Asthma Pathophys Flashcards
Asthma
- Obstructive disease
- Resistance to the flow of air
through the airways during
inspiration and expiration - FEV1 is <80% significant reduce compare to normal
Factors effecting degree of resistance
- Airway diameter
– Laminar or turbulent flow
Symptoms of asthma
- Dyspnoea
- Wheezing shortness of breath
- Tight chest
- Cough
- Chronic unproductive cough
- Night-time wakening with breathlessness
Asthma effect on airways
- Chronic inflammatory disorder of the airways
- Canbe reversible and induced by many stimuli
- Obstructive disorder
3 main factors of asthma
- Airway constriction
- Airway hypersensitivity and responsiveness
- Mucous hyper-secretion
Causes of asthma: genetic factors
- Cytokine response
profiles
Causes of asthma: Environment
- Allergens
- Pollutants
- Infection
- Stress
- Symptoms and chronic changes
Age impact on asthma
- Altered the immune and adaptive immune response
- Causes symptoms and chronic changes
Genetic impact on inflammation with asthma
- Intrinsic vulnerability interacting due to infection or allergy
- Inflammation depending on phenotype
- Bronchospasm
- Airway remodelling
- Airway obstruction
Allergens effect asthma
House dust mite, pollen,
moulds, animals
Chemicals effecting asthma
- Paints
- Hairspray
Drugs effecting asthma
- Aspirin
- ß-blockers
- NSAIDs
Food triggers of Asthma
- Colouring
- Nuts
- Preservatives
Environmental trigger for asthma
- Smoking
- Wood dust
Extrinsic asthma
- Caused by specific triggers
- Allergens specific trigger
- Smoking and occupational agent
Intrinsic trigger
- Non-specific
- Cold dry air
- Exercise
- Virus
Atopy
- Develop IgE antibodies to common antigens
- 1/3 +ve skin prick test - history of eczema and family history of asthma
- Early onset 98% - skin test
- Late onset 76% - skin test
Hypersensitivity
- Allergen is presented on the dendric cells in lung
- Attach to Th0 helper lympocytes differentiate to Th2 lympocytes
- Activate B cells to make IgE
- Secreate cytokines stim mast cels and endothelial cells attracting eosinophils
Hypersensitivity: Sensitisation
- Antigen present on dendric
- Activate helper T cells change to secrete Th2 cytokines
- Activates B-cells
- Plasma cells secrete antibodies
IgE antibodies
- Binding to Fc receptor on mast cell (granulocytes and some mediators eg histamines)
- Fc region bind to mast cell in lung
Mast degranulation
- Rexposure to allergen
- Allergen bind to IgE on mast cell
- Cross linking Ige RECEPTOR
- Cause mast cell degranulation
- Release histamine and inflammatory mediators (Vasodilation increase mucus)
- Attracts eosinophils
- Stimulate cytokines
Asthma Biphasic (Early phase)
- Increased resistance to airflow
- Peak 30-60 mins after allergen exposure
- Subsidised 30-90 min later
- Drop in peak flow response to inflammatory mediators from mast cells
Asthma biphasic (Late phase)
- Can occour long time after allergen exposure 6+ hrs
- Can cause night time asthma
- Continuation of inflammation
characterised by an influx of eosinophils intothe lungs
Leukotrine
- Immediate constriction of airways and mucus production
- Immediate response (sensitsation and challenge)
Late asthmatic response
- Mucus hypersecreation
- Damage to epithelial can cause airways remodelling
- Caused by eosinophil
Recurrent attacks hyperresponsive
- Days and weks after
- Smooth muscle growth from build up of cytokines
Bronchoconstriction
- Narrowing of airways smooth muscle contraction
- Increased mucous decrease diameter
- Air trapping hyperinflation
Mucous plugging and hyperinflation
- Inspiration of air is allowed into alveolus
- In exhalation the mucus plug can impede exhalation of air flow
- Turbulent air flow around blockage cause characteristics wheezing
Theraputic goals
- Minimum symptoms day and night
- Minimal need for reliever inhaler
- No excerbation
- No limitation to activity and normal lung function
Reliever inhaler
Open the airways of a patient suffering an asthma attack
Preventer inhaler
Intervene in the remodelling
process
Vasodialation and increased permiability
- Inflammation causes swelling of tissue due to OEDEMA
- Swelling and decrease in diameter
