Estimation of coherence between the pulsatile aortic blood pressure and the renal cortical flux in dogs

From the resonance phenomena, we suggest that the blood pressure wave in the kidney is synchronized and the pressure wave front arrives at all the peripheral vascular beds (PVBs) inphase. The phase velocity of the blood pressure wave is very fast and its corresponding wavelength is far longer than the size of PVB of the kidney. Therefore, all the blood flows in PVB driven by the blood pressure wave will be kept inphase all around the kidney. To verify our inference, we used Laser-Doppler flowmetry (LDF) to measure the renal cortical fluxes (RCF) at different sites on the kidney surface of dog and compare their frequency structures and phase differences with those of the abdominal aortic blood pressure (AABP). Using the averaged spectrum and the cross-covariance function, we conclude that the frequency structure of RCF is directly correlated with that of AABP and the RCF to AABP phase differences of all the five dogs are in a tiny range. The results strongly suggest that the pulsatile blood pressure wave is pushing the blood in PVBs and integrates all PVBs of the kidney as a unity as suggested by Huygens' principle.