When the ductus arteriosus stays open oxygen-rich (red) blood passes from the aorta to the pulmonary artery mixing with the oxygen-poor (blue) blood already flowing to the lungs.

• 如动脉导管持续开放，主动脉来的富氧血（通过动脉导管）进入肺动脉，与已经流入肺的乏氧血混合。