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Flashcards in Paeds: Asthma HW Deck (32):
1

Definition

A reversible airway obstruction

2

Epi

- 300 million people worldwide
- Childhood: M>F
- Post puberty: F>M

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Cause

1. Atopy and allergy
2. Combination Genetic predisposition and environmental influences
3. Other possibilities

4

Other causes

1. 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)
2. Warm, humid, centrally heated homes = multiplication of dust mites.
3. Obesity - Asthma due to mechanical mechanisms e.g. GORD

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Pathophysiology

Environmental factors and Genetic predisposition

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Environmental factors and genetic predisposition leads to

1. Bronchial inflammation
2. Bronchial hyper-reactivity and trigger factors
3. Oedema, bronchoconstriction, increase mucus production and smooth muscle hypertrophy
4. Airways narrowing and obstruction

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Symptoms

Cough
Wheeze
Breathlessness
Tight chest

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Trigger factors for bronchial hyper-reactivity and trigger factors

1. URTI
2. Allergens
3. Smoking (active/passive)
4. Cold air
5. Exercise
6. Emotional upset/excitement
7. Chemical irritants

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Pathogenesis steps 1

- Mast cell increase and degranulate
- Th2 process driven
3. Mediators released- Histamine and cysteinyl leukotrienes

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Pathogenesis Step 2

1. Eosinophils increase and degranulate
2. Epithelium sheds and attracts more inflammatory cells
3. Basement membrane thickens

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Pathogenesis Step 3

Increase macrophages and increase lymphocytes
Nerves exposed and release factors that increase cytokines

12

Clinical Features/presentations

1. Wheeze (recurrent episodes), Chest tightness, Breathlessness, Cough
2. Diurnal pattern
3. Nocturnal asthma
4. 'Cough-variant asthma'
5. Medication related
6. Occupational asthma

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Diurnal pattern

symptoms/PEF worse in early morning

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Nocturnal asthma

cough and wheeze disturbing sleep

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Cough variant asthma

cough dominant symptoms

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Medication related

Beta-blockers (may induce bronchospasm), aspirin (associated with rhinosinusitis, nasal polyps), other NSAIDS

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Occupational asthma

Considered if working age and symptoms improve during time away from work - increased risk: atopy and smokers.

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Mild asthma

Asymptomatic between exacerbations which occur during viral RTI or after exposure to allergens

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Persistent asthma

Pattern of chronic wheeze and breathlessness. Long standing obstruction causes pectus carinatum (pigeon chest) and/or Harrison's sulcus.

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Diagnosis

Clinical history with demonstration of variable airflow obstruction.

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Investigations

1. Pulmonary function tests
2. Bronchial challenge test (AHR)
3. Exercise test
4. Radiological
5. Measurement of allergic status
6. ABGG's
7. Pulse ox

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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.

23

Pulmonary function tests Spirometry

Detects signs of obstructive airway disease - almost normal/ reduced VC, increased total lung and residual capacities
1. Can trial corticosteroids - useful to see improvement in PEFR
2. Diagnostic: FEV1 >15% improvement following administration of a bronchodilator/trial of corticoteroids.

24

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

25

Exercise test

- If asthmatic exercise should cause a reduction in PEF/ FEV1
- diagnostic: FEV1>15% reduction after 6 mins of excercise

26

Radiological

Generally unhelpful but may show alternative diagnosis
Acute asthma signs: Hyperinflation and ± lobar collapse

27

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

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Occupational asthma diagnosis

Diagnosis difficult. Do two-hourly PEF recordings including time away from work. Bronchial provocation tests with suspected agent may be required.

29

Management

1. Medication
2. Patient educatoin

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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

31

Atopic disorders

- Asthma
- Eczema
- Allergic rhinitis
- Allergic conjunctivitis
- Urticaria and angiooedema
- Food and drug allergies

32

Investigations for atopic diagnosis

+ve skin test to common allergens, eosinophilia and raised serum level of IgE

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