A difference of 15 PaO2 between right radial artery and umbilical artery ABG results indicates what condition?

A difference of 15 mmHg in PaO2 between the right radial artery and the umbilical artery indicates a significant physiological issue, often involving right-to-left shunting of blood. In a scenario with patent ductus arteriosus (PDA), there is an abnormal connection between the aorta and pulmonary artery that can allow deoxygenated blood to bypass the lungs and enter systemic circulation. This results in a lower oxygen saturation in the blood coming from the umbilical artery when compared to the radial artery, as the blood is not adequately oxygenated.

When there is a right-to-left shunt, the expected oxygen levels are compromised, leading to a clinically significant variation in arterial oxygen levels, as measured by blood gas analysis. Therefore, the observed difference in PaO2 levels supports a diagnosis of PDA with right-to-left shunting, indicating a disturbance in normal circulatory and respiratory function that can lead to oxygen deprivation in systemic circulation.