Figure 3

The illustration of iPR series and corresponding fast Fourier transform (FFT) spectrum within 1 minute in one subject for example. The physiologic challenges of iPR include (a) baseline, (b) breathing with 6 cycles per minute, (c) breathing with 30 cycles per minute, (d) head-up tilt (HUT) and corresponding FFT spectrum during (e) baseline, (f) breathing with 6 cycles per minute, (g) breathing with 30 cycles per minute, (h) HUT.