Automated external defibrillator

Abstract

An automatic external defibrillator (AED) according to the present invention comprises: a power supply unit (19); a high-voltage generation unit (16) that boosts a voltage applied from the power supply unit (19) to generate a high-voltage pulse; and a pair of electrodes (30A, 30B) that impart an electric shock based on the high-voltage pulse to a person to be treated. The high voltage generation unit (16) comprises: a full bridge inverter circuit (161) that converts a DC voltage applied from the power supply unit (19) into an AC voltage; a transformer (163) that boosts the converted AC voltage; and a first driver (162). A control unit (14) transmits a pulse width modulation (PWM) signal to the first driver (162), controls the full-bridge inverter circuit (161) by PWM, and changes the output voltage of the full-bridge inverter circuit (161) in a time series in accordance with a set waveform.

Description

automated external defibrillator

[0001] The present disclosure relates to automated external defibrillators.

[0002] Automated external defibrillators (AEDs) are widely used as defibrillators that deliver a high-voltage pulse of electric shock to the recipient's spasming heart, thereby stimulating normal heartbeat. Conventional AEDs are relatively large devices and are often installed in stations, public facilities, commercial facilities, etc., making them difficult to carry around.

[0003] A known technology for miniaturizing AEDs is described in Patent Document 1. The AED described in Patent Document 1 generates a high-voltage pulse by boosting the output voltage of a power supply unit using a transformer. The AED described in Patent Document 1 can be miniaturized because it does not require a high-voltage, large-capacity capacitor.

[0004] Japanese Patent Application Laid-Open No. 2022-182010

[0005] The AED described in Patent Document 1 uses a simple mechanism in which a single switch provided between the power supply unit and the transformer is turned on and off to supply power to the transformer. Therefore, the AED described in Patent Document 1 has difficulty generating high-voltage pulses with complex waveforms suitable for defibrillation, which can be generated by conventional AEDs.

[0006] The present disclosure has been made in consideration of the above-described circumstances, and has an object to provide a small-sized automatic external defibrillator capable of generating high-voltage pulses suitable for defibrillation.

[0007] In order to achieve the above object, the automatic external defibrillator according to the present disclosure comprises: an inverter circuit that converts a DC voltage into an AC voltage by performing a switching operation with a duty ratio according to a switching control signal; a transformer that boosts the AC voltage converted by the inverter circuit; a rectifier circuit that rectifies the voltage boosted by the transformer; electrodes that apply an electric shock to a recipient based on the output voltage of the rectifier circuit; and duty ratio control means that supplies the switching control signal to the inverter circuit and controls the amount of electric energy supplied from the inverter circuit to the transformer.

[0008] Furthermore, a memory unit may be provided for storing data representing changes in the duty ratio over time in accordance with the voltage waveform of the electric shock to be applied to the recipient, in which case the duty ratio control means controls the duty ratio of the switching operation of the inverter circuit, for example, in accordance with the data stored in the memory unit.

[0009] The memory unit may store data representing changes in duty ratio over time corresponding to a plurality of voltage waveforms of an electric shock to be applied to the rescuee. In this case, the rescue device may further include a selection unit for selecting one of the plurality of voltage waveforms. The duty ratio control unit controls the duty ratio of the inverter circuit in accordance with the data corresponding to the voltage waveform selected by the selection unit.

[0010] The device may include a measuring means for measuring the impedance between the electrodes attached to the recipient, a means for storing the basic waveform of the applied voltage, and a means for correcting the basic waveform based on the impedance measured by the measuring means, and for generating data indicating the change in duty ratio over time based on the corrected waveform.

[0011] The device may further comprise means for updating the data indicating the change in duty ratio with respect to time stored in the storage unit.

[0012] The device may further include a polarity reversal circuit that applies the output voltage of the rectifier circuit to the electrode in the forward or reverse direction in accordance with a polarity control signal, and a polarity control means that sends the polarity control signal to the polarity reversal circuit to apply to the electrode a voltage of a polarity corresponding to the voltage waveform of the electric shock to be applied.

[0013] The device may further include a memory unit that stores data indicating the polarity of the applied voltage corresponding to the voltage waveform of the electric shock to be applied to the recipient. In this case, the polarity control means controls the polarity reversal circuit in accordance with the data stored in the memory unit.

[0014] The power supply may further include a smoothing circuit that smoothes the voltage output from the rectifier circuit.

[0015] The duty ratio control means may generate a plurality of voltage pulses by driving the inverter circuit a plurality of times at predetermined time intervals.

[0016] The electrodes may be needle-shaped, pad-shaped, or scissors-shaped and may be attached to the person being rescued.

[0017] According to the present disclosure, it is possible to realize miniaturization and easily generate high-voltage pulses with complex waveforms.

[0018] 10 is a diagram showing an example of the appearance of an AED according to an embodiment of the present disclosure. FIG. 11 is a diagram showing an example of the attachment position of electrodes of an AED according to an embodiment of the present disclosure. FIG. 12 is a circuit block diagram of an AED according to an embodiment of the present disclosure. (A) to (C) are diagrams showing an example of the waveform of a high-voltage pulse that can be applied by an AED according to an embodiment of the present disclosure. FIG. 13 is a diagram showing an example of the circuit configuration of a high-voltage generation unit shown in FIG. 3. FIG. 14 is a timing chart for explaining the operation of a full-bridge inverter circuit shown in FIG. 5. FIG. 15 is a diagram showing an example of the circuit configuration of a first driver shown in FIG. 5. FIG. 16 is a diagram showing an example of the functional configuration of a storage unit shown in FIG. 3. FIG. 17 is a timing chart for explaining the operation of the high-voltage generation unit shown in FIG. 5. FIG. 18 is a flowchart showing details of the waveform table generation process shown in FIG. 10. FIG. 19 is a diagram showing an example of the waveform of a high-voltage pulse in a dual shock mode of an AED according to an embodiment of the present disclosure. FIG. 19 is a flowchart for explaining an example of the operation of an AED in a dual shock mode of an AED according to an embodiment of the present disclosure. FIG. 19 is a diagram showing an example of the appearance of an AED according to a modified example. FIG. 19 is a diagram showing an example of the electrode structure of an AED according to a modified example.

[0019] An automated external defibrillator according to an embodiment of the present disclosure will be described in detail below with reference to the drawings. Note that identical or corresponding parts in the drawings are designated by the same reference numerals. In the following description, the automated external defibrillator will also be referred to as an AED (Automated External Defibrillator).

[0020] 1 is a diagram illustrating an example of the appearance of an AED 1 according to an embodiment of the present disclosure. The AED 1 includes a main body 10, a pair of electrodes 30A and 30B, and cables 40A and 40B that electrically connect the main body 10 to the electrodes 30A and 30B, respectively.

[0021] When using the AED 1, the electrodes 30A and 30B are inserted near the right chest and flank of the recipient, respectively, as shown in Fig. 2 . The positions of the electrodes 30A and 30B are not limited to the example shown in Fig. 2 , and may be any positions that form a pair with respect to the heart, i.e., positions that allow an electric shock to be administered to the heart. Specifically, the electrodes 30A and 30B are inserted at any positions that allow a current generated by a high-voltage pulse to pass from one of the electrodes 30A and 30B through the heart and reach the other. For example, inserting the electrodes 30A and 30B on the left and right shoulders can reduce individual differences.

[0022] Returning to Fig. 1, the main body 10 of the AED 1 has an easily portable shape and size similar to, for example, a mobile terminal, tablet, etc. A display unit 11 and an operation unit 12 are provided on the surface of the main body 10. The display unit 11 includes, for example, a liquid crystal display and its drive circuit. The display unit 11 displays information indicating the operation status of the AED 1, the waveform of the high-voltage pulse to be applied, the operation mode, etc.

[0023] The operation unit 12 includes an operation knob 12 a and a button group 12 b. The button group 12 b includes various operation buttons such as a power button, a voltage application button for instructing the rescuee to apply a high-voltage pulse, a waveform selection button for selecting the waveform of the high-voltage pulse to be applied, and a mode selection button for selecting an operation mode.

[0024] As shown in FIG. 3, the main body 10 of the AED 1 includes the display unit 11 and operation unit 12 described above, as well as a memory unit 13, a control unit 14, a communication unit 15, a high-voltage generation unit 16, an electrocardiogram signal acquisition unit 17, a state detection unit 18, a power supply unit 19, and an audio output unit 20.

[0025] The power supply unit 19 includes a DC power supply with an output voltage V1 of approximately 100 to 110 V. This DC power supply is configured, for example, by connecting a plurality of semi-solid lithium batteries in series. The power supply unit 19 supplies DC power to the high voltage generation unit 16. Although not shown in FIG. 3, the power supply unit 19 is also connected to various components other than the high voltage generation unit 16 and supplies operating power to these components.

[0026] The high-voltage generator 16, under the control of the controller 14, boosts the output voltage of the power supply 19 and adjusts the boosted voltage to generate a high-voltage pulse (more specifically, a potential difference between the electrodes 30A and 30B) between the electrodes 30A and 30B to be applied to the recipient. This high-voltage pulse has a waveform suitable for defibrillation. In this embodiment, the operator operates the operation unit 12 to select the waveform of the high-voltage pulse to be generated from among the monophasic waveform shown in FIG. 4A, the biphasic BTE waveform shown in FIG. 4B, and the RLB waveform shown in FIG. 4C. In the following description, the waveform of the high-voltage pulse currently set to be applied will also be referred to as the "set waveform."

[0027] An example of the circuit configuration of the high voltage generation unit 16 is shown in Fig. 5. Note that Fig. 5 shows only the main circuit configuration, and ground connections and the like are omitted as appropriate. The high voltage generation unit 16 includes a full-bridge inverter circuit 161, a first driver 162, a transformer 163, a rectifying and smoothing circuit 164, a polarity reversing circuit 165, and a second driver 166.

[0028] The full-bridge inverter circuit 161 includes four switching elements Q1 to Q4 that form the four sides of a bridge circuit. Each of the switching elements Q1 to Q4 is configured with a MOSFET, an IGBT, or the like. In the following description, it is assumed that the switching elements Q1 to Q4 are configured with an N-channel MOSFET. One end (drain) of the current path of each of the switching elements Q1 and Q3 is connected to the positive terminal of the power supply unit 19. One end (source) of the current path of each of the switching elements Q2 and Q4 is connected to the negative terminal of the power supply unit 19. A connection node N1 between the other end (source) of the current path of the switching element Q1 and the other end (drain) of the current path of the switching element Q2 is connected to one end of a primary winding 163a of a transformer 163. A connection node N2 between the other end (source) of the current path of the switching element Q2 and the other end (drain) of the current path of the switching element Q4 is connected to the other end of the primary winding 163a of the transformer 163.

[0029] A switching control signal S1 is applied from the first driver 162 to the gates of the switching elements Q1 and Q4, and a switching control signal S2 is applied from the first driver 162 to the gates of the switching elements Q2 and Q3.

[0030] The switching elements Q1 and Q4 are turned on when the switching control signal S1 is at a high level. At this time, current flows from the positive terminal of the power supply unit 19 to the switching element Q1 to the connection node N1 to the primary winding 163a of the transformer 163 to the connection node N2 to the switching element Q4 to the negative terminal of the power supply unit 19. On the other hand, the switching elements Q2 and Q3 are turned on when the switching control signal S2 is at a high level. At this time, current flows from the positive terminal of the power supply unit 19 to the switching element Q3 to the connection node N2 to the primary winding 163a of the transformer 163 to the connection node N1 to the switching element Q2 to the negative terminal of the power supply unit 19.

[0031] As shown in Figures 6(A) and 6(B), by repeating the process of alternately setting the switching control signals S1 and S2 to high level, the set of switching elements Q1 and Q4 and the set of switching elements Q2 and Q3 are alternately turned on repeatedly. As a result, as shown in Figure 6(C), an AC voltage is applied to the primary winding 163a of the transformer 163. The voltage applied to the primary winding 163a is approximately -V1 to +V1. As a result, as shown in Figure 6(D), an AC primary current I in The primary current I in The effective value of is determined by the ratio of the on-period PW1 or PW2 to the on-off cycle λ of the switching elements Q1 to Q4, i.e., the duty ratios (PW1 / λ) and (PW2 / λ). ​​Therefore, by adjusting the duty ratios (PW1 / λ) and (PW2 / λ), that is, by PWM-controlling the switching operations of the switching elements Q1 to Q4, the amount of electrical energy supplied to the transformer 163 can be adjusted. Note that the on-period PW1 of the pair of switching elements Q1 and Q4 and the on-period PW2 of the pair of switching elements Q2 and Q3 may be the same or different.

[0032] A large pulsed momentary current flows through the switching elements Q1 to Q4, so it is desirable to use a large Si-MOSFET that can tolerate a pulsed momentary current of, for example, about 300 A and is capable of high-speed switching.

[0033] The transformer 163 shown in Fig. 5 includes a primary winding 163a and a secondary winding 163b. The primary winding 163a and the secondary winding 163b are wound around a core (iron core) made of ferrite or the like. One end of the primary winding 163a is connected to a connection node N1 of the full-bridge inverter circuit 161, and the other end of the primary winding 163a is connected to a connection node N2. One end of the secondary winding 163b is connected to an output terminal T1 of the transformer 163, and the other end of the secondary winding 163b is connected to an output terminal T2 of the transformer 163.

[0034] The number of turns of the primary winding 163a is relatively small, for example, about 10, and the number of turns of the secondary winding 163b is preferably about 100 to 200. In this case, the turn ratio NR between the primary winding 163a and the secondary winding 163b is 1:10 to 1:20. In this example, the number of turns of the primary winding 163a is 10, the number of turns of the secondary winding 163b is 138, and the turn ratio NR is 13.8. Furthermore, it is desirable to use low-loss Litz wire for the secondary winding 163b, and to make the winding thick. This allows, for example, the resistance of the primary winding 163a to be about 0.025 Ω and the resistance of the secondary winding 163b to be about 1.93 Ω, thereby keeping the impedance of the transformer 163 to 3 Ω or less, which is sufficiently small, less than 1 / 10 of the bioimpedance (50 to 1000 Ω).

[0035] The rectifying and smoothing circuit 164 includes a full-wave rectifying circuit 164a made up of diodes D1 to D4, which are rectifying elements, and a smoothing capacitor C1 that forms a smoothing circuit.

[0036] The input terminal of the full-wave rectifier circuit 164a is connected to the output terminals T1 and T2 of the transformer 163, and the voltage between the output terminals T1 and T2 is full-wave rectified, and the pulsating voltage is applied between the positive terminal T3 and the negative terminal T4 of the smoothing capacitor C1. The diodes D1 to D4 are preferably SiC Schottky diodes that can tolerate large currents and high-frequency switching operations. Furthermore, to ensure a sufficient withstand voltage, multiple diode elements may be connected in series and used as the diodes D1 to D4.

[0037] The smoothing capacitor C1 smoothes the pulsating voltage after full-wave rectification applied between the positive terminal T3 and the negative terminal T4. The smoothing capacitor C1 is preferably one with a high withstand voltage and a relatively small capacity. For example, a withstand voltage of 1,600 V and a capacity of approximately 12 μF is desirable. The smoothing capacitor C1 can suppress pulsations in the output voltage. However, it is also possible to perform rectification only by the full-wave rectifier circuit 164a without providing the smoothing capacitor C1.

[0038] For example, if the output voltage of the power supply unit 19 is 110 V and the turns ratio NR of the transformer 163 is 13.8, the voltage V2 between the positive terminal T3 and the negative terminal T4 will vary depending on the duty ratio but will be approximately 1500 V at most, ensuring a voltage sufficient for use as a high-voltage pulse for the AED 1. It is possible to obtain a higher voltage by adjusting the power supply voltage V1 and the turns ratio NR.

[0039] The polarity reversing circuit 165 is a circuit that applies the voltage V2 output by the rectifying and smoothing circuit 164 between the electrodes 30A and 30B in either a forward or reverse direction. The polarity reversing circuit 165 has a configuration similar to that of the full-bridge inverter circuit 161, and includes four switching elements Q5 to Q8 that form the four sides of the full-bridge circuit. The switching elements Q5 to Q8 are each composed of an N-channel MOSFET, an IGBT, or the like, made of SiC for large currents. In the following description, they are referred to as MOSFETs.

[0040] One end of the current path of switching elements Q5 and Q7 is connected to the positive terminal T3 of rectifying and smoothing circuit 164. One end of the current path of switching elements Q6 and Q8 is connected to the negative terminal T4 of rectifying and smoothing circuit 164. A connection node N3 between the other end of the current path of switching element Q5 and the other end of the current path of switching element Q6 is connected to electrode 30A via cable 40A. A connection node N4 between the other end of the current path of switching element Q7 and the other end of the current path of switching element Q8 is connected to electrode 30B via cable 40B. As a result, voltage V2 or a voltage of the opposite polarity -V2 is applied between electrodes 30A and 30B, resulting in a high-voltage pulse Vout that delivers an electric shock.

[0041] The first driver 162 is a drive circuit that controls the on / off of the switching elements Q1 to Q4 of the full-bridge inverter circuit 161. The first driver 162 controls the period λ and pulse widths PW1 and PW2 of the switching control signals S1 and S2 shown in FIGS. 6A and 6B in accordance with the PWM control signal supplied from the control unit 14. In other words, the first driver 162 controls the duty ratio of the switching operation of the full-bridge inverter circuit 161.

[0042] FIG. 7 shows an example of the configuration of the first driver 162. In the illustrated example, the first driver 162 includes an oscillator circuit 1621 and a frequency divider circuit 1622 including multiple counters. The oscillator circuit 1621 includes, for example, a vibrator and outputs a clock signal of approximately 1 MHz. The frequency divider circuit 1622 counts the number of clock pulses of the clock signal output from the oscillator circuit 1621 in accordance with the PWM control signal to measure the period λ shown in FIG. 6. Within each period λ, the frequency divider circuit 1622 measures the initial timing at which the switching control signals S1 and S2 are set to a high level, and further measures the pulse widths PW1 and PW2 to output the switching control signals S1 and S2. As a result, the period λ and pulse widths PW1 and PW2 of the switching control signals S1 and S2 are controlled in units of one clock (1 μS). The period λ and pulse widths PW1 and PW2 are updated and set in the frequency divider circuit 1622 as needed by the PWM control signal. As a result, the full-bridge inverter circuit 161 is PWM-controlled, and the amount of electrical energy supplied from the full-bridge inverter circuit 161 to the transformer 163 is controlled.

[0043] The second driver 166 is a drive circuit that controls the on / off of the switching elements Q5 to Q8 of the polarity reversal circuit 165. More specifically, the second driver 166 responds to a polarity control signal from the control unit 14, and, for example, when a positive voltage is applied to the electrode 30A and a negative voltage is applied to the electrode 30B, as in the applied voltages in FIG. 4A and the first half of the applied voltages in FIGS. 4B and 4C, the second driver 166 sets the switching control signal S3 to a high level to turn on the switching elements Q5 and Q8. On the other hand, when a negative voltage is applied to the electrode 30A and a positive voltage is applied to the electrode 30B, as in the second half of the applied voltages in FIGS. 4B and 4C, the second driver 166 sets the switching control signal S4 to a high level to turn on the switching elements Q6 and Q7.

[0044] The storage unit 13 shown in Fig. 3 includes a nonvolatile memory such as a read-only memory (ROM) and a volatile memory such as a random access memory (RAM). The nonvolatile memory stores control programs and fixed data executed by the control unit 14. The volatile memory is used by the control unit 14 as a work area when executing the control programs. The volatile memory also temporarily stores electrocardiogram signals and the like.

[0045] 8, a waveform memory area 131 is allocated in the storage unit 13. In the waveform memory area 131, a basic waveform table 132, a PWM control table 133, and a polarity control table 134 are stored.

[0046] The basic waveform table 132 is stored in a nonvolatile storage area of ​​the storage unit 13 and stores waveform data for basic waveforms of high-voltage pulses selectable by the AED 1, such as the voltage waveforms shown in Figures 4A to 4C. The waveform data for each basic waveform is designed so that the total energy applied to the recipient is a reference value Er when the impedance (biological impedance) between the electrodes 30A and 30B is a reference value Rr. The basic waveform table 132 is stored in a nonvolatile storage area. The bioimpedance Rb varies depending on the shape and placement of the electrodes, and is approximately 1000 Ω for needle-shaped electrodes 30A and 30B as shown in Figure 1, and approximately 20 Ω to 200 Ω for conventional pad-type electrodes (see Figure 14). Therefore, in this embodiment, the reference waveform is set with the reference value Rr of bioimpedance set to, for example, 1000 Ω.

[0047] The PWM control table 133 and the polarity control table 134 are tables generated by customizing the basic waveforms stored in the basic waveform table 132 for the rescue recipient. The PWM control table 133 and the polarity control table 134 are sometimes collectively referred to as a waveform table 135, meaning that they are tables that define the waveform of the high-voltage pulse to be applied.

[0048] More specifically, the PWM control table 133 stores the elapsed time t (i=0, 1, 2, . . .) in association with the period λ and pulse widths PW1 and PW2 at that time in order to control the switching control signals S1 and S2 supplied to the full-bridge inverter circuit 161 for the high-voltage pulses to be applied to the rescuee. In other words, it stores data indicating the duty ratio in the switching operation of the full-bridge inverter circuit 161 at the elapsed time t.

[0049] The polarity control table 134 stores the elapsed time ti and the polarity of the voltage to be applied at that time in association with each other in order to control the switching control signals S3 and S4 to be supplied to the polarity reversal circuit 165 for the high voltage pulse to be applied to the rescuee.

[0050] The waveform table 135 will be described in more detail. The bioimpedance Rb between the electrodes 30A and 30B varies depending on the shape of the electrodes, the position of the electrodes, and the like. Therefore, if the voltage Vi determined by the fundamental waveform is applied when the recipient's bioimpedance Rb is high, the applied energy may be insufficient. On the other hand, if the voltage Vi determined by the fundamental waveform is applied when the recipient's bioimpedance Rb is low, the applied energy may be excessive. For this reason, the state detection unit 18 measures the bioimpedance Rb between the electrodes 30A and 30B, and generates an applied waveform by adjusting the waveform of the fundamental waveform according to the magnitude of the recipient's bioimpedance Rb, so that the total energy E applied to the recipient matches the reference value Er.

[0051] The energy E applied to a living body is expressed as the product I·V of the applied voltage V and the current I. Also, I=V / R. Therefore, the applied energy E=V ２ / R. Therefore, if the impedance R is increased by a factor of k, approximately the same energy E can be applied by multiplying the voltage by √k. Alternatively, approximately the same energy E can be applied by multiplying the application time (duration) of the high voltage pulse by a factor of k.

[0052] In this embodiment, when the measured bioimpedance is Rb and the reference value of the bioimpedance is Rr, the voltage Vi of the basic waveform at the timing ti is corrected to √(Rb / Rr)·Vi to form an applied waveform and apply it to the rescuee.

[0053] The PWM control table 133 stores the period λ and pulse widths PW1 and PW2 required to generate the voltage √(Rb / Rr)·V at the timing of the elapsed time t. In other words, it stores the PWM control signal that indicates the duty ratio of the switching operation of the full-bridge inverter circuit 161 at the timing t.

[0054] Meanwhile, the polarity control table 134 stores data indicating the polarity of the voltage to be applied at the timing of the elapsed time ti. Note that data indicating a positive polarity instructs that the switching control signal S3 be set to a high level, and data indicating a negative polarity instructs that the switching control signal S4 be set to a high level.

[0055] The data stored in the PWM control table 133 and the polarity control table 134 will be explained based on a specific example. Here, it is assumed that the pulse voltage waveform to be applied is the BTE voltage shown in Fig. 4B. For ease of understanding, it is assumed that the period λ of the switching control signals S1 and S2 is constant.

[0056] An example of the basic voltage waveform Vr of the BTE voltage waveform is shown by the thin dashed line in Figure 9(A). Assume that the bioimpedance Rb / bioimpedance reference value Rr detected by the state detection unit 18 is 1.3. In this case, to apply the reference energy value Er to the recipient, a voltage waveform Va obtained by correcting the voltage of the basic voltage waveform Vr by 1.14≒√1.3 = √(Rb / Rr) times is applied to the recipient. The voltage waveform Va corrected by 1.14 times is shown by the thick solid line in Figure 9(A) (the figure has been exaggerated for clarity). The output voltage V2 = |Va| of the rectifying and smoothing circuit 164 when obtaining the voltage waveform Va is a positive voltage waveform as shown in Figure 9(B).

[0057] To obtain the voltage waveform |Va| shown in FIG. 9B, as shown in FIGS. 9C and 9D, the duty ratio of the switching operation of the full-bridge inverter circuit 161 is set at time T1 to obtain V2 = 1.14Vr. Thereafter, the duty ratio is gradually reduced between times T1 and T2 and between times T4 and T5 as the voltage of the basic voltage waveform Vr decreases. In other words, the period λ of the switching control signals S1 and S2 is kept constant, and the pulse widths PW1 and PW2 of the switching operation of the full-bridge inverter circuit 161 are appropriately set at time T1. Thereafter, the pulse widths PW1 and PW2 are gradually reduced. Note that FIGS. 9C and 9D are schematic diagrams illustrating the change in duty ratio over time and may differ from actual waveforms. For example, in reality, the switching control signals S1 and S2 are shifted in phase by π, as shown in FIGS. 6A and 6B.

[0058] The PWM control table 133 stores data in table format indicating the period λ and pulse widths PW1 and PW2, i.e., duty ratios, for each elapsed time ti from the start timing T0. The data format can be any format, such as a set of elapsed time ti, period λ, and pulse widths PW1 and PW2, a set of elapsed time ti and pulse widths PW1 and PW2 assuming that the period λ is fixed, or the elapsed time ti and the duty ratios of the switching control signals S1 and S2.

[0059] 9A, it is necessary to turn on switching elements Q5 and Q8 of polarity reversal circuit 165 so as to output a positive voltage between times T0 and T3, and to turn on switching elements Q6 and Q7 so as to output a negative voltage between times T3 and T6. For this reason, as shown in FIGS. 9E and 9F, switching control signal S3 is set to high level between times T0 and T3, and switching control signal S4 is set to high level between times T3 and T6. Polarity control table 134 stores data thus obtained indicating the polarity of the applied voltage at each elapsed time ti from start timing T0.

[0060] 3 includes a processor such as a CPU (Central Processing Unit), i.e., a computer. The control unit 14 may include a single computer or multiple computers. Furthermore, a portion of the control unit 14 may include hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

[0061] The control unit 14 operates in accordance with the control program stored in the memory unit 13, thereby controlling each of the display unit 11, operation unit 12, memory unit 13, communication unit 15, high voltage generation unit 16, electrocardiogram signal acquisition unit 17, status detection unit 18, and audio output unit 20, thereby performing electrocardiogram analysis, electric shock output control, etc.

[0062] The control unit 14 has a waveform control unit 141 as a functional configuration. The waveform control unit 141 has a DSP (Digital Signal Processor). When a waveform to be applied (a set waveform) is selected and the bioimpedance Rb is measured, the DSP calculates data for controlling the duty ratio of the switching operation of the full-bridge inverter circuit 161 and data for controlling the polarity reversal circuit 165, and stores the data in the PWM control table 133 and the polarity control table 134.

[0063] The waveform control unit 141 also references the data stored in the PWM control table 133 to generate a PWM control signal and supplies the generated PWM control signal to the first driver 162. In accordance with the PWM control signal, the first driver 162 alternately turns on and off the pair of switching elements Q1 and Q4 and the pair of switching elements Q2 and Q3 at a designated duty ratio using switching control signals S1 and S2 illustrated in FIGS. 6A, 6B, 9C, and 9D. As a result, an AC voltage having an effective value corresponding to the duty ratio is applied to the primary winding 163a of the transformer 163, as illustrated in FIG. 6C. As a result, an AC primary current Iin having an effective value corresponding to the duty ratio flows, as illustrated in FIG. 6D. As a result, a high-voltage AC voltage corresponding to the turns ratio NR is generated in the secondary winding 163b. This high voltage AC voltage is full-wave rectified by the full-wave rectifier circuit 164a and converted into a DC voltage, which is then smoothed by the smoothing capacitor C1 and output as shown in FIG. 9B.

[0064] The waveform control unit 141 also references the data stored in the polarity control table 134 and supplies the generated polarity control signal to the second driver 166. In response to the polarity control signal, the second driver 166 sets the switching control signal S3 to a high level during the period when a positive voltage should be applied to the recipient, and sets the switching control signal S4 to a high level during the period when a negative voltage should be applied to the recipient, as shown in Figures 9(E) and 9(F). As a result, during the period when a positive voltage should be applied to the recipient, the switching elements Q5 and Q8 are turned on, applying a positive voltage to the recipient, and during the period when a negative voltage should be applied to the recipient, the switching elements Q6 and Q7 are turned on, applying a negative voltage to the recipient. This allows an electric shock with a bipolar voltage waveform to be applied to the recipient.

[0065] 3 is a communication interface that performs wireless or wired communication with an external device (not shown) such as a server device under the control of the control unit 14. The audio output unit 20 includes a sound output device such as a speaker. Under the control of the control unit 14, the audio output unit 20 outputs audio, warning sounds, etc. that guide the operation of the AED 1.

[0066] Electrodes 30A and 30B are needle-shaped electrodes to be attached to a recipient in a cardiac arrest state. Electrode 30A is connected to high-voltage generator 16, electrocardiogram signal acquirer 17, and status detector 18 via cable 40A. Electrode 30B is connected to high-voltage generator 16, electrocardiogram signal acquirer 17, and status detector 18 via cable 40B. Unlike ordinary pad-type electrodes, the use of needle-shaped electrodes 30A and 30B ensures connection between the recipient and electrodes 30A and 30B even when the recipient's body surface is wet.

[0067] The electrocardiogram signal acquiring unit 17 filters noise contained in the electrocardiogram signals from the electrodes 30A and 30B, and amplifies the electrocardiogram signals after filtering out the noise. The electrocardiogram signals amplified by the electrocardiogram signal acquiring unit 17 are sent to the control unit 14 and used for electrocardiogram analysis. The control unit 14 also displays the electrocardiogram signals on the display unit 11 as appropriate.

[0068] The state detection unit 18 measures, for example, the impedance between the electrode 30A and the electrode 30B, i.e., the impedance (biological impedance) of the portion of the recipient through which current passes. The state detection unit 18 outputs the measured impedance to the control unit 14.

[0069] Next, we will explain the operation and usage of the AED 1 having the above configuration. The AED 1 is small and lightweight, so it can be easily carried by a rescuer, and does not require much space when installed.

[0070] When using the AED 1, the rescuer operates the operation unit 12 to turn on the power and insert the electrodes 30A and 30B into positions that sandwich the recipient's heart, for example, the positions shown in FIG. 2 . In this state, the rescuer presses the status detection button in the button group 12b of the operation unit 12 to determine whether the electrodes 30A and 30B are correctly attached. In response to this operation, the control unit 14 causes the high-voltage generation unit 16 to generate a preset voltage and apply it between the electrodes 30A and 30B. The status detection unit 18 measures the voltage between the electrodes 30A and 30B and the current flowing through the electrode 30A or 30B, measures the bioimpedance Rb, and notifies the control unit 14.

[0071] The control unit 14 determines whether the electrodes 30A, 30B are attached correctly (whether the bioimpedance is within a predetermined range) based on the measured bioimpedance. The control unit 14 notifies the user of the determination result via the display unit 11 and the audio output unit 20. The rescuer follows the notification and reattaches the electrodes 30A, 30B as necessary.

[0072] The rescuer checks the electrocardiogram of the recipient as necessary. In this case, with electrodes 30A and 30B attached to the recipient, the rescuer presses the electrocardiogram detection button in button group 12b. In response to this operation, control unit 14 activates electrocardiogram signal acquisition unit 17. ECG signal acquisition unit 17 measures the voltage between electrodes 30A and 30B and supplies the measured voltage to control unit 14. Control unit 14 displays the waveform of the detected bioelectrical voltage on display unit 11. The rescuer checks the electrocardiogram of the recipient according to the display.

[0073] Next, the process of applying a high-voltage pulse to a rescuee will be described with reference to the flowchart of FIG. 10. When applying a high-voltage pulse to a rescuee, the rescuer operates the operation unit 12 to display a list of pre-registered high-voltage pulse waveforms (step S11). The rescuer selects one of the displayed waveforms (step S12: Yes). The selected waveform is the set waveform. Note that steps S11 and S12 may be skipped by selecting a high-voltage pulse waveform to be applied and storing it in the memory unit 13 in advance. Next, the control unit 14 waits for the application button from the button group 12b to be pressed (step S13).

[0074] When the apply button is pressed (step S13: Yes), the waveform control unit 141 of the control unit 14 executes a waveform table generation process to generate the waveform table 135 (PWM control table 133 and polarity control table 134) (step S14).

[0075] The waveform table generation process will be described in detail with reference to the flowchart of FIG. 11 . First, the control unit 14 controls the high-voltage generator 16 and the state detector 18 to measure bioimpedance (step S21). Specifically, the control unit 14 causes the high-voltage generator 16 to generate a predetermined voltage and measure the current flowing through the electrode 30A or 30B, thereby measuring bioimpedance Rb (step S21). Next, the control unit 14 calculates the ratio Rb / Rr of the measured bioimpedance value Rb to the reference value Rr of the bioimpedance expected by the basic waveform stored in the basic waveform table 132 (step S22). Next, the waveform controller 141 of the control unit 14 multiplies the peak value of the set waveform selected in step S14 by the square root of the bioimpedance ratio, √(Rb / Rr), to calculate a corrected voltage waveform Va (step S23), so that the energy of the high-voltage pulse applied to the recipient is the reference value E. Next, the waveform controller 141 sets t to 0 (step S24). Next, the waveform control unit 141 determines the period λ and pulse widths PW1 and PW2 of the switching control signals S1 and S2 based on the peak value of the correction voltage waveform Va at time t (step S25). Next, the waveform control unit 141 determines polarity data based on the polarity of the basic voltage waveform Vr at time t (step S26). Next, the waveform control unit 141 determines whether t has reached the voltage application end time (step S27). If t has not reached the end time (step S27: No), the waveform control unit 141 updates t to t = t + 1 (step S28), returns to step S25, and performs the same process for the next time t. If t has reached the end time (step S27: Yes), the waveform control unit 141 stores the PWM control signals at the series of times t determined by the process of step S25 multiple times in the PWM control table 133, and stores the polarity control signals at the series of times t determined by the process of step S26 multiple times in the polarity control table 134 (step S29). In this way, the PWM control table 133 and the polarity control table 134 are formed by high-speed calculation processing by the DSP of the waveform control unit 141. Next, the process proceeds to step S15 in Fig. 10, where the control unit 14 starts an internal timer.

[0076] Next, the control unit 14 supplies a PWM control signal to the first driver 162 based on the data for the measurement time t of the internal timer among the PWM control signals stored in the PWM control table 133 (step S16). The PWM control signal indicates the period λ and pulse widths PW1 and PW2 or duty ratio of the switching elements Q1 to Q4.

[0077] Furthermore, the control unit 14 supplies a polarity control signal to the second driver 166 based on the data for the measurement time t among the polarity control signals stored in the polarity control table 134 (step S17).

[0078] Next, the control unit 14 determines whether the application of the high-voltage pulse has ended based on the time t measured by the internal timer (step S18). If the application has not ended (step S18: No), the process returns to step S16, and the application of the high-voltage pulse continues. On the other hand, if the application has ended (step S18: Yes), the high-voltage pulse application process ends. Note that the process of measuring and displaying an electrocardiogram may be started automatically.

[0079] In response to the PWM control signal output in step S16, the first driver 162 alternately turns on and off the pair of switching elements Q1 and Q4 and the pair of switching elements Q2 and Q3 at the specified duty ratio. This causes an AC primary current Iin with a magnitude corresponding to the duty ratio to flow through the primary winding 163a of the transformer 163, and a high-voltage AC voltage corresponding to the turns ratio is generated in the secondary winding 163b. This high-voltage AC voltage is full-wave rectified by the full-wave rectifier circuit 164a and converted into a high-voltage DC voltage, which is then smoothed by the smoothing capacitor C1 and output as voltage V2. As shown in FIG. 9B, voltage V2 has a waveform equal to the absolute value waveform of the correction voltage waveform Va.

[0080] In response to the polarity control signal output in step S17, the second driver 166 sets the switching control signal S3 to a high level during the period when a positive high-voltage pulse should be applied, turns on the pair of switching elements Q5 and Q8, applies a forward voltage V2 between the electrodes 30A and 30B, and applies a positive high-voltage pulse Vout to the rescuee. Also, during the period when a negative high-voltage pulse should be applied, the second driver 166 sets the switching control signal S4 to a high level, turns on the pair of switching elements Q6 and Q7, applies a forward voltage V2 between the electrodes 30A and 30B, and applies a negative high-voltage pulse Vout to the rescuee.

[0081] In this way, a high-voltage pulse having a corrected voltage waveform Va as shown in Fig. 9A is applied to the recipient. The high-voltage pulse of the corrected voltage waveform Va applies a substantially constant energy E regardless of variations in bioimpedance caused by individual differences among recipients or variations in the state of attachment of the electrodes 30A and 30B.

[0082] As described above, the AED 1 according to the embodiment of the present disclosure generates a high voltage using DC-AC conversion by an inverter circuit and a transformer, eliminating the need for a high-voltage capacitor to maintain the high voltage and enabling miniaturization. Furthermore, the voltage of the high-voltage pulse is adjusted in a time series manner by the full-bridge inverter circuit 161, which is controlled on a pulse-by-pulse basis by a PWM signal. This makes it possible to easily generate high-voltage pulses with complex waveforms suitable for defibrillation. Furthermore, the polarity reversal circuit 165, controlled by a polarity reversal signal, reverses the polarity of the voltage V2 output by the rectifying and smoothing circuit 164 at appropriate timing according to the set waveform. This makes it possible to easily generate high-voltage pulses with biphasic waveforms, such as BTE and RLB waveforms.

[0083] Furthermore, the AED 1 according to this embodiment is provided with a smoothing circuit that smoothes the voltage boosted by the transformer 163, making it possible to suppress pulsating current and generate a high-voltage pulse with a more ideal waveform.

[0084] In the above embodiment, an example in which a high-voltage pulse is applied to the recipient once has been described, but it may also be applied multiple times. Hereinafter, a mode in which a high-voltage pulse is applied multiple times with a certain time interval between them will be referred to as a dual shock mode. Figure 12 shows an example of a high-voltage pulse generated by the high-voltage generator 16 in the dual shock mode. In this example, two high-voltage pulses with an RLB waveform are generated consecutively with a time interval of 2 seconds. Note that in the dual shock mode, the first and second high-voltage pulses may have different waveforms. Furthermore, more than two high-voltage pulses may be generated consecutively and applied to the recipient.

[0085] In the dual shock mode, the AED 1 applies two consecutive high-voltage pulses to the recipient at a preset time interval. For example, the operator can switch the operation mode of the AED 1 to the dual shock mode by operating the operation unit 12. The operator can also set the time interval between the two consecutive high-voltage pulses to a range of 0.25 seconds to 3.00 seconds by operating the operation unit 12.

[0086] In this case, for example, the entire waveform data for multiple times may be stored in the waveform memory area 131 and applied by the high-voltage pulse application process shown in FIG. 10. Alternatively, as shown in the flow chart of FIG. 13, a high-voltage pulse of a set waveform is applied (step S31), and then it is determined whether the high-voltage pulse has been applied a preset number of times (step S32). If not, a certain interval time is measured (step S33), and the process returns to step S31 to apply the next high-voltage pulse. The waveform of the next high-voltage pulse to be applied may be the same as or different from the waveform of the high-voltage pulse previously applied. Furthermore, when applying three or more times, the interval length may be the same or different each time. Furthermore, the waveforms to be applied and the order in which they are applied may be editable.

[0087] If it is determined in step S32 that the process is finished, the process ends.

[0088] In the case of the process of FIG. 13, if the number of repetitions, the waveforms and order of the high voltage pulses to be applied, and the interval periods are stored in advance in the memory unit 13, there is no need to store all of the waveform data for multiple pulses in the waveform memory area 131, and the capacity of the memory unit 13 can be reduced.

[0089] (Modifications) The above embodiment can be modified in various ways. For example, in the above embodiment, it has been described that the waveform of the high-voltage pulse can be set from among three types: a monophasic waveform, a BTE waveform, and an RLB waveform. However, the types of waveforms that can be set are not limited to these. Furthermore, the waveform of the high-voltage pulse that can be output by the AED 1 may be fixed to only one. For example, if the waveform of the high-voltage pulse that can be output by the AED 1 is fixed to only the monophasic waveform, the polarity reversal circuit 165 does not need to be provided in the high-voltage generation unit 16.

[0090] In addition, any high-voltage pulse waveform can be generated and edited by reading out waveform data stored in basic waveform table 132, processing and editing the waveform in accordance with the operation of operation unit 12 while displaying the waveform on display unit 11, and overwriting or saving it under a different name. Furthermore, waveform data generated or edited by an external computer or the like may be stored in storage unit 13 via communication unit 15.

[0091] The electrodes 30A, 30B of the AED 1 are not limited to the needle-shaped electrodes shown in Fig. 1, and electrodes of various shapes can be used. For example, as shown in Fig. 14, the AED 1 may be provided with pad-shaped electrodes 50A, 50B instead of the needle-shaped electrodes 30A, 30B. Furthermore, the surfaces of the pad-shaped electrodes 50A, 50B may be provided with structures such as fine needles, blades, teeth, or irregularities to reduce contact resistance with the body surface of the person being rescued.

[0092] Furthermore, the electrodes 30A and 30B to which the present disclosure is applied may each have a clothespin-type configuration, as exemplified in Fig. 15. The electrode 30 shown in Fig. 15 has a grip portion 301 and a holding portion 302. The rescuer grips the grip portion 301 of the electrode 30 to open the holding portion 302, inserts and clamps the skin K between the grip portions 302, and then releases the grip of the grip portion 301 to allow the holding portion 302 to hold the skin K, thereby attaching the electrode 30 to the skin K.

[0093] Furthermore, a plurality of needle-shaped parts 303 like a pin holder may be arranged on the grip part 302. At least a part of the needle-shaped parts 303 will be present inside the skin K.

[0094] Needle-shaped electrodes, clothespin-shaped electrodes, pad-shaped electrodes with fine needles, etc. are effective in ensuring stable electrical connection between the electrode and the person being rescued, even in environments where the anterior chest is continuously wet, such as in rainy weather.

[0095] In addition, the circuits and operations can be modified as appropriate. For example, although the explanation has been given mainly in terms of positive logic, the circuits may be designed in terms of negative logic. Furthermore, the materials and numerical values ​​exemplified in the embodiments are merely examples and are not limiting.

[0096] In addition to the bioimpedance, there are also losses in the internal impedance of the battery, the inverter, the transformer, and the rectifier circuit. Therefore, based on the actually measured output current and output voltage, the peak value and pulse length of the basic voltage waveform Vr may be corrected so that the energy of the applied high-voltage pulse matches the target value.

[0097] Alternatively, a correction table may be prepared that associates the total amount of loss with the correction content, the total loss may be calculated, the correction content may be calculated using the calculated total loss as a key, and the basic voltage waveform Vr may be corrected in accordance with the calculated correction content.

[0098] In the above description, the voltage to be applied at each timing t is determined by correcting the basic voltage waveform Vr. However, this disclosure is not limited to this. For example, it is possible to determine the high-voltage waveform to be applied without using the basic voltage waveform Vr. For example, the basic waveform table 132 may be removed, and the envelope of the high-voltage pulse voltage and the total amount of electrical energy to be applied may be stored in the waveform memory area 131. Based on the measured bioimpedance value Rb, the waveform control unit 141 determines the voltage to be applied at each timing so that the total energy of the high-voltage pulse to be applied matches the target value E and the envelope matches the pre-stored basic envelope.

[0099] In the above embodiment, the full-bridge inverter circuit 161 is an example of an inverter circuit that converts a DC voltage into an AC voltage by performing a switching operation with a duty ratio according to a switching control signal. The transformer 163 is an example of a transformer that boosts the AC voltage converted by the inverter circuit. The full-wave rectifier circuit 164a is an example of a rectifier circuit that rectifies the boosted voltage. The smoothing capacitor C1 is an example of a smoothing circuit that smooths the voltage output from the rectifier circuit. The electrodes 30A and 30B are examples of electrodes that apply an electric shock to a rescue recipient based on the output voltage of the rectifier circuit. The polarity reversal circuit 165 is an example of a polarity reversal circuit that applies the output voltage of the rectifier circuit to the electrodes in a forward or reverse direction according to a polarity control signal. Therefore, the switching control signals S3 and S4 are examples of polarity control signals.

[0100] The waveform control unit 141 and the first driver 162 are an example of a duty ratio control means that supplies a switching control signal to the inverter circuit to control the electrical energy supplied from the inverter circuit to the transformer. The PWM control table 133 is an example of a memory unit that stores data representing changes in duty ratio over time corresponding to the voltage waveform of the electric shock to be applied to the recipient. The polarity control table 134 is also an example of a memory unit that stores data representing the polarity of the voltage to be applied to the electric shock to the recipient. The operation unit 12 and the control unit 14 are an example of a selection means that selects one of multiple voltage waveforms to be applied. The control unit 14 and the state detection unit 18 are an example of a measurement means that measures the impedance between the electrodes attached to the recipient. The operation unit 12, the control unit 14, and the communication unit 15 are an example of a means for updating the data representing changes in duty ratio over time stored in the memory unit. The waveform control unit 141 and the second driver 166 are an example of a polarity control means that sends a polarity control signal to the polarity inversion circuit to apply a voltage of a polarity corresponding to the set waveform to the electrodes.

[0101] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to such specific embodiments, and the present disclosure includes the inventions described in the claims and their equivalents.

[0102] 1...AED, 10...main body, 30A, 30B, 50A, 50B...electrodes, 40A, 40B...cable, 11...display unit, 12...operation unit, 13...storage unit, 131...waveform table, 14...control unit, 141...waveform control unit, 15...communication unit, 16...high voltage generation unit, 161...full bridge inverter circuit, 162 first driver, 163 transformer, 163a...primary winding, 163b...secondary winding, 164 rectification smoothing circuit, 165 polarity inversion circuit, 166 second driver, Q1 to Q8...switching elements, D1 to D4...diodes, C1...capacitor, 17...electrocardiogram signal acquisition unit, 18...state detection unit, 19...power supply unit, 20...audio output unit

Claims

1. An automatic external defibrillator comprising: an inverter circuit which converts a DC voltage into an AC voltage by performing a switching operation with a duty ratio according to a switching control signal; a transformer which boosts the AC voltage converted by said inverter circuit; a rectifier circuit which rectifies the voltage boosted by said transformer; electrodes which apply to a recipient an electric shock based on the output voltage of said rectifier circuit; and duty ratio control means which supplies said switching control signal to said inverter circuit and controls the electric energy supplied from said inverter circuit to said transformer.

2. An automatic external defibrillator as claimed in claim 1, further comprising a memory unit which stores data representing changes in duty ratio over time corresponding to the voltage waveform of the electric shock to be applied to the recipient, and said duty ratio control means controls the duty ratio of the switching operation of said inverter circuit in accordance with the data stored in said memory unit.

3. The automatic external defibrillator of claim 2, wherein the memory unit stores data representing changes in duty ratio over time corresponding to each of a plurality of voltage waveforms of the electric shock to be applied to the recipient, and further comprises a selection means for selecting one of the plurality of voltage waveforms, and the duty ratio control means controls the duty ratio of the inverter circuit in accordance with the data corresponding to the voltage waveform selected by the selection means.

4. An automatic external defibrillator as claimed in claim 2 or 3, comprising: a measuring means for measuring impedance between the electrodes attached to a recipient; a means for storing a basic waveform of an applied voltage; and a means for correcting the basic waveform based on the impedance measured by the measuring means, and for generating data showing a change in the duty ratio with respect to time based on the corrected waveform.

5. The automatic external defibrillator according to claim 2, further comprising a means for updating data indicating a change in duty ratio with respect to time stored in said memory unit.

6. An automatic external defibrillator as claimed in any one of claims 1 to 5, further comprising: a polarity reversal circuit which applies to said electrodes the output voltage of said rectifier circuit in a forward or reversed state in accordance with a polarity control signal; and polarity control means which transmits said polarity control signal to said polarity reversal circuit to apply to said electrodes a voltage of a polarity corresponding to the voltage waveform of the electric shock to be administered.

7. An automatic external defibrillator as claimed in claim 6, further comprising a memory unit for storing data indicating the polarity of the applied voltage corresponding to the voltage waveform of the electric shock to be applied to the recipient, and said polarity control means controls said polarity reversal circuit in accordance with the data stored in said memory unit.

8. The automatic external defibrillator according to any one of claims 1 to 7, further comprising a smoothing circuit for smoothing a voltage output from the rectifier circuit.

9. The automatic external defibrillator according to any one of claims 1 to 8, wherein the duty ratio control means generates a plurality of voltage pulses by driving the inverter circuit a plurality of times at a predetermined time interval.

10. An automatic external defibrillator according to any one of claims 1 to 9, wherein the electrodes have a needle, pad or scissors shape and are attached to a person being rescued.

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