KR102543402B1 - Hyperbaric oxygen chamber that prevents barotrauma - Google Patents

Abstract

Provided is a hyperbaric oxygen chamber including a probe mounted on a patient's ear, generating sound toward the patient's eardrum, and measuring the state of the eardrum from the level of sound reflected from the patient's eardrum. According to the present invention, medical accidents can be prevented by objectively evaluating the state of the eardrum. In addition, hyperbaric oxygen chamber treatment can be performed safely and with high efficiency.

Description

Hyperbaric oxygen chamber to prevent barotrauma {HYPERBARIC OXYGEN CHAMBER THAT PREVENTS BAROTRAUMA}

The present invention relates to a hyperbaric oxygen chamber. Specifically, the present invention relates to a hyperbaric oxygen chamber in which internal pressure is automatically controlled to prevent barotrauma.

Hyperbaric oxygen therapy uses a hyperbaric oxygen chamber to supply 100% oxygen to the patient at a pressure that is more than twice the atmospheric pressure. However, middle ear barotrauma may occur due to the pressure difference between the outer ear and the middle ear in a pressurized environment during hyperbaric oxygen therapy. When middle ear barotrauma occurs, light pain, congestion, and bleeding may occur depending on the severity, and in severe cases, the eardrum may rupture. In order to prevent middle ear barotrauma, the use of a nasal spray and a very slow pressure method were implemented. However, these methods cannot completely prevent middle ear barotrauma, and the biggest problem is that the medical personnel cannot help but judge the occurrence of middle ear barotrauma during treatment, depending on the subjective feeling of the patient through conversation with the patient. In addition, the existing automatic pressure control system of the hyperbaric oxygen chamber did not consider the patient's condition and controlled the pressure depending on the treatment table. Therefore, there is a need for a patient-specific treatment system capable of objectively determining whether middle ear barotrauma has occurred during treatment and changing the degree of pressurization according to the patient's condition.

Republic of Korea Patent No. 10-0561209 (registered on March 8, 2006)

A technical problem of the present invention is to automatically control the pressure of the hyperbaric oxygen chamber so that the patient does not experience a barotrauma phenomenon.

In order to solve the above problems, the present invention provides a hyperbaric oxygen chamber including a probe mounted on the patient's ear, generating sound toward the patient's eardrum, and measuring the state of the eardrum from the size of the sound reflected from the patient's eardrum. .

According to the present invention, medical accidents can be prevented by objectively evaluating the state of the eardrum.

According to the present invention, hyperbaric oxygen chamber treatment can be performed safely and with high efficiency.

1 is a schematic diagram showing a hyperbaric oxygen chamber according to the present invention.
2 is a diagram showing an automatic control system for a hyperbaric oxygen chamber according to the present invention.
3 is a view showing a state in which a probe according to the present invention is inserted into a patient's ear.
4 is a diagram showing a probe according to an embodiment of the present invention.
5 shows an MCU module according to the present invention.
6 shows a speaker driving circuit according to the present invention.
7 shows a microphone driving circuit according to the present invention.
8 shows an interface of an automatic pressure control program according to the present invention.
9 is a flowchart illustrating an automatic pressure control method according to the present invention.
10 is a flowchart illustrating an admittance calculation and middle ear pressure estimation algorithm.
11 is a flowchart illustrating a method of operating an MCU module.
12 is a graph showing admittance measurement results according to an embodiment of the present invention.
13 is a graph showing admittance measurement results according to another embodiment of the present invention.
14 is a graph showing a change pattern of admittance during Valsalva breathing.
15 is a graph showing a change pattern of admittance during saliva swallowing.

Terms used in this specification will be briefly described, and an embodiment of the present invention will be described in detail. The terms used in this specification have been selected from general terms that are currently widely used as much as possible while considering the functions in the present invention, but these may vary depending on the intention of a person skilled in the art, precedent, or the emergence of new technologies. In addition, in a specific case, there is also a term arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the invention. Therefore, the term used in this specification should be defined based on the meaning of the term and the overall content of the present invention, not simply the name of the term.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic diagram showing a hyperbaric oxygen chamber according to the present invention. A hyperbaric oxygen chamber according to the present invention includes a chamber, a probe, an MCU module, an air supply valve, an exhaust valve, and a controller.

The chamber is a configuration for a patient to enter and receive hyperbaric oxygen treatment. To this end, the chamber is formed of a closed container structure in which a space in which a patient can be located is formed, and an entrance may be provided. Preferably, the chamber may be provided in a cylindrical shape. Accordingly, pressure resistance performance to withstand a pressure difference between the outside and the inside of the chamber may be improved. In addition, at least one of a bed or a chair may be provided inside the chamber.

The probe is a component that generates sound and receives the reflected sound to measure the state of the eardrum. In detail, the probe is mounted on the patient's ear, generates sound toward the patient's eardrum, and receives the magnitude of the sound reflected from the patient's eardrum. The control unit, which will be described later, measures the state of the eardrum based on the received sound level. This will be described later in detail with reference to FIG. 2 .

The MCU module is a component that is electrically connected to the probe to control sound generated by the probe and receive sound reflected from the probe.

The control unit is configured to estimate the state of the eardrum based on the loudness of the sound input from the MCU module, and to generate a control signal for pressure inside the chamber accordingly. The control unit may be implemented using one or more general purpose computers or special purpose computers. A processing device may run an operating system (OS) and one or more software applications running on the operating system. A processing device may also access, store, manipulate, process, and generate data in response to execution of software.

The air supply valve is configured to open or block the air supply connected to the chamber according to the control signal. That is, when the air supply valve is opened, air flows into the chamber and the pressure inside the chamber rises.

The exhaust valve opens or closes an exhaust passage connected to the chamber according to the control signal. That is, when the exhaust valve is opened, the air inside the chamber is discharged to the outside, and the pressure inside the chamber decreases.

2 is a diagram showing an automatic control system for a hyperbaric oxygen chamber according to the present invention.

The automatic control system of the hyperbaric oxygen chamber is controlled by PID control as shown in FIG. When the treatment starts, the air supply and exhaust solenoid valves are opened, and the pressure value of the treatment table is presented as the SP of the PID controller. The pressure value inside the chamber is obtained through the pressure sensor, presented as the PV of the PID controller, and the MV value is obtained through PID operation to control the supply and exhaust proportion valves, thereby automatically controlling the chamber.

Barotrauma occurs due to a difference in pressure between the inside and outside of the cells of organs present in the body in the process of pressurizing the pressure during hyperbaric oxygen treatment using a hyperbaric oxygen chamber. Barotrauma is defined as a compound word of baros meaning pressure and trauma meaning damage. The barotrauma that occurs during hyperbaric oxygen therapy is external auditory canal barotrauma, middle ear barotrauma, inner ear barotrauma, sinus barotrauma, and lung barotrauma. Lung barotrauma) and tooth barotrauma (Teeth barotrauma) exist. Among them, the most frequent occurrence is middle ear trauma, which occurs when the pressure balance between the outer ear and the middle ear is not achieved. When middle ear barotrauma occurs, the patient may experience mild pain, hearing loss, bleeding, and in severe cases, eardrum rupture. Middle ear barotrauma can be prevented by opening the Eustachian Tube to equalize the pressure between the outer ear and the middle ear. Methods to achieve pressure equalization include Toynbee breathing, Valsalva breathing, and Frenzel. ) method, Lowry method, Edmonds Technique, swallowing, and yawning.

Conventional methods to prevent middle ear barotrauma that occur during hyperbaric oxygen therapy include the use of nasal spray and breathing techniques for pressure equalization. However, since the judgment of middle ear barotrauma during treatment depends on the conversation between the patient and the medical staff, the risk of middle ear barotrauma still exists even if appropriate precautions are taken. Therefore, there is a need for a method for objectively determining middle ear barotrauma rather than relying on the patient's feelings by directly monitoring the condition of the eardrum in real time during treatment.

Therefore, the present invention is characterized by objectively determining barotrauma through a probe. That is, the state of the eardrum is determined by measuring the admittance of the eardrum through the probe. Admittance is the reciprocal of impedance and indicates the degree to which current flows easily. The higher the value of admittance, the easier current flows. The unit is mho.

The probe is composed of a speaker capable of presenting test sounds to the eardrum and a microphone capable of receiving sound reflected from the eardrum. The speaker outputs a single sound at 226 Hz, and the single sound causes the air particles in the outer ear to vibrate. The eardrum resonates with the vibration to receive the sound, and the unabsorbed sound is reflected and input into the microphone. According to the pressure of the outer ear, the eardrum is bent in the direction of the outer ear and the middle ear. Depending on the degree of bending of the eardrum, the amount of sound absorbed and the amount of reflected sound change. The admittance of the eardrum according to the change in pressure can be measured using the obtained sound pressure and sound velocity.

3 is a view showing a state in which a probe according to the present invention is inserted into a patient's ear.

The probe according to the present invention is characterized in that it includes a speaker 222 and a microphone 223.

The speaker 222 receives an electrical signal for the test sound from the MCU module and converts it into sound to generate the test sound. In detail, the speaker is inserted into the external ear of the patient and is provided to generate sound toward the ear drum. The output frequency range of the speaker according to an embodiment of the present invention is 200 Hz to 5.5 kHz, which is a range capable of outputting 226 Hz generated by the developed system. The maximum output sound pressure is 127dB, and even output capability is guaranteed in all frequency bands.

The microphone 223 is a component that converts sound reflected from the eardrum into an electrical signal. In detail, the microphone is inserted into the outer ear of the patient, and the direction of the eardrum is the direction of sound pickup. Accordingly, the microphone converts the sound reflected from the eardrum into an electrical signal and transmits it to the MCU module. In one embodiment of the present invention, the input frequency range of the microphone is 20 Hz to 10 kHz, which is a frequency range sufficient to receive a single 226 Hz sound reflected through the eardrum.

In addition, the probe may be provided with a passage 224 for equalizing the pressure in the outer ear with the pressure inside the chamber. By moving air through the passage 224 into the chamber and into the outer ear, the pressure in the outer ear equalizes the pressure inside the chamber. Also, the chamber may be equipped with a pressure sensor. By measuring the pressure inside the chamber, the pressure in the outer ear can be determined.

4 is a diagram showing a probe according to an embodiment of the present invention. As a preferred embodiment, the probe may be provided in the form of a headset (head-set). In detail, the probe is provided in the form of a headset including a band 21 and an ear-pad 22, and the microphone and speaker protrude 221 from the surface of the headset in contact with the ear to the outside of the patient. can be inserted into it. Accordingly, since the probe is provided in a form familiar to patients, there is an effect of facilitating guidance on how to wear the probe.

5 shows an MCU module according to the present invention.

The MCU module can exchange signals through a probe and a 4-pole Aux cable. In detail, the inspection sound is transmitted to the speaker of the probe, and the sound reflected through the microphone is transmitted as an electrical signal. The acquired microphone signal is transmitted to the controller.

For the control and operation of the entire system, the control unit was configured using the STM32F103RCT6, which uses an ARM-Cortex M3 core, a 32-bit microprocessor. The control unit consists of an LED unit that informs the status of the system, a UART unit for communication with the control unit, and a sound unit for driving the speaker and microphone. In addition, a 4-pole earphone terminal, FC6818, was used for signal exchange with the speaker and microphone of the probe.

In case of driving the speaker, the speaker is controlled using the speaker driving circuit of FIG. 6 . The acoustic unit applies a sine wave signal having a frequency of 226 Hz and an amplitude of 0-2.5 V to the DAC input terminal of the speaker driving circuit using a digital to analog converter (DAC) of the MCU. At this time, the DAC resolution of STM32F103RCT6 is 12bit. Since a sine wave with an amplitude of 0 to 2.5V is a high voltage to drive a speaker, the voltage is reduced from 0 to 100mV by using the OPAMP voltage divider circuit. A sinusoidal signal with a lowered amplitude vibrates the condenser inside the speaker to generate sound pressure.

In case of driving the microphone, the microphone driving circuit of FIG. 7 is used. The space velocity input into the microphone is converted into a voltage and input to the microphone driving circuit. The amplitude of the microphone is 0-1.3V. At this time, the maximum amplitude of the 226Hz signal is 132mV. The input range of ADC (Analog to digital converter) pin of MCU is 0-3.3V and it is possible to perform ADC without any special amplification or filtering. After resetting to V, only the 226Hz signal is amplified by a factor of 25. The amplified signal is input to the ADC pin of the MCU and transmitted to the PC.

In order to acquire the admittance value of the eardrum from the MCU module and implement an automatic pressure control algorithm using the obtained value, a program based on the Windows program LabView2010 (National Instruments, USA) was directly developed and configured as shown in FIG. 8. The description of the program is as follows.

①: X-axis is time, Y-axis is pressure, and the actual pressure inside the chamber is displayed as a graph according to the treatment process.

② : Displays the actual pressure of the chamber and the Sep Point that the pressure of the chamber must reach by the PID algorithm.

③ : As a control unit, there are buttons for starting and ending treatment. Also, set the port for serial communication, enter the subject's name, measure the maximum and minimum values of the subject's eardrum admittance, and calculate and input the threshold value to be applied to the algorithm.

④ : The left and right middle ear pressure is estimated and displayed as a graph.

⑤ : Using the actual pressure inside the current chamber and the estimated middle ear pressure, the pressure difference between the outer and middle ear is calculated and displayed as a graph.

⑥ : The measured admittance of the eardrum is displayed as a graph in real time.

9 is a flowchart illustrating an automatic pressure control method according to the present invention, and FIG. 10 is a flowchart illustrating an admittance calculation and middle ear pressure estimation algorithm.

The automatic pressure control method (hereinafter referred to as process No. 1) operates at 1Hz depending on the speed of the PID controller, and the middle ear pressure estimation algorithm (hereinafter referred to as process No. 2) depends on the speed of transmitting data from the MCU module and operates at a rate of 7232Hz. It works. The two processes operate organically, and middle ear pressure is the estimated middle ear pressure, and chamber pressure is the actual pressure of the measured chamber, which is used as a global variable.

When treatment starts, process 1 issues a start command to the MCU module. The MCU module receiving the start command operates as shown in FIG. 11 . Process 2, which receives data from the MCU module, takes a fixed point digital IIR filter and stores it in an array. The designed digital filter is a 2nd order 226Hz peak filter, with a Q-factor of 50. When all components other than 226Hz are removed through digital filtering and the array of filtered data reaches 1024, the power of 226Hz is calculated by taking 1024 point FFT, and the admittance value of the eardrum is obtained using the power value. If the admittance value is higher than the threshold value set before the start of treatment, it is judged that the pressure is balanced, and the chamber pressure, the pressure value of the current chamber, is substituted for the variable middle ear pressure. If the acquired admittance value is lower than the Threshold value, it is judged that the pressure equilibrium has not been achieved and returns to the beginning of process 2 without any special action. After obtaining 1024 samples and calculating the first acoustic admittance, the signal acquired from the MCU module is overlapped by 25% and repeated until process 1 is completed.

The threshold value for determining the pressure balance is the value corresponding to 40% between the maximum and minimum values of the patient's eardrum admittance before treatment. This value was determined based on the following reasons through experiments in the algorithm development stage.

1. The condition of the eardrum does not recover 100% when pressure equalization methods such as needle insertion are performed because the pressure of the external environment continues to rise, and the admittance value does not rise to the maximum value, but only about 50 to 60% is recovered. this happened

2. If Valsalva breathing is performed while the eardrum is bent toward the middle ear due to external pressure, the pressure in the sinuses and middle ear is higher than the external pressure, and the eardrum may bend toward the outer ear. The data obtained by calculating the admittance of the eardrum through the process No. 2 is about 10 per second. Although the eardrum changes from the inside to the outside through Valsalva respiration, it changes in an instant, so the admittance value of the eardrum was measured to be about 40%. If the threshold is higher than 40%, the pressure balance is still maintained even though the pressure is equalized.

In the developed system, the pressure of the chamber is obtained through the pressure sensor in the treatment waiting process before starting treatment, and when the treatment starts and process 1 operates, the treatment waiting process ends. At this time, the pressure of the chamber measured is input as the initial value of SP and generally has a value of 1ata. Chamber Pressure, the current pressure of the chamber during treatment, is acquired through the pressure sensor and substituted into the variable PV for use in the PID controller. DP (Difference Pressure), the pressure difference between the outer ear and the middle ear, can be calculated using the PV, which is the current pressure, and the middle ear pressure estimated through the second process operation. Hold Flag becomes true when the value of DP exceeds 0.04, and it means that the pressure is maintained by not changing SP, and the initial value is false. If the Hold Flag is false, pressurization is in progress, so the DP value is compared with 0.04 to determine whether to maintain or pressurize the pressure. If DP, the pressure difference between the outer ear and the middle ear, already exceeds 0.04 and the Hold Flag is true, the DP value is compared with 0.02, and if it is less than 0.02, it is determined that the pressure imbalance is resolved, the Hold Flag becomes false, and the existing SP value is 0.002. Increase the pressure by substituting the increased value by

By calculating the SP and PV determined according to the previous calculation result through the PID controller, the MV is obtained and output to control the proportional control valve to adjust the pressure in the chamber.

When PV, the actual pressure of the chamber, exceeds the desired pressure that must be reached for treatment, it is determined that pressurization is completed, a stop command is issued to the MCU module, and the algorithm is terminated. The algorithm is applied to the right ear and the left ear, respectively, and the algorithm is applied even if pressure equalization of one ear is not performed.

After the patient was positioned inside the chamber, admittance was measured while adjusting the pressure of the chamber. The hyperbaric oxygen chamber automatically operates so that the pressure rises at a rate of 0.002 ata/sec. At this time, the patient voluntarily performs pressure equalization continuously. When the pressure in the chamber reaches 1.1 ata, actions that can achieve pressure equilibrium are prohibited and instructions are given to maintain the pressure equilibrium state. By maintaining the pressure equilibrium state, when the pressure difference between the middle ear and the outer ear reaches 0.04 ata or more, after confirming that the pressure in the chamber is maintained, pressure equalization is instructed. When the chamber pressure reaches 1.2 ata, the above process is repeated, and when it reaches 1.3 ata, the measurement ends and returns to atmospheric pressure.

12 is a graph showing admittance measurement results according to an embodiment of the present invention. 12a is the pressure inside the chamber, b of FIG. 12 is the pressure difference of the right ear, c of FIG. 12 is the admittance of the right ear, d of FIG. 12 is the pressure difference of the left ear, and e of FIG. 12 is the admittance of the left ear. indicate The horizontal axis of each graph represents time. In this example, the patient performed the Valsalva breathing method.

From the point where the pressure imbalance begins, pressurization continues until the pressure difference between the outer ear and the middle ear reaches 0.04 ata, and it can be observed that the pressure is maintained when the pressure difference between the outer ear and the middle ear reaches 0.04 ata.

13 is a graph showing admittance measurement results according to another embodiment of the present invention. 13, a is the pressure inside the chamber, b in FIG. 13 is the pressure difference in the right ear, c in FIG. 13 is the admittance in the right ear, d in FIG. 13 is the pressure difference in the left ear, and e in FIG. 13 is the admittance in the left ear. indicate The horizontal axis of each graph represents time. In this example, the patient performed saliva swallowing.

From the point where the pressure imbalance begins, pressurization continues until the pressure difference between the outer ear and the middle ear reaches 0.04 ata, and it can be observed that the pressure is maintained when the pressure difference between the outer ear and the middle ear reaches 0.04 ata.

14 is a graph showing a change pattern of admittance during Valsalva breathing.

When pressure equalization is performed using the Valsalva technique, air from the lungs supplies air to the sinuses and eustachian tubes. The eardrum, which had been bent in the direction of the middle ear by external pressure due to air flowing into the ear tube, is bent in the direction of the outer ear. At this time, the eardrum goes through a 100% recovery state and bends in the direction of the outer ear, but the admittance value does not rise to the maximum. This is considered to be due to data loss caused by the change in the eardrum being faster than the speed obtained by calculating data because only 25% overlap is used in the process of calculating admittance. However, through the algorithm, the momentary rising part can be determined as the pressure equilibrium point, and the pressurized state is maintained. Immediately after performing the Valsalva breathing method, the admittance value of the eardrum is minimal. Since the curved direction of the eardrum cannot be determined using only the admittance value of the eardrum, the system determines that the eardrum is in a pressure imbalance state. However, since the pressure equilibrium was achieved immediately before, the pressure in the chamber continues to rise, so that the eardrum bent in the direction of the outer ear slowly bends in the direction of the inner ear again, showing a pattern as shown in FIG. 14 . The pressure in the chamber increases by 0.002 ata per second, and since it takes less than 10 seconds from immediately after Valsalva respiration to the judgment of the next pressure equilibrium, the estimated pressure difference between the outer ear and the middle ear is less than 0.04 ata.

15 is a graph showing a change pattern of admittance during saliva swallowing.

When saliva swallowing is performed, the eustachian tube is opened for a short time due to instantaneous muscle movement, and external air is introduced into the middle ear space. Unlike Valsalva breathing, which forcefully pushes air into the middle ear space through the eustachian tube, saliva swallowing allows outside air to flow naturally while the eustachian tube is momentarily opened, so the eardrum does not recover 100%, and depending on the person, about 50-60% of the recovery occurs. show a recovery rate. When the admittance of a subject who actually performed saliva swallowing was measured, the maximum value of the admittance value had a higher value. However, by setting the threshold of the algorithm to 40% of the maximum and minimum values of admittance as shown in Equation 1 below, it can be determined as the point of force equilibrium.

[Equation 1]

If the Threshold value is set to 40% of the maximum and minimum values of the admittance, the point at which the algorithm determines that the pressure is equal is already the actual pressure difference between the outer ear and the middle ear, depending on the person, about 0.005ata ~ 0.015ata. However, in the algorithm, the pressure difference at that point is estimated as 0 ata, and the pressure is maintained when 0.04 ata increases from that point. At this time, the actual pressure difference between the outer ear and the middle ear can be predicted as 0.045 to 0.055 ata, and the pressure difference at which the initial symptoms of middle ear barotrauma occur is 0.08 ata, so the safety of the algorithm is secured.

The preferred embodiments of the present invention described above have been disclosed for illustrative purposes, and those skilled in the art with ordinary knowledge of the present invention will be able to make various modifications, changes and additions within the spirit and scope of the present invention, and such modifications, changes and additions will be considered to fall within the scope of the above claims.

Those skilled in the art to which the present invention pertains can make various substitutions, modifications, and changes without departing from the technical spirit of the present invention. is not limited by

10: chamber
20: probe 30: MCU module
40: control unit
50: air supply valve 60: exhaust valve
222: speaker 223: microphone

Claims (6)

In the hyperbaric oxygen chamber for preventing barotrauma,
a probe mounted on the patient's ear, generating sound toward the patient's eardrum, and measuring the magnitude of sound reflected from the patient's eardrum;
an MCU module electrically connected to the probe to control a sound generating operation generated by the probe and receiving sound reflected from the probe;
a control unit for estimating the state of the eardrum based on the volume of sound received from the MCU module and generating a control signal for pressure inside the chamber;
an air supply valve opening or blocking an air supply passage connected to the chamber according to the control signal; and
An exhaust valve that opens or blocks an exhaust path connected to the chamber according to the control signal,
The probe is
a microphone inserted into the patient's outer ear and directed toward the eardrum as a sound pickup direction; and
It includes; a speaker inserted into the outer ear of the patient and generating sound toward the eardrum;
The control unit estimates the state of the eardrum by measuring admittance based on the energy level of the sound generated by the speaker and the energy level of the sound reflected from the eardrum and received by the microphone;
Estimating a difference between the middle ear pressure and the internal pressure of the chamber based on the estimated state of the eardrum;
The point where the difference value is minimum is determined as a pressure equilibrium state,
The output frequency range of the speaker is 200 Hz to 5.5 kHz,
The input frequency range of the microphone is 20 Hz to 10 kHz,
The probe is
It is provided in the form of a headset (head-set) and worn on the patient's ear,
The microphone and speaker protrude from the surface of the headset in contact with the ear and are inserted into the outer ear of the patient,
The control unit,
Sending an open control signal to the air supply valve when the pressure equilibrium is reached;
Sending a cut-off control signal to the air supply valve when the estimated difference value reaches 0.04 ata;
The control unit,
A value that is a predetermined ratio to the difference between the maximum and minimum values of the measured admittance is determined as a threshold value;
The time point at which the threshold value appears is determined as a pressure equilibrium state,
The high-pressure oxygen chamber, characterized in that the predetermined ratio is 40%. delete delete delete delete delete

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