Asthma Definition Asthma is a disease characterized by
Asthma
• Definition: Asthma is a disease characterized by increased responsiveness of trachoebronchialtree to a multiplicity of stimuli clinically it is manifested by paroxysms of dyspnea, cough and wheezing. 2/23/2021 copyright (your organization) 2003 2
• Epidemiology: Incidence diagnosed asthma may be around 2 -6% of all population. ½ of cases develop before age of 10 1/3 of cases occur before age of 40 In childhood there is 2: 1 male/female ratio which equalize by age 30. Incidence of disease is almost lower in underdeveloped societies. 2/23/2021 copyright (your organization) 2003 3
• Pathogentic mechanism: 2/23/2021 copyright (your organization) 2003 4
• Immunological mechanism: 2/23/2021 copyright (your organization) 2003 5
• Mediators of the asthmatic reaction: Histamine Leukocyte chemo tactic factors Prostaglandins Leukotrienes Platelet activating factor (PAF) Kinins Adenosine 2/23/2021 copyright (your organization) 2003 6
Neural mechanism: Sympathetic Receptor Parasympathetic Receptor Beta Sympathetic receptor on smooth muscles stimulated by circulating catecholamine or beta receptor agonist causing bronchial relaxation (Asthmatic patients have a reduction of B& increase in excitatory alpha receptor such difference may be related to genetic factors or may be acquired as a result of allergic infective or autoimmune factor Parasympathetic receptor induce bronchial constriction and anti parasympathetic drugs cause bronchodilation in normal subjects and in patients with asthma 2/23/2021 copyright (your organization) 2003 7
Provoking factors: We have seven major categories of stimuli that increase airway responsiveness and provoke acute attacks of asthma 2/23/2021 copyright (your organization) 2003 8
• 7 major categories: • *Allergens (15 -35%) *Pharmacological stimuli (beta adrenergic antagonist & aspirin other NSAID) *Infection *Air pollution *Occupational factors *Exercise (thermal & osmolarity changes may lead to release of bronchoconstrictior substance or to a neural bronchoconstriction reflex ) * Psychological factors 2/23/2021 copyright (your organization) 2003 9
Clinical features: 2/23/2021 copyright (your organization) 2003 10
• Signs: Grade 1 A Able to carry out work with moderate difficulty. Sleep occasionally disturbed Grade 1 B Only able to carry out work with great difficulty. Sleep frequently disturbed. Grade 2 A Confined to chair or bed but able to get up with moderate difficulty. Sleep disturbed with little or no relief from inhaler. Grade 2 B Confined to chair or bed and only able to get up with great difficulty. Unable to sleep pulse over 130/min. Grade 3 Totally confined to chair or bed no relief from inhaler. Pulse over 120/min. Grade 4 Immobilized and completely exhausted. 2/23/2021 copyright (your organization) 2003 11
Laboratory Finding Changes in lung mechanics *Reduction in airway diameter. *Increase in airway resistance With primary alteration in pulmonary mechanics and secondary changes in gas exchange. Pulmonary function tests are useful in that one can measure the degree of obstruction present it is reversible nature and demonstrate the air way hyper reactivity when combined with provoking factors. 2/23/2021 FEV and FVC In patient with asthma 1 st second FEV 30% also increase more than 20% in FEV Peak Expiratory Flow rate (PEFR) Lung volumes Variability of greater than 1520% in PEFR in a single day or from day to day is very suggestive of asthma and lowest value are recorded in early morning copyright (your organization) 2003 12
The End 2/23/2021 copyright (your organization) 2003 13
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