Acute exacerbation of COPD (AECOPD)
"An exacerbation is an acute worsening of dyspnoea, cough and/or sputum beyond normal day-to-day variation. Every precipitant does the same thing — narrows airways, worsens airflow limitation and drives dynamic hyperinflation, which in turn produces the hypoxaemia and hypercapnia that bring the patient to the ICU."
Summarised from Irwin & Rippe's Intensive Care Medicine; with Marino's The ICU Book, Oh's Intensive Care Manual and GOLD.COPD is defined by persistent airflow limitation (post-bronchodilator FEV₁/FVC <0.7). The ICU sees the severe end: respiratory failure that is a mix of lung failure (V/Q mismatch, shunt) and pump failure (fatigued muscles working against hyperinflation).
What triggers an exacerbation
| Trigger | Note |
|---|---|
| Respiratory infection (viral/bacterial) | The commonest cause; drives sputum change |
| Air pollution / environmental | Linked to symptoms and mortality |
| Non-adherence / undertreatment | Missed inhalers, poor technique |
| Comorbid triggers | Heart failure, PE, pneumothorax, arrhythmia — always exclude |
| ~30% unknown | A subgroup is eosinophilic (steroid-responsive) |
"Exacerbations beget exacerbations." A previous exacerbation is the strongest predictor of the next — and always exclude the mimics (PE, pneumothorax, decompensated heart failure) before blaming COPD.
Dynamic hyperinflation & auto-PEEP
Airflow limitation worsens
Bronchospasm, mucosal oedema and secretions narrow already-diseased small airways; expiratory flow falls.
Incomplete exhalation → gas trapping
The next breath starts before the last is exhaled → dynamic hyperinflation and auto-PEEP (intrinsic PEEP).
Mechanical & haemodynamic penalty
Flattened diaphragm at a mechanical disadvantage → ↑ work of breathing; raised intrathoracic pressure → ↓ venous return → hypotension.
Gas-exchange failure
V/Q mismatch → hypoxaemia; muscle fatigue + increased dead space → hypercapnia & respiratory acidosis (Type 2 failure).
Rapid assessment
| Do | Looking for |
|---|---|
| ABG | Type 2 failure, pH (acidosis = NIV trigger), baseline compensation |
| CXR | Pneumonia, pneumothorax, oedema, hyperinflation |
| ECG / troponin / BNP | Arrhythmia, ischaemia, cor pulmonale, heart failure |
| Bloods / cultures / CRP | Infection, eosinophils, electrolytes |
| Consider CTPA | PE is common and frequently missed in AECOPD |
Pharmacological management
| Therapy | Detail | Note |
|---|---|---|
| Controlled oxygen | Target SpO₂ 88–92% (Venturi 24–28%) | Avoid hyperoxia — it worsens hypercapnia (V/Q + Haldane) |
| Short-acting bronchodilators | SABA (salbutamol) + SAMA (ipratropium), nebulised | Drive nebs with air (not O₂) if CO₂ retainer |
| Systemic corticosteroid | Prednisolone 40 mg/day × 5 days (or IV equivalent) | Shortens recovery; short course (REDUCE) |
| Antibiotics | If ↑ sputum purulence + ↑ volume/dyspnoea (Anthonisen), or ventilated | Cover common respiratory pathogens per local policy |
| Adjuncts | IV magnesium; treat the trigger; VTE prophylaxis | Avoid sedatives in the unsupported hypercapnic patient |
From NIV to the ventilator
"Non-invasive ventilation is the single intervention that most changes outcome in the acidotic hypercapnic exacerbation — it lowers intubation, length of stay and mortality. Invasive ventilation is a rescue, and its whole art is giving enough minute ventilation while avoiding gas trapping."
Summarised from Irwin & Rippe; Oh's Intensive Care Manual; ERS/ATS.| Modality | When | Key point |
|---|---|---|
| NIV (BiPAP) | First line for respiratory acidosis (pH <7.35 with hypercapnia) despite initial therapy | IPAP to offload work & clear CO₂; EPAP to counter auto-PEEP; reassess in 1–2 h |
| HFNO | Hypoxaemia, NIV intolerance/breaks | Comfort, secretion clearance, some CO₂ washout |
| Invasive ventilation | NIV failure/contraindication, ↓ consciousness, arrest, exhaustion | See strategy below |
- Prolong expiration: low rate (10–14), high inspiratory flow, short Ti, I:E 1:3–1:4.
- Modest tidal volume (~6–8 mL/kg PBW); accept permissive hypercapnia.
- Watch auto-PEEP (expiratory hold); set applied PEEP below intrinsic PEEP to ease triggering.
- Sudden hypotension → suspect dynamic hyperinflation → disconnect and let the chest deflate (exclude pneumothorax).
Getting off, and staying off
- Weaning: daily spontaneous breathing trials; extubate to NIV in hypercapnic patients to prevent re-intubation; consider tracheostomy if prolonged.
- Prevention bundle: smoking cessation, inhaler optimisation & technique, vaccination, pulmonary rehabilitation, long-term O₂ if chronically hypoxaemic, and an exacerbation action plan.
Common mistakes
Driving SpO₂ to 100% worsens hypercapnia and can cause narcosis. Target 88–92% with controlled devices.
NIV works best started early for pH <7.35 — waiting costs intubations and lives.
Short expiration → auto-PEEP → hypotension. Use low rates and long expiratory times.
PE, pneumothorax and heart failure masquerade as "just COPD" — actively exclude them.
Sedatives blunt respiratory drive in the unsupported hypercapnic patient — support the airway instead.
Exam pearls
Q: Oxygen target in AECOPD and why?
SpO₂ 88–92%. Hyperoxia worsens hypercapnia through V/Q redistribution, the Haldane effect and reduced hypoxic drive.
Q: When is NIV indicated?
Respiratory acidosis (pH <7.35) with hypercapnia persisting after initial medical therapy — first-line, reduces intubation and mortality.
Q: Steroid regimen?
Prednisolone 40 mg/day for 5 days (REDUCE) shortens recovery without benefit from longer courses.
Q: Ventilator strategy?
Prolong expiration (low rate, high flow, I:E 1:3–1:4), modest Vt, permissive hypercapnia, watch auto-PEEP; disconnect if it causes shock.
Q: Anthonisen criteria for antibiotics?
Increased dyspnoea, sputum volume and sputum purulence — antibiotics if ≥2 (especially purulence) or if ventilated.
All the comparisons in one place
The distinctions that decide management and win vivas — gathered at the end.
COPD vs Asthma (acute)
| Feature | COPD | Asthma |
|---|---|---|
| Age / history | Older, smoker, chronic | Any age, atopy, episodic |
| Airflow limitation | Largely fixed | Largely reversible |
| Baseline gases | Often chronic CO₂ retention | Usually normal between attacks |
| CO₂ in attack | Rises early | Low early; a rising/normal CO₂ is ominous |
| NIV role | Strong (first line for acidosis) | Limited/cautious |
Type 1 vs Type 2 respiratory failure
| Feature | Type 1 (hypoxaemic) | Type 2 (hypercapnic) |
|---|---|---|
| PaO₂ | Low | Low |
| PaCO₂ | Normal/low | High |
| Mechanism | V/Q mismatch, shunt | Alveolar hypoventilation / pump failure |
| COPD relevance | Early/mild | The classic decompensation |
Emphysema vs Chronic bronchitis
| Feature | Emphysema ("pink puffer") | Chronic bronchitis ("blue bloater") |
|---|---|---|
| Pathology | Alveolar destruction, loss of recoil | Mucus gland hyperplasia, productive cough |
| Appearance | Thin, pursed-lip, less cyanosed | Cyanosed, oedematous, cor pulmonale |
| Gases | Relatively preserved until late | Earlier CO₂ retention / hypoxaemia |
NIV vs Invasive ventilation in COPD
| Feature | NIV | Invasive |
|---|---|---|
| Best candidate | Awake, cooperative, pH 7.25–7.35 | Coma, arrest, exhaustion, NIV failure |
| Evidence | ↓ intubation, LOS, mortality | Rescue; higher complication burden |
| Main risk | Delay to intubation if failing | Auto-PEEP, VAP, difficult weaning |
References
- Irwin RS, Lilly CM, Mayo PH, Rippe JM (eds). Irwin & Rippe's Intensive Care Medicine. 9th ed. Wolters Kluwer; 2023.
- Marino PL. Marino's The ICU Book. 5th ed. Wolters Kluwer; 2025.
- Bersten AD, Handy JM (eds). Oh's Intensive Care Manual. Elsevier; 2026.
- Global Initiative for Chronic Obstructive Lung Disease (GOLD). Global Strategy for Prevention, Diagnosis and Management of COPD — 2026 Report.
- Rochwerg B, Brochard L, Elliott MW, et al. ERS/ATS guidelines: non-invasive ventilation for acute respiratory failure. Eur Respir J. 2017;50:1602426.
- Leuppi JD, Schuetz P, Bingisser R, et al. (REDUCE). Short-term vs conventional glucocorticoid therapy in AECOPD. JAMA. 2013;309:2223–2231.
- Anthonisen NR, Manfreda J, Warren CP, et al. Antibiotic therapy in exacerbations of COPD. Ann Intern Med. 1987;106:196–204.