JP5131657B2 - Respiration monitoring method and apparatus - Google Patents

Description

  The present invention relates to a respiratory monitoring method for simultaneously monitoring non-contact and unrestrained breathing of a subject such as a plurality of patients in an intensive care unit using an ultra wide band (UWB wave). Relating to the device.

  UWB waves such as UWB-IR (Ultra Wide Band-Impulse Radio) have a very short pulse width due to the use of a wide frequency band with a 10 dB relative bandwidth of 20% or more of the center frequency or 500 MHz or more, and the pulse resolution is high. Excellent multipath resistance. In addition, the power spectral density is as low as 10 nW / MHz because of its wide bandwidth, and it can coexist with other communication systems.

  On the other hand, in order to monitor a patient's breathing in a hospital room or an intensive care unit, a method is adopted in which an electrode is directly attached to the chest of the patient or a thermistor is attached to the mouth or nose. Such a sensor that requires contact or wiring has problems that cause discomfort to the patient, cause a sensor detachment accident due to a change in body posture, and hinder care / nursing.

  In addition, due to increasing social interest in apnea syndrome and the like, a pressure sensor is attached under the mat of the bed to monitor the breathing movement without restraint (for example, see Patent Document 1) or attached to the patient's bedside. A method of monitoring respiration using an image acquisition / processing device or a laser sensor has also been proposed. However, according to the method disclosed in Patent Document 1, it is difficult to detect subtle respiratory movements including low-frequency fluctuations due to body movements, and an image acquisition / processing device or a laser sensor is installed at the patient's bedside. The method of making it face cannot respond automatically to the position change of the patient due to body movement.

  Further, a method of detecting the movement of the subject by observing the Doppler effect and ranging using a microwave sensor (for example, see Patent Document 2 to Patent Document 6), or a weak radio with a narrow beam width for body movement. A detection method has also been proposed (see, for example, Patent Document 7). However, it is difficult to detect subtle human breathing in a harsh multipath environment such as indoors. Moreover, these conventional methods require a sensor and an attached device for each patient.

Japanese Patent Laid-Open No. 07-031592 JP 2000-083927 A Japanese Patent Application Laid-Open No. 2002-065677 JP 2002-071825 A JP-T-2001-525925 JP 07-059757 A JP 2002-058659 A

  The present invention simultaneously detects a respiratory motion of a plurality of subjects such as patients in a room at the same time without contact and without restraint, and displays a respiratory rate and abnormal breathing on a monitor monitor as necessary. It is an object of the present invention to provide a method for informing doctors and nurses via the device and a device therefor.

In order to solve the above-mentioned problem, the invention according to claim 1 transmits an ultra-wideband radio wave (UWB wave) toward a subject and sets a delay profile from a received signal of a reflected wave by a preamplifier / detector. After the A / D conversion of the delay profile, the signal processing unit observes each reflected wave as a time variation of the signal intensity, and performs a frequency analysis by a wavelet transform to cope with a sudden temporal change in the respiratory waveform. This is a respiratory monitoring method in which a path with a remarkable fluctuation width and periodicity is identified as a body movement caused by the subject's breathing, and the respiratory rate or abnormal breathing of the subject is detected. .

The invention according to claim 2 is an ultra-wideband radio wave oscillator, an ultra-wideband radio wave transmitting / receiving antenna, a preamplifier / detector for amplifying and detecting a received signal to obtain a delay profile, and digitizing the delay profile signal Outputs time variation of signal intensity for each reflected wave from the A / D converter and A / D converted delay profile, and performs frequency analysis by wavelet transform to cope with a sudden temporal change of the respiratory waveform A respiratory monitoring device having a signal processing unit.

  According to the present invention, the respiratory motion of a plurality of subjects can be detected simultaneously without contact and without restraint, and the respiratory rate or abnormal breathing can be known. In addition, the detection result is wirelessly transmitted to a distant monitoring monitor, and when an abnormal breathing is detected, an automatic alarm device is activated to promptly notify an emergency situation to a doctor or nurse.

  The present invention is a respiratory monitoring system that simultaneously detects a respiratory motion of a plurality of subjects in a room using an ultra-wideband radio wave (UWB wave) without contact and without restraint. FIG. 1 shows an outline of the respiratory monitoring system of the present invention. As shown in FIG. 1, for example, a UWB wave is transmitted toward a subject (patient or the like) P from a transmitting antenna 3 disposed on the ceiling of the room, and a reflected wave is received by the receiving antenna 3.

  FIG. 2 shows the configuration of the respiratory monitoring apparatus of the present invention. As shown in FIG. 2, the respiratory monitoring apparatus of the present invention includes a transmitter 1 composed of an ultra-wideband radio wave oscillator 2 and a transmitting / receiving antenna 3, a transmitting / receiving switch (hybrid) 4, and a received signal from the transmitting / receiving antenna 3. From the preamplifier / detector 6, A / D converter 7 and signal processor 8 for detecting the delay profile from the signal, and the respiratory waveform data obtained by the receiver 5 to the remote monitor It consists of a transfer antenna 9 for transmission.

  The transmission unit 1 includes an ultra-wideband radio wave oscillator 2 that oscillates an impulse-like monocycle wave, a stepped FM wave, an FM-CW wave, or a spread spectrum wave, and a transmitting / receiving antenna 3. On the other hand, the receiving unit 5 includes a receiving antenna 3, a preamplifier / detector 6, an A / D converter 7, and a digital signal processing unit 8.

  The UWB wave is transmitted from the transmitting antenna 3 toward the subject (patient or the like) P, and the delay profile detected from the received signal is A / D converted and then reflected by the signal processing unit 8 for each reflected wave (delay time). Is observed as a time fluctuation of the signal intensity, and the respiratory rate or respiratory abnormality of the subject (patient or the like) P is detected.

  The delay profile is a composite wave of delayed reflected waves from the subject and the obstacle. The delay profile is A / D converted, multipaths are separated and identified on the time or distance axis according to the bandwidth, and the signal strength of each path is input to the signal processing unit 8. FIG. 3 shows an example of the delay profile. The distance resolution of this delay profile is proportional to the transmission bandwidth. For example, at 5 GHz, a delay profile with a distance resolution of 6 cm can be obtained, and reflected waves with a path length difference of 6 cm or more can be separated and identified on the time axis. That is, if the path length difference from the antenna to each subject is 6 cm or more, the respiratory motion of a plurality of subjects can be detected simultaneously.

Next, each sample value of the A / D converted delay profile is observed for each transmission, and the periodicity is detected from the temporal change. For example, the reflected wave from the floor or a fixed object has almost no periodicity, but the signal strength is also high because the distance between the transmitting and receiving antenna and the transmitting and receiving antenna of the reflected wave from the subject fluctuates due to respiratory activity. Change (scintillation). In the present invention, the respiratory waveform is subjected to waveform analysis by wavelet transform in order to cope with sudden respiratory fluctuations.

  As described above, in the present invention, the respiratory rate is estimated not from the distance information but from the received signal intensity fluctuation (scintillation) accompanying the minute movement caused by the breathing of the subject P on the received delay profile. Therefore, by monitoring fluctuations in power at positions corresponding to the respective distances of the delay profile, the respiratory rate or abnormal breathing of the subject P can be detected.

The signal intensity of each delayed reflected wave (reflected wave having a different arrival time) is input to the signal processing unit 8 (for ultra-wideband radio waves such as stepped FM waves and FM-CW waves, after detection, each is subjected to inverse FFT (fast Fourier). transform) and FFT (transformed into the time domain and frequency domain), and the respiratory motion is estimated from the time variation. FIG. 4 shows the time variation (in the repetition period T of the transmission wave) of the signal intensity for each reflected wave in the delay profile. In FIG. 4, since S ₁ is a reflected wave from the floor surface, almost no periodicity is seen (only fluctuation due to noise), and it can be seen that this is a reflected wave from the fixed reflecting surface. S _{2 to} S ₆ periodically change due to respiratory motion, and are determined to be reflected waves from the human body, and the temporal change in the signal intensity is measured.

  In the present invention, human motion is not detected by observing the Doppler effect or ranging as in the conventional microwave sensor, but only the signal intensity fluctuation (scintillation) of each delayed reflected wave of the detected delay profile is detected. Used. Therefore, the load on the signal processing unit 8 and the A / D converter 7 is small and a low-cost respiration monitoring device can be provided. FIG. 5 shows the measured respiratory waveform. The respiratory waveform shown in FIG. 5 displays a section where the subject P intentionally stopped breathing. FIG. 5 also shows an actual respiratory waveform measured by attaching a conventional physical sensor (wire sensor) to the body.

  In the signal processing unit 8, frequency analysis is performed by wavelet transform in order to cope with a sudden temporal change in the respiratory waveform. FIGS. 6A and 6B show temporal changes (scalogram) of the frequency / respiration rate processed by the wavelet transform. Fig. 6-1 shows the continuous signal intensity waveform and its frequency / respiration rate over time, and Fig. 6-2 shows the signal intensity waveform and its frequency / respiration rate over time when breathing stops halfway. Show. Here, even when breathing is stopped, a slight change is observed, because the body slightly changes even when breathing is stopped.

According to the present invention, the respiratory movements of a plurality of subjects P can be monitored simultaneously. FIG. 7 shows respiratory waveforms of two subjects P measured simultaneously. FIG. 8 shows a signal intensity waveform that accompanies a sudden change in body position (from supine to prone). As is clear from FIG. 8, the respiratory motion can be accurately measured even for a sudden change in body position.
Further, if necessary, the respiratory waveform data and respiratory rates of a plurality of subjects P can be transmitted wirelessly to a distant monitoring monitor, and an automatic alarm device can be activated in the case of respiratory abnormalities.

  The transmitter / receiver antenna (Schwarzbeck: 9120D) near the ceiling (height: 2.8 m) shown in Fig. 1 is installed, and the delay of the radio transmission line is made using the time domain function of the vector network analyzer (Agilent: 8722ET). The profile was measured, and the result was transferred to a PC for signal processing. Here, a folding bed of a metal frame was used as the bed of the subject P. The floor is flooring.

The frequency bandwidth (BW (band width)) of UWB used for detection is 7 GHz (3 GHz to 10 GHz), and a window function is applied to the signal spectrum from the viewpoint of range sidelobe suppression (sidelobe ratio = −43 dB). The 6 dB pulse width Δd is given by the following equation.

Here, c is the speed of light, and c = 3 × 10 ¹⁰ [cm / s]. Therefore, the resolution Δd at BW = 7 GHz is about 8.4 cm.

FIG. 5 shows the reflected wave signal intensity fluctuation (period T = 0.74 msec) from the subject P lying on his / her back on the bed and the breathing of the subject P measured by winding a band-shaped wire sensor around the chest. The physical fluctuations associated with are shown. Here, the subject P stops breathing for a certain time. As is clear from FIG. 5, signal intensity fluctuations (respiration rate) of 11 times / minute to 16 times / minute are seen through the clothes of the subject P. In addition, small fluctuations at a relatively low frequency are seen, because the body moved slightly.

Schematic showing a respiratory monitoring system according to an embodiment of the present invention. The block diagram which shows the structure of the respiration monitoring apparatus which concerns on one Example of this invention. The graph which shows the delay profile obtained by the respiration monitoring system concerning one example of the present invention. The graph which shows the time fluctuation of the signal strength for every reflected wave of the delay profile obtained by the respiration monitoring system concerning one example of the present invention. The graph which shows the respiration waveform of Examinee P obtained by the respiration monitoring system concerning one example of the present invention. The graph which shows the time change of the continuous signal strength waveform and its frequency / respiration rate in the respiration monitoring system concerning one example of the present invention. In the respiratory monitoring system which concerns on one Example of this invention, the graph which shows the time change of the signal strength waveform when the subject P stops breathing on the way, and its frequency / respiration rate The respiration monitoring system concerning one example of the present invention WHEREIN: The graph which shows two subject P respiration waveforms measured simultaneously In the respiratory monitoring system which concerns on one Example of this invention, The graph which shows the signal strength waveform accompanying the sudden posture change of the subject P

DESCRIPTION OF SYMBOLS 1 Transmitter 2 Long-band radio wave oscillator 3 Transmit / receive antenna 4 Transmit / receive switch (hybrid)
5 the receiving unit 6 preamplifier / detector 7 A / D converter 8 signal processing unit 9 transfers the antenna P examinee _S 1 to S ₆ received signal

Claims (2)

An ultra-wideband radio wave (UWB wave) is transmitted to a subject, a delay profile is obtained from a reflected wave reception signal by a preamplifier / detector, and the delay profile is A / D converted, and then a signal processing unit In order to detect the respiratory rate or abnormal breathing of the subject by performing frequency analysis by wavelet transform in order to respond to the sudden temporal change of the respiratory waveform while observing the signal intensity as a time fluctuation for each reflected wave A respiratory monitoring method characterized by that. An ultra-wideband radio wave oscillator, an ultra-wideband radio wave transmitting / receiving antenna, a preamplifier / detector for amplifying and detecting a received signal of a reflected wave to obtain a delay profile, and an A / D converter for digitizing the delay profile signal A signal processing unit that outputs a time variation of the signal intensity for each reflected wave from the A / D converted delay profile and performs a frequency analysis by wavelet transform in order to cope with a sudden temporal change of the respiratory waveform A respiratory monitoring device characterized by that.

Images