Pathophysiology of bronchial asthma Flashcards
What is bronchial asthma
Chronic airway inflammation, associated with airway hyper responsiveness
B. Asthma leads to…
bronchoconstriction (Reversible) and airflow limitation
Clinical manifestation of bronchial asthma ?
Recurrent episodes of wheezing, breathlessness, chest tightness, and coughing, particularly at night or in the early morning.
What is Airway hyper-reactivity
the tendency for airways to narrow excessively
in response to triggers that have little or no effect in normal individuals
Types of asthma?
- Atopic asthma
- Non-atopic asthma
Non-atopic asthma ..
- Drug-induced asthma
- Exercise-induced asthma
- Occupational asthma
Causes of atopic asthma?
Causes: environmental allergens, such as dusts, pollens, cockroach or animal dander, and foods
Causes of Non- atopic asthma?
✓ Respiratory viral infections,
✓ Air pollutants, e.g., tobacco smoke,
✓ Cold air, stress, exercise
Mechanism of Non-atopic asthma ?
- Chronic airway inflammation and hyperreactivity
- Skin test - negative
Drug-Induced Asthma
- Aspirin and non-steroidal anti-inflammatory drugs
- Beta-adrenoceptor antagonists (β-blockers)
- Oral contraceptive pill
- Cholinergic agents
- Prostaglandin F2α
- Betel nuts contain arecoline
Cause of occupational asthma?
Causes: fumes (epoxy resins, plastics), organic and chemical dusts (wood, cotton, platinum), gases (toluene), or other chemicals (formaldehyde, penicillin products).
Mechanism of occupational asthma ?
1) Type I hypersensitivity
2) Direct production of bronchoconstrictor substances
3) Hypersensitivity responses of unknown origin
Mast cells release preformed mediators. Role preformed mediators?
1) Bronchospasm
2) Increased vascular permeability
3) Mucus production
4) Recruitment of leukocytes
Leukotrienes C4, D4, and E4
1) Prolonged bronchoconstriction
2) Increased vascular permeability
3) Increased mucus secretion
Acetylcholine
- Released from intrapulmonary parasympathetic nerves
- Bronchoconstriction by directly stimulating muscarinic receptors
IL-5 are associated with
peripheral blood eosinophilia
Galectin-10 (GAL10)
is released from eosinophils and forms
Charcot-Leyden crystals
These crystals is a…
Strong inducers of inflammation and
mucus production
Histamine cause?
bronchospasam
Prostaglandin D2 cause?
bronchospasm and vasodilation
Platelet activating factor cause?
Platelet aggregation and release serotonin
Bronchial asthma phatogenesis?
- Immune response
- Genetic susceptibility
- Environmental Factors
Airborne pollutants can serve as
allergens to initiate the Th2 response
Infections do not cause asthma by themselves but
may be important co-factors
viral and bacterial infections are associated with
acute exacerbations of the disease
Morphology of acute severe asthma (status asthmaticus)
Gross & Histology
Gross of acute severe asthma
- Overinflated lungs with small areas of atelectasis
- Occlusion of bronchi and bronchioles by thick, tenacious mucus plugs, which often contain shed epithelium.
Sputum or bronchoalveolar lavage contains ….
1) Curschmann spirals - mucus plugs from subepithelial mucous gland ducts or bronchioles
2) Charcot-Leyden crystals - eosinophil-derived protein galectin-10
Histology of acute severe asthma
Numerous eosinophils
Cause of Airway remodeling
Repeated bouts of allergen exposure
Airway remodelling results in:
1) Bronchial smooth muscle hypertrophy and hyperplasia
2) Epithelial injury
3) Increased airway vascularity
4) Subepithelial mucous gland hypertrophy
5) Subepithelial fibrosis (deposition of type I and III collagens)
Acute airflow obstruction is primarily due to
- bronchocospasm
- acute edema
- mucus plug
Chronic irreversible airway obstruction may be due
Airway remodeling
What are the Clinical Features of acute asthmatic attack?
- Lasts up to several hours
- Recurrent episodes of wheezing, dyspnea, chest tightness, and cough
- Precipitants: exercise (particularly in cold weather), airborne allergens
or pollutants, and viral upper respiratory tract infections
What are the Diagnosis of acute asthmatic attack?
- Difficulty with exhalation (prolonged expiration, wheeze)
- An increase in airflow obstruction – spirometry, peak flow meter
- Atopic asthma – eosinophilia, Curschmann spirals, and Charcot-Leyden crystals in the sputum, skin prick test
Exacerbations of Asthma: Precipitant?
viral infections, moulds, pollens, and air pollutants
Clinical feature of
