CN101176663A - Non-invasive cardiac output detecting methods and apparatus based on sphygmus wave - Google Patents

Abstract

The invention provides a non-invasive cardiac output detection method and apparatus based on a pulse wave; wherein, the detection method comprises the following steps: firstly, amplifying and filtering the pressure pulse signals, and detaching the alternating current and direct current by means of amplifying and filtering; secondly, modulus conversion for the alternating current and direct current, and resampling the digital signals converted; fixing heart rate via the feature points on the waveform of the pulse; and fixing the external pressurizing force via calibrating the separated direct current; thirdly, using mathematical analyzing method to estimate time constant Tau for the separated alternating current; fourthly, calibrating the pulse wave to get mean arterial pressure MAP; fifthly, according to the MAP and Tau, calculating the cardiac output. The detecting apparatus comprises a pulse wave detection device, a detection circuit, a cardiac output estimation device and a display unit. The invention has the advantages of obtaining the cardiac output via a mathematical analyzing of the pulse wave on the non-invasive detection and realizing the non-invasive cardiac output detection.

Description

Non-invasive cardiac output detecting methods and device based on pulse wave

Technical field

The present invention relates to obtain detection method and the device thereof of cardiac output CO and heart rate HR, belong to the human parameters detection technique field of biomedical engineering by the pulse wave that detects life entity.

Background technology

The cardiac output detecting methods that meets clinical needs should have the characteristics of noinvasive, high accuracy, low expense.But regrettably traditional cardiac output detecting methods does not have a kind ofly can satisfy the above characteristic.For example, be used for intensive care unit and operating thermodilution method, although relatively cheap, can not continued operation.Owing to need pulmonary artery catheter to insert, thus its safety be under suspicion, and since this method based on a lot of hypothesis, so be not very accurate.Cardiac output detecting methods is by supersonic blood probe placement real-time measure blood flow on large artery trunks being obtained, need being opened the defective that breast is measured but exist more accurately.

Proper cardiac output detects to be proved to be and exists at need impassablely, estimates that by analyzing the arteriotony waveform kinemic thinking provides an effective solution route for this reason.1976, bourgeois people such as (Bourgeois) proposed to utilize analysis relaxing period arteriotony waveform to estimate kinemic technology according to windkessel model (Windkessel model), and this technology can only be applied on the central large artery trunks.But central aortic pressure is seldom measured clinically, and the waveform of relaxing period is disturbed by the complex wave reflection on the peripheral arterial that detects relatively easily, has influenced result's accuracy.2006, the wood Karma draws people such as (Mukkamala) to propose to eliminate the interference of complicated wave reflection to the relaxing period waveform by the arteriotony waveform of analyzing a plurality of cardiac cycles, and then the technology that bourgeois people such as (Bourgeois) proposes is generalized on the peripheral arterial that detects relatively easily.

Although peripheral arterial blood pressure phase of wave is to easy detection, but have the problem of wound.Meanwhile, the noinvasive detection technique of arterial pulse wave comparative maturity.By the definition of pulse wave as can be known, exist close contact between pulse wave and the blood pressure ripple, this contact can be found out on both waveform similarity degree intuitively.So estimate that by analyzing the detected pulse waveform of non-invasive methods cardiac output is feasible.This provides new thinking for kinemic noinvasive detects.

Summary of the invention

The present invention is directed to the defective that existing cardiac output detecting methods exists, provide a kind of and obtain kinemic non-invasive cardiac output detecting methods based on pulse wave by the pulse waveform that is easy to detect being carried out mathematical analysis.A kind of non-invasive cardiac output checkout gear based on pulse wave is provided simultaneously.

Non-invasive cardiac output detecting methods based on pulse wave of the present invention may further comprise the steps:

(1) utilize pulse wave detection device to obtain the pressure pulse signal, the pressure pulse signal is amplified and filtering, and separate through of ac and DC quantity after the amplification filtering, wherein, of ac is represented filtered pulse signal, and DC quantity is represented and the outside relevant numerical value of exerting pressure;

(2) of ac and DC quantity are carried out analog digital conversion, the digital signal after the conversion is resampled; Utilize the characteristic point (for example ascending branch starting point, peak point or incisura etc.) on the pulse waveform to determine heart rate HR; By isolated DC quantity being demarcated to determine the size of exerting pressure in the outside, determine that with auxiliary detection person the best exerts pressure;

(3) utilize Mathematical Method to estimate timeconstant to isolated of ac;

(4) pulse wave is demarcated, obtained mean arterial pressure MAP

(5) calculate cardiac output CO according to MAP and τ.

The detailed process of above-mentioned steps is:

(1) utilize pulse wave detection device to obtain the pressure pulse signal;

(2) the pressure pulse signal is amplified and filtering;

(3) separate through of ac and DC quantity after the amplification filtering, wherein, of ac is represented filtered pulse signal y (t), and DC quantity is represented and the outside relevant numerical value of exerting pressure;

(4) of ac and DC quantity are carried out analog digital conversion, the digital signal after the conversion are resampled, obtain pulse waveform sequences y (k) with the outside relevant numerical value of exerting pressure;

(5) utilize the characteristic point (for example ascending branch starting point, peak point or incisura etc.) on the pulse waveform to determine heart rate HR;

(6) by isolated DC quantity being demarcated to determine the size of exerting pressure in the outside, determine to be applied to the optimum pressure of test point with auxiliary detection person;

(7) according to pulse waveform sequences y (k), by a pulse train structure heart contraction signal x (k); Each pulse in the pulse train is positioned at corresponding pulse wave upstroke starting point place, and the height of pulse equals its corresponding pulse wave amplitude PA, and the peak value that PA is defined as pulse wave deducts the value at its upstroke starting point place;

(8) estimate an impulse response sequences h (k) according to x (k) and y (k), represent the pure exponential damping process of relaxing period pulse wave, the convolution that h (k) satisfies itself and x (k) is the best fit of y (k) on least squares sense, can be calculated as follows:

$h\left(k\right)=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{\hat{a}}_{i}h(k-i)+\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{\hat{b}}_j\mathrm{\δ}(k-j)$

Wherein, δ (k) is the unit pulse sequence,

Be to auto-regressive equation $y\left(k\right)=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{a}_{i}y(k-i)+\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{b}_{j}x(k-j)+e\left(k\right)$ Unknown parameter { a _i, b _jEstimation, the number of m and n limiting parameter (being model order), e (k) is immeasurablel residual error;

(9) according to the pure exponential damping section among the h (k), estimate the timeconstant (being the time constant in the windkessel model) of decay, it is worth based on following exponential form:

$h\left(k\right)={\mathrm{Ae}}^{-\frac{k}{\mathrm{\τ}}}+\mathrm{\ω}\left(k\right)$

Wherein, ω (k) is immeasurablel residual error, and A is a unknown parameter;

(10) according to pulse and blood pressure corresponding relation numerically, pulse values is demarcated, obtain mean arterial pressure MAP;

(11) according to windkessel model (Windkessel model), obtain:

$\mathrm{CO}\∝\frac{\mathrm{MAP}}{\mathrm{TPR}\·\mathrm{AC}}=\frac{\mathrm{MAP}}{\mathrm{\τ}}$

Wherein, MAP is a mean arterial pressure, and TPR is the peripheral blood vessel drag overall, and AC is the large artery trunks compliance, and τ is the Windkessel time constant, equals the product of TPR and AC, obtains proportional numerical value with cardiac output CO by following formula

(12) by gold index (for example ultrasonic method or thermodilution method) for

Calibrate, obtain proportionality coefficient, and then obtain real cardiac output CO.

Non-invasive cardiac output checkout gear based on pulse wave of the present invention adopts following technical solution:

This checkout gear comprises pulse wave detection device, testing circuit, cardiac output estimation unit and display device, and pulse wave detection device is connected with testing circuit, and testing circuit is connected with the cardiac output estimation unit, and the cardiac output estimation unit is connected with display device.

Pulse wave detection device comprises piezoresistive pressure sensor and fixed support, and piezoresistive pressure sensor is installed on the fixed support, the external pressure that is used to detect pulse wave He is applied to test point; Fixed support is made up of holder and sliding shoe, and holder is provided with guide rail, and sliding shoe is installed on the guide rail of holder, and sliding shoe top is equipped with the feeding bolt, and pressure transducer is placed on the sliding shoe.Sliding shoe drives pressure transducer along the horizontal movement of holder guide rail, and the feeding bolt links to each other with pressure transducer, and the feeding bolt rotates pressure transducer is moved up and down.The horizontal movement of pressure transducer is accurately positioned in directly over the test point it, and the external pressure that the assurance that moves up and down is applied to the test point place is suitable.

Testing circuit comprises an elementary amplifying circuit, a filter amplification circuit and an alternating current-direct current amount split circuit, elementary amplifying circuit is connected with filter amplification circuit, filter amplification circuit is connected with alternating current-direct current amount split circuit, be used for to detected pulse wave and pressure signal amplify, filtering, and separate through of ac and DC quantity after the amplification filtering, wherein, of ac is represented filtered pulse signal, and DC quantity is represented and the outside relevant numerical value of exerting pressure.Each circuit all adopts existing universal circuit, and elementary amplifying circuit adopts the high accuracy amplifier element that the detected differential wave of pulse wave detection device is carried out elementary amplification; Filter amplification circuit adopts the quadravalence low pass to amplify.

The cardiac output estimation unit is used for the signal of testing circuit output is carried out conversion, and estimates cardiac output according to the signal after the conversion, comprises following six parts:

The Signal Pretreatment unit is used for the AC signal and the direct current signal of testing circuit output are carried out analog digital conversion, and the digital signal after the conversion is resampled;

The outside detecting unit of exerting pressure demarcates to determine the size of exerting pressure in the outside by the isolated DC quantity of alternating current-direct current amount split circuit to testing circuit, to determine to be applied to the optimum pressure of person under inspection's test point;

The heart rate detection unit utilizes the characteristic point (for example ascending branch starting point, peak point or incisura etc.) on the pulse waveform to determine heart rate HR;

The pulse waveform analytic unit utilizes Mathematical Method to estimate timeconstant;

Pulse wave is demarcated the unit, according to pulse and blood pressure corresponding relation numerically, obtains mean arterial pressure MAP by the isolated of ac of alternating current-direct current amount split circuit of testing circuit is demarcated;

Cardiac output CO computing unit according to mean arterial pressure MAP that obtains and the timeconstant that estimates, calculates proportional numerical value with CO, again according to golden standard to calibrating of estimating to obtain with the proportional numerical value of CO, obtain real CO.

Display is adopted in display device, is used for real-time display pulse wave-wave shape, outside exert pressure numerical value, cardiac output CO and heart rate HR.

The present invention carries out mathematical analysis by the pulse waveform that detection is obtained and obtains cardiac output, has realized the non-invasive cardiac output detection.

Description of drawings

Fig. 1 is the flow chart of the non-invasive cardiac output detecting methods based on pulse wave of the present invention.

Fig. 2 is the pulse wave detection device sketch map.

Fig. 3 pulse wave detection device user mode sketch map.

Fig. 4 is typical pulse wave figure.

Fig. 5 is windkessel model (Windkessel model).

Fig. 6 is the theory diagram of the non-invasive cardiac output checkout gear based on pulse wave of the present invention.

Wherein: 1, pick off, 2, support, 3, holder, 4, sliding shoe, 5, the card falcon, 6a, the axial location sign, 6b, the axial location sign, 7, the radial location sign, 8, the feeding bolt, 9, be linked with post, 10, binder, 11, pulse wave detection device, 12, examined person's cervical region, 13, testing circuit, 14, the cardiac output estimation unit, 14a, the Signal Pretreatment unit, 14b, the outside detecting unit of exerting pressure, 14c, the heart rate detection unit, 14d, the pulse waveform analytic unit, 14e, pulse wave is demarcated unit, 14f, cardiac output CO computing unit, 15, display device.

The specific embodiment

Fig. 1 has provided the flow chart of the non-invasive cardiac output detecting methods based on pulse wave of the present invention.Utilize pulse wave detection device as shown in Figure 2 to detect position (as cervical region) detection pulse wave at health, convert digital signal to through after a series of processing, the applied mathematics analytical method is analyzed this digital signal again, and then estimates cardiac output and heart rate.Pulse wave detection device shown in Figure 2 comprises pick off 1 and fixed support 2, pick off 1 adopts piezoresistive transducer, fixed support 2 is made up of holder 3 and sliding shoe 4, pick off 1 is fixed in the sliding shoe 4, sliding shoe 4 both sides are respectively equipped with a card falcon 5, pin card falcon 5 sliding shoe 4 is slided along the guide rail horizontal direction on the holder 3.Be provided with three witness markers in holder 3 one sides: axial location sign 6a and 6b, radial location sign 7.During detection, regulate the position of support, carotid artery is axially alignd with axial location sign 6a and 6b line on the holder 3, a pulse wave radially projecting's aligning radial location sign 7 of beating.Above sliding shoe 4, be provided with a feeding bolt 8, rotate the contact pressure that this bolt can change probe and examined person's skin of pick off 1.Outermost is provided with and is linked with post 9 on the holder 3, and immovable bandage 10 is installed on it.This pulse wave detection device 11 is worn on person under inspection's the cervical region 12, as shown in Figure 3.Plug-type location and second positioning technology by the witness marker accurately arteries at detection and localization position of sliding shoe 4 on holder 3 guide rails; Adopt feeding bolt 8 the precession pressuring method can the position apply continuously, the external force of slight change to detecting, and when detected pulse waveform meets the demands, impressed pressure is fixed on numerical value at this moment and remains unchanged.Can determine heart rate according to the characteristic point on the pulse waveform (for example ascending branch starting point, peak point or incisura etc.).

Fig. 4 has provided the typical pulse waveform that pulse wave detection device obtains.Pulse wave is the heart contraction of measuring from periphery, the blood flow pulsation that diastole produced, and therefore the shape of this waveform has reflected the motion of heart.Because not matching of tremulous pulse middle impedance causes the relaxing period waveform to be disturbed by complicated wave reflection, no longer is pure exponential damping.The method that the present invention proposes is eliminated the interference of complicated wave reflection to the relaxing period waveform by the pulse waveform of analyzing a plurality of cardiac cycles, and then can utilize windkessel model (Windkessel model) as shown in Figure 5 to estimate cardiac output.

In the theory diagram of Fig. 6 has provided the non-invasive cardiac output checkout gear based on pulse wave of the present invention, this checkout gear comprises pulse wave detection device 11, testing circuit 13, cardiac output estimation unit 14 and display device 15, and each several part is connected in turn.The structure of detection pulse waveform and outside pulse wave detection device 11 of exerting pressure as shown in Figure 2.

Testing circuit 13 be used for to detected pulse wave and pressure signal amplify, filtering, and separate through of ac and DC quantity after the filtering amplification, wherein, of ac is represented filtered pulse signal, and DC quantity is represented and the outside relevant numerical value of exerting pressure.Cardiac output estimation unit 14 is used for the signal of testing circuit output is carried out a series of conversion, and estimates cardiac output according to the signal after the conversion.Cardiac output estimation unit 14 comprises following six parts again: Signal Pretreatment unit 14a, be used for the AC signal and the direct current signal of testing circuit 13 outputs are carried out analog digital conversion, and the digital signal after the conversion is resampled; The outside detecting unit 14b that exerts pressure by the isolated DC quantity of alternating current-direct current amount split circuit is demarcated to determine the size of exerting pressure in the outside, determines to be applied to the optimum pressure of test point with auxiliary detection person; Heart rate detection unit 14c utilizes the characteristic point (for example ascending branch starting point, peak point or incisura etc.) on the pulse waveform to determine heart rate HR; Pulse waveform analytic unit 14d utilizes Mathematical Method to estimate timeconstant; Pulse wave is demarcated unit 14e, according to pulse and blood pressure corresponding relation numerically, obtains mean arterial pressure MAP by the isolated of ac of alternating current-direct current amount split circuit is demarcated; Cardiac output CO computing unit 14f according to mean arterial pressure MAP that obtains and the timeconstant that estimates, calculates proportional numerical value with CO, again according to golden standard with calibrating of estimating to obtain with the proportional numerical value of CO, obtain real CO.Display device 15 is used for real-time display pulse wave-wave shape, show in real time the outside exert pressure numerical value, show cardiac output CO, show heart rate HR.

Claims (5)

1. the non-invasive cardiac output detecting methods based on pulse wave is characterized in that, may further comprise the steps:

(1) utilize pulse wave detection device to obtain the pressure pulse signal, the pressure pulse signal is amplified and filtering, and isolate through of ac and DC quantity after the amplification filtering, wherein, of ac is represented filtered pulse signal, and DC quantity is represented and the outside relevant numerical value of exerting pressure;

(2) of ac and DC quantity are carried out analog digital conversion, the digital signal after the conversion is resampled; Utilize the characteristic point on the pulse waveform to determine heart rate HR; By isolated DC quantity being demarcated to determine the size of exerting pressure in the outside, to determine the optimum pressure of person under inspection's test point;

(3) utilize Mathematical Method to estimate timeconstant to isolated of ac;

(4) pulse wave is demarcated, obtained mean arterial pressure MAP

(5) calculate cardiac output CO according to MAP and τ.

2. non-invasive cardiac output checkout gear based on pulse wave, it is characterized in that: comprise pulse wave detection device, testing circuit, cardiac output estimation unit and display device, pulse wave detection device is connected with testing circuit, testing circuit is connected with the cardiac output estimation unit, and the cardiac output estimation unit is connected with display device.

3. the non-invasive cardiac output checkout gear based on pulse wave according to claim 2, it is characterized in that: described pulse wave detection device comprises piezoresistive pressure sensor and fixed support, piezoresistive pressure sensor is installed on the fixed support, fixed support is made up of holder and sliding shoe, holder is provided with guide rail, sliding shoe is installed on the guide rail of holder, and sliding shoe top is equipped with the feeding bolt, and pressure transducer is placed on the sliding shoe.

4. the non-invasive cardiac output checkout gear based on pulse wave according to claim 2 is characterized in that: described testing circuit comprises an elementary amplifying circuit, a filter amplification circuit and an alternating current-direct current amount split circuit.

5. the non-invasive cardiac output checkout gear based on pulse wave according to claim 2 is characterized in that: described cardiac output estimation unit comprises following six parts:

The Signal Pretreatment unit is used for the AC signal and the direct current signal of testing circuit output are carried out analog digital conversion, and the digital signal after the conversion is resampled;

The outside detecting unit of exerting pressure demarcates to determine the size of exerting pressure in the outside by the isolated DC quantity of alternating current-direct current amount split circuit to testing circuit, to determine to be applied to the optimum pressure of person under inspection's test point;

The heart rate detection unit utilizes the characteristic point (for example ascending branch starting point, peak point or incisura etc.) on the pulse waveform to determine heart rate HR;

The pulse waveform analytic unit utilizes Mathematical Method to estimate timeconstant;

Pulse wave is demarcated the unit, according to pulse and blood pressure corresponding relation numerically, obtains mean arterial pressure MAP by the isolated of ac of alternating current-direct current amount split circuit of testing circuit is demarcated;

Cardiac output CO computing unit according to mean arterial pressure MAP that obtains and the timeconstant that estimates, calculates proportional numerical value with CO, again according to golden standard to calibrating of estimating to obtain with the proportional numerical value of CO, obtain real CO.

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