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Persistent hypercapnic respiratory failure following an acute exacerbation of COPD — SCE Respiratory MCQ

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HardHypercapniaPersistent hypercapnic respiratory failure following an acute exacerbation of COPDSCE Respiratory

A 68-year-old man with severe COPD is reviewed in a specialist ventilation clinic 3 weeks after discharge. Before admission, he was receiving optimised inhaled therapy and long-term oxygen therapy (LTOT) for severe resting hypoxaemia. During the admission, an infective exacerbation caused acute hypercapnic respiratory failure (pH 7.21, PaCO₂ 11.0 kPa), which responded to acute non-invasive ventilation (NIV). He was weaned from NIV once the acidaemia resolved. He is now clinically back to baseline. Room-air arterial blood gases at 2 and 3 weeks after resolution of the acidaemia show pH 7.38, PaCO₂ 7.5 kPa, bicarbonate 34 mmol/L and PaO₂ 7.0 kPa. His BMI is 27 kg/m², limited respiratory polygraphy shows an apnoea–hypopnoea index of 4/hour, and there is no neuromuscular or chest-wall disorder. Which long-term respiratory support strategy is most likely to improve admission-free survival?

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Correct answer: B — Continue LTOT and initiate nocturnal fixed-pressure-support NIV titrated to substantially reduce PaCO₂

Explanation lettering: E = shown as A · A = shown as B · B = shown as D · D = shown as E

This patient has persistent, compensated hypercapnia in the clinically stable recovery phase after a life-threatening COPD exacerbation requiring acute NIV. The elevated bicarbonate and normal pH indicate chronic ventilatory failure rather than ongoing acute acidaemia. Persistence on repeated measurements 2–3 weeks after resolution is important because hypercapnia measured during or immediately after an exacerbation may resolve spontaneously. Obesity hypoventilation, obstructive sleep apnoea and extrapulmonary ventilatory disorders have also been excluded. The UK HOT-HMV trial enrolled a closely matched population with PaCO₂ above 53 mmHg (approximately 7.1 kPa) 2–4 weeks after resolution of respiratory acidaemia. Adding home NIV to oxygen prolonged median time to readmission or death compared with oxygen alone. NIV should use pressure support sufficient to meaningfully reduce PaCO₂ rather than low-intensity symptomatic settings. B fails because resolved acidaemia does not negate persistent chronic hypercapnic respiratory failure. C addresses hypoventilation but inappropriately withdraws oxygen despite an established LTOT indication and persistent severe hypoxaemia. D would be appropriate for clinically important obstructive sleep apnoea, which the polygraphy excludes; CPAP does not provide adequate ventilatory assistance for this phenotype. E reflects appropriate caution about transient post-exacerbation hypercapnia, but the recommended 2–4-week reassessment window has already been reached with reproducible hypercapnia.

Reference: Chronic obstructive pulmonary disease in over 16s: diagnosis and management — Recommendations (Published 5 December 2018; updated 26 July 2019) — https://www.nice.org.uk/guidance/ng115/chapter/Recommendations Effect of Home Noninvasive Ventilation With Oxygen Therapy vs Oxygen Therapy Alone on Hospital Readmission or Death After an Acute COPD Exacerbation (6 June 2017) — https://pubmed.ncbi.nlm.nih.gov/28528348/ European Respiratory Society guidelines on long-term home non-invasive ventilation for management of COPD (2019) — https://publications.ersnet.org/content/erj/54/3/1901003