Fig. 1
From: Variable open-end wave reflection in the pulmonary arteries of anesthetized sheep
A pressure–velocity (PU) loop for a single resting cardiac cycle without adjustments of the velocity signal delay. Velocity is lagging pressure by 20 ms, and in early systole (arrow), the loop is concave to the pressure axis. It is possible to see that wave speed calculated from dP/dU × 1/ρ in early systole would lead to an artificially high value and subsequently further errors in wave separation