What does a difference in SpO2 greater than 5-10% between pre- and post-ductal measurements typically indicate in a neonate?

A difference in SpO2 greater than 5-10% between pre- and post-ductal measurements in a neonate typically indicates significant shunting at the ductal level. This measurement reflects how effectively blood is being oxygenated and the potential for mixing of oxygenated and deoxygenated blood. Such a difference suggests that blood is bypassing the lungs and not being adequately oxygenated, often due to an anatomical or physiological issue related to congenital heart defects or pulmonary circulation problems.

In healthy neonates, pre-ductal measurements (usually from the right hand) should be similar to post-ductal measurements (usually from a lower extremity). A marked difference often points to either a right-to-left shunt or a left-to-right shunt across the ductus arteriosus, which can lead to the baby not receiving the necessary oxygenation.

While airway obstruction can impact oxygenation levels, it typically does not produce such a specific difference in pre- and post-ductal readings. Cardiac anomalies could explain why shunting is occurring, but the key metric provided here specifically indicates the consequence of that shunting rather than the presence of the anomaly itself. Normal adaptation after birth would not lead to such discrepancies in oxygen saturation readings, as