JPH04336035A - Respiratory waveform estimating method employing electrocardiogram - Google Patents

Abstract

PURPOSE:To improve precision during estimation of a respiratory waveform from an electrocardiogram and to relieve a burden on a person to be examined and to simplify a measuring system by changing a measuring electrocardiogram from two channels to one channel. CONSTITUTION:Respiration is estimated by taking a change in an angle of a T-vector into consideration. A QRS vector and a T-vector are projected on one and the same axis to determine a projection axis for converting a change of an angle into a change of amplitude. The position of a breast part mounting electrode is decided along the projection axis and from the inside of the magnitude of the QRS wave and the T-wave of an electrocardiogram and the magnitude of an QRS wave or the magnitudes of the QRS wave and the T-wave, a respiratory curve is estimated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a respiration estimation method for estimating a respiration waveform from an electrocardiogram without measuring respiration.

0002

[Prior Art] Respiration is measured by attaching a sensor whose electrical resistance changes due to expansion and contraction to the abdomen or chest of the person to be measured (for example, Japanese Patent Application Laid-Open No. 62-362, easy-to-understand ME [Sanpo Publishing Co., Ltd., first edition published April 10, 1971] P.55-56) is simple and has been used more often than before. In this method, respiration is detected as an electrical signal by utilizing the fact that the resistance of the sensor changes in proportion to the movement of the abdomen or chest due to respiration of the subject. The electrical signal is amplified to a predetermined signal level by an amplifier after removing unnecessary DC components and low frequency components using a high-pass filter. Thereafter, it is displayed on a display device such as a cathode ray tube oscilloscope or recorded using a recording device such as a data recorder. Another example is a method of measuring respiration by using a temperature sensor as a detection means and attaching it near the nostrils to detect the temperature difference between exhaled and inhaled air.
No. 2-145603, Japanese Utility Model Application No. 64-3603, and Japanese Utility Model Application No. 1-65009), a respiration monitor device that uses the temperature sensor and chest impedance detection in combination (
Japanese Utility Model Publication No. 1-37949), a method for detecting breathing by generating sound by exhalation and inhalation airflow (Japanese Unexamined Patent Publication No. 1-37949),
79445), etc.

[0003] On the other hand, as a method for estimating respiration from an electrocardiogram, "Estimation of tidal volume from an electrocardiogram" presented at the 5th Symposium on Biological and Physiological Engineering (Proceedings of the same symposium, pp. 277-280) was proposed. be. In this method, as shown in FIG.
Measure the electrocardiogram of the leads, find the QRS magnitude of each electrocardiogram, and combine the vectors plotted in 61 and 62 to obtain 21 QRS vectors.
The respiration waveform is estimated from the change in the angle θ between the RS vector and the I-th lead axis.

Next, the operation for estimating respiration from the electrocardiogram will be explained. FIG. 7 is a block diagram of hardware according to this method. In FIG. 7, 71 is an electrocardiogram amplifier for amplifying the electrocardiograms of lead I and III of the standard limb leads, 72 is an A/D converter, and 73 is a computer. The two types of electrocardiograms amplified by the amplifier 71 are each converted into digital values by the A/D converter 72 in 1 millisecond, and then input into the computer 73. FIG. 8 is a flowchart showing an algorithm for estimating a respiratory waveform from the sample data. In Figure 8,
First, in step 81, a moving average of 10 points before and after is performed in order to remove commercial frequency components included in the sample data. Subsequently, the QRS determination unit 82 automatically detects the peak points of the Q wave, R wave, and S wave for each heartbeat of the electrocardiogram sample data. Then, the QRS vector calculation unit 83 calculates the magnitudes of the lead I and III electrocardiogram waveforms at each of the detected peak points, and calculates the magnitudes of the lead I and III electrocardiogram waveforms at each of the detected peak points,
Both vectors are combined as a II lead coordinate component vector to calculate the angle of the QRS vector. The calculated angle data is interpolated by the cubic spline interpolation method in a data interpolation unit 84 to obtain a continuous curve, and in 85 this continuous curve is outputted as an estimated respiration curve.

[0005]

[Problem to be solved by the invention] In the above respiratory waveform estimation method, the relationship between heart rate and breathing rate is (breathing rate ÷ heart rate) ≧1.
/2, the problem is that the original continuous fluctuation of the QRS vector is not reproduced, resulting in an error in respiratory waveform estimation.

[0006] Furthermore, in the respiration measurement that has been commonly carried out in the past, there has been a problem in that, as mentioned above, it is necessary to separately attach a respiration sensor to the person to be measured, which increases the burden on the person to be measured. Therefore, if the respiratory waveform is estimated from the electrocardiogram, there is no need to wear the respiratory sensor. However, in the above-mentioned method of estimating a respiratory waveform from an electrocardiogram, electrodes are attached to the limbs of the subject, so the problem that the movement of the subject is greatly restricted cannot be solved. Furthermore, even if the patient's limbs are released by guiding the electrocardiogram on the chest or the like to estimate respiration in order to correspond to standard limb guidance, the electrocardiogram must be measured in two channels, and the electrocardiogram amplifier is Two are required.

[0007] This invention was made to solve the above-mentioned problems, and is highly accurate even when the relationship between heart rate and breathing rate is (breathing rate ÷ heart rate) ≧ 1/2. The purpose is to obtain a respiration estimation method that can perform estimation.

[0008] Furthermore, by estimating the respiratory waveform from the electrocardiogram, it is not necessary to attach a respiratory sensor to the subject, and furthermore, the restriction on the movement of the limbs of the subject is removed, and the electrocardiogram to be measured is made into one channel. The purpose is to simplify the software.

[0009]

[Means for Solving the Problems] The respiration estimation method according to the present invention takes into account not only the angle of the QRS vector but also the angle of the T vector, and combines the angle data of both vectors into one data file. By estimating the respiration curve by doubling the number of data to be interpolated, highly accurate estimation can be made even in the case of (respiration rate ÷ heart rate) ≧ 1/2, which is the problem mentioned above. It is.

[0010] Furthermore, in order to remove restrictions on the movement of the extremities of the subject and to measure the electrocardiogram in one channel, a projection axis is determined in which the angular change in the QRS vector results in an amplitude change, and the projection axis is determined along this projection axis. The electrode position to be attached to the chest of the subject is determined, only one channel of the chest lead electrocardiogram is measured, and the respiratory waveform is estimated from the magnitude of the QRS of this electrocardiogram.

Furthermore, in order to improve the accuracy of the above-mentioned respiratory waveform estimation, one projection axis is determined in which the angular change of the QRS vector and the angular change of the T vector correspond to the amplitude changes of the QRS wave and the T wave, respectively. The respiratory waveform is estimated from the QRS wave size and the T wave size of the electrocardiogram derived by determining the electrode attachment position to be attached to the chest.

0012

In the respiration estimation method according to claim 1 of the present invention, estimation accuracy is improved by estimating the respiration waveform using both angular changes of the QRS vector and the T vector.

[0013] Furthermore, in the respiration estimation method according to claims 2 and 3, there is no need to attach electrodes to the limbs, so both arms can be moved, reducing the load on the person to be measured, and the electrocardiogram to be measured is Since there is only one channel, the measurement system can be simplified.

[0014]

【Example】

Example 1. FIG. 1 is a flowchart showing an embodiment according to claim 1. In FIG. 1, reference numeral 11 indicates two-channel electrocardiogram data measured by standard limb leads as in the conventional example. 12 to 15 are configured to calculate the angle of the T vector in addition to calculating the QRS vector angles 82 and 83 in FIG. 8 in the conventional example. In 16, the above 1
Angle data for each heartbeat, QRS, T, QRS, T...
In this way, the data are arranged on the same time axis in the order of occurrence, with the time relationships of the peak points unchanged, and are combined into one data string. At this time, if the magnitude of the angular change between the QRS vector and the T vector is different, the angle data of the T vector is corrected using a correction coefficient determined in advance. In steps 17 and 18, the data string is interpolated and converted into a continuous curve, which is output as an estimated respiratory waveform.

[0015] In the respiration estimation method as described above, two pieces of angle data are obtained for one heartbeat, and the data used for interpolation is twice that of the case where only the QRS vector is used. Therefore, the relationship between heart rate and respiration rate seen in the conventional example is (
Even in the case where (respiration rate ÷ heart rate)≧1/2, highly accurate estimation can be performed.

Example 2. FIG. 2 is an explanatory diagram of how to determine the position of an electrode to be attached to the chest in order to detect the angular change of the QRS vector due to respiration as a monotonous change in the QRS magnitude. In the figure, 21 represents the QRS vector that changes with respiration, and 22 represents the angle formed by the QRS vector. At this time, when the QRS vector is projected in the direction shown by the broken line 23 passing through the heart position, a difference in magnitude corresponding to the angular difference is obtained, as shown by 24. Therefore, by attaching an electrode to the position indicated by 25 and detecting the electrocardiogram from the chest, the respiratory waveform can be estimated from the change in QRS magnitude.

FIG. 3 is a flowchart of an embodiment for estimating a respiratory waveform from an electrocardiogram measured as described above. In the figure, numeral 31 is data obtained by sampling the measured one-channel electrocardiogram, and numeral 32 is the data from which the QRS peak time is detected in the same manner as in the first embodiment. At step 33, the magnitude of the QRS wave at the peak point determined at step 32 is determined. As shown in Figure 4, the magnitude of the QRS is the algebraic sum of the Q, R, and S amplitudes based on the baseline B of 41, that is, BQ+B.
R+BS or each area S1 indicated by 42 to 44
, S2 , S3 calculated by S1 −S2 −S3
, or the average value obtained by integration. The data string of the QRS wave size obtained in this manner is interpolated at 17 and converted into a continuous waveform, and outputted at 18 as a respiratory waveform.

The respiration estimation method described above has the same estimation accuracy as the conventional respiration estimation method, but since it is only necessary to derive one channel of electrocardiogram from the chest, the measurement system can be simplified, and the measurement This can reduce the burden of

Example 3. FIG. 5 is a flowchart of an embodiment for improving the estimation accuracy from the above estimation based on the size of the QRS wave. In the figure, electrocardiogram data 51 is sample data of a thoracic lead electrocardiogram based on the electrode position determined by adding the direction of the T vector to FIG. 32
~53 determines the magnitude of the QRS wave and T wave. As with the QRS wave, the peak value, area, average value, etc. are used for the magnitude of the T wave. In step 54, the magnitude of the T wave is corrected in the same manner as in Example 1, and the data are arranged on the same time axis in order of occurrence time.
Create interpolated data with twice the number of data. 17, the above Q
A continuous curve is obtained by interpolating the data in the same way as interpolating the magnitude of the RS wave. In step 18, the obtained continuous curve is output as an estimated respiratory waveform.

[0020]

[Effects of the Invention] Since the present invention estimates a respiratory waveform using the method described above, it produces the effects described below.

[0021] For one heartbeat, by using two angle data of the QRS vector and the T vector, the conventional method 2
Double the data can be obtained, improving the accuracy of the estimated respiratory waveform and making it possible to estimate even when the respiratory rate is faster than the heart rate.

[0022] Furthermore, the electrode position to be attached to the chest is determined based on the direction of the QRS vector obtained by measuring electrocardiograms from two types of leads that are at different angles to the heart vector, and measurements are taken at this electrode position. By estimating the respiratory waveform from the change in the size of the QRS wave of the electrocardiogram, only one channel of the electrocardiogram is required. Furthermore, since there is no need to attach electrodes to the limbs of the person to be measured, the burden on the person to be measured can be reduced.

[0023] Furthermore, the estimation accuracy can be improved by using the magnitude of the T wave as the estimation data for data of one channel of the chest lead electrocardiogram.

[0024] Furthermore, electrocardiograms are often recorded over a long period of time using a Holter electrocardiograph for testing and diagnosis, but if the present invention is applied, in addition to the conventional electrocardiogram analysis, There is an advantage that the estimated respiratory waveform can also be inspected and diagnosed.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram for determining the electrode attachment position.

FIG. 3 is a flowchart showing a second embodiment of the invention.

FIG. 4 is an explanatory diagram of the size of a QRS wave.

FIG. 5 is a flowchart showing a third embodiment of the present invention.

FIG. 6 is an explanatory diagram of how to obtain a QRS vector.

FIG. 7 is a hardware configuration diagram of a conventional respiration estimation method.

FIG. 8 is a flowchart showing a conventional respiration estimation method.

[Explanation of symbols]

11 Sample data of standard limb lead electrocardiogram 2 channels 12 Detection of each peak point of Q wave, R wave, and S wave 13
Detection of peak time of T wave 14 Calculation of angle of QRS vector 15 Calculation of angle of T vector 16 Converting both angle data of QRS vector and T vector into one data string 17 Data interpolation 18 Output of estimated respiratory waveform 21 QRS vector 23 Angle of change in QRS vector due to breathing 23
Projection axis 24 QRS size 25 Electrode 31 Electrocardiogram data measured at electrode positions determined based on the QRS vector 32 QRS wave peak detection 33 QRS wave size calculation 41 ECG baseline 42 Q wave area 43 R wave area 44 Area of S wave 51 Electrocardiogram data measured at the electrode position determined from QRS and T vector 52 Detection of T wave peak 53 Calculation of T wave size 54 Creation of interpolated data 61 Size of QRS wave in lead I electrocardiogram 62 Size of QRS wave in lead III electrocardiogram 71 Electrocardiogram amplifier 72 A/D converter 73 Computer 81 Moving average of 2-channel electrocardiogram data 82
QRS wave determination unit 83 QRS vector calculation unit 84 Cubic spline interpolation 85 Estimated respiratory waveform output

Claims (3)

[Claims] [Claim 1] 2 that make different angles with respect to the center vector
The method is characterized in that electrocardiograms from different types of leads are measured, a QRS vector is obtained from the QRS waves of the two types of electrocardiograms, and a T vector is obtained from the T waves of the two types of electrocardiograms, and a respiratory waveform is estimated using the angular change of each of the two vectors. A method for estimating respiratory waveforms using electrocardiograms. 2. Determine the direction of the QRS vector from the two types of electrocardiograms according to claim 1, determine the chest mounting position of the electrode based on the direction of the vector, and calculate the QRS of the 1-channel electrocardiogram measured at the electrode position. A method for estimating a respiratory waveform using an electrocardiogram, which is characterized by estimating a respiratory waveform based on the size of the wave. 3. The electrocardiogram according to claim 2, wherein the mounting position of the chest lead electrode is determined by taking into account the direction of the T vector, and the estimation of the respiratory waveform is also performed by taking into account the size of the T wave. The respiratory waveform estimation method used.