Acute Exacerbation of COPD
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Direct answer
Acute exacerbation of COPD is a sustained worsening of breathlessness, sputum volume and sputum purulence beyond normal day-to-day variation, graded by Anthonisen criteria to decide on antibiotics. Treatment combines controlled oxygen with a saturation target of 88 to 92 per cent, nebulised bronchodilators, oral prednisolone for five days, and antibiotics for purulent sputum. Non-invasive ventilation is started for respiratory acidosis with pH below 7.35 and PaCO2 above 6.5 kPa.
What you must remember
- Anthonisen criteria: the three cardinal features are increased breathlessness, sputum volume and sputum purulence; all three is type 1, two is type 2, and one with an upper respiratory infection, fever or increased cough is type 3.
- Antibiotics: indicated when sputum purulence is present with one other feature, and in exacerbations needing mechanical ventilation; amoxicillin with clavulanate, doxycycline or a macrolide are common choices, with local resistance guiding selection.
- Controlled oxygen: saturation target 88 to 92 per cent in patients at risk of CO2 retention, delivered by a Venturi mask at 24 to 28 per cent; high-flow oxygen can cause CO2 narcosis.
- Steroids: oral prednisolone 30 to 40 mg daily for five days, with no taper needed for a short course.
- NIV threshold: respiratory acidosis with pH below 7.35 and PaCO2 above 6.5 kPa that persists despite initial medical treatment.
- Bronchodilators: nebulised salbutamol and ipratropium are first line, while theophylline adds little benefit in acute exacerbation.
A 68-year-old smoker with yellow sputum and drowsiness
A 68-year-old man with smoking-related COPD presents with three days of increased breathlessness, a larger sputum volume and yellow sputum. All three Anthonisen features are present, so this is a type 1 exacerbation.
- Start antibiotics and bronchodilators: Antibiotics are indicated, along with nebulised bronchodilators and prednisolone 30 mg daily for five days.
- Titrate oxygen carefully: Oxygen is started through a Venturi mask at 28 per cent and titrated to a saturation of 88 to 92 per cent, because a saturation of 98 per cent could worsen his CO2 retention.
- Check the blood gas: An arterial blood gas taken at one hour shows pH 7.29 and PaCO2 7.8 kPa, which meets the threshold for non-invasive ventilation, so face-mask NIV is started.
- Screen for NIV contraindications: Contraindications such as cardiac arrest, haemodynamic instability, vomiting or an unprotected airway are checked first, because NIV is unsafe in those states.
- Escalate if no improvement: If his pH does not improve on NIV, or his consciousness deteriorates, intubation is considered.
- Plan discharge: Discharge planning follows with inhaled therapy, review of home oxygen needs and pulmonary rehabilitation.
Where the examiner catches the oxygen mistake
The oxygen and NIV questions follow a few predictable traps.
- Trap: giving high-flow oxygen to chase a saturation of 98 per cent Correct: this reflex can precipitate severe hypercapnia in a breathless COPD patient.
- Trap: accepting a raised PaCO2 as normal for COPD Correct: the pH must be read alongside the PaCO2 before a raised value is called acceptable.
- Trap: choosing NIV by saturation alone Correct: the threshold is defined by pH and PaCO2, so a patient with a saturation of 90 per cent can still need NIV or none at all.
- Trap: ignoring biomass smoke and tuberculosis Correct: biomass smoke is a major COPD risk factor among Indian women who cook over open fires, and tuberculosis mimics COPD when sputum persists or the chest X-ray is atypical.
Frequently asked questions
What is the target oxygen saturation in acute COPD exacerbation?
The target saturation is 88 to 92 per cent in patients at risk of hypercapnic respiratory failure, which includes most COPD exacerbations with known CO2 retention. Oxygen is titrated carefully because high-flow oxygen can worsen carbon dioxide retention.
Which COPD exacerbations need antibiotics according to Anthonisen?
Antibiotics are indicated in acute COPD exacerbation when sputum purulence is present with one other cardinal feature, and in any exacerbation needing mechanical ventilation. A type 1 exacerbation with all three features always qualifies for antibiotics.
What NIV threshold is used in COPD exacerbation?
Non-invasive ventilation is started for acute respiratory acidosis with pH below 7.35 and PaCO2 above 6.5 kPa that persists despite initial medical treatment. These thresholds identify patients most likely to benefit from NIV.
How long are steroids given in acute COPD exacerbation?
Oral prednisolone 30 to 40 mg daily is given for five days in an acute COPD exacerbation, and a prolonged taper is not required. Short courses shorten recovery time and reduce the risk of treatment failure.