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Acute hypercapnic respiratory failure due to COPD exacerbation requiring non-invasive ventilation — SCE Respir

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HardCOPD ExacerbationAcute hypercapnic respiratory failure due to COPD exacerbation requiring non-invasive ventilationSCE Respiratory

A 71-year-old man with severe COPD is admitted with an infective exacerbation and acute hypercapnic respiratory failure. After controlled oxygen and initial bronchodilator treatment, arterial blood gases show pH 7.22, PaCO2 10.1 kPa and PaO2 7.4 kPa. Non-invasive ventilation (NIV) is started. One hour later he is alert, haemodynamically stable and coordinating with NIV; repeat gases show pH 7.29 and PaCO2 8.8 kPa. Oxygen enrichment maintains SpO2 at 90%. A planned break from NIV is attempted to administer further nebulised salbutamol and ipratropium. Within 60 seconds he becomes severely distressed, his respiratory rate rises to 38 breaths/min and SpO2 falls to 82%; these abnormalities resolve promptly when NIV is reapplied. An in-line nebuliser is available. Which is the most appropriate method of delivering the bronchodilator now?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: C — Continue NIV and administer the bronchodilator through an in-line nebuliser, maintaining SpO2 at 88–92%

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

The improving pH and PaCO2 indicate an effective NIV response, so there is no reason to abandon treatment. However, the immediate distress, tachypnoea and desaturation during a brief interruption demonstrate current NIV dependence. Although nebulised bronchodilators should normally be administered during NIV breaks, BTS/ICS guidance specifies that an in-line nebuliser should be used when interruption causes distress. Oxygen enrichment should remain titrated to 88–92% during acute hypercapnic respiratory failure. B would ordinarily be preferred for a hypercapnic patient who can tolerate a treatment break: compressed air avoids the additional uncontrolled oxygen exposure produced by an oxygen-driven nebuliser. It is inappropriate here because the attempted break causes rapid physiological deterioration. C risks worsening hypercapnia and acidosis through high-concentration oxygen delivery and unnecessarily removes effective ventilatory support. D uses the correct delivery route but the wrong oxygen target; 94–98% constitutes excessive oxygenation in this setting. E withholds part of optimal medical therapy without justification. Bronchodilation should continue while ventilatory support reverses the acidosis; normalisation of pH is not a prerequisite. The key sequence is therefore to recognise an improving NIV response, identify NIV dependence during the attempted break, deliver the drug through the circuit, and preserve controlled oxygenation.

Reference: BTS/ICS guideline for the ventilatory management of acute hypercapnic respiratory failure in adults (2016; correction published June 2017) — https://thorax.bmj.com/content/71/Suppl_2/ii1 BTS guideline for oxygen use in adults in healthcare and emergency settings (2017; BTS position reviewed December 2019) — https://www.brit-thoracic.org.uk/document-library/guidelines/emergency-oxygen/bts-guideline-for-oxygen-use-in-adults-in-healthcare-and-emergency-settings/ Chronic obstructive pulmonary disease in over 16s: diagnosis and management (2018; updated 2019) — https://www.nice.org.uk/guidance/ng115/chapter/Recommendations