L20. Asthma

Question 1

What are the three features of asthma

Answer 1

• Chronic inflammatory disease of the airways causing bronchoconstriction, excess mucus production and swelling of the airway- persistent
• Episodic: Can be symptom free between acute event.
• Life threatening: complete block of airways if severe

Question 2

What are the symptoms of asthma

Answer 2

Wheezing- not only asthma, loudness of wheezing related to sputum plug, cough, sputum production, chest tightness, and breathlessness.
These get worse at night.

Question 3

What is the epidemiology behind asthma

Answer 3

Highest ranking disease in terms of years lost to disability in males- 3rd for female. With females higher prevalance in over 17 age, males under 17 age.

Highest cause of admission to hospital for children
2.5x higher prevalence in Maori and Pasifika

NZ has higher rates of asthma, high cost to the system

Question 4

How do make diagnosis of asthma

Answer 4

1. Wheezing
2. History of episodic- cough, wheeze, dyspnea, chest tightness.
   Reversible airflow limitation
3. Lung function test: evidence of variable airflow obstruction: spirometry, FEV1 reduced more than FVC but both lower values. Post bronchodilator increase of FEV1 400ml – more likely
   Peak expiratory flow for monitoring
4. Eosinophil count in blood 4

Question 5

What are the risk factors for asthma

Answer 5

Viral infection, fur or feathers, dust mites, mould, smoke, pollen, weather: thunderstorm: distibute allergens, emotional expression

+ family history of asthma, history atopic disease, allergic rhinitis, eczema

Question 6

What are some atypical presentation of asthma

Answer 6

Dyspnea without wheezing, chronic cough, increased shortness of breath at night-time, allergic rhinitis with wheezing.

Question 7

What are the two types of asthma

Answer 7

Atopic asthma most common:
early onset in childhood triggered by environmental antigens.
Positive family history- genetic predisposition to TH2 over TH1, often preceded by other hypersensitivity.
Drop in lung function

Nonatopic asthma: late onset; related to mycoplasma and chlamydia pneumoniae respiratory tract infections.
Risk factors: medication induced asthma, NSAIDs,

Question 8

What is the pathophysiology of asthma

Answer 8

Acute phase response: 5-10 min after exposure

1. inhaled allergens directly activate mast cells
2. mast cells release Histamine, cysteinylleukotrienes and PgD
3. This causes bronchoconstriction

• Late phase response: 4-6 hr after exposure
  1. inhale allergen
  2. dendritic cell pick it up, activate TH2 cells
  3. TH2 cells release IL5 which activate eosinophil and IL13 which activate B cell
  4. Eosinophil release IgE and recruit other cells
  4. B cell produce more IgE.
  5. IgE activates Mast cells which leads to bronchoconstriction

3. Dual phase: both so even <50% and longer drop

Question 9

What are some substances present in type 2 asthma that cause some of the symptoms

Answer 9

Broncho constriction: Leukotrienes, PGD2, Ach
Leukotrienes also increase mucus secretion and vascular permeability which generates oedema in the airway
Chemokines recruit inflam cells,
Granule proteins damage epithelium (eg EosinophilCP)