Asthma

Question 1

Definition

Answer 1

Chronic reversible airway disease characterised by REVERSIBLE AIRWAY OBSTRUCTION secondary to type 1 hypersensitivity reaction = inflamed bronchioles and mucus hypersecretion
- typically presents in children
Allergic/Eosinophilic asthma (70%) - allergens and atopy - IgE = EXTRINSIC
- Pollen, smoke, dust, mould, antigens
- consider genetics and hygiene hypothesis
Non-allergic/non-eosinophilic (30%) - cold air, exercise, stress, obesity = INTRINSIC
- may present later, harder to treat, associated with smoking (like COPD)

Question 2

Epidemiology

Answer 2

Developed countries
5-15 years peak
Pre-pubertal = males
Persistent into adulthood = females

Question 3

Risk factors

Answer 3

Atopy History (atopic triad)
- Atopic rhinitis
- Asthma
- Eczema
Antenatal factors
- maternal smoking
- viral infection during pregnancy
Low birthweight
Exposure to allergens - house dust mites, pollen, smoke
Not breastfed
Smoking around child
Somter’s triad
- nasal polyps
- asthma
- aspirin sensitivity (triggers prostaglandin production -> leukotriene production)

Question 4

Triggers

Answer 4

Infection,
Allergen,
Cold weather,
Exercise,
Drugs (Bb, Aspirin)

Question 5

Pathophysiology

Answer 5

Environmental trigger (smoke)
The antigens are picked up by dendritic cells (APCs) + presented to Th2 cells
Excessive reaction to the allergens by Th2 cells
Release cytokines (IL4, IL5, TNF-a, leukotriene LTB4)
IL-4 triggers production of IgE antibodies = prime mast cells
Next time exposed to allergen, mast cells release granules containing histamine, leukotrienes (cause bronchoconstriction + more potent than histamine) + prostaglandins
IL-5 triggers eosinophils = release more cytokines

Question 6

Signs

Answer 6

Reduced peak expiratory flow rate (PEFR)
Expiratory wheeze on auscultation
Hyper-resonance on percussion
Pulsus paradoxes (dip in BP during insp.)

Question 7

Symptoms

Answer 7

Usually occur at day time but can night
Productive cough
Spiral mucus plugs + is worse at night
Wheeze,
Chest tightness,
Dyspnoea

Question 8

Moderate asthma attack

Answer 8

• PEFR: 50-75%
• RR: < 25
• Pulse: < 110bpm
• Speech Normal

Question 9

Severe

Answer 9

• PEFR: 30-50%
• RR: > 25
• Pulse: >110
• Can’t complete sentences

Children’s ranges
-SpO2 < 92% (unlike in adults, SpO2 < 92% may be consistent with a ‘severe’ attack in children)
-Heart rate
>125 (>5 years)
>140 (1-5 years)
-Respiratory rate
>30 breaths/min (>5 years)
>40 (1-5 years)
-Use of accessory neck muscles

Question 10

Life threatening

Answer 10

• PEFR: <33%
• O2 sats < 92%
• Silent chest, cyanosis or feeble respiratory effort
• Bradycardia, dysrhythmia, or hypotensive
• Exhaustion (normal pCO2), confusion or coma
• Poor respiratory effort

Note that a patient having any one of the life-threatening features should be treated as having a life-threatening attack.

Question 11

Near fatal asthma

Answer 11

• Raised pCO2
• AND/OR requiring mechanical ventilation with raised inflation pressures.

Further assessment
the BTS guidelines recommend arterial blood gases for patients with oxygen sats < 92%
a chest x-ray is not routinely recommended, unless:
- life-threatening asthma
- suspected pneumothorax
- failure to respond to treatment

Question 12

Acute Management: ADULTS

Answer 12

1. Oxygen: 15L of supplemental O2 via non-rebreathe mask, titrated down to a flow rate where they are able to maintain a SpO‚ 94-98%.
2. SABA
   - standard pressurised metered-dose inhaler (pMDI) = Moderate or Severe
   - oxygen-driven nebulizer = LIFE THREATENING
3. Oral prednisolone 40-50mg (continue for 5 days)
4. Ipratropium bromide: in patients with severe or life-threatening asthma
5. IV magnesium sulphate (MgSO4) bronchodilator
6. IV aminophylline
7. HDU transfer: Intubation and ventilation, ECMO

Criteria for discharge:
- Stable on their discharge medication (i.e. no nebulisers or oxygen) for 12-24 hours
- Inhaler technique checked and recorded
- PEF >75% of best or predicted

Question 13

Acute Management: CHILDREN

Answer 13

MILD - MODERATE:
SABA via spacer (< 3 use close fitting mask)
- 1 puff every 30 - 60 seconds up to maximum 10 puffs
- If symptoms are not controlled repeat beta-2 agonist and refer to hospital
Steroid therapy:
- Should be given to all children with asthma exacerbation
- Treatment should be given 3-5 days
- 2-5 years: 20mg OD or 1-2 mg/kg OD
- > 5 years: 30-40mg OD or 1-2mg/kg OD

Question 14

Investigations: ADULTS

Answer 14

FIRST LINE: Eosinophil count or FeNO
- diagnose asthma, without further investigations, if:
= eosinophil is above the reference range
= FeNO is ≥ 50 ppb
SECOND LINE:
- Bronchodilator reversibility (BDR) with spirometry
= FEV1 increase is ≥ 12% and 200 ml or more from the pre-bronchodilator measurement, or
the FEV1 increase is ≥ 10% of the predicted normal FEV1
If spirometry is not available or it is delayed: peak expiratory flow (PEF) twice daily for 2 weeks = PEF variability ≥ 20%
THIRD LINE: Bronchial challenge test

Question 15

Investigations: CHILDREN 5-16

Answer 15

FIRSTLINE: FeNO > 35ppb
SECOND LINE: Bronchodilator reversibility
- FEV1 increase is ≥ 12% from the pre-bronchodilator measurement, or
- FEV1 increase is ≥ 10% of the predicted normal FEV1
IF spirometry is not available or it is delayed: peak expiratory flow (PEF) twice daily for 2 weeks: PEF variability≥ 20%
THIRD LINE: Skin prick testing to house dust mite OR measure total IgE level and blood eosinophil count
FOUTH LINE: Bronchial challenge test

Question 16

Investigations: Children under 5

Answer 16

• Treating with inhaled corticosteroids as per the management guidelines with regular review
• If they still have symptoms at age 5 then attempt objective tests
• Refer to a specialist respiratory paediatrician any preschool child with an admission to hospital, or 2 or more admissions to an emergency department, with wheeze in a 12-month period.

Question 17

Management: ADULTS

Answer 17

STEP 1:
- AIR therapy: Low dose ICS/Formoterol combination inhaler (PRN)
- Highly Sx (e.g. regular nocturnal waking) or Severe exacerbation: Low dose MART
STEP 2: Regular Low dose MART
STEP 3: Regular Moderate dose MART
STEP 4:
- Check FeNO level + blood eosinophil count
= If either is raised then specialist in asthma care
= If both normal = MART + LTRA or LAMA
= If control not improved stop LTRA or LAMA and start alternative medicine (LTRA or LAMA)
STEP 5: Refer to asthma specialist

Question 18

Management: CHILDREN 5-11

Answer 18

STEP1: Paediatric low dose ICS (BD) + SABA (PRN)
Assess if child is suited to MART regime

YES:
- STEP 2: Paediatric low dose MART
- STEP 3: Paediatric moderate dose MART

NO:
- STEP 2: + LTRA (BD) - Trial for 8-12 weeks + stop if ineffective
-STEP 3: Paediatric moderate dose ICS/LABA (BD) + combination inhaler + SABA
(This can be with or without LTRA depending on results of previous trial)

REFERRAL

Question 19

Management: CHILDREN UNDER 5

Answer 19

8 to 12 week trial of twice-daily paediatric low-dose ICS as maintenance therapy + SABA as required
- Consider stopping ICS and SABA treatment after 8 to 12 weeks if symptoms are resolved.
- Review the symptoms after a further 3 months