Childhood Asthma and Recurrent Wheeze

❍ At a glance

• NZ has one of the highest childhood asthma rates in the world - approximately 15% of children are affected. It is the leading cause of paediatric hospital admissions in NZ.
• Under-5s: most wheeze is viral-induced wheeze, not persistent asthma. Features favouring atopic asthma over viral wheeze include wheeze without viral illness, atopy history, and multiple trigger types. A trial of salbutamol via spacer is both diagnostic and therapeutic.
• Over-5s: step therapy matched to symptom frequency. Step 1 (intermittent): salbutamol via spacer as needed. Step 2 (mild persistent): add low-dose ICS. Step 3: add LABA or montelukast. Always with a spacer - without one, under 10% of the dose reaches the lung.
• Every child with asthma needs a written asthma action plan (AAP), reviewed at least annually. This reduces hospital admissions.
• Severe exacerbation: SpO2 below 92%, single-word speech, silent chest, altered consciousness. Call 111, give salbutamol immediately.

❍ Diagnosis: under-5s and the wheeze distinction

Diagnosing asthma in children under 5 is clinically challenging because wheeze is common in this age group and most young wheezers do not go on to have persistent asthma. Viral-induced wheeze - episodic wheeze triggered by URTI that resolves between episodes - does not require regular preventer therapy and should not be labelled as asthma. Features that favour atopic asthma over viral wheeze include:

• Wheeze in the absence of viral illness
• Personal or family history of atopy (eczema, allergic rhinitis, food allergy)
• Multiple trigger types (cold air, exercise, allergen exposure)
• Persistent symptoms between episodes

A trial of salbutamol via MDI and spacer is both diagnostically and therapeutically useful in young children: a clear clinical response supports a bronchospasm diagnosis. Consider alternative diagnoses - foreign body, tracheomalacia, vascular ring - if wheeze is fixed, unilateral, or unresponsive to bronchodilator.

❍ Diagnosis: over-5s

In children over 5, diagnosis is more reliable. Classic features include: episodic wheeze, chest tightness, cough (particularly nocturnal), and breathlessness; symptoms triggered by exercise, allergen exposure, cold air, or viral illness; symptoms that vary in time and intensity; diurnal variation with worse symptoms in the morning or at night.

Spirometry can confirm the diagnosis in cooperative children over 5-6 years. An FEV1/FVC ratio below the lower limit of normal, with a 12% or greater improvement in FEV1 after salbutamol, is diagnostic of bronchospasm.² Spirometry is not always necessary when the history is typical and there is a clear bronchodilator response clinically.

Alternative diagnoses to consider if the picture is atypical: wheeze that is mainly inspiratory (laryngeal or extrathoracic obstruction), wheeze with no well interval, wheeze that does not respond to bronchodilator, or features suggesting structural airway disease. Refer to paediatrics for further assessment (CT chest, flexible bronchoscopy) if an alternative diagnosis is possible.

❍ Long-term management: stepwise therapy

All children using inhaled medication should use a valved holding spacer. Without one, under 10% of the dose reaches the lower airway. Check spacer technique at every visit.

Step 1 (mild intermittent): salbutamol MDI via spacer as needed. Educate on symptom recognition and when to use reliever.

Step 2 (mild persistent - symptoms more than twice per week, or nocturnal symptoms more than twice per month): add regular low-dose inhaled corticosteroid (ICS). First-line in NZ: budesonide (Pulmicort) 100-200 mcg twice daily or beclometasone 100 mcg twice daily. Step down after 3 months of good control - use the minimum effective dose.²

Step 3 (moderate persistent, not controlled on low-dose ICS): options include increasing ICS to medium dose, adding a long-acting beta-2 agonist (LABA - not to be used without ICS in children), or adding montelukast (4 mg for ages 2-5, 5 mg for ages 6-14). Paediatric review is appropriate before initiating Step 3 in under-5s.

Steps 4-5: specialist paediatric respiratory management.

Written asthma action plans (AAPs) reduce hospital admissions and emergency presentations.⁴ Every child with asthma should have a current written AAP, reviewed at least annually and at any significant change in management.

❍ Acute exacerbations

Assess severity first:

• Mild: talks in sentences, SpO2 ≥95%, no significant recession
• Moderate: talks in phrases, SpO2 92-95%, visible intercostal or subcostal recession
• Severe: single words or unable to speak, SpO2 below 92%, silent chest, cyanosis, altered consciousness

For mild-to-moderate exacerbations in primary care: oxygen to maintain SpO2 above 94%. Salbutamol 2-10 puffs via MDI and spacer (each actuation given separately, wait 30 seconds between puffs), repeated every 20 minutes for up to 3 doses in the first hour. Oral prednisolone 1-2 mg/kg (max 40 mg) for 3 days. If not responding after the initial doses, refer to secondary care.

Severe exacerbation: call 111 immediately. Give salbutamol while waiting. These children deteriorate quickly.

❍ Triggers, referral, and equity

Common triggers include viral respiratory infections (the most common exacerbation trigger in children), exercise, allerg