KR102270546B1 - System for detecting apnea - Google Patents

Abstract

The present invention relates to a system for detecting apnea in real time, so that accurate apnea detection is possible by detecting an apnea signal that may occur during normal activity or sleep of a user or a measurement object from a radio signal reflected by a user or a measurement object. It is about a system that is configured.

Description

Apnea detection system {SYSTEM FOR DETECTING APNEA}

The present invention relates to a system for detecting apnea in real time, so that accurate apnea detection is possible by detecting an apnea signal that may occur during normal activity or sleep of a user or a measurement object from a radio signal reflected by a user or a measurement object. It is about a system that is configured.

Apnea may have various meanings, but in general, it refers to a phenomenon in which breathing is temporarily stopped during normal activities or sleep. In particular, sleep apnea, a phenomenon in which breathing is temporarily stopped during sleep, is a sudden It may cause fatal accidents.

This is because, when oxygen is not supplied to the body due to sleep apnea, the oxygen saturation (the degree to which the blood contains some amount of oxygen) in the body's blood becomes abnormally low.

Nocturnal sleep fragmentation due to sleep apnea causes excessive daytime sleepiness (EDS) and reduces arterial oxygen saturation (O2 saturation).

A decrease in oxygen saturation not only causes high blood pressure, arrhythmia, etc., but can even lead to serious consequences such as heart attack and sudden death during sleep.

Death due to sleep apnea occurs mostly in infants and is called SIDS (Sudden Infant Death Syndrome).

In addition, deaths due to sleep apnea frequently occur in unconscious patients or the elderly.

The sleep apnea may be classified into three patterns: central apnea, obstructive apnea, and mixed apnea.

Central apnea is defined as a neurological disorder that cessation of all respiratory effort during sleep and is predominantly seen in newborns and infants.

Obstructive apnea is characterized by repeated cessation of breathing during sleep due to obstruction or collapse of the upper airway, thereby reducing oxygen saturation in arterial blood.

Mixed apnea means that the two types of apnea described above occur simultaneously.

Clinically, if the symptoms of not breathing for more than 10 seconds during night sleep appear 5 or more times per hour or 30 or more times during 7 hours of sleep, it can be classified as sleep apnea syndrome.

In general, snoring is a sound produced by shaking of the soft palate of the upper airway and can be a strong predictor for suspecting sleep apnea syndrome.

Sleep apnea testing is usually done through polysomnography. The polysomnography test objectively evaluates the structure and function of sleep and events that occurred during sleep. During 8 hours of sleep, EEG, eye movements, mandibular electromyography, leg electromyography, electrocardiogram, snoring, blood pressure, breathing exercise, and oxygen in arterial blood. It is to comprehensively measure saturation, etc., and at the same time record the patient's behavioral abnormalities during sleep by video.

This record is read by sleep test technicians and sleep medicine specialists to determine how severe snoring is, whether an arrhythmia occurs, whether blood pressure rises, whether other problems occur during sleep, and what differences from normal people's sleep are. comprehensive results are obtained.

As a prior art related to sleep apnea diagnosis, the "Integrated sleep apnea screening system" of US Patent No. 6,368,287 is a device that allows ordinary people to easily measure respiration at home without the help of a clinician or expert, and is attached to the nostril area. Disclosed is a system for diagnosing sleep apnea by using a temperature change caused by respiration in the process of inhalation and exhalation using a temperature sensor. This technology displays whether the sensor is accurately positioned on the measurement site with a light emitting diode (LED). However, since measuring respiration using a temperature sensor attached around the nose cannot be used for diagnosing central apnea, there is a problem in that respiration cannot be measured only by temperature change due to nasal winds in actual clinical practice.

"Microprocessor system for the simplified diagnosis of sleep apnea" of US Patent No. 6,342,039 is a system for diagnosing sleep apnea by using the phenomenon that oxygen saturation is lowered by apnea and the oxygen saturation returns to normal when breathing normally. is starting This technique diagnoses the occurrence of apnea by measuring and graphing oxygen saturation continuously and measuring the gradient of oxygen saturation that changes when sleep apnea occurs.

In addition, "Method and apparatus for analyzing heart and respitory frequencies photo-plethysmographically" of US Patent No. 5,396,893 is a method of diagnosing apnea by analyzing photo-plethysmographically according to frequency bands and extracting frequency components corresponding to respiration. By measuring the respiration of a normal person, a very accurate prediction is possible. However, there is a problem in diagnosing that respiration has occurred even when respiration does not occur due to a ringing phenomenon of the filter in the process of extracting respiration components.

That is, in the conventional sleep apnea detection method, by attaching a certain sensor to a measurement target or adopting an algorithm with low accuracy to detect respiration/apnea, an apnea alarm was frequently issued even during normal breathing.

Under the above technical background, the present invention accurately recognizes and measures an irregular respiration signal (ie, a respiration signal that is not similar to a Sin or Cos waveform) of a user or a measurement target as a respiration signal, as well as a change to abnormal respiration during normal respiration. An object of the present invention is to provide a system and method for accurately detecting whether an entry is made.

In addition, the present invention accurately measures the respiration signal of the user or the measurement object even under a noise environment in which the user or measurement object is located in a remote location or there is a dynamic object indicating movement around the user or measurement object, and from this, abnormal during normal breathing An object of the present invention is to provide a system and method for accurately detecting whether or not entering into respiration.

In addition, the present invention accurately distinguishes between abnormal respiration according to the movement of a user or a measurement target and apnea during sleep, and at the same time reflects the characteristics of apnea symptoms that may appear after normal respiration is observed to accurately detect sleep apnea. It aims to provide a system and method.

An apnea detection system according to an aspect of the present invention comprises a transmitter for transmitting a radio signal to a detection area, and a receiver for receiving a radio signal reflected by a measurement target within the detection area. The optimal respiration position determining unit for determining the optimal respiration position of the target, the time axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f ₂ ) of the measurement target from the radio signal reflected from the optimum respiration position, and , The time-axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f ₂ ) are determined as abnormal respiration in the normal respiration determiner and the normal respiration determiner that analyzes the respiration rate ( f 2 ) of the measurement target It may include an apnea determining unit for determining whether the measurement target is apnea by measuring the amount of change in the movement and respiration signal of the measurement target from the radio signal.

Here, the optimum respiration position determining unit may determine the optimum respiration position of the measurement target after removing a background signal from the received radio signal for more accurate determination of the optimum respiration position.

In one embodiment, the optimal respiration position determining unit may determine a position having a maximum dispersion or maximum energy of a radio signal received from the entire detection area as an optimal respiration position of the measurement target.

In addition, when the radio wave signal reflected on the position where the received radio signal has the maximum dispersion or maximum energy is determined as normal respiration by the normal respiration determining unit, the optimal respiration position determining unit determines the position of the optimal respiration position of the measurement target can be decided with

Here, the normal respiration determining unit is a first radio signal extracted from a radio signal reflected on a position where the received radio signal has the maximum dispersion or maximum energy for a predetermined time, and a second radio wave delaying the first radio signal by a predetermined time. The similarity between the two radio signals is calculated through an auto-correlation operation between the signals, and the time of the measurement target is measured through the period between the peaks in which the similarity between the two radio signals calculated by the auto-correlation operation represents the maximum value. Axis-based respiration rate ( f ₁ ) is calculated, and the received radio signal is extracted for a predetermined time at a position where the received radio signal has the maximum dispersion or maximum energy, and then the maximum of the radio signal through Fourier transform operation Calculates the frequency, and is configured to calculate the frequency axis-based respiration rate (f ₂ ) of the measurement target through the frequency calculated by the Fourier transform operation.

In addition, the normal respiration determining unit when the absolute value of the difference between the time axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f ₂ ) calculated from the received radio signal is within a predetermined range, the radio signal can be determined as a normal respiratory signal.

In another example, the normal respiration determining unit is the time axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f ₂ ) for a predetermined time on the position where the received radio signal has the maximum dispersion or maximum energy. When the absolute value of the difference is maintained within a predetermined range, the radio signal may be determined as a normal respiration signal.

The apnea determining unit has an arbitrary maximum signal strength (M _abnormal ) in the first time interval between the abnormal respiration detection time point ( T ₁ ) and the abnormal respiration entry time point ( T ₂ ) corresponding to a predetermined time ( T ) therefrom. When a certain level of the maximum signal intensity ( M _normal ) in the second time interval between the normal respiration progress point ( T ₃ ) and the abnormal respiration entry point ( T ₂ ) of is exceeded, the abnormal respiration entry point ( T ₂ ) is assumed to be the start time of the movement of the measurement target, and the abnormal respiration detection time point ( T ₁ ) and the abnormal respiration entry point ( T ₂ ) corresponding to a predetermined time ( T ) therefrom. When the maximum signal strength ( M _abnormal ) is less than or equal to a certain level of the maximum signal strength ( M _normal ) in the second time interval between any normal breathing progression time ( T ₃ ) and abnormal breathing entry time ( T _{2 ), the abnormal} The respiration entry point ( T ₂ ) may be estimated to be the apnea start time point of the measurement target.

When it is estimated that the abnormal respiration entry time point ( T ₂ ) is the apnea start time point of the measurement target, the apnea determining unit is between the arbitrary normal respiration progress time point ( T ₃ ) and the abnormal respiration detection time point ( T ₁ ). When the change in the signal strength extracted during the time interval exhibits linearity, the abnormal respiration entry time ( T ₂ ) may be determined as the apnea start time of the measurement target.

In addition, the apnea determining unit the amount of change in the signal strength in the third time interval between the arbitrary normal respiration progress time point ( T ₃ ) and a time point ( T ₄ ) after a predetermined time (T ) therefrom (L _current) ) is the abnormal respiration detection time point ( T ₁ ) and a predetermined time ( T ) therefrom before the abnormal respiration entry time point ( T ₂ ) in the first time interval between the change amount of the signal strength ( L _previous ) Constant When the level is exceeded, it is determined that the change in signal strength indicates linearity, and between the arbitrary normal respiration time point ( T ₃ ) and the time point ( T ₄ ) after a predetermined time ( T ) therefrom The change amount (L _current ) of the signal strength in the third time interval is the first time between the abnormal respiration detection time point ( T ₁ ) and the abnormal respiration entry time point ( T ₂ ) corresponding to a predetermined time ( T) therefrom When it is less than a certain level of the change amount (L _previous ) of the signal strength in the interval, it may be determined that the change in the signal strength does not exhibit linearity.

Additionally, the apnea determining unit is the maximum signal strength in the first time interval between the abnormal respiration detection time point ( T ₁ ) and the abnormal respiration entry time point ( T ₂ ) corresponding to a predetermined time ( T ) prior thereto ( M _abnormal) ) is set as the apnea maintenance reference signal strength ( M _reference ), and the signal strength (M _nobreathing ) measured at any time after the abnormal respiration detection time point ( T ₁ ) is the apnea maintenance reference signal strength ( M _reference ) When it exceeds a certain level, it is determined that the apnea of the measurement target is stopped, and the signal strength (M _nobreathing ) measured at any time after the abnormal respiration detection time ( T ₁ ) is the apnea maintenance reference signal strength ( If it is below a certain level of M _reference ), it may be determined that the apnea of the measurement target is maintained.

In another example, the apnea determining unit is the abnormal respiration detection time point ( T ₁ ) and a predetermined time ( T ) therefrom before the abnormal respiration entry time point ( T ₂ ) of the signal strength in the first time interval between the The change amount ( L _previous ) is set as the change amount (L _reference ) of the apnea maintenance reference signal strength , and the change amount (L _nobreathing ) of the signal strength at the same time interval as the first time interval after the abnormal respiration detection time ( T _{1 )} When the change amount of the apnea maintenance reference signal intensity ( L _reference ) exceeds a certain level, it is determined that the apnea of the measurement target is stopped, and the time equal to the first time interval after the abnormal respiration detection time point ( T _{1 )} When the change amount (L _nobreathing ) of the signal intensity in the interval is less than a certain level of the change amount (L _reference ) of the apnea maintenance reference signal intensity, it may be determined that the apnea of the measurement target is maintained.

Additionally, in the apnea detection system according to an embodiment of the present invention, when the apnea of the measurement target is detected by the apnea determining unit, the apnea warning unit for generating an apnea warning alarm and the normal respiration determining unit determine normal breathing It may further include a respiratory rate calculating unit for calculating the time axis-based respiration rate ( f _{1) of the measurement target from the radio signal.}

According to the present invention, an irregular respiration signal (that is, a respiration signal not similar to a Sin or Cos waveform) of a user or a measurement target is accurately recognized and measured as a respiration signal, and whether normal respiration enters into abnormal respiration is accurately detected. can do.

In addition, according to the present invention, even under a noise environment in which the user or the measurement object is located in a remote location or there is a dynamic object representing a movement around the user or the measurement object, the respiration signal of the user or the measurement object is accurately measured and normal breathing therefrom. It is possible to accurately detect whether or not it enters into abnormal respiration.

In addition, according to the present invention, it is possible to accurately detect apnea symptoms by accurately distinguishing between abnormal breathing according to the movement of a user or a measurement target and apnea during sleep, and at the same time reflecting the characteristics of apnea symptoms that may appear after normal breathing is observed. can

1 is a view showing an overall operation flow chart of the apnea detection system according to an embodiment of the present invention.
Figure 2 schematically shows the step of determining the optimal respiration position of the measurement target using the apnea detection system according to an embodiment of the present invention.
3 is a flowchart illustrating an operation of determining an optimal respiration position of a measurement target on an apnea detection system according to an embodiment of the present invention.
4 is a flowchart illustrating an operation of determining whether a normal respiration signal is detected in FIG. 3 .
Figure 5a shows the extraction result of the abnormal respiration signal, Figure 5b shows the Fourier transform operation result of the abnormal respiration signal of Figure 5a, Figure 5c is the autocorrelation of the abnormal respiration signal shown in Figure 5a (auto) -correlation) shows the result of the operation.
Figure 6a shows the extraction result of the normal respiration signal, Figure 6b shows the Fourier transform operation result of the normal respiration signal shown in Figure 6a, Figure 6c is the autocorrelation of the normal respiration signal shown in Figure 6a ( auto-correlation) operation result.
7 is a flowchart illustrating an operation of an apnea determining unit on an apnea detection system according to an embodiment of the present invention.
Figure 8a shows the extraction result of the abnormal respiration signal when abnormal respiration due to the movement of the measurement target is detected, and Figure 8b shows the extraction result of the abnormal respiration signal when the abnormal respiration due to the apnea of the measurement target is detected. .
9A and 9B illustrate changes in intensity according to time change of an abnormal respiration signal when abnormal respiration due to apnea of a measurement target is detected.

In order to better understand the present invention, certain terms are defined herein for convenience. Unless defined otherwise herein, scientific and technical terms used herein shall have the meanings commonly understood by one of ordinary skill in the art. Also, unless the context specifically dictates otherwise, it should be understood that a term in the singular includes its plural form as well, and a term in the plural form also includes its singular form.

Hereinafter, an apnea detection system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings of the present invention.

The present invention relates to a real-time apnea measurement system using a radio signal, and a measurement target intended to measure respiration (or apnea) by a user who directly uses the system or the system (hereinafter, both the user and the measurement target are referred to as measurement targets) It is a system for detecting whether apnea occurs while measuring the breathing pattern or rate of breathing.

First, the apnea detection system according to an embodiment of the present invention is premised on accurately capturing the respiration signal of the measurement target indicating normal respiration.

In addition, the apnea detection system according to an embodiment of the present invention is based on the fact that the apnea symptom of the measurement target is a phenomenon that may appear after a normal respiration signal is observed.

Therefore, the apnea detection system according to an embodiment of the present invention aims to accurately determine whether an abnormal respiration signal corresponds to an apnea signal when an abnormal respiration signal occurs while a normal respiration signal is observed from a measurement target. .

First, the apnea detection system according to an embodiment of the present invention does not measure respiration with only the periodicity of the radio signal reflected by the measurement object, but determines the optimal respiration position from the radio signal reflected by the measurement object, It is characterized in that the respiration signal induced by respiration is effectively extracted from the radio wave signal reflected from the position, and the respiration pattern and/or respiration rate are accurately measured therefrom.

Specifically, the apnea detection system according to an embodiment of the present invention includes a transmitter for transmitting a radio signal to a detection area, and a receiver for receiving a radio signal reflected by a measurement target within the detection area. It may include a control unit for measuring the respiration pattern, respiration rate, and whether or not apnea of the measurement target from the signal.

The transceiver includes a transmitter for transmitting a radio signal to the detection area, and a receiver for receiving a radio signal reflected by a measurement target existing in the detection area. In this case, the receiver may further include an amplifier that increases the strength of the received radio signal.

The radio signal transmitted and received by the transceiver may be, without limitation, a radio signal used in a general measurement system.

In addition, the apnea detection system according to an embodiment of the present invention is preferably built based on IR-UWB (impulse radio ultra wideband) communication technology.

IR-UWB communication technology uses a very narrow impulse ranging from several ns to several hundreds of ps to detect a radio wave signal reflected from a measurement target with higher accuracy than narrowband signals and effectively extract a breathing signal from it. can be beneficial

The control unit may include elements such as a microprocessor and a memory, and the control unit is configured to perform an algorithm for processing radio signals transmitted and received by the transceiver.

Specifically, the control unit calculates the time-axis-based respiration rate and the frequency-axis-based respiration rate from the radio signal reflected from the optimum respiration position determining unit and the optimum respiration position of the measurement target for determining the optimum respiration position of the measurement target, and measuring from this It includes a normal respiration determination unit for determining whether the object is breathing normally, and an apnea determination unit for determining whether the object to be measured is apnea from the radio signal determined as abnormal respiration in the normal respiration determination unit.

1 is a flowchart illustrating an overall operation of the apnea detection system according to an embodiment of the present invention. During the initial operation, the apnea detection system according to an embodiment of the present invention transmits a radio signal to a detection area.

Real-time wireless respiration system according to an embodiment of the present invention may record the time and/or the distance to the measurement object reflected by the radio signal reflected by the radio wave signal is received by the measurement target existing in the detection area.

Then, the control unit of the apnea detection system according to an embodiment of the present invention removes the background signal from the radio signal received through the receiver in order to select only the effective radio signal reflected from the measurement target from the received radio signal, and , is configured to classify the propagation signal from which the background signal has been removed according to the reflected distance.

The background signal is selected from static objects (eg, desks, flowerpots, etc.) and/or dynamic objects that reflect radio signals of less than a predetermined intensity (eg, movement of curtains by wind, movement of small animals, etc.) It may be a signal received by being reflected from at least one object. In addition, even for a static object, a radio signal reflected by a metal material that strongly reflects a radio signal than a dynamic object or a dynamic object (for example, a fan, etc.) larger than the measurement target is also converted into a background signal by presetting the signal strength. can be considered In addition, if the measurement target is a small animal, the strength of the radio signal, which is the standard of the background signal, is smaller than that of the measurement target is a human, and the background signal is generally based on the strength of the signal generated by the human as the background signal. can be removed.

That is, the apnea detection system according to an embodiment of the present invention is a system for effectively detecting only a radio wave signal reflected from a measurement target, and removes a signal reflected from a static object originally existing within the detection area by noise processing. This enables more accurate breathing measurement.

The above-mentioned background signal may be removed through a technique commonly known in the art (eg, a method of extracting and removing a clutter signal through a cumulative average signal) in order to remove the background signal from the received propagation signal.

The propagation signal from which the background signal is removed through the above-described process is classified according to the reflected distance. For example, the distance at which the received radio signal is reflected is the time difference between the time _{at which the radio signal is transmitted (t 0} ) and the time at which the radio signal is received (t _{1 ) after being reflected by an object (Time-of-arrive)} can be estimated based on The reflected distance _{can be calculated as (t 1} -t ₀ )*c/2, where c is the transmission speed of the radio signal in air.

When the background signal is removed from the received radio signal and classification according to distance is completed, the control unit records the radio signal by time-reflection distance based on the intensity (dispersion and/or energy) of the received radio signal by reflection distance .

After the propagation signal for each reflected distance is individually and sequentially generated according to the passage of time, the optimum respiration position determining unit determines the optimum respiration position of the measurement target.

Here, as shown in FIG. 2 schematically illustrating the step of determining the optimal respiration position of the measurement target using the apnea detection system according to an embodiment of the present invention, the optimum respiration position includes the respiration signal of the measurement target. The position, that is, the position where the breathing pattern of the measurement target is accurately reflected, and capturing the correct breathing signal from the radio signal reflected and received for each reflection distance must be preceded for accurate breathing measurement.

In the case of a system that lacks a configuration to determine the optimal respiration position, as in a short-distance measurement system, the respiration signal of the measurement target is inevitably received strongly, making it easy to measure respiration, or there is no movement other than respiration around the measurement object itself or around the measurement object. There is no choice but to be applied only when only the respiratory signal is received.

Accordingly, it is difficult to accurately capture a respiration signal in a noisy environment where the measurement target is located at a distance or there is a dynamic object indicating movement around the measurement target, and there is a possibility that movement other than respiration may be mistaken for a respiration signal. exist.

On the other hand, the apnea detection system according to an embodiment of the present invention not only determines the optimal respiration position of the measurement target after removing the background signal from the received radio signal, but also determines the radio signal received from the entire detection area is the maximum By determining the location with dispersion or maximum energy as the optimal breathing position of the measurement target, it is to compensate for the disadvantages of the existing method that can generate an apnea alarm during normal breathing of the measurement target as the noise location is mistaken for the measurement target's breathing position. It is possible.

More specifically, as shown in FIG. 3 showing an operation flowchart of the step of determining the optimal respiration position of the measurement target on the apnea detection system according to an embodiment of the present invention, apnea detection system according to an embodiment of the present invention The optimal respiration position determining unit applied to first selects the optimal respiration candidate position from the time-reflected radio signal for each distance from which the background signal is removed, the position having the maximum dispersion or maximum energy.

That is, the propagation signal at the optimal respiration candidate position appears as a change in intensity over time (see FIG. 6A ) of the radio signals reflected from the same distance.

Then, it is determined whether the respiration signal extracted from the optimal respiration candidate position represents a normal respiration signal for a predetermined time, and in the case of a normal respiration signal, the respiration signal position is fixed and continuous respiration measurement is made, but the abnormal respiration signal If it is determined that there is, the corresponding position is excluded from the optimal respiration candidate position for a predetermined time.

4 is an operation flowchart of the step of determining whether the respiration signal at the optimal respiration candidate position is a normal respiration signal, the steps may be performed by the normal respiration determiner, but is not necessarily limited thereto.

In one embodiment, the normal respiration determination unit may specifically determine whether the normal respiration signal through the following steps.

1) Autocorrelation between a first radio signal obtained by extracting a radio signal reflected from a position at which the received radio signal has maximum dispersion or maximum energy for a predetermined time, and a second radio signal obtained by delaying the first radio signal by a predetermined time The similarity between two radio signals is calculated through an (auto-correlation) operation, and the time axis-based respiration rate ( calculating f ₁ );

2) After extracting the received radio signal for a predetermined time at the position where the received radio signal has the maximum dispersion or maximum energy, the maximum frequency of the radio signal is calculated through a Fourier transform operation, and in the Fourier transform operation Computing the frequency axis-based respiration rate ( f ₂ ) of the measurement target through the frequency calculated by;

3) When the absolute value of the difference between the time axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f ₂ ) is within a predetermined range, the time axis-based respiration rate ( f ₁ ) for a predetermined time and Determining whether the absolute value of the difference between the frequency axis-based respiration rate ( f _{2) is maintained within a predetermined range;}

4) the absolute value of the difference between the time-axis-based respiration rate ( f ₁ ) and the frequency-axis-based respiration rate ( f ₂ ) measured at a position where the received radio signal has the maximum dispersion or maximum energy is outside a predetermined range, or If the absolute value of the difference between the time axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f ₂ ) for a predetermined time is not maintained within a predetermined range, the position is excluded from the optimal respiration candidate position, and , repeating the above steps 1) to 3) on the position where the radio signal received in the remaining area has the maximum dispersion or maximum energy.

The "predetermined time ( t ₁ )" for extracting the propagation signal reflected on the position where the propagation signal received in step 1) and step 2) has the maximum dispersion or maximum energy, the extracted propagation signal is subjected to autocorrelation and Fourier transform It means the time sufficient to obtain a meaningful result when the operation is performed.

The "predetermined time ( t ₁ )" in step 1) may be appropriately adjusted according to the breathing pattern of the measurement target , for example, the "predetermined time ( t ₁ )" in step 1) is a respiration signal. It may be sufficient time for the troughs and ridges of the expected propagation signal to be received at least twice.

In step 3), the “predetermined range ( d )” in which the absolute value of the difference between the time axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f ₂ ) should exist is determined according to the breathing pattern of the measurement target. Although it can vary, the difference between the time-axis-based respiration rate ( f ₁ ) and the frequency-axis-based respiration rate ( f ₂ ) is the difference between the time-axis-based respiration rate and For a signal, the "predetermined range ( d )" is less than 10% of the actual respiration rate (or the value of either the time axis based respiration rate ( f ₁ ) or the frequency axis based respiration rate ( f ₂ )), preferably 5 % may be less.

For example, the absolute value of the difference between the time axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f ₂ ) measured on a position where the received radio signal has the maximum dispersion or maximum energy is within a predetermined range The absolute value of the difference between the time-axis-based respiration rate ( f ₁ ) and the frequency-axis-based respiration rate ( f ₂ ) measured outside the case and the position where the received radio signal has the maximum dispersion or maximum energy is within a predetermined range Cases are shown in Figs. 5 and 6, respectively.

First, FIG. 5a shows the extraction result of the abnormal respiration signal, FIG. 5b shows the Fourier transform calculation result of the abnormal respiration signal of FIG. 5a, and FIG. 5c shows the autocorrelation of the abnormal respiration signal shown in FIG. 5a (auto-correlation) The result of the operation is shown.

As shown in FIG. 5A , in the case of an abnormal respiration signal, the Sin or Cos waveform indicated by the normal respiration signal generally does not appear. For example, when the measurement is performed in a noisy environment around the measurement object or the optimal respiration position of the measurement object is not precisely specified, the abnormal respiration signal in the form of FIG. 5A is highly likely to be extracted.

As shown in Fig. 5b, after Fourier transform operation of the abnormal respiration signal of Fig. 5a, when the respiration rate is calculated through the maximum frequency value, a result value of 9.7 times / min is obtained, whereas in Fig. 5c As shown, the respiration rate obtained through the similarity between the two signals obtained through the auto-correlation operation between the abnormal respiration signal of FIG. 5a and the signal delayed by a predetermined time is 142.3 times/min.

The difference between the time axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f ₂ ) calculated from the respiration signal shown in FIG. 5A is the actual respiration rate (or time axis-based respiration rate ( f ₁ ) and frequency axis-based respiration Since it far exceeds 10% of the number f ₂ ), it can be determined that the respiratory signal of FIG. 5A is an abnormal signal.

Figure 6a shows the extraction result of the normal respiration signal, Figure 6b shows the Fourier transform operation result of the normal respiration signal shown in Figure 6a, Figure 6c is the autocorrelation of the normal respiration signal shown in Figure 6a ( auto-correlation) operation result.

As shown in Fig. 6b, after Fourier transform operation of the normal respiration signal of Fig. 6a, when calculating the respiration rate through the maximum frequency value, a result value of 29.7 times / min is obtained, whereas in Fig. 6c As shown, the respiration rate obtained through the similarity between the two signals obtained through the auto-correlation operation between the normal respiration signal of FIG. 6a and the signal delayed by a predetermined time is 30.2 times/min.

The difference between the time axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f ₂ ) calculated from the respiration signal shown in FIG. 6A is the actual respiration rate (or time axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate) It corresponds to less than 10% of the number ( f ₂ ) of any one of the values), and it can be determined that the respiratory signal of FIG. 6A is a normal signal.

That is, in the step 3), the apnea detection system according to the present invention provides a noise environment in which a signal by a dynamic object (not sufficiently removed as a background signal) indicating a motion in the vicinity of the measurement object or the location of the measurement object is present. It is possible not only to capture the respiration signal representing the periodicity of the measurement target and accurately measure the respiration rate from it, but also to calculate the time-axis-based respiration rate ( f ₁ ) as a result of the frequency-axis-based respiration rate ( f ₂ ). Accuracy can be improved by collating with the calculation result.

In addition, in step 3), even if the absolute value of the difference between the time axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f ₂ ) is within a predetermined range, such a state is “a predetermined time t ₂ )" is required to be maintained.

Here, the "predetermined time ( t ₂ )" is the time spent in determining whether a normal respiration signal is present at one optimal respiration candidate position, and as the "predetermined time ( t ₂ )" increases, the It is possible to more accurately determine whether the signal is a normal respiration signal, but since the time consumed at one location increases, the time required to scan the entire detection area may increase.

In step 4), the absolute value of the difference between the time axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f ₂ ) measured at a position where the received radio signal has the maximum dispersion or maximum energy is within a predetermined range out, or when the absolute value of the difference of the time axis based on respiratory rate (f ₁₎ and the frequency axis based on respiratory rate (f ₂₎ that is not maintained within a predetermined range for a predetermined time (T _2), optimally the position As a step of excluding from the breathing candidate position, in this case, the position may be excluded for a predetermined time (t _{3 ).}

Here, the "predetermined time ( t ₃ )" is a variable that determines how long the position is not to be searched again when a normal breathing signal is not detected at the optimal respiration candidate position, and the "predetermined time ( t ₃ )" As the value increases, the time required to scan the entire detection area decreases as the time required for one position decreases. However, since the detection time for one position is small, the detection time is small even though it is a normal breathing signal. There is a possibility that it cannot.

Therefore, it is preferable to properly balance the "predetermined time ( t ₂ )" and the "predetermined time ( t ₃ )" in consideration of the time allowed for scanning the entire detection area, and the like.

When the normal respiration determining unit determines that the radio signal at the optimal respiration candidate position (or the next position) is the normal respiration signal by the above-described steps 1) to 4), the position is the optimum respiration by the optimum respiration position determination unit location is determined.

Subsequently, a respiration signal is continuously extracted from the radio wave signal reflected from the optimal respiration position of the measurement target, and whether the extracted respiration signal is a normal respiration signal is re-measured.

That is, the optimal respiration position determiner receives information on whether the radio signal at the optimal respiration candidate position is a normal respiration signal by the normal respiration determiner and determines the optimum respiration position, and the When the optimal breathing position is determined, it is configured to be re-measured by the normal breathing determining unit whether the measurement target shows a normal breathing signal at the corresponding position.

At this time, when it is determined that the measurement target at the optimal respiration position represents a normal respiration signal, the respiration rate calculation is performed from the respiration signal extracted by the respiration rate calculator.

Here, the operation of calculating the respiration rate can be viewed as a repeating operation of step 1) (autocorrelation calculation) for determining whether a normal respiration signal is present at the above-described optimal respiration candidate position.

When the respiratory signal is extracted for a predetermined time ( t ₁ ) at the optimal respiration position, the respiration signal may be obtained as shown in FIG. 6A .

Looking at the initially extracted respiration signal shown in FIG. 6A , the periodicity of the bone and the crest can be observed to some extent, but there are cases in which it is difficult to accurately designate the maximum value of the signal at the crest in which the respiration cycle is accurately reflected. At this time, if the maximum value of the signal is not precisely specified for each adjacent floor, the respiration cycle may be calculated irregularly, and inaccurate respiration measurement is inevitably made.

The operation of calculating the respiration rate on the apnea detection system according to an embodiment of the present invention is based on an autocorrelation operation, and the autocorrelation operation is an original extracted respiration signal (first radio signal) and a predetermined time (for example, , as a calculation of the similarity of the respiration signal (second radio signal) delayed by the respiration cycle reference 1 or 2 cycles), for example, depending on the degree of delay of the second radio signal with respect to the first radio signal It can be defined as a harmonic mean of changing similarity values.

As shown in Fig. 6c, when the measured radio signal has a certain period, a peak showing the maximum similarity will appear according to the constant period, and the time axis-based respiration rate of the measurement target is calculated through the period between the peaks. it is possible to do Unlike the respiration signal shown in Fig. 6a, the signal shown in Fig. 6c can accurately designate the maximum value of the signal (similarity) for each crest, so it is possible to accurately measure the respiration along with the calculation of the regular respiration cycle. There is this.

In addition, when the normal respiration determination unit determines that the measurement target represents an abnormal respiration signal at the optimal respiration position, the respiration rate calculation is stopped by the respiration rate calculation unit, and the apnea determination unit is measured from the radio signal determined as abnormal respiration by the normal respiration determination unit By measuring the movement of the target and the amount of change in the respiration signal, it is determined whether the target is apnea or not.

First, when determining an optimal respiration position, the cause of conversion to an abnormal respiration signal after it is determined to indicate a normal respiration signal may be classified into the following cases.

- When the periodicity of the respiration signal measured by the system is changed as the measurement object moves (corresponding to abnormal respiration but not apnea)

- When the measurement target shows apnea symptoms (corresponding to abnormal breathing, corresponding to apnea)

Therefore, referring to FIG. 7 showing an operation flowchart of the apnea determination unit on the apnea detection system according to an embodiment of the present invention, the moment when the measurement target switches from normal breathing to abnormal breathing is captured, and from this, the recent movement of the measurement target After determining (observing the amount of change in movement), if the measurement target does not show a significant change in movement recently, the correlation between the abnormal respiration signal and the respiration signal appearing during apnea (the amount of change in the respiration signal for a certain time) is examined.

That is, according to the apnea detection system according to an embodiment of the present invention, when the measurement target does not show significant movement recently and the abnormal respiration signal of the measurement target shows a large correlation with the respiration signal appearing during apnea, the measurement target is and determine that the person is apnea.

First, the step of determining whether the measurement target has a recent movement (movement change observation) will be described in more detail.

The step is a step of verifying whether the cause of the abnormal respiration is due to the movement of the measurement target, not the actual apnea, when the measurement target switches from normal breathing to abnormal breathing.

Therefore, the maximum signal strength ( M _abnormal ) (maximum degree of movement) in the first time interval between the abnormal respiration detection time point ( T ₁ ) and the abnormal respiration entry time point ( T ₂ ) corresponding to a predetermined time ( T ) therefrom. , which can be replaced with the average signal strength) is the maximum signal in the second time interval between any normal respiration progression time point ( T ₃ ) and the abnormal respiration entry point ( T _{2 ) at which normal respiration is judged to be in progress.} By comparing the intensity ( M _normal ) (represents the maximum degree of movement and can be replaced with the average signal intensity), it can be confirmed whether the cause of the abnormal respiration is due to the movement of the measurement target.

Here, a time point prior to a predetermined time ( T ) from the abnormal respiration detection time point ( T ₁ ) is defined as an abnormal respiration entry time point ( T ₂ ), and the abnormal respiration detection time point ( T ₁ ) and abnormal respiration entry time point ( T ₂ ) Observing the maximum signal strength (M _abnormal ) in the first time interval between 2 ) is because it takes a certain amount of time for the periodicity of the normal respiration signal to be shifted due to movement or apnea of the measurement target.

Specifically, whether the cause of the abnormal respiration is due to the movement of the measurement target may be determined by the following equation.

M _abnormal > δ _M × M _normal : It is estimated that the measurement object has moved

M _abnormal ≤ δ _M × M _normal : It is assumed that the measurement target has not moved.

Here, δ _M is a correction coefficient for the maximum signal strength during normal breathing, and may be set as a coefficient greater than 1 at least in consideration of variables that may appear during normal breathing.

At this time, if the correction coefficient δ _M is excessively large, the probability of estimating that the measurement object has moved even though there is no actual movement decreases, but sensitivity to small movements may decrease. It needs to be properly adjusted.

Figure 8a shows the extraction result of the abnormal respiration signal when abnormal respiration due to the movement of the measurement target is detected, and Figure 8b shows the extraction result of the abnormal respiration signal when the abnormal respiration due to the apnea of the measurement target is detected. .

In the case of the abnormal respiration signal shown in FIG. 8A , the maximum signal in the first time interval between the abnormal respiration detection time point ( T ₁ ) and the abnormal respiration entry time point ( T ₂ ) corresponding to a predetermined time ( T ) prior thereto The intensity ( M _abnormal ) exceeds the product of the correction factor δ _M by the maximum signal intensity ( M _normal ) in the second time interval between any normal respiratory progression time point ( T ₃ ) and abnormal respiratory entry point ( T _{2 ).} Therefore, the abnormal respiration entry point ( T ₂ ) may be estimated as a time point at which the movement of the measurement target is started.

Accordingly, as shown in FIG. 8A , when it is estimated that an abnormal respiration signal is generated as the measurement object moves, the apnea determining unit determines that the measurement object is not apnea.

On the other hand, in the case of the abnormal respiration signal shown in FIG. 8B , the abnormal respiration detection time point ( T ₁ ) and the abnormal respiration entry time point ( T ₂ ) corresponding to a predetermined time ( T ) before the first time interval in the first time interval The maximum signal strength ( M _abnormal ) is the product of the maximum signal strength ( M _normal ) in the second time interval between any normal respiratory progression time point ( T ₃ ) and abnormal breathing entry time point ( T ₂ ) and the correction factor δ _M . Since the following, the abnormal respiration entry time ( T ₂ ) can be estimated to be the apnea start time of the measurement target, and it is concluded that the cause of the abnormal respiration signal is not due to the movement of the measurement target (influence on the respiratory cycle) There is no movement enough to line).

When it is concluded by the apnea decision unit that the cause of the abnormal respiration signal is not due to the movement of the measurement target, the correlation between the abnormal respiration signal and the respiration signal appearing during apnea (the amount of change in the respiration signal over a certain period of time) is examined. .

Accordingly, when it is estimated that the abnormal respiration entry point ( T ₂ ) is the apnea start time of the measurement target , the apnea determining unit is between the arbitrary normal respiration progress time point ( T ₃ ) and the abnormal respiration detection time point ( T ₁ ) It is determined whether the change in signal strength extracted during the time interval of .

The linearity indicated by the change in signal strength is, as shown in FIG. 9a, when there is a change in the respiration cycle on the graph showing the respiration signal intensity according to time change, the respiration signal does not show periodicity, and increases or decreases almost linearly. It means the shape, and in particular, linearity on a graph showing the intensity of the respiration signal according to time change is a characteristic observed when the measurement target exhibits apnea symptoms.

Alternatively, instead of linearity, it is possible to determine whether the measurement target is apnea based on the Y-axis movement distance for a certain period of time on a graph showing the respiration intensity according to time change.

Here, the Y-axis movement distance for a certain time is the total sum of Y-axis change values that change for a certain time, and may be calculated by the following equation.

L : Total moving distance, N : Accumulated respiration signal size, B[x] : Y value (strength) of the xth respiration signal

In one embodiment, the linearity representing the apnea symptom of the measurement target may be determined by the following equation.

L _current > λ × L _previous : Determining that the measurement target is apnea

L _{current ≤} λ × L _previous : Determining that the measurement target is not apnea

Here, λ is a correction coefficient for the amount of change in signal strength at a predetermined time interval during apnea, and may be set as a coefficient greater than at least 1 in consideration of variables that may appear during apnea.

At this time, if the correction coefficient λ is excessively large, the probability of erroneous judgment on the existence of linearity on the graph may be reduced, but even if the measurement object is apnea, if the apnea of the measurement object does not show strong linearity on the graph, apnea Since there is a risk that the measurement will not be determined as , it needs to be appropriately adjusted according to the sleep pattern of the measurement target.

9B is a diagram illustrating an auto-correlation calculation result of an abnormal respiration signal when abnormal respiration due to apnea of a measurement target is detected.

Here, the change amount (L _current ) of the signal strength in the third time interval between the arbitrary normal respiration progress time point ( T ₃ ) and the time point ( T ₄ ) after a predetermined time (T ) therefrom is the abnormal respiration The product of the change amount (L _previous ) of the signal strength in the first time interval between the detection time ( T ₁ ) and the abnormal respiration entry time ( T ₂ ) corresponding to a predetermined time ( T ) before and the correction factor λ If it is exceeded, it is determined that the change in signal strength indicates linearity, and at this time, it is determined that the measurement target is in apnea.

On the other hand, the change amount (L _current ) of the signal intensity in the third time interval between the arbitrary normal respiration progress time point ( T ₃ ) and the time point ( T ₄ ) after a predetermined time (T ) therefrom is the abnormal respiration The product of the change amount (L _previous ) of the signal strength in the first time interval between the detection time ( T ₁ ) and the abnormal respiration entry time ( T ₂ ) corresponding to a predetermined time ( T ) before the detection time (T 1 ) and the correction factor λ Below, it is determined that the change in signal strength does not exhibit linearity, and in this case, it is determined that the measurement target is not in apnea.

In addition, the apnea measurement system according to an embodiment of the present invention further includes an apnea warning unit that generates an apnea warning alarm when it is determined that the measurement target is in apnea, and observes whether the measurement target exhibits continuous apnea symptoms together with this. do.

Whether the measurement target shows continuous apnea symptoms can be confirmed by measuring the amount of change in the motion signal and/or the respiration signal of the measurement target.

In one embodiment, the maximum signal intensity (M _abnormal ) in the first time interval between the abnormal respiration detection time point ( T ₁ ) and the abnormal respiration entry time point ( T ₂ ) corresponding to a predetermined time ( T ) prior thereto is set as the apnea maintenance reference signal strength ( M _reference ) (see FIG. 8b ), and the signal strength ( M _nobreathing ) measured at any time after the abnormal respiration detection time point ( T ₁ ) is the apnea maintenance reference signal strength ( M _reference) ), a large movement of the measurement target occurs (by an apnea warning alarm by the apnea warning unit, etc.), and accordingly, it can be determined that apnea has stopped.

On the other hand, when the signal strength (M _nobreathing ) measured at any time after the abnormal respiration detection time point (T ₁ ) is below a certain level of the apnea maintenance reference signal strength ( M _reference ), it is determined that the apnea of the measurement target is maintained, and , it can repeatedly generate an apnea warning alarm.

Here, δ _nobreathing may be used as a correction coefficient between the apnea maintenance reference signal strength ( M _reference ) and the signal strength ( M _nobreathing ) measured at any time point, and the correction coefficient is a variable that may appear during apnea and / or measurement target It can be appropriately adjusted according to the sleep pattern of the

In another example, the amount of change in the signal strength in the first time interval between the abnormal respiration detection time point ( T ₁ ) and the abnormal respiration entry time point ( T ₂ ) corresponding to a predetermined time ( T ) prior thereto ( L _previous ) is set as the amount of change (L _reference ) of the apnea maintenance reference signal intensity (see FIG. 9b), and the change amount of the signal intensity (L _nobreathing ) at the same time interval as the first time interval after the abnormal respiration detection time point (T ₁ ) is apnea When a certain level of the change amount ( L _reference ) of the maintenance reference signal strength is exceeded, it may be determined that the apnea of the measurement target is stopped.

On the other hand, when the change amount (L _nobreathing ) of the signal strength in the same time interval as the first time interval after the abnormal respiration detection time point (T ₁ ) is less than a certain level of the change amount ( L _{reference) of the apnea maintenance reference signal strength, the measurement target of} It may determine that the apnea is maintained and repeatedly generate an apnea warning alarm.

Similarly, λ _nobreathing may be used as a correction coefficient for the change amount of the apnea maintenance reference signal intensity ( L _reference ) and the change amount of the signal intensity change ( L _nobreathing ) in the same time interval as the first time interval, and the correction coefficient may appear during apnea. It may be appropriately adjusted according to the existing variables and/or the sleep pattern of the measurement target.

In the above, although an embodiment of the present invention has been described, those of ordinary skill in the art can add, change, delete or add components within the scope that does not depart from the spirit of the present invention described in the claims. The present invention may be variously modified and changed by, etc., and this will also be included within the scope of the present invention.

Claims (14)

a transceiver comprising a transmitter for transmitting a radio signal to a detection area and a receiver for receiving a radio signal reflected by a measurement target within the detection area;
an optimum respiration position determining unit for determining an optimum respiration position of the measurement target from the received radio signal;
Calculate the time-axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f ₂ ) of the measurement target from the radio wave signal reflected from the optimal respiration position, and the time axis-based respiration rate ( f ₁ ) and the frequency Normal respiration determining unit for analyzing the axis-based respiration rate ( f ₂ ) to determine whether the measurement target is respiration normally; and
an apnea determination unit for determining whether the measurement target is apnea by measuring the movement of the measurement target and a change amount of the respiration signal from the radio signal determined by the normal respiration determination unit as abnormal respiration;
containing,
Apnea detection system.
According to claim 1,
The optimal respiration position determining unit for determining the optimal respiration position of the measurement target after removing the background signal from the received radio signal (background subtraction),
Apnea detection system.
According to claim 1,
The optimal respiration position determining unit determines the position at which the radio signal received from the entire detection area has the maximum dispersion or maximum energy as the optimal respiration position of the measurement target,
Apnea detection system.
4. The method of claim 3,
The optimal breathing position determining unit,
When the radio signal reflected on the position where the received radio signal has the maximum dispersion or maximum energy is determined as normal respiration by the normal respiration determining unit, determining the position as the optimal respiration position of the measurement target,
Apnea detection system.
5. The method of claim 4,
The normal respiration determining unit,
Autocorrelation (auto) between a first propagation signal obtained by extracting a radio signal reflected from a position at which the received radio signal has maximum dispersion or maximum energy for a predetermined time and a second radio signal delaying the first radio signal by a predetermined time -correlation) calculation to calculate the similarity between the two radio signals, and the time axis-based respiration rate ( f _{1 )} of the measurement target through the period between the peaks in which the similarity between the two radio signals calculated by the autocorrelation operation represents the maximum value. ) is calculated,
After the received radio signal is extracted for a predetermined time at a position where the received radio signal has the maximum dispersion or maximum energy, the maximum frequency of the radio signal is calculated through a Fourier transform operation, and is calculated by the Fourier transform operation Calculate the frequency axis-based respiration rate ( f _{2 ) of the measurement target through the}
Apnea detection system.
6. The method of claim 5,
The normal respiration determining unit,
When the absolute value of the difference between the time axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f _{2 ) calculated from the received radio signal is within a predetermined range,}
determining the radio signal as a normal breathing signal,
Apnea detection system.
6. The method of claim 5,
The normal respiration determining unit,
The absolute value of the difference between the time axis-based respiration rate ( f ₁ ) and the frequency axis-based respiration rate ( f ₂ ) is maintained within a predetermined range for a predetermined time on a position where the received radio signal has the maximum dispersion or maximum energy if be,
determining the radio signal as a normal breathing signal,
Apnea detection system.
According to claim 1,
The apnea determining unit,
The maximum signal intensity (M _abnormal ) in the first time interval between the abnormal respiration detection time point ( T ₁ ) and the abnormal respiration entry time point ( T ₂ ) corresponding to a predetermined time ( T ) prior thereto is any normal respiration progression When the maximum signal intensity (M _normal ) in the second time interval between the time point ( T ₃ ) and the abnormal respiration entry point ( T ₂ ) exceeds a certain level, the abnormal respiration entry time point ( T ₂ ) is the measurement target It is estimated that it is the start time of the movement of
The maximum signal intensity (M _abnormal ) in the first time interval between the abnormal respiration detection time point ( T ₁ ) and the abnormal respiration entry time point ( T ₂ ) corresponding to a predetermined time ( T ) prior thereto is any normal respiration progression When the maximum signal intensity (M _normal ) in the second time interval between the time point ( T ₃ ) and the abnormal respiration entry point ( T ₂ ) is less than a certain level, the abnormal respiration entry time point ( T ₂ ) is the apnea of the measurement target presumed to be the time of initiation,
Apnea detection system.
9. The method of claim 8,
The apnea determining unit,
When it is estimated that the abnormal respiration entry time point ( T ₂ ) is the apnea start time point of the measurement target,
When the change in signal strength extracted during the time interval between the arbitrary normal respiration progress time point ( T ₃ ) and the abnormal respiration detection time point ( T ₁ ) shows linearity, the abnormal respiration entry time point ( T ₂ ) is the measurement target determined to be the onset of apnea of
Apnea detection system.
10. The method of claim 9,
The apnea determining unit,
The change amount (L _current ) of the signal intensity in the third time interval between the arbitrary normal respiration progress time point ( T ₃ ) and a time point ( T ₄ ) after a predetermined time (T ) therefrom is the abnormal respiration detection When it exceeds a certain level of the change amount (L _previous ) of the signal strength in the first time interval between the time point ( T ₁ ) and the abnormal respiration entry time point ( T ₂ ) corresponding to a predetermined time ( T ) before the time point ( T 1 ), It is determined that the change in signal strength indicates linearity,
The change amount (L _current ) of the signal intensity in the third time interval between the arbitrary normal respiration progress time point ( T ₃ ) and a time point ( T ₄ ) after a predetermined time (T ) therefrom is the abnormal respiration detection When it is less than a certain level of the change amount (L _previous ) of the signal strength in the first time interval between the time point ( T ₁ ) and the abnormal respiration entry time point ( T ₂ ) corresponding to a predetermined time ( T) before the time point (T 1 ), the signal Judging that the change in intensity does not show linearity,
Apnea detection system.
10. The method of claim 9,
The apnea determining unit,
The maximum signal strength (M _abnormal ) in the first time interval between the abnormal respiration detection time point ( T ₁ ) and the abnormal respiration entry time point ( T ₂ ) corresponding to a predetermined time ( T ) prior therefrom is the apnea maintenance reference signal set to the intensity ( M _reference ),
When the signal strength (M _nobreathing ) measured at any time after the abnormal respiration detection time point ( T ₁ ) exceeds a certain level of the apnea maintenance reference signal strength ( M _reference ), the apnea of the measurement target is stopped decide that,
When the signal strength (M _nobreathing ) measured at any time after the abnormal respiration detection time point ( T ₁ ) is below a certain level of the apnea maintenance reference signal strength ( M _reference ), it is determined that the apnea of the measurement target is maintained doing,
Apnea detection system.
10. The method of claim 9,
The apnea determining unit,
The change amount (L _previous ) of the signal strength in the first time interval between the abnormal respiration detection time point ( T ₁ ) and the abnormal respiration entry time point ( T ₂ ) corresponding to a predetermined time ( T ) prior therefrom is the apnea maintenance criterion Set as the amount of change in signal strength ( L _{reference ),}
When the change amount (L _nobreathing ) of the signal strength in the same time interval as the first time interval after the abnormal respiration detection time point ( T ₁ ) exceeds a certain level of the change amount (L _reference ) of the apnea maintenance reference signal strength, the determining that the subject's apnea has ceased;
When the change amount (L _nobreathing ) of the signal strength in the same time interval as the first time interval after the abnormal respiration detection time point ( T ₁ ) is less than a certain level of the change amount (L _reference ) of the apnea maintenance reference signal strength, the measurement target determined that apnea is maintained,
Apnea detection system.
According to claim 1,
When the apnea of the measurement target is detected by the apnea determining unit, further comprising an apnea warning unit for generating an apnea warning alarm,
Apnea detection system.
According to claim 1,
Further comprising a respiration rate calculating unit for calculating the time-axis-based respiration rate (f ₁ ) of the measurement target from the radio signal determined as normal respiration in the normal respiration determination unit,
Apnea detection system.

Images