Method of measuring instantaneous arterial blood pressure and compliance and device thereof
First Claim
1. A method for measuring the arterial instantaneous blood pressure and compliance, comprising:
- a searching step;
finding the critical depth λ
s when Ps= Pb and determining Ps and λ
s using an actuator to impose a pressure on the skin, a pressure sensor to measure a skin mean blood pressure Ps, and a displacement sensor to detect the depth λ
s under the pressure, then using the pressure sensor to measure the peak-to-peak pressure value, where the above-mentioned procedure is repeated until the maximum peak-to-peak value is reached, with the corresponding depth being the critical depth λ
s and the mean blood pressure measured at the skin being equal to the arterial mean blood pressure Pb;
wherein Ps is the mean blood pressure measured at the skin, Pb is the arterial mean blood pressure, and λ
s is the critical depth of the skin;
a controlling step;
using the pressure sensor to monitor the blood pressure change Δ
Ps transmitted from the artery to the skin when the arterial blood pressure changes by Δ
Pb at the critical depth λ
s, using the actuator to change the depressed depth of the skin for generating the corresponding displacement change Δ
λ
s so that the blood pressure change at the skin Δ
Ps approaches zero, in which case the muscle tissue compliance remain invariant, the tissue stiffness Kt being equal to the tissue impedance Zt and thus making the mean blood pressure at the skin Ps and the arterial mean blood pressure Pb remain equivalent, where the displacement change Δ
λ
s of the actuator detected by the displacement sensor is the variation in the arterial blood vessel diameter;
wherein Δ
Pb is the difference between the arterial blood pressure and the mean blood pressure, Δ
λ
s is the displacement change from the critical depth λ
s for the arterial mean blood pressure change of Δ
Pb;
an identifying step;
simulating the artery vessel as a second-order system with mass, damping, and stiffness and performing system identification to obtain blood vessel parameters Mv, Dv, and Kv as well as the artery impedance Zv;
an estimating step;
transmitting the detected signal to a controlling unit for computations, using the mean blood pressure at the skin Ps, the artery impedance Zv, and the arterial blood vessel diameter change Δ
λ
s to estimate the arterial instantaneous blood pressure {circumflex over (P)}b, and using the arterial instantaneous blood pressure {circumflex over (P)}b and the diameter displacement change Δ
λ
v to make a plot of the arterial dynamic compliance at the critical position.
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Abstract
A method of measuring the instantaneous arterial blood pressure and compliance and the device thereof are disclosed. The method identifies a critical depth under the skin. At this critical position, the arterial mean blood pressure is equivalent to the mean blood pressure obtained on the skin. The variation in the arterial mean blood pressure is tracked and controlled to maintain the equivalence between the mean blood pressure measured on the skin and the arterial mean blood pressure. In this case, the compliance of the muscle tissues remains invariant. Therefore, the variation measured on the skin is simply the behavior of the blood vessel. Using the skin-artery correlation, the invention can obtain the instantaneous blood pressure after some computation and the dynamic compliance at the critical position.
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Citations
8 Claims
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1. A method for measuring the arterial instantaneous blood pressure and compliance, comprising:
-
a searching step;
finding the critical depthλ s whenP s=P b and determiningP s andλ s using an actuator to impose a pressure on the skin, a pressure sensor to measure a skin mean blood pressureP s, and a displacement sensor to detect the depth λ
s under the pressure, then using the pressure sensor to measure the peak-to-peak pressure value, where the above-mentioned procedure is repeated until the maximum peak-to-peak value is reached, with the corresponding depth being the critical depthλ s and the mean blood pressure measured at the skin being equal to the arterial mean blood pressureP b;
whereinP s is the mean blood pressure measured at the skin,P b is the arterial mean blood pressure, andλ s is the critical depth of the skin;a controlling step;
using the pressure sensor to monitor the blood pressure change Δ
Ps transmitted from the artery to the skin when the arterial blood pressure changes by Δ
Pb at the critical depthλ s, using the actuator to change the depressed depth of the skin for generating the corresponding displacement change Δ
λ
s so that the blood pressure change at the skin Δ
Ps approaches zero, in which case the muscle tissue compliance remain invariant, the tissue stiffness Kt being equal to the tissue impedance Zt and thus making the mean blood pressure at the skinP s and the arterial mean blood pressureP b remain equivalent, where the displacement change Δ
λ
s of the actuator detected by the displacement sensor is the variation in the arterial blood vessel diameter;
wherein Δ
Pb is the difference between the arterial blood pressure and the mean blood pressure, Δ
λ
s is the displacement change from the critical depthλ s for the arterial mean blood pressure change of Δ
Pb;an identifying step;
simulating the artery vessel as a second-order system with mass, damping, and stiffness and performing system identification to obtain blood vessel parameters Mv, Dv, and Kv as well as the artery impedance Zv;an estimating step;
transmitting the detected signal to a controlling unit for computations, using the mean blood pressure at the skinP s, the artery impedance Zv, and the arterial blood vessel diameter change Δ
λ
s to estimate the arterial instantaneous blood pressure {circumflex over (P)}b, and using the arterial instantaneous blood pressure {circumflex over (P)}b and the diameter displacement change Δ
λ
v to make a plot of the arterial dynamic compliance at the critical position. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification