A patient on ECMO support shows worsening oxygenation despite stable ventilator and ECMO settings. What should be checked first?

Correct option is B

In ECMO, sudden worsening of oxygenation despite stable parameters suggests clot formation or obstruction in circuit/oxygenator. This is a critical complication needing immediate check.
Explanation of options: (a) ✘ Glucose has no role in oxygenation failure. (b) ✔ Correct; clot/obstruction in ECMO circuit directly reduces oxygen delivery. (c) ✘ Position changes do not alter ECMO oxygenation significantly. (d) ✘ Vasopressors affect BP, not oxygen transfer in ECMO.