JP2002219108A - Optical ballistocardiograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ballistocardiograph which can be compact in its struc ture, and is not restricted by the size of a bed or mattress to be used and free from electric shock or an invasion of noise. SOLUTION: An optical ballistocardiograph equipped with an optical fiber 1 upon which either a patient or a subject is placed, a light-emitting element 5 and light receiving element 6 for the measurement of changes of the quantity of light that generates from the patient's or the subject's body movements, or the like, and transmits an inner part of the optical fiber. The optical fiber 1 is anchored in the rigid upper and lower plates 3, 4 in order to enhance the sensitivity of the device, and a stress integrator 2 is installed for concentrating the stress that affects the optical fiber 1. The compactness of the device is therefore possible because of such a simple structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of quality of care and labor saving by remote monitoring of the health of bedridden elderly people.
The present invention relates to an optical ballist cardiograph (an unrestricted heart rate / respiration / body motion measuring device) for performing labor-saving nursing by a remote monitor of a patient on a bed and performing accurate evaluation by measurement without making the subject aware of the measurement.

[0002]

2. Description of the Related Art In order to evaluate the mental and physical condition of a human body, it is desirable to perform unrestricted measurement without making the subject aware of the measurement. This unrestricted human body measurement method enables dynamic monitoring of patients and bedridden elderly people, and can save labor and improve quality of nursing and nursing care.

Considering the possibility of unrestricted measurement of the heart rate and the like of the human body, when the ventricle ejects blood into the arterial system at once, the ventricle receives a mechanical reaction. Also, when the ejected blood is deflected by the aortic arch, the aortic arch also undergoes recoil. If the human body rests on a platform that can easily move in height, the platform will exhibit constant movement. This movement is greater as the recoil is greater, and the magnitude of the recoil depends on the stroke volume of the heart. If the change in stress due to these recoils can be detected, it is possible to measure the heart rate and the like simply by placing the subject on a measuring table.

A measuring apparatus utilizing this phenomenon is called a ballist cardiograph (BCG). Conventionally, a bed movable in a horizontal direction or an electrostatic charge sensitive bed using a capacitive sensor has been used. These are not widely used because of their complicated structure and delicate operation.

[0005] The first practical measuring device is a table suspended from above, which is easily moved elastically only in the height direction by a spring, and the movement of the table is measured optically using a camera. It is a device to do. FIG. 1 shows a typical example of the measurement result.

In the BCG signal waveform of FIG. 1, H, I, J,
It shows a number of extreme values as indicated by K, L, M, N, O.
The mechanism of generation of all extrema is not known, but I corresponds approximately to the recoil of ventricular contraction and J approximately corresponds to the recoil of the aortic arch. I and J values (mm) and aortic cross-sectional area A
(Cm ² ) and ventricular contraction time C (seconds)

(Equation 1) Is empirically required. Although it is not very accurate as an absolute value, it has been applied clinically to see temporal and relative changes because it can be easily measured.

[0007] In the above-mentioned conventional apparatus, it is necessary to move the patient to a bed dedicated to measurement, which is less comfortable than a normal bed, so that long-time measurement is impossible.

[0008] In 1970, a portable acceleration device was proposed. The device could be worn on the patient's shoulder or head and the data was written to a conventional electrocardiograph. However, since this device measures only the movement of the head and not the whole body, the measured signal may not be similar to the normal BCG signal pattern as shown in FIG. Only mutual comparison of the results measured within the range was possible. Despite these limitations, this device has been shown to be clinically useful (Wr
light, B .; M. , 1970, “A port
able ballistocardiograph
h ", Bibl. Cardiol., Vol.
3, p. 72-75. ).

[0009] The most advanced BCG measuring device existing is
Static charge sensitive bed
Biomat (B) using Nsitive bed
IO-MATT: Trademark of BIOTEC (Finland), Alihanka, J. et al. , Vaahtorant
a, K. , And Saarivivi, I .; ,
1981, "A new method for l
ong-term monitoring of the
e ballistocardiogram, hear
rt rate and respiration ",
Am. J. Physiol. Vol. 240,
p384-392. ). This device was not developed as a special circulatory system, but for long-term recording and patient monitoring. The device can also monitor respiration by passing the output signal through different filters.

This device is essentially a large capacitor with a hard insulating plate sandwiched between metal plates (200 cm × 90 cm × 0.1 mm) on both sides. This is placed on the patient's bed, and the patient rests on the mattress. A change in the electrostatic potential of the metal plates on both sides due to the charge distribution induced by various body movements of the patient is detected by a high-performance differential amplifier used for an electroencephalograph or the like.

In this device, the capacitor is shielded and grounded with a conductive material so as to form a kind of Faraday cage in order to prevent the influence of electric charges generated by clothes and bed covers. As a result, interference from electromagnetic waves and AC power, and the influence of other measuring devices in the vicinity can be eliminated.

The measurement essentially involves a change in the capacitance of the capacitor. If you only need to measure the body movement, you can use a plastic foam mattress.
For the purpose of signal measurement, two separate plastic plates are used and hollow inside, so that the mechanical movement producing the electrostatic charge is limited to the surface only.

[0013]

The problems of the biomat described above include the following.

1) The structure for measuring the electrostatic charge is complicated, large and expensive. Current size is 200cm ×
It is 90 cm × 2 cm. For the sensitivity of the device, it is necessary that the distance between the two electrodes is sufficiently large and the two electrodes can be largely deformed and a large electrode area is required, so that miniaturization is difficult. Also,
Even if it is possible to reduce the size, due to the structure of the device,
It is difficult to make things of any size.

2) Because of the delicate structure and measurement method, not everyone can use it. Mattresses need to be placed on biomats to protect the structure, which limits the available beds and mattress structures. Not all environments can be used.

3) There is a danger in using electricity for measurement. At least give patients anxiety about danger.

4) Even if shielded, it is not perfect due to the structure and size, and noise may be mixed.

Other conventional techniques and their problems are listed below.

1. Measurement of heart rate and respiration a) Portable type heart rate and respiration measurement device capable of continuous measurement b) Holter electrocardiograph c) Embla (measuring device for EEG, heart rate, respiration, etc.) Fla
ga (Iceland)

The problems of these measuring instruments are as follows. (1) A sensor such as an electrode is required, and a small recorder must be mounted or data must be transmitted using a wireless device. (2) It takes a lot of time to attach the sensor. (3) Make the subject aware of the measurement. (4) It is expensive due to its complicated structure. (5) Electricity is used, and subjects and patients are anxious about danger. For this reason, it is not comfortable for the subject / patient, and is far from being unrestricted in the true meaning.

2. Measurement of body movement a) Infrared image capturing and analysis from above the bed (Takae Kataoka et al., Sensor Handbook p1074-1075, Baifukan, Kyoto (1986)) b) Temperature distribution measurement using a thermistor array (Togawa)
a, T.A. , Tamura, T .; , Zhou,
J. Mizukami, H .; and Ishi
Jima, M .; , 1989, "Physiolo.
medical monitoring systems
attached to the bedand sa
unitary equipments ”, Proce
edings of IEEE EMBS 11 ^th I
international conference,
p. 1461-1463. C) Trial of pressure distribution measurement using a capacitive sensor similar to a biomat (Tomohiro Okubo et al., 1994, "Measurement system of patient dynamics by capacitive sensor", Medical Electronics and Biotechnology, vol. 32, p132) -135)

These measuring methods require large-scale equipment and are expensive. Further, the method of measuring the pressure distribution using the capacitive sensor of c) has a problem of response time and a problem of danger.

3. Unconstrained Heart Rate Measurement in Bathtub a) Method of Electrical Measurement Using Water's Slight Conductivity (Takumi Yoshimura et al., 1994, "Development and Evaluation of Heart Rate Monitor in Unconstrained Bathtub" ”, Medical electronics and biotechnology,
vol. 32, p246-253) b) Method of optically measuring ripples caused by the BCG signal on the water surface These measurement methods have a limitation in a bathtub, and a)
The method of (1) has a problem that danger of electric shock or its anxiety, and the method of (b) is difficult to put into practical use due to large disturbance.

The problem to be solved by the present invention is as follows.
It is an object of the present invention to provide a ballist cardiograph which can be downsized, is not restricted by the bed or mattress used, has no risk of electric shock, and is free from noise.

[0025]

In order to solve the above-mentioned problems, an optical ballist cardiograph according to the present invention comprises a light-transmitting solid on which a patient or a subject is placed, and a body movement of the patient or the subject. Means for measuring a change in the amount of light that is transmitted through the interior of the translucent solid. In the present specification, the body motion and the like include unrestricted heartbeats, respiration when the heart sends blood to the arterial system, and periodic body motions due to lung motion during respiration.

In this optical ballist cardiograph, the following embodiments are given. (1) The translucent solid is sandwiched between upper and lower rigid plates. (2) The translucent solid has a rod-like structure that concentrates stress. (3) The translucent rod can be an optical fiber. (4) In order to amplify the load applied to the translucent solid, a stress concentrator that partially presses against the translucent solid is provided. (5) The stress concentrator is formed on at least one of the inner surfaces of the upper and lower plates as a protrusion or a ridge contacting the optical fiber.

[0027]

Next, an embodiment of the present invention will be described. It is well known that when a stress is applied to a solid polymer material, the refractive index changes and birefringence occurs, which is called a photoelastic effect. Using the photoelastic effect of this solid polymer, it was considered to measure the BCG signal of the human body and the movement and respiration of the subject's body. In order to detect slight pressure fluctuations superimposed on the weight of the subject's body as optical fluctuations, a light-transmitting solid, here a plastic optical fiber, is used, and a light-emitting element and a light-receiving element are attached to both ends. The light intensity transmitted through the optical fiber was monitored.

As shown in FIG. 2, when a stress F is applied to the freely bent optical fiber 1 in a direction in which the curvature is changed, the degree of reflection on the inner wall surface of the optical fiber 1 changes. The change in intensity is large. It is also possible to detect faint vibrations and small winds that occur in the room.

As shown in FIG. 3, if a coil is formed by winding the optical fiber 1 using a core material 11 made of a material capable of sufficiently sensing the weight of a human body, a sensor with high sensitivity can be manufactured. Can be. However, the sensor shown in FIG. 3 has high sensitivity because the elongation of the optical fiber 1 due to the stress F is amplified in proportion to the number of turns, but the bulk of the device becomes large, the overall structure becomes complicated, and the simplicity is increased. Is not enough.

Further, as shown in FIG. 4, a sensor of a type in which a stress F is applied perpendicularly to the axial direction of the optical fiber 1 was studied. However, in the case of this mode of stress, the sensitivity of the optical fiber alone is small.

Therefore, as shown in FIG. 5, one optical fiber 1 is arranged between the hard plates 3 and 4 in a meandering state and is sandwiched between the hard plates 3 and 4, so that the length of the optical fiber 1 constituting the sensor unit is reduced as much as possible. I tried to make it longer. As a result, the stress F is applied to the entire surface of one optical fiber 1 in the axial direction,
Sensitivity can be improved. This is the basic configuration of the present invention.

However, in this case, since the stress F is dispersed and applied to the entire side surface of the optical fiber 1, it is difficult to improve the sensitivity.
Therefore, as a preferred embodiment of the present invention, the sensitivity is improved using a stress concentrator.

That is, as shown in FIG. 6, an optical fiber 1 made of an elastic material and a stress concentrator 2 intersecting the axis of the optical fiber 1 are arranged between the rigid upper and lower plates 3 and 4. Integrate while sandwiched.

As the stress concentrator 2, the same wire as that of the optical fiber 1 can be used, or another one having a circular cross section can be used.

With this configuration, when the stress F is applied to the upper plate 3, the stress is concentrated at the intersection of the optical fiber 1 and the stress concentrator 2. Thereby, the stressed portion of the optical fiber 1 is deformed, and the cross-sectional shape is distorted from a circular shape. When light passes through the distorted portion, the light transmittance decreases. Using this, the change in stress due to body movement of the patient and the subject lying on the upper board 3 is measured. At this time, among the frequencies included in the transmitted light intensity change signal, respiration, heartbeat,
By using a filter that extracts only the frequency corresponding to the body motion, such information can be extracted.

As the stress concentrator, in addition to the wire, projections and ridges may be formed on the upper and lower plates 3 and 4 to apply the stress to the optical fiber in a concentrated manner. Further, in addition to a light-transmitting solid formed of a rod-shaped body such as an optical fiber, a light-transmitting plate-shaped solid may be used to measure a change in planar light transmittance.

[0037]

Embodiments of the present invention will be described below. FIGS. 7A and 7B show a first embodiment of the optical ballist cardiograph of the present invention, wherein FIG. 7A is a perspective view and FIG. 7B is a side view.

In this embodiment, 300 mm × 200
Acrylic plate of mm × 5mm (almost A4 size)
And a commercially available plastic optical fiber 1 having a diameter of 1 mm.
(Esca, Mitsubishi Rayon) and the stress concentrator 2 were fixed. Further, the upper plate 3 of the same material as the lower plate 4 was placed and fixed to form a sandwich structure. The light emitting element 5 attached to one end of the optical fiber 1 is a red semiconductor laser (oscillation wavelength 670 nm, light output 5 mW, Sanyo Electric Co., Ltd.
DL-3149-056), and a phototransistor (Toshiba Corporation TPS601) was used as the light receiving element 6 attached to the other end of the optical fiber 1. The mounting jig 12 for the light emitting element 5 and the light receiving element 6 is fixed to the lower plate 4,
Prevented noise contamination.

The signal (BCG signal) from the light receiving element 6 is
Only the variation was amplified by an AC amplifier (not shown) having an amplification factor of 3000 to 30000 via the electric cable 7, and was taken into a computer (not shown) at a sampling frequency of 200 Hz and a resolution of 12 bits. BACS at the same time
The finger plethysmogram was measured using (Computer Convenience Co., Ltd.), and synchronously captured. The connection time for the measurement was 35 seconds.

The measurement was carried out with the subject sitting on the upper plate 3 of the apparatus constructed as described above. FIG. 8 shows B at that time.
The measurement results of the CG signal W1 and the finger plethysmogram W2 are shown. B
The CG signal W1 has a wave having the same cycle as the pulse wave signal W2,
It can be seen that a higher frequency component exists. This BC
The G signal W1 is considered to correspond to the waveform of FIG.

FIGS. 9 and 10 show the results of FFT (fast Fourier transform) analysis of the BCG signal and the fingertip plethysmogram, respectively. From these analysis results, it can be seen that a peak corresponding to the pulse exists slightly above 1 Hz. The position of this peak is exactly the same in FIGS. 9 and 10, indicating that the pulse can be measured with the BCG signal.

FIG. 11 shows the cross-correlation between the BCG signal and the finger plethysmogram. The cross-correlation shows large amplitude and clear periodicity. This indicates that the BCG signal and the fingertip plethysmogram have the same periodicity, but it can also be seen that they are not exactly the same. This may be due to the existence of a number of extreme values corresponding to the BCG signal waveform of FIG.

In the above-described embodiment, an example is shown in which an optical fiber is used as the light-transmitting solid. However, the present invention is not limited to the optical fiber, and a similar rod-shaped light-transmitting solid made of glass or plastic may be used. Is obtained.

FIG. 12 shows a second embodiment of the present invention. In this embodiment, for example, one (FIG. 12 (a)) or a plurality of (FIG. 12 (b)) ridges 4a as light transmission paths are formed on the upper surface of an acrylic lower plate 4, and the ridges 4a are formed. The light-emitting element 5 is attached to one end, and the light-receiving element 6 is attached to the other end, and the upper plate 3 is mounted and fixed thereon. When a patient or a subject is placed on the upper plate 3 and the body movement is measured, the body movement
Therefore, a change in the amount of transmitted light due to the stress appears on the light receiving element 6.

FIG. 13 shows a third embodiment of the present invention. In this embodiment, a rectangular plate-like mat 8 is formed of a flexible and translucent solid, and at a longitudinal end,
The light emitting element unit 9 and the light receiving element unit 10 are attached. The light emitting element unit 9 is provided with a plurality of light emitting elements 5, and the light receiving element unit 10 is provided with the light receiving element 6 at a position facing the light emitting element 5. When a stress is applied to the mat 8, the amount of transmitted light changes due to a distortion corresponding to the magnitude of the stress, so that the body movement can be measured. Further, since a plurality of light emitting elements and light receiving elements are provided, it is possible to specify a position where a stress is applied.

[0046]

As described above, according to the present invention, the following effects can be obtained.

1) A light-transmitting solid on which a patient or a subject is placed, and means for measuring a change in the amount of light transmitted through the light-transmitting solid caused by body movement of the patient or the subject. With the provision, since the structure is simple, the size can be reduced to, for example, A4 size or less. Therefore, it is also possible to measure the subject while sitting on the chair.

2) Since it has a simple and sturdy structure, anyone can operate it and use it for home care.

3) Since light is used, there is no danger of electric shock or the like, and there is no fear that noise is mixed in the optical signal.
Further, since the optical-electrical change of the signal can be performed by a monitor (measurer), there is no possibility of causing noise in other devices.

4) In order to amplify the load applied to the translucent solid, a body for detecting the motion of the body is provided separately from or integrally with the upper and lower plates to partially contact the translucent solid. Can be improved.

5) When used for a bed, the position of the patient can be specified by using a plurality of translucent solids (optical fibers).

[Brief description of the drawings]

FIG. 1 is a waveform diagram showing an example of a BCG signal.

FIG. 2 is an explanatory diagram showing a first example of how to apply a stress to an optical fiber.

FIG. 3 is a perspective view showing a first example of a sensor.

FIG. 4 is an explanatory diagram showing a second example of how to apply a stress to an optical fiber.

FIG. 5 is a plan view and a front view showing a second example of the sensor.

FIG. 6 is a plan view and an enlarged front view showing a second example of the sensor.

FIG. 7 is a perspective view and a side view showing the first embodiment of the present invention.

FIG. 8 is a waveform chart showing a BCG signal and a fingertip plethysmogram.

FIG. 9 is a power spectrum of a BCG signal.

FIG. 10 is a power spectrum of a finger plethysmogram.

FIG. 11 is a cross-correlation diagram between a BCG signal and a finger plethysmogram.

FIG. 12 is a perspective view showing a second embodiment of the present invention.

FIG. 13 is a perspective view showing a third embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical fiber 2 stress concentrator 3 upper plate 4 lower plate 4 a ridge 5 light emitting element 6 light receiving element 7 electric cable 8 mat 9 light emitting element unit 10 light receiving element unit 11 core material 12 jig

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasunobu Noto 3-6-1, Hakata-ekimae, Hakata-ku, Fukuoka, Fukuoka F-term (reference) 2F051 AA17 AB03 4C017 AA10 AA14 AA20 AC26 BC07

Claims (6)

[Claims] 1. A light-transmitting solid on which a patient or a subject is placed, and means for measuring a change in the amount of light transmitted through the light-transmitting solid caused by body movement of the patient or the subject. An optical ballist cardiograph equipped with: 2. The optical ballist cardiograph according to claim 1, wherein the translucent solid is sandwiched between upper and lower rigid plates. 3. The optical ballist cardiograph according to claim 2, wherein the translucent solid has a rod-like structure for concentrating stress. 4. The optical ballist cardiograph according to claim 3, wherein the light-transmitting rod is an optical fiber. 5. The translucent solid according to claim 1, further comprising a stress concentrator that partially presses the translucent solid to amplify a load applied to the translucent solid. Optical ballist cardiograph as described. 6. The optical ballistic cardiograph according to claim 5, wherein the stress concentrator is formed on at least one of the inner surfaces of the upper and lower plates as a protrusion or a ridge contacting the optical fiber.