Patent ID: 12193829

DETAILED DESCRIPTION OF THE DISCLOSURE

A swallowing analyzing system according to an embodiment of the present disclosure is described below in detail with reference to the accompanying drawings.

FIG.1toFIG.5illustrate a swallowing analyzing system S according to the embodiment of the present disclosure. The swallowing analyzing system S includes a swallowing sensor1and a swallowing analyzer30. The swallowing sensor1includes a sensor portion2configured to detect swallowing of the subject101(human body), and a body20configured to process signals outputted from the sensor portion2.

For example, the sensor portion2as a whole has a rectangular shape and is located on one end side of the swallowing sensor1in a vertical direction (upper side inFIG.3). As illustrated inFIG.2, the sensor portion2includes a piezoelectric film sensor3, an insulating film7, and shield films8and9. As illustrated inFIG.1, the sensor portion2is located within a range of movement of thyroid cartilage103, which occurs along with swallowing, and is attached to the skin of the anterior neck region102of the subject101.

The jawbone104is located above the thyroid cartilage103and the breastbone105is located below the thyroid cartilage103. A pair of the carotid arteries106are located on right and left sides of the thyroid cartilage103. The sensor portion2is arranged within a range in which the sensor portion2does not overlap the jawbone104, the breastbone105, and the carotid arteries106. The sensor portion2is deformed by displacement of the thyroid cartilage103along with swallowing of the subject101to detect movement of the thyroid cartilage103.

The piezoelectric film sensor3is an example of a piezoelectric element. The piezoelectric film sensor3is located inside the sensor portion2. The piezoelectric film sensor3is formed into a film shape and generates electric signals (electric charges) depending on its deformation.

As illustrated inFIG.3, the piezoelectric film sensor3includes a plurality of (for example, two) sensing portions3A and3B (sensing regions). The number of sensing portions is not limited to two and may be three or more but is generally about two to four. The number of sensing portions may be one.

The sensing portions3A and3B are arrayed in a longitudinal direction of the neck region (vertical direction) in a state in which the piezoelectric film sensor3is attached to the anterior neck region102of the subject101. Specifically, the sensing portions3A and3B are arranged in the vertical direction across the thyroid cartilage103. Therefore, the upper sensing portion3A is arranged above the thyroid cartilage103. The lower sensing portion3B is arranged below the thyroid cartilage103. The sensing portions3A and3B are electrically isolated from each other and individually output signals (analog signals S1aand S2a).

As illustrated inFIG.3, a lateral dimension L1of each of the sensing portions3A and3B is desirably, for example, 5 mm or more and 50 mm or less. A vertical dimension L2of each of the sensing portions3A and3B is desirably, for example, 5 mm or more and 15 mm or less. The total vertical dimension of the plurality of sensing portions3A and3B, that is, a vertical dimension L3of the entire piezoelectric film sensor3is desirably, for example, 20 mm or more and 45 mm or less. The lateral dimension L1, the vertical dimension L2, and the like of the sensing portions3A and3B are set in consideration of the following matters.

In one swallowing action, the thyroid cartilage103ascends by about 20 mm from a position before the swallowing action, moves forward, and then descends back to the original position (seeFIG.6toFIG.9). Therefore, the vertical dimension L3of the piezoelectric film sensor3is set to 20 mm or more. If the maximum of four sensing portions are assumed, the vertical dimension L2of one sensing portion is preferably 5 mm or more.

In addition, the movement of the thyroid cartilage103needs to fall out of a range of one sensing portion. Therefore, the vertical dimension L2of one sensing portion is set to, for example, 15 mm or less as a value smaller than 20 mm.

Further, the distance from the thyroid cartilage103to the jawbone104is about 50 mm depending on the orientation of the face. The distance from the thyroid cartilage103to the breastbone105below the thyroid cartilage103is about 45 mm. Therefore, the vertical dimension of the entire swallowing sensor1including the piezoelectric film sensor3and the body20is set to 95 mm or less. Thus, an attachment member10for fixing the piezoelectric film sensor3and the body20is arrangeable so as not to overlap the jawbone104and the breastbone105in the vertical direction. Accordingly, it is possible to suppress detection of vibration noise and to reduce the occurrence of a case in which the attachment member10peels off.

Upward displacement of the skin around the breastbone105during an action of turning the face upward is smaller than that of the skin around the thyroid cartilage103. Thus, if the region where the piezoelectric film sensor3is attached reaches the vicinity of the breastbone105, the accuracy of distinction between the action of turning the face upward and swallowing decreases. The body20including amplification circuits21A and22A and the like is harder and heavier than the piezoelectric film sensor3. Therefore, the body20is desirably arranged below or on the side of the piezoelectric film sensor3so as not to hinder the deformation of the flexible piezoelectric film sensor3. If the body20is attached to the skin and if the body20overlaps the breastbone105, the accuracy of distinction between the action of turning the face upward and swallowing decreases as well. The size of the body20is about 15 mm or more due to the sizes of internal components such as a battery26.

Further, the skin around the jawbone104is likely to sag. In particular, the skin of elderly people sags greatly. If the piezoelectric film sensor3is attached to the sagging skin, it is difficult to transfer the movement of the thyroid cartilage103to the piezoelectric film sensor3due to the sag of the skin. Therefore, it is desirable to avoid attaching the piezoelectric film sensor3around the jawbone104. Thus, the vertical dimension L3of the entire piezoelectric film sensor3is preferably set to 45 mm or less.

In this structure, the swallowing sensor1is arranged so that the center of the piezoelectric film sensor3overlaps the laryngeal prominence that is a projection of the thyroid cartilage103and the plurality of sensing portions3A and3B are arrayed in the vertical direction. Assuming this arrangement, the lateral dimension of the piezoelectric film sensor3(sensing portions3A and3B) is set to 5 mm or more.

The relative distance between the sternocleidomastoid muscles located on right and left of the thyroid cartilage103is about 60 to 100 mm. Upward displacement of the skin on the sternocleidomastoid muscles during the action of turning the face upward is smaller than that of the skin around the thyroid cartilage103. Thus, if the region where the piezoelectric film sensor3is attached reaches the vicinity of the sternocleidomastoid muscles, the accuracy of distinction between the action of turning the face upward and swallowing decreases. Therefore, the lateral dimension of the piezoelectric film sensor3is set to 50 mm or less so that the piezoelectric film sensor3does not overlap the skin on the sternocleidomastoid muscles.

As illustrated inFIG.2, the piezoelectric film sensor3(sensing portions3A and3B) is formed by using a piezoelectric film4. Specifically, the piezoelectric film sensor3is formed of the piezoelectric film4and first and second electrode films5and6.

The piezoelectric film4is formed by forming a thin piezoelectric film4B on a base4A made of an insulating material. For example, a polyimide film is used for the base4A but other resin films made of polyethylene terephthalate (PET) or the like may be used. Polyimide has a high heat resistance as the resin film and is therefore resistant to a temperature increase during film formation and also resistant to a temperature increase caused by soldering, thermocompression bonding, or the like for attaining electrical connection. Therefore, polyimide is preferably used as the material for the base4A.

For example, aluminum nitride (AlN) is used for the thin piezoelectric film4B but an inorganic material such as zinc oxide (ZnO), lead zirconate titanate (PZT), or potassium sodium niobate (KNN) may be used. Further, a piezoelectric polymer film made of polyvinylidene difluoride (PVDF) or polylactide (PLLA) may be used as the piezoelectric film4.

The first and second electrode films5and6are provided on both sides (front side and back side) of the piezoelectric film sensor3in its thickness direction. The first electrode film5is provided on the front surface (one principal surface) of the piezoelectric film4while covering the thin piezoelectric film4B of the piezoelectric film4. The second electrode film6is provided on the back surface (other principal surface) of the piezoelectric film4while covering the base4A of the piezoelectric film4.

A metal material such as gold (Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), or titanium (Ti) is used for the first and second electrode films5and6but a conductive material such as indium tin oxide (ITO) may be used, or carbon or the like may be used. The first and second electrode films5and6detect the analog signal S1aor S2adepending on the deformation of the piezoelectric film sensor3(sensing portion3A or3B) and output the detected analog signal S1aor S2ato the amplification circuit21A or22A of the body20. In this case, minute deformation is detected and therefore the first and second electrode films5and6are preferably soft and thin.

The insulating film7covers the first electrode film5. Therefore, the first electrode film5is sandwiched between the insulating film7and the thin piezoelectric film4B of the piezoelectric film sensor3. For example, the insulating film7is formed into an elastically deformable film shape by using an insulating soft resin material. The insulating film7covers the entire first electrode film5to insulate the first electrode film5from the shield films8and9.

The shield films8and9are located on an outer side portion (outer shell) of the sensor portion2and are provided on both sides of the piezoelectric film sensor3and the insulating film7in the thickness direction. That is, the shield films8and9cover the piezoelectric film sensor3and the insulating film7from both sides in the thickness direction. The shield films8and9only need to have conductivity, and a film obtained by forming a thin metal film on a resin film, a conductive resin film, a conductive fabric (nonwoven fabric) produced by using conductive yarns, or the like is suited to each of the shield films8and9. Each of the shield films8and9is formed into an elastically deformable film shape. The shield films8and9shield the piezoelectric film sensor3from external electromagnetic noise. The shield films8and9are connected to a ground (GND) of an electric circuit provided in the body20.

The attachment member10is located on one side of the swallowing sensor1in the thickness direction. For example, the attachment member10is formed into a rectangular shape by using a double coated tape having biocompatibility. The attachment member10attaches the swallowing sensor1to the surface of the anterior neck region102of the subject101.

The body20is located on the other end side of the swallowing sensor1in the vertical direction (the lower side inFIG.1). The body20is driven by the internal battery26and separates a signal outputted from the piezoelectric film sensor (piezoelectric element) into a displacement signal that is a low frequency component and a sound signal that is a high frequency component. Then, the body20makes determination for swallowing detection in real time based on the displacement signal. When the swallowing is detected, the body20extracts data on the displacement signal and the sound signal during the detected swallowing and wirelessly outputs the data to the outside.

As illustrated inFIG.4, the body20includes pre-processing units21and22, a signal processing unit23(such as a processor), a wireless communication module25, and the battery26. In this case, the body20is removably connected to the sensor portion2by using a connector (not illustrated) or the like and is attached to a lower end side of the sensor portion2attached to the subject101(seeFIG.3). Thus, if only the sensor portion2is damaged or soiled, only the sensor portion2can be replaced by being removed from the body20.

The pre-processing units21and22are provided for a plurality of systems (for example, two systems) depending on the number of the sensing portions3A and3B of the piezoelectric film sensor3. The pre-processing units21and22perform amplification, filtering, and A/D conversion as pre-processing for the analog signals S1aand S2aoutputted from the piezoelectric film sensor3.FIG.1andFIG.3exemplify the case in which the body20is arranged below the sensor portion2. The present disclosure is not limited thereto and the body20may be arranged on the side (right or left side) of the sensor portion2.

The pre-processing unit21includes the amplification circuit21A, a low pass filter21B (hereinafter referred to as LPF21B), a high pass filter21C (hereinafter referred to as HPF21C), and A/D converters21D and21E. An input side of the pre-processing unit21is connected to the sensing portion3A of the piezoelectric film sensor3and an output side of the pre-processing unit21is connected to the signal processing unit23.

An input side of the amplification circuit21A is connected to the sensing portion3A of the piezoelectric film sensor3. The amplification circuit21A amplifies the analog signal S1aoutputted from the first and second electrode films5and6of the sensing portion3A. The LPF21B and the HPF21C separate the amplified analog signal S1ainto a low frequency component S1La (displacement speed) and a high frequency component S1Ha (sound) with respect to, for example, several tens of hertz to 100 Hz.

The LPF21B passes the low frequency component S1La having a frequency lower than a cutoff frequency in the amplified analog signal S1aand attenuates a component having a frequency higher than the cutoff frequency. The low frequency component S1La includes a displacement component associated with a displacement speed of the thyroid cartilage103along with swallowing. To make swallowing determination, the low frequency component S1La suffices if the low frequency component S1La is a signal of several tens of hertz or less. Therefore, the cutoff frequency of the LPF21B is set to, for example, about several tens of hertz to 100 Hz.

The HPF21C passes the high frequency component S1Ha having a frequency higher than a cutoff frequency in the amplified analog signal S1aand attenuates a component having a frequency lower than the cutoff frequency. The high frequency component S1Ha includes a sound component associated with the sound generated during the swallowing action. Therefore, the high frequency component S1Ha includes at least a signal having a frequency up to about 3 kHz. The cutoff frequency of the HPF21C is set to, for example, about several tens of hertz to 100 Hz.

The cutoff frequency of the HPF21C may be set to a value (for example, about 100 to 500 Hz) higher than the cutoff frequency of the LPF21B within a range in which a necessary sound component such as swallowing sound can be obtained.

The A/D converter21D converts the low frequency component S1La of the analog signal S1a, which is outputted from the LPF21B, into a digital signal S1Ld. To make the swallowing determination, the displacement signal (displacement speed signal) having a frequency component of several tens of hertz or less is sufficient. Therefore, the sampling frequency of the A/D converter21D is set to a frequency (for example, about 100 Hz to 1000 Hz) sufficiently higher than that of the low frequency component S1La including the displacement signal of several tens of hertz or less. Since the sampling frequency of the A/D converter21D is applied to the displacement signal, the sampling frequency of the A/D converter21D is set to a value (low sampling frequency) lower than a sampling frequency of the A/D converter21E applied to the sound signal.

The A/D converter21E converts the high frequency component S1Ha of the analog signal S1a, which is outputted from the HPF21C, into a digital signal S1Hd. To obtain the sound signal, a frequency component having a frequency up to about 3 kHz at the minimum is required for a sampling frequency. Therefore, the sampling frequency of the A/D converter21E needs to be about 10 kHz. Thus, the sampling frequency of the A/D converter21E is set to a value (high sampling frequency) higher than the sampling frequency of the A/D converter21D.

The pre-processing unit22is structured substantially similarly to the pre-processing unit21. Therefore, the pre-processing unit22includes the amplification circuit22A, a low pass filter22B (hereinafter referred to as LPF22B), a high pass filter22C (hereinafter referred to as HPF22C), and A/D converters22D and22E that are substantially similar to the amplification circuit21A, the LPF21B, the HPF21C, and the A/D converters21D and21E. An input side of the pre-processing unit22is connected to the sensing portion3B of the piezoelectric film sensor3and an output side of the pre-processing unit22is connected to the signal processing unit23.

The amplification circuit22A amplifies the analog signal S2aoutputted from the sensing portion3B. The LPF22B and the HPF22C separate the amplified analog signal S2ainto a low frequency component S2La (displacement speed) and a high frequency component S2Ha (sound). The A/D converter22D converts the low frequency component S2La into a digital signal S2Ld. The A/D converter22E converts the high frequency component S2Ha into a digital signal S2Hd.

The signal processing unit23constitutes a swallowing determination unit configured to make determination for the swallowing action. The signal processing unit23is provided in the body20and is driven by electric power supplied from the battery26. An input side of the signal processing unit23is connected to the A/D converters21D,21E,22D, and22E. An output side of the signal processing unit23is connected to a memory24and the wireless communication module25. For example, the signal processing unit23includes a microcomputer (CPU). The signal processing unit23makes determination for swallowing of the subject101based on the digital signals S1Ld and S2Ld. When the determination is made for swallowing of the subject101, the signal processing unit23extracts displacement components (digital signals S1Ld and S2Ld) and sound components (digital signals S1Hd and S2Hd) during the detected swallowing and wirelessly outputs the components by using the wireless communication module25. In addition, the signal processing unit23stores the pieces of signal data during the swallowing in the memory24.

For example, data during swallowing can be set within a data range in which a change in the signal strength of a displacement speed component exceeds a threshold. For example, the data during swallowing may be set within a data range corresponding to a change pattern that matches with a preset reference swallowing pattern (data range from a swallowing start point to a swallowing end point in the reference pattern). Further, the data during swallowing may be set within a data range in which pieces of data during a predetermined time are added prior to and subsequent to one of the two data ranges described above.

The extracted digital signals S1Ld, S2Ld, S1Hd, and S2Hd are wirelessly outputted by using the wireless communication module25. In addition, the extracted digital signals S1Ld, S2Ld, S1Hd, and S2Hd are stored in the memory24(storage unit) provided inside the body20. The memory24may be a volatile memory or a non-volatile memory.

The wireless communication module25is provided in the body20and is connected to the signal processing unit23. The wireless communication module25includes a modulation circuit configured to modulate signals in conformity with various wireless communication standards, and a transmission unit configured to transmit the modulated signals (neither of which is illustrated). The wireless communication module25outputs the digital signals S1Ld, S2Ld, S1Hd, and S2Hd during the swallowing, which are extracted by the signal processing unit23, toward the swallowing analyzer30that is an external device. The swallowing analyzer30analyzes a swallowing function based on the received data.

For example, Bluetooth (registered trademark), Wi-Fi (registered trademark), ZigBee (registered trademark), ANT (registered trademark), UWB, or NFC (near-field communication) is applicable to a communication scheme of the wireless communication module25. In particular, Bluetooth Low Energy (hereinafter referred to as BLE) having low power consumption is preferably used as the communication scheme of the wireless communication module25. However, BLE is not suited to application in which signals having a large data capacity, such as a sound signal, are transmitted continuously and constantly. To reduce power consumption by using BLE, it is necessary to minimize the transmitted data amount.

Therefore, it is important that only data during swallowing, which is necessary for the swallowing function analysis, be transmitted while being extracted from the sound signal having a large data amount. In consideration of this point, the signal processing unit23makes determination for swallowing detection in real time based on the displacement signal and, when the swallowing is detected, extracts data on the displacement signal and the sound signal during the detected swallowing.

If the sound signal having a large data amount is analyzed constantly, power consumption increases compared with the analysis of the displacement signal (displacement speed signal). The signal processing unit23makes the swallowing determination based on the displacement signal (displacement speed signal) having a small data amount. Therefore, it is possible to reduce power consumption other than that during communication.

The battery26is provided in the body20and is connected to the pre-processing units21and22, the signal processing unit23, the wireless communication module25, and the like. The battery26constitutes a power supply configured to supply drive voltages (electric power) to the amplification circuits21A and22A, the A/D converters21D,21E,22D, and22E, the signal processing unit23, the wireless communication module25, and the like.

The swallowing analyzer30is structured by an external device such as a PC (computer), a portable terminal, a storage device, or a server (none of which is illustrated). The swallowing analyzer30makes determination for the swallowing function by receiving the data on the displacement signal and the sound signal during the swallowing, which is transmitted from the wireless communication module25. Specifically, the swallowing analyzer30makes determination for the swallowing action based on the displacement signal and determines whether swallowing dysfunction such as a slowdown in swallowing reflex or an abnormality of swallowing timing is present based on the sound signal obtained at the time of determination for the swallowing action.

The swallowing analyzing system S has the structure described above. Next, swallowing detection processing in which the signal processing unit23detects swallowing of the subject101is described with reference toFIG.5. The swallowing detection processing is repeatedly executed in each predetermined period while the swallowing sensor1is driven.

In Step1, the low frequency components S1La and S2La outputted from the LPFs21B and22B are first converted into the digital signals S1Ld and S2Ld by the A/D converters21D and22D. The signal processing unit23acquires the digital signals S1Ld and S2Ld, which are pieces of data on displacement signals obtained through conversion at a low sampling frequency of, for example, about 100 Hz.

The absolute values of the displacement speeds (digital signals S1Ld and S2Ld) increase along with movement of the throat before the swallowing. Therefore, determination is subsequently made in Step2as to whether the absolute values of the displacement speeds are equal to or higher than a predetermined threshold ST based on the digital signals S1Ld and S2Ld that are the displacement signals. When the absolute values of the displacement speeds are lower than the threshold ST, an action before the swallowing is not detected. Therefore, the determination is “NO” in Step2and the processing returns to Step1. When the absolute values of the displacement speeds exceed the predetermined threshold ST, the action before the swallowing is detected. Therefore, the determination is “YES” in Step2and the processing proceeds to Steps3and4.

In Step3, changes in the signal strengths of the sensing portions3A and3B are acquired individually. Specifically, waveform patterns of temporal changes in the digital signals S1Ld and S2Ld including the displacement signals are acquired. In Step4, the high frequency components S1Ha and S2Ha outputted from the HPFs21C and22C are converted into the digital signals S1Hd and S2Hd by using the A/D converters21E and22E. Then, the signal processing unit23starts to acquire the digital signals S1Hd and S2Hd including sound signals.

In Step5, determination is subsequently made as to whether swallowing occurs based on whether the change patterns of the digital signals S1Ld and S2Ld and timings of changes in the sensing portions3A and3B (for example, maximum signal strengths) fall within predetermined ranges.

FIG.13illustrates an example of the waveform patterns during the swallowing. As illustrated inFIG.13, a sharp downward peak Pa1of the upper sensing portion3A and a sharp upward peak Pb1of the lower sensing portion3B occur within a predetermined time around 1.5 seconds during the swallowing. Then, a slightly broad upward peak Pa2of the upper sensing portion3A and a slightly broad upward peak Pb2of the lower sensing portion3B occur within a predetermined time around 1.6 seconds. Further, two gentle downward peaks Pb3and Pb4occur within a predetermined time around 1.7 to 2.1 seconds. Therefore, the signal processing unit23determines whether the swallowing occurs based on whether all the peaks Pa1, Pa2, and Pb1to Pb4occur.

The peaks Pa1and Pb1correspond to upward movement (elevation) of the laryngeal prominence. The peaks Pa2and Pb2correspond to forward movement (advance) of the laryngeal prominence. The peaks Pb3and Pb4correspond to movement of the laryngeal prominence to the original position.

To obtain the sharp downward peak Pa1of the upper sensing portion3A and the sharp upward peak Pb1of the lower sensing portion3B, it is desirable that the arrangement distance between the upper sensing portion3A and the lower sensing portion3B be approximated to the size of the laryngeal prominence in the longitudinal direction of the neck region (about 10 to 35 mm) so that the movement of the thyroid cartilage103can easily be grasped on the skin, and the upper sensing portion3A and the lower sensing portion3B can be arranged vertically across the laryngeal prominence. When the plurality of sensing portions3A and3B are arranged in this manner, determination can be made while distinguishing the upward movement and the forward movement of the laryngeal prominence.

FIG.13illustrates the example of the waveform patterns during the swallowing. The number of peaks or the timings of peaks may differ depending on, for example, the attachment position of the piezoelectric film sensor3, differences in measurement conditions, individual differences, or the degree of dysphagia. Therefore, there is no need to use all the peaks Pa1, Pa2, and Pb1to Pb4for the swallowing determination. For example, only the peaks Pa1and Pa2, which are characteristic and easy to detect, may be used. For example, a peak of the upper sensing portion3A may also be detected at a time corresponding to the peak Pb3or Pb4of the lower sensing portion3B. Therefore, the swallowing determination may be made in consideration of other peaks as well as the peaks Pa1, Pa2, and Pb1to Pb4.

Further, the swallowing determination is not limited to the displacement signal, and the sound signal may be taken into consideration. Specifically, determination of whether the swallowing occurs may be made in consideration of, for example, whether swallowing sound is included in the sound signal in addition to whether the determination condition on the displacement signal described above is satisfied.

When the determination condition described above is not satisfied, determination is not made that the swallowing occurs. Therefore, the determination is “NO” in Step5and the processing returns to Step1. When the determination condition described above is satisfied, determination is made that the swallowing occurs. Therefore, the determination is “YES” in Step5and the processing proceeds to Step6, in which only data during the swallowing is extracted.

For example, the data during the swallowing corresponds to pieces of data on the digital signals S1Ld, S2Ld, S1Hd, and S2Hd from a start point to an end point, assuming that the start point is a timing when the action before the swallowing is detected in Step2(timing when the absolute values of the displacement speeds exceed the predetermined threshold ST) and the end point is a timing when a predetermined time elapses from the determination in Step5that the swallowing occurs.

The predetermined time is set as appropriate in consideration of, for example, individual differences in waveform data among the subjects101. Further, there is no need to extract all the pieces of data for which acquisition is started in Step2. For example, the timing of the determination in Step5that the swallowing occurs may be set as a reference and data within predetermined time ranges prior to and subsequent to the timing may be extracted. In Step7, the extracted data is subsequently transmitted to the swallowing analyzer30that is the external device by using the wireless communication module25. In addition, the extracted data is stored in the internal memory24. If the swallowing analyzer30can securely receive the wirelessly transmitted data, the processing of storing the data in the internal memory24may be omitted.

According to this embodiment, the body20makes determination for swallowing detection by using the displacement signal on the thyroid cartilage103. Therefore, the accuracy of swallowing determination increases. The body20makes determination for swallowing detection based on the displacement signal that is the low frequency component. Therefore, processing performance of high throughput is unnecessary for arithmetic processing in the determination for swallowing detection. Further, the body20includes the battery26and wirelessly outputs data. Therefore, power supply and data output cables are unnecessary. Thus, the weights of the cables are eliminated, thereby being capable of reducing the occurrence of a case in which the swallowing sensor1including the piezoelectric film sensor3and the body20peels off the skin due to the weight.

Further, the body20makes the swallowing determination by processing measurement data. Every time determination is made that the swallowing is detected, the body20extracts data on the signals (digital signals S1Ld, S2Ld, S1Hd, and S2Hd) during the swallowing and wirelessly outputs the data to the outside. Therefore, the wirelessly transmitted data is only the data during the swallowing. Thus, there is no need to continuously transmit a large amount of data. Accordingly, it is possible to reduce power consumption of, for example, the wireless communication module25and to use a small-size, low-height, and small-capacity battery as the internal battery26.

Further, the swallowing analysis is performed by the external swallowing analyzer30instead of the inside of the body20attached to the subject101. A PC, a terminal, or the like in which internal analysis processing is rewritable may be used as the swallowing analyzer30. The swallowing analysis method has not been established currently and may be revised later on. Even if the swallowing analysis method is revised, the revised analysis method can be applied easily.

Further, the body20acquires data on the displacement signal at a low sampling frequency and, when a change that satisfies a predetermined condition is detected in the data on the displacement signal, acquires data on the sound signal at a high sampling frequency. Therefore, the data amount is normally small and high-speed processing is unnecessary. Thus, the power consumption of the body20can be reduced. As a result, a small-capacity battery can be used as the internal battery26.

Further, when the displacement around the thyroid cartilage103starts to occur and a change that satisfies a predetermined condition (for example, the rate of change is equal to or higher than a threshold) starts to be detected in the data on the displacement signal, the body20acquires the data on the sound signal at the high sampling frequency. Therefore, the determination for swallowing detection can be made accurately by using not only the data on the displacement signal but also the data on the sound signal.

Further, the body20automatically extracts, from the displacement signal and the sound signal, only partial data with strong possibility of the swallowing involving the displacement around the thyroid cartilage103. For example, even in measurement during sleep, it is possible to exclude unnecessary data indicating that the swallowing does not occur. Thus, there is no need to extract the swallowing from long-time data through ex-post data analysis.

Further, the piezoelectric film sensor3is attached to the skin within the range of the movement of the thyroid cartilage103, which occurs along with the swallowing. Therefore, even if, for example, the thickness and the shape of the neck (neck region) differ among the subjects101, influence of the individual differences can be suppressed and the sensor can be used without being adjusted to many people.

Further, the piezoelectric film sensor3includes the plurality of sensing portions3A and3B in the longitudinal direction of the neck region and outputs the signals along with deformation of the plurality of sensing portions3A and3B. Therefore, the plurality of sensing portions3A and3B can output signals having different waveform patterns in response to the movement (upward movement and forward movement) of the thyroid cartilage103. By using the analog signals S1aand S2afrom the plurality of sensing portions3A and3B, the swallowing can be identified more easily than in a case in which a single sensing portion is used.

Further, the piezoelectric film sensor3is attached to the skin on the thyroid cartilage103and includes the plurality of sensing portions3A and3B in the longitudinal direction of the neck region. For example, at the time of nodding or other neck actions that do not cause a change in the relative position between the thyroid cartilage103and the skin on the thyroid cartilage103(action of vertically moving the head), the relative position between the thyroid cartilage103and the skin does not change. At the time of swallowing action, the relative position between the thyroid cartilage103and the skin changes.

This point is described in detail with reference toFIG.6toFIG.12. For example, in an oral stage illustrated inFIG.6, which is a period of a reference posture before the swallowing action, the subject101masticates food F and delivers the food F into the pharynx. At this time, the thyroid cartilage103is located at a position near the lower sensing portion3B out of the two sensing portions3A and3B.

In a subsequent pharyngeal stage, the subject101delivers the food F from the oral cavity to the pharynx. As illustrated inFIG.7, the thyroid cartilage103located under the lower sensing portion3B moves to a position under the upper sensing portion3A during the swallowing action. In a subsequent esophageal stage illustrated inFIG.8andFIG.9, the subject101delivers the food F from the pharynx to the esophagus. At this time, the respiratory tract is closed and therefore the food F does not enter the respiratory tract. The food F is delivered from the esophagus to the stomach.

During the swallowing action, waveform patterns differ between the displacement signal (low frequency component S2La) from the lower sensing portion3B and the displacement signal (low frequency component S1La) from the upper sensing portion3A. The output displacement speed components are maximum when the thyroid cartilage103moves upward (seeFIG.7). For example, when the thyroid cartilage103moves from the lower side to the upper side of the piezoelectric film sensor3as illustrated inFIG.10andFIG.11, the significant peaks Pa1and Pb1in opposite directions occur in the displacement signal from the lower sensing portion3B and the displacement signal from the upper sensing portion3A (seeFIG.13).

During the action of turning the face upward as illustrated inFIG.12, the thyroid cartilage103does not move from the position under the lower sensing portion3B. Therefore, the significant peaks are unlikely to occur in the output displacement speed components. Even if the significant peaks occur, the significant peaks in opposite directions do not occur in the displacement signal from the lower sensing portion3B and the displacement signal from the upper sensing portion3A. Since the displacement signals from the sensing portions3A and3B differ between the vertical movement of the neck and the swallowing action, erroneous detection along with the vertical movement of the neck can be suppressed.

FIG.10toFIG.12demonstrate that there is no significant difference between the swallowing action and the action of turning the face upward in terms of relative positional relationships of the thyroid cartilage103to a lateral neck portion A and a lower portion B of the anterior neck region102. During the swallowing action, the thyroid cartilage103is displaced upward but the lateral neck portion A and the lower portion B of the anterior neck region102are not substantially displaced. If the sensor is fixed to the neck region by putting a retaining band around the neck as disclosed in Patent Document 1, the thyroid cartilage103is displaced upward relative to the posterior neck region when the subject101turns the face upward. Therefore, it is difficult to distinguish the movement of the thyroid cartilage103under the skin through the swallowing action from the movement of the thyroid cartilage103relative to the posterior neck region through the vertical movement of the neck. Thus, it is desirable that the fixing range of the swallowing sensor1be the skin on the thyroid cartilage103and the skin within a narrow range around the thyroid cartilage103.

If the sensing region is a narrow range, the thyroid cartilage103falls out of the range of its sensing region when the thyroid cartilage103moves during the swallowing. Therefore, the swallowing sensor1covers the movement range of the thyroid cartilage103with the plurality of sensing portions3A and3B.

The swallowing sensor1includes the signal processing unit23configured to detect the movement of the thyroid cartilage103and make determination for the swallowing action based on the analog signals S1aand S2afrom the plurality of sensing portions3A and3B. The plurality of sensing portions3A and3B can output the analog signals S1aand S2ahaving different waveform patterns in response to the movement (upward movement and forward movement) of the thyroid cartilage103. Therefore, when the analog signals S1aand S2aare outputted from the plurality of sensing portions3A and3B, the signal processing unit23can detect the movement of the thyroid cartilage103and make determination for the swallowing action by comparing the features of the waveform patterns of the analog signals S1aand S2a.

Specifically, the signal processing unit23makes the swallowing determination by making determination for the upward movement and the forward movement of the laryngeal prominence based on the analog signals S1aand S2afrom the plurality of sensing portions3A and3B. Therefore, the signal processing unit23can make the swallowing determination depending on whether the peaks Pa1and Pb1associated with the upward movement of the laryngeal prominence and the peaks Pa2and Pb2associated with the forward movement of the laryngeal prominence occur in the analog signals S1aand S2a.

The piezoelectric film sensor3is formed by using the piezoelectric film4. Therefore, the sensing portions3A and3B can be formed thin and light and the movement of the larynx including the thyroid cartilage103is not hindered. Further, discomfort of the patient can be reduced. In addition, the weight of the piezoelectric film sensor3per the attachment area can be reduced and therefore the peeling of the piezoelectric film sensor3off the skin of the neck region can be suppressed.

The signal processing unit23makes determination for the swallowing action by using the displacement components (low frequency components S1La and S2La) of the analog signals S1aand S2aoutputted from the piezoelectric film sensor3. Since the signal frequencies of the displacement components are low, the signal processing unit23can make determination for the swallowing action by using the displacement components of the digital signals S1Ld and S2Ld whose sampling frequencies are low.

When the signal processing unit23determines that the swallowing occurs, the signal processing unit23extracts the displacement components (digital signals S1Ld and S2Ld of the low frequency components S1La and S2La) and the sound components (digital signals S1Hd and S2Hd of the high frequency components S1Ha and S2Ha) of the pieces of signal data during the detected swallowing and wirelessly outputs the components. The swallowing analyzer30makes determination for the swallowing function based on the pieces of data on the displacement signals and the sound signals during the swallowing. Therefore, it is also possible to detect, for example, abnormal noise frequently observed in a swallowing function abnormality. Thus, the determination accuracy of the swallowing function (dysphagia) is improved.

Further, the frequency component having a frequency up to about 3 kHz at the minimum is required for the sound component. Therefore, the sampling frequency needs to be about 10 kHz. Thus, the data amount becomes enormous when the sound component is measured for a long time. When the swallowing sensor1determines that the swallowing occurs, the swallowing sensor1extracts the displacement components and the sound components of the pieces of signal data during the detected swallowing and wirelessly outputs the components. Therefore, there is no need to wirelessly output the displacement components and the sound components of the pieces of signal data constantly. It is only necessary to extract the displacement components and the sound components of the pieces of signal data only when the swallowing determination is made. Thus, it is possible to reduce the occurrence of the case in which the acquired data becomes enormous compared with the case in which the pieces of signal data are wirelessly output constantly.

In the embodiment described above, the amplified analog signal is separated into the low frequency component and the high frequency component. The present disclosure is not limited thereto and the digital signal obtained through the AD conversion may be separated into the low frequency component and the high frequency component. Further, the analog signal before amplification may be separated into the low frequency component and the high frequency component.

In the embodiment described above, the piezoelectric film sensor3is exemplified as the piezoelectric element. The piezoelectric element need not have the film shape but may have a bulk shape (massive shape). Further, the piezoelectric material for the piezoelectric element is not particularly limited as long as the piezoelectric material is a substance having piezoelectricity. For example, a material containing, as a main component, a compound having a wurtzite structure or a composite oxide having a perovskite structure (ABO3) (perovskite composite oxide) may be used as the piezoelectric material for the piezoelectric element.

Examples of the compound having the wurtzite structure include aluminum nitride, gallium nitride, indium nitride, beryllium oxide, zinc oxide, cadmium sulfide, zinc sulfide, and silver iodide.

For example, at least one kind of element selected from among lead (Pb), barium (Ba), calcium (Ca), strontium (Sr), lanthanum (La), lithium (Li), and bismuth (Bi) may be employed as an A site of the perovskite structure (ABO3) of the perovskite composite oxide. For example, at least one kind of element selected from among titanium (Ti), zirconium (Zr), zinc (Zn), nickel (Ni), magnesium (Mg), cobalt (Co), tungsten (W), niobium (Nb), antimony (Sb), tantalum (Ta), and iron (Fe) is employed as a B site of the perovskite structure (ABO3).

Specific examples of the perovskite composite oxide include lead zirconate titanate [Pb(Zr, Ti)O3] (referred to also as PZT), potassium tantalate niobate [K(Ta, Nb)O3], barium titanate (BaTiO3), and (Pb, La)(Zr, Ti)O3[such as lead titanate (PbTiO3)].

In the embodiment described above, only the data on the displacement signal is acquired at the low sampling frequency at the start of operation of the swallowing sensor1to reduce power consumption. The present disclosure is not limited thereto. For example, the data on the displacement signal and the sound signal may be acquired at the high sampling frequency from the start of operation of the swallowing sensor1.

Next, description is made of the disclosure incorporated in the embodiment described above. The swallowing analyzing system according to the present disclosure includes the piezoelectric element located within the range of the movement of the thyroid cartilage, which occurs along with the swallowing, and attached to the skin of the anterior neck region; the swallowing detector to be driven by the internal battery, configured to make determination for swallowing detection in real time based on the displacement signal that is the low frequency component of the signal outputted from the piezoelectric element, and configured to extract, when the swallowing is detected, the data on the signal during the detected swallowing and wirelessly output the data to the outside; and the swallowing analyzer configured to make determination for the swallowing function by receiving the data on the signal during the swallowing.

According to the present disclosure, the swallowing detector makes determination for swallowing detection by using the displacement signal on the thyroid cartilage. Therefore, the accuracy of swallowing determination increases. The swallowing detector makes determination for swallowing detection based on the displacement signal that is the low frequency component. Therefore, processing performance of high throughput is unnecessary for arithmetic processing in the determination for swallowing detection. Further, the swallowing detector includes the battery, and wirelessly outputs the data. Therefore, power supply and data output cables are unnecessary. Thus, the weights of the cables are eliminated, thereby being capable of reducing the occurrence of a case in which the piezoelectric element and the swallowing detector peel off the skin due to the weight.

Further, the swallowing detector makes the swallowing determination by processing measurement data. Every time determination is made that the swallowing is detected, the swallowing detector extracts the data on the signal during the swallowing and wirelessly outputs the data to the outside. Therefore, the wirelessly transmitted data is only the data during the swallowing. Thus, there is no need to continuously transmit a large amount of data. Accordingly, it is possible to reduce power consumption of, for example, the communication module and to use a small-size, low-height, and small-capacity battery as the internal battery.

Further, the swallowing analysis is performed by the external swallowing analyzer instead of the inside of the swallowing detector attached to the subject. A computer, a terminal, or the like in which internal analysis processing is rewritable may be used as the swallowing analyzer. Even if the swallowing analysis method is revised, the revised analysis method can be applied easily.

In the present disclosure, the swallowing detector acquires the displacement signal at the low sampling frequency. When a change that satisfies the predetermined condition is detected in the data on the displacement signal, the swallowing detector starts to acquire, at the high sampling frequency, the sound signal that is the high frequency component of the signal outputted from the piezoelectric element. When the swallowing is detected based on the displacement signal, the swallowing detector extracts the data on the displacement signal and the sound signal during the detected swallowing and wirelessly outputs the data to the outside.

According to the present disclosure, the data on the displacement signal is acquired at the low sampling frequency and, when the change that satisfies the predetermined condition is detected in the data on the displacement signal, the data on the sound signal is acquired at the high sampling frequency. Therefore, the data amount is normally small and high-speed processing is unnecessary. Thus, power consumption can be reduced. As a result, a small-capacity battery can be used as the internal battery.

Further, when the displacement around the thyroid cartilage starts to occur and a change that satisfies the predetermined condition (for example, the rate of change is equal to or higher than the threshold) starts to be detected in the data on the displacement signal, the data on the sound signal is acquired at the high sampling frequency. Therefore, the determination for swallowing detection can be made accurately by using not only the data on the displacement signal but also the data on the sound signal.

Further, only partial data with strong possibility of the swallowing involving the displacement around the thyroid cartilage is automatically extracted from the displacement signal and the sound signal. For example, even in measurement during sleep, it is possible to exclude unnecessary data indicating that the swallowing does not occur. Thus, there is no need to extract the swallowing from long-time data through ex-post data analysis.

In the present disclosure, the piezoelectric element is located within the range of the movement of the thyroid cartilage, which occurs along with the swallowing, is attached to the skin of the anterior neck region, includes the plurality of sensing portions in the longitudinal direction of the neck region, and individually outputs the signals along with the deformation of the plurality of sensing portions. The swallowing detector detects the movement of the thyroid cartilage and makes determination for the swallowing action based on the signals from the plurality of sensing portions.

According to the present disclosure, the piezoelectric element includes the plurality of sensing portions in the longitudinal direction of the neck region and outputs the signals along with the deformation of the plurality of sensing portions. Therefore, the plurality of sensing portions can output signals having different waveform patterns in response to the movement (upward movement and forward movement) of the thyroid cartilage. By using the signals from the plurality of sensing portions, the swallowing can be identified more easily than in the case in which a single sensing portion is used.

Further, the piezoelectric element is attached to the skin on the thyroid cartilage and includes the plurality of sensing portions in the longitudinal direction of the neck region. For example, at the time of nodding action or other neck actions that do not cause a change in the relative position between the thyroid cartilage and the skin on the thyroid cartilage (action of vertically moving the head), the relative position between the thyroid cartilage and the skin does not change. At the time of swallowing action, the relative position between the thyroid cartilage and the skin changes. Therefore, the signals from the sensing portions differ between the vertical movement of the neck and the swallowing action. Thus, erroneous detection along with the vertical movement of the neck can be suppressed.

In the present disclosure, the swallowing detector makes determination for the swallowing by making determination for the upward movement and the forward movement of the laryngeal prominence based on the signals from the plurality of sensing portions.

In the upward movement of the laryngeal prominence, peaks occur in the signals from the plurality of sensing portions because the laryngeal prominence moves upward. In the forward movement of the laryngeal prominence, peaks occur in the signals from the plurality of sensing portions because the laryngeal prominence moves forward. The swallowing detector can make determination for the swallowing by determining whether the peaks occur.

In the present disclosure, the piezoelectric element is formed by using the piezoelectric film.

According to the present disclosure, the piezoelectric element is formed by using the piezoelectric film. Therefore, the weight of the piezoelectric element per attachment area can be reduced. Thus, the sensing portions can be formed thin and light, and the movement of the larynx including the thyroid cartilage is not hindered. Further, discomfort of the patient can be reduced, and the peeling of the piezoelectric element off the skin of the neck region can be suppressed because the piezoelectric element is light.

In the present disclosure, the swallowing analyzer makes determination for the swallowing function based on the data on the displacement signal and the sound signal during the swallowing.

Therefore, it is also possible to detect, for example, abnormal noise frequently observed in a swallowing function abnormality. Thus, the determination accuracy of the swallowing function (dysphagia) is improved.

In the embodiments described above, description is made using the piezoelectric film sensor3as the sensor portion2. The sensor portion may be a strain sensor. The strain sensor (strain detecting element) is described below.

As illustrated inFIGS.14to17, a strain sensor100aof a first embodiment is a strain sensor including a sensor unit4aand a fixing member6a.

The sensor unit4aincludes a sensor sheet41a, a body42a, and a connecting portion43a. The sensor sheet41aincludes a detecting portion45aconfigured to detect strain in a predetermined direction, and fixing portions46aand47alocated at both ends of the detecting portion45a. The sensor sheet41ais coupled, via the connecting portion43a, to the body42aconfigured to process signals outputted from the detecting portion45a.

The fixing member6ahas a first principal surface and a second principal surface that face each other. A tensile load of the fixing member6ais larger than a tensile load of the detecting portion45aof the sensor sheet41a.

The sensor unit4ais fixed to the first principal surface of the fixing member6aby attaching the sensor sheet41aand the body42ato the fixing member6a. The sensor sheet41ais fixed in a state in which the entire sensor sheet41aoverlaps the first principal surface of the fixing member6a. That is, the fixing member6aexists so as to overlap the entire sensor sheet41ain a plan view. The plan view means that the strain sensor is viewed orthogonally to the principal surface of the fixing member.

The strain sensor100aof the first embodiment is used by attaching the second principal surface of the fixing member6ato a measurement target object so that the detecting portion45aof the sensor sheet41ais located in a measurement region of the measurement target object.

The detailed structures of the sensor unit4a, the fixing member6a, and the strain sensor100aare described below.

(Sensor Unit)

As described above, the sensor unit4aincludes the sensor sheet41a, the body42a, and the connecting portion43a.

The sensor sheet41aincludes a base51ahaving a first principal surface and a second principal surface that face each other, and a conductor52aprovided on the first principal surface of the base51a.

The constituent material for the base51ais preferably an expansible and contractible material having a low elastic modulus. The material preferably contains an expansible and contractible material having a low elastic modulus, such as polyurethane, acrylic, or a silicone resin.

The thickness of the base51ais not particularly limited. The thickness may be preferably 10 μm or more and 200 μm or less, more preferably 20 μm or more and 100 μm or less, even more preferably 30 μm or more and 50 μm or less.

The conductor52aextends to the connecting portion43aand the body42a. That is, the conductor52aincludes a terminal conductor52a4provided on the body42a, a wiring conductor52a3provided on the connecting portion43a, a fixing conductor52a2provided on the fixing portion46a, and a detecting conductor52a1provided on the detecting portion45a. Specifically, the conductor52aextends from the body42ato the detecting portion45aof the sensor sheet via the connecting portion43aand the fixing portion46aof the sensor sheet, extends leftward from the right end of the detecting portion45a, and returns to the right end while being folded near the center of the detecting portion45a. The right side of the drawing is defined as a right side of the detecting portion45a. The conductor52athat returns to the right end extends to the body42avia the fixing portion46aof the sensor sheet and the connecting portion43a. The folded portions of the conductor52aare arranged parallel to each other. The detecting conductor52a1expands or contracts in a lateral direction in conformity with expansion or contraction of the detecting portion45ain the lateral direction. The resistance value of the detecting conductor52a1changes in response to the change in the length of the detecting conductor52a1. By detecting the change in the resistance value of the detecting conductor52a1, the expansion/contraction amount of the detecting portion45a, that is, strain of the measurement target object can be detected. That is, the detecting conductor52a1constitutes a sensing portion52a11.

The constituent material for the detecting conductor52a1of the conductor52ais preferably a material that greatly changes in the resistance value in response to expansion or contraction. It is preferable to form the detecting conductor52a1by using a mixture containing metal powder such as silver (Ag) or copper (Cu) and an elastomeric resin such as silicone. When the detecting conductor52a1is formed by using the mixture of the metal powder and the resin, the number of contacts between particles of the metal powder increases or decreases and the distance between the particles of the metal powder increases through the expansion or contraction of the detecting portion45a. Therefore, it is possible to increase the rate of increase or decrease in the resistance value with respect to displacement. When the detecting conductor52a1is formed by using the mixture of the metal powder and the resin, breakage due to deformation can be prevented by expansion and contraction properties of the resin.

The constituent material for the portions of the conductor52aother than the detecting conductor52a1, specifically, the fixing conductor52a2, the wiring conductor52a3, and the terminal conductor52a4, may be the same constituent material as that for the detecting conductor52a1or may be a constituent material different from that for the detecting conductor52a1. If the conductor52aother than the detecting conductor52a1is formed of the same material as that for the detecting conductor52a1, the detecting conductor52a1and the conductor52aother than the detecting conductor52a1can collectively be formed in one step. Therefore, the manufacture can be performed at low costs. If the conductor52aother than the detecting conductor52a1is formed of a constituent material different from that for the detecting conductor52a1, the increase or decrease in the resistance value with respect to the displacement of the detecting conductor52a1is made more significant and the breakage due to the expansion or contraction is prevented. In addition, the conductor52aother than the detecting conductor52a1can be formed of a material having a low resistance. Thus, strain can be detected with higher accuracy.

In the strain sensor100aof the first embodiment, five conductors52aare arranged. That is, the strain sensor100aincludes a plurality of sensing portions52a11to52a15. The sensing portions52a11to52a15are arranged parallel to each other in the detecting portion45aat regular intervals in a vertical direction. The vertical direction means a direction from top to bottom inFIG.14andFIG.15. By providing the plurality of detecting portions, strain can be detected in a wider range or the accuracy can further be increased if the detection is performed in a range of the same size.

In this embodiment, the sensing portions52a11to52a15are arrayed in the longitudinal direction of the neck region (vertical direction) in a state in which the strain sensor100ais attached to the anterior neck region102of the subject101. Specifically, the sensing portions52a11to52a15are arranged from the upper side to the lower side so as to cover the thyroid cartilage103. The sensing portions52a11to52a15are electrically isolated from each other and individually output signals.

The detecting portion45ais a region where a change in the shape of the measurement target object is measured. The outside dimension of the detecting portion45ais set in consideration of the range of the measurement region and the followability of the detecting portion45ais set in consideration of the flexibility of the measurement target object.

The detecting portion45aincludes a plurality of slits53aprovided in a direction intersecting the direction of expansion and contraction of the detecting portion. By providing the slits53ain the detecting portion45a, the detecting portion45ahas a shape and structure in which the detecting portion45ais deformed more easily than the periphery. Thus, the followability of the detecting portion45acan be increased.

In the strain sensor100aof the first embodiment, as illustrated inFIG.14, the detecting portion45aincludes the sensing portion52a11constituted by the detecting conductor52a1, and a low elastic modulus portion formed so as not to restrain the deformation of the detecting portion in response to strain and not to restrain the deformation of the measurement target object. The “low elastic modulus” in a case of expressing the low elastic modulus in the low elastic modulus portion or changing into the low elastic modulus herein means that the elastic modulus is lower than those of the fixing portions46aand47a.

The fixing portions46aand47asupport the detecting portion45aso that, when the measurement region of the measurement target object expands or contracts, the detecting portion45aexpands or contracts in response to the expansion or contraction. In the strain sensor100aof the first embodiment, the fixing portions46aand47aare provided on both sides of the detecting portion45ain the direction of expansion and contraction of the detecting conductor52a1(that is, the detecting portion). The fixing portions46aand47ainclude confinement portions54aand55aso that, when the measurement region of the measurement target object expands or contracts, the strain corresponding to the expansion or contraction of the measurement region can be detected without being influenced by expansion or contraction of regions other than the measurement region. As illustrated inFIG.15, the confinement portions54aand55aare provided in the fixing portions46aand47a, respectively. It is preferable that the confinement portions54aand55abe provided close to the detecting portion45a. Thus, the strain in the measurement region of the measurement target object can accurately be measured while reducing the influence of portions other than the measurement region.

The body42aincludes a base57aand the terminal conductor52a4. The terminal conductor52a4is provided on one principal surface of the base57a.

The constituent material for the base57ais not particularly limited and may be the same material as the constituent material for the base51a, such as polyurethane, acrylic, or a silicone resin.

The connecting portion43aincludes a base58aand the wiring conductor52a3. The wiring conductor52a3is provided on one principal surface of the base58a. The connecting portion43ais provided to couple the sensor sheet41ato the body42aand to electrically connect the detecting conductor52a1of the sensor sheet41ato the terminal conductor52a4of the body42a.

(Fixing Member)

The fixing member6ais a sheet-shaped member having the first principal surface and the second principal surface that face each other.

The tensile load of the fixing member6ais larger than the tensile load of the sensor sheet41a. That is, the fixing member6ais less stretchable than the sensor sheet41a. With this structure, the degrees of buffering of movement by an interposed object having flexibility are equalized. Thus, variations in strain measurement results can be reduced. For example, if an articulation or cartilage is measured, movement is detected by the sensor with superficial skin interposed therebetween. Even if the movement of the articulation or cartilage is the same, the followability of the sensor differs due to individual differences in the flexibility of the skin, the shape of crease, or the like. Thus, different measurement results may be obtained. With the strain sensor disclosed herein, the variations in the measurement results can be reduced even if individual differences are present.

Examples of the constituent material for the fixing member6ainclude a rubber and a sponge.

Examples of the rubber include a urethane rubber and a silicon rubber.

Examples of the sponge include a nitrile rubber sponge (NBR sponge), a chloroprene rubber sponge (CR sponge), and an ethylene rubber sponge (EPDM rubber sponge). The sponge is preferably the chloroprene rubber sponge.

The sponge may be a closed-cell or open-cell sponge.

FIG.17illustrates an example of waveform patterns during swallowing, which are obtained by the strain sensor. The solid lines represent signals obtained by the sensing portions52a11to52a15. The broken line represents a video analysis result of swallowing videofluorography (VF). A peak of an increase in a sensor output value occurs when the sensor is strained in a stretching direction. Therefore, the peak indicates that the thyroid cartilage moves forward or backward at the corresponding sensing portion. The forward movement of the thyroid cartilage can be estimated based on the increase or decrease in the sensor output value. If the peaks of the sensing portions appear with time differences, it can be estimated that the thyroid cartilage moves upward or downward so as to pass the sensing portions in order of the time differences.

Specifically, as illustrated inFIG.17, peaks Pa1, Pb1, and Pc1occur in the sensing portions52a14to52a12around 2.5 seconds. Then, a peak Pd1occurs in the sensing portion52a11around 3.5 seconds and peaks Pc2, Pb2, and Pa2occur sequentially in the sensing portions52a12,52a13, and52a14around 4 seconds. To check this movement against the video analysis result of the swallowing videofluorography (VF), the movement matches with a state in which the thyroid cartilage moves upward from around 2.5 seconds to around 3.5 seconds and moves downward from around 3.5 seconds to around 4 seconds. At this timing of vertical movement, a bolus of food passes by the thyroid cartilage. Thus, it can be confirmed that the swallowing occurs. That is, swallowing behavior is started at the peak Pa1, the thyroid cartilage ascends at Pb1, Pc1, and Pd1, and the thyroid cartilage descends at the peaks Pd1, Pc2, Pb2, and Pa2to return to the initial position. Thus, it is understood that the swallowing is completed. The swallowing determination can be made based on the time differences among the peaks in the sensing portions.1swallowing sensor2sensor portion3piezoelectric film sensor (piezoelectric element)3A,3B sensing portion4piezoelectric film5,6first and second electrode films10attachment member20body (swallowing detector)21,22pre-processing unit21B,22B LPF21C,22C HPF23signal processing unit24memory25wireless communication module26battery30swallowing analyzerS swallowing analyzing system