Asthma

Question 1

Intro

what, presents as, peak incidence

Answer 1

• Chronic inflammation of the airways - due to a type 1 hypersensitivity reaction after exposure to triggers
• Presents as REVERSIBLE AIRWAY OBSTRUCTION due to narrowing ariways
• More common in children

Question 2

Aetiology

Answer 2

• GENETIC PREDISPOSITION - antigen exposure causes IgE production (atopy)
• ENVIRONMENTAL FACTORS - passive smoking increases exposure and hygeine hypothesis says cleaner envts cause IgE response to allergens

Question 3

Causes

Answer 3

• allergens - pollen, pets, mould
• drugs causing wheeze - NSAIDs (aspirin), B-blockers, penicillin
• dust, fumes, vapour - smoking, perfume, air pollution
• cold air
• occupational agents - flour, paint
• viral infections - rhinovirus, RSV, parainfluenza

Question 4

risk factors

Answer 4

• personal/family history of atopy
• antenatal factors - maternal smoking
• low birth weight
• not breastfed
• passive smoking in childhood
• obesity
• air pollution
• increased exposure to triggers
• respiratory infections in infancy
• hygeine hypothesis

Question 5

pathophysiology

Answer 5

Type 1 hypersensitivity reaction
= allergens stimulate type 2 helper T cells to rpoduce cytokines
= causes inflammation of airways
= bronchial hyperresponsiveness and reversible bronchoconstriction

Question 6

symptoms

Answer 6

• wheezing
• cough - worse at night, non-productive
• shortness of breath on exertion
• chest tightness

Question 7

signs

Answer 7

• expiratory wheeze on auscultation
• reduced PEFR

Question 8

complications

Answer 8

reversible airway remodelling
- hypertrophy of SMC and mucous glands
- oedema, scarring, fibrosis

airway narrowing
- V/Q mismatch
- reduced ventilation of affected alveoli

Question 9

mild/moderate asthma can lead to

Answer 9

type 1 respiratory failure

low O2 and low CO2

where pt hyperventilates to blow off the excess CO2 (inc resp rate)

Question 10

progression to severe asthma is noticed when

Answer 10

pt can’t complete sentences in one breath

Question 11

life threatening asthma can lead to

Answer 11

type 2 respiratory failure

high CO2 and low O2

where more airways are narrowed so bronchoconstriction

Question 12

asthma exacerbations can be measured by

Answer 12

PEFR of best/predicted value

Question 13

grading severity of asthma exacerbations

Answer 13

MODERATE
- PEFR >50-75%
- RR < 25/min
- pulse < 110 bpm
- normal speech
- increasing symptoms but no features of acute severe asthma

ACUTE SEVERE (type 1 resp failure)
- PEFR 33-50%
- RR > 25/min
- low CO2 (inc resp rate, hyperventilating so blowing off CO2)
- pulse > 110 bpm
- inability to complete sentences in one breath

LIFE THREATENING (type 1 resp failure)
- PEFR < 33%
- O2 sats <92%
- normal CO2 (4.6-6kPa)
- low O2 (<8kPa)
- silent chest
- cyanosis
- feeble respiratory effort
- bradycardia, arrhythmia, hypotension
- exhaustion, confusion, coma

NEAR FATAL (type 2 resp failure)
- raised CO2 (no gas exchange as more bronchoconstriction)
- require mechanical ventilation with raised inflation pressures

Question 14

treating different severities

Answer 14

ACUTE SEVERE ASTHMA
- oxygen
- B2 agonists
- M2 antagonist (lungs) eg. ipratropium - antimuscarinic
- corticosteroids eg. prednisolone

LIFE THREATENING/NEAR FATAL
- move to ITU
- maybe need mechanical ventilation