Asthma — Causes, Symptoms & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

Asthma is a chronic inflammatory condition of the airways characterised by three core pathophysiological features: airway inflammation (eosinophilic and neutrophilic), airway hyperresponsiveness (exaggerated bronchoconstriction in response to triggers), and reversible airflow obstruction (airways narrow during episodes but respond to bronchodilators). It affects approximately 262 million people globally — the most common chronic respiratory disease and one of the most prevalent chronic conditions in children. Clinical features include episodic wheeze, breathlessness, chest tightness, and cough (especially nocturnal and early morning), varying in severity from mild to life-threatening. With appropriate treatment, the vast majority of patients achieve good symptom control and maintain normal lung function. Over 80% of asthma deaths occur in low- and middle-income countries with limited access to inhalers, underscoring global health equity gaps.

Asthma results from a complex interaction of genetic predisposition and environmental exposures. Atopy (genetic tendency to develop IgE-mediated allergies) is the most important predisposing factor — 70-80% of asthma patients are atopic. Common triggers and sensitisers: aeroallergens (house dust mite [most common in UK], grass and tree pollen, pet dander — cat, dog — cockroach, mould), viral respiratory infections (rhinovirus — most common exacerbation trigger), cigarette smoke (active and passive), air pollution (nitrogen dioxide, particulate matter PM2.5, ozone), exercise, cold air, NSAIDs and aspirin (aspirin-exacerbated respiratory disease — 10% of adult asthmatics), beta-blockers, emotional stress, occupational sensitisers (isocyanates, flour dust, latex — occupational asthma). Protective factors: early farm exposure (hygiene hypothesis), breastfeeding, Mediterranean diet, vitamin D sufficiency. The obesity epidemic is driving increasing asthma prevalence — obese asthmatics have worse control and are more likely to have non-eosinophilic (neutrophilic) asthma.

Episodic symptoms: wheeze (musical expiratory polyphonic sound), breathlessness (dyspnoea), chest tightness, and cough — typically worse at night and early morning, worse with triggers (exercise, cold air, allergen exposure, infections). Between episodes, patients may be completely asymptomatic. Atopic symptoms frequently co-exist: allergic rhinitis (affects 80% of asthmatic patients), eczema, food allergy, and urticaria. Acute asthma attack severity: Mild (speaks in sentences, SpO2 >95%, PEF >75% best); Moderate (sentences limited by breathlessness, SpO2 92-94%, PEF 50-75% best, tachycardia); Severe (unable to complete sentences, SpO2 <92%, PEF <50% best, accessory muscle use, tachycardia >110); Life-threatening (silent chest, cyanosis, bradycardia/hypotension, confusion, PEF <33% best, SpO2 <92% despite O2 — near-fatal/status asthmaticus).

Diagnosis is based on characteristic symptoms plus objective evidence of variable airflow obstruction. Spirometry: demonstrates obstructive pattern (reduced FEV1/FVC ratio) — reversibility of more than 12% and 200ml in FEV1 after salbutamol 400mcg confirms asthma. Peak flow monitoring: variability of more than 20% between morning and evening readings over 2-4 weeks supports diagnosis. Bronchial challenge test (methacholine, mannitol, exercise challenge): confirms airway hyperresponsiveness when spirometry is normal — positive when FEV1 falls more than 20% (PC20 < 8 mg/ml methacholine). Fractional exhaled nitric oxide (FeNO): a non-invasive biomarker of eosinophilic airway inflammation — FeNO above 40 ppb strongly supports eosinophilic asthma and predicts steroid responsiveness. Blood eosinophil count: elevated in eosinophilic asthma; guides biologic therapy eligibility. Allergy testing (skin prick tests or specific IgE) identifies allergen sensitisation. Chest X-ray excludes alternative diagnoses (pneumonia, pneumothorax, foreign body).

GINA 2024 stepwise approach: Step 1 (mild intermittent): as-needed low-dose ICS/formoterol (Symbicort, Fostair) — preferred over SABA-only (reduces exacerbation risk). As-needed SABA (salbutamol) as alternative. Step 2 (mild persistent): Regular low-dose ICS (beclometasone 200mcg/day, budesonide 200mcg, fluticasone 100mcg) + as-needed SABA. Step 3 (moderate persistent): Low-dose ICS + LABA (salmeterol, formoterol) — fixed combination (Seretide, Symbicort, Fostair). MART therapy (Maintenance And Reliever Therapy — single low-dose ICS/formoterol inhaler for both preventer and reliever) reduces exacerbation risk by 30-50% and is the preferred Step 3-4 strategy. Step 4 (severe): Medium/high-dose ICS + LABA. Step 5 (very severe refractory): Add-on biologic therapy: mepolizumab, benralizumab (anti-IL-5 for eosinophilic asthma); dupilumab (anti-IL-4/13, FDA-approved for severe eosinophilic asthma and OCS-dependent asthma); tezepelumab (anti-TSLP — broadest biologic, effective across phenotypes). Acute asthma: nebulised salbutamol (2.5-5mg every 20 minutes initially), ipratropium bromide (0.5mg 3 doses in first hour), systemic corticosteroids (prednisolone 40-50mg or IV hydrocortisone 100mg), oxygen to maintain SpO2 94-98%, IV magnesium sulphate 2g for severe/life-threatening asthma. Intubation and ventilation for near-fatal asthma (last resort).

Uncontrolled or severe asthma causes a wide spectrum of complications. Acute life-threatening exacerbations (status asthmaticus): can progress to respiratory failure requiring mechanical ventilation; near-fatal asthma kills over 1,000 people in the UK annually and 455,000 globally. Pneumothorax: rupture of alveoli during severe air trapping can cause spontaneous pneumothorax — presenting as sudden sharp chest pain and worsening dyspnoea. Chronic airway remodelling: persistent uncontrolled inflammation over years causes structural airway changes — subepithelial fibrosis, smooth muscle hypertrophy, goblet cell hyperplasia — leading to fixed airflow obstruction resembling COPD ('asthma-COPD overlap'). Medication side effects: high-dose inhaled corticosteroids cause oral candidiasis, dysphonia, and systemic effects (reduced bone mineral density, adrenal suppression at very high doses); oral corticosteroids used for frequent exacerbations cause weight gain, diabetes, osteoporosis, hypertension, and cataracts. Psychological complications: anxiety and depression are two to three times more common in asthmatic patients than in the general population — poorly controlled asthma and fear of attacks drives significant mental health burden. Exercise limitation and physical deconditioning reduce quality of life substantially.

Identify and avoid personal triggers — maintain a trigger diary. House dust mite reduction: allergen-impermeable mattress and pillow covers, weekly hot washing of bedding (above 60°C), reduce soft furnishings. Avoid pet exposure if sensitised. Use antihistamines and nasal corticosteroid spray for co-existing allergic rhinitis (treating rhinitis improves asthma control significantly). Quit smoking — active and passive smoking worsens asthma control and steroid responsiveness. Achieve and maintain healthy weight — obesity significantly worsens asthma. Annual influenza vaccination is recommended for all asthmatic patients. Ensure correct inhaler technique — poor technique is the most common reason for treatment failure; ask pharmacist for technique check at every review. Written Asthma Action Plan — personalised guide to adjusting therapy based on symptoms/PEF — reduces emergency visits and hospitalisation. Regular GINA-based asthma review every 1-3 months during assessment, 3-6 monthly when controlled.

Call emergency services immediately for a severe or life-threatening asthma attack: inability to speak in sentences, SpO2 below 92%, peak flow below 33% of best, silent chest (no wheeze — airways too tight to generate audible wheeze), blue lips or fingernails, confusion, exhaustion, or collapse. Use your blue reliever inhaler (salbutamol) and call 999/911. Do not drive yourself to hospital. See a doctor urgently for: worsening asthma requiring reliever inhaler more than 2 times per day, night waking from asthma, or any asthma attack requiring more than 2 puffs of salbutamol within 2 hours without improvement. Consult your GP or respiratory nurse if your asthma control has deteriorated, you need to increase your reliever use, or you are concerned about your preventer inhaler effectiveness.