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Long-Term Oxygen Therapy — SCE Respiratory MCQ

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HardLong-Term Oxygen TherapySCE Respiratory

A 72-year-old man with severe COPD is assessed for long-term oxygen therapy. He stopped smoking 3 years ago, has a BMI of 23 kg/m² and has no symptoms suggesting obstructive sleep apnoea. His inhaled treatment is optimised, and he has been clinically stable for 10 weeks. Two room-air arterial blood gases obtained 3 weeks apart show PaO₂ values of 6.9 and 7.0 kPa, PaCO₂ values of 6.8 and 6.9 kPa, and pH values of 7.39 and 7.38, respectively. At his first formal oxygen titration, oxygen at 2 L/min raises SpO₂ to 92% and PaO₂ to 8.3 kPa. The corresponding PaCO₂ is 8.0 kPa and pH is 7.36. He remains alert and clinically well. Which management plan is most appropriate?

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

Reveal the answer and explanation

Correct answer: C — Defer LTOT, undertake further medical optimisation and repeat oxygen titration with blood gases after 4 weeks

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

His repeated stable room-air PaO₂ measurements confirm severe chronic hypoxaemia and therefore establish a potential indication for LTOT. Baseline hypercapnia does not itself exclude LTOT, but it requires serial assessment of PaCO₂ and pH during oxygen titration. Although 2 L/min achieves the oxygenation target, PaCO₂ rises from 6.8–6.9 kPa to 8.0 kPa: an increase exceeding 1 kPa. BTS guidance advises that respiratory acidosis and/or a PaCO₂ rise greater than 1 kPa during an LTOT assessment may indicate clinical instability; medical treatment should be further optimised and assessment repeated after 4 weeks. Therefore E is correct. A is inappropriate because an empirically lower flow may not achieve PaO₂ of at least 8 kPa and does not remove the need to document its effect on PaCO₂ and pH. B exposes him to potentially significant oxygen-induced worsening of hypercapnia and delays reassessment excessively. C is premature: domiciliary oxygen should be combined with nocturnal ventilatory support when this response occurs on two repeated assessments despite apparent clinical stability, not after its first occurrence. D is incorrect because stable hypercapnic patients can receive LTOT when carefully titrated and monitored; hypercapnia is a reason for enhanced assessment rather than an absolute contraindication.

Reference: BTS Guidelines for Home Oxygen Use in Adults (June 2015) — https://www.brit-thoracic.org.uk/document-library/guidelines/home-oxygen-for-adults/bts-guidelines-for-home-oxygen-use-in-adults/ Chronic obstructive pulmonary disease in over 16s: diagnosis and management (2018, updated 2019) — https://www.nice.org.uk/guidance/ng115/chapter/Recommendations