Heartbeat information acquisition system and bed system

Abstract

To provide a heart beat information acquisition system capable of easily and correctly acquiring heart beat information.SOLUTION: A heart beat information acquisition system for acquiring heart beat information of a subject on a bed includes: a plurality of load detectors for detecting a load of the subject on the bed; a waveform acquisition section for acquiring a plurality of heart beat waveforms respectively corresponding to the plurality of load detectors based on outputs of the plurality of load detectors; a waveform selection section for selecting the maximum amplitude waveform being the heart beat waveform with the largest amplitude among the plurality of heart beat waveforms among the plurality of heart beat waveforms; and a heart beat information acquisition section for acquiring heart beat information of the subject based on the output of the load detector corresponding to the maximum amplitude waveform among the plurality of load detectors.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a heartbeat information acquisition system and a bed system.

Background Art

[0002] In the fields of medical care and nursing care, it has been proposed to detect the load of a subject on a bed via a load detector and acquire biological information such as the respiration rate and heart rate of the subject based on the detected load.

[0003] Patent Document 1 discloses a biological information detection device including a plurality of detection units (for example, pressure sensors). The biological information detection device of Patent Document 1 includes an arithmetic unit that calculates, for signals from each of the plurality of detection units, a ratio (signal-to-noise ratio) between the intensity value of a signal due to the vibration of the living body to be detected and the intensity value of a signal other than the signal due to the vibration of the living body to be detected, and a selection unit that selects one or more detection units having a large signal-to-noise ratio, and detects vibrations due to respiration, heartbeat, body movement, etc. of the living body using the detection units selected by the selection unit.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a heartbeat information acquisition system and a bed system that can acquire heartbeat information more simply and accurately.

Means for Solving the Problems

[0006] According to a first aspect of the present invention, a heartbeat information acquisition system for acquiring heartbeat information of a subject on a bed, comprising A plurality of load detectors that detect the load of a subject on a bed, A waveform acquisition unit that acquires a plurality of heartbeat waveforms respectively corresponding to the plurality of load detectors based on the outputs of the plurality of load detectors; A waveform selection unit that selects a maximum amplitude waveform, which is the heartbeat waveform with the largest amplitude among the plurality of heartbeat waveforms, from the plurality of heartbeat waveforms; There is provided a heartbeat information acquisition system including a heartbeat information acquisition unit that acquires the heartbeat information of the subject based on the output of the load detector corresponding to the maximum amplitude waveform among the plurality of load detectors.

[0007] In the heartbeat information acquisition system according to the first aspect, the waveform selection unit may obtain an integrated value of amplitudes in a predetermined period for each of the plurality of heartbeat waveforms, and select, as the maximum amplitude waveform, the waveform having the largest integrated value among the plurality of heartbeat waveforms.

[0008] In the heartbeat information acquisition system according to the first aspect, the integrated value may be an integrated value of moving average values of each of the plurality of heartbeat waveforms.

[0009] In the heartbeat information acquisition system according to the first aspect, the waveform selection unit may use only positive values of the amplitudes of each of the plurality of heartbeat waveforms in calculating the integrated value of the amplitudes of each of the plurality of heartbeat waveforms.

[0010] The heartbeat information acquisition system according to the first aspect may further include a body movement determination unit that determines whether or not body movement has occurred in the subject based on at least one output of the plurality of load detectors.

[0011] In the heartbeat information acquisition system according to the first aspect, the waveform selection unit may not select the maximum amplitude waveform during a period in which the body movement determination unit determines that body movement has occurred in the subject.

[0012] In the heartbeat information acquisition system according to the first aspect, when the body movement determination unit determines that body movement has occurred in the subject, the waveform selection unit may reselect the maximum amplitude waveform after the body movement has ended.

[0013] In the heartbeat information acquisition system according to the first aspect, the waveform selection unit may select the maximum amplitude waveform at a predetermined period.

[0014] In the heartbeat information acquisition system according to the first aspect, the heartbeat information acquisition unit may calculate the heartbeat rate of the subject based on the autocorrelation of the maximum amplitude waveform.

[0015] In the heartbeat information acquisition system according to the first aspect, the heartbeat information acquisition unit may perform peak detection on the maximum amplitude waveform and calculate the heartbeat rate of the subject based on the detected peaks.

[0016] In the heartbeat information acquisition system according to the first aspect, the heartbeat information acquisition unit may calculate the heartbeat rate of the subject based on the frequency analysis of the output of the load detector corresponding to the maximum amplitude waveform.

[0017] According to a second aspect of the present invention, a bed, and a bed system including the heartbeat information acquisition system according to the first aspect are provided.

Advantages of the Invention

[0018] The heartbeat information acquisition system and the bed system of the present invention can acquire heartbeat information more simply and accurately.

Brief Description of the Drawings

[0019]

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DETAILED DESCRIPTION OF THE INVENTION

[0020] <Embodiment> Regarding the heartbeat information acquisition system 100 (FIG. 1) according to the embodiment of the present invention, a case where it is used together with the bed BD (FIG. 2) to calculate (estimate) the heart rate of the subject S on the bed BD will be described as an example.

[0021] As shown in FIG. 1, the heartbeat information acquisition system 100 of this embodiment mainly includes a load detection unit 1, a control unit 3, and a storage unit 4. The load detection unit 1 and the control unit 3 are connected via an A / D conversion unit 2. A display unit 5, a notification unit 6, and an input unit 7 are further connected to the control unit 3.

[0022] The load detection unit 1 includes four load detectors 11, 12, 13, and 14. Each of the load detectors 11, 12, 13, and 14 is a load detector that detects a load using, for example, a beam-shaped load cell. Such load detectors are described, for example, in Japanese Patent No. 4829020 and Japanese Patent No. 4002905. The load detectors 11, 12, 13, and 14 are each connected to the A / D conversion unit 2 by wiring or wirelessly.

[0023] As shown in FIG. 2, the four load detectors 11 to 14 of the load detection unit 1 are respectively disposed under casters C1, C2, C3, and C4 attached to the lower ends of the legs BL1, BL2, BL3, and BL4 at the four corners of the bed BD used by the subject S.

[0024] The A / D conversion unit 2 includes an A / D converter that converts an analog signal from the load detection unit 1 into a digital signal, and is connected to the load detection unit 1 and the control unit 3 by wiring or wirelessly.

[0025] The control unit 3 is a dedicated or general-purpose computer, and a body movement determination unit 31 and a heartbeat information acquisition unit 32 are constructed inside.

[0026] The storage unit 4 is a storage device that stores data used in the heartbeat information acquisition system 100, and for example, a hard disk (magnetic disk) can be used.

[0027] The display unit 5 is a monitor such as a liquid crystal monitor that displays information output from the control unit 3 to the user of the heartbeat information acquisition system 100.

[0028] The notification unit 6 includes a device that audibly performs a predetermined notification based on information from the control unit 3, for example, a speaker.

[0029] The input unit 7 is an interface for performing a predetermined input to the control unit 3 and can be a keyboard and a mouse.

[0030] The operation of acquiring the heartbeat information (heart rate in this embodiment) of the subject on the bed using such a heartbeat information acquisition system 100 will be described.

[0031] The acquisition of the subject's heartbeat information using the heartbeat information acquisition system 100 includes a load detection step S1, a body movement determination step S2, a heartbeat information acquisition step S3, and a display step S4 as shown in the flowchart of FIG. 3.

[0032] Generally, in the load detection step S1, the loads of the subject are detected using the load detectors 11 to 14. In the body movement determination step S2, the presence or absence of the subject's body movement is determined based on the load (load value) detected by at least one of the load detectors 11 to 14. In the heartbeat information acquisition step S3, the subject's heartbeat information is obtained using the load (load value) detected by the load detectors 11 to 14. In the display step S4, the obtained heartbeat information is displayed on the display unit 5.

[0033] [Load Detection Step] In the load detection step S1, the loads of the subject S on the bed BD are detected using the load detectors 11, 12, 13, and 14. The loads of the subject S on the bed BD are distributed and applied to the load detectors 11 to 14 arranged under the legs BL1 to BL4 at the four corners of the bed BD, and are detected dispersedly by these.

[0034] Load detectors 11 to 14 each detect a load (load change) and output it to the A / D conversion unit 2 as an analog signal. The A / D conversion unit 2 converts the analog signal into a digital signal with a sampling period of, for example, 5 milliseconds and outputs it to the control unit 3 as a digital signal (hereinafter referred to as "load signal"). Hereinafter, the load signals obtained by digitally converting the analog signals output from the load detectors 11, 12, 13, and 14 in the A / D conversion unit 2 are referred to as load signals s1, s2, s3, and s4, respectively.

[0035] [Body movement determination step] In the body movement determination step S2, the body movement determination unit 31 determines whether or not body movement has occurred in the subject S using at least one of the load signals s1 to s4.

[0036] Here, "body movement" means the movement of the subject's head, torso (trunk), and limbs. Movements of organs, blood vessels, etc. associated with breathing, heartbeat, etc. are not included in body movement. Body movement can be classified, for example, into large body movement accompanied by movement of the torso (trunk) of the subject S and small body movement accompanied only by movement of the subject's limbs and head. An example of large body movement is turning over or getting up, and an example of small body movement is movement of the hands, feet, or head during sleep.

[0037] The body movement determination unit 31 determines whether or not body movement has occurred in the subject S based on the following principle.

[0038] Fig. 4 shows a schematic waveform of the load signal s1 from the load detector 11 obtained during a predetermined period including times t0, t1, and t2.

[0039] During the period (period P1) from time t0 to time t1 within the predetermined period in which the waveform shown in Fig. 4 is obtained, no body movement has occurred in the subject S. Therefore, the load signal s1 during this period only vibrates slightly reflecting the movement of the subject's organs and blood vessels according to the breathing and heartbeat of the subject S, and the amount of variation is small. In other words, during the period P1 in which no body movement has occurred in the subject S, the variation in the sampling values of the load signal s1 is small.

[0040] On the other hand, during the predetermined period in which the waveform shown in FIG. 4 is obtained, body movement occurs in the subject S during the period from time t1 to time t2 (period P2). Specifically, the subject S is moving the right arm. Therefore, the load signal s1 during this period fluctuates greatly reflecting the movement of the right arm of the subject S. In other words, during the period P2 when body movement occurs in the subject S, the variation in the sampling values of the load signal s1 is large.

[0041] Thus, the variation in the sampling values of the load signal s1 from the load detector 11 becomes smaller during the period when no body movement occurs in the subject S, and becomes larger during the period when body movement occurs in the subject S. The same applies to the load signals s2, s3, and s4 from the load detectors 12, 13, and 14.

[0042] Therefore, the body movement determination unit 31 calculates the standard deviation σ representing the magnitude of the variation in the sampling values included in a predetermined period (for example, 5 seconds) for at least one of the load signals s1 to s4 from the load detectors 11 to 14, and based on the comparison between the calculated standard deviation σ and a predetermined threshold value σ th determines whether body movement has occurred in the subject S.

[0043] Specifically, for example, if the value of the standard deviation σ calculated for the predetermined period is smaller than the predetermined threshold value σ th it is determined that no body movement has occurred in the subject S during that period. On the other hand, if the value of the standard deviation σ calculated for the predetermined sampling period is larger than the predetermined threshold value σ th it is determined that body movement has occurred in the subject S during that period. Note that instead of the standard deviation σ, the variance σ 2 may be compared with a predetermined threshold value σ 2 th to determine the presence or absence of body movement of the subject S.

[0044] [Heartbeat information acquisition step] In the heartbeat information acquisition step S3, the heartbeat information acquisition unit 32 acquires the heartbeat information of the subject S using the load signals s1 to s4. The heartbeat information is the heart rate in this embodiment.

[0045] As shown in FIG. 5, the heartbeat information acquisition step S3 includes a heartbeat waveform acquisition step S31, a maximum amplitude waveform selection step S32, and a heart rate calculation step S33.

[0046] As shown in FIG. 6, the heartbeat information acquisition unit 32 includes a heartbeat waveform acquisition unit 321, a waveform selection unit 322, and a heart rate calculation unit 323. The waveform selection unit 322 includes a moving average integration unit 322a and a selection execution unit 322b.

[0047] In the heartbeat waveform acquisition step S31, the heartbeat waveform acquisition unit 321 acquires the heartbeat waveform of the subject S from each of the load signals s1 to s4.

[0048] In this specification and the present invention, the "heartbeat waveform" means a waveform showing the temporal variation of the load value corresponding to the heartbeat of the subject. One cycle of the heartbeat waveform corresponds to one cycle of the heartbeat. The amplitude of the heartbeat waveform has a correlation with the amount of blood flowing through one heartbeat. If other conditions are the same, the larger the amount of blood flowing through one heartbeat, the larger the amplitude of the heartbeat waveform.

[0049] Specifically, for example, the heartbeat waveform acquisition unit 321 acquires the heartbeat waveform by the following method.

[0050] Since the human heartbeat occurs about 30 to 200 times per minute, the frequency of the human heartbeat is about 0.5 to 3.3 Hz (hereinafter referred to as the "heartbeat band"). Therefore, the heartbeat waveform acquisition unit 321 extracts the components having the frequency of the heartbeat band from each of the load signals s1 to s4 by a band-pass filter, and sets the extracted components as the heartbeat waveforms HW1 to HW4.

[0051] Examples of the heartbeat waveforms HW1, HW2, HW3, and HW4 acquired based on the load signals s1, s2, s3, and s4 are shown in FIGS. 7(a), 7(b), 7(c), and 7(d), respectively. The heartbeat waveforms HW1 to HW4 shown in FIGS. 7(a) to 7(d) are the heartbeat waveforms of the subject S in the period from time 10 s to time 40 s.

[0052] In the maximum amplitude waveform selection step S32, the waveform selection unit 322 selects the waveform with the largest amplitude (hereinafter referred to as the "maximum amplitude waveform") from the four heartbeat waveforms HW1 to HW4 acquired in the heartbeat waveform acquisition step S31.

[0053] Specifically, for example, the waveform selection unit 32 selects the maximum amplitude waveform according to the following procedure.

[0054] (1) Clipping process First, the waveform selection unit 32 performs a clipping process on each of the heartbeat waveforms HW1 to HW4 to cut off the amplitude less than zero by the moving average integration unit 322a. The moving average integration unit 322a replaces the amplitude value less than zero with zero for each of the heartbeat waveforms HW1 to HW4.

[0055] The clipped waveforms HW1' to HW4' obtained by performing the clipping process on the heartbeat waveforms HW1 to HW4 shown in FIGS. 7(a) to 7(d) are as shown in FIGS. 8(a) to 8(d), respectively.

[0056] (2) Calculation of moving average value MA Next, the waveform selection unit 32 sequentially calculates the 10-second moving average value MA of the amplitudes of the clipped waveforms HW1' to HW4' by the moving average integration unit 332a.

[0057] FIG. 9(a) shows the state of sequentially calculating the 10-second moving average value of the amplitude of the clipped waveform HW1' based on the clipped waveform HW1' shown in FIG. 8(a).

[0058] Specifically, FIG. 9(a) shows the calculation with the denominator being "10" and the numerator being the integrated value of the amplitude of the clipped waveform HW1' within the period, and obtaining the moving average value MA = 1.3 in the period from time 10s to time 20s. Also, FIG. 9(b) shows the state of obtaining the moving average value MA = 1.3 in the period from time 20s to time 30s and the moving average value MA = 1.4 in the period from time 30s to time 40s by the same calculation.

[0059] Figure 9(b) performs the same calculation based on the clipped waveform HW2’ shown in Figure 8(b), and shows the state of obtaining the moving average value MA = 1.8 in the period from time 10s to time 20s, the moving average value MA = 1.8 in the period from time 20s to time 30s, and the moving average value MA = 1.8 in the period from time 30s to time 40s.

[0060] Figure 9(c) performs the same calculation based on the clipped waveform HW3’ shown in Figure 8(c), and shows the state of obtaining the moving average value MA = 1.2 in the period from time 10s to time 20s, the moving average value MA = 1.1 in the period from time 20s to time 30s, and the moving average value MA = 1.0 in the period from time 30s to time 40s.

[0061] Figure 9(d) performs the same calculation based on the clipped waveform HW4’ shown in Figure 8(d), and shows the state of obtaining the moving average value MA = 1.1 in the period from time 10s to time 20s, the moving average value MA = 1.1 in the period from time 20s to time 30s, and the moving average value MA = 1.2 in the period from time 30s to time 40s.

[0062] (3) Integration of the moving average value MA Next, the waveform selection unit 32 sequentially integrates the moving average value MA calculated every 10 seconds by the moving average integration unit 332a to obtain the moving average integration value MAI. And when the moving average value MA is integrated 6 times (for 60 seconds), the moving average integration value MAI at that time is used as the reference integration value MAI Ref and stored, and the moving average integration value MAI is reset.

[0063] Figures 10(a) to 10(d) respectively integrate the moving average value MA calculated every 10 seconds based on the clipped waveforms HW1’ to HW4’, and obtain the reference integration value MAI Ref at time 60s, time 120s, and time 180s. The state of obtaining is shown. The obtained reference integration value MAI Ref has the values as shown in each figure.

[0064] (4) Selection of the maximum amplitude waveform Next, the waveform selection unit 32 selects, by the selection execution unit 322b, one of the heartbeat waveforms HW1 to HW4 as the maximum amplitude waveform.

[0065] Specifically, the selection execution unit 322b compares four reference integrated values MAI Ref based on each of the immediately preceding heartbeat waveforms HW1 to HW4 every 60 seconds, and selects, as the maximum amplitude waveform, the waveform with the largest value of the reference integrated value MAI Ref .

[0066] Regarding the examples shown in FIGS. 7 to 10, at any of the times 60s, 120s, and 180s, the value of the reference integrated value MAI Ref based on the heartbeat waveform HW2 is larger than the values of the reference integrated values MAI Ref based on the heartbeat waveforms HW1, HW3, and HW4. Therefore, the selection execution unit 322b selects the heartbeat waveform HW2 as the maximum amplitude waveform immediately after 60s, immediately after 120s, and immediately after 180s.

[0067] In the heart rate calculation step S33, the heart rate calculation unit 323 calculates the heart rate of the subject S based on the maximum amplitude waveform selected in the maximum amplitude waveform selection step S32.

[0068] Specifically, for example, the heart rate calculation unit 323 calculates the heart rate of the subject S by the following method.

[0069] The heart rate calculation unit 323 calculates the autocorrelation value in the time domain for the heartbeat waveform selected as the maximum amplitude waveform among the heartbeat waveforms HW1 to HW4.

[0070] The calculated autocorrelation value indicates the degree of coincidence between the heartbeat waveform and the waveform obtained by shifting the heartbeat waveform by a lag (delay) L in the time axis direction. Since the degree of coincidence between a certain waveform and the waveform obtained by shifting the waveform by a lag L in the time axis direction is the highest when the lag L is equal to the period of the waveform, the value of the lag L corresponding to the peak of the autocorrelation value indicates the period of the heartbeat waveform.

[0071] Therefore, the heart rate calculation unit 323 detects the peak of the autocorrelation value and determines the lag L corresponding to the peak as the period of the heartbeat waveform.

[0072] In addition, when there are a plurality of peaks in the range corresponding to the period of the heartbeat (here, about 0.3 s < L < about 2.0 s), the heart rate calculation unit 323 determines the lag L corresponding to the higher peak as the period T of the heartbeat waveform.

[0073] Thereafter, the heart rate calculation unit 323 calculates the heart rate HR [bpm] using the following (Equation 1).

Equation

[0074] After the heartbeat information acquisition system 100 is activated, when the result of the body movement determination of the subject S by the body movement determination unit 31 becomes "no body movement", the moving average integration unit 322a starts calculating the moving average value MA and the moving average integration value MAI for each of the heartbeat waveforms HW1 to HW4. Then, every 60 seconds thereafter, the moving average integration unit 322a calculates the reference integration value MAI Ref of each of the heartbeat waveforms HW1 to HW4, and the selection execution unit 322b selects the maximum amplitude waveform.

[0075] Each time a new maximum amplitude waveform is selected, the heart rate calculation unit 323 switches to calculating the heart rate using the new maximum amplitude waveform.

[0076] After any one of the heartbeat waveforms HW1 to HW4 is selected as the maximum amplitude waveform at a certain time, the heart rate calculation unit 323 may calculate the heart rate based on the maximum amplitude waveform acquired after that time. In this case, the heart rate of the subject S can be calculated and displayed with higher accuracy. Alternatively, after any one of the heartbeat waveforms HW1 to HW4 is selected as the maximum amplitude waveform at a certain time, the heart rate calculation unit 323 may use the heartbeat waveform before that time (i.e., the reference integration value MAI RefThe calculation of the heart rate may be performed based on the heart rate waveform involved in the calculation. Also in this case, the heart rate of the subject S can be calculated with higher accuracy based on the waveform confirmed by calculation to be the maximum heart rate waveform.

[0077] The heart rate information acquisition unit 32, while periodically calculating the reference integrated value MAI Ref and selecting the maximum amplitude waveform (in this embodiment, every 60 seconds), when the determination result of the body movement determination unit 31 becomes "body movement present", the calculation of the moving average value MA by the moving average integration unit 322a is stopped, and the moving average integrated value MAI is reset. Also, the selection of the maximum selected waveform is canceled (that is, the designation as the maximum amplitude waveform for any one of the heart rate waveforms HW1 to HW4 is also canceled), and the calculation of the heart rate is also aborted.

[0078] This is because during the period when the subject S is experiencing body movement, the heart rate waveform is disturbed by the influence of the body movement, and it becomes difficult to perform the selection of the maximum amplitude waveform and the calculation of the heart rate with high accuracy.

[0079] The heart rate information acquisition unit 32 does not calculate the moving average value MA, the moving average integrated value MAI, and the heart rate during the period when the determination result of the body movement determination unit 31 is "body movement present". When the determination result of the body movement determination unit 31 returns to "no body movement" again, the heart rate information acquisition unit 32 starts calculating the moving average value MA and the moving average integrated value MAI by the moving average integration unit 322a again. The moving average integrated value MAI does not inherit the value before the body movement, but is newly integrated from zero. Then, when the reference integrated value MAI Ref is calculated about 60 seconds after the end of the body movement, the maximum amplitude waveform is selected, and the calculation of the heart rate using the selected maximum amplitude waveform is restarted.

[0080] When the position and posture of the subject S on the bed change according to the body movement of the subject S, the maximum amplitude waveform often switches to another waveform. Therefore, it is preferable to select the maximum amplitude waveform again triggered by the body movement of the subject S.

[0081] [Display step] In the engineering S4, the control unit 3 displays the calculation result of the heart rate calculation step S33 on the display unit 5. Further, in the display step S4, in addition to or instead of the display using the display unit 5, notification using the notification unit 6 may be performed. In this case, for example, when the heart rate of the subject S deviates from a predetermined range, a notification sound is emitted to notify a nurse or a caregiver who is a user of the heart rate information acquisition system 100 of the abnormality of the heart rate state.

[0082] The effects of the heart rate information acquisition system 100 of the present embodiment are summarized below.

[0083] The heart rate information acquisition system 100 of the present embodiment selects the maximum amplitude waveform, which is the waveform with the largest amplitude among the four heart rate waveforms HW1 to HW4 obtained from the four load detectors 11 to 14, and calculates the heart rate using the selected maximum amplitude waveform. In this way, by calculating the heart rate using a waveform with a large amplitude, the accuracy of the calculated heart rate can be improved.

[0084] Patent Document 1 discloses selecting a signal with a large signal-to-noise ratio from the detection signals of a plurality of detection units for use in subsequent processing. However, even if an output signal used for calculating the heart rate is selected based on the magnitude of the signal-to-noise ratio of the output signal from the load detector, it is not always possible to select an appropriate output signal. This is because for a load detector with little influence of noise, even if the amplitude of the heart rate waveform based on the output signal of the load detector is small, the signal-to-noise ratio becomes large.

[0085] On the other hand, the heart rate information acquisition system 100 of the present embodiment first acquires a heart rate waveform from the output of the load detector to remove noise to a certain extent, and then directly focuses on the amplitude of the heart rate waveform, which is a factor affecting the accuracy of heart rate calculation, to select the waveform used for heart rate calculation. Therefore, a heart rate waveform suitable for calculating the heart rate can be accurately selected, and the heart rate can be calculated with high accuracy.

[0086] In addition, the heartbeat information acquisition system 100 of the present embodiment has a smaller signal processing load required for waveform selection compared to the case of calculating the signal-to-noise ratio. Thus, the small signal processing load is particularly advantageous when implementing the heartbeat information acquisition system 100 as an embedded program of a microcomputer (microcontroller).

[0087] The heartbeat information acquisition system 100 of the present embodiment selects the maximum amplitude waveform based on the integrated value of the moving average values of the amplitudes of the heartbeat waveforms HW1 to HW4. By using the moving average value of the amplitude in this way, the influence of instantaneous fluctuations (i.e., noise) of the amplitude can be suppressed, and the selection of the maximum amplitude waveform can be performed more appropriately. Also, by using the integrated value of the amplitude, a minute difference in the amplitude can be enlarged, and the selection of the maximum amplitude waveform can be performed more appropriately.

[0088] The heartbeat information acquisition system 100 of the present embodiment includes a body movement determination unit 31, and the heartbeat information acquisition unit 32 stops the selection of the maximum amplitude waveform and the calculation of the heart rate during the period when the body movement determination unit 31 determines that the subject has body movement. Therefore, the influence of body movement is suppressed, and the reliability of the selected maximum amplitude waveform and the calculated heart rate is high.

[0089] The heartbeat information acquisition system 100 of the present embodiment reselects the maximum amplitude waveform periodically, and also reselects the maximum amplitude waveform after the body movement ends even when the subject S has body movement. Therefore, based on the sequentially selected maximum amplitude waveforms, highly accurate heart rate calculation can be continued.

[0090] <Modification Example> In the heartbeat information acquisition system 100 of the above embodiment, the following modification modes can also be adopted.

[0091] In the heartbeat information acquisition system 100 of the above embodiment, the waveform selection unit 322 calculates the 10-second moving average value MA of the amplitudes of the heartbeat waveforms HW1 to HW4, calculates the moving average integrated value MAI, and the reference integrated value MAI which is the integrated value of the moving average value MA for 60 seconds RefAlthough the maximum amplitude waveform is selected based on the calculation of , it is not limited to this.

[0092] The period for calculating the moving average value MA is not limited to 10 seconds and is arbitrary, and the reference integrated value MAI Ref is also not limited to 60 seconds and can be the integrated value of the moving average value MA over an arbitrary period.

[0093] The waveform selection unit 322 may select, as the maximum amplitude waveform, a heartbeat waveform in which the moving average value MA is the largest during a predetermined period without calculating the moving average integrated value MAI.

[0094] The waveform selection unit 322 may select, as the maximum amplitude waveform, a heartbeat waveform in which the integrated value of the amplitude during a predetermined period is the largest without calculating the moving average value MA.

[0095] The waveform selection unit 322 may select the maximum amplitude waveform based only on the magnitude relationship of one amplitude at a predetermined time. The amplitude of the heartbeat waveform can be obtained by identifying the peak of the heartbeat waveform through peak detection.

[0096] In the heartbeat information acquisition system 100 of the above embodiment, the waveform selection unit 322 performs clip processing prior to the calculation of the moving average value MA, but it is not limited to this.

[0097] It is not necessary to perform clip processing. Also, for example, instead of clip processing, a process of replacing the negative sign of the negative value of the amplitude with a positive sign may be performed. Alternatively, the heartbeat waveform may be shifted by a predetermined amount in the positive direction of the amplitude. By these processes, the calculation accuracy can be improved by calculating the moving average value MA using only positive values of the amplitude.

[0098] In the heartbeat information acquisition system 100 of the above embodiment, after the waveform selection unit 322 selects the maximum amplitude waveform, the heart rate is calculated using the selected maximum amplitude waveform, but it is not limited to this.

[0099] For example, the heart rate calculation unit 323 may always calculate the heart rate based on each of the heart rate waveforms HW1 to HW4 in advance, and after the waveform selection unit 322 selects the maximum selection waveform, the heart rate calculated in advance based on the selected maximum amplitude waveform (that is, any one of the heart rate waveforms HW1 to HW4) may be displayed on the display unit 5.

[0100] In the heart rate information acquisition system 100 of the above embodiment, the heart rate calculation unit 323 calculates the heart rate based on the calculation of the autocorrelation value, but it is not limited to this. Various methods can be used to calculate the heart rate based on the heart rate waveform.

[0101] Specifically, for example, peak detection is performed on the maximum amplitude waveform, and the period of the maximum amplitude waveform is specified based on the peak-to-peak distance. Then, the specified period is applied to the above (Equation 1) to calculate the heart rate HR [bpm].

[0102] The heart rate calculation unit 323 may perform peak detection on the maximum amplitude waveform for a certain period and calculate the heart rate HR [bpm] from the number of peaks.

[0103] The heart rate calculation unit 323 may calculate the heart rate of the subject S without using the heart rate waveform. Specifically, for example, after the maximum amplitude waveform is selected, Fourier analysis of the load signal from the load detector corresponding to the maximum amplitude waveform is performed to identify the peak frequency appearing in the heart rate band. Then, regarding the peak frequency as the frequency of the heart rate, the heart rate is calculated. Instead of Fourier analysis, other frequency analyses can also be used to calculate the heart rate.

[0104] In the heart rate information acquisition system 1000 of the above embodiment, the heart rate information acquisition unit 32 may include, in addition to the heart rate calculation unit 323, or instead of the heart rate calculation unit 323, a unit for acquiring desired heart rate information such as stroke volume.

[0105] The heart rate information acquisition system 1000 of the above embodiment may not have the body movement determination unit 31.

[0106] In the above description, the heartbeat information acquisition system 1000 was described as an independent system. However, the heartbeat information acquisition system 1000 may be a part of a biological state acquisition (monitoring) system that acquires (monitors) various biological information such as the respiration rate of a subject.

[0107] The heartbeat information acquisition system 100 of the above embodiment does not necessarily have to include all of the load detectors 11 to 14, and it may only include any plurality of them. Further, the load detectors do not necessarily have to be arranged at the four corners of the bed, and they can be arranged at any position so as to detect the load of the subject on the bed and its fluctuations. Further, the load detectors 11 to 14 are not limited to load sensors using beam type load cells, and for example, force sensors can also be used.

[0108] In the heartbeat information acquisition system 100 of the above embodiment, each of the load detectors 11 to 14 was arranged under the caster C attached to the lower end of the leg of the bed BD, but it is not limited to this. Each of the load detectors 11 to 14 may be provided between the four legs of the bed BD and the floor board of the bed BD, or may be provided between the upper leg and the lower leg if the four legs of the bed BD can be divided vertically. Further, the load detectors 11 to 14 may be combined with the bed BD integrally or detachably to constitute a bed system BDS including the bed BD and the biological information monitoring system 100 of this embodiment (FIG. 11).

[0109] In the heartbeat information acquisition system 100 of the above embodiment, a signal amplification unit that amplifies the load signal from the load detection unit 1 or a filtering unit that removes noise from the load signal may be provided between the load detection unit 1 and the A / D conversion unit 2.

[0110] In the heartbeat state monitoring system 100 of the above-described embodiment, the display unit 5 may include a simple visual display means such as a printer that prints and outputs information representing heartbeat information or a lamp that displays heartbeat information, instead of or in addition to the monitor. The notification unit 6 may include a vibration generation unit that performs notification by vibration, instead of or in addition to the speaker.

[0111] As long as the features of the present invention are maintained, the present invention is not limited to the above-described embodiment, and other forms conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

Industrial Applicability

[0112] According to the heartbeat information acquisition system of the present invention, the heartbeat information of the subject can be acquired more accurately, which can contribute to the improvement of the quality of medical care, nursing, etc.

Explanation of Signs

[0113] 1 Load detection unit, 11, 12, 13, 14 Load detectors, 2 A / D conversion unit, 3 Control unit, 31 Body movement determination unit, 32 Heartbeat information acquisition unit, 321 Heartbeat waveform acquisition unit, 322 Waveform selection unit, 322a Moving average integration unit, 322b Selection execution unit, 323 Heartbeat rate calculation unit, 4 Memory unit, 5 Display unit, 6 Notification unit, 7 Input unit, 100 Heartbeat information acquisition system, BD Bed, BDS Bed system

Claims

1. A heart rate information acquisition system for acquiring the heart rate information of a subject on a bed, comprising: a plurality of load detectors for detecting the load of the subject on the bed; a waveform acquisition unit for acquiring a plurality of heart rate waveforms respectively corresponding to the plurality of load detectors based on the outputs of the plurality of load detectors; a waveform selection unit for selecting a selected heart rate waveform from the plurality of heart rate waveforms; a heart rate information acquisition unit for acquiring the heart rate information of the subject based on the output of the load detector corresponding to the selected heart rate waveform among the plurality of load detectors, wherein the waveform selection unit obtains an integrated value of the amplitudes of each of the plurality of heart rate waveforms over a predetermined period, and selects, as the selected heart rate waveform, the waveform having the largest integrated value among the plurality of heart rate waveforms.

2. The heart rate information acquisition system according to claim 1, wherein the integrated value is an integrated value of the moving average values of each of the plurality of heart rate waveforms.

3. The heart rate information acquisition system according to claim 1 or 2, wherein the waveform selection unit uses only positive values of the amplitudes of each of the plurality of heart rate waveforms in calculating the integrated value of the amplitudes of each of the plurality of heart rate waveforms.

4. The heart rate information acquisition system according to any one of claims 1 to 3, further comprising a body movement determination unit for determining whether or not body movement has occurred in the subject based on at least one output of the plurality of load detectors.

5. The heart rate information acquisition system according to claim 4, wherein the waveform selection unit does not select the selected heart rate waveform during a period in which the body movement determination unit determines that body movement has occurred in the subject.

6. The heart rate information acquisition system according to claim 4 or 5, wherein when the body movement determination unit determines that body movement has occurred in the subject, the waveform selection unit reselects the selected heart rate waveform after the body movement has ended.

7. The heart rate information acquisition system according to any one of claims 1 to 6, wherein the waveform selection unit selects the selected heart rate waveform at a predetermined period.

8. The heart rate information acquisition system according to any one of claims 1 to 7, wherein the heart rate information acquisition unit calculates the heart rate of the subject based on the autocorrelation of the selected heart rate waveform.

9. The heart rate information acquisition system according to any one of claims 1 to 7, wherein the heart rate information acquisition unit performs peak detection on the selected heart rate waveform and calculates the heart rate of the subject based on the detected peak.

10. The heartbeat information acquisition system according to any one of claims 1 to 7, wherein the heartbeat information acquisition unit calculates the heartbeat rate of the subject based on frequency analysis of the output of the load detector corresponding to the selected heartbeat waveform.

11. A bed, A bed system comprising the heartbeat information acquisition system according to any one of claims 1 to 10.

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