JP2001245871A - Doze judging device using saturation percentage of oxygen in artery blood in judging doze - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a traffic accident caused by a doze at the wheel. SOLUTION: The saturation percentage of oxygen in the artery blood (SpO2), one of biological data of human body, is used as a means for judging a doze. At the start of a doze, SpO2 lowers drastically; then after forming a minimum value, the SpO2 begins to rise and forms a maximal value. After that, the value lowers a little and comes near to a stable value before the start of the doze. The change of the value is a result of the interactions between the sympathetic nerve and the parasympathetic nerve. Therefore, the reproductivity is high and there is little difference by person, so the method using SpO2 is the most appropriate for judging a doze. The device using the method for judging a doze judges a doze by storing the standard curve of SpO2 indicating a doze in the device beforehand and comparing the curve and the change of SpO2 value in time at the time of driving a car. The device is comprised of an oxymetry function part using red light and infrared light and a comparator.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of attaching a probe having a sensor to a part of a living body to continuously and non-invasively measure the binding ratio between hemoglobin and oxygen in arterial blood. It relates to the application of a pulse oximeter, which is known in practice. 2. Description of the Related Art As a so-called drowsiness detection method at the time of driving in which the awake state shifts to a half-wake (drowsiness), a modified steering (angular) cycle method or an electroencephalogram method has been studied. Although none of these have been put to practical use at the experimental stage, they are referred to here as prior art. In the modified steering (angular) cycle method, when the driver enters a semi-wake state during driving, the frequency at which the driver operates the steering wheel to correct the course of the vehicle decreases, and as a result, the steering cycle is extended. Set the threshold in advance,
When this value is exceeded, it is determined that the person has entered half-wake. In addition, the EEG method detects the Alpha wave in the EEG by waveform analysis and compares it with the beta wave that appears frequently during awakening,
This is a method for determining half awakening. On the other hand, there is also a method of judging half-wake by observing a time interval variation (RR interval variation) of a driver's heartbeat. Furthermore, there is a method of video-taking a blink of an eye (blink) and judging half-wake from the opening and closing of the eye. All of these depend on the characteristics of the driver's driving technique and the personal qualities of the driver, and it is difficult to determine the threshold value for the half-wake determination, and lacks versatility. In addition, the modified steering cycle method, the blink method, and the like are indirect as parameters for determining arousal, and similarly lack versatility. [0004] Furthermore, the brain wave detection method considered to be more direct requires a high-level analysis in a method of separating alpha waves from observed waveforms. In any case, according to the conventional technology, it cannot be said that it is a simple, versatile, and accurate method for detecting half-wake (sleeping). [0005] Regarding the pulse oximeter, as a conventionally known technique, Japanese Patent Publication No. 53-26437 and Japanese Patent Publication No.
There is one disclosed in JP-A-11-11097. In the present invention, the pulse oximeter is used as a part of the function of the present invention by utilizing the arterial oxygen saturation as a parameter for determining arousal, but is not a pulse oximeter itself. In this sense, the present invention does not extend from the prior art. [0006] The following conditions must be satisfied in order to accurately determine a half-wake and use it as a half-wake detection device or a warning device for general use. It is possible to accurately judge when the transition from awake to semi-awake. There is no difference in the judgment result depending on the individual difference. It is possible to directly detect the half-wake biometric information that allows early judgment of entering semi-wake (until it is judged to be indirect information) (It takes a long time and the accuracy is lowered.) The configuration of the detection device is simple (lower cost, and eventually leads to general use). Must be satisfied. However, the above-mentioned conventional methods, such as the modified steering cycle, brain wave detection, and blink observation, do not satisfy the above conditions. [0007] In order to satisfy and detect various problems that have been delayed in the first half of awakening (drowsiness), it is first necessary to directly detect biological information as a target for sensing. is there. One of the human functions directly controlled by the sleep center is breathing. This respiratory state is directly controlled through the nervous system by the hypothalamus of the cerebrum, which is the sleep center.
The arterial oxygen saturation, which is a detection parameter according to the present invention, is a direct reflection of the respiratory condition. [0008] When a human is attacked by sleep (a signal is emitted from the cerebrum), a change in respiratory volume occurs. Early in the sleep,
That is, the respiratory volume decreases at the stage of transition from awake to semi-awake. Accordingly, SpO2 slightly decreases. When the state of respiratory decline continues, a protective function acts on the living body (relationship between sympathetic nerve and accessory sympathetic nerve), and SpO2 slightly recovers, and after a long time, recovers to near the initial value. Purely from a medical point of view, the decrease in respiratory volume is compensated for by improving the oxygen uptake function, indicating a compensatory action and a restorative action of the human body. On the other hand, when the state changes from semi-awakening to awakening (wake up), on the other hand, the respiratory volume increases sharply, but SpO2 instantaneously (suddenly increases) due to the similar protective action of the living body. ) It increases after decreasing, forms a maximum value (peak), then gradually decreases and approaches a certain value. This constant value is often an initial value. In any case, in response to the sleep / wake signal of the living body, SpO2 overshoots in a positive (increase) direction or a negative (decrease) direction, and has a peculiar pattern approaching a certain stable constant value. . In the present invention, attention was paid to the temporal change of SpO2 in response to the command of the cerebral sleep / wake center. In addition, in the awakening / semi-awakening / awakening cycle described above, there are several methods for determining a half-wakefulness. That is, the appearance of a pattern that overshoots and decreases after the initial decrease and then increases thereafter is determined to be dozing (semi-awakening). A further method is that after the appearance of the first dozing pattern described above, the onset of dozing, including the above-mentioned sudden decrease (overshoot), increase (formation of a peak), and a gradual decrease that appears when awake, including a stable pattern. to decide. This assumes that light snoozing always accompanies wakefulness (driving is considered to be closest to this). The last method considers the above semi-awakening / wakening pattern as one, and determines the appearance of dozing with the appearance of a plurality of these. Which of the above three methods should be used depends on the required measurement accuracy, the required time until the determination, the memory capacity of the determination device of the present invention, the allowable complexity of the device configuration, and the like. Is determined by Next, a means for solving the problem will be described with respect to a drowsiness judging device for judging drowsiness by using any of the above judgment methods. As described above, the original form of the present invention can be found in a conventional pulse oximeter, but here, in order to avoid complexity, only differences from the conventional apparatus of the present invention will be mainly described. Unless otherwise described, a conventional pulse oximeter is used. When a part of the living body, such as a fingertip, an ear lobe, or the like, is irradiated on a part of a living body, when passing through an artery, a part of the infrared ray is different depending on hemoglobin (Hb) constituting red blood cells or a complex of hemoglobin and oxygen (HbO2). It is absorbed to a certain degree and has wavelength dependence. It has so-called spectral characteristics. However, by fixing the wavelength of the infrared ray, it has a value specific to the target substance. Thus, the oxygen saturation can be obtained. The oxygen saturation curve used for the above determination is obtained by accumulating and displaying the oxygen saturation with respect to time. In the conventional oximeter, if the SpO2 value that changes every moment can be displayed on the display at each moment, the basic performance is secured. However, the present invention provides means for solving the problem by adding various new functions which are not heretofore described. The first is a function of storing the SpO2 value at the start of falling asleep at the time {not at the time of riding in a car) for a specific individual at the time {at time} in a memory element. This function is conventionally achieved by a semiconductor memory device. By making these stored measured values continuous over time, one oxygen saturation curve is obtained. Here, this is called a standard (reference) curve. Next, a similar oxygen saturation curve can be obtained with the start of falling asleep during driving. The function according to the present invention is constituted by a comparator (comparator) for comparing the similarity between a plurality of oxygen saturation curves obtained in this manner. In actual application of the present invention, a reference curve stored in advance is compared with a characteristic curve measured during driving, and the above-mentioned semi-wake (sleeping) is determined from the similarity. At this time, the individual difference is almost completely removed, and the accuracy of the dozing determination is improved. As another method, instead of obtaining a reference curve, there is a method of collecting SpO2 changes in a large number of people's homes and storing a typical curve as a reference curve.
As one of the methods, there is a method of defining a difference between a local minimum value and a local maximum value at each time point. At this time, although the judgment accuracy is slightly reduced, the SpO2 method does not largely differ between individuals and is within an acceptable range. Moreover, since the reference curve stored in advance is used, there is no need for each person to collect the reference curve. In any case, since the comparison with the reference curve is required, it is necessary to have a comparator as a new circuit function. First Embodiment First, a series of measured values of SpO2 from the start of falling asleep to the time of awakening are shown in FIG. 1 as an example. In the figure, the left half starts falling asleep and then stabilizes.
The right half shows the time from the start of awakening to the stabilization. Next, these will be described sequentially. First, the dozing part, but when awake, S
It takes the first stable value of 98% pO2, but starts to decrease greatly in about 30 seconds from the start of falling asleep, and reaches the first minimum value in about 1 minute. After a while, it began to increase over time,
At 1 minute and 50 seconds, the first local maximum is reached and then decreases to the second stable value. When the dozing state continues, SpO2
The value keeps about this stable value. On the other hand, in the awakening part on the right side, after the start of awakening, it suddenly drops from the second stable value to form a second minimum value, and then suddenly exceeds the first stable value. After increasing and forming the second maximum, it gradually decreases and takes on the same third stable value as the first stable value. When the awakening continues, the fluctuation is small with substantially the third stable value. In the above, an example of the transition of SpO2 in one cycle from awakening to dozing to further awakening has been described. Next, an embodiment of the two dozing start determination method according to the present invention will be described. First, the first part is the left part of the figure, that is, of SpO2 from the first stable value to the second stable value, the first stable value, the first minimum value, the first maximum value, the second stability value. Each acceptable range of values
A standard value is determined with reference to the dozing data of a large number of persons surveyed in advance, stored in a storage element in the device, and this is compared with SpO2 obtained during driving, and a high similarity drowsiness is determined. Judge as driving. At this time, instead of the standard value, a method of storing SpO2 data at the time of falling asleep of a specific individual using the device as a reference curve in the device according to the present invention and comparing this with the SpO2 value obtained during driving may be used. . The second is to add the SpO2 value at the time of awakening of the right part to the left part of the figure, that is, judge drowsiness from the first stabilization to the third stabilization in the same manner as the first method. May be. This assumes that dozing is light sleep and that dozing is accompanied by arousal. In a similar sense, the second dozing above
If it is considered that the characteristic of dozing is that one cycle of awakening is repeated a plurality of times, the doping may be determined by comparing the plurality of changes in SpO2 with a reference value and a reference curve in the same manner as above. Embodiment 2 FIG. 2 shows the SpO2 and the pulse rate when shifting from the awake phase to the dozing phase. The transition of SoP2 is similar to that of FIG. 1, but the pulse rate is 70
Fluctuates around the center, and decreases greatly with the start of falling asleep. At the beginning of this decrease, the amplitude is slightly large as shown in the figure, but the amplitude decreases over time. The above pulse rate change is peculiar to the drowsiness start period, and the drowsiness determination is performed in combination with SpO2. That is, this method is a method in which a drowsiness start is predicted from a drop in the pulse rate very early in the drowsiness start, and a drowsiness start is determined when the drowsiness start is determined later from SpO2. Embodiment 3 FIG. 3 shows the relationship between SpO2 and pulse interval fluctuation when shifting from awake to dozing. The pulse interval fluctuation fluctuates significantly at the very beginning of falling asleep, and attenuates with time as shown in the figure. Here, this initial fluctuation is regarded as a sign of the start of dozing, and SpO2 obtained late
This is a method of determining that a dozing start has occurred when it is confirmed that the dozing has started. Embodiment 4 Next, using the dozing determination method according to the present invention,
FIG. 4 shows an embodiment of the dozing determination device according to the present invention. In the figure, the SpO2 signal processing / control unit such as an optical probe unit serving as a SpO2 detection unit, a microcomputer unit, an AD conversion unit, and a display unit including an alarm device, as well as reference data and a reference curve are compared with the measured data. Arithmetic CPU ". Here, the least squares operation CPU is shown as an example of the comparison circuit as an example, but the comparison circuit block may be replaced by another method. The point is that this part is composed of a comparison circuit. For example, if it has a function of comparing the basic waveform of dozing / wake and the reference data / reference curve shown in [First Embodiment] It is an invention. When the comparison circuit section determines that the vehicle is dozing, the driver / passenger is notified of the drowsy driving by displaying a character or using an alarm device such as a buzzer. The present invention is a car society, and the number of registered cars is 700.
It has reached 100,000 units. On the other hand, the lifestyle has more opportunities to be active at night, and it is said that 16% of accidents are caused by dozing off. The number of traffic fatalities is as high as 9000 per year, of which the proportion due to drowsy driving will further increase. Or
In such a social environment, prevention of driving accidents falling asleep is a social demand. Become the present invention "new doze (semi-awakening)
By using the "Drowsiness determination device using the determination method", the driver and the passengers can clearly recognize that they are falling asleep by using the display device and the alarm device, and take a break at an appropriate place. By taking appropriate countermeasures such as urging the driver to sleep, it is possible to prevent traffic accidents and fatal accidents caused by falling asleep.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the elapse of time from the stable state of arterial blood oxygen saturation (SpO2) at the time of awakening to the beginning of falling asleep and the time of awakening again. FIG. 2 Pulse rate / S at the time of transition from awake to dozing
4 shows the relationship between pO2 and time. FIG. 3 shows the relationship between pulse interval fluctuation / SpO2 and time when awakening transitions to dozing. FIG. 4 shows a block diagram of the device according to the invention.

Claims (1)

Claims 1. An arterial blood oxygen saturation (SpO2) of a human awake state obtained by an oximetry method using two or more light irradiations after a certain stable value is obtained. From this stable value, it increases once with time and then decreases, or has a pattern that decreases with time from a certain stable value, further decreases with time, increases to the first minimum value, then increases to the first maximum value. A method of judging that the person has entered a doze (semi-wake) from awakening when he enters a decreasing trend and then takes a certain second stable constant value (see the left part of FIG. 1). 2. After forming the last second stable value in the pattern of claim 1, it continues to decrease, and then increases rapidly after forming the second minimum value to increase the second maximum value. A stable value that is less than a certain first stable value or decreases and approaches a substantially same third stable value (see the right part of FIG. 1). At this time, when the right part of FIG. 1 appears in addition to the change of SpO2 shown in the left part of FIG. 1, it is determined that the person has fallen asleep (semi-awake) from awakening. 3. A method for judging that the person has entered a doze (semi-wake) from awake when the pattern of claim 2 is repeated a plurality of times. 4. The method according to claim 1, 2 or 3, wherein other organisms having oxygen saturation other than humans are similarly judged. 5. A pulse rate and a pulse waveform obtained by an oximetry method using two or more light irradiations, wherein a decrease in the pulse rate from the time of awakening is observed, and a decrease in the amplitude of the pulse waveform is observed. A method for determining a drowsiness that concludes that the user has fallen asleep in combination with the drowsiness determination method according to any one of claims 1 to 4, when one or both of the pulse interval variations are simultaneously observed. 6. An oximetry method for irradiating arterial blood with two or more red light / infrared rays and determining a change in absorbance to determine oxygen saturation of arterial blood.
A function for obtaining O2, a function for storing the time change of SpO2 at time intervals, and a reference curve set in advance corresponding to each claim in order to determine claims 1 to 4 from the stored numerical value group. And a comparator for comparing the similarity with the stored numerical value group, a function for displaying that a semi-wake (sleep) has been entered as a result of these determinations, and a buzzer for notifying by an alarm Judgment device. It is not necessary that the display function and the alarm function coexist. Further, the display unit may display the SpO2 value and the pulse rate. 7. An oximetry method for irradiating arterial blood with two or more red light / infrared rays and determining a change in absorbance to determine arterial oxygen saturation.
The function of obtaining O2, the function of storing the time change of SpO2 at time intervals, and the difference between the first stable value and the first minimum value to determine Claims 1 to 4 from the stored numerical value group. The difference between the first minimum value and the first maximum value, the difference between the second stable value and the second minimum value, the difference between the second minimum value and the second maximum value, and the stored numerical value group. A drowsiness judging device comprising a comparator for comparing similarities, a function of displaying that the person has entered a half-wake state (drowsiness) as a result of these judgments, and a buzzer for giving an alarm. Note that the display function and the alarm function do not need to coexist, as in the previous section. Further, the display unit may display the SpO2 value and the pulse rate. 8. A dozing determination device having a comparator according to claim 6.
A dozing determination apparatus having a comparator for comparing the SpO2 with the pulse rate reduction or the pulse waveform amplitude reduction or pulse interval variation shown in claim 5 as a comparison item.