JPH058974Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] This invention places a light-emitting element on one side of a measurement site such as a fingertip or an earlobe, and a light-receiving element on the other side. This relates to a pulse oximeter that measures the oxygen saturation level in the blood.

[Conventional technology]

The frequency of use of pulse oximeters is rapidly increasing in patient management during anesthesia and postoperatively, but in the case of subjects with peripheral circulatory insufficiency, low temperature Occasional cases of burns have been reported.

[The problem that the idea aims to solve]

In view of this point, it is an object of the present invention to provide a pulse oximeter that can prevent low-temperature burns caused by heat generation of light emitting elements.

[Means to solve the problem]

In order to achieve this object, the present invention includes a temperature sensor disposed near the light emitting element so as to be in contact with the measurement site, and a temperature detected by the temperature sensor that can cause low-temperature burns. The temperature rise determination means compares the temperature with a reference temperature corresponding to the temperature and outputs an abnormal temperature signal when the reference temperature is reached, and the notification means reports an abnormality in response to the abnormal temperature signal.

In order to start the measurement after confirming that the measurement site is set, according to claim 2, a light amount reduction detection that detects that the amount of light incident on the light receiving element is reduced due to the setting of the measurement site compared to when it is directly irradiated. Provide means.

In order to avoid measuring the temperature detected by the sensor in a non-equilibrium state, according to claim 3, the start of operation of the rising temperature determining means is delayed in response to turning on the device switch or a detection signal from the light amount reduction detecting means. A timer means is provided. According to claim 4, instead of the timer means, temperature equilibrium detection means may be provided for calculating a temperature change curve in which the sensor detected temperature moves toward a temperature equilibrium state after the measurement site is set, and detecting the point in time when the sensor-detected temperature reaches the equilibrium temperature. good.

In order to make a highly accurate judgment based on the subject's body temperature, according to claim 5, a temperature rise due to heat generated by the light emitting element is measured in addition to the temperature sensor disposed near the light emitting element so as to be in contact with the measurement site. Providing another temperature sensor that is placed in contact with the measurement site at a position spaced apart from the light emitting element to an extent that does not cause
The temperature rise determining means is configured to detect a temperature difference between both temperature sensors and output an abnormal temperature signal when this temperature difference exceeds a reference temperature difference.

To automatically avoid low temperature burns, claim 6
A temperature sensor is placed near the light emitting element so as to make contact with the measurement area, and the detected temperature detected by this temperature sensor is compared with a reference temperature that is unlikely to cause low-temperature burns, and an error signal is output. The device includes an error signal generating means and a drive current control means for increasing or decreasing the drive current of the light emitting element in response to the error signal.

According to claim 7, in order to perform automatic control with high precision in accordance with the body temperature of the subject, in addition to the temperature sensor disposed near the light emitting element so as to be in contact with the measurement site,
Another temperature sensor is provided that is placed in contact with the measurement site at a distance from the light emitting element to an extent that does not cause a temperature rise due to heat generated by the light emitting element, and the error signal generating means is configured to measure the temperature between both temperature sensors. It is configured to compare the difference with a reference temperature difference and output an error signal.

In order to predict the equilibrium temperature and quickly detect the possibility of low-temperature burns, according to claim 8, the invention of claim 1 includes calculating a temperature change curve in which the sensor-detected temperature moves toward a temperature equilibrium state after the measurement site is set. Equilibrium temperature prediction means for predicting the equilibrium temperature is provided, and the temperature rise determination means is made to compare the predicted equilibrium temperature with a reference temperature. Similarly, in addition to the temperature sensor placed near the light-emitting element so as to make contact with the measurement site, there is also a temperature sensor placed in contact with the measurement site at a distance from the light-emitting element that does not cause a temperature rise due to the heat generated by the light-emission element. In the case where another temperature sensor is provided, according to claim 9, the temperature difference detected by both temperature sensors calculates a temperature difference change curve in which the temperature difference shifts toward a temperature equilibrium state after the measurement site is set, and the equilibrium temperature difference is calculated. A means for predicting an equilibrium temperature difference is provided, and a rise temperature determining means is used to compare the predicted equilibrium temperature difference with a reference temperature difference corresponding to the possibility of causing low-temperature burns, and detect an abnormality when this reference temperature difference is reached. Configure to output a temperature signal.

[Effect]

According to claim 1, the abnormally increased temperature determining means:
Comparing the temperature detected by the temperature sensor that is in contact with the skin near the light-emitting element with the reference temperature, it is determined that if the temperature exceeds this temperature there is a possibility of causing low-temperature burns. Alert with sound.
In this case, according to claim 2, the light amount reduction detection means functions as a set sensor for the pulse oximeter of the measurement site, so that the measurement is performed in a normal measurement state, and according to claim 3, the device power supply Measurement is performed after the timer time has elapsed after turning on the device, or after setting the measurement site and turning on the power. According to claim 4, the measurement is performed after the sensor-detected temperature reaches an equilibrium state in a normal measurement state.

According to claim 5, the temperature rise is measured based on the subject's body temperature detected by another temperature sensor.

According to the sixth aspect of the present invention, the drive current of the light emitting element is feedback-controlled to a constant light emission amount in accordance with the temperature rise of the measurement site so as not to cause low-temperature burns. According to claim 7, feedback control is performed to maintain a constant temperature difference based on the subject's body temperature detected by another temperature sensor.

According to claim 8, when the temperature detected by the temperature sensor is moving from a transient temperature to an equilibrium state in the state where the measurement site is set at the time of starting or restarting measurement, the equilibrium temperature is predicted and compared with the reference temperature. will be held. According to claim 9, the measurement is likewise carried out while the transient temperature difference is on its way to an equilibrium state.

〔Example〕

FIG. 1 is a diagram showing the configuration of a fingertip-attached pulse oximeter according to an embodiment of the present invention.

In the figure, numerals 1 and 2 are light emitting elements attached to a probe 9 (partially shown) set on a fingertip 8, and alternately emit light of different wavelengths. Reference numeral 3 designates a light-receiving element that is similarly attached to the probe 9 so as to face the probe 9 so as to receive the amount of light transmitted through the fingertip 8 in response to these light emissions. A circuit device 4 is attached to these elements, and the blood oxygen saturation level is determined by a well-known method from the ratio of the amounts of transmitted light. Then, the probe 9 is placed on the fingertip 8.
When the finger tip 8 is not set, the temperature rise in the measurement area due to the light emission is about 5°C, and when the finger tip 8 is set, the temperature rise remains at about 2.5°C if normal heat dissipation occurs.

Both light emitting elements 1 and 2 in this probe 9
In between, according to the present invention, a thermistor 10 as a temperature sensor is attached so as to be in contact with the fingertip 8. The light-receiving element 3, as a part of the circuit device 4, has a probe 9 set on the fingertip 8 to be in a light-transmitting state, thereby functioning as a light amount reduction detection means for detecting a state in which the amount of received light has been reduced from the direct irradiation state. A comparator 11 is attached, followed by a timer 12 which starts timing in response to the output signal of this comparator. This timer outputs a timer signal when, for example, 5 minutes have elapsed so that even if the power switch is turned on in advance and the thermistor 10 is set in a state where the temperature is rising, the temperature equilibrium state can be reached.

Similarly, as part of the circuit device 4, the thermistor 10 is connected to the thermistor 10 after the timer signal is generated.
A comparator 13 that outputs an abnormal temperature signal when the detected temperature reaches a limit value of about 40°C to 60°C, which may cause low-temperature burns, for example, a reference temperature of 40°C, and the detected temperature. A temperature display 14 is attached to the comparator 13 for monitoring the temperature, and a display 15 is attached following the comparator 13 for notifying an abnormality with light in response to an abnormal temperature signal. The temperature rise determination means may be configured by using the CPU of the circuit device 4 for calculating the oxygen saturation value instead of the comparator 13.

During measurement, when the probe 9 is attached to the fingertip 8, the temperature of the thermistor 10 rises toward the body temperature, as shown in FIG. 2, and when the device switch is turned on and starts emitting light, The comparator 11 immediately detects a low light amount state due to the light passing through the fingertip 8, starts the timer 12, and starts measuring the blood oxygen saturation based on the above-mentioned amount of transmitted light. After a few minutes, as shown by the solid line in the figure, the body reaches an equilibrium state where the temperature has risen by about 2 to 3 degrees Celsius above the body temperature.
This temperature is monitored by the temperature display 14, and 5 minutes after the switch is turned on, a timer signal is output, and the comparator 13 detects that the detected temperature is 40°C, which is the reference temperature.
Start judging whether or not to exceed.

If, due to poor peripheral circulation, the temperature rises by about 4°C relative to the body temperature, as shown by the dotted line in the figure, the comparator 13 will detect that the detected temperature exceeds the reference temperature of 40°C. is detected, an abnormal temperature rise signal is output, and the indicator 15 is made to emit light. This makes it possible to take countermeasures such as moving the set position of the probe 9 or reducing the drive current. At this time, the peripheral circulation state can also be estimated by monitoring the detected temperature with the temperature display 14.

Further, as shown in FIG. 3, if the switch is turned on before the probe 9 is set, the thermistor 10 may detect a temperature higher than the reference temperature when the fingertip 8 is set, but the comparator 13 may detect a temperature higher than the reference temperature. Comparator 11 is not operating yet and finger tip 8 is set.
The measurement is started after the equilibrium condition has been reached by starting the timer 12.

In this embodiment, it is also possible to eliminate the comparator 11 and timer 12. in this case,
By turning on the fingertip 8 after setting it, it is possible to ensure proper measurement. Furthermore, if the comparator 11 is not provided and only the timer 12 that is started by the switch is provided, even if the switch is turned on before the fingertip 8 is attached, normal measurement is possible if the temperature reaches equilibrium within the time corresponding to the timer time. be. When only the comparator 11 is provided without the timer 12, false alarms are avoided at least before the normal measurement state in which the probe 9 is set on the fingertip 8.

FIG. 4 shows another embodiment of the present invention, in which the same reference numerals as in FIG. 1 indicate the same or equivalent parts.

In the figure, reference numeral 21 denotes an error signal generating means for comparing the temperature voltage signal detected by the thermistor 10 with a reference voltage corresponding to a reference temperature, for example, 39° C., which is unlikely to cause low-temperature burns, and outputting an error voltage. It is. Reference numeral 22 denotes drive current control means for reducing or increasing the drive currents of the light emitting elements 1 and 2 in response to this ± error voltage. Reference numeral 23 denotes a notification means for notifying that measurement is impossible when the drive currents of the light emitting elements 1 and 2, which are controlled in accordance with the temperature, reach a lower limit value effective for measurement. As a result, the temperature of the fingertip 8 is measured at a safe reference temperature set in advance, and if the peripheral circulation is poor and an abnormal temperature rise cannot be avoided even if the current is reduced within the allowable range, the alarm means 23
will be notified to that effect.

FIG. 5 shows yet another embodiment of the present invention, in which, in addition to the thermistor 10 shown in FIG. is added to the probe 39, and the temperature rise determination means 31 includes a temperature difference detection means 31a for detecting the temperature difference between the fingertip temperature detected by the thermistor 30 and the temperature detected by the thermistor 10, The temperature difference determining means 31b monitors whether or not the temperature difference exceeds a reference temperature difference, for example, 2.5° C., which corresponds to the upper limit temperature at which there is no possibility of causing low-temperature burns. As a result, the degree of peripheral circulation is monitored with high precision in accordance with the subject's body temperature, and the temperature difference display 32 displays the temperature rise from the body temperature.

Moreover, this temperature difference signal can be generated by making the reference signal of the error signal generating means 21 in FIG. 4 correspond to a safe reference temperature difference and using it as an input signal.
It can also be used for automatic control of drive current.

FIG. 6 shows still another embodiment of the present invention, in which the CPU calculates the temperature change gradient at which the temperature detected by the thermistor 10 approaches the temperature equilibrium state based on the timer signals successively generated from the timer. The equilibrium temperature prediction means 41 used, the rising temperature determination means 42 which outputs an abnormal temperature signal when the predicted equilibrium temperature exceeds a reference temperature corresponding to the possibility of causing low-temperature burns, and the temperature rise determination means 42 which outputs an abnormal temperature signal in response to the abnormal temperature signal. A notifying means 43 for notifying an abnormality follows the thermistor 10.

As shown by the solid line in FIG.
For the negative temperature change curve A when the finger tip is set to 1 or the positive temperature change curve B when the switch is turned on after the finger tip is set as shown by the solid line in FIG. It is determined whether or not the measured state is reached, and a temperature change curve that reaches an equilibrium state is predicted. As a result, the increased temperature determining means 42 quickly determines safety before equilibrium is reached. As mentioned above, it is possible to have the CPU determine whether it is a transient region under an actual measurement state or a transient region simply caused by a switch, but it is also possible to have the CPU determine whether it is a transient region under actual measurement conditions or simply due to a switch. It is also possible to make predictions after setting. It is also conceivable that the equilibrium temperature prediction means 41 is configured to detect from the temperature change curve the time point at which equilibrium is reached when the temperature change becomes almost zero, and start a determination operation instead of the timer.

As shown in FIG. 5, two thermistors 10,
30, in place of the equilibrium temperature prediction means 41, an equilibrium temperature difference prediction means is provided which calculates a temperature difference change curve in which the temperature difference detected by both temperature sensors approaches an equilibrium state. Then, if the estimated equilibrium temperature difference exceeds a reference temperature difference corresponding to the possibility of causing low-temperature burns, a rising temperature determining means is provided that outputs an abnormal temperature signal. Then, as shown in FIG. 7a together with the dotted line, there is a region C where the temperature rise difference approaches each other when the fingertip 8 is set after switching on, or as shown in FIG. 7b together with the dotted line. To,
In region D where both temperatures rise, the temperature difference in an equilibrium state is estimated, and this predicted value is compared in advance with the reference temperature difference. In this case, similarly, the temperature difference detected by both temperature sensors calculates the temperature difference change curve toward the temperature equilibrium state after the finger tip is set, detects the point when the temperature difference is balanced, and starts the temperature difference judgment operation. You can also do so.

[Effect of idea]

As described above, according to the present invention, according to claim 1, low-temperature burns can be caused by automatically warning an abnormal temperature rise caused by an abnormality in peripheral circulation, and adjusting the drive current or changing the set position. A fearless pulse oximeter becomes possible.
At this time, according to claim 2, the photoelectric probe is monitored in a normal measurement state where it is set at the measurement site. Further, according to claim 3, the measurement is performed after the timer time has elapsed after the device is powered on, and therefore, if the photoelectric probe is set to the measurement site sufficiently early within the timer time, measurement in an equilibrium state is possible. become. Alternatively, if the timer is started when both the device is powered on and the measurement site is set, measurements can be made more reliably in a temperature-balanced state.

According to claim 4, instead of a fixed timer time,
The measurement is started with a delay until just when the temperature sensor and the measurement site reach a temperature equilibrium state.

According to claim 5, a temperature rise based on the subject's body temperature is measured, making it possible to make highly accurate judgments.

According to claim 6, the driving current of the light emitting element is feedback-controlled so as to maintain a safe reference temperature, and low-temperature burns are automatically avoided. On this occasion,
According to claim 7, safe measurement is automatically performed in a state where the temperature rise is kept constant based on the subject's body temperature.

According to claim 8, by calculating the temperature change curve toward the equilibrium state, the equilibrium temperature is predicted in advance, and the possibility of low-temperature burns can be predicted. Similarly,
According to claim 9, the equilibrium temperature difference is predicted and the possibility of low-temperature burns is predicted.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a pulse oximeter according to an embodiment of the present invention, FIGS. 2 and 3 are diagrams explaining the operation of the same embodiment, and FIGS. 4 to 6 are diagrams showing other embodiments of the present invention. FIG. 7 is a diagram illustrating the operation of the embodiment according to FIGS. 5 and 6, respectively. 1, 2... Light emitting element, 3... Light receiving element, 9, 3
9...Probe, 10,30...Thermistor.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. In a pulse oximeter that measures the oxygen saturation level in blood from the amount of light transmitted through a measurement site that is set between a light emitting element and a light receiving element that face each other, A temperature sensor is placed near the light emitting element so as to be in contact with it, and the detected temperature detected by this temperature sensor is compared with a reference temperature corresponding to the possibility of causing low-temperature burns.When this reference temperature is reached, an abnormal temperature is detected. A pulse oximeter comprising: temperature rise determining means for outputting a signal; and reporting means for notifying an abnormality in response to the abnormal temperature signal. 2 Detecting that the amount of light incident on the light receiving element has been reduced due to the setting of the measurement area compared to when it is directly illuminated,
2. The pulse oximeter according to claim 1, further comprising light amount reduction detection means for starting the temperature rise determination means. 3. Claim 1, further comprising timer means for delaying the start of operation of the temperature rise determining means.
Or the pulse oximeter according to 2. 4. Calculate a temperature change curve in which the detected temperature detected by the temperature sensor moves toward the temperature equilibrium state after setting the measurement area so as to delay the start of operation of the rising temperature determination means until the detected temperature reaches an equilibrium state. The pulse oximeter according to claim 1 or 2, further comprising temperature equilibrium detection means for detecting the point at which the temperature has been reached. 5 In addition to the temperature sensor placed near the light emitting element so as to contact the measurement site, there is also a temperature sensor placed in the vicinity of the light emitting element so as to contact the measurement site at a position spaced apart from the light emitting element to the extent that a temperature increase due to heat generation of the light emitting element does not occur. The temperature increase determining means is configured to detect a temperature difference between the two temperature sensors and output an abnormal temperature signal when this temperature difference exceeds a reference temperature difference. The pulse oximeter according to claim 1, characterized in that: 6. In a pulse oximeter that measures oxygen saturation in the blood from the amount of light transmitted through a measurement site set between a light emitting element and a light receiving element facing each other, a pulse oximeter is placed near the light emitting element so as to make contact with the measurement site. a disposed temperature sensor; an error signal generating means for comparing the detected temperature detected by the temperature sensor with a reference temperature that is not likely to cause low-temperature burns and outputting an error signal; and in response to the error signal. A pulse oximeter comprising: drive current control means for increasing/decreasing the drive current of the light emitting element. 7 In addition to the temperature sensor placed near the light emitting element so as to contact the measurement site, there is also a temperature sensor placed in the vicinity of the light emitting element so as to contact the measurement site at a position spaced apart from the light emitting element to the extent that a temperature increase due to heat generation of the light emitting element does not occur. Further, the error signal generating means is configured to compare the temperature difference between the two temperature sensors with a reference temperature difference and output an error signal. The pulse oximeter according to claim 6. 8 Equipped with an equilibrium temperature prediction means for predicting an equilibrium temperature by calculating a temperature change curve in which the detected temperature moves toward a temperature equilibrium state after the measurement part is set, and having the temperature increase judgment means compare the predicted equilibrium temperature with a reference temperature. The pulse oximeter according to claim 1, characterized in that: 9 In addition to the temperature sensor placed near the light emitting element so as to come into contact with the measurement site, there is also a temperature sensor placed in the vicinity of the light emitting element so as to contact the measurement site at a position spaced apart from the light emitting element to the extent that a temperature increase due to heat generation of the light emitting element does not occur. Equilibrium temperature difference prediction, in which an equilibrium temperature difference is predicted by providing another temperature sensor arranged at the same time and calculating a temperature difference change curve in which the temperature difference detected by both temperature sensors moves toward a temperature equilibrium state after the measurement site is set. the temperature rise determining means compares the predicted equilibrium temperature difference with a reference temperature difference corresponding to the possibility of causing low-temperature burns, and outputs an abnormal temperature signal when the reference temperature difference is reached. The pulse oximeter according to claim 1, wherein the pulse oximeter is configured to: