Non-invasive method and device of measuring the real-time continuous pressure of fluid in elastic tube and the dynamic compliance of elastic tube

摘要

The invention presents a non-invasive method and device of measuring the real-time continuous pressure of fluid fluctuating in an elastic tube and the dynamic compliance of the elastic tube, in which the theory of VLDT (Vascular Loading Decoupling Technique) is used. After searching the initial critical depth and determining the decoupled ratio, a DC controller generates a DC control gain to maintain the elastic tube at critical depth, and an AC controller employs the self-adaptive and Step-Hold control rules to create the pulsation of elastic tube without effect of surrounding tissues, and be capable of measuring the real-time continuous fluid pressure and dynamic compliance of elastic tube.

主权项

1. A non-invasive method of measuring a real-time continuous pressure of fluid in an elastic tube and a dynamic compliance of the elastic tube, wherein elastic surrounding tissues are wrapped outside the elastic tube, and wherein a fluctuating fluid flows in the elastic tube, the fluid having a fluid pressure which can be divided into a DC part Pb and an AC part ΔPb, the method comprising:
using an oscillometric method, pressing a detection head by a DC-driven actuator on the surface of the surrounding tissues to locate an initial critical depth λs; holding at the initial critical depth to determine a decoupled ratio K for partial or full tracking of the AC part of fluid pressure ΔPb; actuating a DC-driven actuator to maintain a DC part of a sensor's pressure Ps as equal to the DC part of the fluid pressure Pb, and setting a resulting new depth as the location of an updated critical depth λs′; setting an AC-driven actuator, separate from the DC-driven actuator, in an idling (hold) stage to obtain three previous reference pressures Δ{circumflex over (P)}b′(n−3), Δ{circumflex over (P)}b′(n−2), and Δ{circumflex over (P)}b′(n−1), and estimating a reference pressure Δ{circumflex over (P)}b′(n) for an actuated (step) stage; using a constant AC open loop gain Ka and a self-adaptive control rule to estimate a parallel impedance H1 and compute an impedance of the elastic tube Zv2(n); using the constant AC open loop gain Ka and the parallel impedance H1 to calculate an AC control gain Ga for a next step stage; sending an AC control gain Ka from AC controller, and moving the AC-driven actuator to track the AC part of the fluid pressure ΔPb and obtain the AC part of a displacement Δλs′(n); computing the AC part of the fluid pressure ΔPb′(n) according to the impedance of the elastic tube Zv2(n) and the AC part of the displacement Δλs′(n); adding the DC part of the fluid pressure Pb′(n), which is equal to the DC part of the sensor's pressure Ps, to the AC part of the fluid pressure ΔPb′(n), to compute the real-time continuous fluid pressure Pb(n); extracting a series of equivalent mechanical properties including mass Mv(n), damping Dv(n), and stiffness Kv(n) from the dynamic impedance of elastic tube Zv2(n) by using a parameter identification technique, and computing the dynamic compliance of elastic tube Cv(n) using the reciprocal of the stiffness Kv(n).