Descending Aortic Flow: 

This measure is only currently recommended for use as a research tool as it has poor reproducibility! Measure the descending aortic diameter (or area) from an axial view at the level of the diaphragm.

Use high resolution zoom to optimise the DAo view:

Measure the descending aortic flow velocity from the ductal view, but with the transducer directed caudally to visualise the vessel anterior and to the left of the spine.

Due to angle of insonation angle correction must be used to avoid significantly underestimating volume of flow. This view is the same as used when looking for diastolic descending aortic flow reversal as part of an assessment of haemodynamic significance of the ductus arteriosus.