Asthma
Summary
Asthma is a chronic inflammatory disease of the airways characterised by variable expiratory airflow limitation, bronchial hyperresponsiveness, and respiratory symptoms that vary over time and intensity. It affects over 300 million people worldwide and is the most common chronic respiratory condition. Symptoms include wheeze, breathlessness, chest tightness, and cough, typically varying with triggers, time of day, and treatment adherence. The GINA (Global Initiative for Asthma) guidelines recommend a stepwise approach to management with inhaled corticosteroids (ICS) as the cornerstone. Recent GINA updates (2024) recommend ICS-formoterol as the preferred reliever therapy across all severity steps, moving away from SABA-only relievers.
Key Facts
- Definition: Chronic airway inflammation with variable expiratory airflow limitation
- Prevalence: 5-10% adults; 10-15% children
- Pathophysiology: Th2-driven eosinophilic inflammation, reversible bronchospasm
- Diagnosis: Reversible airflow obstruction on spirometry (≥12% and ≥200mL increase post-bronchodilator)
- Cornerstone Treatment: Inhaled corticosteroids (ICS)
- Preferred Reliever (GINA 2024): ICS-formoterol PRN
- Goals: Symptom control, normal activity, prevent exacerbations, minimise side effects
Clinical Pearls
"No ICS = No Asthma Controller": Every patient with asthma should have ICS in their regimen. SABA-only use is associated with increased mortality.
"ICS-Formoterol Revolution": GINA 2024 recommends ICS-formoterol as the preferred reliever for all steps, reducing exacerbations and avoiding the need for SABA.
"Asthma Deaths are Preventable": Most asthma deaths occur in patients with poor control, excessive SABA use, and inadequate ICS. Education and adherence are key.
Why This Matters Clinically
Asthma is common, costly, and causes significant morbidity. Well-controlled asthma allows a normal life. Poor control leads to exacerbations, hospitalisations, and preventable deaths. Appropriate treatment and patient education save lives.
Prevalence
| Population | Prevalence |
|---|---|
| Global | 300+ million affected |
| Adults (UK) | 5-10% |
| Children (UK) | 10-15% |
| Developed countries | Higher prevalence |
Demographics
| Factor | Details |
|---|---|
| Age | Peak in childhood; second peak in adulthood |
| Sex | Boys > Girls (childhood); Women > Men (adulthood) |
| Ethnicity | Higher morbidity in Black populations |
Risk Factors
| Factor | Details |
|---|---|
| Atopy | Strongest risk factor (eczema, allergic rhinitis) |
| Family History | Genetic predisposition |
| Early Viral Infections | RSV, rhinovirus |
| Tobacco Smoke Exposure | In utero and childhood |
| Obesity | Associated with more severe asthma |
| Occupational Exposures | Isocyanates, flour, animal allergens |
Mechanism
Step 1: Allergen/Trigger Exposure
- Inhaled allergens (dust mites, pollen, pet dander)
- Viral infections, cold air, exercise, irritants
Step 2: Th2-Driven Inflammation
- Dendritic cells present allergen to T cells
- Th2 cytokines released (IL-4, IL-5, IL-13)
- Eosinophil recruitment
- Mast cell activation
Step 3: Airway Effects
- Bronchospasm (smooth muscle contraction)
- Mucosal oedema
- Mucus hypersecretion
- Bronchial hyperresponsiveness
Step 4: Airway Remodelling (Chronic)
- Subepithelial fibrosis
- Smooth muscle hypertrophy
- Goblet cell hyperplasia
- Fixed airflow obstruction
Key Inflammatory Cells
| Cell | Role |
|---|---|
| Eosinophils | Central effector cell; marker of Type 2 inflammation |
| Mast Cells | Release histamine, leukotrienes (acute phase) |
| Th2 Cells | Orchestrate inflammation via cytokines |
| Epithelial Cells | Source of TSLP, IL-33, IL-25 (alarmins) |
Symptoms
Triggers
| Trigger | Examples |
|---|---|
| Allergens | Dust mites, pollen, pets, mould |
| Infections | Viral URTIs |
| Exercise | Especially cold, dry air |
| Irritants | Smoke, pollution, strong odours |
| Weather | Cold air, humidity changes |
| Drugs | NSAIDs, beta-blockers |
| Emotions | Stress, laughter |
Signs
Red Flags
[!CAUTION] Life-Threatening Asthma Features:
- PEF <33% best or predicted
- SpO2 <92%
- Silent chest, poor respiratory effort
- Cyanosis
- Bradycardia, arrhythmia, hypotension
- Exhaustion, confusion, altered consciousness
- ABG: Normal or raised PaCO2 (indicates fatigue)
Structured Approach
General:
- Respiratory distress, posture (tripod)
- Ability to speak (sentences, words, or unable)
- Cyanosis
Vital Signs:
- RR, HR, SpO2, BP, Temp
- PEF measurement
Chest:
- Inspection: Hyperinflation, accessory muscle use
- Palpation: Reduced expansion
- Percussion: Hyperresonant
- Auscultation: Expiratory wheeze, prolonged expiration
- In severe attack: Silent chest = EMERGENCY
Severity Assessment (Acute)
| Feature | Moderate | Severe | Life-Threatening |
|---|---|---|---|
| PEF | 50-75% | 33-50% | <33% |
| SpO2 | ≥92% | <92% | <92% |
| Speech | Sentences | Words | Unable |
| RR | Increased | >25 | Variable |
| HR | <110 | >110 | Bradycardia |
| Chest | Wheeze | Loud wheeze | Silent |
Diagnostic Tests
| Test | Purpose | Findings in Asthma |
|---|---|---|
| Spirometry | Objective diagnosis | FEV1/FVC reduced; reversibility ≥12% + 200mL |
| Peak Flow | Monitoring, variability | Diurnal variation >10% |
| FeNO | Eosinophilic inflammation | >50ppb suggests Type 2 inflammation |
| Blood Eosinophils | Phenotyping, biologic eligibility | ≥150-300 for biologics |
| Total IgE | Allergic asthma | Elevated in allergic phenotype |
| Skin Prick Testing | Identify triggers | Allergen sensitisation |
| CXR | Exclude other pathology | Usually normal |
| Bronchial Challenge | If spirometry normal | Positive = hyperresponsiveness |
Acute Exacerbation
| Test | Purpose |
|---|---|
| PEF | Severity assessment |
| SpO2 | Hypoxia |
| ABG | If SpO2 <92% or severe attack |
| CXR | Exclude pneumothorax, infection |
GINA Stepwise Approach (2024)
Preferred Track (ICS-Formoterol):
- All steps: ICS-formoterol as reliever (replaces SABA)
- Step 1: PRN ICS-formoterol only
- Step 2: Low-dose ICS-formoterol as maintenance + PRN
- Step 3-4: Medium-dose ICS-LABA + PRN ICS-formoterol
- Step 5: High-dose + add-ons + biologics
Key Medications:
- ICS: Budesonide, Beclomethasone, Fluticasone
- LABA: Formoterol, Salmeterol
- LAMA: Tiotropium (add-on Step 4-5)
- LTRA: Montelukast (add-on)
Acute Exacerbation Management
| Severity | Treatment |
|---|---|
| Mild-Moderate | High-dose SABA via MDI+spacer or nebuliser; Prednisolone 40-50mg OD for 5 days |
| Severe | Nebulised SABA + Ipratropium; Oxygen; IV hydrocortisone if vomiting; close monitoring |
| Life-Threatening | As above + IV Magnesium Sulphate 1.2-2g; consider IV Aminophylline; ICU |
Non-Pharmacological
- Allergen avoidance
- Smoking cessation
- Weight management
- Inhaler technique education
- Written asthma action plan
- Flu and pneumococcal vaccination
Biologic Therapy (Severe Asthma)
| Biologic | Target | Phenotype |
|---|---|---|
| Omalizumab | Anti-IgE | Allergic asthma |
| Mepolizumab | Anti-IL-5 | Eosinophilic |
| Benralizumab | Anti-IL-5Rα | Eosinophilic |
| Dupilumab | Anti-IL-4/IL-13 | Eosinophilic, atopic |
| Tezepelumab | Anti-TSLP | Broad (any phenotype) |
Acute
| Complication | Notes |
|---|---|
| Pneumothorax | Rare; suspect if sudden deterioration |
| Respiratory Failure | Type 1 or Type 2 (exhaustion) |
| Death | Preventable with appropriate treatment |
Chronic
| Complication | Notes |
|---|---|
| Airway Remodelling | Fixed obstruction |
| Steroid Side Effects | Oral steroids (osteoporosis, diabetes, adrenal suppression) |
| Psychosocial Impact | Anxiety, depression, reduced QoL |
Natural History
Many children with asthma improve or "outgrow" it. Adult-onset asthma tends to persist. With good control, patients have normal life expectancy.
Outcomes
| Variable | Outcome |
|---|---|
| Mortality | ~1,000 deaths/year (UK); preventable |
| Exacerbations | Major driver of morbidity |
| Quality of Life | Excellent if well-controlled |
Poor Prognostic Factors
- Previous near-fatal asthma
- Frequent exacerbations
- Poor adherence
- Smoking
- High SABA use
- No ICS in regimen
Key Guidelines
-
GINA Global Strategy for Asthma 2024 — International gold standard.
-
BTS/SIGN British Guideline on Asthma (SIGN 158) — UK pathway.
Landmark Trials
SYGMA 1 & 2 (2018) — As-needed ICS-formoterol
- Key finding: PRN budesonide-formoterol non-inferior to maintenance ICS for mild asthma
- Clinical Impact: Supports reliever-only ICS-formoterol for mild asthma
NOVEL START (2019) — PRN ICS-formoterol
- Key finding: PRN ICS-formoterol superior to PRN SABA for mild asthma
- Clinical Impact: GINA recommendation shift away from SABA-only
Evidence Strength
| Intervention | Level | Key Evidence |
|---|---|---|
| ICS for asthma control | 1a | Multiple RCTs, Cochrane |
| ICS-formoterol as reliever | 1a | SYGMA, NOVEL START |
| Biologics for severe asthma | 1a | DREAM, SIROCCO, QUEST |
What is Asthma?
Asthma is a long-term condition where your airways are inflamed and sensitive. They can narrow when triggered, making it hard to breathe.
What causes symptoms?
Common triggers include:
- Allergies (dust mites, pollen, pets)
- Colds and chest infections
- Exercise, especially in cold air
- Smoke, pollution
- Strong emotions
How is it treated?
-
Preventer inhalers (brown/orange): Contain steroid medicine to reduce inflammation. Use every day to keep asthma under control.
-
Reliever inhalers (blue or MART): Open your airways quickly when you have symptoms. New guidelines recommend using a "MART" inhaler (combined preventer and reliever) instead of blue reliever alone.
-
Avoid triggers: Identify and reduce exposure to your triggers.
-
Asthma action plan: Written plan showing what to do when symptoms worsen.
What to expect
- With good treatment, most people live completely normal lives
- Annual flu jab is recommended
- Regular reviews with your GP or asthma nurse
When to seek urgent help
Go to A&E or call 999 if:
- Your reliever isn't helping
- You're too breathless to speak
- Your lips or fingers turn blue
- You feel like you can't breathe
Primary Guidelines
- Global Initiative for Asthma (GINA). Global Strategy for Asthma Management and Prevention. 2024. ginasthma.org
Key Trials
-
O'Byrne PM, FitzGerald JM, Bateman ED, et al. Inhaled Combined Budesonide–Formoterol as Needed in Mild Asthma (SYGMA 1). N Engl J Med. 2018;378(20):1865-1876. PMID: 29768149
-
Beasley R, Holliday M, Reddel HK, et al. Controlled Trial of Budesonide–Formoterol as Needed for Mild Asthma (NOVEL START). N Engl J Med. 2019;380(21):2020-2030. PMID: 31112386
Further Resources
- Asthma + Lung UK: asthmaandlung.org.uk
- BTS/SIGN Guideline: brit-thoracic.org.uk
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate guidelines and specialists for patient care.