JPH04136207U - respiratory rate measuring device - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a respiration rate measuring device that can more accurately measure respiration rate based on pulse wave undulations. [Structure] The undulation of the pulse wave is determined in step S4 from the upper peak value of the pulse wave sequentially detected in step S3, and the average value of the first and second sections of the undulation is calculated in step S6. In addition, the median values of the first, second, and third sections are calculated in step S7. In step S8, the average median difference ΔAM _1, ΔAM ₂ of the first and second sections is calculated, and in step S9, the median difference ΔMI ₁₂ between the first and second sections and between the second and third sections is calculated. _, ΔMI ₂₃ are calculated respectively. First to third sections with small slopes when the absolute value of ΔMI ₁₂ is smaller than the absolute value of the average median difference ΔAM ₁ in step S10 and the absolute value of ΔMI ₂₃ is smaller than the absolute value of ΔAM ₂ in step S11 The respiration rate is determined using the pulse wave undulations of the patient.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention relates to a respiration rate measuring device that measures respiration rate based on pulse wave undulations. It is something.

0002

[Conventional technology]

In order to accurately understand the patient's condition during and after surgery, call the patient. The number of inhalations is measured and monitored. When measuring this respiration rate, Usually, methods such as electrically detecting changes in the thorax are used.

0003

[Problem that the idea aims to solve]

However, in devices that measure respiratory rate using the method described above, Usually, the part of the device that is attached to the living body is relatively large, or the part that is attached to the body is There are many places to attach it to the living body, making it difficult to handle and wearing it for a long time. There were disadvantages such as causing discomfort to the patient when exposed to the air.

0004 On the other hand, for example, Utility Model Application Publication No. 2-1210, which was previously filed and published by the present applicant. As described in Publication No. 06, it is based on the undulation, which is a low frequency fluctuation component of the pulse wave. If the respiratory rate is measured using a relatively small pulse wave sensor, a relatively small pulse wave sensor can be placed in one place on the living body. Because you only need to put it on, it is easier to handle and reduces discomfort for the patient. It is thought that However, even in this case, there are still problems to be solved. Ru. In other words, the undulation of the pulse wave tends to be relatively large due to fluctuations in the patient's actual blood pressure value. If the undulation is tilted and there is a part without a peak, the respiration rate cannot be measured accurately. There was a problem.

[0005] This invention was developed against the background of the above circumstances, and its purpose is to Roha has developed a respiration rate measuring device that can more accurately measure respiration rate based on pulse wave undulations. It is about providing.

[0006]

[Means to solve the problem]

The gist of this invention to achieve the above purpose is to attach the device to the artery of the living body. It is based on the undulation, which is a low frequency fluctuation component of the pulse wave sequentially detected by the pulse wave sensor. Accordingly, it is a respiration rate measuring device that measures the respiration rate per unit time of the living body. , as shown in the complaint correspondence diagram in Figure 1, (a) the undulations for detecting the undulations of the pulse wave; a detection means; and (b) a predetermined undulation of the pulse wave detected by the undulation detection means. (c) average value calculation means for calculating the average value within the first period; and the swell of the pulse wave within a predetermined second period following the first period. (d) median value calculation means for calculating the median between the maximum value and the minimum value, respectively; The average is the difference between the average value in the first period and the median value in the first period. an average median difference calculation means for calculating a median difference; and (e) the first period and the second period. (f) a median difference calculation means for calculating a median difference that is a difference between median values of; If the absolute value of the median difference is smaller than the absolute value of the average median difference, 1 period and the second period using the undulation of the pulse wave within at least one of the second period. and respiration rate determining means for determining the respiration rate per unit time.

[0007]

[Effects of action and invention]

In a respiration rate measuring device having such a configuration, the pulse rate that is sequentially detected by the pulse wave sensor is The undulation, which is a low frequency fluctuation component of the wave, is detected by the undulation detection means, and the pulse wave is detected by the undulation detection means. An average value of the undulation within a predetermined first period is calculated by an average value calculation means. At the same time, the pulse wave within the first period and the second period following the first period. The median value between the maximum value and the minimum value of the waviness is calculated by the median value calculation means. It will be done. Also, the difference between the average value in the first period and the median value in the first period The average median difference is calculated by the average median difference calculation means, and The median difference, which is the difference between the median values between The absolute value of the median difference is determined by the respiratory rate determination means as the absolute value of the mean median difference. the pulse within at least one of the first period and the second period in the case where The number of breaths per unit time is determined using the swell of the waves. In this case, The absolute value of the median difference between the first period and the second period is the absolute value of the average median difference of the first period. If it is smaller than the value, it means that the pulse wave undulations in the first and second periods are mostly This is considered to indicate that there is no slope, etc., so the first period and Using pulse wave undulations with a small slope within at least one period of the second period This allows the respiratory rate to be measured more accurately.

[0008] In addition, instead of calculating the median difference between the first period and the second period, Find the mean difference, and the absolute value of the mean difference is smaller than the absolute value of the mean median difference. It is also possible to determine the respiration rate using the undulation of the pulse wave in this case. In this case, the mean difference is relatively less affected by noise than the median difference. Even if large noise is mixed in, the absolute value of the mean difference is smaller than the absolute value of the mean median difference. The measured respiration rate may be inaccurate because the respiration rate is determined by be. On the other hand, according to the respiration rate measuring device of the present invention, it is possible to The respiratory rate is determined when the absolute value of the median difference is less than the absolute value of the mean median difference. Therefore, even if the undulation of the pulse wave has almost no slope, a relatively large amount of noise will be mixed in. If the absolute value of the median difference is greater than the absolute value of the mean median difference, the respiratory rate will decrease. Since no decisions are made, noise effects can be better avoided and the respiratory rate can be measured more accurately. It is possible to determine the

[0009]

【Example】

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

0010 FIG. 2 is a diagram showing an example of the configuration of a respiration rate measuring device to which the present invention is applied. In the diagram 10 is a container-shaped housing, the open end of which is connected to the patient's body surface 12. It can be detachably attached to the wrist 16 by the band 14 while facing each other. ing. A pulse wave sensor 2 is installed inside the housing 10 via a diaphragm 18. 0 is provided to be relatively movable and protrude from the open end of the housing 10. A pressure chamber 22 is formed by the housing 10, diaphragm 18, etc. has been done. In this pressure chamber 22, pressure is supplied from a fluid supply source 24 through a pressure regulating valve 26. Pressure fluid such as air is supplied, and thereby the pulse wave sensor 20 is pressed against the body surface 12 with a pressing force corresponding to the pressure within the pressure chamber 22.

[0011] The pulse wave sensor 20 is made of a semiconductor chip made of, for example, single crystal silicon. A pressure sensitive element (not shown) such as a pressure sensitive diode is provided on the pressing surface 28. The pulse is a pressure vibration wave generated from the radial artery 32 and transmitted to the body surface 12. The pulse wave is detected and a pulse wave signal SM representing the pulse wave is supplied to the control device 34. Above pressure A pressure sensor 36 is provided between the chamber 22 and the pressure regulating valve 26. 6 supplies a pressure signal SP representing the pressure within the pressure chamber 22 to the control device 34. Main implementation In the example, the radial artery 32 corresponds to the artery in the claims.

0012 The control device 34 is a so-called microcomputer consisting of a CPU, ROM, RAM, etc. The CPU follows a program stored in advance in the ROM. Then, the signal processing is executed using the memory function of the RAM, and the pressure regulating valve 26 is driven to adjust the pressure. The pressure inside the force chamber 22 is adjusted, and based on the pulse wave signal SM obtained during the pressure change process. determine the pressing force of the pulse wave sensor 20 and hold it at the determined pressing force. At the same time, a pulse wave is detected at the pressing force, and low frequency fluctuations of the detected pulse wave are detected. Detects the component undulation and determines the patient's breathing rate based on the undulation of the pulse wave. Then, the determined respiration rate is sequentially displayed on the display 38.

[0013] Next, the operation of the respiration rate measuring device configured as described above is explained in the flowchart of FIG. Explain according to the following.

[0014] First, when the power is turned on and the start switch (not shown) is turned on, the step Step S1 is executed, and a suitable pressing force for the pulse wave sensor 20 is determined. It is held by the applied pressing force. That is, for example, the inside of the pressure chamber 22 is relatively gently moved. The pulse wave represented by the pulse wave signal SM, which is raised at a constant rate and collected sequentially during the pressure increase process. The pressure in the pressure chamber 22 when the pulse wave with the maximum amplitude is collected by calculating the amplitude of each The force is determined, and the pressure within the pressure chamber 22 is set to the determined pressure.

[0015] Next, step S2 is executed and the pulse wave signal SM is read to measure the respiration rate. be absorbed. Next, the upper peak value detection routine of step S3 is executed, and the upper peak value detection routine of step S3 is executed. In order to determine the upper peak value of the pulse wave represented by the pulse wave signal SM read in step S2, A well-known upper peak value detection algorithm is executed and the step By executing S4, the upper peak value detected in step S3 is By sequentially storing in a predetermined storage location in RAM, the low frequency fluctuation component of the pulse wave is The undulation to be represented is determined. In the following step S5, for the current respiration rate measurement, A preset period of time after reading of the pulse wave signal SM starts, for example, It is determined whether 30 seconds have elapsed. If a certain amount of time has not passed yet, Steps S2 to S5 are repeatedly executed, but continue after a certain period of time. Step S6 is then executed. Figures 4 and 6 were determined as described above. It is a diagram showing an example of the undulation of a pulse wave, and for example, the first section and the first section are shown every 10 seconds. It is divided into three sections: 2nd section and 3rd section. In addition, in FIGS. 4 and 6, , the pulse wave undulation is drawn as an envelope connecting each upper peak value data for convenience. Ru. In this embodiment, step S3 and step S4 are performed by the waviness detection method. Corresponds to the tier.

[0016] In step S6, the average value AV ₁ of the pulse wave undulation data in the first section and the average value AV ₂ of the pulse wave undulation data in the second section are calculated, and in the following step S7, The median values (average values of maximum value data and minimum value data) MI ₁ , MI ₂ , MI ₃ of pulse wave undulation data in the first section, second section, and third section are calculated, respectively. Next, step S8 is executed to calculate the average median difference ΔAM ₁ , which is the difference between the average value AV ₁ of the first interval and the median value MI ₁ , and the average value of the second interval An average median difference ΔAM ₂ is calculated, which is the difference between the value AV 2 and _the median MI ₂ . Next, by executing step S9, the median difference ΔMI ₁₂ , which is the difference between the median value MI ₁ of the first section and the median value MI ₂ of the second section, is calculated, and the median value of the second section is calculated. A median difference ΔMI ₂₃ is calculated, which is the difference between MI ₂ and the median MI ₃ of the third section. Therefore, in this embodiment, the above step S6 is used as an average value calculation means, the above step S7 is used as a median value calculation means, the above step S8 is used as an average median difference calculation means, and the above step S9 is used as a median value difference calculation means. When the first section is the first period, the second section corresponds to the second period, and when the second section is the first period, the third section corresponds to the second period.

In the next step S10, it is determined whether the absolute value of the median difference ΔMI ₁₂ between the first section and the second section is smaller than the absolute value of the average median difference ΔAM ₁ of the first section. . If this judgment is affirmed, the subsequent step S11 is executed, so that the absolute value of the median difference ΔMI ₂₃ between the second section and the third section becomes the average median difference ΔAM ₂ of the second section. It is determined whether it is smaller than the absolute value of . If this determination is affirmative, that is, if the determinations in step S10 and step S11 are both affirmative, it is considered that the undulations of the pulse wave are hardly inclined as shown in FIG. is executed and the respiration rate is determined based on the undulation of the pulse wave detected this time. However, if the determination in step S10 is negative or the determination in step S11 is negative, for example, as shown in FIG. As shown in the figure, it is conceivable that the undulation of the pulse wave has a large slope and there is no peak in the undulation, so the process returns to step S2 without determining the respiration rate based on the current undulation of the pulse wave. Therefore, in this embodiment, steps S10 to S12 correspond to the respiration rate determining means.

[0018] In the respiration rate determination routine of step S12 above, as shown in FIG. By first executing step SS1, the pulse determined in step S4 is Detection of the lower peak value of the wave undulation starts, and the detected lower peak value becomes the standard. Semi-lower peak value Pd^*After that, step SS2 is executed. Detection of the upper peak value is started, and the detected upper peak value is the standard upper peak value. Pu^*is determined as. Below standard peak value Pd^*and standard peak value Pu^*but After being determined, step SS3 is executed to determine the next lower peak value Pd. In the next step SS4, the below-standard peak value Pd^*and the lower peak value Pd The absolute value of is the below standard peak value Pd^*It is determined whether or not the value is within 20% of the value. this If the determination is negative, step SS5 is executed to avoid noise. The below standard peak value Pd^*The standard lower peak value Pd is the average value of the lower peak value Pd and the lower peak value Pd. ^* After is updated, steps SS2 and subsequent steps are executed again.

If the determination in step SS4 is affirmative, step SS6 is executed to determine the upper peak value Pu following the lower peak value Pd. Next, step SS7 is executed to determine whether the absolute value of the difference between the standard peak value Pu ^* and the upper peak value Pu is within 20% of the standard peak value Pu ^* . If this judgment is affirmative, step SS8 is executed, and the standard upper peak value Pu ^* and the upper peak value Pu determined in step SS6 are located next to the upper peak value Pu. It is determined whether the absolute value of the difference with the data value Dp is within 20% of the standard peak value Pu ^* . If this determination is affirmative, that is, if the determinations in step SS7 and step SS8 are both affirmative, step SS9 is executed and the upper peak value Pu determined in step SS6 is the second one. It is determined whether or not. If the determination in step SS9 is negative, the determined upper peak value Pu is the first one, so after the second upper peak value Pu is determined in step SS6, steps SS7 to SS9 are performed. executed again. At this time, the determination in step SS9 is affirmative, so by executing step SS10, the time (seconds) between the pair of upper peak values Pu is determined as the respiratory cycle T, and the unit time is calculated in the respiratory cycle T. For example, the number of breaths per minute is calculated by dividing by 60 seconds. Although not shown in the figure, in steps SS2, SS3, and SS6, even if a predetermined period of time (for example, 10 seconds) has elapsed due to lack of pulse wave undulation data, the standard peak value Pu ^* , lower If the peak value Pd and upper peak value Pu are not determined, the respiration rate determination routine is terminated.

[0020] The respiration rate is calculated in this way and the respiration rate determination routine in step S12 is completed. Once completed, the following step S13 is executed, and the respiration rate displayed on the display 38 is After the displayed value is updated to the value determined in step S12, the steps from step S2 onwards are performed again. The following steps are executed, and the measurement of the respiration rate continues in the same manner.

[0021] In this way, according to the respiration rate measuring device of this embodiment, the first section and the second section of the pulse wave undulation are Median difference ΔMI between two intervals₁₂The absolute value of is the average median difference ΔAM of the first interval₁of Median difference ΔMI between the second section and the third section that is smaller than the absolute value_{twenty three}The absolute value of Average median difference ΔAM in the second interval₂If the absolute value of the first interval is smaller than the absolute value of The number of breaths per unit time is determined using the pulse wave undulation within the third interval. In this way, the median difference ΔMI₁₂The absolute value of is the mean median difference ΔAM ₁ smaller than the absolute value of and the median difference ΔMI_{twenty three}The absolute value of is the mean median difference ΔAM₂of If it is smaller than the absolute value, as mentioned above, the pulse wave in the first to third sections is The curve is considered to have almost no slope based on actual blood pressure fluctuations, so The respiration rate can be measured more accurately using the pulse wave undulations.

[0022]Incidentally, conventionally, even when the pulse wave undulations have a relatively large slope and there are parts of the pulse wave undulations without a peak, the respiration rate can be measured using the pulse wave undulations. Therefore, as shown in Figure 7, for example, the determined breathing cycle T may be significantly larger than the actual value, and the measured value of the respiratory rate may be significantly smaller than the actual value, making the measurement of the respiratory rate inaccurate. There is. On the other hand, according to this embodiment, in the case of pulse wave undulations that are highly sloped and have no peak, the absolute value of the median difference ΔMI ₁₂ is the absolute value of the average median difference ΔAM ₁ , as shown in FIG. 6, for example. value, and the absolute value of the median difference ΔMI ₂₃ is larger than the absolute value of the average median difference ΔAM ₂ , so the pulse wave undulations with a large slope and no peak are excluded from the respiratory rate measurement target. The respiration rate is measured only on the basis of pulse wave undulations that have little slope, which makes the respiration rate measurement more accurate.

Further, according to this embodiment, the absolute value of the median difference ΔMI ₁₂ is smaller than the absolute value of the average median difference ΔAM ₁ and the absolute value of the median difference ΔMI ₂₃ is smaller than the absolute value of the average median difference ΔAM ₂ . Since the respiration rate is calculated based on the undulation of the pulse wave when the value is smaller than the value, there is an advantage that the influence of noise can be suitably avoided. In other words, the average difference between the first and second sections and the average difference between the second and third sections can be used instead of the median differences ΔMI ₁₂ and ΔMI ₂₃ . Since the difference in value is affected by noise more than the difference in mean value, when relatively large noise is mixed in, the absolute value of the difference in median value becomes larger than the absolute value of the difference in average median value, and the respiration rate is determined. Therefore, the influence of noise can be suitably avoided and the respiration rate can be measured more accurately.

[0024] Furthermore, according to this example, the undulation of the pulse wave suitable for measuring the respiration rate is determined. After that, the lower peak value Pd and the pair of upper peak values Pu are calculated from the undulation of the pulse wave. In determining the respiration rate, step SS4, step SS7, and step S In S8, whether or not the lower peak value Pd and the upper peak value Pu are noise. Since the respiratory rate can be determined, the measurement of the respiratory rate becomes more accurate.

[0025] Note that in the above embodiment, the undulation is detected based on the upper peak value of the pulse wave. However, the undulation may be detected based on the lower peak value of the pulse wave.

[0026] Further, in the embodiment, in step S5, the pulse rate is It is determined whether a certain period of time has passed since reading of the wave signal SM started. However, whether a predetermined number of upper peak values or lower peak values of the pulse wave have been detected. It can also be configured to determine whether or not.

[0027] Further, in the above embodiment, the pulse wave undulations for the determined fixed time are divided into three sections. The breathing rate is determined using the pulse wave undulations in these three sections. For example, claims It is divided into two sections corresponding to the first period and the second period in can also be configured to determine the respiration rate using the undulation in either section. However, there is no problem in dividing it into four or more sections.

[0028] Furthermore, in the embodiment, the respiration rate is calculated based on one respiration cycle. However, the respiration rate is calculated based on the average respiration cycle obtained by calculating multiple respiration cycles and averaging them. It is also possible to configure it so that it is emitted.

[0029] In addition, in the above example, the pulse rate per unit time is determined, and the pulse rate and respiration are calculated. In the respiration rate determination routine of step S12, from the predetermined relationship between the It may be configured to estimate whether the determined respiration rate is an abnormal value.

[0030] Further, in the embodiment described above, only the respiration rate is displayed on the display 38; The waveform of the pulse wave, pulse rate, etc. may also be displayed.

[0031] Furthermore, in the embodiment, the pulse wave sensor 20 is mounted on the radial artery 32. Of course, it may also be attached to other arteries such as the dorsalis pedis artery or carotid artery. It is.

[0032] In addition, various changes may be made to this invention without departing from its spirit. It is something.

[Brief explanation of drawings]

FIG. 1 is a complaint correspondence diagram.

FIG. 2 is a diagram showing an example of a respiration rate measuring device to which the present invention is applied, and is a diagram showing its configuration.

FIG. 3 is a flowchart for explaining the operation of the device in FIG. 2;

FIG. 4 is a diagram showing an example of the undulation of the pulse wave detected in the flowchart of FIG. 3, and is a diagram illustrating an example of the undulation of which the respiratory rate is to be measured.

FIG. 5 is a flowchart for explaining the respiration rate determination routine of FIG. 3;

6 is a diagram illustrating another example of pulse wave undulations detected in the flowchart of FIG. 3, and is a diagram illustrating an example of undulations with large slopes that are excluded from respiratory rate measurement targets.

FIG. 7 is a diagram showing an example of a respiratory cycle determined from the undulations of a pulse wave with a large slope using a conventional respiration rate measuring device.

[Explanation of symbols]

20 Pulse wave sensor 32 Radial artery (artery)

Claims (1)

[Scope of utility model registration request] 1. Respiration rate measurement that measures the respiration rate per unit time of a living body based on undulations that are low frequency fluctuation components of a pulse wave sequentially detected by a pulse wave sensor attached to an artery of the living body. The apparatus comprises: an undulation detection means for detecting the undulation of the pulse wave; and an average value calculation means for calculating an average value within a predetermined first period of the undulation of the pulse wave detected by the undulation detection means. , median value calculation means for calculating the median value between the maximum value and the minimum value of the undulation of the pulse wave within the first period and within a predetermined second period following the first period; average median difference calculation means for calculating an average median difference that is a difference between the average value in the first period and the median value in the first period;
median difference calculation means for calculating a median difference that is a difference between median values in a period and a second period; and when the absolute value of the median difference is smaller than the absolute value of the average median difference, the first A respiration rate measuring device comprising: respiration rate determining means for determining the respiration rate per unit time using pulse wave undulations within at least one of the period and the second period.