Analysis of blood flow energy characteristics of pulsatile and non-pulsatile flow during extracorporeal circulation

Abstract

Objective: To analyze the magnitude of blood flow energy and characteristics of frequency domain between pulsatile flow and nonpulsatile flow during cardiopulmonary bypass and physiological flow. Methods: From January 2017 to December 2017, 60 cases of patients with mitral valve disease scheduled for mitral valve replacement or repair at Department of Cardiasurgery, Shanghai Chest Hospital, Shanghai Jiaotong University were randomly divided into 2 groups: pulsatile perfusion (PP) and non-pulsatile perfusion (NP). The magnitude of blood flow energy during pulsatile and non-pulsatile was calculated using energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE) while fast Fourier transformation (FFT) was used to perform power spectral density analysis to identify the frequency domain characteristics between artificial and physiological flow (prior to CPB). The data was analyzed by analysis of variance or t test. Results: At the different time-points after occlusion, the EEP and SHE in PP group were respectively 1.52 to 1.62 and 2.03 to 2.22 times higher than NP at the distal of artery filter. The power density analysis revealed that the blood flow energy of physiological pulsatile flow patterns was within 40 Hz and the ratio of low frequency energy was more than 90% before clamp. The spectral energy ratio of low frequency decreased in both group compared with physiological flow was more obvious in NP group at the radial artery. The ratio of estimated value of power density of PP and NP groups analysis showed the corresponding 0 to 5 Hz, 0 to 10 Hz, 0 to 40 Hz frequency range values measured at the radial artery and filter were 9.51, 4.68, 3.59 and 3.87, 2.69, 2.38 respectively after occulusion. In each frequency range, the energy of PP is higher than that of NP, and the lower the frequency, the greater the difference. The ratio of estimated value of power density of PP and NP groups for the three frequencies measured at the radial artery before and after occlusion were 2.86, 2.83, 2.75 and 14.70, 12.74, 9.85 respectively, and decreased significantly in NP group and low frequency energy. The ratio of estimated value of power density of PP and NP groups under the three different frequencies measured at the radial artery and filter were 26.35, 33.15, 37.36 and 37.41, 54.18, 56.64 respectively, in the conduction process from filter to radial artery, energy exhaustion is significant, especially in group NP. Conclusions: The PP provides significantly more energy than the NP whereby the PP is closer to the physiological pulsatile on the energy frequency structure and attenuation characteristics, with mainly low frequency energy of 0 to 5 Hz and weak energy attenuation. The energy loss of non-pulsatile flow is obvious, especially the low frequency energy.