Right-to-left ductal shunt and transcutaneous PO2.

The continuous monitoring of the PO2 with double sensors, pre- and post-ductal, is very interesting during the neonatal period; the magnitude of the right-to-left ductal shunting, related to high pulmonary vascular resistance, is well evaluated by the hyperoxemia test. This noninvasive method allows a reliable observation of the pulmonary vascular response to oxygen, alkaline solutions, or tolazoline infusion.