Acute Exacerbation of COPD
A 66-year-old man with severe COPD has 2 days of worsening breathlessness. Despite an hour of controlled oxygen, bronchodilators, hydrocortisone and doxycycline, he remains distressed with a respiratory rate of 30 breaths/min and is drowsy with a flapping tremor. Arterial blood gas on 28% oxygen shows pH 7.26, PaCO2 8.6 kPa, PaO2 7.9 kPa and bicarbonate 30 mmol/L. What is the most appropriate next step in management?
- A.Intravenous aminophylline infusion
- B.Non-invasive bilevel positive airway pressure ventilationCorrect
- C.Increase inspired oxygen to 100% by reservoir mask
- D.Intravenous furosemide bolus and fluid restriction
Explanation
Non-invasive ventilation is indicated in an exacerbation of COPD when persistent respiratory acidosis remains despite optimal medical therapy, conventionally a pH below 7.35 with a PaCO2 above 6.0 to 6.5 kPa, and it is strongly indicated below a pH of 7.30 as here. Bilevel support unloads the fatigued respiratory muscles, augments alveolar ventilation to clear carbon dioxide, and counterbalances intrinsic PEEP, and it reduces intubation rates, mortality and length of stay more than any other single intervention in this setting. The standard package of care that must precede it comprises controlled oxygen targeting a saturation of 88 to 92%, short-acting beta-2 agonist plus short-acting antimuscarinic nebulizers, systemic corticosteroid (prednisolone 30 to 40 mg for 5 days), and antibiotics when sputum is purulent or ventilatory support is required. Aminophylline is a second-line agent with a narrow therapeutic index that causes arrhythmias, vomiting and seizures with little benefit, and it does not correct acute respiratory acidosis. Raising the inspired oxygen to 100% is actively harmful: it abolishes hypoxic vasoconstriction, worsening ventilation-perfusion matching, causes the Haldane effect and reduces respiratory drive, all of which raise the PaCO2 further and deepen the acidosis. Furosemide treats pulmonary oedema from left heart failure, which is excluded by the clear chest radiograph and the hyperinflated lungs. If non-invasive ventilation fails or consciousness deteriorates further, intubation and invasive ventilation should be considered according to the patient's wishes and premorbid function.
Why each option
- A.
- Aminophylline is second line, has a narrow therapeutic index, and does not reliably reverse hypercapnic acidosis.
- B.
- Correct. Persistent respiratory acidosis with pH 7.26 and PaCO2 8.6 kPa despite optimal therapy is the classic indication for non-invasive ventilation.
- C.
- High-flow uncontrolled oxygen worsens hypercapnia through ventilation-perfusion mismatch and the Haldane effect; target saturation is 88 to 92%.
- D.
- There is no evidence of fluid overload; the radiograph shows hyperinflation without pulmonary oedema.
Reference: GOLD Report, 2024; NICE COPD Guideline NG115
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