Oesophageal Doppler Descending Aorta — FRCA Primary MCQ

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HardPhysics & Clinical MeasurementOesophageal Doppler Descending AortaFRCA Primary

An oesophageal Doppler calculates descending-aortic flow using measured mean velocity. Which additional measurement enters directly into the flow calculation?

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Correct answer: B — The aortic cross-sectional area

The best answer is “The aortic cross-sectional area”. Volumetric flow is mean velocity multiplied by vessel cross-sectional area. Oesophageal Doppler therefore depends on velocity measurement plus an estimate or measurement of aortic diameter and area, with further assumptions when extrapolating descending-aortic flow to total cardiac output. Damping, filling pressure and systemic resistance are not direct terms in that equation.

Reference: Singer et al., New techniques for cardiac output measurement: oesophageal Doppler: https://pmc.ncbi.nlm.nih.gov/articles/PMC137448/