JP2010082362A - Ventricular volume measurement apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ventricular volume measurement apparatus by which power consumption is reduced and consumption of a battery is suppressed to enable the apparatus to be continuously usable for a long time even when the apparatus is embedded in a body. <P>SOLUTION: The ventricular volume measurement apparatus 1 includes: two current electrodes 2 and two detection electrodes 4 arranged across the ventricle A; a current control part 3 to supply composite alternating current obtained by combining two frequencies with each other set so that one is n times as large as the other (where, n is an integer of ≥2); and a ventricular volume calculation part 6 to calculate a ventricular volume on the basis of the composite alternating current supplied between the two current electrodes 2 and a voltage value detected between the detection electrodes 4. When the cycle of current on the low frequency side is smaller than a sampling cycle required for the measurement of a ventricular volume, the current control part 3 supplies the composite alternating current for only one cycle portion of the current on the lower frequency side among the sampling cycles and stops supply of the composite alternating current during the rest period. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a ventricular volume measuring device.

  Conventionally, a current obtained by combining a synthetic alternating current obtained by synthesizing currents of two frequencies set so that one is n times the other (where n is an integer of 2 or more) with the ventricle interposed therebetween. A voltage value supplied between the electrodes and detected between the detection electrodes arranged across the ventricle is captured 2n times during one cycle on the low frequency side at the positive and negative peaks of the synthesized alternating current, and based on the voltage value There is known a ventricular volume measuring device that measures temporal variation of ventricular volume by continuously calculating ventricular volume conductance (see, for example, Patent Document 1).

JP 2005-253834 A

However, the ventricular volume measuring device disclosed in Patent Document 1 is configured so that the current generation circuit always operates and generates a combined alternating current even when the sampling period necessary for the measurement of the ventricular volume conductance is larger than the current period on the low frequency side. Since the power is supplied, there is a disadvantage that power consumption is large and the battery is consumed.
The present invention has been made in view of the above-described circumstances, and can be used continuously over a long period of time even when it is embedded in the body while reducing power consumption and suppressing battery consumption. An object is to provide a heart volume measuring device.

In order to achieve the above object, the present invention provides the following means.
In the present invention, two current electrodes and two detection electrodes arranged with the ventricle in between, and one between the current electrodes is n times the other (where n is an integer of 2 or more). Based on a current control unit that supplies a combined AC current obtained by combining currents of two frequencies set to, a combined AC current supplied between the current electrodes, and a voltage value detected between the detection electrodes A ventricular volume calculating unit that calculates a ventricular volume, and the current control unit is configured to select a low one of the sampling periods when a low-frequency current period is smaller than a sampling period necessary for measuring the ventricular volume. Provided is a ventricular volume measuring device that supplies a synthetic alternating current for one period of a frequency-side current and stops supplying the synthetic alternating current for the remaining period.

  According to the present invention, a synthetic alternating current is supplied from the current control unit to the current electrode, and the ventricular volume can be calculated based on the voltage appearing between the detection electrodes. The synthesized alternating current is composed by synthesizing two currents having a frequency of 1 and an n-fold frequency, and the voltage value of the positive and negative peaks of the current on the high frequency side is 2n times during one cycle on the low frequency side. By taking it in, the ventricular volume can be measured.

  In this case, in order to measure the time change of the ventricular volume, it is sufficient to measure one period on the low frequency side during the sampling period necessary for the measurement of the ventricular volume. If the period is less than the sampling period required for ventricular volume measurement, the combined AC current supply is stopped for the time exceeding the current period on the low frequency side to minimize power consumption. Can do. As a result, battery consumption can be suppressed and continuous use over a long period of time can be achieved.

In the above invention, the current control unit has a current value at the start of supply of the combined alternating current between the current electrodes and a current value at the stop of supply of current equal to a current value at the stop of supply of the combined alternating current, and It is good also as supplying a synthetic | combination alternating current so that the primary differential value may become zero.
By doing in this way, it is suppressed that a high frequency component is included in the synthetic | combination alternating current interrupted by the supply and stop of synthetic | combination alternating current at a supply start time and a supply stop time, and it is a simple circuit and few The synthesized alternating current can be synthesized and supplied with the power consumption. As a result, battery consumption can be further suppressed.

Further, in the above invention, the current control unit is configured so that the integrated value of the combined alternating current during supply is substantially zero with reference to the current value during the supply stop of the combined alternating current between the current electrodes. An alternating current may be supplied.
By doing so, the direct current component included in the combined alternating current is reduced, and inconvenience when the direct current component is included, for example, the occurrence of waveform disturbance when passing through the direct current cut circuit in the detection circuit can be prevented with high accuracy. Ventricular volume can be measured.

  According to the present invention, power consumption is reduced, battery consumption is suppressed, and even when the battery is embedded in the body, it can be used continuously over a long period of time.

A ventricular volume measuring device 1 according to an embodiment of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, the ventricular volume measuring apparatus 1 according to the present embodiment includes two current electrodes 2 arranged with a ventricle A interposed therebetween, and a current control unit 3 that supplies current between the current electrodes 2. Similarly, two detection electrodes 4 arranged with the ventricle A in between, a voltage detection unit 5 for detecting a voltage between the detection electrodes 4, and a ventricular volume based on a voltage value detected by the voltage detection unit 5 And a calculation unit 6 for calculation. The current control unit 3, the voltage detection unit 5, and the calculation unit 6 are driven by a battery (not shown).

  As shown in FIG. 2, the current control unit 3 includes a waveform generation unit 7 that generates a combined AC voltage obtained by combining two waveform voltages different in frequency by n times, and a combined AC generated in the waveform generation unit 7. A conversion unit 8 that converts a voltage into a combined AC current and a DC cut circuit 9 that cuts a DC component in the combined AC current converted by the conversion unit 8 are provided.

  The voltage detector 5 includes a DC cut circuit 10 that cuts a DC component of the voltage appearing between the detection electrodes 4, an amplifier 11 that amplifies the AC voltage from which the DC component is cut, and the amplified AC voltage. As shown by a symbol B, a sampling unit 12 that samples a voltage value at the positive and negative peaks of the combined AC current is provided.

  The current control unit 3 and the voltage detection unit 5 are arranged between the current electrodes 2 as shown in FIG. 2 when the period X necessary for measuring the ventricular volume is longer than the period Y on the low frequency side of the supplied current. Current supply and voltage measurement and ventricular volume calculation operation through the detection electrode 4 are performed for one cycle Y on the low frequency side of the current to be supplied, and for the remaining period Z, current supply between the current electrodes 2 and All of the voltage measurement via the detection electrode 4 and the calculation operation of the ventricular volume are stopped.

  The calculation unit 6 can calculate conductance according to the blood volume between the detection electrodes 4 corresponding to the two frequencies by calculating and subtracting the sampled voltage value. Ventricular volume and blood volume are substantially equivalent, and these values are proportional to ventricular volume. Therefore, the ventricular volume can be accurately measured by accurately obtaining this conductance (hereinafter referred to as ventricular volume conductance).

The operation of the ventricular volume measuring apparatus 1 according to the present embodiment configured as described above will be described below.
In order to measure the ventricular volume using the ventricular volume measuring apparatus 1 according to the present embodiment, two current electrodes 2 and two detection electrodes 4 are arranged across the ventricle A, and the current electrodes are operated by the operation of the current control unit 3. Between the two, a combined alternating current obtained by combining currents of two frequencies is supplied. Since a voltage corresponding to the value of the synthetic AC current and the value of the ventricular volume conductance appears between the detection electrodes 4, the sampling unit 12 samples the voltage value at the time of the positive and negative peaks of the synthetic AC current. And the ventricular volume is calculated in the calculating part 6 using the sampled voltage value.

  In this case, according to the present embodiment, the sampling necessary for the measurement of the ventricular volume is sufficient for one cycle on the low frequency side of the synthetic AC current. There is no need for supply, voltage value detection, sampling and ventricular volume calculations. Therefore, as shown in FIG. 2, during the period Z exceeding one cycle, the operation of the current control unit 3, the voltage detection unit 5, and the calculation unit 6 is stopped to save power and suppress battery consumption. can do. FIG. 4 shows a conventional synthesized alternating current waveform.

When the period X necessary for measuring the ventricular volume is shorter than the period Y on the low frequency side of the current to be supplied, the period Y may be shortened by increasing the frequency on the low frequency side. .
Moreover, when the synthetic | combination alternating current applied to the current electrode 2 is interrupted like the ventricular volume measuring apparatus 1 which concerns on this embodiment, as shown in FIG. 5, in both the electric current supply start time P and the stop time Q The current value is preferably equal to the stopped current value I ₀ and the first derivative of the current value is preferably zero.

If the current value is not equal to the stopped current value I ₀ at the start of current supply P or at the time of stop Q, as shown in FIG. 6, a synthesized alternating current with a steep rise and fall must be synthesized. This complicates a circuit for generating a synthetic alternating current including a high frequency component. On the other hand, by supplying a synthetic alternating current having a waveform as shown in FIG. 5, a circuit can be configured using a low-speed semiconductor element, and further power saving can be achieved at low cost.

Further, as shown in FIG. 5, it is preferable that the synthetic AC current to be supplied has a waveform such that the integrated value thereof is substantially zero with reference to the current value I ₀ during the stop.
As shown in FIG. 7, the synthesized alternating current that is either positive or negative with respect to the stopped current value I ₀ includes a direct current component, so that the waveform is disturbed at the outlet of the direct current cut circuit 9 in the current control unit 3. Therefore, there is a disadvantage that the ventricular volume conductance cannot be accurately measured.

The DC cut units 9 and 10 are for blocking the virtual ground potential in the circuit constituting the current control unit 3 and the voltage detection unit 5 to the living body and blocking the DC potential by the contact between the living body and the electrodes 2 and 4 to the circuit. Is necessary.
Therefore, by adopting the waveform of the synthetic alternating current as shown in FIG. 5, there is an advantage that the ventricular volume can be measured with high accuracy without the above-mentioned disadvantages.

It is a block diagram which shows the ventricle volume measuring apparatus which concerns on one Embodiment of this invention. It is a figure which shows an example of the waveform of the synthetic | combination alternating current supplied by the electric current control part of the ventricular volume measuring apparatus of FIG. It is a figure which shows an example of the synthetic | combination alternating current of FIG. 2, and a voltage detection position. It is a figure which shows the conventional synthetic | combination alternating current as a comparative example of FIG. It is a figure which shows another example of the waveform of the synthetic | combination alternating current supplied by the electric current control part of the ventricular volume measuring apparatus of FIG. It is a figure which shows the comparative example of the waveform of the synthetic | combination alternating current supplied by the current control part of the ventricular volume measuring apparatus of FIG. It is a figure which shows the other comparative example of the waveform of the synthetic | combination alternating current supplied by the electric current control part of the ventricular volume measuring apparatus of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ventricular volume measuring apparatus 2 Current electrode 3 Current control part 4 Detection electrode 6 Calculation part (ventricular volume calculation part)

Claims (3)

Two current electrodes and two detection electrodes arranged across the ventricle;
Current control for supplying a composite alternating current obtained by combining currents of two frequencies set so that one is n times the other (where n is an integer of 2 or more) between the current electrodes. And
A ventricular volume calculation unit that calculates a ventricular volume based on a combined alternating current supplied between the current electrodes and a voltage value detected between the detection electrodes;
The current control unit supplies a composite alternating current for one cycle of the low frequency side current out of the sampling cycle when the cycle of the low frequency side current is smaller than the sampling cycle necessary for measuring the ventricular volume. And the ventricular volume measuring device which stops supply of a synthetic | combination alternating current during the remaining period.   The current control unit is configured such that the current value at the start of supply of the composite AC current between the current electrodes and the stop of current supply is equal to the current value at the stop of supply of the composite AC current, and the primary differential value thereof is The ventricular volume measuring apparatus according to claim 1, wherein the synthetic alternating current is supplied so as to be zero.   The current control unit supplies the combined AC current so that an integrated value of the combined AC current during supply becomes substantially zero with reference to a current value when the supply of the combined AC current between the current electrodes is stopped. 2. The ventricular volume measuring device according to 2.

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