Abstract
Vasomotion is the spontaneous time-dependent contraction and relaxation of micro arteries and the oscillating frequency is about 0.01–0.1 Hz. The physiological mechanism of vasomotion has not been thoroughly understood. From the dynamics point of view, the heartbeat is the only external loading exerted on the vascular system. We speculate that the nonlinear vascular system and the variable period of the heartbeat might induce the low-frequency vasomotion. In this study, the laser Doppler flowmeter is used to measure the time series of radial artery blood flow and reconstructed modified time series that has the same period as the measured time series but different heartbeat curves. We measured the time series of radial artery blood flow in different conditions by adding different noise disturbances on the forearm, and we decomposed the experiment pulse signal by Hilbert–Huang transform. The wavelet spectral analyses showed that the low-frequency components were induced by the variable period but independent of the shape of the heartbeat curve. Furthermore, we simulated the linear flow in a single pipe and the nonlinear flow in a piping network and found that the nonlinear flow would generate low-frequency components. From the results, we could deduce that the variable period of heartbeat and the nonlinearity of the vascular system induce vasomotion. The noise has effects on the blood signals related to the respiratory activities (∼0.3 Hz) but little influence on that related to the cardiac activities (∼1 Hz). Adding white noise and then stopping would induce an SNR increase in the frequency band related to vasomotion (∼0.1 Hz).
Highlights
Vasomotion is the spontaneous change in micro arteries diameters, which was first observed in the bat wing (Jones, 1852; Gustafsson et al, 1993; Rossi et al, 2006)
The oscillations in the region around ~1 Hz are related to the cardiac activity, the oscillations in the region around ~0.3 Hz are related to the respiratory activity, and the oscillations ranging from 0.001 to 0.2 Hz are related to endothelial and myogenic activities (Stefanovska et al, 1999; Söderström et al, 2003)
The spectral analyses of the results lead to the following conclusions: 1) Based on the Laser-Doppler flow (LDF) measured radial artery blood flow signals at the wrist, two groups of data, reconstructed and average data, were acquired by constructing a sinusoidal flow velocity model using important features from the experimental data
Summary
Vasomotion is the spontaneous change in micro arteries diameters, which was first observed in the bat wing (Jones, 1852; Gustafsson et al, 1993; Rossi et al, 2006). Microcirculation may reflect the conditions of other systemic vascular functions and the microvascular abnormalities may originate the pathogenesis sequence in some diseases (Holowatz et al, 2008), and the link between vasomotion and cardiovascular diseases is acknowledged in many research studies (Fonseca et al, 2018; Smith, 2020). Many studies (MückWeymann et al, 1996; Bracic and Stefanovska, 1998; Stefanovska et al, 1999; Söderström et al, 2003; Cracowski et al, 2006) analyzed characteristic frequencies of blood flow oscillation signals, and these frequencies components correspond to several types of activities. The oscillations in the region around ~1 Hz are related to the cardiac activity, the oscillations in the region around ~0.3 Hz are related to the respiratory activity, and the oscillations ranging from 0.001 to 0.2 Hz are related to endothelial and myogenic activities (Stefanovska et al, 1999; Söderström et al, 2003). Vasomotion is the oscillations related to endothelial and myogenic activities whose frequency interval is from 0.001
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