Fig. 1. Example of original data [PDA(t), dorsal aortic pressure; QDA(t), dorsal aortic flow] obtained from a HH21 CON embryo (A). Data were recorded simultaneously in the dorsal aorta at the level of the sinus venosus. Waveforms were decomposed using Fourier transform to characterize the modulus (B) and phase (C) of arterial impedance.