JPH034209B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention detects respiration rate, heart rate, or both in a non-contact manner based on body surface displacement without attaching electrodes or the like to the subject. The present invention relates to a non-contact body surface displacement detection device.

[Problems to be solved by conventional technology and invention]

In clinical practice, it is important to monitor respiratory rate or heart rate over a long period of time during surgery or with a device such as a CCU. It is also important for constant monitoring of the respiratory and circulatory systems of premature infants, and for screening for sudden death syndrome, which has recently become the largest cause of perinatal death.

A typical measurement method for this purpose is a contact method in which an electrode or transducer is attached to the subject and a lead wire is led out. In this case, the lead wires may interfere with nursing care.
Moreover, the burden on the examinee is large.

Therefore, recently, as a non-contact measurement method,
It is well known to irradiate the body surface with ultrasonic waves and detect respiratory waves or heartbeat waves as body surface displacement from the phase change of the reflected signal detected by a microphone.
However, this method has the problem that high-precision measurement is difficult due to noise caused by air fluctuations and interference of reflected waves caused by non-uniform movement of the body surface. In addition, a method of irradiating microwaves is well known, but similarly, errors occur due to interference of reflected waves due to non-uniform movement, and installation becomes complicated.

Therefore, it is an object of the present invention to provide a body surface displacement detection device that measures respiration rate or heartbeat rate with high accuracy using a non-contact type and simple configuration.

[Means for solving problems]

In order to achieve this object, the present invention includes a light source 2 that repeatedly irradiates a pulsed light beam onto the body surface 1 of a subject, and a light spot that makes the reflected scattered light incident through a condensing lens 4. An optical spot position sensor 10 that detects the position, a synchronous detection circuit 9 that converts the detection signal of this sensor into a continuous wave signal by holding it in synchronization with each pulse, and a body detection signal that is detected from the synchronous detection signal of this sensor. Body surface displacement waveform detection circuits 14 and 17 that detect surface displacement waveforms
and body surface displacement frequency counting circuits 20 and 25 that count the body surface displacement waveform for a predetermined time.

Note that the symbols in parentheses refer to those in the embodiment described later.

[Effect]

The scattered light of the light beam reflected by the body surface 1 of the abdomen, chest, or back of the subject is condensed and enters the light spot position sensor 10 in a pulsed manner as a light spot. The incident position of this light spot changes as the reflection position of the light beam changes in accordance with body surface displacement due to respiration or heartbeat. By holding the detection signal synchronously,
The optical spot position sensor 10 outputs a continuous wave detection signal corresponding to its displacement. The body surface displacement waveform detection circuits 14 and 17 detect a desired noise-free body surface displacement waveform from this synchronously detected detection signal, and send the output signal to the body surface displacement frequency counting circuits 20 and 25 for a predetermined period of time. Let them count.

[Embodiments of the invention]

1 to 4 show an embodiment of the present invention. In FIG. 1, a pulse 2 with a period of 2 ms and a pulse width of 100 μs is supplied from the clock control unit 5, and a pulse with a peak value of about 2 mW is supplied. It is a laser light source that emits a light beam of a shape, and irradiates the chest 1 with light from a position 10 cm away, for example, through a focus lens 3 with a focal length of 5 cm, for example. The reflected and scattered light is condensed into a spot through the condenser lens 4, and is incident on the optical spot position sensor 10. This sensor consists of a well-known semiconductor position sensing device (PSD) 11, which has two pairs of electrodes arranged at symmetrical positions, each outputting a photocurrent according to the displacement in the X and Y axis directions from the center position. , for example, an I/V conversion circuit 12 that converts the photocurrent at a pair of terminals Y and Y' in the Y-axis direction into a voltage signal, and an I/V conversion circuit 12 that converts the photocurrent at a pair of terminals Y and Y' in the Y-axis direction into a voltage signal, and converts the voltage signal at both terminals into a voltage signal corresponding to the incident position of the light spot. It is comprised of a correction circuit 13 that converts into a position signal whose voltage level changes.

Between this correction circuit and the I/V conversion circuit 12,
By intervening the synchronous detection circuit 9, the 100 μs wide output signal of the Y, Y' terminals generated every 2 ms from the I/V conversion circuit 12 is held until the next optical pulse is generated, and a continuous wave output signal is generated. The correction circuit 13
supply to. These optical systems 2 to 4, 11 are mounted, for example, on a stand, and irradiate light through a transparent case to a premature baby in the incubator or directly to an adult baby.

Reference numeral 14 denotes a respiratory wave detection circuit, which includes a bandpass filter 15 with a pass band of 0.08 to 2 Hz to remove noise included in the output signal of the correction circuit 13, and detects respiratory waves from the signal input through this filter. The main body 16 is a respiratory wave detection circuit. This circuit body is constituted by, for example, the circuit shown in FIG. 3, which is well known per se. 17 is a heartbeat wave detection circuit, which also has a passband of 10 to 20Hz in order to remove noise included in the output signal of the correction circuit 13.
It is composed of a bandpass filter 18 and a waveform shaping circuit 19 that pulses its output signal.

20 is a respiration rate counting circuit that counts the respiration rate for a predetermined time, and is composed of a counter 21 that counts the output signal of the respiratory wave detection circuit main body 16, and a data holding circuit 22 that holds the counted value.
By sharing the clock control section 5, the counter 21 is reset and the data holding circuit 22 is latched using a clock generated at predetermined time intervals. 25 is a heart rate counting circuit that counts the heart rate for a predetermined time;
and a data holding circuit 27 that holds the counted value, and a clock control section 5.
are shared.

28 is a display unit that displays the respiration rate and heart rate data held in the data holding circuits 22 and 27; 29;
is the recording section that performs the recording.

The operation of the body surface displacement detection device configured as described above is as follows.

The chest 1 is irradiated with a well-converged light beam from a laser light source 2 through a focus lens 3 at intervals of 2 ms. The incident light beam is scattered by the chest 1, and the reflected and scattered light is converged by the condenser lens 4 and enters the PSD 11. As a result, PSD1
From 1, it corresponds to the displacement of the incident position of the light spot due to chest wall breathing and heartbeat, and compared to continuous light irradiation, the influence of indoor illumination light and ambient light is reduced by the increase in pulse peak value. The current signal is Y,
The signal is output from the Y' terminal and converted into a pulse-like voltage signal by the I/V conversion circuit 12. As shown in FIG. 2, the synchronous detection circuit 9 synchronizes and holds both input signals shown by the solid line with a clock pulse synchronized with the optical pulse from the clock control section 5, thereby generating a continuous waveform shown by the dotted line. Convert to signal. Therefore, the correction circuit 13 outputs one continuous wave signal whose voltage level changes according to the displacement of the chest wall.

The output signal of the correction circuit 13 inputted to the respiratory wave detection circuit 14 has heartbeat components etc. reduced in the bandpass filter 15, and is supplied as an input signal V1 to the respiratory wave detection circuit main body 16 shown in FIG.

In the same figure, A1 and A2 are operational amplifiers, A3
is a comparator, and A4 is an inverter. Analog switch SW1 and diode D that are turned on when output signal V5 of comparator A3 is “1”
1 and capacitor C1 constitute a peak hold circuit, and analog switch SW2, which is turned on when output signal V5 is "0", diode D2 and capacitor C1 constitute a bottom hold circuit. The operation is well known, but to explain period A, it is assumed that just before that period, as shown in FIG. 4, the output signal V5 of comparator A3 had become "1" and peak detection was being performed. Inverted signal V2 obtained by inverting input signal V1 by operational amplifier A1
is divided by resistors R3 and R4, and the operational amplifier A2
and its peak value is input to comparator A3 -
This becomes the input signal V4. Since the +input signal V3 of the comparator A3 is inputted after the inverted signal V2 and the output signal V5 are divided by the resistors R6 and R7, the comparator A3 is inverted due to the fall of the inverted signal V2, and the output signal V5 is "0". "become. As a result, the analog switch SW2 is turned on and bottom detection is performed. +input signal V3 of comparator A3
In this case, the inverted signal V2 and the output signal V5 are connected to the resistor R6,
The voltage is divided at R7 and is at the bottom level - below the input signal. When the inverted signal V2 rises, the comparator A3 is inverted and the output signal V5 becomes "1" again.
become. As a result, comparator A3 outputs output signal V5, which is a logic signal corresponding to the respiratory wave cycle.
is output.

Similarly, the output signal of the correction circuit 13 is also input to the heartbeat wave detection circuit 17, and a bandpass filter 18 removes noise such as respiratory wave components to detect only the heartbeat wave. converted into corresponding pulses.

The clock control unit 5 generates a clock every minute, causes the counters 21 and 26 to count the respiratory wave signal and the heartbeat wave signal, and causes the data holding circuits 22 and 27 to count the respiratory rate and heartbeat wave signal updated every minute. Retain heart rate data. The display section 28 numerically displays the breathing rate and heart rate, and the recording section 29 continuously records them on recording paper.

In the above embodiment, the synchronous detection circuit 9 can be placed after the correction circuit 13. circuit portions 14-16, 21-22 or circuit portion 17,
25, it is also possible to configure the device as only a heart rate detection device or a respiration rate detection device. As the optical spot position sensor 10, a CCD
The displacement of the light spot position on the imaging surface may be detected by using an image sensor such as a mold or the like and reading and scanning the imaging surface. It is also conceivable that the readout scan of the image sensor is stepped in synchronization with the pulsed light irradiation so that the synchronous detection circuit can also be used. It is also conceivable to use an LED as the light source of the light beam.

〔Effect of the invention〕

As described above, by detecting the displacement of the reflected light spot in response to body surface displacement according to the present invention, all the advantages of the non-contact type can be maintained, and since it is an optical type, the spot diameter can be easily reduced. , Therefore, compared to ultrasound and microwaves, there is less interference and measurement accuracy is improved. Similarly, since the spot diameter can be made small, even if the person is wearing clothes and the surface shape is irregular, interference is unlikely to occur, so body surface displacement can be reliably detected even through the clothes. Furthermore, since light is used, the problem of interference with peripheral devices is eliminated. Furthermore, even if the peak power is increased by pulsed light beam irradiation, the average value of the optical output can be reduced, increasing patient safety.
By synchronously detecting the incident light signal, the S/N ratio for disturbance light is higher than that of continuous light beam irradiation.
The ratio also improves.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of the optical system and attached circuits of a non-contact body surface displacement detection device according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of the synchronous detection circuit of the embodiment, and Fig. 3 4 is a diagram illustrating the circuit configuration of the respiratory wave detection circuit main body of the same embodiment, and FIG. 4 is a diagram illustrating the voltage relationship of each part in FIG. 3. 1...Chest, 4...Condensing lens.

Claims (1)

[Claims] 1. A light source that repeatedly irradiates the subject's body surface with a pulsed light beam, a light spot position sensor that detects the position of the light spot formed by passing the reflected scattered light through a condensing lens, and detection of this sensor. a synchronous detection circuit that converts the signal into a continuous wave signal by holding the signal in synchronization with each of the pulses; a body surface displacement waveform detection circuit that detects a body surface displacement waveform from the converted detection signal; A non-contact body surface displacement detection device comprising: a body surface displacement frequency counting circuit that counts output signals of the body surface displacement waveform detection circuit.