WO2013140583A1 - Fluid evaluation device and method - Google Patents

Description

Fluid evaluation apparatus and method

The present invention relates to a technical field of a fluid evaluation apparatus and method for evaluating a fluid by detecting a flow rate of the fluid such as a blood flow.

As this type of fluid evaluation device, for example, there is a device that detects a blood flow using a laser blood flow meter (see, for example, Patent Document 1). The laser blood flow meter disclosed in Patent Document 1 irradiates a living body with laser light and detects the blood flow rate of the living body based on a change in wavelength caused by Doppler shift that occurs during reflection or scattering. More specifically, when the living body is irradiated with laser light, scattered light is generated due to the flow of blood in the blood vessels of the living body (that is, movement of red blood cells that are scatterers). The frequency of the scattered light is changed by the laser Doppler action corresponding to the moving speed of the red blood cells that are the scatterers, as compared with the frequency of the original laser light. A signal component corresponding to a so-called frequency difference signal is obtained by mutual interference between the scattered light and the reflected light of the laser light from the living body. By analyzing this signal component, the blood flow of the living body is detected.

In addition, although it is not the literature which discloses the apparatus which detects a blood flow rate, there exists patent document 2 and 3 as another prior art literature relevant to this invention.

Japanese Patent No. 4658705 Japanese Patent No. 3350521 JP 2001-224593 A

The blood flow generally varies greatly according to the heart beat (for example, changes in a sine curve). For this reason, when the detected blood flow is output as it is (for example, output to a display connected to the outside of the laser Doppler blood flow meter), the blood flow that changes every moment along the time axis is output. It will be. In some cases, the blood flow volume (that is, the detection result) output in this way may be difficult to utilize. Therefore, it is conceivable to try to make it easier to utilize the output blood flow volume (that is, the detection result) by calculating the time average value of the detected blood flow volume and outputting the calculated time average value.

Here, depending on the method of calculating the time average value of blood flow, the calculated time average value of blood flow may deviate from the time average value of blood flow that should be calculated (that is, ideal). This is clarified by experiments by the inventors of the present application. For example, suppose that the time average value of the blood flow volume for every predetermined fixed period is calculated. On the other hand, the pulsation cycle of blood flow can always vary according to the pulsation of the heart. For this reason, when the time average value of the blood flow rate for each predetermined fixed period is calculated, the calculated blood is caused by the difference between the pulsation cycle of the blood flow and the fixed cycle for calculating the time average value of the blood flow rate. It is clear from experiments by the present inventors that the time average value of the flow rate may become larger or smaller than the time average value of blood flow that should be originally calculated (that is, ideal). It has become. Such a change (that is, error) in the time average value of the blood flow rate is not preferable from the viewpoint of highly accurate detection of the blood flow rate.

The above-described technical problem is not limited to the case where the time average value of the blood flow rate (blood flow rate) is calculated, but may similarly occur when the time average value of the flow rate of any fluid is calculated. .

The present invention has been made in view of the above-mentioned problems, for example, and an object of the present invention is to provide a fluid evaluation apparatus and method capable of suitably calculating an average value of fluid flow rates.

A fluid evaluation apparatus for solving the above-described problem is to detect an irradiation unit that irradiates a laser beam to a measurement target in which a fluid flows, and the laser beam irradiated to the measurement target. First detection means for detecting the flow rate of the fluid based on a change in frequency resulting from a Doppler shift of the laser light, and a second detection for detecting a pulsation cycle of the flow rate based on the change in the flow rate. And means for calculating an average value of the flow rate for each period synchronized with the pulsation cycle.

A fluid evaluation method for solving the above-described problem includes an irradiation step of irradiating a measurement target with a fluid flowing therein to a laser beam, and detecting the laser beam irradiated to the measurement target. A first detection step for detecting the flow rate of the fluid based on a frequency change resulting from a Doppler shift of the laser light, and a second detection for detecting a pulsation cycle of the fluid based on the change in the flow rate. And a calculation step of calculating an average value of the flow rate for each period synchronized with the pulsation cycle.

It is a block diagram which shows the structure of the blood flow rate detection apparatus of 1st Example. It is a flowchart which shows the flow of operation | movement of the blood flow rate detection apparatus of 1st Example. It is a timing chart which shows the waveform of the various signals observed in the case of operation | movement of the blood flow rate detection apparatus of 1st Example. Without calculating the number of samples corresponding to the pulse wave period, various signals observed during the operation of the blood flow detection device of the comparative example that calculates the average value (average blood flow) of the blood flow of a fixed number of samples It is a timing chart which shows a waveform. It is a block diagram which shows the structure of the blood flow rate detection apparatus of 2nd Example. It is a flowchart which shows the flow of operation | movement of the blood flow rate detection apparatus of 2nd Example. It is a block diagram which shows the structure of the blood flow rate detection apparatus of 3rd Example. It is a flowchart which shows the flow of operation | movement of the blood flow rate detection apparatus of 3rd Example. It is a block diagram which shows the structure of the blood flow rate detection apparatus of 4th Example. It is a flowchart which shows the flow of operation | movement of the blood flow rate detection apparatus of 4th Example. It is a timing chart which shows the waveform of various signals observed in the case of operation of the blood flow rate detection device of the 4th example.

Hereinafter, embodiments of a fluid evaluation apparatus and method will be described in order as modes for carrying out the invention.

(Embodiment of fluid evaluation apparatus)
<1>
The fluid evaluation apparatus according to the present embodiment is obtained by detecting an irradiation unit that irradiates laser light to a measurement target in which a fluid flows, and the laser light irradiated to the measurement target. First detection means for detecting the flow rate of the fluid based on a frequency change resulting from the Doppler shift of the laser light; and second detection means for detecting a pulsation cycle of the flow rate based on the change in the flow rate; Calculating means for calculating an average value of the flow rate for each period synchronized with the pulsation cycle.

According to the fluid evaluation apparatus of this embodiment, the irradiation means irradiates the measurement target with laser light. A fluid flows inside the object to be measured. The laser light is preferably applied to the fluid. Examples of the measurement target and the fluid include living bodies such as humans and animals and blood. Or a water pipe and water are mention | raise | lifted as another example of a to-be-measured object and a fluid.

The first detection means detects the flow rate of the fluid based on the frequency change caused by the Doppler shift of the laser light. Specifically, for example, when laser light is irradiated on the measurement target, scattered light is generated due to the flow of fluid inside the measurement target. The frequency of the scattered light is changed by the laser Doppler action corresponding to the moving speed of the fluid as compared with the frequency of the original laser light. A signal component corresponding to a so-called frequency difference signal is obtained by the mutual interference between the scattered light and the reflected light of the laser light from the object to be measured. By analyzing this signal component, the flow rate of the fluid is detected.

The second detection means detects the pulsation cycle of the flow rate based on the change in the flow rate detected by the first detection means. Note that the “pulsation cycle” means, for example, a flow rate change cycle that changes so as to pulsate (for example, a period from the peak value of the flow rate to the next peak value). When the fluid is blood, the pulsation cycle substantially coincides with the pulse cycle (typically, the cycle of one pulse).

The calculating means calculates an average value of the flow rate detected by the first detecting means (for example, a time average value that is an average value of the sum of the sample values of the flow rate every predetermined time). Particularly in the present embodiment, the calculation means calculates an average value of the flow rate for each period synchronized with the pulsation cycle (for example, a time average value that is an average value of the sum of the sample values of the flow rate for each period synchronized with the pulsation cycle). To do. In other words, the calculation means calculates the average value of the flow rate for each period synchronized with the pulsation cycle (for example, for each period synchronized with the pulsation cycle, the sum of the sample values of the flow rate detected during the period) Calculate the average time value). In other words, the calculation means calculates an average value of the flow rate in synchronization with the pulsation cycle (for example, calculates a time average value that is an average value of the sum of the sample values of the flow rate in synchronization with the pulsation cycle). .

I will give a specific example. For example, it is assumed that the pulsation cycle detected by the second detection means is 1 second. The first detection means detects the flow rate once every 0.1 seconds. In this case, the calculation means calculates an average value of the flow rate per second, which is a pulsation cycle. In other words, considering that the first detection means detects the flow rate 10 times during one second, which is the pulsation cycle, the calculation means can obtain 10 flow rate samples detected during the 1 second, which is the pulsation cycle. The average value of the sum of values is calculated. On the other hand, if the pulsation cycle detected by the second detection unit is changed to 1.2 seconds, the calculation unit calculates the sum of the sample values of 12 flow rates detected during the pulsation cycle of 1.2 seconds. The average value of is calculated.

According to the fluid evaluation apparatus of the present embodiment described above, the average value of the fluid flow rate is calculated in accordance with the pulsation cycle of the fluid flow rate that may change due to some factor. That is, the calculation cycle for calculating the average value of the fluid flow rate is appropriately adjusted according to the pulsation cycle of the fluid flow rate. Therefore, according to the fluid evaluation device of the present embodiment, the pulsation cycle of the fluid flow rate and the fluid are compared with the fluid evaluation device of the comparative example in which the calculation cycle when calculating the average value of the fluid flow rate is fixed. The possibility of a deviation from the calculation cycle for calculating the average value of the flow rates of is reduced. Alternatively, according to the fluid evaluation apparatus of the present embodiment, there is little or no deviation between the pulsation cycle of the fluid flow rate and the calculation cycle for calculating the average value of the fluid flow rate. Therefore, according to the fluid evaluation apparatus of the present embodiment, the flow rate of the fluid calculated by the calculation unit as compared with the fluid evaluation apparatus of the comparative example in which the calculation cycle when calculating the average value of the flow rate of the fluid is fixed. Is less likely to deviate from the average value of the flow rate of the fluid to be originally calculated (that is, ideal). Alternatively, according to the fluid evaluation apparatus of the present embodiment, the average value of the flow rate of the fluid calculated by the calculation unit may deviate from the average value of the flow rate of the fluid that should be originally calculated (that is, ideal). Little or no. For this reason, the fluid evaluation apparatus of this embodiment can calculate the average value of the flow volume of a fluid suitably.

<2>
In another aspect of the fluid evaluation apparatus according to the present embodiment, the calculation unit is configured to perform the calculation every the same period as the pulsation period or every N times (where N is an integer of 2 or more) the pulsation period. Calculate the average flow rate.

According to this aspect, the calculation means preferably uses an average value of the flow rate for each period synchronized with the pulsation cycle (for example, a time average value that is an average value of the sum of the sample values of the flow rate for each period synchronized with the pulsation cycle). Can be calculated.

<3>
In another aspect of the fluid evaluation apparatus of the present embodiment, the fluid evaluation apparatus further includes an output unit that outputs the average value calculated by the calculation unit at a desired timing.

According to this aspect, the average value of the flow rate of the fluid calculated by the calculation unit is output to another device (for example, a display or an analysis circuit) provided in the fluid evaluation device or attached to the outside of the fluid evaluation device. Is done.

<4>
In another aspect of the fluid evaluation apparatus including the output unit as described above, the desired timing is a fixed timing that appears periodically.

According to this aspect, the average value of the flow rate of the fluid calculated by the calculation means is output at a constant cycle. For this reason, even if the period during which the calculation unit calculates the average value (that is, the period synchronized with the pulsation cycle) fluctuates, the cycle in which the average value of the fluid flow rate calculated by the calculation unit is output from the output unit is constant. Kept. Therefore, compared with the case where the average value of the flow rate of the fluid calculated by the calculation unit is output in a random cycle, the average value can be easily used for other apparatuses that acquire the average value from the output unit.

<5>
In another aspect of the fluid evaluation apparatus including the output unit as described above, the desired timing is a timing designated by the user.

According to this aspect, the average value of the flow rate of the fluid calculated by the calculation means is output at a timing designated by the user. For this reason, even if the period during which the calculation unit calculates the average value (that is, the period synchronized with the pulsation cycle) fluctuates, the cycle in which the average value of the fluid flow rate calculated by the calculation unit is output from the output unit is It is adjusted appropriately according to the instructions. Therefore, compared with the case where the average value of the flow rate of the fluid calculated by the calculation means is output in a cycle unrelated to the user's instruction, for other devices that acquire the average value from the output means, the average value is It becomes easy to use.

<6>
In another aspect of the fluid evaluation apparatus of this embodiment, the fluid evaluation device further includes third detection means for detecting the amplitude of the flow rate, and the calculation means (i) when the amplitude is equal to or greater than a predetermined amount, An average value of the flow rate for each period synchronized with the pulsation cycle detected by the detection unit is calculated, and (ii) the pulsation detected by the first detection unit in the past when the amplitude does not exceed the predetermined amount. The average value of the flow rate for each period synchronized with the cycle is calculated.

According to this aspect, when the amplitude of the flow rate is relatively small (that is, not larger than the predetermined amount), compared to the case where the amplitude of the flow rate is relatively large (that is, larger than the predetermined amount), It is presumed that the reliability of the pulsation cycle detected by the second detection means is relatively lowered. Therefore, when the amplitude of the flow rate is relatively small (that is, not more than a predetermined amount), the calculating means replaces the pulsation cycle with relatively low reliability that the second detecting means detects in real time. The second detection means having relatively high reliability calculates the average value of the flow rate for each period synchronized with the pulsation cycle detected in the past. For this reason, the reliability of the average value calculated by the calculation means is relatively compared with the case where the average value of the flow rate for each period synchronized with the pulsation cycle detected in real time by the second detection means is always calculated. Can be increased.

The calculation means is a period synchronized with the pulsation period itself of the flow rate detected by the second detection means in the past (that is, the same period as the pulsation period or N times the pulsation period (where N is an integer of 2 or more). Alternatively, the average value of the flow rate for each 1 / N times) may be calculated. Alternatively, the calculation unit may calculate an average value of the flow rate for each period synchronized with the time average value of the pulsation cycle of the flow rate detected in the past by the second detection unit.

<7>
The fluid is a blood flow flowing inside the living body as the measurement target, and the pulsation cycle is a pulse wave cycle of the blood flow.

According to this aspect, in the fluid evaluation device, the calculation means has a blood flow rate for each period synchronized with the pulse wave cycle of blood (that is, the pulse cycle, typically one pulse cycle). An average value of (that is, blood flow volume) can be calculated.

(Embodiment of fluid evaluation method)
<8>
The fluid evaluation method of the present embodiment is obtained by irradiating a laser beam to a measurement target in which a fluid flows inside, and detecting the laser beam irradiated to the measurement target. A first detection step for detecting a flow rate of the fluid based on a frequency change caused by a Doppler shift of the laser light; a second detection step for detecting a pulsation cycle of the fluid based on the change in the flow rate; A calculation step of calculating an average value of the flow rate for each period synchronized with the pulsation cycle.

According to the fluid evaluation method of the present embodiment, various effects enjoyed by the fluid evaluation apparatus of the present embodiment described above can be suitably enjoyed.

Incidentally, in response to various aspects adopted by the fluid evaluation apparatus of the present embodiment, the fluid evaluation method of the present embodiment may adopt various aspects.

Such an operation and other advantages of the present embodiment will be clarified from examples described below.

As described above, the fluid evaluation apparatus according to the present embodiment includes an irradiation unit, a first detection unit, a second detection unit, and a calculation unit. The fluid evaluation method of this embodiment includes an irradiation process, a first detection process, a second detection process, and a calculation process. Therefore, the average value of the flow rate of the fluid can be suitably calculated.

Hereinafter, embodiments of the fluid evaluation apparatus will be described with reference to the drawings. Hereinafter, an example in which the fluid evaluation device is applied to a blood flow rate detection device that detects a flow rate (that is, blood flow rate) of blood flowing in a blood vessel of a living body will be described. However, the fluid evaluation device can detect any flow rate of any fluid other than blood (for example, water flowing in a water pipe or blood flowing in a tube constituting a blood flow circuit of an artificial dialysis device). The present invention may be applied to a flow rate detection device.

(1) First Embodiment First , the blood flow detection device 1 of the first embodiment will be described with reference to FIGS.

(1-1) Configuration of Blood Flow Detection Device First, the configuration of the blood flow detection device 1 of the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of a blood flow rate detection device 1 according to the first embodiment.

As shown in FIG. 1, the blood flow rate detection device 1 according to the first embodiment includes a laser element 11, a light receiving element 12, an amplifier 13, an analog / digital (A / D) converter 14, an arithmetic circuit 15, A pulse wave period detection circuit 16, an averaging circuit 17, a timing generator 18, and a sampling circuit 19 are provided.

The laser element 11 constitutes a specific example of “irradiation means” and irradiates the living body 100 such as a human being or an animal with the laser beam LB. At this time, it is preferable that the laser element 11 irradiates the blood vessel in the living body 100 with the laser beam LB.

The light receiving element 12 constitutes a specific example of “first detection means”, and beat signals generated by mutual interference between the reflected light of the laser light LB from the living body 100 and the scattered light of the laser light LB from the living body 100. Receives light. The light receiving element 12 generates a detection current obtained by converting the received beat signal light into an electrical signal.

The amplifier 13 constitutes a specific example of “first detection means”, which amplifies the detection current output from the light receiving element 12 after converting it into a voltage signal.

The A / D converter 14 constitutes a specific example of “first detection means”, and an A / D converter 14 outputs A / D with respect to the output of the amplifier 13 (that is, the voltage signal corresponding to the beat signal light received by the light receiving element 12). D conversion processing (that is, quantization processing) is performed. As a result, the A / D converter 14 outputs the sample value of the voltage signal (that is, the quantized voltage signal) corresponding to the beat signal light received by the light receiving element 12 to the arithmetic circuit 15.

The arithmetic circuit 15 constitutes a specific example of “first detection means”, and outputs the output of the A / D converter 14 (that is, the sample value of the voltage signal corresponding to the beat signal light received by the light receiving element 12). On the other hand, frequency analysis using FFT (Fast Fourier Transform) is performed. As a result, the arithmetic circuit 15 calculates a blood flow rate Q (k (where k is a variable assigned in time series in accordance with the blood flow calculation timing)).

The pulse wave cycle detection circuit 16 constitutes a specific example of “second detection means”, and by analyzing the temporal change of the blood flow rate Q (k) calculated by the calculation circuit 15, the pulse wave cycle (that is, , The period of blood pulsation, and substantially the period of pulse) Tr. Thereafter, the pulse wave cycle detection circuit 16 counts the number of samples n of the blood flow rate Q (k) corresponding to the pulse wave cycle Tr (that is, the number of samples of the blood flow rate Q (k) detected in the same period as the pulse wave cycle. n) is calculated.

The averaging circuit 17 constitutes a specific example of “calculation means”, and calculates an average value of n blood flow volumes Q (k) (hereinafter referred to as “average blood flow volume Qh” as appropriate).

The timing generator 18 generates a timing at which the sampling circuit 19 outputs the average blood flow rate Qh.

The sampling circuit 19 constitutes a specific example of “output means”, and the blood flow detection device 1 synchronizes the average blood flow Qh calculated by the averaging circuit 17 with the timing generated by the timing generator 18. (Or to a processing block (not shown) included in the blood flow rate detection device 1).

Note that the blood flow detection device 1 may output the average blood flow Qh calculated by the averaging circuit 17 as it is. In this case, the blood flow rate detection device 1 may not include the timing generator 18 and the sampling circuit 19.

(1-2) Operation of Blood Flow Detection Device Next, the flow of operation of the blood flow detection device 1 of the first embodiment will be described with reference to FIGS. FIG. 2 is a flowchart showing the operation flow of the blood flow rate detection device 1 of the first embodiment. FIG. 3 is a timing chart showing waveforms of various signals observed during the operation of the blood flow rate detection device 1 of the first embodiment.

As shown in FIG. 2, the laser element 11 irradiates a living body 100 such as a human being or an animal with the laser beam LB (step S11). At this time, it is preferable that the laser element 11 irradiates the blood vessel in the living body 100 with the laser beam LB.

Thereafter, the light receiving element 12 receives the beat signal light generated by the mutual interference between the reflected light of the laser light LB from the living body 100 and the scattered light of the laser light LB from the living body 100 (step S12). Specifically, when the living body 100 is irradiated with the laser light LB, scattered light is generated due to blood flow inside the blood vessel in the living body 100 (that is, movement of red blood cells that are scatterers). The frequency of the scattered light is changed by the laser Doppler action corresponding to the moving speed of the blood as compared with the frequency of the original laser light. The light receiving element 12 receives beat signal light (so-called frequency difference signal) generated by mutual interference between the scattered light and the reflected light of the laser light LB from the living body 100. Note that as the scattered light that generates the beat signal light, forward scattered light corresponding to the transmitted light of the laser light LB irradiated on the living body 100 may be used, or the reflected light of the laser light LB irradiated on the living body 100. Backscattered light corresponding to may be used.

Thereafter, the light receiving element 12 generates a detection current obtained by converting the received beat signal light into an electric signal. The light receiving element 12 outputs the generated detection current to the amplifier 13. The amplifier 13 converts the detection current output from the light receiving element 12 (that is, the detection current corresponding to the beat signal light received by the light receiving element 12) into a voltage signal and then amplifies it. The amplifier outputs a voltage signal to the A / D converter 14.

Thereafter, the A / D converter 14 performs an A / D conversion process (that is, a quantization process) on the output of the amplifier 13 (that is, a voltage signal corresponding to the beat signal light received by the light receiving element 12) (steps). S13). As a result, the A / D converter 14 outputs the sample value of the voltage signal (that is, the quantized voltage signal) corresponding to the beat signal light received by the light receiving element 12 to the arithmetic circuit 15. Specifically, for example, if the sampling period of the A / D converter 14 is Ta, the A / D converter 14 samples the voltage signal sample value (corresponding to the beat signal light received by the light receiving element 12 for each period Ta ( That is, a quantized voltage signal) is output.

The arithmetic circuit 15 performs frequency analysis using FFT (Fast Fourier Transform) on the output of the A / D converter 14 (that is, the sample value of the voltage signal corresponding to the beat signal light received by the light receiving element 12). . As a result, the arithmetic circuit 15 calculates a blood flow rate Q (k) (step S14: refer to the first waveform in FIG. 3). Specifically, for example, the arithmetic circuit 15 performs FFT on the sample value of the voltage signal corresponding to the beat signal light and the Nf sample values. The arithmetic circuit 15 calculates the blood flow rate Q (k) using a first moment that is a result of multiplication of the power spectrum and the frequency vector obtained by performing the FFT. Since a known method (for example, the method disclosed in Japanese Patent No. 3313841) may be used as a method for calculating the blood flow rate Q (k) by frequency analysis using FFT, detailed description thereof is omitted. To do. The arithmetic circuit 15 outputs the calculated blood flow volume Q (k) to each of the pulse wave period detection circuit 16 and the averaging circuit 17.

Note that the period in which the blood flow volume Q (k) is calculated (that is, the period in which one (in other words, one sample) blood flow volume Q (k) is calculated) Tq is the first and second stages in FIG. As shown in each waveform of the stage, Nf × Ta (that is, the number of FFT points Nf × the sampling period Ta of the A / D converter 14).

Thereafter, the pulse wave cycle detection circuit 16 analyzes the time change of the blood flow rate Q (k) calculated by the arithmetic circuit 15 (that is, the time change of the blood flow rate Q (k) of a plurality of samples) to thereby calculate the pulse wave cycle. Tr is calculated (step S15). For example, the pulse wave period detection circuit 16 binarizes the blood flow rate Q (k) with reference to the amplitude center of the blood flow rate Q (k) as shown in the first and third waveforms in FIG. And the pulse wave period Tr is calculated for a period from the rise to the fall of the binarized blood flow rate Q (k) (that is, a combination of a pulse with an amplitude greater than or equal to a pulse less than the amplitude center). May be. In other words, for example, the pulse wave period detection circuit 16 determines that the blood flow rate Q (k) is the amplitude center of the blood flow rate Q (k), as shown in the first and third waveforms in FIG. The pulse wave period Tr may be calculated by detecting a crossing point (so-called zero cross point). Alternatively, for example, the pulse wave period detection circuit 16 detects the peak value of the blood flow rate Q (k) and calculates the interval between two peak values that are continuous on the time axis as the pulse wave period Tr. Also good. Alternatively, for example, the pulse wave cycle detection circuit 16 detects the bottom value of the blood flow rate Q (k) and calculates the interval between two bottom values that are continuous on the time axis as the pulse wave cycle Tr. Also good.

Thereafter, the pulse wave period detection circuit 16 calculates the sample number n of the blood flow rate Q (k) corresponding to the pulse wave period Tr as shown in the third waveform in FIG. 3 (step S16). Specifically, the pulse wave cycle detection circuit 16 calculates the number of samples n of the blood flow rate Q (k) detected in the same period as the pulse wave cycle Tr. In other words, the pulse wave period detection circuit 16 calculates the number of samples n of the blood flow rate Q (k) included in the same period as the pulse wave period Tr. Here, the pulse wave period detection circuit 16 may calculate the number of samples n using a mathematical formula of n = Tr / Tq = Tr / (Nf × Ta). In other words, the pulse wave period detection circuit 16 is configured such that the number of samples n = pulse wave period Tr / period of blood flow Q (k) is calculated Tq = pulse wave period Tr / (number of FFT points Nf × A / D converter 14 The number of samples n may be calculated using a mathematical formula of sampling period Ta).

A specific numerical value will be described as an example. It is assumed that the sampling period Ta of the A / D converter 14 is 55 microseconds, the FFT point number Nf is 1024, and the pulse wave period Tr is 0.9 seconds. In this case, the number of samples n is n = 0.9 / (55 × 10 ⁻⁶ × 1024) ≈16. Therefore, the number of samples n corresponding to the pulse wave period Tr = 0.9 seconds is 16. Alternatively, if the pulse wave period Tr is changed to 1.03 seconds, the number of samples n is n = 1.03 / (55 × 10 ⁻⁶ × 1024) ≈18.

Note that the number of samples n calculated by the pulse wave period detection circuit 16 is preferably an integer. Therefore, the pulse wave period detection circuit 16 may carry up the digits after the decimal point when the calculated sample number n has digits after the decimal point. Alternatively, digits after the decimal point may be carried down. Alternatively, digits after the decimal point may be rounded off.

As can be seen from the waveform at the third stage in FIG. 3, the number of samples n calculated by the pulse wave period detection circuit 16 changes as appropriate according to the time variation of the blood flow rate Q (n). That is, the number of samples n calculated by the pulse wave cycle detection circuit 16 changes appropriately according to the pulse wave cycle Tr. The third waveform in FIG. 3 shows an example in which the number of samples n1 is calculated in a certain period while the number of samples n2 is calculated in the subsequent period.

Note that the pulse wave period detection circuit 16 may calculate the number n of samples of the blood flow rate Q (k) corresponding to a period N (where N is an integer of 2 or more) times the pulse wave period Tr. In this case, the pulse wave period detection circuit 16 may calculate the number of samples n using a mathematical formula of n = Tr × N / Tq = Tr × N / (Nf × Ta).

The pulse wave period detection circuit 16 outputs the calculated sample number n to the averaging circuit 17.

Thereafter, the averaging circuit 17 calculates an average value (that is, average blood flow Qh) of the blood flow volumes Q (k) of n samples calculated in step S16 (step S17). For example, the averaging circuit 17 calculates (Q (0) + Q (1) +... + (Q (n−1)) / n as the average blood flow rate Qh, for example, the number of samples n = 16 In this case, the averaging circuit 17 adds the sample values of the 16 blood flow rates Q (k) sequentially and sequentially calculated along the time axis, and outputs the addition result with the number of samples n = 16. By dividing, the average blood flow rate Qh is calculated.

More specifically, taking the waveform shown in FIG. 3 as an example, the averaging circuit 17 determines (Q (0) + Q (1) +... In a certain period (a period in which the number of samples n1 is calculated). Then, + (Q (n1-1)) / n1 is calculated as the average blood flow rate Qh, and then the averaging circuit 17 calculates (Q (n11) in another period (period in which the number of samples n2 is calculated). ) + Q (n1 + 1) +... + (Q (n1 + n2-1)) / n2 is calculated as the average blood flow Qh, and the averaging circuit 17 outputs the calculated average blood flow Qh to the sampling circuit 19. .

Thereafter, the sampling circuit 19 synchronizes the average blood flow Qh calculated by the averaging circuit 17 with the timing generated by the timing generator 18 (corresponding to the resampling timing shown in the fifth waveform in FIG. 3), The data is output to the outside of the blood flow detection device 1 (or to a processing block (not shown) included in the blood flow detection device 1) (step S18). As a result, the average blood flow Qh shown in the waveform of the sixth stage (final stage) in FIG.

It should be noted that the timing generated by the timing generator 18 is preferably a fixed timing (that is, a timing that appears in a fixed cycle). In this case, the output rate (in other words, transfer rate) of the average blood flow Qh output from the blood flow detection device 1 is constant.

Further, the sampling circuit 19 may output a time average value Qh ′ calculated by further averaging the average blood flow rate Qh every predetermined time. In this case, fluctuations in the value output from the blood flow rate detection device 1 (in this case, the time average value Qh ′) can be reduced.

Here, as a comparative example, with reference to FIG. 4, without calculating the sample number n corresponding to the pulse wave period Tr, the average value (average blood flow rate Qh) of the blood flow rate Q (k) of m fixed samples. ) Will be described. FIG. 4 shows a blood flow detection of a comparative example in which an average value (average blood flow Qh) of blood flow Q (k) of m fixed samples is calculated without calculating the number n of samples corresponding to the pulse wave period Tr. It is a timing chart which shows the waveform of various signals observed at the time of operation of an apparatus.

As shown in FIG. 4, the blood flow rate detection device of the comparative example calculates (Q (0) + Q (1) +... + (Q (m−1)) / m as the average blood flow rate Qh. For example, when the fixed sample number m = 21, the blood flow rate detection device of the comparative example adds 21 sample values of the blood flow rate Q (k) sequentially and sequentially calculated along the time axis. At the same time, the average blood flow Qh is calculated by dividing the addition result by the fixed sample number m = 21.

However, while the number m of samples for calculating the average blood flow rate Qh is fixed, the pulse wave cycle Tr varies. This is because the blood flow pulsates with the heartbeat, and the pulse wave period Tr naturally varies with the change of the heartbeat. Therefore, a deviation occurs between the pulse wave period Tr and the calculation period for calculating the average blood flow rate Qh (that is, the period corresponding to the fixed sample number m). Therefore, depending on the timing at which the average blood flow Qh is calculated, m blood flows Q (k) for calculating the average blood flow Qh, as shown on the relatively left side of the waveform in the first stage of FIG. Of these, the number of blood flows Q (k) distributed on the side larger than the amplitude center may be larger than the number of blood flows Q (k) distributed on the side smaller than the amplitude center. The average blood flow Qh calculated from the m blood flows Q (k) is ideally calculated as shown in the vicinity of the center of the fourth waveform in FIG. Is likely to become bigger than. Alternatively, depending on the timing of calculating the average blood flow Qh, as shown on the relatively right side of the waveform in the first stage of FIG. 4, m blood flows Q (k) for calculating the average blood flow Qh Of these, the number of blood flows Q (k) distributed on the side larger than the amplitude center may be smaller than the number of blood flows Q (k) distributed on the side smaller than the amplitude center. The average blood flow Qh calculated from such m blood flow volumes Q (k) is an ideal average blood to be originally calculated, as shown on the right side of the waveform in the fourth row in FIG. The possibility of becoming smaller than the flow rate Qh is high. Therefore, if the number of samples m when calculating the average blood flow Qh is fixed, the average blood flow Qh may include an error.

In addition, it has been confirmed by experiments of the inventors of the present application and the like that the fluctuation of the average blood flow Qh having a frequency lower than the pulse wave period Tr is a fluctuation involving the activity of the autonomic nervous system of the living body 100. . This fluctuation is an original fluctuation as a reaction of the living body 100 and is preferably detected. By the way, fluctuations (that is, fluctuations in the average blood flow Qh) are generated in the average blood flow Qh output from the blood flow detection device of the comparative example, as shown in the waveform at the fourth stage in FIG. . However, this fluctuation cycle is an erroneous fluctuation due to the above-described error in the average blood flow Qh (that is, the deviation of the blood flow Q (k) used for calculating the average blood flow Qh from the amplitude center). The reaction of the living body 100 is different from the original fluctuation. However, such an erroneous fluctuation also has a frequency (that is, a long period) lower than the pulse wave period Tr of the blood flow rate Q (k). Therefore, in the blood flow rate detection device of the comparative example, the original fluctuation as the reaction of the living body 100 and the error of the above average blood flow rate Qh (that is, the blood flow rate Q (k) used when calculating the average blood flow rate Qh). Incorrect fluctuations due to (bias with respect to the amplitude center) are mixed. For this reason, there is a possibility that the original fluctuation is not suitably detected as a reaction of the living body 100.

However, according to the blood flow volume detection device 1 of the present embodiment, the average value (average blood flow volume Qh) of the blood flow volume Q (k) of n samples calculated in accordance with the pulse wave cycle Tr is calculated. That is, the calculation cycle (that is, the cycle corresponding to the number of samples n) when calculating the average blood flow Qh is appropriately adjusted according to the pulsation cycle Tr of the blood flow Q (k). Therefore, according to the blood flow rate detection device 1 of the present embodiment, there is a possibility that a deviation occurs between the pulse wave cycle Tr and the calculation cycle for calculating the average blood flow rate Qh, as compared with the blood flow rate detection device of the comparative example. Is reduced. Alternatively, according to the blood flow detection device 1 of the present embodiment, there is little or no deviation between the pulse wave cycle Tr and the calculation cycle for calculating the average blood flow Qh. According to the blood flow detection device 1 of the present embodiment, compared to the blood flow detection device of the comparative example, the n blood flows Q (k) for calculating the average blood flow Qh is larger than the amplitude center. The possibility that the number of blood flows Q (k) distributed on the side is larger than the number of blood flows Q (k) distributed on the side smaller than the amplitude center is reduced. Alternatively, according to the blood flow volume detection device 1 of the present embodiment, the blood flow volume Q (k) distributed on the side larger than the amplitude center among the n blood flow volumes Q (k) for calculating the average blood flow volume Qh. Of the blood flow volume Q (k) distributed on the side smaller than the amplitude center is hardly or not at all. Similarly, according to the blood flow volume detection device 1 of the present embodiment, the amplitude center of the n blood flow volumes Q (k) for calculating the average blood flow volume Qh as compared with the blood flow volume detection device of the comparative example. The possibility that the number of blood flow volumes Q (k) distributed on the larger side is smaller than the number of blood flow volumes Q (k) distributed on the smaller side than the amplitude center is reduced. Alternatively, according to the blood flow volume detection device 1 of the present embodiment, the blood flow volume Q (k) distributed on the side larger than the amplitude center among the n blood flow volumes Q (k) for calculating the average blood flow volume Qh. Is less than the number of blood flows Q (k) distributed on the side smaller than the amplitude center. That is, according to the blood flow volume detection device 1 of the present embodiment, compared to the blood flow volume detection device of the comparative example, from the center of amplitude among the n blood flow volumes Q (k) for calculating the average blood flow volume Qh. There is a high possibility that the number of blood flows Q (k) distributed on the larger side and the number of blood flows Q (k) distributed on the smaller side of the amplitude center substantially coincide with each other. Therefore, according to the blood flow detection device 1 of the present embodiment, the average blood flow Qh that should be originally calculated (that is, the ideal) average blood flow Qh is compared with the blood flow detection device of the comparative example. The possibility of shifting from is reduced. Alternatively, according to the blood flow rate detection device 1 of the present embodiment, the average blood flow rate Qh is hardly or completely deviated from the originally calculated (that is, ideal) average blood flow rate Qh. For this reason, the blood flow rate detection device 1 of the present embodiment can suitably calculate the average blood flow rate Qh.

In addition, according to the blood flow detection device 1 of the present embodiment, compared to the blood flow detection device of the comparative example, it is used when calculating the error of the average blood flow Qh (that is, the average blood flow Qh). The possibility that an erroneous fluctuation due to the deviation of the blood flow volume Q (k) from the amplitude center) occurs in the average blood flow volume Qh is reduced. Alternatively, according to the blood flow detection device 1 of the present embodiment, the above-described error in the average blood flow Qh (that is, the deviation of the blood flow Q (k) used for calculating the average blood flow Qh from the amplitude center). The resulting false fluctuations will occur little or no in the mean blood flow Qh. For this reason, according to the blood flow rate detection device 1 of the present embodiment, the original fluctuation is suitably detected as the reaction of the living body 100.

In order to prevent an erroneous fluctuation due to the above-described error in the average blood flow Qh (that is, the deviation of the blood flow Q (k) with respect to the amplitude center used when calculating the average blood flow Qh). In addition, it is conceivable to relatively increase the fixed sample number m. However, if the number m of fixed samples is relatively large, the original fluctuation is also averaged and suppressed as a reaction of the living body 100. For this reason, as a result, the original fluctuation may not be suitably detected as the reaction of the living body 100. Therefore, the blood flow rate detection device 1 of the present embodiment that calculates the number of samples n according to the pulse wave period Tr is very advantageous in practice.

In addition, according to the blood flow detection device 1 of the present embodiment, the average blood flow Qh is output in synchronization with the timing generated by the timing generator 18. Therefore, the output rate (in other words, transfer rate) of the average blood flow Qh output from the blood flow detection device 1 can be made constant. Therefore, it is relatively easy to construct an interface between the blood flow rate detection device 1 and the external device.

In addition, the blood flow rate detection device 1 according to the present embodiment can output the averaged blood flow rate Qh in a cycle longer than the cycle Tq in which the blood flow rate Q (k) is calculated. For this reason, compared with the case where the blood flow rate Q (k) is output as it is, the output data amount per unit time can be reduced. Furthermore, the blood flow rate detection device 1 of the present embodiment can output an average blood flow rate Qh that is the result of averaging after the blood flow rate Q (k) is averaged. For this reason, compared with the case where the blood flow rate Q (k) is output as it is, the output data amount per unit time can be reduced.

(2) Second Example Next, the blood flow detection device 2 of the second example will be described with reference to FIGS. 5 and 6. In the following description, the same configuration and operation as those of the blood flow rate detection device 1 of the first embodiment are denoted by the same reference numerals and step numbers, and detailed description thereof is omitted.

(2-1) Configuration of Blood Flow Detection Device First, the configuration of the blood flow detection device 2 of the second embodiment will be described with reference to FIG. FIG. 5 is a block diagram showing the configuration of the blood flow rate detection device 2 of the second embodiment.

As shown in FIG. 5, the blood flow rate detection device 2 of the second embodiment does not include the timing generator 18 and the user request reception unit 21 as compared with the blood flow rate detection device 1 of the first embodiment. It differs in that it is equipped. Other components included in the blood flow detection device 2 of the second embodiment may be the same as other components included in the blood flow detection device 1 of the first embodiment.

The user request accepting unit 21 accepts an instruction from a user (that is, a user of the blood flow detection device 2) instructing the timing at which the sampling circuit 19 outputs the average blood flow Qh. The user request receiving unit 21 generates a timing at which the sampling circuit 19 outputs the average blood flow Qh in synchronization with the received user instruction.

(2-2) Operation of Blood Flow Detection Device Next, the flow of operation of the blood flow detection device 2 of the second embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing the operation flow of the blood flow rate detection device 2 of the second embodiment.

As shown in FIG. 6, the blood flow rate detection device 2 of the second embodiment performs the operations from step S11 to step S17 in the same manner as the blood flow rate detection device 1 of the first embodiment.

Thereafter, in the blood flow rate detection device 2 of the second embodiment, the sampling circuit 19 generates the average blood flow rate Qh calculated by the averaging circuit 17 at the timing when the timing generator 18 generates (that is, the timing according to the user's instruction). In synchronization with (), the blood is output to the outside of the blood flow detection device 1 (step S21).

Such a blood flow volume detection device 2 of the second embodiment can preferably enjoy the same effects as the various effects that the blood flow volume detection device 1 of the first embodiment can enjoy.

In addition, according to the blood flow rate detection device 2 of the second embodiment, the average blood flow rate Qh is output in synchronization with the timing instructed by the user. Therefore, the output rate (in other words, transfer rate) of the average blood flow Qh output from the blood flow detection device 1 can be set to a user's favorite rate. Therefore, the average blood flow Qh is output in a user-friendly manner.

(3) Third Example Next, the blood flow detection device 3 of the third example will be described with reference to FIGS. In the following description, the same configuration and operation as those of the blood flow rate detection device 1 of the first embodiment are denoted by the same reference numerals and step numbers, and detailed description thereof is omitted.

(3-1) Configuration of Blood Flow Detection Device First, the configuration of the blood flow detection device 3 of the third embodiment will be described with reference to FIG. FIG. 7 is a block diagram illustrating a configuration of the blood flow rate detection device 3 according to the third embodiment.

As shown in FIG. 7, the blood flow rate detection device 3 according to the third embodiment has a pulse rate calculation circuit 31, an averaging circuit 32, and a sampling circuit 33 as compared with the blood flow rate detection device 1 according to the first embodiment. Is different in that it is further equipped. Other components included in the blood flow detection device 3 of the third embodiment may be the same as other components included in the blood flow detection device 1 of the first embodiment.

The pulse rate calculation circuit 31 calculates the pulse rate R (i (where i is a variable assigned in time series according to the timing of calculating the pulse rate)) from the sample number n calculated by the pulse wave period detection circuit 16. Is calculated.

The averaging circuit 32 calculates an average value of the predetermined number w of pulse rates R (i) (hereinafter, referred to as “average pulse rate Rh” as appropriate).

The sampling circuit 33 synchronizes the average pulse rate Rh calculated by the averaging circuit 32 to the outside of the blood flow detection device 1 (or the blood flow detection device 1 inside) in synchronization with the timing generated by the timing generator 18. Output to a processing block (not shown).

In addition, the blood flow rate detection apparatus 1 may output the average pulse rate Rh calculated by the averaging circuit 32 as it is. In this case, the blood flow rate detection device 1 may not include the sampling circuit 33.

(3-2) Operation of Blood Flow Detection Device Next, the flow of operation of the blood flow detection device 3 of the third embodiment will be described with reference to FIG. FIG. 8 is a flowchart showing the flow of the operation of the blood flow rate detection device 3 of the third embodiment.

As shown in FIG. 8, the blood flow rate detection device 3 of the third embodiment performs the operations from step S11 to step S17 in the same manner as the blood flow rate detection device 1 of the first embodiment.

In the blood flow rate detection device 3 of the third embodiment, the pulse rate calculation circuit 31 further calculates the pulse rate R (i) from the sample number n calculated by the pulse wave cycle detection circuit 16 (step S31). Here, the pulse rate calculation circuit 31 may calculate the pulse rate R (i) using a mathematical formula R (i) = n × Tq × 60 = n × (Nf × Ta) × 60. In other words, the pulse rate calculation circuit 31 calculates the pulse rate R (i) = the number of samples n × the cycle in which the blood flow rate Q (k) is calculated Tq × 60 = the number of samples n × (the number of FFT points Nf × A / D). The pulse rate R (i) may be calculated using a mathematical formula of sampling period Ta) × 60 of the converter 14.

A specific numerical value will be described as an example. It is assumed that the sampling period Ta of the A / D converter 14 is 55 microseconds, the FFT point number Nf is 1024, and the sample number n is 16. In this case, the pulse rate R (i) is R (i) = 16 × (1024 × 55 × 10 ⁻⁶ ) × 60≈54 times / minute.

The pulse rate calculation circuit 31 outputs the calculated pulse rate R (i) to the averaging circuit 32.

Thereafter, the averaging circuit 32 calculates an average value (that is, average pulse rate Rh) of a predetermined number w of pulse rates R (i) (step S32). For example, the averaging circuit 32 calculates (R (0) + R (1) +... + (R (w−1)) / w as the average pulse rate Rh, for example, when the predetermined number w = 16. In some cases, the averaging circuit 32 adds the sample values of the six pulse rates R (i) sequentially and sequentially calculated along the time axis, and divides the addition result by the predetermined number w = 16. Then, the average pulse rate Rh is calculated, and the averaging circuit 32 outputs the calculated average pulse rate Rh to the sampling circuit 33.

After that, the sampling circuit 33 synchronizes the average pulse rate Rh calculated by the averaging circuit 32 to the outside of the blood flow detection device 1 (or the blood flow detection device 1 is synchronized with the timing generated by the timing generator 18). The data is output to a processing block (not shown) provided inside (step S33).

Such a blood flow volume detection device 3 of the third embodiment can preferably enjoy the same effects as the various effects that the blood flow volume detection device 1 of the first embodiment can enjoy. In addition, according to the blood flow rate detection device 2 of the second embodiment, not only the average blood flow rate Qh but also the average pulse rate Rh is output.

(4) Fourth Example Next, the blood flow detection device 4 of the fourth example will be described with reference to FIGS. 9 to 11. In the following description, the same configuration and operation as those of the blood flow rate detection device 1 of the first embodiment are denoted by the same reference numerals and step numbers, and detailed description thereof is omitted.

(4-1) Configuration of Blood Flow Detection Device First, the configuration of the blood flow detection device 4 of the fourth embodiment will be described with reference to FIG. FIG. 9 is a block diagram showing the configuration of the blood flow rate detection device 4 of the fourth embodiment.

As shown in FIG. 9, the blood flow volume detection device 4 of the fourth embodiment is compared with the blood flow volume detection device 1 of the first embodiment, and the pulse amplitude detection circuit 41, the level decrease detection circuit 42, and the averaging The difference is that a circuit 43 and a selection circuit 44 are further provided. Other components included in the blood flow detection device 4 of the fourth embodiment may be the same as other components included in the blood flow detection device 1 of the first embodiment.

The pulse amplitude detection circuit 41 constitutes a specific example of “third detection means”, and analyzes the time change of the blood flow volume Q (k) calculated by the arithmetic circuit 15 to thereby detect the pulse amplitude (that is, blood (Amplitude of flow rate Q (k)) A is calculated.

The level drop detection circuit 42 determines whether or not the pulse amplitude A detected by the pulse amplitude detection circuit 41 is less than a predetermined threshold value.

The averaging circuit 43 calculates a predetermined number p of sample numbers n (j (where j is a variable assigned in time series according to the calculation timing of the number of samples)) (hereinafter referred to as “average samples” as appropriate). A number Nh ″).

The selection circuit 44 selects one of the number of samples n (j) detected by the pulse wave period detection circuit 16 and the average sample value Nh calculated by the averaging circuit 43 based on the determination result in the level decrease detection circuit 42. Output to the averaging circuit 17.

(4-2) Operation of Blood Flow Rate Detection Device Next, the flow of operation of the blood flow rate detection device 4 of the fourth embodiment will be described with reference to FIGS. FIG. 10 is a flowchart showing the flow of the operation of the blood flow rate detection device 4 of the fourth embodiment. FIG. 11 is a timing chart showing waveforms of various signals observed during the operation of the blood flow rate detection device 4 of the fourth embodiment.

As shown in FIG. 10, the blood flow rate detection device 4 of the fourth embodiment performs the operations from step S11 to step S16 in the same manner as the blood flow rate detection device 1 of the first embodiment.

Thereafter, in the blood flow rate detection device 4 of the fourth embodiment, the averaging circuit 43 calculates the average value (that is, the average sample number Nh) of the predetermined number p of sample numbers n (j). For example, the averaging circuit 43 calculates (n (0) + n (1) +... + (N (p−1)) / p as the average sample number Nh, for example, when the predetermined number p = 16. In some cases, the averaging circuit 43 adds the sample values of the 16 sample numbers n (i) sequentially and sequentially calculated along the time axis, and divides the addition result by the predetermined number p = 16. The averaging circuit 43 outputs the calculated average sample number Nh to the selection circuit 44.

After that, the pulse wave amplitude detection circuit 41 analyzes the time change of the blood flow volume Q (k) calculated by the arithmetic circuit 15 to obtain the pulse amplitude (that is, the amplitude of the blood flow volume Q (k), which is shown in FIG. (Refer to the second-stage waveform) A is calculated (step S42). The pulse wave amplitude detection circuit 41 may handle the amplitude of the blood flow rate Q (k) as the pulse amplitude A as it is. Alternatively, the pulse wave amplitude detection circuit 41 may handle a value obtained by performing a predetermined calculation process on the amplitude of the blood flow volume Q (k) as the pulse amplitude A.

Thereafter, the level decrease detection circuit 42 determines whether or not the pulse amplitude A detected by the pulse wave amplitude detection circuit 41 is less than a predetermined threshold (see the second waveform in FIG. 11) (step S43). The predetermined threshold value may be set to a lower limit value of the pulse amplitude A that can suitably calculate the pulse wave period Tr. Alternatively, the predetermined threshold may be set to a lower limit value of the pulse amplitude A that can calculate a reliable pulse wave period Tr.

As a result of the determination in step S43, when it is determined that the pulse amplitude A is not less than the predetermined threshold value (step S43: No), it is determined that the pulse amplitude A is not relatively decreased. That is, it is determined that the pulse amplitude A has a magnitude that allows the reliable pulse wave period Tr to be calculated. Therefore, the sample value n (j) currently calculated by the pulse wave period detection circuit 16 is estimated to be highly reliable. Therefore, in this case, the selection circuit 44 averages the number of samples n (j) detected by the pulse wave period detection circuit 16 as shown on the left side of the waveform of the fifth stage in FIG. It outputs to the circuit 17 (step S44). After that, the averaging circuit 17 calculates an average value (that is, average blood flow Qh) of the blood flow volume Q (k) of the sample number n (j) (step S17).

On the other hand, as a result of the determination in step S43, when it is determined that the pulse amplitude A is less than the predetermined threshold (step S43: Yes), it is determined that the pulse amplitude A is relatively decreased. That is, it is determined that the pulse amplitude A does not have a magnitude that allows the reliable pulse wave cycle Tr to be calculated. Therefore, the sample value n (j) currently calculated by the pulse wave period detection circuit 16 is estimated to be low in reliability. For this reason, in this case, the selection circuit 44 outputs the average number of samples Nh calculated by the averaging circuit 43 to the averaging circuit 17 as shown on the right side of the fifth waveform in FIG. (Step S45). Thereafter, the averaging circuit 17 calculates an average value (that is, average blood flow Qh) of the blood flow Q (k) of the average number of samples Nh (step S17).

Thereafter, the sampling circuit 19 synchronizes the average blood flow Qh calculated by the averaging circuit 17 with the outside of the blood flow detection device 1 (or the blood flow detection device 1 is synchronized with the timing generated by the timing generator 18). The data is output to a processing block (not shown) provided inside (step S18).

Such a blood flow volume detection device 4 of the fourth embodiment can preferably enjoy the same effects as the various effects that the blood flow volume detection device 1 of the first embodiment can enjoy.

In addition, according to the blood flow rate detection device 4 of the fourth embodiment, it is difficult to calculate the reliable sample number n due to the relative decrease in the pulse amplitude A (or reliable pulse wave period). In the case where it is difficult to calculate Tr, an average value of the sample number n calculated in the past (that is, the average sample number Nh) can be used instead of the sample number n calculated in real time. Therefore, the blood flow rate detection device 4 of the fourth embodiment can calculate the average blood flow rate Qh that is correspondingly reliable even when the pulse amplitude A is relatively decreased.

Note that the reliability of the number of samples n is substantially equivalent to the reliability of the pulse wave period Tr. Therefore, the blood flow rate detection device 4 according to the fourth embodiment performs the pulse calculated in the past in addition to or instead of calculating the average value of the number of samples n calculated in the past (that is, the average number of samples Nh). The average value of the wave period Tr may be calculated, and the number of samples n may be calculated from the average value of the pulse wave period Tr. Alternatively, the blood flow rate detection device 4 according to the fourth embodiment uses a statistically calculated average in addition to or instead of using the average value of the number of samples n calculated in the past (that is, the average number of samples Nh). The sample number n may be calculated from a reference value of a typical pulse wave period Tr.

In addition, you may combine suitably a part of each structure demonstrated in 1st Example-4th Example. Even in this case, the blood flow rate detection device obtained by appropriately combining a part of the configurations described in the first to fourth embodiments can suitably enjoy the various effects described above.

In addition, the present invention can be appropriately changed without departing from the gist or the idea of the invention that can be read from the claims and the entire specification, and a blood flow detection device and method involving such a change are also included in the present invention. Included in technical thought.

1, 2, 3, 4 Blood flow rate detection device 11 Laser element 12 Light receiving element 13 Amplifier 14 A / D converter 15 Arithmetic circuit 16 Pulse wave period detection circuit 17 Averaging circuit 18 Timing generator 19 Sampling circuit 21 User request receiving unit 31 Pulse rate calculation circuit 32 Averaging circuit 33 Sampling circuit 41 Pulse wave amplitude detection circuit 42 Level drop detection circuit 43 Averaging circuit 44 Selection circuit

Claims (8)

An irradiating means for irradiating a laser beam to a measurement target in which a fluid flows;
First detection means for detecting a flow rate of the fluid based on a frequency change caused by Doppler shift of the laser light, which is obtained by detecting the laser light irradiated on the measurement target;
Second detection means for detecting a pulsation cycle of the flow rate based on the change in the flow rate;
A fluid evaluation apparatus comprising: a calculating unit that calculates an average value of the flow rate for each period synchronized with the pulsation cycle. The said calculating means calculates the average value of the said flow volume for every period of the same period as the said pulsation period, or every period (N is an integer greater than or equal to 2) times the said pulsation period. Item 2. The fluid evaluation apparatus according to Item 1. 2. The fluid evaluation apparatus according to claim 1, further comprising output means for outputting the average value calculated by the calculation means at a desired timing. 4. The fluid evaluation apparatus according to claim 3, wherein the desired timing is a fixed timing that appears periodically. 4. The fluid evaluation apparatus according to claim 3, wherein the desired timing is a timing designated by a user. Further comprising third detecting means for detecting the amplitude of the flow rate;
The calculating means calculates (i) an average value of the flow rate for each period synchronized with the pulsation cycle detected by the first detecting means when the amplitude is a predetermined amount or more, and (ii) the amplitude 2. The fluid evaluation according to claim 1, wherein when the value does not exceed the predetermined amount, the first detection unit calculates an average value of the flow rate for each period synchronized with the pulsation cycle detected in the past. apparatus. The fluid is a blood flow flowing inside a living body as the measurement target,
The fluid evaluation apparatus according to claim 1, wherein the pulsation cycle is a pulse wave cycle of the blood flow. An irradiation step of irradiating a measurement target in which a fluid flows inside with a laser beam;
A first detection step for detecting a flow rate of the fluid based on a frequency change caused by Doppler shift of the laser light, which is obtained by detecting the laser light irradiated on the measurement target;
A second detection step of detecting a pulsation cycle of the fluid based on the change in the flow rate;
A fluid evaluation method comprising: a calculation step of calculating an average value of the flow rate for each period synchronized with the pulsation cycle.

Images