JP2509828B2 - Respiratory wave measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a respiratory wave measuring device for measuring a respiratory wave or a ventilation volume by an electrocardiogram signal.

[0002]

2. Description of the Related Art Respiration influences other biological phenomena by its physiological activity. For example, a change in volume in a body cavity due to respiration changes the visceral position in the body cavity and changes the electrical characteristics of the body viewed from outside the body. . In particular, the pericardium of the heart is in contact with the diaphragm and is strongly physically affected by breathing. Therefore, although the amplitude and baseline of the electrocardiogram change with breathing,
On the contrary, there is a possibility that information on respiration can be extracted from this fluctuation. Computer issued by IEEE Computer Society in 1985
in Cardiology, Volume 12, pages 113-116,
It has been proposed that the tidal volume can be estimated from the change in the direction by expressing the change of the heart by MOODY and the like with the average electric axis obtained from the electrocardiogram.

FIG. 8 shows the configuration of a respiratory wave measuring apparatus based on this proposal. The electrodes 1, 2, 3 are provided on both wrists and the left foot.
The lead-to-lead III is detected by wearing the, and the electrocardiographic signal of the lead-I from the electrocardiograph 4 and the average value of the potentials obtained from the three electrodes and the potential obtained from the left foot electrode 3. The aVf lead electrocardiogram signal is output, and further digitized by the A / D converter 5 to be output to the personal computer 6.
Is being supplied to.

In this personal computer, the maximum and minimum points of the QRS wave are first detected by the differentiation method known per se for the QRS wave of the I-th lead and the aVf lead as shown in FIG. Next, the R wave amplitude A _R1 and S wave amplitude A _{S1 of the} first lead, which are the horizontal axis components of the average heart vector, and the R wave amplitude A _R2 and S wave amplitude A _S2 of the aVf lead, which are the vertical axis components, are detected. Then, based on the amplitude data of these two types of amplitude induction, θ indicates the direction of the average electric axis for each heartbeat.
₀ is detected according to the following formula. θ ₀ = tan ⁻¹ {(A _R2 + A _S2 ) / (A _R1 + A _S1 )} (1) Then, the estimated respiratory wave curve is obtained by connecting the plot data of each θ ₀ , and its PP value Measure tidal volume from (amplitude between maximum and minimum values).

[0005]

According to the present invention, it has been confirmed that a respiratory wave or a ventilation volume curve can be obtained based on an electrocardiogram signal without attaching a respiratory sensor to the subject's mouth. It is an object of the present invention to provide a respiratory wave measuring device capable of measuring a respiratory wave, and thus a ventilation volume, with higher accuracy by an electrocardiogram signal.

[0006]

In order to achieve this object, the present invention, as shown in FIG. 1, inputs an induction signal induced to an electrode attached to a living body so that a heart vector can be detected. As an electrocardiogram signal detection circuit 1 for outputting at least two corresponding electrocardiogram signals capable of defining a heart vector
When, R wave amplitude which constitutes the detected two R-wave amplitudes A _R1 and S wave amplitude A _S1 and the vertical axis component constituting the horizontal axis component of the cardiac base <br/> vector from QRS waves in ECG signals Electrocardiogram signal analysis means 2 for detecting A _R2 and S wave amplitude A _S2, and the direction of the absolute sum type electric axis for each heartbeat based on the absolute values of the detected amplitudes A _R1 , A _S1 , A _R2 , A _S2 θ is θ = t
an ⁻¹ {(| A _R2 | + | A _S2 |) / ( | A _R1 |
+ | A _S1 |)} is used to form a respiratory wave curve that generates a respiratory wave curve by creating an approximate curve that sequentially connects data indicating the direction of each absolute sum type electric axis that is sequentially calculated. Means 4 and output means 5 for displaying or recording the respiratory wave curve are provided. In order to obtain the tidal volume of respiration numerically, the ventilation volume calculating means 6 for calculating the tidal volume from the respiratory wave curve formed by the respiratory wave forming means 4 is provided, and the respiratory wave curve is further displayed or recorded. Instead of or in addition to the output means 5, the output means 7 for numerically displaying the ventilation volume is provided.

[0007]

The electrocardiogram signal detection circuit 1 outputs an electrocardiogram signal of a lead in the orthogonal direction of the heart vector or a lead of a predetermined angle convertible to the orthogonal axis. The electrocardiogram signal analyzing means 2 uses the RRS amplitudes A _R1 and S wave amplitudes A _S1 forming the horizontal axis component of the average heart vector and the R wave amplitudes A _R2 and S waves forming the vertical axis components from the QRS waves in the electrocardiogram signal. The amplitude A _S2 is detected. The calculation means 3 detects the detected amplitudes A _R1 , A _S1 , A
_R2, the absolute value the following formula for each heartbeat based on the A _S2 calculates the direction θ of the absolute sum electrical axis. θ = tan ⁻¹
{(| A _R2 | + | A _S2 |) / ( | A _R1 | + | A
_S1 |)} (2) The respiratory wave forming means 4 creates an approximate change curve connecting the calculated θ's, and causes the output means 5 to display or record the respiratory wave curve.

[0008]

FIG. 2 shows the configuration of a respiratory wave measuring apparatus according to an embodiment of the present invention. In the figure, 18 is a electrocardiograph which receives the induced voltage detected by the electrodes 1-3 as described above, and outputs the various ECG signals, including the first I-induced and aVf induction. 20 is a CPU, ROM21, RA
By attaching M22 and I / O boat 23, etc.,
The above-mentioned electrocardiogram signal analyzing means, computing means and respiratory wave forming means are configured. The I / O boat 23 has a cathode ray tube display device 24 for displaying a respiratory wave, and a printer 2 for recording the data.
A numerical value display 26 for numerically displaying 5 and the tidal volume is connected.

[0009] CPU20 is crowded preparative electrocardiogram signal of the I-induced and aVf induction digitized by the A / D converter 19, a known per se the differential method, first each of the maximum and minimum time point of the QRS wave To detect. Then
R wave amplitude A _{R1 of} lead I, which is the horizontal axis component of the heart vector
And the S wave amplitude A _S1 are detected, and a vertical axis component a
The R wave amplitude A _R2 and the S wave amplitude A _S2 of the Vf induction are detected. Then, the amplitudes A _R1 , A detected for each heartbeat
_{Based on S1} , A _R2 and A _S2 , the electric axis θ based on the absolute sum is detected according to the above-mentioned formula (2) along the average electric axis direction θ ₀ based on the so-called algebraic sum. Further, based on the plot data of each θ calculated for each heartbeat, an approximate respiratory wave curve is created by, for example, the cubic spline interpolation method. Furthermore, the P-P value is obtained based on the measured respiratory wave curve, and the actual tidal volume is calculated by multiplying it by the conversion coefficient determined based on the ventilation volume measured by the respiratory sensor in advance. .

The operation of the respiratory wave measuring apparatus configured as described above will be described. The induction potential obtained from each electrode is the electrocardiograph 1
8 and the CPU 20 is supplied with the digitized electrocardiogram signal a (FIG. 3) through the I / O port 23. As a result, for each heartbeat, the R wave amplitude A _{R1 of} lead I
And S wave amplitude A _{S1 and} aVf induced R wave amplitude A _R2 and S wave amplitude A _S2 are detected to calculate θ. That is, FIG.
As shown in A, it is obtained as an angle with respect to the horizontal axis of a diagonal line D of a rectangle R circumscribing a heart vector loop L formed by combining two types of electrocardiographic signals for each heartbeat.
Incidentally, FIG. 4B shows the conventional algebraic sum according to the equation (1) by a similar vector loop.

Subsequently, plot data θ which is sequentially calculated
The respiratory wave curve b (FIG. 3) is created by the cubic spline interpolation method based on the above, and the ventilation volume is calculated. As a result, the respiratory wave curve is displayed on the cathode ray tube display device 24 together with the normal electrocardiographic signal and is printed out on the printer 25, and the tidal volume is numerically displayed on the numerical display 26 for each respiratory cycle.

FIG. 6 shows a test example using such an absolute sum type device and a conventional algebraic sum type device. The change data of the angle indicating the direction of the electric axis with respect to the tidal volume of 0 to 3 liters is shown. The case where about 70 points are plotted is shown. Table 1 shows that such a test was conducted on four more people,
By obtaining the correlation coefficient of each, it was confirmed that the respiratory wave was detected with higher accuracy than the conventional algebraic sum method.

[0013]

[Table 1]

When the ventilation volume is measured by leads I and III without deriving the aforementioned aVf lead,
The orthogonal direction component _AT for the lead I is calculated from the QRS wave signals of the lead I and the lead III according to the following equation based on the geometrical relationship shown in FIG. A _T = | A ₁ | / tan 60 ° + | A ₃ | / sin 60 ° That is, the R-wave amplitude A _R2 and the S-wave amplitude A _S2 of the orthogonal component are first detected by this conversion formula. And
Horizontal wave component R-wave amplitude A _R1 and S-wave amplitude A of lead I
Θ is detected along with _{S1 according} to the above-mentioned equation (2). Furthermore, it is possible to measure by guiding the electrodes arranged on the chest, on condition that the electrode arrangement is such that the heart vector can be detected. In particular, in order to eliminate the need for conversion to orthogonal axes, it is conceivable to arrange four electrodes in a cross shape in a vertical and horizontal direction around the heart on the chest. The lateral electrode arrangement does not necessarily have to be horizontal. The present invention can be attached to an electrocardiograph or can be implemented as a dedicated device.

[0015]

As described above, according to the present invention, the respiratory wave curve can be detected more faithfully by the electrocardiogram signal based on the absolute sum type electric axis. Thereby, the ventilation amount can be detected with high accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a respiratory wave measuring apparatus according to the present invention.

FIG. 2 is a diagram showing a configuration of a respiratory wave measuring apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing operation waveforms of the apparatus of the embodiment.

4A and 4B show a relationship between a heart vector loop and an electric axis. FIG. 4A is a diagram according to the embodiment and FIG. 4B is a conventional diagram.

FIG. 5 is a diagram illustrating an amplitude relationship of QRS waveforms in an electrocardiogram.

FIG. 6 shows a test example of a respiratory wave measuring apparatus, which is shown in FIG.
Is the absolute sum method of the embodiment, and FIG. 9B is the conventional algebraic sum method.

FIG. 7 is a diagram for explaining the operation of the respiratory wave measuring apparatus according to another embodiment.

FIG. 8 is a diagram showing a schematic configuration of a respiratory wave measuring apparatus using a personal computer.

[Explanation of symbols]

 1, 2, 3 electrodes

Claims (2)

(57) [Claims] 1. An electrocardiogram signal detection circuit which receives an induction signal induced in an electrode attached to a living body so as to detect a heart vector and outputs at least two kinds of corresponding electrocardiogram signals capable of defining a heart vector. When, R wave amplitude a _R1 and S wave amplitude a _S1 constituting the horizontal axis component of the QRS wave or al heart vector <br/> Le in the detected two ECG signal
And R wave amplitude A _R2 and S wave amplitude A that constitute the vertical axis component
_{Based on} the absolute values of the detected amplitudes A _R1 , A _S1 , A _R2 , and A _S2 , the electrocardiographic signal analysis means for detecting _S2, and the direction θ of the absolute sum type electric axis for each heartbeat, θ = tan ⁻¹ {(| A _R2 | + | A _S2 |) / ( | A _R1 | +
| A _S1 |) and calculating means for calculating a}, respiratory wave forming means for forming a breathing wave curve by creating an approximate curve connecting the direction of the data in the order of the absolute sum type electric shaft that is over time computation And a respiratory wave measuring device comprising an output means for displaying or recording a respiratory wave curve. 2. A ventilation volume calculating means for calculating a tidal volume from a respiratory wave curve formed by the respiratory wave forming means, and one or a combination of the output means for displaying or recording the respiratory wave curve. The respiratory wave measuring apparatus according to claim 1, further comprising output means for numerically displaying the respiration volume.