COPD acute hypercapnic respiratory failure — FFICM MCQ

Correct answer: A — Start NIV and titrate oxygen to 88 to 92%

The correct answer is A, start NIV and titrate oxygen to 88 to 92%. This patient has acute-on-chronic type 2 respiratory failure with a raised bicarbonate reflecting chronic CO2 retention, but pH 7.24 with PaCO2 9.2 kPa shows decompensated respiratory acidosis persisting despite high-flow oxygen. BTS/ICS guidance recommends NIV when pH stays below 7.35 with PaCO2 above 6.5 kPa despite optimal medical therapy, and there is no contraindication here (no pneumothorax, alert though exhausted). Oxygen must be titrated to 88 to 92% because over-oxygenation abolishes hypoxic pulmonary vasoconstriction, worsens V/Q mismatch and reduces ventilatory drive, further raising CO2. NIV unloads the respiratory muscles and improves alveolar ventilation, correcting acidosis while avoiding intubation in a conscious, cooperative patient. Why the other options are wrong: A, Continue high-flow oxygen and repeat ABG in 4 hours: high-flow oxygen worsens hypercapnia in COPD, and 4 hours is far too long to leave a decompensated acidotic patient without ventilatory support. B, Intubate immediately for controlled hyperventilation: invasive ventilation is reserved for NIV failure, severe or worsening acidosis, reduced consciousness or copious secretions; this alert patient warrants a trial of NIV first. C, Start CPAP with FiO2 1.0: CPAP gives no pressure support for ventilation, does not correct hypercapnia, and FiO2 1.0 risks worsening CO2 retention; bilevel NIV, not CPAP, is required. E, Give intravenous sodium bicarbonate: this does not treat the ventilatory failure, can worsen intracellular acidosis, and may paradoxically increase CO2; it has no role here. Key point: In acute hypercapnic COPD exacerbation with persistent acidosis (pH under 7.35, PaCO2 over 6.5 kPa) despite medical therapy, start NIV with oxygen titrated to 88 to 92%, reserving intubation for NIV failure or contraindications.

Reference: British Thoracic Society/Intensive Care Society Guideline for the Ventilatory Management of Acute Hypercapnic Respiratory Failure in Adults, 2016: recommends targeting SpO2 88-92% in AECOPD and starting NIV when pH <7.35 with PaCO2 >6.5 kPa persists despite optimal medical therapy. https://pmc.ncbi.nlm.nih.gov/articles/PMC4800170/