Pocket-sized automated external defibrillator

Abstract

An automated external defibrillator (AED) device may include a high voltage capacitor (HV Cap) configured to store energy required to deliver a defibrillation shock to a patient, a battery configured to charge the HV Cap, a DC / DC converter circuit including a high voltage transformer, FET switches with associated drivers, and rectifier diodes, an H-bridge circuit configured to convert energy released from the HV Cap into a biphasic pulse, and a memory and a microprocessor configured to operate the AED device. In particular, the HV Cap, the DC / DC converter circuit, the H-bridge circuit, one or more batteries, and the memory and microprocessor may be contained within a pocket-sized housing, the AED device may be configured to continuously monitor and adjust the rate at which the battery charges the HV Cap, and the AED device may include a variable frequency relaxation oscillator circuit configured to obtain a Z body measurement of the patient.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the priority of U.S. Provisional Patent Application No. 63 / 142,910, filed on January 28, 2021, which is incorporated herein by reference.

[0002] This disclosure generally relates to the field of medical electronics, and more particularly, to a portable automated external defibrillator (AED).

Background Art

[0003] According to the World Health Organization, an estimated 18 million people die each year from cardiovascular disease (CVD), which is the leading cause of death worldwide. Each year, nearly 800,000 Americans have a heart attack, and according to the American Heart Association (AHA), nearly 300,000 Americans die each year from sudden cardiac arrest (SCA).

[0004] People with risk factors such as hypertension, diabetes, or hyperlipidemia, or people with heart disease, have the highest risk of heart attack or SCA. And each year, nearly 200,000 people who have previously experienced a heart attack suffer a recurrence. Many second heart attacks are fatal.

[0005] Furthermore, 70% of heart attacks are out - of - hospital cardiac arrests (OHCA), and 90% of OHCA cases are fatal. During cardiac arrest, survival depends on the speed at which a life - saving shock can be delivered to the heart by a defibrillator, and for every minute of delay, the chance of survival decreases by 10%. However, in the United States, the average length of time between an emergency call to the police and the arrival of emergency medical services (EMS) is about 8 minutes, or 14 minutes in rural areas. As a result, most deaths from heart attacks occur because defibrillation therapy is not administered quickly enough.

[0006] Unfortunately, even if an ambulance or paramedics arrive at the victim's location within eight minutes, brain injury may have already occurred, as more than five minutes of oxygen deprivation can cause irreversible brain damage. Therefore, even if a patient survives a heart attack, they may suffer permanent functional impairment and may not be able to enjoy a full life afterward.

[0007] To save lives, defibrillation therapy must be delivered to the homes of individuals with risk factors for heart disease. However, conventional AEDs are typically found only in public places such as airports and gymnasiums. These conventional AEDs are large, bulky, and complex, and are likely to be somewhat intimidating to most people. Conventional AEDs are also often installed in wall-mounted enclosures with signs indicating that an alarm will sound when the door is opened. In an emergency, this can have the opposite effect, increasing the concern and anxiety of a potential good Samaritan, potentially preventing them from taking action. Furthermore, up to 20% of conventional AEDs are barely functional at the time, and many of these AEDs are not clearly marked when maintenance is needed or when it is required.

[0008] Therefore, it would be desirable to enable defibrillation therapy to be performed closer to people with risk factors for heart disease. It would also be desirable to provide an AED device that is compact enough for family members or caregivers of people with heart disease to carry, easy to use, readily available when and where needed, and provides highly visible warnings whenever service or maintenance is required. [Overview of the project]

[0009] In one embodiment, an automated external defibrillator (AED) device is provided, which includes a high-voltage capacitor (HV Cap) configured to store the energy required to deliver a defibrillating shock to a patient; one or more batteries configured to charge the HV Cap; a high-voltage transformer (HV XFMR); a field-effect transistor (FET) switch with associated drivers; and a rectifier diode, preferably comprising a DC / DC converter circuit configured to increase the battery voltage to about 2000 volts; an H-bridge circuit configured to convert the energy released from the HV Cap into biphasic pulses; and memory and a microprocessor configured to store and execute computer-executable instructions for the operation of the AED device, wherein the HV Cap, DC / DC converter circuit, H-bridge circuit, one or more batteries, and memory and microprocessor are housed in a pocket-sized housing. In some embodiments, the AED device further includes a pair of defibrillator pads and a cable for operably connecting the HV Cap to the pair of defibrillator pads, the defibrillator pads also being pocket-sized.

[0010] In another embodiment, an AED device is provided that is configured to continuously monitor and adjust the rate at which one or more batteries charge the HV Cap. In a preferred embodiment, the AED device is configured to simultaneously monitor the discharge current and temperature of one or more batteries and to charge the HV Cap at the maximum possible rate with the available power from one or more batteries, without exceeding either the maximum temperature or maximum discharge rate of one or more batteries.

[0011] In yet another embodiment, an AED device is provided that includes a variable frequency relaxation oscillator circuit configured to acquire a patient's Z-body measurement, the circuit being effective in self-oscillating at a frequency proportional to the patient's body impedance.

[0012] In yet another embodiment, an AED device is provided that includes a power handler circuit including a real-time clock (RTC) and does not enter sleep mode when the main microprocessor is powered off, the power handler circuit being configured to control the AED device when the main microprocessor is powered off by the RTC, and the RTC being configured to periodically power on the main microprocessor to perform an embedded self-test (BIST) sequence. [Brief explanation of the drawing]

[0013] A detailed description is given with reference to the attached drawings. The use of the same reference numeral may indicate similar or identical items. Various embodiments may utilize elements and / or components other than those illustrated in the drawings, and some elements and / or components may not be present in those various embodiments. The elements and / or components in the drawings are not necessarily drawn to scale.

[0014] [Figure 1A] This is a front perspective view of an AED device according to one disclosed embodiment of the present invention. [Figure 1B] Figure 1A is a rear perspective view of the AED device shown. [Figure 2A] A perspective view of a defibrillator pad configured for packaging according to one embodiment of the disclosed invention. [Figure 2B] Figure 2A is an exploded view of the defibrillator pad and its components. [Figure 3A] This is a front view of an AED circuit board and high-voltage capacitor assembly according to one disclosed embodiment of the present invention. [Figure 3B] Figure 3A is a rear view of the AED circuit board and high-voltage capacitor assembly shown. [Figure 4A] This is a side view of the disassembled and assembled AED circuit board according to one disclosed embodiment of the present invention. [Figure 4B] Figure 4A is a rear perspective view of the AED circuit board shown. [Figure 5] A software block diagram for an AED device according to one embodiment of the disclosed invention. [Figure 6] An example of a high voltage capacitor charging circuit according to one embodiment of the disclosed invention. [Figure 7] A block diagram depicting a Z body measurement sequence according to one embodiment of the disclosed invention. [Figure 8] An example of a conventional Z body measurement circuit, common in the prior art. [Figure 9] An example of a Z body measurement circuit utilizing a relaxation oscillator according to one embodiment of the disclosed invention. [Figure 10] A block diagram depicting an ECG and shock delivery sequence according to one embodiment of the disclosed invention. [Figure 11] A block diagram depicting an embedded self - test (BIST) sequence according to one embodiment of the disclosed invention. [Figure 12] An example of a speaker verification circuit utilizing microphone monitoring according to one embodiment of the disclosed invention. [Figure 13] An example of an analog front - end verification circuit according to one embodiment of the disclosed invention.

Best Mode for Carrying Out the Invention

[0015] A new, more compact automated external defibrillator (AED) device has been developed. Advantageously, it is pocket - sized, and its size is achieved by combining unique hardware and software components with the practical innovations described herein. This AED device is small enough to be carried with a patient, and advantageously, it can be present whenever and wherever it may be needed.

[0016] As used herein, the term "pocket size" means that the AED device is small enough to be carried by a person within the pocket of a coat or pants, or within a small wallet or handbag having dimensions of 170 mm × 95 mm × 40 mm or less.

[0017] One of the keys to reducing the size and weight of an AED compared to conventional AEDs is to reduce the size and / or number of batteries required by the device. This will undoubtedly reduce the amount of power stored and available to operate the AED device, and thus requires some power consumption reduction and operational innovations as described below to meet regulatory performance requirements while maintaining or exceeding other performance expectations such as reliability, maintenance / service time intervals. In a preferred embodiment, the AED device as disclosed herein uses four CR2 batteries. CR2 batteries are preferred for reasons of size, charging time, and combination of available power sources, but the AED device can be adapted to use other suitable types or numbers of commercially available batteries that meet the size and performance requirements of currently disclosed AED devices.

[0018] Similarly, the size of the defibrillator pads used in this AED is also reduced compared to the large-sized defibrillator pads used in conventional AEDs. In a preferred embodiment, in accordance with the minimum allowable pad size according to the FDA, the pad size is reduced to 6.0 inches × 3.3 inches (152 mm × 84 mm) without sacrificing effectiveness, which represents a reduction in size compared to the size of conventional AEDs.

[0019] An AED device measures the patient's body impedance, calculates the energy required to deliver an appropriate shock, analyzes the patient's electrocardiogram (ECG) to determine if the patient has a rhythm that can receive a shock, and delivers the appropriate energy as a life-saving shock. Even more advantageously, the AED devices described herein are small enough to be easily carried by a person with heart disease, a family member of that person, or another caregiver, for example, in a clothing pocket, handbag, or backpack. Thus, AED devices facilitate life-saving by bringing defibrillation therapy to the home and other locations where conventional AEDs are unavailable and / or timely access to emergency medical service staff is not possible.

[0020] Furthermore, the AED device advantageously offers several features that facilitate its use and reliability. For example, in some embodiments, the AED device includes a speaker that provides voice prompts to quietly guide the user on what to do in an emergency. In addition, the speaker also informs the user when the battery or defibrillator pads need to be replaced, when the internal temperature of the device becomes too hot, or when other maintenance services are required. The voice prompts can be programmed in many languages. Furthermore, in a preferred embodiment, the AED device performs several self-checks to prepare as needed, or warns the user when a malfunction occurs in the microprocessor, speaker, or other device, such as an LED and piezo buzzer included in the AED device, so that maintenance services can be performed on the AED device before it is requested to be used.

[0021] In preferred embodiments, the front of the AED device is streamlined with a minimum number of buttons and lettering to avoid distracting or distracting the user. For example, in preferred embodiments, the AED device includes only a single button for the user to “power on” the device and begin using it. In some other embodiments, the AED is activated by a capacitive switch that powers on the device each time the user touches it, or by a motion sensor that powers on the device each time movement is detected (e.g., each time it is removed from its storage pouch or sleeve). In these embodiments, the goal is to make it as simple as possible for the user to use the device during stressful medical situations.

[0022] A preferred embodiment of the AED device is shown in Figures 1A-1B. The AED device 100 includes a housing 102 that houses the electronic components inside the device 100. In the preferred embodiment, the housing 102 measures 6.1 inches (155 mm) in length (L), 3.4 inches (86 mm) in width (W), and 1.1 inches (28 mm) in height (H), and weighs only about 1 pound (450 g).

[0023] As shown in Figure 1A, the surface of the housing 102 is neat and includes a single ON button 106, a speaker hole 110, a piezo buzzer hole 112, and an LED status light 108. The AED device 100 does not include an OFF button, thereby preventing the user or bystander from accidentally turning off the power during use. As shown in Figure 1B, the rear of the housing 102 has a battery box cover 114, which is configured to provide access to the battery inside the AED device 100. Extending from the top of the housing 102 are two defibrillator cables 104 (which connect to the corresponding defibrillator pads 202, 204, as shown in Figures 2A-2B).

[0024] When not in use, the AED device 100, defibrillator cable 104, and defibrillator pads 202, 204 can be stored together in a small pouch, sleeve, or case (not shown). For example, it may be a soft cloth pouch, a bifold case, etc. The pouch, sleeve, or case may be designed to minimize the silencing or blocking of auditory or visual service notifications emitted by the AED device.

[0025] One embodiment of the defibrillator pads 202, 204 is shown in Figures 2A-2B. The defibrillator pads 202, 204 are integrated with the defibrillator cable 104, so that when the defibrillator pads 202, 204 are placed on the patient's chest, the shock from the AED device is transmitted through the defibrillator cable 104 to the defibrillator pads 202, 204, delivering a shock to the patient. As shown in Figure 2A, the defibrillator pad storage assembly 200 includes laminated paper 206 placed between the conductive gel layers 203, 205 of the defibrillator pads 202, 204, which are stored facing each other in a sealed, airtight pouch (not shown). This packaging configuration helps maintain the integrity of the conductive gel layers 203, 205. As shown in each figure, the defibrillator pads 202 and 204 have similar length and width dimensions to the housing 102, so that the housing facilitates their compact storage together. In one embodiment, the defibrillator pads 202 and 204 are approximately 6 cm long and about 3 cm wide. Other dimensions for the defibrillator pads are also possible, as long as the defibrillator pads comply with the relevant regulatory requirements. For example, the U.S. Food and Drug Administration (FDA) requires that defibrillator pads must total at least 150 cm². 2 , or 75cm per pad 2 It is required to have a contact area.

[0026] Figure 2B shows the structure of the defibrillator pads 202, 204 and the configuration for packaging. Each defibrillator pad 202, 204 has a conductive surface coated with conductive gel layers 203, 205. A removable pressure-sensitive laminate 206 is placed between the conductive gel layers 203, 205 of the defibrillator pads 202, 204.

[0027] Figures 3A-3B show the internal electronic components of the AED device 100, including a high-voltage capacitor (HV Cap) 302 and a circuit board 304 (shown in more detail in Figures 4A-4B), which together form an internal assembly 300. Figure 3A shows a front view of the internal assembly 300. According to this embodiment, the electronic components are arranged on a main printed circuit board (PCB) 306. More specifically, the front of the main PCB 306 houses a power button 308, a speaker 310, a piezoelectric buzzer 312, an LED status light 314, a microphone 316, a backup battery 318, and a microSD memory card 320. A primary microprocessor 602 and a secondary microprocessor (not shown) are also integrated into the main PCB 306. The HV Cap 302 is attached to the distal end of the circuit board 304 by capacitor leads 322, which are connected to capacitor contacts 334 located on the rear of the main PCB 306.

[0028] Figure 3B shows a rear view of the internal assembly 300. The rear of the main PCB 306 houses four battery boxes 328 sized to hold CR2 batteries (not shown), a high-voltage transformer (HV XFMR) 326, capacitor contacts 334, and an area 330 for defibrillator cable contacts. Thus, the HV Cap 302 is indirectly connected to the batteries (not shown) by the HV XFMR 326. In this embodiment, the HV XFMR 326 converts the power supplied by the batteries (not shown) to a level that the HV Cap 302 can receive. The rear of the main PCB 306 also includes relays 332 and an H-bridge circuit on the secondary PCB 324, both of which are standard components of AED devices in various different configurations.

[0029] Figure 5 is a software block diagram showing the arrangement and interaction of these electronic components. The functions of the AED device 100 can be classified into one of two categories: defibrillation tasks and built-in self-test (BIST) tasks. Defibrillation tasks can only be performed when the AED device 100 is fully powered on, while BIST tasks are performed regardless of whether the AED device 100 is powered on or off.

[0030] In addition to these two main task categories, the AED device 100 also utilizes an audio driver (not shown), which is responsible for the interface connection between the speech synthesis device and the SD card 320 on which these audio files are stored. While the defibrillation and BIST tasks are being performed, the audio driver retrieves the appropriate audio files from the SD card 320, routes the audio to the speech synthesizer, and plays the audio for the user.

[0031] The AED device 100 also utilizes a data recording task, which also forms an interface with an SD card 320. Any data collected during a defibrillation task or BIST task is stored on the SD card 320 and can then be retrieved on an external device. The AED device 100 also includes an IrDA UART driver for interface connection with an IR transmitter or receiver. This IrDA UART functions to communicate with compatible devices. For example, the IrDA UART can transmit recorded data or receive firmware updates to be installed on the AED device 100.

[0032] Returning to the primary AED device 100 task, Figures 6-10 provide additional details regarding the primary defibrillation task, which include charging the HV Cap 302, performing Z-physical measurements, obtaining and analyzing the patient's ECG, and delivering a shock. Since the defibrillation task requires the AED device 100 to be fully powered on, the user must power on the AED device 100 to begin any of these tasks. To do so, the user presses down the ON button 106, which is connected to the power button 308, and this power button allows the microprocessor 602 to power on the internal assembly 300.

[0033] Figure 6 shows an exemplary embodiment of the HV Cap 302 charging circuit 600. The AED device 100 uses the return-connected DC / DC converter 600 shown in Figure 6 to boost the battery voltage (approximately 12 volts) to a sufficiently high voltage (up to 2000 volts) for the shock pulse.

[0034] This converter consists of a field-effect transistor (FET) switch 3002, a driver 3003, a snubber circuit 3006, a transformer 326, and a rectifier diode 3004. Under software control, a microcontroller 602 generates a pulse trail amplified by the driver 3003 to operate the gate of the FET switch 3002. The switch can be periodically opened and closed to allow current to flow or to interrupt the current flowing through the primary winding of the transformer 326. When the current is interrupted, an inverse electromagnetic force (EMF) voltage is generated on the primary winding of the transformer 326 according to Lenz's law, which describes the fundamental characteristics of this coil.

[0035] Because the number of turns in the secondary winding of transformer 326 is much greater than that of the primary winding, the EMF voltage in the secondary winding is multiplied by the turns ratio between the primary and secondary windings. This ratio is selected so that the peak of the inverse EMF pulse can reach 2000 volts. This voltage is rectified by diode 3004, which charges HV Cap 302.

[0036] In a preferred embodiment, the AED device 100 uses a CR2 battery to power the AED device 100 and charge the HV Cap 302. Because these batteries are much smaller than those used in conventional AED devices, the HV Cap 302 requires more charging time than in conventional AED devices. Conventional AED devices also typically do not begin charging until a heart rhythm capable of receiving a shock is detected. Therefore, to account for the smaller battery, the AED device 100 begins charging the HV Cap 302 immediately after the AED device 100 is powered on and before attempting to detect whether a heart rhythm capable of receiving a shock is present. According to a preferred embodiment, the HV Cap 302 will be fully charged within 30-40 seconds after the AED device 100 is powered on.

[0037] The microprocessor 602 is programmed to monitor and control the charging speed of the HV Cap 302. To charge the HV Cap 302, the microprocessor 602 sends a series of square wave pulses from the HV XFMR326 to the HV Cap 302, in which case the frequency of these pulses effectively controls the charging speed of the HV Cap 302. Thus, the microprocessor 602 is programmed with a feedback loop that adjusts the pulse frequency to adjust the charging speed as needed.

[0038] In particular, the microprocessor 602 of the AED device disclosed herein is configured to partially modify the charging speed to ensure that the battery does not exceed the manufacturer-specified discharge rate and temperature, i.e., 1000mA and 60°C in the case of a CR2 battery. Accordingly, the charging circuit 600 includes a temperature sensor 604 and a current monitor 606 for collecting and providing feedback to the microprocessor. This process ensures that the HV Cap 302 is charged at the fastest possible speed given the available battery power at that time.

[0039] Furthermore, the microprocessor 602 of the AED device disclosed herein is configured to partially modify the charging speed to take into account the functions of the AED device 100 that occur while the HV Cap 302 is being charged. For example, the speaker 310 may be giving various commands to the user during the charging process. To take into account the current that the speaker 310 is drawing from the battery, the microprocessor 602 will appropriately reduce the current to the HV Cap 302 to keep the battery within specified discharge and temperature thresholds. Then, once the voice prompt is complete, the microprocessor 602 will return to the original charging speed.

[0040] While the HV Cap 302 is charging, the AED device 100 performs two defibrillation tasks before it can deliver a shock, the first of which is to perform a body impedance (Z-body) measurement. Z-body measurement incorporates both the resistance and capacitance of the patient's body when an AC current is applied. Z-body measurement is essential in determining the magnitude of the shock to be delivered. In particular, the shock delivered by the AED device 100 is only effective if the magnitude of the current is high enough to depolarize the heart. However, the current cannot be high enough to damage the patient's cardiac tissue. Therefore, Z-body measurement ensures that the shock is within this effective non-damaging range.

[0041] The process for performing Z-body measurement is shown in Figure 7. After the user powers on the AED device 100 and properly places the defibrillator pads 202 and 204 on the patient's chest, the AED device 100 will attempt to detect Z-body measurement. According to an exemplary embodiment, as shown in Figure 9, the AED device 100 performs Z-body measurement using a relaxation oscillator circuit 900. This process is quite different from conventional AED devices that perform Z-body measurement using a circuit like the one in Figure 8. Conventional processes for performing Z-body measurement generally involve transmitting a constant high-frequency AC signal through the defibrillator cable and pads, and that signal is subject to significant external interference. Therefore, conventional AED devices must use expensive precision circuit components to measure these signals and filter out unavoidable interference.

[0042] Therefore, the relaxation oscillator circuit 900 is advantageous to use because it is simpler (and less expensive) to design than conventional Z-body measurement circuits, takes up less space, and has greater resistance to interference.

[0043] The circuit 900 shown in Figure 9 self-oscillates at a frequency defined by its timing components. The basic idea behind using this type of oscillator for Z-body measurement is to include the human body as one of the timing components for the oscillator and to capture the frequency changes generated by the oscillator. After calibration, measuring the output frequency of the circuit will determine the Z-body value of the only changing component (the human body) that caused the change.

[0044] In a preferred embodiment, the circuit includes a voltage comparator 907, which is integrated into a microprocessor 602 having an inverting input 908, a non-inverting input 909, and an output 910, voltage dividers 901 and 905, and a timing RC circuit having a fixed resistor 904 and a capacitor 906. The human body 911, which appears as a resistor in the circuit, is connected in parallel with resistor 904 via two cables called the apex 912 and the sternum 913.

[0045] The feedback resistor 902 provides the positive feedback required to initiate the oscillation process. Resistor 903 is used to scale the magnitude of the feedback signal. The circuit is powered from the power supply 914 relative to ground potential 915. The comparator 907 is an electronic device whose output state can have only two predefined values, depending on the status of its input: approximately 0 volts (V) or a volt value close to the power supply voltage. In the case of an AED supplying 3.3V to the circuit, the comparator's output 910 will be approximately 0V or 3.3V. The comparator 907 compares the voltages on its inputs 908 and 909 and sets the output 910 accordingly. If the voltage of the non-inverting input 909 is higher than the voltage of the inverting input 908, the output 910 will be set to 3.3V. Otherwise, the output 910 will be 0V.

[0046] The operation of circuit 900 is as follows: When power supply 914 is applied, the voltage on the non-inverting input 909 of comparator 907 is set according to the voltage dividers 901 and 905 packed by the apex voltage 912 through calibration resistor 903. If resistors 901 and 905 are set to equal values, in this example it will be half of the supply voltage 914, or 1.65V. However, it will increase or decrease depending on the voltage on the apex wire 912 applied to input 909 via resistor 903, and in turn depend on the status of the comparator's output 910. Based on the selected values ​​of the components, the non-inverting input 909 voltage will be approximately 1.55V when output 910 is 0V and 1.75V when output 910 is 3.3V.

[0047] Initially, the voltage on the inverting input 908 is near zero as capacitor 906 is discharged, and therefore the output 910 of comparator 907 is set to 3.3V. This voltage is applied to capacitor 906 in parallel with the body impedance (Z body) via feedback resistor 902 and timing resistor 904. Capacitor 906 will begin to charge from the current flowing through resistor 904 and body 911 toward the voltage set by the voltage divider formed by feedback resistor 902 and calibration resistor 903. The ratio of the voltage divider is set so that the final voltage on the apical wire 912 is higher than 1.75V.

[0048] When the voltage across capacitor 906 connected to the inverting input 908 exceeds 1.75V present on the non-inverting input 909, the output 910 of comparator 907 inverts from 3.3V to 0V. This reduces the voltage at the apex 912 to less than 1.55V, and the voltage on the non-inverting input 909 immediately changes to approximately 1.55V.

[0049] Next, capacitor 906 begins to discharge through resistor 904 and body 911. When the capacitor discharges from 1.75V to 1.55V, the voltage at the non-inverting input becomes higher than the voltage at the inverting input, and the cycle repeats, generating a digital frequency (between 0V and 3.3V) on the output 910 of comparator 907.

[0050] As described above, the time required for capacitor 906 to maintain a charge from 1.55V to 1.75V and to maintain a discharge from 1.75V to 1.55V depends on the RC constant R, which consists of resistor 904 and the human body impedance (Z body) in parallel. Since resistor 904 is constant and known, the only variable that determines the final oscillation period (e.g., frequency) on the output 910 of comparator 907 is the human body impedance (Z body). By calibrating the oscillator against a known set of impedances, the contribution of the human body 911 to the frequency change of the oscillator can be determined by calculating the frequency of the signal on the output 910 of comparator 907 and the Z body value.

[0051] Therefore, the microprocessor 602 requires fewer variables to calculate the Z-body measurement. Furthermore, because the relaxation oscillator circuit 900 does not use and measure analog signals, it is completely unaffected by external interference, making it optimal compared to conventional Z-body measurement circuits. And, as previously mentioned, the simplicity of the relaxation oscillator circuit requires fewer components, thus reducing the manufacturing cost and size of the device.

[0052] Furthermore, the relaxation oscillator circuit 900 does not require the use of expensive, precision resistors or capacitors. Because this circuit drives the output signal using only a voltage comparator and a few non-precision passive resistors and capacitors, it results in a significant reduction in the number of components compared to conventional Z-body measurement circuits. The patient's body impedance is determined using measurements of the circuit's output frequency. Its output is a digital signal, allowing frequency to be measured independently of amplitude, which provides greater noise immunity than conventional Z-body measurement methods.

[0053] However, in some situations, the AED device 100 may not be able to perform this measurement. Generally, if the defibrillator pads 202 and 204 are not properly positioned on the patient's chest, the AED device 100 will not perform the Z-body measurement. Therefore, after a failure to perform the Z-body measurement, the user will be instructed to adjust the defibrillator pads 202 and 204. If the measurement fails three times, the user will be instructed to perform cardiopulmonary resuscitation (CPR) instead.

[0054] If the AED device 100 successfully performs the Z-physical measurements, the AED device 100 will proceed to a second defibrillation task, which involves reading and analyzing the patient's ECG. This process is generally shown in Figure 10 and involves monitoring the patient's cardiac rhythm to determine if the patient has one of two rhythm patterns that can deliver a shock. Defibrillation is only effective when the patient is in ventricular tachycardia (Vtach) or ventricular fibrillation (Vfib), and therefore, if neither of these two shock-delivering rhythms is detected, the AED device 100 will instruct the user to perform CPR. If Vtach or Vfib is detected and the HV Cap 302 is fully charged, the AED device 100 will instruct the user to leave undisturbed before delivering a shock. The user will then be instructed to perform CPR.

[0055] The process of detecting the patient's heart rhythm utilizes an analog front-end (AFE) circuit (not shown) integrated into the main PCB 306. According to an exemplary embodiment, the AFE not only acquires ECG data but also includes a MAX30003 integrated circuit (IC) (not shown) for controlling the gain, sample rate, bias, polarity, and filter adjustments necessary to maximize the readability of the ECG signal. In this embodiment, the IC receives the patient's low-voltage heart rhythm, which is transmitted to an analog-to-digital converter (ADC) (not shown). These digital outputs are sampled periodically, and the data buffered at that point is transmitted to a microprocessor 602, which is programmed to determine whether the patient has a heart rhythm that can receive a shock. The AED device 100 must acquire at least six consecutive heart rhythms of a pattern that can receive a shock; otherwise, no shock will be delivered.

[0056] According to an exemplary embodiment, the AED device 100 utilizes a software high-voltage (HV) shock driver (not shown) to interface all circuits involved in the defibrillation process. More specifically, the HV shock driver software measures the voltage of the HV Cap 302 after Z-body measurements are performed to ensure that the voltage of the HV Cap 302 is charged to an appropriate level. Furthermore, the HV shock driver software is also responsible for controlling whether a shock is actually delivered after ECG data has been collected.

[0057] When the AED device 100 is powered on and the defibrillator pads 202 and 204 are attached to the patient, the AED device 100 continuously measures the patient's ECG waveform and classifies it in real time. If the classification is determined to be a waveform that can receive a shock, namely (i) ventricular tachycardia (Vtach) or (ii) ventricular fibrillation (Vfib), and this classification remains constant for a minimum of 6 seconds, a high-voltage shock is delivered to the patient via the defibrillator pads.

[0058] To deliver a shock, the AED device 100 utilizes an H-bridge circuit 324 that converts the energy released from the HV Cap into a biphasic pulse, which is defined as two pulses of opposite polarity applied in succession. After the shock is delivered, the AED device 100 instructs the user to perform CPR while continuing to monitor the patient's ECG. After two minutes of CPR, if analysis of the patient's ECG indicates that a second shock is needed, the above process is repeated, and a third shock is delivered if necessary. In any case, the device instructs the user to perform two minutes of CPR between shocks.

[0059] In a preferred embodiment, the AED device does not have an OFF button to prevent the device from being accidentally powered off at an inconvenient moment. Instead, the device is configured to power off after a specified inactivity period, for example, after a total inactivity period of 3 minutes. The speaker 310 will warn the user that the AED device 100 is powered off.

[0060] Apart from the defibrillation task described above, the AED device 100 performs several built-in self-test (BIST) tasks, based in part on the diagram in Figure 11. Generally, the BIST tasks ensure that the AED device 100 is functioning correctly, and most of these BIST tasks are performed while the AED device 100 is off.

[0061] Because this AED device uses a significantly smaller battery than conventional AED devices, its internal components are configured and programmed in a way that conserves as much battery power as possible. Therefore, an exemplary embodiment of AED device 100 includes a power handler system (not shown) for controlling the BIST task while conserving as much battery power as possible. More specifically, the power handler system ensures that when AED device 100 is not in use, all circuits are turned off, with the exception of a few ultra-low power components. These always-on ultra-low power components operate in the nanoampere range and include, but are not limited to, a real-time clock (RTC) (not shown). This power handler system is unique compared to conventional AED devices, which often enter a "sleep mode" when not in use. However, since sleep mode still consumes a significant amount of energy, this power handler system is particularly advantageous for reducing power consumption during prolonged periods of inactivity.

[0062] Generally, the RTC is programmed to periodically call the microprocessor 602 to initiate a BIST sequence, which involves a series of hardware verifications and battery level checks. If the BIST is successful (no errors are identified), the AED device 100 status is updated, and the green status LED 314 flashes periodically. This green status LED 314 will continue flashing until the next BIST sequence, even after the microprocessor 602 is powered off. If the BIST is unsuccessful and the speaker 310 is functioning correctly, the red status LED 314 flashes when an audio prompt such as "Service required" is given. The microprocessor 602 then powers off, during which time the red status LED 314 flashes and the piezo buzzer 312 beeps. This process is repeated every 30 minutes until the AED device 100 is serviced. If the speaker 310 malfunctions or the microprocessor 602 is unresponsive, the red status LED 314 flashes while the piezo buzzer 312 beeps. These alarms continue uninterrupted or intermittently until the AED device 100 is serviced.

[0063] Turning to the specific verifications performed during the BIST sequence, Figure 12 shows an exemplary speaker verification circuit 1200. The reliability, sound pressure level, and integrity of the voice prompts are critical in guiding the user in using the AED device, and therefore the speaker 310 needs to be monitored frequently. According to the exemplary embodiment, the speaker 310 is integrated into the housing using an O-ring or gasket (not shown) to achieve splash-proof or waterproof protection up to an acceptable ingress protection (IP) level. The speaker hole 110 in the housing 102 allows sound pressure from the speaker 310 to exit the AED device 100, but the speaker may be potentially susceptible to damage, for example, by water or a sharp object penetrating the speaker hole. This type of damage may not be noticeable to the naked eye, but it may distort or even render the voice prompts nonexistent.

[0064] In an exemplary embodiment, the main PCB 306 is fitted with a small microphone 316 positioned very close to the speaker 310. When powered on by the RTC, the microprocessor 602 generates a short sound lasting approximately 20–50 milliseconds, which is played back through the speaker 310. The microprocessor 602 also "hears" this sound as it is repeated through the microphone 316. If the speaker 310 is damaged in any way, the sound will not match, and the microprocessor 602 will enter the necessary warning sequence as described above.

[0065] Another potential vulnerability to portable AED devices is the device's temperature. More specifically, AED devices are susceptible to damage when stored in environments with temperatures exceeding the device's specified operating and storage temperature ranges. According to an exemplary embodiment, the AED device 100 continuously monitors its temperature using a temperature sensor integrated circuit (temperature sensing IC), generally shown in Figure 6. Like the RTC, the temperature sensing IC is an ultra-low power component and therefore monitors the AED device's temperature even when the microprocessor 602 is powered off. If the temperature of the AED device 100 falls outside an acceptable range, the temperature sensor IC powers on the microprocessor 602, which then enters the necessary warning sequence.

[0066] This AED device is also uniquely vulnerable to damage to the defibrillator cable 104 and the defibrillator pads 202, 204. Conventional AED devices are typically stored in a securely wall-mounted enclosure, and therefore, individual components are unlikely to be damaged by normal passing activity. In contrast, because the AED device disclosed herein is intended for personal use, it may be susceptible to tampering and damage in ways not of conventional AED devices, for example, while left unattended at home and / or while being transported in a vehicle and outdoors, thereby potentially being dropped or exposed to water and various temperatures. To ensure that the defibrillator pads 202, 204 and the defibrillator cable 104 are in a functional state, the AED device 100 has several methods for verifying the integrity of the pads 202, 204 and the cable 104.

[0067] According to the first exemplary embodiment, during the BIST sequence, the microprocessor 602 generates a low-frequency signal of approximately 30 kHz and transmits this signal through the defibrillator cable 104 and the defibrillator pads 202, 204. If the signal returns to the microprocessor 602 and matches the original signal within a predetermined error margin, the defibrillator cable 104 and the defibrillator pads 202, 204 are intact. If there is a significant change in the signal, it is likely that the defibrillator pads 202, 204 are no longer properly sealed or the conductive gel layers 203, 205 have dried out. If no signal returns at all, at least one of the defibrillator pads 202, 204 and / or the defibrillator cable 104 is significantly damaged. In any case where the transmitted signal and the returned signal do not match, the microprocessor 602 will initiate the necessary warning sequence.

[0068] In another exemplary embodiment, a pressure-sensitive laminate 206 positioned between defibrillator pads 202, 204 has at least one small hole so that conductive gel layers 203, 205 make direct contact. Here, the microprocessor 602 is programmed to periodically generate a low-voltage DC signal of approximately 3-5VDC, which is transmitted through the defibrillator cable 104 and the defibrillator pads 202, 204. Similar to the embodiments described above, the microprocessor 602 compares the returned signal (if a signal is returned) with the original signal to determine whether the defibrillator cable 104 or the defibrillator pads 202, 204 is damaged. When damage to at least one of the defibrillator pads 202, 204 and / or the defibrillator cable 104 is detected, the microprocessor 602 will initiate an appropriate warning sequence as needed.

[0069] In yet another embodiment, the integrity of the defibrillator cable 104 and the defibrillator pads 202, 204 is verified using a method similar to that described with respect to performing Z-body measurements. In particular, this verification method utilizes the relaxation oscillator circuit shown in Figure 9. During the BIST sequence, the relaxation oscillator will begin oscillating within an established frequency range. The microprocessor 602 detects this oscillation and then calculates the oscillation frequency. If the calculated oscillation frequency is within the established range, the defibrillator cable 104 and the defibrillator cables 202, 204 are functioning correctly. If the calculated frequency is outside this range, or if the microprocessor 602 is unable to detect the oscillation, at least one of the defibrillator pads 202, 204 and / or the defibrillator cable 104 is damaged, and the microprocessor 602 will enter the necessary warning sequence.

[0070] The FDA requires that the defibrillator pads of an AED device be replaced at least every two years. Therefore, according to an exemplary embodiment, the RTC is programmed with a timer that will alert the microprocessor 602 every two years when the defibrillator pads 202, 204 must be replaced. When the microprocessor 602 is alerted that maintenance service is needed, it will initiate a predetermined warning sequence to inform the user that new defibrillator pads 202, 204 are needed.

[0071] The BIST sequence also includes verifying the functionality of the AFE circuit. According to an exemplary embodiment, this process is performed using the circuit shown in Figure 13. When the AED device 100 enters the BIST sequence, the microprocessor 602 transmits a low-frequency signal simulating a heartbeat of approximately 1–5 Hz to the AFE circuit. Upon receiving this signal, the AFE circuit reads and processes the signal as if it were collecting ECG data, processes the data accordingly, and reports it to the microprocessor 602. The AFE circuit is considered to be functioning correctly when the data returned to the microprocessor 602 matches the original signal within a predetermined error margin. However, if no data is returned, or if the returned data falls outside the predetermined error margin, the microprocessor 602 enters the necessary warning sequence.

[0072] Furthermore, the BIST sequence is involved in several additional verifications. According to an exemplary embodiment, the BIST sequence also verifies the power supply voltage and battery status. The user will be appropriately warned if the power supply voltage is low or if an error is detected in the battery status. However, the AED device 100 is equipped with a backup battery 318 to ensure that components such as the RTC are always powered. The backup battery 318 is also crucial for supplying power to the AED device 100 while the battery is being serviced (e.g., replaced).

[0073] The BIST sequence also verifies the functionality of the RAM and SD card 320. The primary purpose of the SD card 320 is to hold information relating to the status of the AED device 100 and any specific parts requiring maintenance service. According to an exemplary embodiment, the SD card 320 is easily removable and uploads all status information for the AED device 100 to a computer. This upload allows the user to easily identify whether the AED device 100 requires maintenance service, and if so, which parts and / or systems require maintenance service.

[0074] Furthermore, according to another exemplary embodiment, the microphone 316 can also record ambient sounds while the device is in use. Therefore, the AED device 100, or more specifically, the SD card, must have sufficient storage capacity to retain this audio data. This data can be used to provide forensic information about any failed resuscitation attempts.

[0075] The BIST sequence also implicitly verifies the functionality of microprocessor 602. More specifically, if microprocessor 602 is unresponsive during any of the aforementioned tasks, it is not functioning properly. In such cases, a secondary microprocessor takes over a limited number of processing functions. In particular, the secondary microprocessor will initiate an appropriate warning sequence to inform the user that maintenance service is required.

[0076] As used herein, the term “about” means plus or minus 10% of the numerical value in which it is used.

[0077] While this disclosure has been described with reference to several exemplary embodiments, it will be understood by those skilled in the art that this disclosure is not limited to such disclosed embodiments. Conversely, the disclosed embodiments can be modified to incorporate any number of variations, changes, substitutions, or equivalent configurations not described herein, but these are within the scope of this disclosure.

Claims

1. An automated external defibrillator (AED) device, A high-voltage capacitor (HV Cap) configured to store the energy required to deliver a defibrillating shock to a patient, One or more batteries configured to charge the HV Cap, A DC / DC converter circuit including a high-voltage transformer (HV XFMR), a field-effect transistor (FET) switch with associated drivers, and rectifier diodes, An H-bridge circuit configured to convert the energy released from the HV Cap into a two-phase pulse, The AED device comprises a memory and a microprocessor configured to store and execute computer executable instructions for the operation of the AED device, The HV Cap, the DC / DC converter circuit, the H-bridge circuit, the one or more batteries, and the memory and the microprocessor are housed in a pocket-sized housing. An automated external defibrillator (AED) device wherein the microprocessor is configured to simultaneously monitor the discharge current and temperature of one or more batteries so as not to exceed (i) the maximum discharge rate of one or more batteries and (ii) the maximum operating temperature of one or more batteries, and to adjust the charging rate of the HV Cap, thereby enabling the HV Cap to be charged at the maximum possible speed with available battery power without exceeding the maximum allowable discharge current or maximum allowable temperature of one or more batteries.

2. The AED according to claim 1, wherein the DC / DC converter circuit is configured to increase the battery voltage to approximately 2000 volts.

3. A pair of defibrillator pads, The AED according to claim 1 or 2, further comprising a cable for operably connecting the HV Cap to the pair of defibrillator pads, wherein the defibrillator pads are pocket-sized.

4. The AED device according to any one of claims 1 to 3, wherein the pocket-sized housing has dimensions of 155 mm x 86 mm x 28 mm or less.

5. The AED device according to any one of claims 1 to 4, wherein the one or more batteries consist of four CR2 batteries.

6. The AED device according to any one of claims 1 to 5, wherein the HV Cap is configured to start charging when the AED device is powered on.

7. The AED device according to claim 1, wherein the maximum discharge rate is 1000 mA and the maximum operating temperature is 75°C.

8. The AED device according to any one of claims 1 to 7, further comprising a real-time clock (RTC) and a temperature sensor integrated circuit (temperature sensor IC), each configured to power on the AED device according to dynamic parameters programmed into the RTC and the temperature sensor IC, and the microprocessor configured to be completely powered off (rather than in sleep mode) when the AED device is not in use.

9. The AED device according to claim 8, wherein when the AED device is not in use, all circuits and components are powered off, except for the RTC, the temperature sensor IC, and their supporting circuits.

10. The AED device according to claim 8 or 9, wherein the RTC is configured to periodically power on the microprocessor and perform a series of built-in self-tests (BISTs) to check one or more batteries and hardware of the AED device.

11. The AED device according to any one of claims 8 to 10, further comprising a speaker housed within the pocket-sized housing and configured to provide voice prompts to the user.

12. The AED device according to claim 11, further comprising a microphone disposed near the speaker in the pocket-sized housing, the RTC being configured to periodically power on at least one computer processor to perform a BIST on which a signal is transmitted from the computer processor through the speaker, the computer processor evaluating the integrity of the speaker by comparing the transmitted signal with the signal received through the microphone.

13. The AED device according to claim 12, wherein, during use, the AED device is configured to record audio received by the microphone during the operation of the AED device, and has an external flash memory for storing the audio received by the microphone during the operation of the AED device.

14. The AED device according to claim 8 or 9, wherein the temperature sensor IC is configured to continuously monitor the temperature of the AED device, including when the power to other parts of the AED device circuit is turned off.

15. The AED device according to any one of claims 8 to 10, further comprising: (i) a low-power microcontroller that is periodically powered on by a signal from the RTC; (ii) monitors the temperature of the pocket-sized housing and / or the defibrillator pads; and (iii) is configured to power on the microprocessor to warn if the monitored temperature falls outside a specified temperature range.

16. The AED device according to any one of claims 1 to 15, comprising a variable frequency relaxation oscillator circuit configured to acquire Z-body measurements, wherein the circuit is effective in self-oscillating at a frequency proportional to the patient's body impedance.

17. The AED device according to any one of claims 1 to 16, wherein the microprocessor is configured to verify the integrity of the defibrillator pads and cables.

18. The AED device according to any one of claims 1 to 17, wherein the microprocessor is configured to verify the integrity of the electrocardiogram (ECG) circuit within the AED device.

19. The AED device according to claim 18, wherein the microprocessor is configured to periodically generate a signal that simulates a heartbeat, input the signal to an analog front-end (AFE) circuit, and then compare the input signal with a signal processed by the AFE circuit.

20. The AED device according to any one of claims 1 to 19, wherein the pocket-sized housing has a surface having a single button which is a power-on button.

21. The microprocessor accesses the memory, The ECG of the patient is read and analyzed to determine whether the patient has a cardiac rhythm that can be affected by shock. Charging the aforementioned HV Cap, Determining the discharge current for the defibrillation shock based at least partially on the Z-body measurements of the patient, The defibrillation shock described above, It is configured to execute computer executable instructions to do so, The automated external defibrillator (AED) device according to claim 1, comprising a variable frequency relaxation oscillator circuit configured to acquire the patient's Z-body measurement, wherein the circuit is effective in self-oscillating at a frequency proportional to the patient's body impedance.

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