JPH0622325Y2 - Respiratory rate measuring device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a respiratory rate measuring device for measuring a respiratory rate based on a change in peak value of a pulse wave.

Conventional technology and its problems Medical professionals such as doctors generally measure and relate the respiratory rate in order to accurately grasp the state of a living body such as a patient undergoing surgery. Conventionally, when measuring the respiratory rate, a method of detecting a change in the chest circumference of the living body or a method of detecting the chest impedance has been adopted, but in order to implement such a method, the device is relatively large and complicated. There was a drawback that it was troublesome to handle.

On the other hand, as a result of various studies, the present inventor discovered that there is a specific relationship between the change in the curve connecting the peak values of the pulse wave and the respiratory rate. The present invention has been made based on such findings, and an object thereof is to provide a smaller respiratory rate measuring device.

Means for Solving the Problems To achieve the above object, the gist of the present invention is (a) a pulse wave sensor for detecting a pulse wave generated from an artery of a living body, and (b) the pulse wave Peak value detection means for obtaining the peak value of the artery output from the sensor, and (c) the change period of the curve connecting the peak values detected by the peak value detection means or the unit change of the periodic change of the peak value per unit time. Respiratory rate determining means for determining the respiratory rate of the living body based on the number of times.

In this way, the peak value of the pulse wave detected by the pulse wave sensor is determined by the peak value detection means, and the respiratory rate determination means changes the cycle or cycle of the curve connecting the peak values. The respiratory rate is determined based on the number of dynamic changes per unit time. Therefore, according to the present invention, since the breathing rate can be obtained by mounting the pulse wave sensor on the living body, there is an effect that the entire apparatus is significantly downsized as compared with the conventional one.

Moreover, since the pulse wave sensor is similar to that used for a blood pressure monitor, a pulse waveform monitor, etc., when the blood pressure monitor or pulse waveform monitor and the respiratory rate measuring device are combined, the pulse wave sensor is shared. There are advantages.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram for explaining the configuration of the respiratory rate measuring device of this embodiment and the pulse wave detecting device coupled thereto. A pulse wave detection probe 16 is fastened by a support band 14 on the epidermis of a part of the living body such as a wrist and directly above the artery 12 located near the skin of the living body. The pulse wave detecting probe 16 is inserted between the housing 18 and the pulse wave sensor 20, and the pulse wave sensor 20 housed inside the housing 18, the housing 18 having a relatively high rigidity with a bottom surface opened. The pulse wave sensor 20 with respect to the housing 18 and the airtight pressure chamber 2 inside the housing 18.
2 and a rubber diaphragm 24 that forms part 2. A pipe 26 is connected to the housing 18, and a pressure fluid from an electric pump 28 connected to the pipe 26 is regulated by a pressure regulating valve 30 controlled by a microcomputer 34 described later and supplied into the housing 18. It is supposed to be done. That is, the housing 18
When the pressure fluid is supplied from the electric pump 28, the diaphragm 24 is expanded as the pressure in the pressure chamber 22 rises, and the pulse wave sensor 20 is also pressed against the living body. The pulse wave sensor 20 including a semiconductor pressure detecting element detects a pulse wave which is a pressure vibration wave generated in the artery 12 when pressed against a living body, and a pulse wave signal representing the pulse wave. The SM is output to the microcomputer 34. Housing 1
A pressure sensor 32 is connected between 8 and the pressure regulating valve 30 and outputs a pressure signal SP representing the pressure in the pressure chamber 22 to the microcomputer 34.

The microcomputer 34 includes a CPU, RA (not shown).
CPU equipped with M, ROM, interface, etc.
Uses the temporary storage function of RAM to process the input signal according to the program stored in ROM in advance, and the pressure chamber 2
The fluid pressure in 2 is adjusted. That is, the microcomputer 34 operates the pressure regulating valve 30 in response to the operation of the start push button (not shown) to move the electric pump 28 to the pressure chamber 22.
The pressure of the pulse wave signal SM,
For example, the amplitude, signal power, etc. are calculated and the pulse wave signal SM is calculated.
Is detected, and when saturated, the pressure regulating valve 30 is operated by feedback control so that the pressure is maintained. Further, the CPU uses the pulse wave signal SM
The blood pressure value is determined based on the above, and the blood pressure value is displayed on the display 36 together with the pulse waveform. The upper peak value of the pulse wave corresponds to the systolic blood pressure value, and the lower peak value of the pulse wave corresponds to the diastolic blood pressure value. Is determined. Further, since the pulse wave shape displayed on the display 36 as described above represents arterial pressure, it is utilized as various medical information.

Further, the CPU stores the upper peak value in the RAM each time the pulse wave is detected, and obtains the envelope 38 connecting the upper peak values. This envelope 38 is the second
As shown in the figure, it periodically changes up and down, and this cyclic change corresponds to the respiration of the living body. That is, during the inspiration period of the living body 10, since the heart is compressed due to the expansion of the lung volume, the upper peak value and the lower peak value of the pulse wave become relatively low, and the heart is not compressed during the expiration period. Since both peak values are relatively high because they are loosened, the respective peak values C ₁ , C ₂ , C ₃ ... Of the envelope 38.
.. The time between C _n , that is, the change period T _{1 of} the envelope 38,
T _{2, T} 3 respiratory rate based on ···· _{T n-1} is being asked. Therefore, in this embodiment, a part of the microcomputer 34 corresponds to the peak value detecting means and the respiratory rate determining means, and the envelope 38 corresponds to the curve.

The operation of this embodiment will be described below with reference to the flowchart of FIG.

When a start push button (not shown) is pressed and the power is turned on, first, in step S1, the pulse wave signal SM detected by the pulse wave sensor 20 is read. In the next step S2, the difference between the amplitude value of the pulse wave signal SM read in the current cycle and the amplitude value of the pulse wave signal SM ⁻¹ read in the previous cycle (SM-S
It is determined whether or not (M ⁻¹ ) is smaller than a predetermined value α. This is to determine whether or not the magnitude of the pulse wave signal SM is saturated, and in the saturated state of the pulse wave signal SM, even if the pressing force on the pulse wave sensor 20 is increased, the adjacent pulse is detected. It is based on the fact that there is no greater difference than the very small value α between the amplitude values of the wave signal SM. Initially, the magnitude of the pulse wave signal SM is not saturated, so the determination in step S2 is denied and step S3 is performed.
Through step S5 is executed. That is, the value P obtained by adding a relatively small predetermined pressure ΔP to the pressure P ⁻¹ in the pressure chamber 22 in the previous cycle stored in the RAM in the microcomputer 34 is determined, and the pressure chamber 2
After the pressure fluid is supplied into the pressure chamber 22 so that the pressure in 2 reaches the fluid pressure P, P ⁻¹ indicating the previous fluid pressure is updated to the current value P in preparation for the next cycle. Is done. Then, when it is determined in step S2 that the pulse wave signal SM is saturated in the process in which the operation of steps S1 to S5 is repeated and the fluid pressure P in the pressure chamber 22 is increased by ΔP, steps S6 to steps are performed. S8 is executed respectively. In step S6, the fluid pressure P ^-1 stored in step S5 is determined as the fluid pressure P in the pressure chamber 22, and the subsequent step S6.
In 7, the pulse waveform of the pulse wave signal SM read in step S1 is displayed, and at the same time, the maximum and minimum blood pressure values are determined and displayed based on the pulse wave signal SM.

Next, the breathing rate determination routine of step S8 is executed. As shown in FIG. 4, in the respiratory rate determination routine, in step SS1, the upper peak value M _n of the current pulse wave represented by the pulse wave signal SM and the upper peak values M _n−1 , M of the previous pulse wave are represented.
_It is determined whether or not the upper peak value C _n in the envelope 38 connecting _n−2 , M _n−3, ... Has been obtained. When the upper peak value C _n is not obtained, the respiratory rate determination routine ends, but when the upper peak value C _n is obtained, step SS2 is executed and the upper peak value C _n determined this time is determined. The time between the immediately preceding upper peak value C _{n−1, that} is, the change period T _n−1 of the upper peak value of the envelope 38 is obtained. In the subsequent step SS3, the average cycle Tave of the change cycle Tn _-1 determined this time and the immediately preceding two change cycles Tn _-2 and Tn _-3 is calculated. Then, step SS4 is executed, the respiratory rate B is determined from the following equation (1) based on the average period Tave, and is displayed on the display 36.

B = unit time / Tave (1) That is, assuming that the unit time is 1 minute, the respiratory rate becomes 15 when the average period Tave is 4 seconds.
Then, by subsequently executing steps S4 and S5, the pressure is adjusted so that the fluid pressure P in the pressure chamber 22 is maintained, and the fluid pressure P ⁻¹ is updated again. In the process of repeating the above operation, when the magnitude of the detected pulse wave is significantly changed due to the fluctuation of the pressing force on the pulse wave sensor 20 due to the body movement of the living body, etc. The determination in S2 is denied, and the pressing force is feedback-controlled in steps S3 to S5. The judgment reference value α in step S2 is set to a large value so that it does not react to a normal fluctuation of the magnitude of the pulse wave.

As described above, in the present embodiment, the respiratory rate is determined based on the change period of the envelope 38 connecting the upper peak values of the pulse waves detected by the pulse wave sensor 20 attached to the living body. The entire device is significantly downsized as compared with the conventional one.
Moreover, according to this embodiment, the pulse wave sensor 20 is shared,
There is an advantage that the blood pressure monitor or pulse waveform monitor and the respiratory rate measuring device can be combined.

Another embodiment of the present invention will be described below. In addition,
The same parts as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted.

For example, in the above-described embodiment, the respiratory rate is calculated by obtaining the period between the peaks of the envelope 38 and dividing the unit time by the period, but instead of this,
The number of occurrences K of the upper peak of the envelope 38 per predetermined time U
Alternatively, the respiratory rate B may be calculated according to the following equation (2).

B = K × (60 sec / U) (2) In the above-described embodiment, the respiratory rate is determined using the peak value of the envelope 38 that connects the upper peak values of the pulse wave.
Instead of this, an envelope connecting the lower peak values of the pulse wave may be used. Further, of the envelope curve of the upper peak value and the envelope curve of the lower peak value, the one that more accurately corresponds to the respiratory rate may be selectively used.

Further, an abnormal pulse wave mixed with a normal pulse wave may be removed. If an abnormal pulse wave such as noise is mixed into the normal pulse wave, the correspondence between the envelope connecting the peak values and the breathing will collapse, so removing the abnormal pulse wave will increase the respiratory rate. There is an advantage that it can be obtained more accurately.

Further, in the above-described embodiment, the blood pressure monitor and the pulse waveform monitor are combined, but it goes without saying that the respiratory rate measuring device may be used alone or may be combined with another device.

The above description is merely one embodiment of the present invention, and the present invention can be variously modified without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the configuration of a breathing rate measuring apparatus according to an embodiment of the present invention when it is used in combination with a blood pressure monitoring apparatus and a pulse waveform monitoring apparatus. FIG. 2 is a time chart showing a pulse wave and an envelope connecting the upper peak values of the pulse wave. FIG. 3 is a flow chart for explaining the operation of the apparatus shown in FIG. FIG. 4 is a flow chart for explaining the respiratory rate determination routine of FIG. 12: Artery 20: Pulse wave sensor 34: Microcomputer 38: Envelope (curve)

Claims (1)

[Scope of utility model registration request] 1. A pulse wave sensor for detecting a pulse wave generated from an artery of a living body, a peak value detecting means for obtaining a peak value of a pulse wave output from the pulse wave sensor, and a peak value detecting means. Respiration rate determining means for determining the respiration rate of the living body based on the change period of the curve connecting the detected peak values or the number of periodic changes of the curve per unit time, and a respiration rate characterized by comprising: measuring device.