Patent Description:
Patient physiological signal simulation is commonly used in the medical community (e.g. manufacturers, hospitals, research facilities) to reproduce real-life scenarios for creating new devices and algorithms, or as training tools for physicians and/or paramedics to acquire realistic experience in a controlled environment. In the realm of electrocardiogram (ECG) signals, Automatic External Defibrillator (AED) manufacturers obtain field data from their distributed AEDs, but the collected data is often corrupted or noisy. This noise and/or corruption may be caused by numerous factors, such as patients' physiological status, environment factors, pad imbalance, etc. In addition, acquiring such patient data may require a high degree of administrative work.

Currently, AED users, mainly paramedics and emergency medical personnel, often ignore voice prompts from the device because of either a conflict between the AED audio instruction and their current medical practices or confusion with the use of the device. Thus, AED users continue to perform CPR during an analyzing period. As a result, the ECG analysis algorithm may not accurately identify the ECG rhythm and consequently delays defibrillation therapy. This delay can significantly impact patient survival rate and recovery. Moreover, it is difficult to generate and collect sample data, and the collected data usually contain undesired artifacts, adding levels of sophistication and impeding the development of algorithms.

There have been efforts in developing more realistic biosignals during CPR, but such signals have been digitally simulated. Digital simulation typically ignores some of the stochastic nature of the signal and reduces the realism of the signal. Therefore, there is a need for simulation devices that can accurately and consistently replicate ECG and impedance signals undergoing physiological changes due to CPR.

<CIT> discloses a dimmer switch including a rotary potentiometer.

<CIT> discloses a system including a chest compression sensor configured to detect at least one parameter corresponding to chest compression of a subject and an electrocardiogram signal generator configured to generate a simulated electrocardiogram signal. <CIT> discloses a manikin and control system for use by a student practicing a procedure normally applied to the human body, such as cardiopulmonary resuscitation.

The invention provides an electromechanical system according to claim <NUM>. The present disclosure further provides examples directed to CPR-artifact simulation systems, methods, and apparatus. These systems may serve as usability-testing tools for new algorithms by contaminating simulated ECG signals in a manner representative of how CPR changes a body's thoracic impedance. Currently, heart-rhythm simulation devices may generate a large variety of noise-free ECG waveforms. However, a robust algorithm requires corrupted signals that closely resemble real-life situations. The disclosed systems can generate both corrupted ECG signals and impedance signals, resembling all possible signals by the AED. Furthermore, by using only analog systems, this invention can produce realistic CPR corrupted ECG signals that physically correlate with the impedance signal being recorded on the system. Additionally, the disclosed analog systems provide greater versatility than corresponding digital systems. The analog systems may be implemented with other simulation systems, simulation devices, or manikins without the complexity of digital interfacing, as analog interfacing may be achieved through a simple adapter.

Generally, in one aspect of the disclosure an electrical system, method, and apparatus for generating a CPR-corrupted ECG signal is provided. The electrical system may include an ECG signal generator electrically coupled to a first contact of an AED. The electrical system may further include a backend circuit. The backend circuit may include a potentiometer. The potentiometer may be electrically coupled to the ECG signal generator and a second contact of the AED. A user input is configured to adjust an impedance of the potentiometer.

According to an example, the backend circuit may further include a divider impedance circuit electrically coupled to the potentiometer. The divider impedance circuit may form a voltage divider circuit with the potentiometer. The backend circuit may further include a reference voltage circuit electrically coupled to the divider impedance circuit and the potentiometer.

According to an example, the divider impedance circuit may include one or more resistors.

According to an example, the reference voltage circuit may include a DC voltage source.

According to an example, the reference voltage circuit may further include a regulator circuit. The regulator circuit may be a Zener diode shunt regulator circuit.

According to an example, the backend circuit may further comprise a potentiometer adjustment circuit electrically coupled in parallel to the potentiometer. The potentiometer adjustment circuit may include one or more resistors.

Generally, in another aspect of the disclosure, an electromechanical system, method, and apparatus for generating a CPR-corrupted ECG signal is provided. The electromechanical system may include an ECG signal generator electrically coupled to a first contact of an AED. The electromechanical system may further include a backend circuit. The backend circuit may include a potentiometer. The potentiometer may be electrically coupled to the ECG signal generator and a second contact of the AED. The electromechanical system, method, or apparatus may further include a compression mechanism. The compression mechanism may be configured to receive a vertical force. The compression mechanism may also be configured to adjust an impedance of the potentiometer according to the vertical force.

According to an example, the compression mechanism may include a rack having a plurality of teeth and an initial position. The rack may be configured to translate to a second position according to the vertical force. The compression mechanism may further include a gear with a plurality of teeth engaged with the teeth of the rack such that the gear rotates according to the translation of the rack.

According to an example, the rack may be configured to translate from the second position to the initial position after the application of the vertical force.

According to an example, the potentiometer may be a rotary potentiometer having a shaft coupled to the gear such that the rotation of the gear adjusts the impendence of the potentiometer.

Generally, in another of the disclosure, an electromechanical system, method, and apparatus for adjusting the impedance of a circuit is provided. The electromechanical system may include a potentiometer. The electromechanical system may include a compression mechanism. The compression mechanism may be configured to receive a vertical force. The compression mechanism may be further configured to adjust the impedance of the potentiometer according to the vertical force.

According to an example, the compression mechanism may include a rack having a plurality of teeth and an initial position. The rack may be configured to translate according to the vertical force. The compression mechanism may further include a gear with a plurality of teeth engaged with the teeth of the rack such that the gear rotates according to the translation of the rack.

Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the various embodiments.

The present disclosure describes various embodiments for systems for simulating CPR corruption of ECG signals. More generally, Applicant has recognized and appreciated that it would be beneficial to provide systems to generate CPR-corrupted ECG signals using an electromechanical device to model CPR administered by a first responder. These systems may be used as a usability testing tool to validate new defibrillator algorithms, functionality, or systems by (<NUM>) recognizing the rate, depth, onset, and offset for CPR, (<NUM>) analyzing corrupted ECG rhythms during CPR, and (<NUM>) evaluating CPR quality. These systems may also be used to enhance functionality and quality of a manikin product for medical training and usability testing by providing a CPR-corrupted ECG signal and a thoracic impedance signal as feedback that correlates with how the CPR is being performed.

Referring to <FIG>, in a one aspect, an electrical system <NUM> for generating a CPR-corrupted ECG signal is provided. The electrical system <NUM> may include an ECG signal generator <NUM> electrically coupled to a first contact <NUM> of an AED <NUM>. The ECG signal <NUM> generator may have an internal impedance of <NUM> ohms.

The electrical system <NUM> may further include a backend circuit <NUM>. The backend circuit <NUM> may include a potentiometer <NUM>. Potentiometer <NUM> is shown in <FIG> as R2. The potentiometer <NUM> may be electrically coupled to the ECG signal generator <NUM> and a second contact <NUM> of the AED <NUM>. The potentiometer <NUM> may be a rotary potentiometer. In further examples, the potentiometer <NUM> may be a sliding potentiometer.

A user input <NUM> is configured to adjust an impedance of the potentiometer <NUM>. In an example explained in greater detail below, the user input <NUM> may be downward thrust as would be performed by a first responder during CPR. A device, such as a compression mechanism <NUM> described in greater detail below, may then adjust the impedance of the rotary potentiometer by actuating its shaft. The potentiometer <NUM> may have an impedance range from <NUM> to <NUM> ohms. In one example, and as shown in <FIG>, the potentiometer <NUM> is set to <NUM> ohms. In one example, the impendence of the potentiometer <NUM> and its related circuitry is adjusted such that an impedance signal of the backend circuit <NUM> has a baseline of <NUM> ohms and an oscillation range of <NUM> ohms.

According to an example, the backend circuit <NUM> may further include a divider impedance circuit <NUM> electrically coupled to the potentiometer <NUM>. The divider impedance circuit <NUM> may include one or more resistors. The one or more resistors may in serial and/or parallel configuration. As shown in <FIG>, the divider impendence circuit <NUM> may be R1, a <NUM> ohm resister. The divider impedance circuit <NUM> may form a voltage divider circuit <NUM> with the potentiometer <NUM>.

The backend circuit <NUM> may further include a reference voltage circuit <NUM> electrically coupled to the divider impedance circuit <NUM> and the potentiometer <NUM>. The reference voltage circuit <NUM> may include a DC voltage source. The reference voltage circuit may further include a regulator circuit <NUM>. The regulator circuit may be a Zener diode shunt regulator circuit. In an example shown in <FIG>, DC voltage source V1 provides a voltage of <NUM> V. The Zener diode shunt circuit includes a single Zener diode D. D, embodied as Linear Technology part number LT1004-<NUM>, has a reverse breakdown voltage of <NUM> V. Thus, arranged as a Zener diode shunt regulator, D maintains the output voltage of reference voltage circuit <NUM> as approximately <NUM> V. The regulator circuit <NUM> of <FIG> further includes current limiting resistor R6. In this example, R6 is set to <NUM> ohms.

According to an example, the backend circuit may further comprise a potentiometer adjustment circuit <NUM> electrically coupled in parallel to the potentiometer <NUM>. The potentiometer adjustment circuit <NUM> may include one or more resistors. In the example shown in <FIG>, the potentiometer adjustment circuit <NUM> is embodied as resister R3 with an impedance of <NUM> ohms. Modifying the impedance of the potentiometer adjust circuit <NUM> allows for greater control of the overall impedance of the backend circuit <NUM> as controlled by the potentiometer <NUM>. In other examples, the potentiometer <NUM> may be a plurality of resistors in a series and/or parallel configuration.

In a further example, the electrical system <NUM> may further include an overvoltage circuit to protect the backend circuit <NUM> during the application of electric shock in defibrillation. In an example, the overvoltage circuit may include a gas discharge tube (GDT) and/or a transient voltage suppressor (TVS). In the event of delivering an electric shock into the system, the GDT and/or TVS may be activated to shunt excess transient current back to the AED <NUM> to reduce excess current in the backend circuit <NUM>. In an example, the ECG signal generator <NUM> may be designed to withstand normal defibrillation without damage to its internal components. In this way, the ECG signal generator <NUM> may be used to reduce the electrical load on the other electrical components of the circuit.

As described above, <FIG> shows a sample circuit diagram for the electrical system <NUM>. The resister values shown for R1-R6 are example values used in a prototype of the electrical system <NUM>. A person having ordinary skill in the art would appreciate that other resister values may be possible, or even preferred, depending on the application. As the R2 resistance value changes according to the setting of the potentiometer <NUM>, the overall impedance change of the system <NUM> may be calculated using equation <NUM> below:
<MAT>.

Further, the change in the output voltage level of the system <NUM> may be calculated as equation <NUM> below:
<MAT>.

Referring to <FIG>, generally, in another aspect, an electromechanical system <NUM> for generating a CPR-corrupted ECG signal is provided. The electromechanical system <NUM> may include an ECG signal generator <NUM> electrically coupled to a first contact <NUM> of an AED <NUM>.

The electromechanical system <NUM> may further include a backend circuit <NUM>. The backend circuit <NUM> may include a potentiometer <NUM>. The potentiometer <NUM> may be electrically coupled to the ECG signal generator <NUM> and a second contact <NUM> of the AED <NUM>.

The electromechanical system <NUM> may further include a compression mechanism <NUM>. The compression mechanism <NUM> may be configured to receive a vertical force, such as a downward thrust as would be performed by a first responder during CPR. The compression mechanism <NUM> may also be configured to adjust an impedance of the potentiometer <NUM> according to the vertical force.

Referring to <FIG>, the compression mechanism <NUM> may include a rack <NUM> having a plurality of teeth <NUM> and an initial position. The rack <NUM> may be configured to translate to a second position according to the vertical force. The compression mechanism <NUM> may further include a gear <NUM> with a plurality of teeth <NUM> engaged with the teeth <NUM> of the rack <NUM> such that the gear <NUM> rotates according to the translation of the rack <NUM>.

According to an example, the potentiometer <NUM> may be a wire-wound, rotary potentiometer having a shaft <NUM> coupled to the gear <NUM> such that the rotation of the gear <NUM> adjusts the impendence of the potentiometer <NUM>. The potentiometer <NUM> may have a rotational range of <NUM> degrees. In an example configuration, a <NUM> translation of the rack <NUM> may result in <NUM> ohm of impedance change due to rotation of the shaft <NUM> of the potentiometer <NUM>. The amount of impedance change per distance of rack translation may be controlled by a variety of factors including, but not limited to, the diameter of the gear <NUM>, the impedance range of the potentiometer <NUM>, and/or the impedance of the potentiometer adjustment circuit <NUM>.

To facilitate the rotation of the shaft <NUM> of the potentiometer <NUM>, the potentiometer <NUM> may sit in a potentiometer holder, as shown in <FIG>. As further shown in <FIG>, the rack <NUM> may include a slider configured to engage with a slot in the potentiometer holder. This configuration may provide proper alignment of the components of the compression mechanism <NUM>, including the potentiometer <NUM>, gear <NUM>, and rack <NUM>. These components may be produced via 3D printing, and may be composed of polylactic acid (PLA). In other examples, nylon may be used to reduce friction between the components.

The rack <NUM> may be further configured to translate from the second position to the initial position after the application of the vertical force. This reflex response may be configured to mimic decompression of the human thorax during CPR following a downward thrust. In other embodiments, the rack <NUM> may be configured to translate from the second position to a third position, wherein the third position differs from the initial position.

According to an example, the backend circuit <NUM> may further include a divider impedance circuit <NUM> electrically coupled to the potentiometer <NUM>. The divider impedance circuit <NUM> may form a voltage divider circuit <NUM> with the potentiometer <NUM>. The backend circuit <NUM> may further include a reference voltage circuit <NUM> electrically coupled to the divider impedance circuit <NUM> and the potentiometer <NUM>.

Referring to <FIG>, generally, in another aspect, an electromechanical system <NUM> for adjusting the impedance of a circuit is provided. The electromechanical system <NUM> may include a potentiometer <NUM>. The electromechanical system <NUM> may include a compression mechanism <NUM>. The compression mechanism <NUM> may be configured to receive a vertical force. The compression mechanism <NUM> may be further configured to adjust the impedance of the potentiometer <NUM> according to the vertical force. The compression mechanism <NUM> may include a rack <NUM> having a plurality of teeth <NUM> and an initial position. The rack <NUM> may be configured to translate according to the vertical force. The compression mechanism <NUM> may further include a gear <NUM> with a plurality of teeth <NUM> engaged with the teeth <NUM> of the rack <NUM> such that the gear <NUM> rotates according to the translation of the rack <NUM>.

According to an example, the potentiometer <NUM> may be a wire-wound, rotary potentiometer having a shaft <NUM> coupled to the gear <NUM> such that the rotation of the gear <NUM> adjusts the impendence of the potentiometer <NUM>. The potentiometer <NUM> may have a rotational angle of <NUM> degrees.

The electromechanical system <NUM> may be configured to be installed in a manikin. Rack <NUM> may be clipped onto a plastic arch of a rib-piece of the manikin. When a user performs CPR on the manikin, the rib-piece and plastic arch may be pushed down so as to also slide the rack <NUM> down the potentiometer holder. The potentiometer holder may be secured in the manikin using epoxy.

To protect the potentiometer <NUM> from over-rotation, the electromechanical system <NUM> does not utilize the full rotation of the rotary potentiometer. In one example, the compression system <NUM> allows for <NUM> degree rotation of the gear <NUM> and the shaft <NUM> of the potentiometer <NUM>.

Referring to <FIG>, generally, in another aspect, a further example of an electrical system <NUM> for generating a CPR-corrupted ECG signal is provided. <FIG> shows a schematic diagram for the further system <NUM>. An AED or defibrillator <NUM> performing ECG analysis is found on the right side of <FIG>. Without the system <NUM>, the AED <NUM> would be connected directly to a Defibrillator Analyzer <NUM>, which presents a cardiac rhythm voltage source in series with a patient resistance. Some defibrillator analyzers <NUM> are designed to be shockable by the AED <NUM> as well.

The system <NUM> is connected in series with a defibrillator analyzer <NUM> in order to sum voltage and resistance variations into a signal from the defibrillator analyzer <NUM> seen by the AED <NUM>. With a standard <NUM> inch CPR compression stroke on a CPR mannequin chest, the system <NUM> shown is designed to add <NUM> mV peak-to-peak to the signal from the defibrillator analyzer <NUM>, with the added voltage dependent on the instantaneous depth of a CPR compression stroke. The system <NUM> shown is also designed to add <NUM> ohm peak-to-peak to the resistance presented by the defibrillator analyzer <NUM>, with an analogous dependence on the CPR stroke. The voltage and resistance variations are designed to be correlated.

As described above, the means of conversion of mechanical motion of the CPR mannequin chest to an electrical variation is by way of a potentiometer <NUM>. The instantaneous resistance value of the potentiometer <NUM>, in parallel with another passive resistor <NUM> to lower the overall resistance value, serves as both the direct resistance variation of the system <NUM>, and also as part of a voltage divider, which divides a reference voltage by a (relatively large) ratio to provide the system <NUM> voltage variation. As shown in <FIG>, a rack and pinion style gear mechanism may be used to convert the linear motion of the mannequin chest to rotary motion of the potentiometer <NUM>. The design values, using a potentiometer variation from <NUM> ohms to <NUM> ohms in parallel with a fixed <NUM> ohm resistance, results in a non-linear overall variation in resistance, with a slower variation over the higher end of the potentiometer <NUM> in comparison with the lower end deeper in the compression stroke. This may be partially compensated for by adjustments to the mechanical rack and pinion mechanism, for example, by offsetting the center of the "pinion" gear element on the potentiometer shaft, in order to provide more rotation during the early part of the compression stroke in comparison with the later part.

The system <NUM> also includes protection from a shock delivered by the AED <NUM> to the series connection of the defibrillator analyzer <NUM> and the system <NUM>. The protection is in the form of shunt anti-parallel diodes <NUM>, for bidirectional protection. The shunt diodes <NUM> are intended to divert a high current defibrillation pulse from the remainder of the system <NUM>, while clamping the voltage seen by the remaining circuit to the peak forward voltage of the diodes <NUM> during the pulse. In normal operation (rather than during a shock event), the voltage and resistance across the shunt diodes <NUM> is very low, and so the shunt diodes <NUM> have negligible impact on the system <NUM>.

Selection of specific appropriate diodes <NUM> may be left to a user, beyond guidance that the diodes <NUM> must be capable of handling the peak defibrillation current and overall defibrillation current pulse, and must be fast enough to conduct the defibrillation current pulse without excess instantaneous voltage during the pulse.

Referring to <FIG>, generally, in another aspect, a method <NUM> for generating a CPR-corrupted ECG signal is provided. The method <NUM> may include the step of providing <NUM> an ECG circuit including an ECG signal generator and a potentiometer. The method may include the step of generating <NUM>, via the ECG signal generator, an ECG signal. The method may further include the step of applying <NUM>, by a user, a vertical force to a compression mechanism coupled to the potentiometer. The method may further include the step of rotating <NUM>, via the compression mechanism, a shaft of the potentiometer. The method may further include the step of adjusting <NUM>, via the rotation of the shaft of the potentiometer, an impedance of the potentiometer.

It should also be understood that, unless clearly indicated to the contrary, in any non-claimed methods disclosed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.

Claim 1:
An electromechanical system (<NUM>) for generating a cardiac-pulmonary resuscitation (CPR)-corrupted electrocardiogram (ECG) signal, comprising:
an ECG signal generator (<NUM>) configured to be electrically coupled to a first contact (<NUM>) of an automated external defibrillator (AED) (<NUM>); and
a backend circuit (<NUM>), characterized in that the backend circuit (<NUM>) further comprises a potentiometer (<NUM>) electrically coupled to the ECG signal generator (<NUM>) and configured to be electrically coupled to a second contact (<NUM>) of the AED (<NUM>); and
a compression mechanism (<NUM>) configured to:
receive a vertical force; and
adjust an impedance of the potentiometer (<NUM>) according to the vertical force;
wherein the compression mechanism comprises:
a rack (<NUM>) having a plurality of teeth (<NUM>) and an initial position, wherein the rack (<NUM>) is configured to translate to a second position according to the vertical force; and
a gear (<NUM>) with a plurality of teeth (<NUM>) engaged with the teeth (<NUM>) of the rack (<NUM>) such that the gear (<NUM>) rotates according to the translation of the rack (<NUM>);
and
wherein the potentiometer (<NUM>) is a rotary potentiometer having a shaft (<NUM>) coupled to the gear (<NUM>) such that the rotation of the gear (<NUM>) adjusts the impedance of the potentiometer (<NUM>), thereby generating a cardiac-pulmonary resuscitation (CPR)-corrupted electrocardiogram (ECG) signal.