Asthma Flashcards
Asthma
A chronic inflammatory disorder of the airways characterized by:
- recurring symptoms
- airway obstruction (reversible spontaneously or with treatment)
- bronchial hyper-responsiveness to stimuli
Most common chronic childhood illness
Major cause of school absenteeism, visits to emergency, and hospital admissions
Incidence
1-2 kids in 10 children
More common in boys (until adolescence), then trend reverses
80-90% have symptoms before 4-5 years
2 main types
- recurrent wheezing in early childhood; usually precipitated by viral infections (RSV)
- chronic asthma associated with allergy persisting into later childhood & often adulthood
Classification of Asthma, ages 5-11 years: Step 1
Intermittent Asthma:
- symptoms < 2 days/week
Classification of Asthma, ages 5-11 years: Step 2
Mild Persistent Asthma
- symptoms > 2 times/week, but < once/day
Classification of Asthma, ages 5-11 years: Step 3 or 4
Moderate Persistent Asthma
- daily symptoms
Classification of Asthma, ages 5-11 years: Step 5 or 6
Severe persistent Asthma
- symptoms several times a day
Purpose of Step Classification for Asthma
provides stepwise approach to pharmacologic management, environmental control & educational interventions needed at each step
Etiology
Multifactorial - biochemical, genetic, immunologic, environmental, infectious, endocrine, & psychological factors
Allergy influences persistence& severity of disease -> atopy (IgE - mediated respones to common aeroallergens) is strongest identifiable predisposing factor for developing asthma
BUT: 20-40% have no evidence of any allergic disease and still acquire asthma
Risk Factors (8)
atopy (including hx of allergies or atopic dermatitis)
heredity (e.g., parent/sibling)
Gender (boys > girls until adolescence then girls > boys)
Smoking or exposure to second-hand smoke
Maternal smoking during pregnancy
Ethnicity (african-american at greatest risk)
Low birthweight
Being overweight
Examples of Triggers
Allergens - trees, shrubs, grasses, pollens, air pollution, dust mites, dust, pollens, mould, smoke, sprays
Occupational chemicals
Physical exercise
Cold air
Weather or temperature changes
Environmental change
Cold & infections - viral or bacterial
Animals - cats, dogs, rodents, horses
Medications - aspirin, NSAIDS, antibiotics
Strong emotion - fear, anger, laughing, crying
Foods - nuts, milk, diary
Conditions - GER, TEF
Endocrine factors - menses, pregnancy, thyroid disease
Pathophysiology
Initial release of inflammatory mediators from bronchial mast cells, macrophages, & epithelial cells
Migration & activation of other inflammatory cells
Alterations in epithelial integrity & autonomic neural control of airway tone
Increase in airway smooth muscle responsiveness -> wheezing, dyspnea, & eventual obstruction
Mast cells release histamine which leaks into the airway and then the more severe reaction starts -> brochospasm, airway is getting close and mucus is being produced
Pathophysiology - Obstructive Symptoms
Inflammation & edema of mucous membranes
Accumulation of tenacious secretions from mucous glands
Spasm of smooth muscle of bronchi & bronchioles -> decreases caliber of bronchioles
Could be mucus plugging the alveoli
Two mainstays of treatment: first one deals with diameter of the airway - something to relax the bronchospasm (beta 2 agonist - salbutamol or ventolin)
second one: anticholinergic to clear the mucus (atrovent or ipratropium)
What causes an asthmatic episode?
some asthma triggers are exercise, infection, and allergies. Asthma obstructions airflow through bronchoconstriction and inflammatory changes, narrowing the airway and thus increasing production of mucus. Alveoli may become hyperinflated or collapse because of obstruction, leading to impaired gas exchange.
Pathophysiology: immunologic factors
Allergy is strongest epidemiologic risk factor for chronic asthma morbidity & mortality -> IgE is most active antibody in allergic reactions. Mediates hypersensitive reaction in bronchial mucosa -> specific tissue binding
Immunologic Factors: Release of chemical mediators
Histamine, leukotrienes, platelet-activating factor, prostaglandins, serotonin
Major effect:
- increased permeability of blood vessels
- contraction of smooth muscle
- stimulation of mucous secretion
