyperirritability of the tracheobronchial tree is the most common underlying characteristic of asthmatic diathesis. Asthma is divided into two major types on clinical basis: allergic (extrinsic) and idiosyncratic (intrinsic). The development of allergic asthma is mediated by genetic factors due to which the individual’s susceptibility to precipitating factors and extracts of airborne antigens is increased. The major characteristic of allergic asthma is high serum level of immunoglobulin E (IgE). In 25 to 30% of all allergic asthma cases, the immunologic mechanisms are casually related, whereas in 33% of cases the immunologic mechanisms are contributory. An asthmatic attack is precipitated by agents that stimulate the receptors present on the surfaces of tracheobronchial receptors. Cholinergic mediation is responsible for the development of intraoperative bronchospasm. Furthermore, the stimulation of afferent receptors on bronchial mucosa can also precipitate an asthmatic attack. Bronchoconstriction is also mediated by the stimulation of M3 cholinergic receptors on bronchial smooth muscles; the impulse for constriction is carried by efferent parasympathetic fibres to the bronchial smooth muscles. The stimulation of M3 cholinergic receptors results in the release of acetylcholine which acts on M2 muscarinic receptors and cause bronchospasm. (Malhotra & Yao 2012, p.45). Pathophysiology and Pathogenesis: The primary characteristics of asthma are chronic airway inflammation, reversible expiratory airflow obstruction, and hypersensitivity of the airways. The nonspecific hyperirritability of the tracheobronchial tree is the common underlying denominator in the diasthesis of asthma. Asthma is characterised by persistent subacute airway hyperirritability, the exact mechanism of which is still unknown. According to the most popular hypothesis, subacute airway hyperirritability is a result of subacute airway inflammation. Bronchial biopsy of asthmatics in remission reveals an infiltration of inflammatory cells coupled with shedding of epithelial mucosa. The exposure to a stimulus results in the activation of mast cells, eosinophils, T-lymphocytes, macrophages, basophils, neutrophils, and platelets. Moreover, the exposure also results in the stimulation of structural cells including epithelial cells, fibroblasts, and airway smoth muscle cells. The stimulation of inflammatory cells and structural cells results in the release of large amounts of various chemical mediators which cause bronchospasm, vascular congestion, increased capillary permeability, and thick tenacious secretions. (Malhotra & Yao 2012, p.46). The T helper cell type-2 (Th2) immune responses that typically occur in atopic conditions are also associated with asthma. A cascade of immune mediated events resulting in the development of chronic airway inflammation is triggered by various allergic and non allergic agents. The inflammation of airways is the hallmark of asthma. The allergic agents that might precipitate an asthmatic attack are dust mites, cockroach residue, furred animals, moulds, and pollens, whereas the agents included in the non allergic category are infections, tobacco smoke, cold air, and exercise. Exposure to these agents leads to an increase in the levels of Th2 cells in the airways which results in the production of specific cytokines. The cytokines released in response to elevated levels of Th2 cells include IL-4, IL-5, IL-9 and IL-13. The released cytokines stimulate the development of eosinophilic inflammation and also stimulate masts cells to produce large amounts of IgE. In response to elevated levels of IgE, various inflammatory mediators such as histamine and cysteinyl leukotrienes are released. The inflammatory mediators are responsible for the development of symptoms characteristic of asthma including contraction of smooth muscles in respiratory airways (bronchospasm), edema, and hypersecretion of mucous. (Kim & Mazza 2011, p.2). A late phase asthmatic response is triggered by mediators and cytokines released during the early stages of an immune response to an allergen. The late phase asthmatic response is characterised by further inflammation of the airways and an increase in the bronchial hypersensitivity. The development of asthma is governed by genetic predisposition and the disease runs in families. The link to genetic predisposition is justified by the identification of various regions on chromosomes which are associated with increased susceptibility to allergic and non allergic agents in asthmatic patients. Moreover, a number of chromosomal regions associated with the mediation of increased production of IgE have been identified in asthmatic patients and increased expression of airway hyper responsiveness coupled with accelerated production of inflammatory mediators have also been identified. (Kim & Mazza 2011, p.2). The net result of the inflammatory reaction is decrease in the diameter of the airways which increases the resistance to air flow and causes a reduction in decreased forced expiratory volumes and flow rates. The cascade of events also result in hyperinflation of the lungs and thorax, increased breathing work, respiratory tract muscle function alterations, mismatched perfusion, and alteration in the concentration of blood gases. (Malhotra &Yao 2012, p.46). Classification: Brittle Asthma: Sir John Floyer in 1698 provided the first description of brittle asthma. Patients of brittle asthma have a characteristic rapid swing in their respiratory condition. The rapid swings further deteriorate and result in an impaired respiratory status. The morning dipping of PEFR based on diurnal variation is particularly exaggerated in patients with brittle asthma and is usually manifested in two ways. Type 1 brittle asthma is characterised by a maintained hyper variability of PEFR, whereas type 2 brittle asthma has a characteristic sudden precipitation of airway obstruction. The delineation of precipitating factors of brittle asthma has not yet been done; however, risk factors include female gender, psychological disorders, food intolerances, atopy, and decreased perception of airway compromise, reduced total lung capacity, decreased hypoxic drive, and neutrophil induced inflammation of the airways. (Gershwin & Albertson 2008, p.267). Occupational Asthma: The most common occupational lung disease in developed countries is occupational asthma and is defined as the asthma induced by stimulus present only at the work place of an individual. The common stimuli at the workplace include animals in veterinary hospitals or zoos, wood dust in lumber yards, and hair sprays in beauty salons. As many as 400 agents associated with the development of occupational asthma have been identified. This category of asthma encompasses about 15% of adult asthmatics. The diagnosis occupies special criteria and the diagnosis might involve as long as several months of vigilant observation and data collection. The mechanisms involved in occupational asthma can be immunologic as well as non-immunologic. An individual who already has asthma and has an attack induced through stimuli present at the workplace is not classified under the category of occupational asthma. The proper diagnosis of occupational asthma is quite crucial due to the involvement of worker’s compensation decisions. (Gershwin & Albertson 2008, p.285). Exercise Induced Asthma: Patients who experience wheezing or bronchoconstriction upon exertion fall into the category of exercise induced asthmatics (EIA). Usually, the precipitation of an asthmatic attack requires significant aerobic activity however numerous exceptional cases have also been reported. EIA is quite prevalent among adolescents and it can also exist in patients who are suffering from conventional asthma. Individuals with EIA can go on to become elite athletes because the prognosis of the disease is generally quite good. (Gershwin & Albertson 2008, p.231). Pregnancy and Asthma: Asthma is not listed under the contraindications of pregnancy. However, a pregnant patient with a history of uncontrolled asthma has a higher risk of developing complications which can pose dangers for herself and her baby if her asthma exacerbates during gestation. Several studies have revealed that the severity of asthma is subject to change during gestation. Approximately one third of pregnant asthmatics exhibit exacerbation of asthma; equal numbers of pregnant asthmatics show a decrease in the severity of asthma and the remaining one third shows no change in the severity of symptoms during pregnancy. Poorly controlled asthma during gestation can have a serious impact on the baby; the risk of perinatal mortality can increase by several folds and an increased chance of premature birth and low birth weight has been observed. In order to decrease the incidence of complications associated with asthma during gestation it is important that susceptible mothers follow an asthma action plan throughout pregnancy by susceptible women. (Clark 2011, p.21). Status asthmaticus: Status asthmaticus is a type of asthma characterised by acute exacerbation and irresponsiveness to bronchodilators and steroids. The prevalence of status asthmaticus accounts for about 5 to 10% of adult asthmatics. The hallmark of status asthmaticus is the thickening of the basement membrane and smooth muscle hypertrophy. Unlike other types of asthma, status asthmaticus is more prevalent among males than females. The irresponsiveness to steroids is due to abnormalities in histone deacylation pathways, overexpression of the alternative, non-functioning of glucocorticoid beta receptor, or transcriptional factor interference. (Clark 2011, p.21-22). Diagnosis of Asthma: The key symptoms of asthma are: i. The peak flow numbers are observed in caution/yellow range ii. Persistent cough which is more severe at night and maybe with or without the production of mucous iii. Shortness of breath upon exertion iv. Chest pain and intercostals retractions v. Sudden precipitation of an attack of wheezing which is episodic in nature and gets worse at night and morning vi. Wheezing worsens with heartburn, exposure to cold air, or during strenuous aerobic activity. (Clark 2011, p.17). Patient Presentations: Due to the presence of an extensive differential diagnosis, complete physical examination of a patient with wheezing and coughing in the emergency room is essential. An asthmatic patient usually has fine wheezing with a characteristic musical sound which is heard more prominently during expiration. Upon administration of bronchodilators, the wheezing significantly diminishes. The patient repeatedly coughs and shows shortness of breath. (Gershwin & Alberton 2008, p.232). Diagnostic Testing: Spirometry: In order to access reversible airway obstruction and to diagnose asthma, spirometry is the most reliable method. Spirometry can be done on patients who are eligible for lung function testing and are above the age of six years. Spirometry is usually performed in pulmonary function laboratories and primary care facilities; it is essential to perform the test within strict protocols. The test is performed by requesting the patient to breathe deeply and exhale forcefully into a spirometer. The forced vital capacity and forced expiratory volume are measured in one second with the spirometer. The measure of air flow obstruction is provided by the calculation of FEV to FVC. An improvement in FEV by 12% after the administration of 200 ml of inhaled rapid acting bronchodilator confirms the existence of asthma. (Kim & Mazza 2011, p.3). Peak Expiratory Flow Monitoring: In case spirometry is not available, an alternate testing method can be employed which is known as peak expiratory flow monitoring. Peak expiratory flow monitoring is usually used to either diagnose occupational asthma or to monitor the effectiveness of treatment strategies. The best time to perform the test is morning and evening. The diurnal variation in FEV and a 12% improvement rate indicates the presence of asthma. (Kim & Mazza 2011, p.3). Challenge Testing: Direct airway challenging tests (inhaled bronchoconstrictor stimuli such as methacholine or histamine) and indirect challenges (mannitol or exercise) are employed in the diagnosis of asthma which is characterised by normal lung function tests. During the test, the patient is instructed to inhale increasing concentrations of the stimulus. The stimulus is inhaled until a given level of bronchoconstriction is achieved (i.e. a 20% fall in FEV). The results of the tests are presented in the form of a dose of the stimulating agent used which results in 20% reduction of FEV. A positive result with methacholine is a PC20 value of less than 8mg/mL. Non- Invasive Markers of Airway Inflammation: The measurement of sputum eosinophilia or other inflammatory markers provides a useful way for the diagnosis of asthma. The measurement of inflammatory markers is a better diagnostic test for asthma than lung functioning tests. The non invasive markers testing methods are not widely available for use due to their ongoing clinical trials. (Kim & Mazza 2011, p.3). Allergy Skin Testing: For the identification of possible precipitating factors of asthma and for the determination of the patient’s allergic status, allergy testing methods are generally used. The test involves the use of allergens found in an individual’s geographical location. The tests are very sensitive and are not expressive, thus provide an easy way for diagnosis. (Kim & Mazza 2011, p.4). Differential Diagnosis: The presence of wheezing and dyspnea indicate bronchial asthma. The differential diagnosis of asthma from other respiratory diseases involving wheezing and coughing is quite easy due to the characteristics of asthma such as triad of dyspnea, coughing, wheezing, and history of periodic episodes of attacks. Valuable contributory evidence is provided by the presence of a family history of allergic diseases. Wheezing responsive to bronchodilators constitutes an essential component of differential diagnosis. An individual with asthma usually has an increased chance of developing chronic obstructive lung disease, exertional dyspnea, and orthopnea. The symptoms presented by acute left ventricular failure are similar to those exhibited by bronchial asthma. Clinical findings such as moist basilar rales, gallop rhythms, blood tinged sputum, peripheral edema, and history of heart disease provide ways for differential diagnosis. (Malhotra & Yao 2012, p.48). Management: Measures of Assessment, Monitoring and Prevention: Asthma is becoming a common health issue so its management aims to provide easy and reliable methods of treatment for asthma patients. One of the important objectives of treatment is to minimise the effects of asthma on quality of life. Ideally, the treatment should be able to effectively abolish the symptoms; restoring the normal lung function and minimising the risk of acute exacerbation or asthma attacks. One of the crucial components of asthma management is the involvement of people surrounding the victim, such as parents and teachers. It is important that they should be educated about the disease and encouraged to take part in the treatment of the patient. Monitoring the patient for any sign of respiratory distress is vital especially under the conditions where it most likely to have an exacerbation of disease. (Kumar & Clark 2009, p.942). Lifestyle modification: Identifying the extrinsic factors or the causative allergens and avoiding them is important for asthma management. Lifestyle modification is required to make sure that these allergens such as dust mites, pollens, moulds and certain foods are avoided by wearing masks, prompt cleaning of bedding covers and avoiding cigarette smoke or irritating fumes from cooking. (Kumar & Clark 2009, p.942). Medication: Drug therapy remains the mainstay for the treatment of asthma. Most of these pharmacological agents are inhaled to provide direct access into the target tissue. This accounts for immediate onset of action for most of these drugs. For discussion purposes these medication can be divided into bronchodilators and controllers. (Kasper & Harrison 2005, p.1512). Beta 2 agonists are the most commonly used drugs for bronchodilation. They cause relaxation of the bronchial smooth muscle by stimulating beta 2 receptors. It is important to understand that this therapy can temporarily take care of the respiratory symptoms by widening the airway but it has little or no effect on the underlying inflammation that initially caused the narrowing. Salbutamol or terbutaline inhalers are commonly used. Long acting beta 2 agonists such as salmeterol and formoterol have longer duration of action and are more potent then the short acting beta blockers but are only used along with corticosteroids. Anti-cholinergic and Theophylline are other drugs that can act as bronchodilators but are much less effective compared to beta agonists. Controllers are the drugs that are aimed to treat the underlying inflammation. Inhaled corticosteroids are by far the most successful controllers and have revolutionized asthma treatment. They are very potent anti-inflammatory drugs that considerably reduce the number of inflammatory cells in the airways. They mostly turn off the transcription genes that encodes for inflammatory proteins such as cytokines. Oral or systemic steroids are used to treat acute severe asthma. Other complementary medications such as antileukotrienes and cromones are used in some cases as controllers but are less effective compared to inhaled corticosteroids. (Kasper & Harrison 2005, p.1512-1514). Recent research has revealed that the administration of Aspirin and other nonsteriodal anti-inflammatory drugs (NSAIDs) resuts in exacerbation of asthma. (Anonymous, 2011). Others: Other alternate treatments have been devised and experimented such as immunotherapy, hypnosis, acupuncture, breathing control, yoga etc. (Kasper & Harrison 2005, p.1514). Prognosis: Earlier, it was thought that asthma subsides by the time patients reach their teenage. But the recent studies has shown that it mostly recur in the third or even fourth decade of life. Airway remodeling is mostly an irreversible phenomenon and can severely affect the lung function. (Kumar & Clark 2009, p.946). Despite these factors, asthma has a good prognosis. This is mostly due to the introduction of inhaled corticosteroids as front line medications that limits the inflammation and further remodeling of the airways. Summary and Conclusion: Asthma is a chronic respiratory disease condition with very high global prevalence rates. The incidences are increasing in both developed and developing countries. Asthma has both extrinsic and intrinsic components that play a part in disease development. Chronic inflammation with remodelling of the bronchial tree leads to airway obstruction. The disease is more prevalent in young children than adults. Asthma can affect the quality of life and may impact psychologically on the growth and development of a child. Therefore, management includes support from parents and close associates to minimise limitations in the everyday activities of children suffering from asthma. With the present treatment regimes, asthma has a good prognosis, but prevention can significantly reduce the incidence and mortality rate associated with this disease. References: Clark, M. V. 2011. Asthma: a clinician's guide. Jones & Bartlett Learning. Sudbury, MA. (http://www.cdc.gov/nchs/data/nhsr/nhsr032.pdf). Malhotra, V., & Yao, F.-S. F. 2012. Yao & Artusio's anesthesiology: problem-oriented patient management. Wolters Kluwer Health/Lippincott Williams & Wilkins, Philadelphia. KIM, H., & Mazza, J. 2011. Asthma. BioMed Central Ltd. (http://www.aacijournal.com/content/7/S1/S2). Gershwin, M. E., & Alberton, T. 2008. Bronchial Asthma a Guide for Practical Understanding and Treatment. Springer. Dordrecht, Netherlands. http://public.eblib.com/EBLPublic/PublicView.do?ptiID=364052. Kumar, P. J., & CLARK, M. L. 2009. Kumar & Clark's clinical medicine. Saunders Elsevier, Edinburgh. Kasper, D. L., & Harrison, T. R. 2005. Harrison's principles of internal medicine. McGraw-Hill, Medical Pub. Division, New York. Atkinbami, L., Moorman, J. Liu, & X. 2011. National Health Statistics Reports 2005-2009, Number 32, January 12, 2011, National Center for Health Statistics. (http://www.cdc.gov/nchs/data/nhsr/nhsr032.pdf). Anonymous, 2011. Asthma. A.D.A.M. Medical Encyclopedia. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001196/ Read More