JP3460419B2 - Derivation of reference value for heart rate signal test - Google Patents

Description

Those concerning the derivation how the reference values for [belongs Technical Field of the Invention The present invention relates to noise on the measured heartbeat signals to check whether or not riding Description of the Invention [0001] . 2. Description of the Related Art In many cases, when measuring a heartbeat signal and using the heartbeat information, only inaccurate information can be obtained due to electric noise, movement of a subject, or the like. For this reason, it is necessary to check whether noise is included in the measured heartbeat signal, but conventionally, it was measured using a reasonable upper limit and lower limit as a human heartbeat interval. He is only checking the validity of the heart rate signal. [0003] In addition, when a continuous heartbeat signal is required, although it is apparent that the measured heartbeat signal contains, for example, noise or is missing, noise is measured from the measured heartbeat signal. Make corrections to remove,
It is necessary to perform correction to compensate for the missing part of the heartbeat signal. As a reference value for the correction at this time, the average value of the heartbeat intervals has been conventionally used. [0004] However, it is difficult to say that an accurate inspection is performed in a system with a lot of noise only by checking the validity using the above upper limit value and lower limit value. Also, the correction of the heartbeat signal cannot cope with the case where noise is accidentally mixed in at a timing satisfying the condition of the human heartbeat interval. In addition,
There is a possibility that inaccurate information may be mixed in the creation of the reference value, and in the correction based on such a reference value, the corrected heartbeat signal will also be inaccurate. The present invention has been made in view of such a point, and an object of the present invention is to provide a method of deriving a reference value for a heartbeat signal test capable of deriving an appropriate value as a reference value for a heartbeat signal test. Ru near to provide. According to a method of deriving a reference value for a heartbeat signal test according to the present invention, a heartbeat signal whose variation in interval is within a predetermined% among predetermined heartbeat signals is determined. It is characterized in that the average value of the heartbeat signal intervals at the time of consecutive times or more is used as a reference value for the heartbeat signal test. By paying attention to the variation of the continuous heartbeat interval, if the variation does not fall within a predetermined range, even if the variation is within a range appropriate for the human heartbeat interval, the variation is canceled so as not to be reflected in the reference value. The present invention will be described in detail below.
FIG. 2 shows an example of a system configuration for implementing the reference value derivation method and the heartbeat signal correction method of the present invention. A physical change due to a heartbeat detected by the pickup 2 from the subject 1 is converted into an electric signal by the detection circuit 3, converted into a digital signal by the binarization circuit 4, and then input to the microcomputer (CPU) 5. .
The derivation method and the correction method are implemented by a method suitable for the CPU 5, and specific operations are performed in the CPU 5. Hereinafter, the derivation method and the correction method will be described assuming this system. It is assumed that the above system has a configuration of a system and a control program that recognizes a rising edge of a signal as a heartbeat. First, as to the derivation of the reference value, as shown in FIG. 1, the data detected in step 202 is used as interval data in step 203. Next, at step 204, the validity of the interval data is checked. This is to check whether the human heartbeat interval is normal, and as described in the conventional example, the upper limit (H-limit msec) and lower limit of the human heartbeat interval
(L-limit msec). It is considered that these two values slightly vary depending on the use of the system, the state of the subject of the system, and the like. If it is determined in step 204 that there is an abnormality, the accumulated number of detections is canceled and the next interval data is waited. If it is normal, it is checked in step 206 whether the variation of the interval is within ± R%. If the same person is in the same state, the range of the variation of the heartbeat interval must be much smaller than the normal range inspected in step 204, and it is determined that a continuous signal having a large variation is noise. can do. The threshold value R here also depends on the subject and the system and cannot be determined without any limitation, but a value of 20 to 30% can be suitably used. If it is determined in step 206 that there is an abnormality, the processing is performed in the same manner as in step 204, and if it is normal, 1 is added to the number of detected data (step 207). By repeating the above processing, if X consecutive normal interval data are detected, an average value thereof is obtained and set as a reference value. Regarding X at this time, if it is too small, the reliability of the value will be low, and if it is too large, it will take too much time to obtain the reference value. Therefore, about 3 to 10, preferably about 5 is appropriate. Next, a correction method for correcting the measured heartbeat signal using the reference value will be described. First, as for a false alarm such as a case where noise enters between the original heartbeat signals, as shown in FIG. 3, when the measured interval data of the heartbeat signals is smaller than A% of the reference value, it is determined to be abnormal. It is assumed that the rising edge obtained this time is canceled and is not detected. It is also determined that the previous rising edge is normal as the interval data, but there is a possibility of a slight shift back and forth, so cancel it, set the rising edge two times before as the last edge that can be trusted, and set the next edge Perform processing. Next, as shown in FIG. 4, when the interval data of the measured heartbeat signal is larger than B% of the reference value, as shown in FIG. Assuming that a signal to be detected during the rising edge of is not detected, the following signal is complemented. FIG. 5 shows a supplementary routine. In step 502, interval data that is considered to include a plurality of undetected signals in between is divided by a reference value. The obtained answer is converted into an integer by an appropriate method such as rounding in steps 503 and 504, and then 1 is subtracted. The value thus obtained is used as the number of signals to be complemented, and the number of complementary edges (heartbeat signals) is arranged in the interval data. In this arrangement, these are arranged at regular intervals. As the threshold values A and B for the above correction, values of A = 80% to 60% and B = 125% to 150% can be suitably used. Since the correction method depends on the system to be mounted, it cannot be determined unconditionally. For example, in a system in which the heartbeat interval is expected to be gradually widened (for example, a system that induces sleep), the value of B should be set to be large, and the value of A should be set to be small. Is added, more accurate correction can be performed. It is, of course, preferable to execute the correction for the false report and the unreported report in combination, and FIG. 6 shows a flow in this case. After the correction for the false report, the correction for the unreport is performed. It is possible to cancel interval data that is too short compared to the reference value and treat the data as interval data that has an interval that is too wide to perform complementation, thereby simplifying and speeding up the algorithm. The above system has been described as a real-time processing system as an example of description, but the present invention is not limited to this, and can be applied to a batch processing system. As described above, in the method of deriving a reference value for heartbeat signal inspection according to the present invention, since a variation range is set, it is possible to derive a more accurate reference value in a short time. I can . [0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart relating to derivation of a reference value according to the present invention. FIG. 2 is a system configuration diagram of the above system. FIG. 3 is a flowchart relating to correction for a false report. FIG. 4 is a flowchart relating to correction for unreported information. FIG. 5 is a flowchart for complementary correction. FIG. 6 is a flowchart relating to correction. [Description of Signs] 1 subject 2 pickup 3 detection circuit 4 binarization circuit 5 CPU

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-150050 (JP, A) JP-A-5-168604 (JP, A) JP-B-63-34731 (JP, B1) JP-T-60 Showa 60- 500753 (JP, A) WO 97/23254 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61B 5/0245

Claims (1)

(57) [Claims 1] The average value of the heartbeat signal intervals when the heartbeat signals whose variation in the interval is within a predetermined percentage among the measured heartbeat signals continues for a predetermined number of times or more is calculated as the heartbeat signal. A method for deriving a reference value for a heartbeat signal test, wherein the reference value is used as a reference value for a test.