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Post-pneumonectomy physiology — SCE Respiratory MCQ

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HardRespiratory PhysiologyPost-pneumonectomy physiologySCE Respiratory

During a stable COPD review, an arterialised earlobe sample gives a plausible pH and PCO2 but a PO2 close to the long-term-oxygen threshold. How should the sample be interpreted?

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Correct answer: B — Use pH and PCO2; confirm PO2 with an arterial sample

Arterialised earlobe pH and PCO2 usually agree closely with arterial values and are useful for stable monitoring. Earlobe PO2 tends to underestimate arterial PO2 and agreement is insufficient when a precise oxygenation decision is required, including a borderline LTOT assessment. In that setting, pulse oximetry and an arterial sample should resolve the decision.

Reference: ARTP statement on pulmonary function testing (Published 2020): https://bmjopenrespres.bmj.com/content/7/1/e000575; BTS guideline for oxygen use and arterialised capillary blood-gas interpretation (Published 2017): https://thorax.bmj.com/content/72/Suppl_1/ii1