JPH0212115B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to respiratory tuning of an open breathing system used for inhaling oxygen gas to patients with chronic respiratory diseases.

[Prior art]

Methods of inhaling gases such as oxygen to patients include
There are two main types: closed type and open type. The closed type is a method used for anesthesia, etc., and the oxygen gas supply circuit is cut off from the outside air, and it is easy to synchronize breathing by changing the internal pressure of this circuit, and this has already been done. On the other hand, the open type is inhaled by patients with chronic respiratory diseases who attach the end of the oxygen supply tube to their nasal cavity or oral cavity for a long period of time, and usually oxygen gas is continuously supplied regardless of breathing movements. be done. Therefore, since gas is delivered even when exhaling, the patient feels resistance to breathing, and oxygen gas is not utilized during exhalation and is wasted.

Therefore, a research group at Tottori University School of Medicine has developed a breathing-synchronized gas supply device that has a control function that can supply oxygen and other gases in accordance with breathing, but it detects breathing patterns using a temperature sensor such as a thermistor. In order to perform this, it was necessary to perform analysis using a microcomputer, etc., and the responsiveness to breathing was not fully satisfactory.

[Purpose of the invention]

In view of the current state of respiratory synchronization in the respiratory system, and as a result of various studies on respiratory sensors, the present invention has been developed to detect the onset of inhalation and exhalation by using a pyroelectric respiration sensor using a pyroelectric element as a respiration sensor. The purpose of this project is to use this technology to provide a breathing synchronized oxygen supply device that does not require the complicated analysis using a microcomputer that was previously required, and that does not have synchronization lag. It is.

[Structure of the invention]

That is, the present invention basically consists of a nasal cannula part equipped with a respiratory sensor including at least a pyroelectric element, a solenoid valve, and a solenoid valve opening/closing circuit, and the temperature change rate of the respiratory airflow from the respiratory sensor is proportional to the temperature change rate of the respiratory airflow. This breathing-synchronized oxygen supply device is characterized in that a solenoid valve is opened and closed via the solenoid valve opening/closing circuit according to an output voltage signal, and the supply of oxygen gas is controlled in synchronization with expiration and inspiration.

The most significant feature of the present invention is the use of a pyroelectric element in the respiratory synchronization sensor. In a pyroelectric element, when a temperature change occurs, the spontaneous polarization value of the ferroelectric element changes, and the surface charge of the element changes. At this time, when an external load is connected, a current (pyrocurrent) flows, and the surface returns to its original state with neither excess nor deficiency, and no current flows until the temperature changes again. Therefore, the pyroelectric element responds only when there is a temperature change, and when used as a respiration sensor, a differential waveform of the respiration waveform can be obtained. Therefore, this waveform has a sharp peak at the beginning of expiration and inspiration, and the simplest method of applying a trigger at an appropriate voltage level is to
The start of exhalation and inspiration can be accurately detected.
Furthermore, the pyroelectric element can provide a much higher output than other temperature sensing elements such as thermistors and thermocouples, and subsequent signal processing is also very easy.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The respiratory synchronized oxygen supply apparatus of the present invention will be explained below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. The main body 1 includes at least an oxygen intake port 2, an oxygen supply port 3, a solenoid valve 4, and a solenoid valve opening/closing circuit 5. An oxygen concentrator, oxygen cylinder, etc. may be connected to the oxygen intake port 2, and the solenoid valve opening/closing circuit 5 may be connected to the oxygen intake port 2. The electromagnetic valve 4 is operated by a signal from the circuit 5 to synchronize the patient's exhalation and inhalation, that is, oxygen is sent out from the oxygen supply port 3 only when the patient is inhaling oxygen.

The electromagnetic valve opening/closing circuit 5 receives the signal from the pyroelectric sensor 7.
Two types of triggers are applied to the output voltage signal proportional to the temperature change rate of the respiratory airflow, one for inspiration and one for expiration, and when the signal from the pyroelectric sensor 7 exceeds the trigger level for inspiration, the solenoid valve is opened and vice versa. This is a solenoid valve operating circuit that closes the solenoid valve when the exhalation trigger level is exceeded.

An oxygen intake port 2 and an oxygen supply port 3 are attached to the main body panel, and a nasal cannula 6 is connected to the oxygen supply port 3. The nasal cannula 6 has a structure in which oxygen flows through it, branches into two directions in the middle, and guides the oxygen to two nostrils, and is widely used for oxygen inhalation by patients with relatively mild symptoms. There is. In the embodiment shown in FIG. 1, a pyroelectric sensor 7 consisting of several electrical components such as a pyroelectric element and a field effect transistor is installed near the conduit 8 inserted into the nostril of the nasal cannula 6. The output voltage signal is sent to the electromagnetic valve opening/closing circuit 5 through a cord 9. Therefore, the cord 9 should be attached to the nasal cannula 6 so that it does not get in the way, or
Alternatively, it is preferable to mold the tube of the nasal cannula into an 8-shaped tube and wire a cord inside one of the tubes. The cannula 6 itself is also not heavy, which is more preferable. In this embodiment, the nasal cannula 6 is directly connected to the oxygen supply port 3 of the main body 1, but of course a humidifier may also be inserted and installed in the middle.

The pyroelectric elements used in the pyroelectric sensor of the present invention include single crystals such as lithium tantalate (LiTaO ₃ ), triglycine sulfate (TGS), lead titanate (PbTiO ₃ ), and lead zirconate titanate (PZT). ), polymeric ferroelectric materials such as polyvinylidene fluoride (PVDF), and composites of ceramic sintered powder and plastic materials, but are not limited to these.

The biggest advantage of using a pyroelectric element as a sensor is its high sensitivity and high output. for example,
The output of chromel-allomel thermocouple is 0.04mV/℃
On the other hand, in the case of a pyroelectric element, it varies depending on the type and size, but for example, it is 1.3mV/
A very high output of °C·sec can be obtained, and this fact greatly simplifies subsequent signal processing. Furthermore, as mentioned above, the output is differential with respect to temperature, which is very advantageous in detecting the timing of switching between exhalation and inspiration.

Since the rise in the output of the pyroelectric sensor of the present invention is governed by the rate of change in the temperature of the pyroelectric element,
If the thickness is made as thin as possible in order to reduce the heat capacity, the response will be better and the timing of breathing can be more sensitively detected. Figure 2a shows a respiration waveform generated by a thermistor.As shown in the figure, the waveform is close to a sine curve, and the beginnings of exhalation and inspiration are not clear. On the other hand, in the respiratory waveform obtained by the pyroelectric sensor as shown in Figure 2b, very sharp peaks appear on the positive and negative sides at the beginning of expiration and inspiration, respectively, so this signal has different characteristics. All you have to do is apply the trigger to open and close the solenoid valve.

〔Effect of the invention〕

By using the oxygen supply device of the present invention, in an open breathing system, it is possible to accurately detect the start of a patient's inhalation and exhalation, and to send oxygen gas in synchronization with this, and it also has excellent responsiveness to breathing. This system does not give the patient a feeling of respiratory resistance, has a simple structure that does not require complex waveform analysis or calculation systems, is inexpensive, has few failures, and is able to reduce the amount of oxygen required. The present invention has the advantage of being less than 1/2 that of the non-tuned type, and the present invention is a very effective system in the medical industry from the perspective of resource saving.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a breathing synchronized oxygen supply apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing respiratory waveforms, where a is a respiratory waveform produced by a conventional thermistor, and b is a respiratory waveform produced by the apparatus of the present invention using a pyroelectric element.

Claims (1)

[Scope of Claims] 1. Basically consists of a nasal cannula section equipped with a respiratory sensor including at least a pyroelectric element, an electromagnetic valve, and an electromagnetic valve opening/closing circuit, and is configured to control the temperature change rate of the respiratory airflow from the respiratory sensor. A respiration synchronized oxygen supply device characterized in that a proportional output voltage signal opens and closes a solenoid valve via the solenoid valve opening/closing circuit to control the supply of oxygen gas in synchronization with exhalation and inspiration. 2. The respiratory synchronized oxygen supply device according to claim 1, wherein the means for transmitting the output voltage signal from the respiratory sensor to the electromagnetic valve opening/closing circuit is radio wave transmission using a telemeter.