12.1 Asthma

Diagnosing Asthma in Children Under 5

Asthma is a chronic inflammatory disease of the airways characterized by variable, reversible airflow obstruction, bronchial hyperresponsiveness, and recurrent symptoms of wheeze, cough, chest tightness, and dyspnea. It is the most common chronic disease of childhood, and the written paper tests it heavily because both diagnosis and management change with age.

The core diagnostic problem in preschool children is that spirometry -- the objective lung-function test that confirms variable airflow obstruction by demonstrating a reduced forced expiratory volume in 1 second (FEV1) to forced vital capacity (FVC) ratio with reversibility after a bronchodilator -- cannot be performed reliably before about age 5-6, because young children cannot cooperate with the forced expiratory maneuver. Diagnosis under age 5 is therefore clinical, based on a pattern of:

• Recurrent wheeze, cough, or breathlessness, often triggered by viral upper respiratory infections, exercise, laughing, crying, cold air, or allergen exposure
• Symptoms worse at night or in the early morning
• A personal or family history of atopy (eczema, allergic rhinitis, food allergy, or parental asthma)
• A clear symptomatic response to a therapeutic trial of a bronchodilator (often with an inhaled corticosteroid), with relapse when treatment is stopped

Because up to a third of preschoolers wheeze with viral infections and most of them ("transient early wheezers") outgrow it by school age, exam questions favor tools that separate transient wheeze from true asthma. The Asthma Predictive Index (API) is the classic tool: a child with frequent wheezing (four or more episodes in a year) in the first 3 years of life is API-positive if they also have ONE major criterion (parental asthma, physician-diagnosed atopic dermatitis, or aeroallergen sensitization) or TWO minor criteria (food allergen sensitization, wheezing apart from colds, or blood eosinophilia of 4% or more). A positive API strongly predicts persistent asthma at school age.

Severity and Control Classification

Two classifications matter and are frequently confused on exams:

Severity is based on symptom frequency, nighttime awakenings, reliever use, and lung function before any controller therapy is started. Control -- the classification used at every follow-up visit -- asks four simple questions about the preceding 1-4 weeks: daytime symptoms more than twice a week, any nighttime waking, reliever use more than twice a week, and any activity limitation. Zero "yes" answers means well-controlled; 1-2 means partly controlled; 3-4 means uncontrolled. The exam frequently rewards recognizing that ongoing management decisions are driven by control, not by the original severity label.

Stepwise Management: Controller vs. Reliever

Asthma medications fall into two functional classes, and mixing them up is a classic exam trap:

• Reliever (rescue) medication -- a short-acting beta-2 agonist (SABA) such as salbutamol (albuterol), used as-needed for acute symptom relief. It treats bronchospasm but does nothing for the underlying inflammation.
• Controller (maintenance) medication -- chiefly inhaled corticosteroids (ICS), taken daily regardless of symptoms, which treat chronic airway inflammation and are the most effective agents for preventing exacerbations.

Management follows a stepwise ladder that escalates or de-escalates based on the control assessment above:

1. Step 1 -- as-needed SABA only (reserved for infrequent, mild symptoms)
2. Step 2 -- regular low-dose ICS as a controller, plus as-needed SABA
3. Step 3 -- low-dose ICS plus a second controller (a long-acting beta-2 agonist [LABA] in older children, or an increased ICS dose in children under 5, who should not receive a LABA)
4. Step 4-5 -- medium/high-dose ICS-LABA combination, addition of a leukotriene receptor antagonist (montelukast), and referral for severe/refractory asthma (biologic therapy, oral corticosteroids as a last resort)

A leukotriene receptor antagonist such as montelukast is a reasonable alternative controller in young children, particularly for exercise- or virus-induced symptoms, though it is generally less effective than ICS.

Acute Exacerbation Management

Assess severity by respiratory rate, accessory muscle use, ability to speak in sentences, oxygen saturation, and mental status. Initial treatment of a moderate-to-severe exacerbation includes:

• Oxygen to keep saturation at 94% or above
• Repeated doses of SABA (e.g., salbutamol via spacer or nebulizer), given every 20 minutes for up to three doses in the first hour for moderate-to-severe attacks
• Early systemic corticosteroids (oral prednisolone or IV methylprednisolone), which reduce relapse and hospital admission
• Inhaled ipratropium bromide (an anticholinergic) added to SABA in the emergency department for moderate-to-severe exacerbations
• IV magnesium sulfate for severe exacerbations not responding to initial therapy (generally reserved for children aged 2 years and older)
• Admission criteria: persistent hypoxia, poor response after 1-2 hours of treatment, inability to tolerate oral intake or medication, or a history of prior severe/near-fatal attacks

A silent chest, cyanosis, exhaustion, or a confused or drowsy child are red flags for impending respiratory failure and mandate immediate escalation, not simply more bronchodilator.

Spacer and Inhaler Technique

Because inhaler technique failure is a common, correctable cause of "poorly controlled" asthma, know the following:

• A spacer (valved holding chamber) should be used with every pressurized metered-dose inhaler (pMDI) in children -- it removes the need to coordinate actuation with inhalation, improves lung deposition, and reduces oropharyngeal deposition (and thus oral thrush with ICS).
• Infants and toddlers who cannot form a seal around a mouthpiece use a spacer with an attached face mask; children old enough to cooperate (roughly age 4-5 and older) transition to a spacer with a mouthpiece.
• Each puff should be actuated into the spacer one at a time, followed by five to six tidal breaths (or a single deep breath and hold, in cooperative older children) before the next puff.
• A nebulizer is not inherently superior to a pMDI-plus-spacer for delivering bronchodilator -- for mild-to-moderate exacerbations, pMDI with spacer is equally effective and preferred, with nebulizers reserved for severe distress or a child unable to use a spacer effectively.
• After ICS use, rinsing the mouth (and regularly washing the face mask or spacer) reduces local side effects such as oral candidiasis and hoarseness.