Fig. 6

Pulse transit time detection in magnified recordings in animals with low and high blood pressure. a Single frame from color-magnified video of an anesthetized axolotl (Additional file 8). The dorsal aorta (DA) is indicated. b Proximal and distal DA and background signal (black, red and gray rings in a) development over time (combined channel signals). c Cross-correlation plot of proximal and distal DA signal. Notice the phase delay in the proximal and distal DA signal .d Micro-CT (μCT) generated model of the heart [sinus venosus (SV), atria (A), ventricle (V), and outflow tract (OFT)] and major arterial networks in the axolotl confirming the course of the DA as drawn in a. e Four-frame time series showing color changes along the left arteria carotis communis over time in a color-magnified video of a resting human being (Additional file 9, first part). f Vertical scan line over time showing temporal variation at the intersection with the a. carotis communis. g Lower and upper throat and background signal (black, red, and gray rings in e) development over time (combined channel signals). h Cross-correlation plot of lower and upper throat signal. Notice the phase delay between the lower throat and upper throat signal. i Fourier-transformed combined channel signal for lower throat in g in the frequency domain. j Four-frame time series showing color changes along the right arteria brachialis over time in a color-magnified video of a resting human being (Additional file 9, second part). k Vertical scan line over time showing temporal variation at the intersection with the a. brachialis. l Armpit and elbow and background signal (black, red, and gray rings in j) development over time (combined channel signals). m Cross-correlation plot of armpit and elbow signal. Notice the phase delay between the lower armpit and elbow signal. n Fourier-transformed combined channel signal for armpit in i in the frequency domain