JPH056962Y2 - - Google Patents

Description

[Detailed Description of the Invention] <<Industrial Application Field>> The present invention relates to a respiration sensor that detects the temperature difference between exhaled and inhaled air, and detects the presence or absence of respiration, the rate of respiration, the manner of respiration, etc.

<<Prior Art>> In post-operative respiratory management, neonatal life support, and the like, sensing respiration and monitoring its state by some means plays a most important role in terms of prompt response to the occurrence of any abnormality and, ultimately, in terms of the survival of the patient.

Conventional methods for sensing this breathing include methods that measure the impedance of the chest, methods that measure resistance changes due to expansion and contraction of electrical resistors attached to the chest strap, methods that detect the pressure of respiratory airflow, etc.
There are known devices that detect breathing sounds using a microphone, and devices that detect changes in humidity and temperature between exhaled and inhaled air. However, while these conventional means of detecting breathing are effective in measuring the presence or absence of breathing, respiratory waveforms, and in some cases respiratory flow rate, they are effective in measuring the presence or absence of breathing, respiratory waveforms, and, in some cases, respiratory flow rate. When providing breathing assistance to a patient with respiratory failure, the timing of assisting breathing, that is, the trigger for delivering air or oxygen when the patient wants to breathe, may be because the breathing is so weak that it cannot be detected. Alternatively, the influence of signals unrelated to breathing (body movement, electromagnetic interference, etc.) was large, resulting in frequent malfunctions.

Therefore, the present inventors installed a pyroelectric element in the respiratory airflow passage, used the pyroelectric element to detect a temperature change in the passage, and detected the temperature change from an electric circuit including the pyroelectric element. Invented a breathing sensor that is characterized by determining the timing of the start of exhalation and inhalation based on the differential waveform of an electrical signal corresponding to
It was disclosed in Publication No. 11133. By using an appropriate adapter, this breathing sensor using a pyroelectric element can sufficiently detect breathing in patients who breathe through an intubation tube such as a tracheal tube inserted into the nose, mouth, or trachea. However, in patients who have had a tracheostomy and are not fitted with a ventilator window, the respiratory airflow entrance and exit are wide open, making it difficult to effectively direct the respiratory airflow into the passageway of the pyroelectric respiration sensor. unable to lead,
It was not possible to accurately detect breathing.

《Problem that the invention aims to solve》 This invention can accurately detect breathing by attaching it to a patient who does not have a ventilator window after tracheostomy, where it has been difficult to detect breathing in the past. The purpose is to provide a breathing sensor.

《Means for solving the problem》 That is, the present invention basically consists of a sensor section that has at least a pyroelectric element, a field effect transistor, and a resistance element mounted on a circuit board, and a connector section for connecting to an electrical device. It is composed of
In the sensor section, the circuit system except the pyroelectric element is housed in a conductive outer tube, and the inner tube is filled with a sealing resin, and the sensor section and the connector section are connected through a tube. The tube is characterized by housing a cord consisting of a signal line and a power line connecting the sensor section and the connector section, and a ground wire connecting the sensor section, the outer tube, and the connector section. It is a breathing 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 exhalation and inspiration, and by applying a trigger at an appropriate voltage level, it is possible to accurately detect the beginning of exhalation and inspiration. Moreover,
Pyroelectric elements can provide much higher output than other temperature-sensitive elements such as thermistors and thermocouples, so they have the advantage of simplifying subsequent signal processing, such as not requiring amplification. In this way, the greatest advantage of using a pyroelectric element as a sensor is its high sensitivity and high output.Also, as mentioned above, its output is differential with respect to temperature, and it is different between expiration and inspiration. This is very advantageous in detecting the timing of switching.

The pyroelectric elements used in the breathing sensor of this invention include single crystals such as lithium tantalate (Li Ta O ₃ ), triglycine sulfate (TGS), lead titanate (Pb Ti O ₃ ), and lead zirconate titanate. Examples include, but are not limited to, sintered bodies such as (PZT), polymeric ferroelectric materials such as polyvinylidene fluoride (PVDF), and composites of ceramic sintered body powder and plastic materials. . However, since the rise in the output of the respiration sensor according to the present invention is controlled by the rate of change in temperature of the pyroelectric element, the response is better if the thickness is made as thin as possible in order to reduce the heat capacity. Able to grasp timing acutely. From this point of view, the limit for the thickness of single crystal and ceramic sintered bodies is 80 to 100 μm, and such thicknesses tend to break easily and are difficult to work with, such as when attaching to a support. On the other hand, filters or sheet-like materials made of single polymeric ferroelectric materials or composites of ceramic crystal powder and polymeric materials have good processability, and devices with a thickness of several tens of micrometers or less can be easily produced. It is suitable because it is easy to work with and has good workability.

FIG. 1 is a circuit diagram showing an example of an electrical circuit of a respiration sensor according to the present invention. The charge generated on the pyroelectric element 1 due to temperature change depends on the electric properties of the element such as capacitance, resistance, pyroelectricity, size, speed of temperature change, etc. Generally, its impedance is as high as 10 ⁸ to 10 ¹¹ Ω, and it cannot be detected as it is. Therefore, a recorder with a built-in buffer amplifier circuit for converting impedance is used, or a field effect transistor 2 is used to lower the impedance. The output impedance is determined by the output resistor 4, but it is usually desirable to set it to about 10 ³ to ^{10 5} Ω. The capacitor 5 is used to preferentially pass the high frequency component of the obtained signal, that is, the signal component at a time point when the rate of change is large, and the obtained waveform differs depending on the size of its capacitance. Therefore, the capacitance of the capacitor used can be determined depending on the purpose, and in some cases, the capacitor 5
Sometimes it is not used. In addition, between the gate of the field effect transistor 2 and the ground, the pyroelectric element 1 is connected in parallel.
It is also possible to stabilize the signal by inserting a gate resistor b of about 500 to 1000 MΩ.

On the other hand, when a pyroelectric element 1 is used in combination with a field effect transistor 2 and an output resistor 4 as shown in Fig. 1, the lead wire connecting each element acts as an antenna and noise from the outside is It is expected that this will interfere with the accurate detection of temperature changes. However, since the output of the pyroelectric element is large, by compactly combining the pyroelectric element 1, field effect transistor 2, output resistor 4, etc. into one component, the influence of external noise can be almost ignored. However, if the entire electrical circuit system consisting of the pyroelectric element 1, field effect transistor 2, output resistor 4, etc. is surrounded by a layer of conductive material to block electromagnetic waves from the outside (electromagnetic wave shielding). , you can be more careful.

In the respiratory sensor of the present invention, as shown in Fig. 2, the pyroelectric element 21 is exposed so that the respiratory airflow directly hits the pyroelectric element, so the electromagnetic wave shield protects the electric circuit system except for the pyroelectric element 21. Although it will be surrounded by a conductive material, it is better to shield the wiring from the pyroelectric element 21 as much as possible as shown in FIG. Mantle tube 2 that stores the parts to be shielded
The material of the outer tube 26 may be any material as long as it can make the outer tube 26 conductive, and is not particularly limited, but may include metals such as aluminum, copper, and iron, as well as conductive plastics or rubber. , plastic or rubber pipes coated with conductive paint can be used.

As shown in FIG. 2, the sensor unit in the present invention includes a pyroelectric element 21 attached to one end of a circuit board 23 on which an electric circuit is formed by a method such as printed wiring.
, and also a field effect transistor on the other side,
It is equipped with parts 22 such as resistive elements, and the circuit system part consisting of the parts 22 except for the pyroelectric element 21 is a hard vinyl chloride resin jacket tube coated with conductive paint to make it conductive. inserted into 26,
A sealing resin 29 such as an epoxy liquid resin is filled and sealed. At this time, the dimensions of the outer tube 26 should be such that the pyroelectric element 21 can be exposed as much as possible, and the conductor connected thereto can be hidden. By connecting the arm wires with the conductive coating of the mantle tube 26, the circuit system inside the mantle tube is shielded from electromagnetic waves and is not affected by external noise.

A cord 27 consisting of a signal line, a field effect transistor power supply line, and a ground line is connected to the jacket tube 26.
It is housed in a tube 25 that connects the ventilator and the connector 28, and is connected to an external electrical device such as an amplifier or the main body of the respirator through the cord 27 and the connector 28.

The respiration sensor according to the present invention can be applied to a wide range of medical devices that require sensing of respiration. Application examples include respiratory support devices, respiration monitors, apnea monitoring devices, anesthesia machines, incubators, oxygen administration system, ventilator, respirator, X
Radiography equipment (timing synchronization during chest X-ray photography),
Examples include rehabilitation exercise equipment for respiratory diseases, and synchronization of various treatment devices that stimulate the living body with breathing. The material, shape, size, and signal processing method of the pyroelectric element vary depending on its use.

To use it, fix it with tape or the like so that the pyroelectric element of the sensor part faces the incision of a patient who has undergone a tracheotomy and does not have a window for connecting to a ventilator. Because the pyroelectric element that serves as the sensor is exposed, it is able to detect breathing by sensitively reacting to the weak respiratory airflow that passes through the wide open tracheostomy.

《Effects of the invention》 According to the breathing sensor of the present invention, breathing can be detected well even in patients who have had a tracheostomy and do not have a ventilator window, which was extremely difficult to detect in the past. This is extremely useful in the medical industry because it enables respiratory assistance for these patients to be performed in synchronization with the patient's breathing.

[Brief explanation of the drawing]

Figure 1 shows one of the electrical circuits of the breathing sensor of the present invention.
FIG. 2 is a diagram showing the structure of a respiration sensor according to an embodiment of the present invention, in which (a) is a side sectional view and (b) is a plan view.

Claims (1)

[Scope of utility model registration request] It basically consists of a sensor section that has at least a pyroelectric element, a field effect transistor, and a resistance element mounted on a circuit board, and a connector section for connecting to an electrical device. The circuit system other than the circuit system is housed in a conductive mantle tube, and the mantle tube is filled with a sealing resin, and the sensor part and the connector part are connected through a tube, and the tube A respiration sensor characterized by housing a cord inside that consists of a signal line and a power line connecting the sensor part and the connector part, and a ground wire connecting the sensor part, the mantle tube, and the connector part.