Post on 04-Apr-2018
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WHAT IS ASTHMA?
A reversible, obstructive lung disease caused by anexcessive reaction of the airways to certain stimuli ortriggers
Asthma is a disease of airways that is characterized byincreased responsiveness of the tracheobronchial tree tovarious stimuli; resulting in spasmodic narrowing of theair passages
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Asthma is a chronic inflammatory disorder of theairwaysin which many cells and cellular elementsplay a role, in particular, mast cells, eosinophils,T-lymphocytes, macrophages, neutrophils,and epithelial cells.
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Asthma Types
1. Extrinsic (atopic, allergic) asthma
2. Intrinsic (non-atopic, idiosyncratic) asthma
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Extrinsic (atopic, allergic) asthma
Most common type
Begins in childhood or in early adult life
Patients have family history/personal preceding ofallergic
diseases like rhinitis, urticaria, eczema
Hypersensitivity to allergens is usually present
IgE in serum (initiating acute immediate response and a latephase reaction )
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Acute Immediate Response
Initiated by IgE-sensitised mast cells on the mucosal surfa
Mast cells on degranulation release Histamine, LTs, PGs,
PAF, chemotactic factors for eosinophils and neutrophils
Net effects are bronchoconstriction, oedema, mucus
hypersecretion, accumulation of eosinophils and neutrophi
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AllergenIgE
Mast cells (on the mucosal surface)sensitise
Histamine, LTs, PGs, PAF, chemotactic
factors for eosinophils and neutrophils
Degranulate and Release
bronchoconstrictionoedema Mucus hypersecretion
Accumulation of eosinophils and neutrop
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Disease pattern
Episodic --- acute exacerbations interspersed withsymptom-free periods
Chronic --- daily AW obstruction which may be mild,moderate or severe superimposed acute exacerbations
Life-threatening--- slow-onset or fast-onset (fatal withinhours)
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INFLAMMATION
Airflow Limitatio
SYMPTOMS
Cough, WheezeDyspnoea
TRIGGERS
Allergens, Exercise,
Cold Air, SO2 Particulates
Pathogenesis:
Airway
HyperresponsivenessGenetic*
INDUCERSAllergens,Chemical sensitiser
Air pollutants, Virus infection
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3 Components of an Asthma Attack
1. Bronchospasm
The smooth muscles that wrap around the
windpipe (bronchi) tighten, reducing the size of the
airway.
normal
Asthma attack
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Components of an
Asthma Attack
2. Inflammation
The mucosal lining of the windpipe becoinflamed and swells, thereby reducing the sizof the airway even further.
3. Mucus
Increased mucus production takes up mo
space; causing airway constriction.
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Pathophysiology
Airway inflammation
Intermittent airflow obstruction
Bronchial hyper responsiveness
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Hypersecretion of mucous
Mucous gland hypertrophy
Mucous is thick
Airways can be blocked by mucous plugs
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Inflamatory cell infiltration
Eosinophils, mast cells, neutrophils, macrophages,
basophils all implicated Lymphocytes, including T-cells
Inflamatory mediators including cytokines
Abnormal antibodies including IgE
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Other constituent airway cells: Fibroblasts
Endothelial cells
Epithelial cells
Contribute to the chronicity of the disease.
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Airway inflammation
Principal cells in airway inflammation include mast cells, eosinophilsepithelial cells, macrophages and activated T lymphocytes.
T lymphocytes release numerous cytokines.
fibroblasts, endothelial cells, and epithelial cells, contribute to thechronicity of the disease.
Adhesion molecules (eg. selectins, integrins) are critical in directing inflammatory changes in the airway.
Finally, cell-derived mediators influence smooth muscle tone andproduce structural changes and remodeling of the airway.
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Airflow obstruction
Can be caused by acute bronchoconstriction, airway edema, chronic mucouplug formation and airway remodeling.
Acute bronchoconstriction results from IgEdependent mediator release upexposure to aeroallergens and is the primary component of the early asthmaresponse.
Airway edema occurs 6-24 hours following an allergen challenge and isreferred to as the late asthmatic response.
Chronic mucous plug formation consists of an exudate of serum proteins ancell debris
Airway remodeling is associated with structural changes due to long-standiinflammation and may profoundly affect the extent of reversibility of airwa
obstruction.
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During acute attack
Antigen antibody interaction
Stimulation/degranulation of mast cells with release of: Histamine Leukotriens
Chemotactic factors Bradykinin
Resulting in: Smooth muscle contraction (decreased camp) Increased capillary permeability, causing edema
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SIGNS AND SYMPTOMS OF AN ASTHMA
ATTACK
Wheezing, coughing
Shortness of breath
Chest tightness
Dry mouth Fatigue
Itchy chin or clipped speech
Headache
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ASTHMA ATTACK TRIGGERS!
Pets Indoorpollution
Exercise
Pollens
Weather