Paeds: Asthma HW Flashcards
Definition
A reversible airway obstruction
Epi
- 300 million people worldwide
- Childhood: M>F
- Post puberty: F>M
Cause
- Atopy and allergy
- Combination Genetic predisposition and environmental influences
- Other possibilities
Other causes
- Hygiene hypothesis: reduced infections in early life bias immune system towards allergic phenotype - Th2. T lymphocytes may differentiate into Th1 (fights virus/bacteria) or Th2 (allergic response)
- Warm, humid, centrally heated homes = multiplication of dust mites.
- Obesity - Asthma due to mechanical mechanisms e.g. GORD
Pathophysiology
Environmental factors and Genetic predisposition
Environmental factors and genetic predisposition leads to
- Bronchial inflammation
- Bronchial hyper-reactivity and trigger factors
- Oedema, bronchoconstriction, increase mucus production and smooth muscle hypertrophy
- Airways narrowing and obstruction
Symptoms
Cough
Wheeze
Breathlessness
Tight chest
Trigger factors for bronchial hyper-reactivity and trigger factors
- URTI
- Allergens
- Smoking (active/passive)
- Cold air
- Exercise
- Emotional upset/excitement
- Chemical irritants
Pathogenesis steps 1
- Mast cell increase and degranulate
- Th2 process driven
3. Mediators released- Histamine and cysteinyl leukotrienes
Pathogenesis Step 2
- Eosinophils increase and degranulate
- Epithelium sheds and attracts more inflammatory cells
- Basement membrane thickens
Pathogenesis Step 3
Increase macrophages and increase lymphocytes
Nerves exposed and release factors that increase cytokines
Clinical Features/presentations
- Wheeze (recurrent episodes), Chest tightness, Breathlessness, Cough
- Diurnal pattern
- Nocturnal asthma
- ‘Cough-variant asthma’
- Medication related
- Occupational asthma
Diurnal pattern
symptoms/PEF worse in early morning
Nocturnal asthma
cough and wheeze disturbing sleep
Cough variant asthma
cough dominant symptoms
Medication related
Beta-blockers (may induce bronchospasm), aspirin (associated with rhinosinusitis, nasal polyps), other NSAIDS
Occupational asthma
Considered if working age and symptoms improve during time away from work - increased risk: atopy and smokers.
Mild asthma
Asymptomatic between exacerbations which occur during viral RTI or after exposure to allergens
Persistent asthma
Pattern of chronic wheeze and breathlessness. Long standing obstruction causes pectus carinatum (pigeon chest) and/or Harrison’s sulcus.
Diagnosis
Clinical history with demonstration of variable airflow obstruction.
Investigations
- Pulmonary function tests
- Bronchial challenge test (AHR)
- Exercise test
- Radiological
- Measurement of allergic status
- ABGG’s
- Pulse ox
Pulmonary function tests PEFR
- Record PEFR after rising in morning and before retiring in evening
- Diagnostic: >20% diurnal variation >3 days in a week for 2 weeks on PEF diary - amount of variability is some indication of disease severity.
Pulmonary function tests Spirometry
Detects signs of obstructive airway disease - almost normal/ reduced VC, increased total lung and residual capacities
- Can trial corticosteroids - useful to see improvement in PEFR
- Diagnostic: FEV1 >15% improvement following administration of a bronchodilator/trial of corticoteroids.
Bronchial challenge test (AHR)
- Demonstrates airway hyper-reactivity - due to bronchoconstriction - increased concentrations of histamine/methacholine causes a reduction in FEV1 if asthmatic
- Note: has a high -ve predictive value but +ve results may be seen in other conditions e.g. COPD, CF
Exercise test
- If asthmatic exercise should cause a reduction in PEF/ FEV1
- diagnostic: FEV1>15% reduction after 6 mins of excercise
Radiological
Generally unhelpful but may show alternative diagnosis
Acute asthma signs: Hyperinflation and ± lobar collapse
Measurement of allergic status
- Skin prick tests: Measurement of IgE to confirm sensitivity to specific agent
- Atopic asthma: Increased sputum or peripheral blood eosinophil count and raised serum total IgE
Occupational asthma diagnosis
Diagnosis difficult. Do two-hourly PEF recordings including time away from work. Bronchial provocation tests with suspected agent may be required.
Management
- Medication
2. Patient educatoin
Patient education
- inhaler technique
- Medication - when to use, what each does, frequency, dosage.
- Use of PEF
- Relationship between symptoms and inflammation and important key symptoms e.g. nocturnal waking
- What to do if acute asthma attack
- Avoidance of aggravating factors
- Do not smoke
Atopic disorders
- Asthma
- Eczema
- Allergic rhinitis
- Allergic conjunctivitis
- Urticaria and angiooedema
- Food and drug allergies
Investigations for atopic diagnosis
+ve skin test to common allergens, eosinophilia and raised serum level of IgE
