JPH0137949B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a respiratory monitoring device.

Conventionally, most devices of this type have detected respiration using the thoracic impedance induction method because it is easy to use both the ECG detection electrode and the respiration detection electrode. In addition, there was also a method using the pine stress method, which detects respiration by detecting changes in the body caused by respiratory movements, similar to the thoracic impedance induction method.

However, the former method does not directly detect exhalation or inhalation, but detects respiration by detecting the respiratory movement during respiration, that is, changes in the diaphragm as impedance changes through the body surface.
For this reason, it is difficult to simultaneously detect various body movements of the patient and detect breathing when the patient is moving, and when there is only respiratory movement in the case of airway obstruction, that is, there is no actual ventilation, only the detected movement is difficult. It has the disadvantage that it detects even when you are breathing, and detects your breathing.

On the other hand, since the latter detects the same content as the former, it also has the same drawbacks.

By the way, in Japanese Patent Publication No. 53-18839, a temperature detection element is attached to the patient's airway system to detect temperature changes during respiratory ventilation in combination with the impedance induction method.
This shows a device for measuring absolute ventilation.

However, attaching the temperature detection element to the nose and mouth places an excessive burden on the patient and has the disadvantage that operation becomes unstable when the ambient temperature is high.

Therefore, the inventor of the present invention has proposed that by making it possible to perform respiratory monitoring by switching between the impedance induction method and the ventilation temperature detection method depending on the situation, the shortcomings of each method can be compensated for by appropriate selection. Since the chest current can also be used for electrocardiograph (ECG), we thought it would be more convenient in practice. But 2
If a system detection circuit section is provided to monitor respiration, the circuit configuration will be complicated and the cost will be high.

An object of the present invention is to enable switching between two systems of respiratory monitors with a simple configuration.

The respiratory monitoring device of the present invention includes a pair of electrodes 4 for detecting thoracic impedance, and a two-terminal respiratory ventilation detector 7 consisting of an element such as a thermistor whose resistance value changes depending on the change in air temperature during respiratory ventilation, and a switching circuit. 3, the pair of electrodes 4 and the respiratory ventilation detector 7 can be switched and connected to the detection circuit.

Between the pair of electrodes 4 or 2 of the respiratory ventilation detector 7
It is equipped with a detection circuit that sends a current between the terminals and extracts impedance changes during breathing as a signal, and uses the output to detect breathing.

The detection impedance change rate of the detection circuit when the switching circuit 3 is switched to the respiratory ventilation detector 7, and the detection impedance change rate of the detection circuit when the switching circuit 3 is switched and connected to the pair of electrodes 4. The impedance of the respiratory ventilation detector 7 is corrected so that the values are approximately the same.

With this configuration, it becomes possible to perform respiratory monitoring by switching between the thoracic impedance method and the respiratory ventilation temperature detection method with a simple circuit.

Next, an embodiment of the respiratory monitoring device of the present invention will be described with reference to the drawings.

FIG. 1 is an overall block circuit diagram, and FIG. 2 is a waveform diagram for explaining the block circuit of FIG. 1.

First, we will discuss the case of detecting respiration using the thoracic impedance induction method.

An oscillation output as shown in FIG. 2 from an oscillation circuit 1 having an oscillation frequency of 50 KHz, for example 50 KHz, is given to a constant current circuit 2. In this constant current circuit 2, a pair of chest electrodes 4, which are respiratory detection electrodes, are attached to the chest of a patient to be measured during respiratory monitoring, as shown in FIG.
During this period, constant current control is performed so that the oscillation output flows as a constant weak current signal of 100 μA or less. In the case of respiration detection using the thoracic impedance induction method, this constant current signal is applied to the pair of thoracic electrodes 4 via the switching circuit 3 connected to the a side. This signal then flows between the pair of chest electrodes 4 through the patient.

However, it is assumed that the patient is performing breathing exercises. Due to changes in the diaphragm due to this breathing movement, the impedance between the pair of chest electrodes 4
Zk changes as shown in FIG. Therefore, due to the change in impedance Zk, the signal is modulated in amplitude as shown in FIG. 2 in conjunction with the constant current control by the constant current circuit 2.

On the other hand, this amplitude-modulated signal between the constant current circuit 2 and the switching circuit 3 is given to the amplifier circuit 5 having a high input impedance. Then, it is widened. This amplified signal is applied to the rectifier circuit 6, where it is detected and becomes a waveform signal as shown in FIG.

This waveform signal corresponds to a change in impedance Zk due to breathing between a pair of chest electrodes 4 installed on the patient's chest, or more precisely, due to a change in the diaphragm based on breathing movement. Even with this, respiration detection can be performed using the thoracic impedance induction method.

Next, a case will be described in which respiration is detected by direct detection of respiratory ventilation. Note that explanations of duplicate parts will be omitted.

When detecting respiration using the thoracic impedance induction method, the switching circuit 3 connected to the a side is
In the case of direct detection of respiratory ventilation, it is connected to the b side. As a result, the oscillation circuit 1 outputs the oscillation,
The signal that becomes a constant weak current due to the constant current circuit 2 is
It is applied to a respiratory ventilation detector 7 that directly detects respiratory ventilation. The respiratory ventilation detector 7 is composed of an element, such as a thermistor, whose resistance value changes based on changes in air temperature during respiratory ventilation. Then, it is fixedly attached near the patient's respiratory ventilation to be measured during respiratory monitoring, for example, near the nose and mouth as shown in FIG. As a result, the thermistor and the like are exposed to changes in air temperature due to warm air discharged from the patient's body during breathing and cold air sucked in from outside the patient's body during breathing, and the resistance value Zk' changes. The signal thus becomes amplitude modulated as in the case with thoracic impedance induction. This signal is then amplified and detected.

Note that the resistor R is provided so that the change in resistance value Zk' during respiration monitoring using the thermistor etc. described above has the same rate of change as the change in impedance Zk during respiration monitoring using the thoracic impedance induction method. It is.

In this embodiment, an oscillation circuit 1, a constant current circuit 2, an amplification circuit 5, and a rectification circuit 6 constitute a detection circuit section for detecting respiration by the thoracic impedance induction method.

In summary, the respiratory monitoring device of the present invention is characterized in that a respiratory ventilation detector consisting of an element whose resistance value changes based on changes in air temperature during respiratory ventilation can be connected to the detection circuit section based on the thoracic impedance induction method. It is.

Thereby, depending on the purpose, respiration detection using the thoracic impedance induction method and respiration detection using the respiratory ventilation detector can be performed without changing the apparatus, and moreover, with an economical configuration that uses the same detection circuit section.

In addition, respiration detection using a respiratory ventilation detector directly monitors the detection of actual expiration and inhalation, so it can detect apnea due to airway obstruction, which cannot be detected with the thoracic impedance induction method, and is reliable. The quality is extremely high. Therefore, according to the present invention, it is possible to switch and use two respiratory monitoring methods depending on the situation, so the shortcomings of each method can be compensated for by appropriate selection, and the chest electrode can also be used for electrocardiography. This is extremely convenient in practice.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram of one embodiment of the respiratory monitoring device of the present invention, FIG. 2 is a waveform diagram for explaining the block circuit of FIG. 1, and FIG. 3 is a chest electrode based on the chest impedance induction method, and FIG. 6 is a diagram illustrating how to attach a respiratory ventilation detector for direct respiratory ventilation detection. In addition, among the symbols used in the figure, 1...
...Oscillation circuit, 2... Constant current circuit, 3... Switching circuit, 4... Electrode, 5... Amplifying circuit, 6... Rectifying circuit, 7... Respiratory ventilation detector, R... Resistor.

Claims (1)

[Claims] 1. A two-terminal respiratory ventilation detector comprising a pair of electrodes for detecting thoracic impedance, an element whose resistance value changes with changes in air temperature during respiratory ventilation, and the pair of electrodes and the respiratory ventilation detector. and a detection circuit that flows a current between the pair of electrodes or between the two terminals of the respiratory ventilation detector and extracts the change in impedance during breathing as a signal, The detection impedance change rate of the detection circuit when switching to the respiratory ventilation detector is approximately the same as the detection impedance change rate of the detection circuit when the switching circuit is switched and connected to the pair of electrodes. , A respiratory monitoring device characterized in that the impedance of the respiratory ventilation detector is corrected.