2 Asthma

How asthma affects the airways

Asthma symptoms include wheeze, shortness of breath, chest tightness, and cough. They vary over time and in intensity. During an episode, three processes can narrow the airways:

• Bronchoconstriction: airway smooth muscle tightens.

• Airway-wall swelling: inflammation increases wall thickness and sensitivity to triggers.

• Mucus production: excess or thick mucus further obstructs airflow.

These changes make breathing out difficult and may cause air trapping. Recurrent inflammation can lead to structural airway changes, called airway remodeling, and persistent airflow limitation in some people. The combination and importance of these mechanisms vary among people with asthma.

Potential triggers include viral infections, allergens, smoke or vaping, exercise, air pollution, and some medicines.

Assessing control and exacerbation severity

Assess both current symptom control and future risk. When assessing symptom control, ask about daytime symptoms, night waking, reliever use, and activity limitation over the past $4$ weeks. Also check exacerbation history, lung function, inhaler technique, adherence, exposures, and relevant comorbidities. Symptom frequency alone does not reliably predict a severe attack.

Spirometry is preferred for lung-function assessment. Use peak expiratory flow (PEF) when spirometry is unavailable.

Assessing an acute presentation

An exacerbation is an acute or subacute worsening of symptoms and lung function compared with the person’s usual condition. Assess speech, breathing effort and rate, air entry, pulse, oxygen saturation, and PEF when feasible. Consider other causes of breathlessness, including anaphylaxis, pneumonia, pneumothorax, and cardiac disease. For children, use an age-appropriate validated severity score when available.

Presentation findings that may indicate severity include:

• Mild: speaks in sentences; breathing rate is normal or mildly increased; room-air oxygen saturation is usually $\geq 94\%$; PEF is $>70\%$ of personal best or predicted.

• Moderate: speaks in phrases; breathing effort is increased; oxygen saturation is usually $\geq 92\%$; PEF is $50\text{–}70\%$.

• Severe or life-threatening: unable to speak, drink, or lie down; breathing rate is $>30$ per minute; oxygen saturation is $<92\%$; quiet or silent chest; PEF is $<50\%$.

• Acutely life-threatening: drowsiness, confusion, or cyanosis.

Use the worst concerning feature to guide escalation. A quiet chest, altered mental status, or marked hypoxemia is an emergency. Pulse oximetry can overestimate oxygenation in some people with darker skin.

Managing an acute exacerbation

Treat promptly while assessing severity and arranging a higher level of care when indicated. Follow local protocols and individual action plans.

• Severe or life-threatening features: arrange immediate emergency transfer. Give an inhaled short-acting beta-agonist (SABA), add inhaled ipratropium for severe attacks, provide controlled oxygen as needed, and give systemic corticosteroids. If asthma occurs with anaphylaxis, give epinephrine first. Drowsiness, confusion, cyanosis, or a silent chest requires urgent escalation, including intensive-care assessment.

• Mild to moderate symptoms: inhaled albuterol (salbutamol) by pressurized metered-dose inhaler and spacer is commonly used; repeat doses according to severity and response. Add ipratropium for moderate symptoms or inadequate initial response. Give systemic corticosteroids for exacerbations beyond mild.

• Oxygen: titrate to a saturation target of $92\text{–}95\%$ in adults and adolescents, adjusted for altitude and local guidance.

For adults, a typical oral prednisolone course is $40\text{–}50\,\text{mg}$ daily for $5\text{–}7$ days. For children, a typical course is $1\text{–}2\,\text{mg/kg}$ daily, with a maximum of $40\,\text{mg}$, for $3\text{–}5$ days. Dosing and treatment decisions require clinical judgment and local protocols.

Do not routinely order chest X-rays or blood gases, prescribe antibiotics, or use sedatives for an asthma exacerbation.

Reassessment and discharge

Monitor symptoms, oxygen saturation, breathing effort, air entry, and lung function. Reassess within about an hour or sooner if the patient worsens. Transfer to higher-level care if the patient deteriorates or responds inadequately.

Before discharge, confirm sustained improvement, arrange ICS-containing controller treatment, review inhaler technique and adherence, provide a written action plan, and arrange follow-up—usually within days.

Long-term control and review

Inhaled corticosteroid (ICS)-containing treatment is central to preventing attacks, even when symptoms are infrequent. GINA does not recommend SABA-only treatment because it does not treat airway inflammation and is associated with increased exacerbation risk.

For adults and adolescents, GINA’s preferred approach is usually low-dose ICS–formoterol as needed at lower treatment steps. At higher steps, maintenance-and-reliever therapy (MART) uses the same inhaler for maintenance and relief. This approach requires a formoterol-containing combination; other ICS–LABA inhalers are not interchangeable as relievers. Alternative regimens pair daily ICS-containing maintenance treatment with an appropriate reliever. Options for children differ by age and should follow pediatric guidance. Availability, licensing, and local guidelines may vary.

At each review, assess symptoms and exacerbation risk. Check inhaler technique and adherence before stepping treatment up, address relevant triggers, smoking or vaping, and comorbidities, and agree on the patient’s goals. Provide a written action plan explaining how to recognize worsening asthma, adjust prescribed medicines, and seek urgent care.

Once control has been sustained for $2\text{–}3$ months, consider a supervised step-down to the lowest effective treatment. Do not stop ICS-containing treatment without clinical advice.