Final answer:
Dual stage venous cannulae have thin walls, small lumens, high pressure, and valves that facilitate efficient blood flow.
Step-by-step explanation:
Dual stage venous cannulae have thin walls, small lumens, high pressure, and valves. They are designed to facilitate the flow of deoxygenated blood from the veins to the heart. The small lumens and high pressure allow for efficient blood flow, while the valves ensure that blood can flow in only one direction.