Asthma

Question 1

Asthma definition

Answer 1

• chronic inflammatory airway disease
• intermittent reversible airway obstruction
• airway hyperreactivity

Question 2

Asthma risk factors

Answer 2

• family history
• allergens
• history of atopy
• nasal polyposis
• obesity
• GORD
• apnoea

Question 3

Asthma pathophysiology (extrinsic)

Answer 3

• first exposure to allergen results in mast cell sensitisation
• second exposure leads to degranulation of the mast cell
• this results in prostaglandin, leukotriene and histamine release
• airway hyperresponsiveness causes smooth muscle contraction
• airway remodelling over time

Question 4

Asthma signs and symptoms

Answer 4

• wheezing
• coughing
• chest tightness
• recurrent dyspnoea
• night waking due to symptoms

Question 5

Asthma diagnosis (over 17)

Answer 5

• spirometry
• bronchodilator reversibility
• FeNO > 40 ppm

Question 6

Asthma diagnosis (5 - 17)

Answer 6

• spirometry and bronchodilator reversibility
• FeNO if normal spirometry or obstructive symptoms and no BDR

Question 7

Asthma diagnosis (< 5)

Answer 7

• clinical judgement
• reversibility test positive if increased forced expiratory volume > 12% / 200ml

Question 8

Asthma obstructive picture

Answer 8

• air cannot be expelled
• increased residual volume and TLC
• low FEV1/FVC ratio
• low FEV1 indicates severity

Question 9

Asthma ABG findings

Answer 9

• early - tachypnoea so blowing off CO2 leads to respiratory alkalosis
• late - respiratory fatigue leads to hypoventilation and respiratory acidosis
• normal or low pH in acute asthma is a warning sign

Question 10

Methacholine challenge

Answer 10

• methacholine = parasympathomimetic
• “rest and digest” so airways constrict (due to muscarinic M3 receptor)
• administer in increasing concentration from 0.016 to 16 mg/m via nebuliser
• measure FEV1 at 30 and 90 seconds
• positive if PD20 ≤ 200 mcg or PC20 ≤ 8 mg/mL

Question 11

BTS guidelines moderate asthma

Answer 11

PEFR 50-75%
speech normal
resp rate < 25
heart rate < 110

Question 12

BTS guidelines severe asthma

Answer 12

PEFR 33-50%
incomplete sentences
resp rate > 25
heart rate > 100

Question 13

BTS guidelines life-threatening asthma

Answer 13

PEFR < 33%
sats less than 92%
normal or low PCO2
silent chest/cyanosis/feeble resp effort
reduced heart/resp rate
dysrhythmia
exhaustion, confusion, coma

Question 14

Asthma management

Answer 14

1. SABA prn
2. Add low dose ICS or cromolyn or montelukast
3. Increase to medium dose ICS
4. Add LABA or montelukast
5. Increase to high dose ICS
6. Add oral steroids

Question 15

Acute asthma investigations

Answer 15

• ABG, repeat in 1 hour if ongoing
• peak flow, repeat 15-30 min after starting treatment
• oxygen saturation
• consider CXR but not routine

Question 16

Acute asthma management

Answer 16

• give oxygen
• give SABA (inhaled or IV)
• give steroid (oral or IV)
• give nebulised ipratropium bromide
• consider MgSO4
• aminophylline IV
• if unresponsive, intubate, ventilate and refer to ITU