Heart rate acquisition device and bed system

Abstract

A heart rate acquisition device (30) for acquiring the heart rate of a subject (S) on a bed (BD) is provided with: a heartbeat waveform acquisition unit (31) for acquiring, on the basis of the output of load detectors (11, 12, 13, 14) provided on the bed, a heartbeat waveform indicating the temporal variation of a load value corresponding to the heartbeat of the subject; a heartbeat cycle estimation unit (33) for obtaining an estimated value of the heartbeat cycle of the subject on the basis of the transition of the heartbeat waveform; and a heart rate calculation unit (34) that calculates the heart rate of the subject on the basis of the heartbeat waveform and the estimated value.

Description

Technical Field

[0001] The invention relates to a heart rate acquisition device and a bed system. Background Art

[0002] In the medical and nursing fields, a method has been proposed to detect the load of a subject on a bed via a load detector and obtain biological information such as the subject's respiratory rate and heart rate based on the detected load.

[0003] Patent Document 1 discloses a method of calculating an autocorrelation function of a heartbeat waveform acquired based on an output of a load detector, and calculating a heart rate of a subject based on a peak point of the autocorrelation function.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2022-72436 Summary of the invention

[0007] Problems to be solved by the invention

[0008] There is a demand for further improvement in accuracy and efficiency in the acquisition of biological information based on load detection.

[0009] One of the objects of the present invention is to provide a heart rate acquisition device and a bed system capable of acquiring heart rate with higher accuracy.

[0010] Another object of the present invention is to provide a heart rate acquisition device and a bed system that can acquire heart rate more efficiently.

[0011] Another object of the present invention is to provide a heart rate acquiring device and a bed system that can more appropriately display the acquired heart rate.

[0012] Solutions for solving problems

[0013] According to a first aspect of the present invention, there is provided a heart rate acquisition device for acquiring the heart rate of a subject lying on a bed, wherein the heart rate acquisition device comprises:

[0014] a heartbeat waveform acquisition unit that acquires a heartbeat waveform based on an output of a load detector provided on the bed, wherein the heartbeat waveform represents a temporal variation in a load value corresponding to a heartbeat of the subject;

[0015] a cardiac cycle estimating unit that obtains an estimated value of the cardiac cycle of the subject based on the transition of the cardiac waveform; and

[0016] The heart rate calculation unit calculates the heart rate of the subject based on the heartbeat waveform and the estimated value.

[0017] According to a second aspect of the present invention, there is provided a heart rate acquisition device for acquiring the heart rate of a subject lying on a bed, wherein the heart rate acquisition device comprises:

[0018] a heart rate calculation unit that calculates the heart rate of the subject based on a temporal change in an output of a load detector provided on the bed in accordance with a heartbeat of the subject;

[0019] A display unit that displays the heart rate calculated by the heart rate calculation unit; and

[0020] A display control unit controls the display content of the display unit,

[0021] The display control unit causes the display unit to display the heart rate calculated by the heart rate calculation unit in a different manner when the subject is on the bed and when the subject is not on the bed.

[0022] According to a third aspect of the present invention, there is provided a heart rate acquisition device for acquiring the heart rate of a subject lying on a bed, wherein the heart rate acquisition device comprises:

[0023] a heartbeat waveform acquisition unit that acquires a heartbeat waveform based on an output of a load detector provided on the bed, wherein the heartbeat waveform indicates a temporal change in a load value corresponding to a heartbeat of the subject; and

[0024] a heart rate calculation unit that calculates the heart rate of the subject based on the heartbeat waveform;

[0025] The calculation of the heart rate in the heart rate calculation unit includes:

[0026] Calculating the autocorrelation function of the heartbeat waveform;

[0027] detecting a peak point of the autocorrelation function; and

[0028] calculating the heart rate based on the detected position of the peak point,

[0029] The calculation of the autocorrelation function includes:

[0030] Calculating a first autocorrelation function of the heartbeat waveform included in the first period;

[0031] Calculating a second autocorrelation function of the heartbeat waveform included in a second period after the first period;

[0032] calculating a third autocorrelation function of the heartbeat waveform included in a third period after the second period;

[0033] Calculate the sum of the first autocorrelation function and the second autocorrelation function at a first moment as the autocorrelation function; and

[0034] At a second time after the first time, a sum of the second autocorrelation function and the third autocorrelation function is calculated as the autocorrelation function.

[0035] According to a fourth aspect of the present invention, there is provided a bed system comprising:

[0036] bed;

[0037] a load detector, disposed on the bed; and

[0038] The heart rate acquisition device of the first, second or third embodiment.

[0039] Effects of the Invention

[0040] The heart rate acquisition device and bed system of the present invention can acquire the heart rate with higher accuracy.

[0041] The heart rate acquisition device and bed system of the present invention can acquire the heart rate more efficiently.

[0042] The heart rate acquisition device and bed system of the present invention can more appropriately display the acquired heart rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a block diagram showing the structure of a biological information acquiring device according to an embodiment of the present invention.

[0044] Figure 2 It is an explanatory diagram showing the arrangement of the load detector with respect to the bed.

[0045] Figure 3 This is a flowchart showing the procedure of acquiring the heart rate of a subject using a biological information acquiring device.

[0046] Figure 4 In the figures, (a), (b), (c), and (d) are graphs showing examples of heartbeat waveforms obtained based on outputs from four load detectors disposed under the bed legs.

[0047] Figure 5 This is a flowchart showing the details of the cardiac cycle estimation step.

[0048] Figure 6 This is a graph showing an example of a heartbeat waveform together with a valley point, a rising zero-crossing point, a peak point, and a falling zero-crossing point of the heartbeat waveform.

[0049] Figure 7 This is a table for explaining the tracking of the heartbeat waveform in the heartbeat cycle estimation step, and mainly shows the relationship between the state of the heartbeat waveform and the state transition variable.

[0050] Figure 8Among them, (a), (b), and (c) are explanatory diagrams for explaining the significance of the heart rate calculation unit decomposing and calculating the autocorrelation function of the heartbeat waveform, wherein (a) is a diagram for explaining the situation where a part of the autocorrelation function of the heartbeat waveform is calculated at time t, (b) is a diagram for explaining the situation where a part of the autocorrelation function of the heartbeat waveform is calculated at time t+0.5, and (c) is a diagram for explaining the situation where a part of the autocorrelation function of the heartbeat waveform is calculated at time t+1.0.

[0051] Fig. 9 This is a flowchart showing the details of the heart rate calculation procedure.

[0052] Fig.10 In the figure, (a) to (h) are explanatory diagrams for illustrating the calculation process of the autocorrelation function in the heart rate calculation unit, wherein (a) represents an example of a heartbeat waveform together with the sampling values ​​of the heartbeat waveform, and (b) to (h) are explanatory diagrams respectively representing the contents of the sampling values ​​stored in an array provided in a specified area of ​​the storage unit in the calculation step of the autocorrelation function.

[0053] Fig.11 In the figure, (a) and (b) are explanatory diagrams for explaining the interpolation processing performed in the heart rate calculation step, wherein (a) is a graph showing data points around the peak point of the autocorrelation function detected by peak point detection, and (b) is a graph showing a quadratic curve calculated based on the data points of (a) and the peak point of the quadratic curve.

[0054] Fig.12 In the figure, (a) and (b) respectively represent schemes for displaying the respiratory rate and the heart rate in the display unit, wherein (a) represents a state in which the respiratory rate and the heart rate are displayed in the display unit, and (b) represents a state in which the respiratory rate and the heart rate are not displayed in the display unit. DETAILED DESCRIPTION

[0055] <Implementation Method>

[0056] A biological information acquisition system 100 ( Figure 1 ) to integrate the system with the bed BD ( Figure 2 ) are used together to calculate (estimate) the heart rate of the subject S on the bed BD.

[0057] [Structure of Biological Information Acquisition System 100]

[0058] like Figure 1As shown, the biological information acquisition system 100 of this embodiment mainly includes a load detection unit 10, a biological information acquisition unit (heart rate acquisition device) 30, and a user terminal 40. The load detection unit 10 and the biological information acquisition unit 30 are connected via an A / D conversion unit 20. The biological information acquisition unit 30 and the user terminal 40 are connected by wire or wirelessly.

[0059] The load detection unit 10 includes four load detectors 11, 12, 13, and 14. The load detectors 11, 12, 13, and 14 are load detectors that detect loads using, for example, beam-shaped load cells. The load detectors 11, 12, 13, and 14 are connected to the A / D converter 20 by wire or wirelessly.

[0060] like Figure 2 As shown, four load detectors 11 to 14 are respectively arranged on casters C 1 , C 2 , C 3 , C 4 Below, caster C 1 , C 2 , C 3 , C 4 Legs BL attached to the four corners of the bed BD used by the subject S 1 BL 2 BL 3 BL 4 The lower end of .

[0061] The A / D conversion section 20 is connected to the load detection section 10 and the biological information acquisition section 30 by wire or wirelessly. The A / D conversion section 20 includes an A / D converter that converts an analog signal input from the load detection section 10 into a digital signal.

[0062] The biological information acquisition unit 30 mainly includes a heartbeat waveform acquisition unit 31, a body movement determination unit 32, a heartbeat cycle estimation unit 33, a heart rate calculation unit 34, and a storage unit 35. As an example, the heartbeat waveform acquisition unit 31, the body movement determination unit 32, the heartbeat cycle estimation unit 33, and the heart rate calculation unit 34 are constructed inside a control unit (controller) not shown in the figure that the biological information acquisition unit 30 has. The operation of the heartbeat waveform acquisition unit 31, the body movement determination unit 32, the heartbeat cycle estimation unit 33, and the heart rate calculation unit 34 will be described later.

[0063] The storage unit 35 is a storage device that stores data used in the biological information acquisition unit 30. As an example, the storage unit 35 can be a hard disk, a nonvolatile memory, or the like.

[0064] The user terminal 40 includes a display control unit 41 , a display unit 42 , a notification unit 43 , an input unit 44 , and a storage unit 45 .

[0065] As an example, the display control unit 41 is constructed inside a control unit (controller) not shown in the figure provided in the user terminal 40. The display control unit 41 obtains various information such as the heart rate acquired by the biological information acquisition unit 30 from the biological information acquisition unit 30, and displays it on the display unit 42 (details will be described later).

[0066] The display unit 42 visually displays the information such as the heart rate acquired from the biological information acquisition unit 30 to the user of the biological information acquisition system 100. For example, a monitor such as a liquid crystal monitor can be used as the display unit 42.

[0067] The notification unit 43 performs a predetermined notification in an auditory manner based on the information such as the heart rate acquired from the biological information acquisition unit 30. For example, a speaker may be used as the notification unit 43. The display control unit 41 may also control the operation of the notification unit 43.

[0068] The input unit 44 is an interface for inputting information to the biological information acquiring system 100. The input unit 44 can be, for example, a keyboard and a mouse.

[0069] The storage unit 45 is a storage device that stores data used in the user terminal 40. As an example, the storage unit 45 can be a hard disk, a nonvolatile memory, or the like.

[0070] [Operation of the Biological Information Acquisition System 100]

[0071] An operation of acquiring the heart rate of a subject lying on a bed using the biological information acquiring system 100 having such a configuration will be described.

[0072] like Figure 3 As shown in the flowchart, the acquisition of the heart rate of the subject S using the biological information acquisition system 100 includes a load detection step S1, a heartbeat waveform acquisition step S2, a body movement determination step S3, a heartbeat cycle estimation step S4, a heart rate calculation step S5 and a display step S6.

[0073] Generally speaking, in the load detection step S1, the load of the subject S is detected using the load detectors 11 to 14. In the heartbeat waveform acquisition step S2, the heartbeat waveform is extracted by filtering based on the temporal changes in the detection values ​​of the load detectors 11 to 14. In the body movement determination step S3, the presence or absence of body movement of the subject S is determined based on the amplitude of the heartbeat waveform. In the heartbeat cycle estimation step S4, the heartbeat cycle of the subject S is estimated based on the heartbeat waveform. In the heart rate calculation step S5, the heart rate of the subject S is calculated based on the heartbeat waveform, the presence or absence of body movement, and the estimated value of the heartbeat cycle. In the display step S6, the calculated heart rate is displayed on the display unit 42.

[0074] [Load detection step S1]

[0075] In the load detection step S1, the load of the subject S on the bed BD is detected using the load detectors 11, 12, 13, and 14. The load of the subject S on the bed BD is distributedly applied to the legs BL disposed at the four corners of the bed BD. 1 ~BL 4 The load detectors 11 to 14 at the lower side detect the loads in a distributed manner by these load detectors.

[0076] The load detectors 11 to 14 detect the load (load change) and output it in the form of an analog signal to the A / D conversion unit 20. The A / D conversion unit 20 converts the analog signal into a digital signal with a sampling period of, for example, 5 milliseconds (0.005 seconds) and outputs it in the form of a digital signal (hereinafter referred to as a "load signal") to the biological information acquisition unit 30. 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 20 are respectively referred to as load signals s 1 、s 2 、s 3 、s 4 .

[0077] [Heartbeat waveform acquisition step S2]

[0078] In the heartbeat waveform acquisition step S2, the heartbeat waveform acquisition unit 31 obtains the heartbeat waveform from each load signal s 1 ~s 4 The heartbeat waveform of the subject S is obtained.

[0079] In this specification and the present invention, a "heartbeat waveform" refers to a waveform that represents the temporal variation of a load value corresponding to the heartbeat of a subject. One cycle of a heartbeat waveform corresponds to one cycle of a heartbeat. The amplitude of a heartbeat waveform is correlated with the amount of blood flowing through one beat. If other conditions are the same, the greater the amount of blood flowing through a beat, the greater the amplitude of the heartbeat waveform.

[0080] Specifically, the heartbeat waveform acquisition unit 31 acquires the heartbeat waveform by, for example, the following method.

[0081] Since the human heart beats about 40 to 150 times per minute, the frequency of the human heart beats is about 0.66 Hz to 2.5 Hz (hereinafter referred to as the "heartbeat frequency band"). Therefore, the heartbeat waveform acquisition unit 31 obtains the load signal s through a bandpass filter. 1 ~s 4 Components having frequencies in the heartbeat frequency band are extracted respectively, and the extracted components are set as heartbeat waveforms HW1 to HW4.

[0082] From the load signal s 1 The extracted heartbeat waveform HW1 and the load signal s 2 The extracted heartbeat waveform HW2 and the load signal s 3 The extracted heartbeat waveform HW3 and the load signal s 4 An example of the extracted heartbeat waveform HW4 is shown in Figure 4 (a) Figure 4 (b) Figure 4 (c) Figure 4 (d). Figure 4 (a)~ Figure 4 The heartbeat waveforms HW1 to HW4 shown in (d) are heartbeat waveforms of the subject S in the same period (time 0 s to time 30 s).

[0083] In addition, the heartbeat waveform acquisition unit 31 downsamples the acquired heartbeat waveforms HW1 to HW4 to reduce the processing load. In this embodiment, the sampling frequency is converted to a sampling period of 5 milliseconds (0.005 seconds) to 10 milliseconds (0.01 seconds). It should be noted that downsampling may not be performed.

[0084] [Body Movement Determination Step S3]

[0085] In the body movement determination step S3 , the body movement determination unit 32 determines whether the subject S has had body movement based on a comparison between the amplitude AM of the heartbeat waveforms HW1 to HW4 and a threshold value.

[0086] Here, in the present invention and this specification, "body movement" refers to the movement of the subject's head, trunk, and limbs. The movement of organs, blood vessels, etc. caused by breathing, heartbeat, etc. is not included in body movement. As an example, body movement can be classified into large body movement accompanied by the movement of the subject's trunk (trunk) and small body movement accompanied only by the movement of the subject's limbs and head. An example of large body movement is turning over, getting up, etc., and an example of small body movement is the movement of hands, feet, and head during sleep, etc.

[0087] The body movement determination unit 32 determines the presence or absence of body movement based on the comparison between the amplitude AW of the heartbeat waveforms HW1 to HW4 and the threshold value. Specifically, for example, when the amplitude AW of at least one of the heartbeat waveforms HW1 to HW4 is greater than the body movement threshold value THp on the positive side, or when the amplitude AW of at least one of the heartbeat waveforms HW1 to HW4 is less than the body movement threshold value THn on the negative side, it is determined that the subject S has body movement.

[0088] The body movement thresholds THp and THn can be set arbitrarily. Specifically, for example, the magnitude of the past amplitude AM of the heartbeat waveforms HW1 to HW4 can be considered, and appropriate values ​​can be set to indicate that the subject S has had body movement when the amplitude AM (positive value) is greater than the positive threshold, and appropriate values ​​can be set to indicate that the subject S has had body movement when the amplitude AM (negative value) is less than the negative threshold. It is also possible to use only positive thresholds and indicate that the subject S has had body movement when the absolute value of the amplitude AM is greater than the threshold.

[0089] The body movement determination unit 32 sets a body movement occurrence flag while determining that the subject S has had body movement. The body movement occurrence flag is set in a predetermined area reserved in the storage unit 35, for example.

[0090] [Heartbeat cycle estimation step S4]

[0091] In the heartbeat cycle estimating step S4 , the heartbeat cycle estimating unit 33 estimates the heartbeat cycle of the subject S based on the heartbeat waveforms HW1 to HW4 .

[0092] As described above, one cycle of a heartbeat waveform corresponds to one cycle of a heartbeat. Therefore, the heartbeat cycle estimation unit 33 tracks the transition of at least one of the heartbeat waveforms HW1 to HW4 to obtain the interval (length) of one cycle of the heartbeat waveform, thereby estimating the heartbeat cycle of the subject S.

[0093] Specifically, the heartbeat cycle estimation unit 33 performs, for example, Figure 5 The heartbeat cycle of the subject S is estimated by the process shown in the flowchart of Figure 6 ) is used as an example to estimate the heartbeat cycle of the subject S.

[0094] In the cardiac cycle estimation step S4, the cardiac cycle estimation unit 33 always performs the waveform transition tracking step S41. In the waveform transition tracking step S41, the cardiac cycle estimation unit 33 tracks the transition of the cardiac waveform HW1 based on the sign of the slope of the cardiac waveform HW1, the sign of the cardiac waveform HW1, and the state transition variable WS ( Figure 7 ).

[0095] Specifically, the cardiac cycle estimation unit 33 sequentially determines the valley point b of the cardiac waveform HW1, the zero-crossing point rx at the rising edge of the cardiac waveform HW1 (hereinafter referred to as the “rising zero-crossing point rx”), the peak point p of the cardiac waveform HW1, and the zero-crossing point fx at the falling edge of the cardiac waveform HW1 (hereinafter referred to as the “falling zero-crossing point fx”).

[0096] Here, the state transition variable WS is a variable indicating the state of the heartbeat waveform HW1. When the state transition variable WS is "1", the heartbeat waveform HW1 is in a state of moving from the valley point b to the rising zero-crossing point rx. When the state transition variable WS is "2", the heartbeat waveform HW1 is in a state of moving from the rising zero-crossing point rx to the peak point p. When the state transition variable WS is "3", the heartbeat waveform HW1 is in a state of moving from the peak point p to the falling zero-crossing point fx. When the state transition variable WS is "4", the heartbeat waveform HW1 is in a state of moving from the falling zero-crossing point fx to the valley point b.

[0097] Specifically, the heartbeat cycle estimation unit 33 determines the valley point b, the rising zero-crossing point rx, the peak point p, and the falling zero-crossing point fx, for example, in the following manner. Here, the case of determining the nth valley point b, i.e., the valley point b(n), the nth rising zero-crossing point, i.e., the rising zero-crossing point rx(n), the nth peak point p, i.e., the peak point p(n), and the nth falling zero-crossing point fx, i.e., the falling zero-crossing point fx(n) is described as an example.

[0098] (1) Determination of valley point b

[0099] like Figure 6 , Figure 7 As shown, at a certain time point, the state transition variable WS is "4", the sign of the slope of the heartbeat waveform HW1 changes from negative to positive, and the amplitude AM of the heartbeat waveform HW1 at this time point is smaller than the threshold TH b(n) (valley amplitude threshold), the cardiac cycle estimation unit 33 determines that there is a valley b(n) of the cardiac waveform HW1 at that time point. As an example, the threshold TH b(n) It can be set to the amplitude AM of the respiratory waveform HW1 at the valley point b(n-1) determined one cycle ago b(n－1) one third of.

[0100] When the valley point b(n) is identified, the cardiac cycle estimating unit 33 calculates the amplitude AM of the cardiac waveform HW1 at the valley point b(n) as b(n) The state transition variable WS is stored in the storage unit 35. In addition, the state transition variable WS is changed from "4" to "1". When the state transition variable WS is "1", the cardiac cycle estimation unit 33 waits for the arrival of the rising zero-crossing point rx.

[0101] (2) Determination of the rising zero crossing point rx

[0102] When the state transition variable WS is "1" and the sign of the heartbeat waveform HW1 changes from negative to positive at a certain time point, the heartbeat cycle estimation unit 33 determines that the rising zero-crossing point rx(n) exists at that time point.

[0103] When the rising zero-crossing point rx(n) is identified, the cardiac cycle estimation unit 33 changes the state transition variable WS from "1" to "2." When the state transition variable WS is "2," the cardiac cycle estimation unit 33 waits for the peak point p to arrive.

[0104] (3) Determination of peak point p

[0105] At a certain time point, the state transition variable WS is "2", the sign of the slope of the heartbeat waveform HW1 changes from positive to negative, and the amplitude AM of the heartbeat waveform HW1 at this time point is greater than the threshold value TH p(n) (peak amplitude threshold), the cardiac cycle estimation unit 33 determines that the peak point p(n) of the cardiac waveform HW1 exists at this time point. As an example, the threshold TH p(n) It can be set to the amplitude AM of the respiratory waveform HW1 at the peak point p(n-1) determined one cycle ago p(n－1) one third of.

[0106] When the peak point p(n) is identified, the cardiac cycle estimating unit 33 calculates the amplitude AM of the cardiac waveform HW1 at the peak point p(n) p(n) The state transition variable WS is stored in the storage unit 35. In addition, the state transition variable WS is changed from "2" to "3". When the state transition variable WS is "3", the cardiac cycle estimation unit 33 waits for the arrival of the falling zero-crossing point fx.

[0107] (4) Determination of the falling zero-crossing point fx

[0108] When the state transition variable WS is "3" and the sign of the heartbeat waveform HW1 changes from positive to negative at a certain time point, the heartbeat cycle estimation unit 33 determines that the falling zero-crossing point fx(n) exists at that time point.

[0109] When the falling zero-crossing point fx(n) is identified, the cardiac cycle estimation unit 33 changes the state transition variable WS from "3" to "4." When the state transition variable WS is "4," the cardiac cycle estimation unit 33 waits for the arrival of the valley point b.

[0110] The cardiac cycle estimating unit 33 executes step S42 in parallel with the waveform transition tracking step S41 to determine whether the determination of the falling zero-crossing point fx in the waveform transition tracking step S41 has been completed.

[0111] If it is determined that the falling zero-crossing point fx has not been identified (S42: No), the cardiac cycle estimation unit 33 executes step S42 again. If it is determined that the falling zero-crossing point fx has been identified (S42: Yes), the cardiac cycle estimation unit 33 proceeds to step S43.

[0112] In step S43 , the cardiac cycle estimation unit 33 determines whether or not the cardiac waveform HW1 satisfies a predetermined condition in the cycle before the identified zero-crossing point fx.

[0113] Specifically, the heartbeat cycle estimation unit 33 determines whether the amplitude AM (positive value) at the peak point p determined in the previous cycle is less than the body movement threshold value THp and whether the amplitude AM (negative value) at the valley point b determined in the previous cycle is greater than the body movement threshold value THn. The peak point p and valley point b determined in the previous cycle are, for example, p(n) and b(n) at the timing of determining the falling zero crossing point fx(n). The body movement threshold values ​​THp and THn may be the same values ​​as the body movement threshold values ​​THp and THn used in the body movement determination step S3.

[0114] The heartbeat cycle estimation unit 33 determines whether the interval PR of the previous cycle is within a predetermined range. The interval PR of the previous cycle is, for example, the length (time) from the falling zero crossing point fx(n-1) to the falling zero crossing point fx(n) when the timing of the falling zero crossing point fx(n) is determined.

[0115] When the amplitude AM (positive value) at the peak point p determined in the previous cycle is greater than the body movement threshold THp and / or the amplitude AM (negative value) at the valley point b determined in the previous cycle is less than the body movement threshold THn, or when the interval PR of the previous cycle is not within the prescribed range (S43: No), the heartbeat cycle estimation unit 33 returns to step S42.

[0116] When the amplitude AM (positive value) at the peak point p determined in the previous cycle is less than the body movement threshold value THp, the amplitude AM (negative value) at the valley point b determined in the previous cycle is greater than the body movement threshold value THn, and the interval PR of the previous cycle is within the prescribed range (S43: Yes), the cardiac cycle estimation unit 33 proceeds to step S44. Specifically, for example, when the interval PR of the previous cycle is greater than the prescribed value, the cardiac cycle estimation unit 33 determines that the PR is within the prescribed range.

[0117] In step S44, the heartbeat cycle estimation unit 33 determines whether the change ratio of the interval PR of the previous cycle to the interval PR of the cycle before this cycle is within a predetermined range. It should be noted that, when the interval PR of the previous cycle is the length (time) from the falling zero crossing point fx(n-1) to the falling zero crossing point fx(n), the interval PR of the cycle before this cycle is the length (time) from the falling zero crossing point fx(n-2) to the falling zero crossing point fx(n-1).

[0118] Specifically, for example, when the variation ratio of the interval PR of the previous cycle relative to the interval PR of the cycle immediately before the current cycle is greater than 50% and less than 200% (i.e., when the interval PR of the previous cycle is greater than 1 / 2 and less than 2 times the interval PR of the cycle immediately before the current cycle), the heartbeat cycle estimation unit 33 determines that the variation ratio of the interval PR of the previous cycle relative to the interval PR of the cycle immediately before the current cycle is within a prescribed range.

[0119] If it is determined that the variation ratio of the interval PR of the previous cycle relative to the interval PR of the cycle immediately before the cycle is not within the prescribed range (S44: No), the cardiac cycle estimation unit 33 returns to step S42. If the variation ratio of the interval PR of the previous cycle relative to the interval PR of the cycle immediately before the cycle is within the prescribed range (S44: Yes), the cardiac cycle estimation unit 33 proceeds to step S45.

[0120] In step S45, the heartbeat cycle estimation unit 33 stores the interval PR of the previous cycle in a predetermined area of ​​the storage unit 35. At this time, if the interval PR of eight cycles is already stored in the area, the interval PR of the earliest cycle is deleted. That is, the storage unit 35 is stored in a FIFO (first in first out) manner.

[0121] In step S46, the cardiac cycle estimation unit 33 determines whether the interval PR of eight cycles is stored in the predetermined area of ​​the storage unit 35. When the interval RP of eight cycles is stored in the predetermined area of ​​the storage unit 35 (S46: Yes), the cardiac cycle estimation unit 33 outputs the median of the PR of eight cycles as the estimated value of the cardiac cycle of the subject S to the heart rate calculation unit 34 (step S47). When the period RP of eight cycles is not stored in the predetermined area of ​​the storage unit 35 (S46: No), the cardiac cycle estimation unit 33 returns to step S42.

[0122] [Heart rate calculation step S5]

[0123] In the heart rate calculation step S5, the heart rate calculation unit 34 calculates (estimates) the heart rate of the subject S based on the temporal variation of the heartbeat waveforms HW1 to HW4, the estimated value of the heartbeat cycle estimated in the heartbeat cycle estimation step S4, and whether the subject S has body movement.

[0124] The heart rate calculation section 34 calculates the heart rate of the subject S roughly based on the following principle.

[0125] First, the heart rate calculation unit 34 calculates the autocorrelation function (autocorrelation coefficient) in the time domain for each of the heartbeat waveforms HW1 to HW4 .

[0126] The calculated autocorrelation function uses the delay time as a variable to represent the degree of agreement between the heartbeat waveforms HW1 to HW4 and the waveforms obtained by shifting the heartbeat waveforms in the time axis direction by a predetermined delay time. For a certain waveform having periodicity and the waveform obtained by shifting the waveform in the time axis direction by a delay time, the degree of agreement between the two is the highest when the delay time is equal to the period of the waveform. Therefore, the value of the delay time at which the autocorrelation function shows a peak represents the period of each of the heartbeat waveforms HW1 to HW4.

[0127] In view of the above, the heart rate calculation unit 34 detects the peaks of the autocorrelation functions of the heartbeat waveforms HW1 to HW4, identifies the delay time corresponding to the detected peaks as the cycle of the heartbeat waveform, and calculates the estimated value of the heart rate of the subject S based on the identified cycle.

[0128] It should be noted that, in the present embodiment, the heart rate calculation unit 34 calculates the autocorrelation function within a calculation window of 1.65 seconds. That is, the autocorrelation function within the delay time range of 0 seconds to 1.65 seconds is calculated. The human heart rate is usually at least about 40 [beats / minute], and the period of the heartbeat waveform is at most about 1.5 seconds. Therefore, by calculating the autocorrelation function within the calculation window of 1.65 seconds, the period of the heartbeat waveform can be accurately obtained, and the increase in the amount of calculation processing can be suppressed.

[0129] In addition, in the present embodiment, the heart rate calculation unit 34 suppresses an increase in the amount of calculation processing by performing calculations by decomposing the autocorrelation function. Figure 8 (a)~ Figure 8 (c) is used to illustrate the concept.

[0130] Set to Figure 8 In the state shown in (a), the autocorrelation function ACF(t) of the waveform w(t) at 0.5 seconds past time t and the waveform W(t) at 1.65 seconds past time t is calculated. Figure 8 Under the condition shown in (b), the autocorrelation function ACF(t+0.5) of the waveform w(t+0.5) at 0.5 seconds past the time t+0.5 and the waveform W(t+0.5) at 1.65 seconds past the time t+0.5 is calculated. Figure 8 In the state shown in (c), the autocorrelation function ACF(t+1.0) of the waveform w(t+1.0) 0.5 seconds past the time t+1.0 and the waveform W(t+1.0) 1.65 seconds past the time t+1.0 is calculated.

[0131] Here, in Figure 8In the state shown in (c), consider calculating the autocorrelation function of the waveform 1.5 seconds past the time t+1.0 and the waveform W(t+1.0) 1.65 seconds past the time t+1.0. In this case, if we can Figure 8 (a)~ Figure 8 As can be read from (c), the calculated autocorrelation function is equal to the autocorrelation function obtained by adding the autocorrelation function ACF(t), the autocorrelation function ACF(t+0.5) and the autocorrelation function ACF(t+1.0).

[0132] That is, in Figure 8 In the state shown in (c), when calculating the autocorrelation function of the waveform 1.5 seconds past the time t+1.0 within the calculation window of 1.65 seconds, if the autocorrelation function of the waveform 1.5 seconds past the time t+1.0 and the waveform W(t+1.0) 1.65 seconds past the time t+1.0 are calculated, the amount of calculation will increase. In contrast, by calculating the autocorrelation function ACF(t+1.0) of the waveform w(t+1.0) 0.5 seconds past the time t+1.0 and the waveform W(t+1.0) 1.65 seconds past the time t+1.0 and adding it to the calculated autocorrelation function ACF(t) and autocorrelation function ACF(t+0.5), the amount of calculation can be reduced.

[0133] In this way, at each timing for calculating the autocorrelation function, the heart rate calculation unit 34 of the present embodiment does not calculate the autocorrelation function for the entire target waveform at that timing, but calculates the autocorrelation function for the most recent part of the target waveform at that timing and adds it to the autocorrelation function calculated at the past timing, thereby suppressing the increase in the amount of calculation processing.

[0134] Specifically, the heart rate calculation unit 34 is, for example, Fig. 9 The heart rate of the subject S is calculated through the following process.

[0135] In step S51, the heart rate calculation unit 34 sequentially calculates the autocorrelation function of the latest 0.5 second waveform and the past 1.65 second waveform of each of the heartbeat waveforms HW1 to HW4. Specifically, the calculation is performed as follows using, for example, an array AR provided in the storage unit 35. Here, the calculation related to the heartbeat waveform HW1 is described as an example. The calculation related to the heartbeat waveforms HW2 to HW4 is also the same.

[0136] Array AR( Fig.10(b) can store 165 elements. The array AR stores the sampling values ​​a(n) (n=1, 2, ..., 165) of the amplitude AM of the heartbeat waveform HW1 every 0.01 seconds (i.e., the sampling period after downsampling in the waveform acquisition step S2). The sampling values ​​stored in the array AR are consistent with the 1.65 second heartbeat waveform HW1 ( Fig.10 corresponds to (a).

[0137] It should be noted that while the body movement determination flag is set by the body movement determination unit 32 , a value of 0 is stored as the sampling value a(n) of the amplitude AR.

[0138] First, the heart rate calculation unit 34 generates an array AR after shifting the array AR by -164 times. 164 ( Fig.10 Then, for the array AR 164 Each element of is multiplied by the sample value a(165), and the multiplication result is stored in the multiplication operation array AAR( Fig.10 (d)). At this time, the data stored in the multiplication operation array AAR represents the autocorrelation function of the heartbeat waveform HW1 of the latest 0.01 second calculated within the calculation window of 1.65 seconds.

[0139] Next, the heart rate calculation unit 34 generates an array AR after shifting the array AR by -163 times. 163 ( Fig.10 Then, for the array AR 163 Multiply each element of by the sample value a(164), and add the multiplication result to the multiplication operation array AAR ( Fig.10 At this time, the data stored in the multiplication operation array AAR represents the autocorrelation function of the heartbeat waveform HW1 of the latest 0.02 seconds calculated within the calculation window of 1.65 seconds.

[0140] Similarly, the heart rate calculation unit 34 creates an array AR after shifting the array AR by -N times (N=162, 161, . . . , 115). N Then, for the array AR N Each element of is multiplied by the value of the sampling value a(N+1), and the multiplication result is added to the multiplication array AAR. The heart rate calculation unit 34 repeatedly performs these processes and creates the array AR after shifting the array AR by -115 times for the 50th time. 115 ( Fig.10 Then, for the array AR 115 Multiply each element of by the value of a(116), and add the multiplication result to the multiplication array AAR ( Fig.10At this time, the data stored in the multiplication operation array AAR represents the autocorrelation function of the heartbeat waveform HW1 of the latest 0.5 seconds calculated within the calculation window of 1.65 seconds.

[0141] In step S52, the heart rate calculation unit 34 determines whether the multiplication result of 50 times (0.5 seconds) is added to the multiplication array AAR. If the multiplication result of 50 times (0.5 seconds) is not added, the process returns to S51. If the multiplication result of 50 times (0.5 seconds) is added, the calculation result stored in the multiplication array AAR is stored in the storage unit 35 (S53).

[0142] The heart rate calculation unit 34 performs steps S52 and S53 for each of the heartbeat waveforms HW1 to HW4. Hereinafter, the autocorrelation functions calculated within the calculation window of 1.65 seconds for the heartbeat waveforms HW1, HW2, HW3, and HW4 for 0.5 seconds stored in step S53 are referred to as partial autocorrelation functions PAF1, PAF2, PAF3, and PAF4, respectively.

[0143] The heart rate calculation unit 34 stores the partial autocorrelation functions PAF1 to PAF4 in the storage unit 35 in a FIFO manner. The storage unit 35 has defined areas capable of sequentially storing 16 autocorrelation functions PAF1 to PAF4.

[0144] In step S54, the heart rate calculation unit 34 calculates autocorrelation functions AF1, AF2, AF3, and AF4 by adding the 16 autocorrelation functions PAF1, PAF2, PAF3, and PAF4 stored in the storage unit 35. The heart rate calculation unit 34 stores the calculated autocorrelation functions AF1 to AF4 in the storage unit 35. The autocorrelation functions AF1 to AF4 respectively represent the autocorrelation functions of the heartbeat waveforms HW1 to HW4 of the most recent 8 seconds calculated within a calculation window of 1.65 seconds.

[0145] In step S55 , the heart rate calculation unit 34 calculates the total autocorrelation function AF by adding the autocorrelation functions AF1 to AF4 stored in the storage unit 35 . The heart rate calculation unit 34 stores the calculated total autocorrelation function AF in the storage unit 35 .

[0146] In step S56, the heart rate calculation unit 34 determines whether the body movement period within the most recent 8 seconds (hereinafter appropriately referred to as the "calculation target time") associated with the calculation of the autocorrelation functions AF1 to AF4 and the calculation of the total autocorrelation function AF is shorter than one third of the entire period (8 seconds).

[0147] When it is determined that the body motion period is more than one third of the entire calculation target period (S56: No), the heart rate calculation unit 34 outputs an error (S58). This is because during the period when the subject S has body motion, the heartbeat waveform is disturbed by the influence of the body motion, making it difficult to accurately determine the heartbeat cycle and calculate the heart rate.

[0148] When it is determined that the body movement occurrence period is shorter than one third of the entire calculation target period (S56: Yes), the heart rate calculation unit 34 calculates the heart rate of the subject S in step S57. The heart rate calculation unit 34 detects the peak point based on the autocorrelation functions AF1 to AF4 and the total autocorrelation function AF using at least one of the following (i) to (iv).

[0149] (i) The waveform with the highest power of signal amplitude in the target calculation period is determined among heartbeat waveforms HW1 to HW4, and the autocorrelation function corresponding to the determined waveform is used. In this case, for example, when the power of signal amplitude of heartbeat waveform HW1 is determined to be the highest, autocorrelation function AF1 is used.

[0150] (ii) The autocorrelation function having the largest absolute value of the peak among the autocorrelation functions AF1 to AF4 is used.

[0151] (iii) Normalize autocorrelation function AF1 by the power of the signal amplitude of heartbeat waveform HW1. Similarly, normalize autocorrelation functions AF2 to AF4 by the power of the signal amplitude of heartbeat waveforms HW2 to HW4. Then, use the autocorrelation function with the largest absolute value of the peak among the normalized autocorrelation functions AF1 to AF4.

[0152] (iv) Using the total autocorrelation function AF: This improves the SN ratio (signal-to-noise ratio) and increases the accuracy of heart rate calculation.

[0153] Specifically, the heart rate calculation unit 34 calculates the heart rate of the subject S through the following steps, for example. Here, calculation using the autocorrelation function AF1 will be described. The calculation method described below can be applied in the same manner regardless of which of the above (i) to (iv) is used.

[0154] First, the heart rate calculation unit 34 performs peak point detection on the autocorrelation function AF1. At this time, the heart rate calculation unit 34 determines the range for performing peak point detection in consideration of the estimated value of the heart cycle of the subject S estimated in the heart cycle estimation step S4.

[0155] As described above, it is considered that the peak of the autocorrelation function AF1 appears at a position corresponding to the period of the heartbeat waveform HW1. Therefore, the heart rate calculation unit 34 considers the estimated value of the heartbeat cycle of the subject S (i.e., the period of the heartbeat waveform HW1) estimated in the heartbeat cycle estimation step S4, and limits the range of performing peak point detection to the estimated value. This can reduce the burden of calculation processing in peak point detection and improve the reliability of the detection result.

[0156] Next, the heart rate calculation unit 34 performs interpolation processing of the autocorrelation function AF1 before and after the detected peak point.

[0157] Autocorrelation functions AF1 to AF4 and the total autocorrelation function AF are based on at least one of the heartbeat waveforms HW1 to H4 that appear at a sampling period of 0.01 seconds. Therefore, data points of autocorrelation functions AF1 to AF4 and the total autocorrelation function AF are also obtained at 0.01 second intervals.

[0158] Here, as a result of the peak point detection performed on the autocorrelation function AF1, Fig.11 The data point of amplitude af(p) shown in (a) is shown in FIG. 1 . At this time, the amplitude af(p-1) at the data point before the amplitude af(p) and the amplitude af(p+1) at the data point after the amplitude af(p) are both smaller than the amplitude af(p), so if only these three data points are observed, it can be seen that the amplitude af(p) corresponds to the peak point. However, the data points of the autocorrelation function AF1 are spaced at 0.01 second intervals, so sometimes the true peak point of the autocorrelation function AF1 exists between the amplitude af(p) and the amplitude af(p-1) or between the amplitude af(p) and the amplitude af(p+1).

[0159] Therefore, the heart rate calculation unit 34 performs interpolation processing on the autocorrelation function AF1 to obtain the true peak point PK of the autocorrelation function AF1. Specifically, the interpolation processing is performed, for example, by interpolating the convex quadratic function F( Fig.11 (b)) and the curve fitting of the autocorrelation function AF1. Thus, the following formula representing the offset OS between the peak point detected by the peak point detection and the true peak point PK can be obtained.

[0160]

[0161] Here, Ts is a sampling period of data points of the autocorrelation function AF1 (0.01 [s] in this embodiment).

[0162] Fig.11(b) shows a state where the quadratic function F is fitted by the interpolation process. The heart rate calculation unit 34 detects the peak point PK of the quadratic function F as a true peak point.

[0163] Next, the heart rate calculation unit 34 determines the delay time L corresponding to the true peak point (ie, the peak point PK of the quadratic function F) as the heartbeat period T of the subject S. Then, the heart rate HR [bpm] of the subject S is calculated using the following (Formula 2).

[0164] HR=60 / T[bpm] Formula 2

[0165] The heart rate calculation unit 34 sequentially calculates the heart rate HR based on at least one of the sequentially calculated autocorrelation functions AF1 to AF4 and the total autocorrelation function AF. The heart rate calculation unit 34 calculates the heart rate HR every 0.01 seconds, for example.

[0166] [Display step S6]

[0167] In the display step S6, the display control unit 41 of the user terminal 40 sequentially obtains the heart rate HR sequentially calculated by the heart rate calculation unit 34 from the biological information acquisition unit 30, and displays it on the display unit 42. In addition, in the display step S6, the notification unit 43 may be used to perform notification in addition to the display using the display unit 42, or the notification unit 43 may be used to perform notification instead of the display using the display unit 42. In this case, for example, when the heart rate HR of the subject S deviates from a prescribed range, the display control unit 41 emits a notification sound to notify the doctor, nurse, care worker, etc., who is the user of the biological information acquisition system 100, of the abnormal heartbeat state.

[0168] Specifically, the display control unit 41 performs display in the following manner, for example.

[0169] In this embodiment, the display control unit 41 sequentially obtains the heart rate HR calculated by the heart rate calculation unit 34 and stores it in the storage unit 45, and displays the median of the plurality of heart rates HR within the most recent minute on the display unit 42 ( Fig.12 (a)). This can suppress the influence of instantaneous changes in heart rate HR caused by interference, etc. When the heart rate HR exceeds a predetermined threshold value, the voice notification is performed by the notification unit 43, which helps to suppress false notifications.

[0170] In addition, while the subject S is not on the bed BD, the display control unit 30 does not display the heart rate HR on the display unit 42 ( Fig.12(b)). Specifically, the period during which the subject S is not on the bed BD can be, for example, a period during which the biological information acquisition unit 30 (respiration rate calculation unit, weight calculation unit) does not calculate the respiration rate of the subject S, a period during which the weight of the subject S detected by the load detection unit 1 is less than a specified value, etc.

[0171] Specifically, the biological information acquisition unit 30 may be based on the load signal s 1 ~s 4 The center of gravity of the subject S is calculated sequentially, and the respiration rate of the subject S is calculated based on the temporal change of the center of gravity of the subject S corresponding to the respiration of the subject S. Alternatively, the biological information acquisition unit 30 may calculate the respiration rate of the subject S based on the load signal s 1 ~s 4 At least one of them performs Fourier analysis to determine the peak frequency that appears in the frequency band corresponding to breathing, and regards the determined peak frequency as the breathing frequency of the subject S to calculate the breathing rate of the subject S.

[0172] The biological information acquisition unit 30 can convert the load signal s 1 ~s 4 Add them together to calculate the weight of the subject S.

[0173] Even during a period when the subject S is not on the bed BD, the biological information acquisition unit 30 may calculate the heart rate based on interference (for example, air vibration caused by the operation of peripheral equipment such as an air conditioner, etc.). Therefore, by stopping the display of the heart rate HR on the display unit 42 during a predetermined period when it can be estimated that the subject S is not on the bed BD, it is possible to prevent erroneous display of the heart rate HR.

[0174] The effects of the biological information acquiring system 100 according to the present embodiment will be summarized below.

[0175] First, in the heartbeat cycle estimation step S4, the biological information acquisition system 100 of the present embodiment estimates the heartbeat cycle of the subject S based on the heartbeat waveform HW1, etc. Then, the peak point detection of the autocorrelation function AF1, etc. is performed within a range consistent with the estimated heartbeat cycle, and the heart rate HR of the subject S is calculated based on the detected peak point. Since the biological information acquisition system 100 of the present embodiment performs the peak point detection of the autocorrelation function AF1, etc. in consideration of the pre-estimated heartbeat cycle, even in the case where the heartbeat waveform HW1, etc. is distorted and the periodicity is disturbed, the peak point position of the autocorrelation function AF1, etc. can be determined with high accuracy, and the heart rate HR can be calculated with high accuracy. In addition, the calculation processing load of the peak point detection is small.

[0176] In the heart rate calculation step S5, the biological information acquisition system 100 of this embodiment does not calculate the autocorrelation function of the target period as a whole at one time, but decomposes it into partial autocorrelation functions and calculates and then adds them. Therefore, the autocorrelation function at each timing can be calculated with less calculation amount. In this way, the load of calculation processing is small, which is particularly advantageous when the biological information acquisition system 100 is installed as an embedded program of a microcomputer (microcomputer).

[0177] In the heart rate calculation step S5 , the biological information acquiring system 100 of the present embodiment performs interpolation processing to detect a true peak point, and calculates the heart rate HR of the subject S based on the true peak point. Therefore, the heart rate HR of the subject S can be obtained with higher accuracy.

[0178] In the display step S6, the biological information acquiring system 100 of this embodiment stops displaying the heart rate HR on the display unit 42 during a predetermined period during which it can be estimated that the subject S is not on the bed BD. Therefore, the biological information acquiring system 100 of this embodiment can prevent erroneous display of the heart rate HR.

[0179] <Modification>

[0180] The biological information acquiring system 100 of the above-described embodiment may also adopt the following modifications.

[0181] In the cardiac cycle estimation step S4 of the above embodiment, the cardiac cycle estimation unit 33 determines whether the interval between the falling zero crossing points fx, the peak point p, the valley point b, etc. in the previous cycle meet the specified conditions each time the falling zero crossing point fx is determined. However, the present invention is not limited thereto. Alternatively, the same determination may be performed each time the rising zero crossing point rx is determined.

[0182] In the cardiac cycle estimation step S4 of the above embodiment, the determination of whether the amplitude AM (positive value) at the peak point p is less than the body movement threshold THp and / or the determination of whether the amplitude AM (negative value) at the valley point b is greater than the body movement threshold THn may be omitted. In the cardiac cycle estimation step S4 of the above embodiment, the determination of whether the variation ratio of the interval PR of the previous cycle relative to the interval PR of the cycle before the cycle is within a prescribed range may be omitted.

[0183] In the cardiac cycle estimation step S4 of the above embodiment, the median of the eight intervals PR stored in the storage unit 35 is set as the estimated value of the cardiac cycle of the subject S, but the present invention is not limited thereto. The number of intervals PR stored in the storage unit 35 may be any number or one. The cardiac cycle estimation unit 33 may also set the median or average of any number of intervals PR as the estimated value of the cardiac cycle of the subject S.

[0184] In the heartbeat cycle estimating step S4 of the above embodiment, the heartbeat cycle estimating unit 33 estimates the heartbeat cycle of the subject S using the heartbeat waveform HW1, but the present invention is not limited thereto. The heartbeat cycle estimating unit 33 may estimate the heartbeat cycle of the subject S using at least one of the heartbeat waveforms HW1 to HW4.

[0185] In the heart rate calculation step S5 of the above embodiment, the heart rate calculation unit 34 sequentially calculates the partial autocorrelation functions PAF1~PAF4 of the latest 0.5 second respiratory waveform HW1~HW4 and the past 1.65 second respiratory waveform HW1~HW4, and performs addition operations for 8 seconds to calculate the autocorrelation functions AF1~AF4, but is not limited to this.

[0186] The target period for calculating the partial autocorrelation functions PAF1 to PAF4 is not limited to 0.5 seconds but is arbitrary. Also, the target period for calculating the autocorrelation functions AF1 to AF4 is not limited to 8 seconds but is arbitrary.

[0187] That is, the heart rate calculation unit 34 can adopt an arbitrary scheme including the following steps: calculating the partial autocorrelation functions PAF1~PAF4 (first autocorrelation function) of the heartbeat waveforms HW1~HW4 included in a specified period (first period), calculating the partial autocorrelation functions PAF1~PAF4 (second autocorrelation function) of the heartbeat waveforms HW1~HW4 included in a specified period (second period) after the specified period, calculating the partial autocorrelation functions PAF1~PAF4 (third autocorrelation function) of the heartbeat waveforms HW1~HW4 included in a specified period (third period) after the specified period, calculating the sum of the first autocorrelation function and the second autocorrelation function as autocorrelation functions AF1~AF4 at a specified timing (first moment), and calculating the sum of the second autocorrelation function and the third autocorrelation function as autocorrelation functions AF1~AF4 at a subsequent specified timing (second moment).

[0188] In the heart rate calculation step S5 of the above embodiment, the heart rate calculation unit 34 may calculate the autocorrelation functions AF1 to AF4 instead of the partial autocorrelation functions PAF1 to PAF4. In this case, for example, the autocorrelation functions of the latest 8-second heartbeat waveforms HW1 to HW4 calculated within a calculation window of 1.65 seconds are calculated every 0.5 seconds.

[0189] In the heart rate calculation step S5 of the above embodiment, when it is determined that the body motion period is more than one third of the entire calculation target period (S56: Yes), the heart rate calculation unit 34 outputs an error (S58). However, the present invention is not limited thereto, and the heart rate calculation unit 34 may output an error when the body motion period is an arbitrary ratio (1 / 2, 1 / 4, etc.) of the calculation target period in step S56. In addition, the heart rate calculation unit 34 may output an error when at least a part of the calculation target period is the body motion period.

[0190] In the heart rate calculation step S5 of the above embodiment, the heart rate calculation unit 34 may not perform interpolation processing. In this case, the heartbeat period T of the subject S is determined and the heart rate HR [bpm] of the subject S is calculated using the peak of the autocorrelation function detected in the peak detection.

[0191] In the above embodiment, the display control unit 30 does not display the heart rate HR on the display unit 42 while the subject S is not on the bed BD. However, the present invention is not limited thereto. The display control unit 30 may adopt any scheme that makes the display of the heart rate HR on the display unit 42 different between the schemes for displaying the heart rate HR on the display unit 42 when the subject S is on the bed BD and the schemes for displaying the heart rate HR on the display unit 42 when the subject S is not on the bed BD.

[0192] Specifically, for example, the display control unit 30 may perform a normal display while the subject S is on the bed BD, and may perform a display using red text, a flashing display, etc. while the subject S is not on the bed BD. It should be noted that in this specification and the present invention, "no display" is also set as a scheme of the display method. In this way, by making the display scheme of the heart rate HR when the subject S is not in bed different from the display scheme of the heart rate HR when the subject S is in bed, the user can intuitively understand that the heart rate being displayed is not the heart rate of the subject S.

[0193] The biological information acquisition unit 30 of the above embodiment may not include the body movement determination unit 32. In this case, the process related to the body movement determination of the above embodiment may not be executed.

[0194] In the heartbeat information acquisition system 100 of the above embodiment, the heartbeat calculation unit 34 calculates the heartbeat based on the calculation of the autocorrelation value, but the present invention is not limited thereto. Various methods can be used to calculate the heartbeat based on the heartbeat waveform.

[0195] Specifically, for example, the heart rate calculation unit 34 may calculate the load signal s 1 ~s 4At least one of them performs Fourier analysis to determine the peak frequency that appears in the frequency band corresponding to the heartbeat, and regards the determined peak frequency as the heartbeat frequency of the subject S to calculate the respiratory rate of the subject S.

[0196] In this aspect, the estimated value of the heart cycle of the subject S estimated in the heart cycle estimating step S4 may be taken into consideration when determining the peak frequency.

[0197] In this specification and the present invention, the amplitude value of the negative value is less than the threshold value (negative value) means that the absolute value of the amplitude value of the negative value is greater than the absolute value of the threshold value (negative value). The comparison of the amplitude value (negative value) and the threshold value (negative value) specified in the present invention includes a scheme of comparing the absolute value of the amplitude value (negative value) and the absolute value of the threshold value (negative value).

[0198] In the biological information acquisition system 100 of the above embodiment, a single biological information acquisition unit 30 is connected to the user terminal 40, but the present invention is not limited thereto. A plurality of biological information acquisition units 30 may be connected to the user terminal 40. Alternatively, the biological information acquisition unit 30 and the user terminal 40 may be integrated, or the user terminal 40 may be understood as a part of the heart rate acquisition unit of the present invention.

[0199] The biological information acquisition system 100 of the above-mentioned embodiment does not necessarily need to include all the load detectors 11 to 14, and may include only at least one of the load detectors 11 to 14. In addition, the load detectors do not necessarily need to be arranged at the four corners of the bed, and may be arranged at any position in a manner that can detect the load of the subject on the bed and its change. In addition, the load detectors 11 to 14 are not limited to load sensors using beam-type load cells, and force sensors (force sensors) may be used, for example.

[0200] In the biological information acquiring system 100 of the above-described embodiment, the load detection unit 1 may be a plurality of pressure-sensitive sensors (pressure sensors) arranged in a matrix under the bed sheet.

[0201] The load detectors 11 to 14 may be integrally or detachably combined with the bed BD to form a bed system BDS ( Figure 2 ).

[0202] The display control unit 41 and the display unit 42 of the above-described embodiment may be combined with any heart rate calculation unit to form a heart rate calculation device. With such a heart rate calculation device, the acquired heart rate can be displayed more appropriately.

[0203] In the biological information acquisition device 30 of the above-described embodiment, the heartbeat cycle estimation unit 33 may be omitted. In this case as well, the heart rate calculation unit 34 can more efficiently acquire the heart rate.

[0204] As long as the characteristics of the present invention are maintained, the present invention is not limited to the above-described embodiments, and other embodiments that can be conceived within the technical concept of the present invention are also included in the scope of the present invention.

[0205] Description of Reference Numerals

[0206] 1: load detection unit; 11, 12, 13, 14: load detectors; 3: biological information acquisition unit; 31: heartbeat waveform acquisition unit; 32: body movement determination unit; 33: heartbeat cycle estimation unit; 34: heart rate calculation unit; 35: storage unit; 40: user terminal; 41: display control unit; 42: display unit; 43: notification unit; 44: input unit; 45: storage unit; BD: bed; BDS: bed system.

Claims

1. A heart rate acquisition device for acquiring the heart rate of a subject on a bed, wherein: The heart rate acquisition device comprises: a heartbeat waveform acquisition unit that acquires a heartbeat waveform based on an output of a load detector provided on the bed, wherein the heartbeat waveform represents a temporal variation in a load value corresponding to a heartbeat of the subject; a cardiac cycle estimating unit that obtains an estimated value of the cardiac cycle of the subject based on the transition of the cardiac waveform; and The heart rate calculation unit calculates the heart rate of the subject based on the heartbeat waveform and the estimated value.

2. The heart rate acquisition device according to claim 1, wherein: The cardiac cycle estimating unit obtains the estimated value based on determination of a valley point of the cardiac waveform, a rising zero-crossing point of the cardiac waveform, a peak point of the cardiac waveform, and a falling zero-crossing point of the cardiac waveform.

3. The heart rate acquisition device according to claim 2, wherein: When the interval between two consecutive rising zero crossings or between two consecutive falling zero crossings is within a specified range, and the amplitude of the heartbeat waveform at the valley point between the two consecutive rising zero crossings or between the two consecutive falling zero crossings is less than the valley point amplitude threshold, and the amplitude of the heartbeat waveform at the peak point between the two consecutive rising zero crossings or between the two consecutive falling zero crossings is greater than the peak point amplitude threshold, the heartbeat cycle estimation unit sets the interval between the two consecutive rising zero crossings or between the two consecutive falling zero crossings as the estimated value.

4. The heart rate acquisition device according to claim 3, wherein: When the amplitude of the heartbeat waveform at the valley point between the two consecutive rising zero crossings or between the two consecutive falling zero crossings is greater than the valley point body motion threshold, and the amplitude of the heartbeat waveform at the peak point between the two consecutive rising zero crossings or between the two consecutive falling zero crossings is less than the peak point body motion threshold, the heartbeat cycle estimation unit sets the interval between the two consecutive rising zero crossings or between the two consecutive falling zero crossings as the estimated value.

5. The heart rate acquisition device according to claim 3 or 4, wherein: When the interval between the two consecutive rising zero crossing points or the two consecutive falling zero crossing points is greater than a specified value, the cardiac cycle estimation unit determines that the interval between the two consecutive rising zero crossing points or the two consecutive falling zero crossing points is within the specified range.

6. The heart rate acquisition device according to any one of claims 3 to 5, wherein: The heart rate cycle estimation unit sequentially determines the rising zero crossing point or the falling zero crossing point and calculates the interval between the two consecutive rising zero crossing points or the two consecutive falling zero crossing points. When the variation ratio of the interval calculated at a certain timing relative to the interval calculated immediately before the timing is within a prescribed range, the heart rate cycle estimation unit determines that the interval is within the prescribed range.

7. The heart rate acquisition device according to any one of claims 1 to 6, wherein: The calculation of the heart rate in the heart rate calculation unit includes: Calculating the autocorrelation function of the heartbeat waveform; detecting a peak point of the autocorrelation function; and calculating the heart rate based on the detected position of the peak point, The heart rate calculation unit determines a range in which the peak point detection is performed based on the estimated value.

8. The heart rate acquisition device according to claim 7, wherein: In the calculation of the heart rate in the heart rate calculation unit, calculating the heart rate based on the detected position of the peak point includes: Performing interpolation processing around the detected peak point; and The heart rate is calculated based on the position of the peak point determined by the interpolation process.

9. The heart rate acquisition device according to claim 7 or 8, wherein: The calculation of the autocorrelation function in the heart rate calculation unit includes: Calculating a first autocorrelation function of the heartbeat waveform included in a first period; Calculating a second autocorrelation function of the heartbeat waveform included in a second period after the first period; calculating a third autocorrelation function of the heartbeat waveform included in a third period after the second period; Calculate the sum of the first autocorrelation function and the second autocorrelation function at a first moment as the autocorrelation function; and At a second time after the first time, a sum of the second autocorrelation function and the third autocorrelation function is calculated as the autocorrelation function.

10. The heart rate acquisition device according to any one of claims 7 to 9, wherein: The load detector includes a first load detector and a second load detector, The heartbeat waveform acquisition unit acquires a first heartbeat waveform based on the output of the first load detector and a second heartbeat waveform based on the output of the second load detector. The autocorrelation function calculated by the heart rate calculation unit is a sum of an autocorrelation function of a first heartbeat waveform and an autocorrelation function of a second heartbeat waveform.

11. The heart rate acquisition device according to any one of claims 7 to 10, wherein: further comprising a body movement determination unit for determining whether the subject has body movement based on a comparison between the amplitude of the heartbeat waveform and a body movement threshold value, When the ratio of the period in which the subject has body motion to the target period for calculating the autocorrelation function is equal to or greater than a threshold, the heart rate calculation unit does not calculate the heart rate based on the autocorrelation function.

12. The heart rate acquisition device according to any one of claims 1 to 11, wherein: Also available: A display unit that displays the heart rate calculated by the heart rate calculation unit; and A display control unit controls the display content of the display unit, The display control unit causes the display unit to display the heart rate calculated by the heart rate calculation unit in a different manner when the subject is on the bed and when the subject is not on the bed.

13. The heart rate acquisition device according to claim 12, wherein: The apparatus further comprises: a weight calculation unit for calculating the weight of the subject based on the output of the load detector; and / or a respiratory rate calculation unit for calculating the respiratory rate of the subject based on the output of the load detector. When the calculated weight of the subject is less than a threshold value and / or when the respiration rate of the subject is not calculated, the display control unit determines that the subject is not on the bed.

14. The heart rate acquisition device according to claim 12 or 13, wherein: The heart rate calculation unit calculates the heart rate in sequence, The display control unit displays the medians of the plurality of heart rates calculated sequentially on the display unit.

15. A heart rate acquisition device for acquiring the heart rate of a subject on a bed, wherein: The heart rate acquisition device comprises: a heart rate calculation unit that calculates the heart rate of the subject based on a temporal change in an output of a load detector provided on the bed in accordance with a heartbeat of the subject; a display unit, configured to display the heart rate calculated by the heart rate calculation unit; as well as A display control unit controls the display content of the display unit, The display control unit causes the display unit to display the heart rate calculated by the heart rate calculation unit in a different manner when the subject is on the bed and when the subject is not on the bed.

16. The heart rate acquisition device according to claim 15, wherein: The apparatus further comprises: a weight calculation unit for calculating the weight of the subject based on the output of the load detector; and / or a respiratory rate calculation unit for calculating the respiratory rate of the subject based on the output of the load detector. When the calculated weight of the subject is less than a threshold value and / or when the respiration rate of the subject is not calculated, the display control unit determines that the subject is not on the bed.

17. The heart rate acquisition device according to claim 15 or 16, wherein: The heart rate calculation unit calculates the heart rate in sequence, The display control unit displays the medians of the plurality of heart rates calculated sequentially on the display unit.

18. A heart rate acquisition device for acquiring the heart rate of a subject on a bed, wherein: The heart rate acquisition device comprises: a heartbeat waveform acquisition unit that acquires a heartbeat waveform based on an output of a load detector provided on the bed, wherein the heartbeat waveform indicates a temporal change in a load value corresponding to a heartbeat of the subject; and a heart rate calculation unit that calculates the heart rate of the subject based on the heartbeat waveform; The calculation of the heart rate in the heart rate calculation unit includes: Calculating the autocorrelation function of the heartbeat waveform; detecting a peak point of the autocorrelation function; and calculating the heart rate based on the detected position of the peak point, The calculation of the autocorrelation function includes: Calculating a first autocorrelation function of the heartbeat waveform included in a first period; Calculating a second autocorrelation function of the heartbeat waveform included in a second period after the first period; calculating a third autocorrelation function of the heartbeat waveform included in a third period after the second period; Calculate the sum of the first autocorrelation function and the second autocorrelation function at a first moment as the autocorrelation function; and At a second time after the first time, a sum of the second autocorrelation function and the third autocorrelation function is calculated as the autocorrelation function.

19. The heart rate acquisition device according to claim 18, wherein: In the calculation of the heart rate in the heart rate calculation unit, calculating the heart rate based on the detected position of the peak point includes: Performing interpolation processing around the detected peak point; and The heart rate is calculated based on the position of the peak point determined by the interpolation process.

20. A bed system comprising: bed; a load detector, disposed on the bed; and The heart rate acquisition device according to any one of claims 1 to 19.

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