- Email: [email protected]
A TASER conducted electrical weapon with cardiac biomonitoring capability: Proof of concept and initial human trial
Journal of Forensic and Legal Medicine 43 (2016) 48e52
Contents lists available at ScienceDirect
Journal of Forensic and Legal Medicine j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j fl m
A TASER conducted electrical weapon with cardiac biomonitoring capability: Proof of concept and initial human trial Jason P. Stopyra a, *, Samuel I. Ritter a, Jennifer Beatty a, James C. Johnson a, Douglas M. Kleiner b, James E. Winslow III a, Alison R. Gardner a, William P. Bozeman a a b
Department of Emergency Medicine, Wake Forest University School of Medicine, Winston Salem, NC, USA Tactical Medics International, Jacksonville Beach, FL, USA
a r t i c l e i n f o
a b s t r a c t
Article history: Received 28 December 2015 Received in revised form 11 June 2016 Accepted 3 July 2016 Available online 5 July 2016
Introduction: Despite research demonstrating the overall safety of Conducted Electrical Weapons (CEWs), commonly known by the brand name TASER®, concerns remain regarding cardiac safety. The addition of cardiac biomonitoring capability to a CEW could prove useful and even lifesaving in the rare event of a medical crisis by detecting and analyzing cardiac rhythms during the period immediately after CEW discharge. Objective: To combine an electrocardiogram (ECG) device with a CEW to detect and store ECG signals while still allowing the CEW to perform its primary function of delivering an incapacitating electrical discharge. Methods: This work was performed in three phases. In Phase 1 standard law enforcement issue CEW cartridges were modified to demonstrate transmission of ECG signals. In Phase 2, a miniaturized ECG recorder was combined with a standard issue CEW and tested. In Phase 3, a prototype CEW with onboard cardiac biomonitoring was tested on human volunteers to assess its ability to perform its primary function of electrical incapacitation. Results: Bench testing demonstrated that slightly modified CEW cartridge wires transmitted simulated ECG signals produced by an ECG rhythm generator and from a human volunteer. Ultimately, a modified CEW incorporating ECG monitoring successfully delivered incapacitating current to human volunteers and successfully recorded ECG signals from subcutaneous CEW probes after firing. Conclusion: An ECG recording device was successfully incorporated into a standard issue CEW without impeding the functioning of the device. This serves as proof-of-concept that safety measures such as cardiac biomonitoring can be incorporated into CEWs and possibly other law enforcement devices. © 2016 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.
Keywords: TASER CEW Biomonitor ECG EKG
1. Introduction Conducted electrical weapons (CEWs), commonly known by the brand name TASER®, are commonly used by law enforcement officers to subdue and apprehend suspects who are actively resisting or threatening officers or others, but do not represent a lethal threat. Research has shown that serious injury or death is extremely rare after use of these less lethal devices.1,2,14 However, isolated case reports of deaths occurring shortly after CEW use
* Corresponding author. Department of Emergency Medicine, Wake Forest University, School of Medicine, Medical Center Boulevard, Winston-Salem, NC, 27157, USA. E-mail address: [email protected] (J.P. Stopyra).
leave lingering questions of cardiac safety.3e5 These unexpected deaths after exposure to a CEW discharge remain rare, and are often intertwined with other risk factors for sudden death including exertion, drug use, and pre-existing medical conditions.6e8 A CEW delivers a series of low current, high voltage electrical impulses via two insulated wires attached to probes, which are propelled through the air and imbed themselves in a subject's skin or clothing.9 This combination of subcutaneous metal probes and insulated wires connected to an electronic device represents the basic components needed to obtain an electrocardiogram. This configuration makes it possible to detect and analyze the cardiac rate and rhythm of a suspect while the CEW remains attached. Such cardiac biomonitoring capability could prove useful and even lifesaving in the event of a medical crisis by detecting a suspect's cardiac rhythm during the period immediately after CEW
http://dx.doi.org/10.1016/j.jflm.2016.07.003 1752-928X/© 2016 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.
J.P. Stopyra et al. / Journal of Forensic and Legal Medicine 43 (2016) 48e52
49
Fig. 1. Artificially generated ECG signal recorded after successful deployment of a modified CEW cartridge.
Fig. 2. Surface ECG recorded from skin electrodes after successful deployment of a modified CEW cartridge.
Fig. 3. ECG tracing recorded from weapon-fired subcutaneous CEW probes at the posterior torso after successful discharge and function of a modified CEW cartridge.
discharge. Incorporation of real time analysis capability, which already exists in implanted cardiac devices, combined with a notification system could prompt nonmedical CEW users (law enforcement personnel) to obtain immediate medical assistance or apply an automatic external defibrillator (AED) if dangerous cardiac rhythms are detected. This could enhance subject safety whether the dangerous rhythm is related to the CEW discharge, a coexisting medical condition, or to another process such as drug overdose or Excited Delirium Syndrome.1,10e12 Further, a recording of the
cardiac rhythm at the time of collapse and death would be invaluable when investigating and determining the cause of rare in-custody deaths. We hypothesized that a combination of existing technologies would allow us to obtain interpretable electrocardiogram (ECG) tracings through minor modifications to a standard police issue CEW and cartridge. Our primary objective was to provide proof of this concept and then to combine a miniaturized ECG device with a standard CEW in order to test detection and storage of ECG signals
50
J.P. Stopyra et al. / Journal of Forensic and Legal Medicine 43 (2016) 48e52
Fig. 4. Custom mounting device with Implantable Loop Recorder (ILR) (top) and isolating switches (sides), in place on standard law enforcement issue Taser Model X26.
while still allowing the CEW to perform its primary function of delivering an incapacitating electrical discharge. 2. Methods In Phase 1, investigators modified commercial off the shelf Taser Model X26 cartridges (Taser International, Scottsdale, Arizona) to demonstrate proof-of-concept that ECG signals could be detected. The standard single-use CEW cartridges were partially disassembled by an electrical engineer to add soldered electrical connections to the probes and wires. A commercially available ECG signal generator (Tutor T Arrhythmia Generator, Pinnacle Technology Group, Inc. Ottawa Lake, MI) and two miniaturized ECG recorders (Omron Portable ECG Monitor HCG-801, Omron Healthcare, Inc., Lake Forest, IL and Merlin ECG Event Recorder, Meditech Inc., Budapest, Hungary) were used to detect and record ECG signals via the modified CEW probes and wires. Additional proof-ofconcept was provided by discharging the modified CEW cartridges to demonstrate continued ability of the cartridge to function
normally after the electrical modifications and by detecting ECG signals from human volunteers after discharge. In Phase 2, a prototype CEW with on-board cardiac biomonitoring combined a standard Taser Model X26 CEW (Taser International, Scottsdale, Arizona) with a miniature implantable loop recorder (ILR) (Reveal® XT, Medtronic Incorporated, Minneapolis, Minnesota). This ILR is approved by the Food and Drug Administration as a long term subcutaneously placed device. It automatically detects, interprets, and records abnormal cardiac rhythms. It can also be manually activated as an event recorder and is interrogated and programmed using proprietary equipment similar to other implanted cardiac devices. The ILR's contacts points were modified to allow connection to an external signal source. A custom mount was fabricated to externally attach the ILR and two high voltage-tolerant isolating switches (Model HM12-1A69, Meder Electronics, Wareham, MA) to the CEW without obstruction and to allow electrical connection with the modified CEW cartridges as previously developed. The prototype CEW was then tested to determine if it would discharge normally and if interpretable ECG signals could be recorded via the test apparatus. Lastly, in Phase 3, the modified cartridges and prototype CEW with on-board cardiac biomonitoring was tested on human volunteers to assess its ability to perform its primary function of electrical incapacitation. With approval by the institutional review board, a convenience sample of healthy adult volunteers was recruited from a class of law enforcement trainees who, as part of their CEW training, undergo a 5 s CEW exposure with probes deployed across the back of the torso. The only additional study intervention was ECG monitoring. Study exclusion criteria included allergies to ECG electrodes or adhesives. Written informed consent was obtained prior to testing. During testing simultaneous ECG recordings were obtained via standard leads and ECG electrodes at the anterior chest wall using as a surface ECG reference and the CEW-mounted ILR, with contact provided by the CEW probes and wires. The ILR was manually activated to initiate recording just prior to the training CEW exposure, allowing the anterior chest leads to record surface ECG signals before, during, and after the CEW discharge and the CEW-mounted ILR to record ECG signals after skin contact was made and the
Fig. 5. Generated ECG signal recorded by ILR mounted on prototype CEW after successful deployment of a modified CEW cartridge.
J.P. Stopyra et al. / Journal of Forensic and Legal Medicine 43 (2016) 48e52
51
Table 1 Demographics of volunteer subjects.
Age (years) Height (inches) Weight (pounds)
Mean
Range
31.5 69.5 213.5
21e50 65e74 136e250
outgoing CEW discharge was completed. After CEW discharge the ILRs were left in place for approximately 30 s before removal. Demographic data were collected including age, gender, height, and weight. Outcomes included successful CEW discharge, proper/ expected probe trajectory, successful delivery of an incapacitating electrical discharge and successful ECG recording. Probe trajectory and electrical incapacitation function were judged by direct observation by certified CEW instructors. ECG recordings were judged as successful if recordings obtained by the prototype CEW device could be interpreted with regard to heart rate, rhythm, and QRS morphology (narrow vs. wide) of 3 or more consecutive QRS complexes during the monitoring period after CEW discharge. ECG tracings were independently viewed and classified by two physician investigators. Data were entered into a commercially available spreadsheet program (Excel 2010, Microsoft Corporation, Redmond, WA) and descriptive analysis was performed. Confidence intervals of observed proportions were calculated using statistical analysis software (QuickCalcs, GraphPad Software Inc, La Jolla, CA). 3. Results In Phase 1, bench testing of the modified CEW cartridges demonstrated that the modified probes and wires could transmit simulated ECG signals produced by a rhythm generator. Further testing demonstrated unimpaired ability to discharge and deliver the probes at a static target. The discharged leads then successfully transmitted ECG signals from a rhythm generator (Fig. 1) and from surface electrodes placed on a human volunteer (Fig. 2). Finally, a modified CEW cartridge successfully delivered an incapacitating current to a human volunteer and then recorded an ECG signal from the CEW probes imbedded in the subcutaneous tissue of the volunteer's back (Fig. 3). Phase 2 involved mounting the technology onto a standard law enforcement issue CEW. An ILR was secured to the CEW via a custom fabricated mount (Fig. 4). Bench testing demonstrated the ability to discharge the CEW without impediment and for the ILR to record generated ECG signals via the modified CEW cartridges (Fig. 5). Phase 3 involved initial human testing of the prototype CEW with cardiac biomonitoring. A convenience sample of 6 law enforcement trainees were recruited. 5 of the 6 subjects (83%) were male. Additional demographics are shown in Table 1. The prototype CEW effectively deployed and delivered its intended discharge in all 6 subjects. The probe trajectory and placement was as expected in all subjects. ECG signals with 3 or more consecutive QRS complexes constituting an “interpretable” ECG as previously defined was clearly present in one of the cases, providing proof of concept (Fig. 6.). Other tracings were obscured by motion and artefactual noise. None of the subjects experienced any unexpected adverse effects from the exposure and all subjects continued with their training. 4. Discussion A rapidly expanding body of literature has defined the physiologic effects of CEW exposure in humans, and has to date revealed
Fig. 6. Simultaneous ECG tracings from anterior surface ECG reference (upper) and posterior CEW-mounted ILR (lower).
no life-threatening metabolic, respiratory, or cardiac effects with exposures up to 45 s.13 Despite these reassuring findings, there are ongoing concerns regarding possible cardiac rhythm disturbances from the electrical discharge of the CEW. Although a very low rate
52
J.P. Stopyra et al. / Journal of Forensic and Legal Medicine 43 (2016) 48e52
of significant injuries (0.25%) has been found in over 1200 field CEW uses by law enforcement personnel, cardiac complications continue to be a concern because of potential associated mortality.14 This work has demonstrated that ECG signals can be detected via standard law enforcement issue CEW probes and wires, providing proof-of-concept that it is possible to incorporate biomonitoring of cardiac rhythm into a CEW. Although the design had a low yield in providing identifiable ECG tracings, we were successful in demonstrating a sinus tachycardic rhythm in one subject. In the future, we would envision production and use of a combination CEW/ECG that incorporates existing miniaturized ECG technology internal to the CEW device with enhanced filtering to reduce artifacts and noise. In addition, it would include storage and downloading functions as well as user notification methods to alert non-medical law enforcement personnel of potential medical issues in real time. Audible alarms and visual signals indicating extreme tachycardia, ventricular fibrillation, or asystole could convey the potential urgency of the situation and guide nonmedical users to reassess subjects and to call for medical aid and/or apply an AED. Such a device could be used to provide biomonitoring of suspects after CEW use and rapid notification of police personnel of potential medical complications. The addition of respiratory rate monitoring by measurement of cyclic variations in impedance between ECG leads is also theoretically possible but not evaluated in this work. This technology is well developed and routinely incorporated into pre-hospital and hospital medical monitoring devices. Addition of these capabilities could increase suspect safety during and after the apprehension process and promote rapid activation of potentially life-saving medical care in rare instances of serious medical events. Partnerships between biomedical device manufacturers and less lethal weapon technology industries could benefit private companies, researchers, law enforcement agencies, and most importantly subjects who may be at risk for life threatening problems after CEW exposure. Similar capabilities could be incorporated into handcuffs or into a freestanding device with skin surface attachment for biomonitoring of suspects in police custody. 5. Limitations This work is an early demonstration and proof of concept. More development is required to have reliable, interpretable ECG recordings after exposure, and to incorporate additional features as discussed above. It is important to note that not all CEW uses result in sustained subcutaneous placement of both probes, which is a prerequisite for biomonitoring as discussed. 6. Conclusion ECG signals can be recorded via standard CEW probes and wires with minor modifications. Further, it is possible to combine an existing ECG analysis and storage device with the CEW without
negatively impacting its function. Incorporation of this type of biomonitoring into future law enforcement devices could increase safety and allow rapid treatment of suspects who may suffer a medical crisis while in police custody. Funding and acknowledgements This project was supported by Grants No. 2004-IJ-CX-K047 and 2006-DE-BX-K002 awarded by the National Institute of Justice, Office of Justice Programs, US Department of Justice. Points of view in the document are those of the authors and do not necessarily represent the official position or policies of the US Department of Justice. Phase 3 of this project was supported by an investigatorinitiated grant from the Medtronic Corporation, including Reveal® XT ILRs and technical support. The authors wish to acknowledge and thank Mt Airy North Carolina Police Department, Todd Lazarus, Jim Martin, Jackie Corino, Catherine Burgess and Travis Ardner for their valuable expertise and technical support. References 1. Vilke GM, DeBard ML, Chan TC, et al. Excited Delirium Syndrome (ExDS): defining based on a review of the literature. J Emerg Med. 2012;43:897e905. 2. Kroll MW, Lakkireddy D, Rahko, et al. Ventricular fibrillation risk estimation for conducted electrical weapons: critical convolutions. Conf Proc IEEE Eng Med Biol Soc. 2011;2011:271e277. 3. Sheridan RD. Letter by Sheridan regarding articles, “TASER electronic control devices can cause cardiac arrest in humans” and “TASER electronic control devices and cardiac arrests: coincidental or causal? Circulation. 2014;130:e167. 4. Kroll MW, Lakkireddy DR, Stone JR, Luceri RM. Response to letter regarding article, “TASER electronic control devices and cardiac arrests: coincidental or causal? Circulation. 2014;130:e168. 5. Zipes DP. Response to letter regarding article, “TASER electronic control devices can cause cardiac arrest in humans. Circulation. 2014;130:e169. 6. National Institute of Justice. Study of Deaths Following Electro Muscular Disruption; May 2011. https://www.ncjrs.gov/pdffiles1/nij/222981.pdf. 7. Ho JD, Heegaard WG, Dawes DM, Natarajan S, Reardon RF, Miner JR. Unexpected arrest-related deaths in america: 12 months of open source surveillance. West J Emerg Med. 2009;10:68e73. 8. Jauchem JR. Deaths in custody: are some due to electronic control devices (including TASER devices) or excited delirium? J Forensic Leg Med. 2010;17: 1e7. 9. Ho JD, Dawes DM, Chang RJ, Nelson RS, Miner JR. Physiologic effects of a newgeneration conducted electrical weapon on human volunteers. J Emerg Med. 2014;46:428e435. 10. Vilke GM, Payne-James J, Karch SB. Excited delirium syndrome (ExDS): redefining an old diagnosis. J Forensic Leg Med. 2012;19:7e11. 11. Vilke GM, Sloane C, Levine S, Neuman T, Castillo E, Chan TC. Twelve-lead electrocardiogram monitoring of subjects before and after voluntary exposure to the Taser X26. Am J Emerg Med. 2008;26:1e4. 12. Ho JD, Dawes DM, Bultman LL, et al. Respiratory effect of prolonged electrical weapon application on human volunteers. Acad Emerg Med. 2007;14:197e201. 13. Vilke GM, Bozeman WP, Chan TC. Emergency department evaluation after conducted energy weapon use: review of the literature for the clinician. J Emerg Med. 2011;40:598e604. 14. Bozeman WP, Hauda 2nd WE, Heck JJ, Graham Jr DD, Martin BP, Winslow JE. Safety and injury profile of conducted electrical weapons used by law enforcement officers against criminal suspects. Ann Emerg Med. 2009;53: 480e489.
Contents lists available at ScienceDirect
Journal of Forensic and Legal Medicine j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j fl m
A TASER conducted electrical weapon with cardiac biomonitoring capability: Proof of concept and initial human trial Jason P. Stopyra a, *, Samuel I. Ritter a, Jennifer Beatty a, James C. Johnson a, Douglas M. Kleiner b, James E. Winslow III a, Alison R. Gardner a, William P. Bozeman a a b
Department of Emergency Medicine, Wake Forest University School of Medicine, Winston Salem, NC, USA Tactical Medics International, Jacksonville Beach, FL, USA
a r t i c l e i n f o
a b s t r a c t
Article history: Received 28 December 2015 Received in revised form 11 June 2016 Accepted 3 July 2016 Available online 5 July 2016
Introduction: Despite research demonstrating the overall safety of Conducted Electrical Weapons (CEWs), commonly known by the brand name TASER®, concerns remain regarding cardiac safety. The addition of cardiac biomonitoring capability to a CEW could prove useful and even lifesaving in the rare event of a medical crisis by detecting and analyzing cardiac rhythms during the period immediately after CEW discharge. Objective: To combine an electrocardiogram (ECG) device with a CEW to detect and store ECG signals while still allowing the CEW to perform its primary function of delivering an incapacitating electrical discharge. Methods: This work was performed in three phases. In Phase 1 standard law enforcement issue CEW cartridges were modified to demonstrate transmission of ECG signals. In Phase 2, a miniaturized ECG recorder was combined with a standard issue CEW and tested. In Phase 3, a prototype CEW with onboard cardiac biomonitoring was tested on human volunteers to assess its ability to perform its primary function of electrical incapacitation. Results: Bench testing demonstrated that slightly modified CEW cartridge wires transmitted simulated ECG signals produced by an ECG rhythm generator and from a human volunteer. Ultimately, a modified CEW incorporating ECG monitoring successfully delivered incapacitating current to human volunteers and successfully recorded ECG signals from subcutaneous CEW probes after firing. Conclusion: An ECG recording device was successfully incorporated into a standard issue CEW without impeding the functioning of the device. This serves as proof-of-concept that safety measures such as cardiac biomonitoring can be incorporated into CEWs and possibly other law enforcement devices. © 2016 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.
Keywords: TASER CEW Biomonitor ECG EKG
1. Introduction Conducted electrical weapons (CEWs), commonly known by the brand name TASER®, are commonly used by law enforcement officers to subdue and apprehend suspects who are actively resisting or threatening officers or others, but do not represent a lethal threat. Research has shown that serious injury or death is extremely rare after use of these less lethal devices.1,2,14 However, isolated case reports of deaths occurring shortly after CEW use
* Corresponding author. Department of Emergency Medicine, Wake Forest University, School of Medicine, Medical Center Boulevard, Winston-Salem, NC, 27157, USA. E-mail address: [email protected] (J.P. Stopyra).
leave lingering questions of cardiac safety.3e5 These unexpected deaths after exposure to a CEW discharge remain rare, and are often intertwined with other risk factors for sudden death including exertion, drug use, and pre-existing medical conditions.6e8 A CEW delivers a series of low current, high voltage electrical impulses via two insulated wires attached to probes, which are propelled through the air and imbed themselves in a subject's skin or clothing.9 This combination of subcutaneous metal probes and insulated wires connected to an electronic device represents the basic components needed to obtain an electrocardiogram. This configuration makes it possible to detect and analyze the cardiac rate and rhythm of a suspect while the CEW remains attached. Such cardiac biomonitoring capability could prove useful and even lifesaving in the event of a medical crisis by detecting a suspect's cardiac rhythm during the period immediately after CEW
http://dx.doi.org/10.1016/j.jflm.2016.07.003 1752-928X/© 2016 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.
J.P. Stopyra et al. / Journal of Forensic and Legal Medicine 43 (2016) 48e52
49
Fig. 1. Artificially generated ECG signal recorded after successful deployment of a modified CEW cartridge.
Fig. 2. Surface ECG recorded from skin electrodes after successful deployment of a modified CEW cartridge.
Fig. 3. ECG tracing recorded from weapon-fired subcutaneous CEW probes at the posterior torso after successful discharge and function of a modified CEW cartridge.
discharge. Incorporation of real time analysis capability, which already exists in implanted cardiac devices, combined with a notification system could prompt nonmedical CEW users (law enforcement personnel) to obtain immediate medical assistance or apply an automatic external defibrillator (AED) if dangerous cardiac rhythms are detected. This could enhance subject safety whether the dangerous rhythm is related to the CEW discharge, a coexisting medical condition, or to another process such as drug overdose or Excited Delirium Syndrome.1,10e12 Further, a recording of the
cardiac rhythm at the time of collapse and death would be invaluable when investigating and determining the cause of rare in-custody deaths. We hypothesized that a combination of existing technologies would allow us to obtain interpretable electrocardiogram (ECG) tracings through minor modifications to a standard police issue CEW and cartridge. Our primary objective was to provide proof of this concept and then to combine a miniaturized ECG device with a standard CEW in order to test detection and storage of ECG signals
50
J.P. Stopyra et al. / Journal of Forensic and Legal Medicine 43 (2016) 48e52
Fig. 4. Custom mounting device with Implantable Loop Recorder (ILR) (top) and isolating switches (sides), in place on standard law enforcement issue Taser Model X26.
while still allowing the CEW to perform its primary function of delivering an incapacitating electrical discharge. 2. Methods In Phase 1, investigators modified commercial off the shelf Taser Model X26 cartridges (Taser International, Scottsdale, Arizona) to demonstrate proof-of-concept that ECG signals could be detected. The standard single-use CEW cartridges were partially disassembled by an electrical engineer to add soldered electrical connections to the probes and wires. A commercially available ECG signal generator (Tutor T Arrhythmia Generator, Pinnacle Technology Group, Inc. Ottawa Lake, MI) and two miniaturized ECG recorders (Omron Portable ECG Monitor HCG-801, Omron Healthcare, Inc., Lake Forest, IL and Merlin ECG Event Recorder, Meditech Inc., Budapest, Hungary) were used to detect and record ECG signals via the modified CEW probes and wires. Additional proof-ofconcept was provided by discharging the modified CEW cartridges to demonstrate continued ability of the cartridge to function
normally after the electrical modifications and by detecting ECG signals from human volunteers after discharge. In Phase 2, a prototype CEW with on-board cardiac biomonitoring combined a standard Taser Model X26 CEW (Taser International, Scottsdale, Arizona) with a miniature implantable loop recorder (ILR) (Reveal® XT, Medtronic Incorporated, Minneapolis, Minnesota). This ILR is approved by the Food and Drug Administration as a long term subcutaneously placed device. It automatically detects, interprets, and records abnormal cardiac rhythms. It can also be manually activated as an event recorder and is interrogated and programmed using proprietary equipment similar to other implanted cardiac devices. The ILR's contacts points were modified to allow connection to an external signal source. A custom mount was fabricated to externally attach the ILR and two high voltage-tolerant isolating switches (Model HM12-1A69, Meder Electronics, Wareham, MA) to the CEW without obstruction and to allow electrical connection with the modified CEW cartridges as previously developed. The prototype CEW was then tested to determine if it would discharge normally and if interpretable ECG signals could be recorded via the test apparatus. Lastly, in Phase 3, the modified cartridges and prototype CEW with on-board cardiac biomonitoring was tested on human volunteers to assess its ability to perform its primary function of electrical incapacitation. With approval by the institutional review board, a convenience sample of healthy adult volunteers was recruited from a class of law enforcement trainees who, as part of their CEW training, undergo a 5 s CEW exposure with probes deployed across the back of the torso. The only additional study intervention was ECG monitoring. Study exclusion criteria included allergies to ECG electrodes or adhesives. Written informed consent was obtained prior to testing. During testing simultaneous ECG recordings were obtained via standard leads and ECG electrodes at the anterior chest wall using as a surface ECG reference and the CEW-mounted ILR, with contact provided by the CEW probes and wires. The ILR was manually activated to initiate recording just prior to the training CEW exposure, allowing the anterior chest leads to record surface ECG signals before, during, and after the CEW discharge and the CEW-mounted ILR to record ECG signals after skin contact was made and the
Fig. 5. Generated ECG signal recorded by ILR mounted on prototype CEW after successful deployment of a modified CEW cartridge.
J.P. Stopyra et al. / Journal of Forensic and Legal Medicine 43 (2016) 48e52
51
Table 1 Demographics of volunteer subjects.
Age (years) Height (inches) Weight (pounds)
Mean
Range
31.5 69.5 213.5
21e50 65e74 136e250
outgoing CEW discharge was completed. After CEW discharge the ILRs were left in place for approximately 30 s before removal. Demographic data were collected including age, gender, height, and weight. Outcomes included successful CEW discharge, proper/ expected probe trajectory, successful delivery of an incapacitating electrical discharge and successful ECG recording. Probe trajectory and electrical incapacitation function were judged by direct observation by certified CEW instructors. ECG recordings were judged as successful if recordings obtained by the prototype CEW device could be interpreted with regard to heart rate, rhythm, and QRS morphology (narrow vs. wide) of 3 or more consecutive QRS complexes during the monitoring period after CEW discharge. ECG tracings were independently viewed and classified by two physician investigators. Data were entered into a commercially available spreadsheet program (Excel 2010, Microsoft Corporation, Redmond, WA) and descriptive analysis was performed. Confidence intervals of observed proportions were calculated using statistical analysis software (QuickCalcs, GraphPad Software Inc, La Jolla, CA). 3. Results In Phase 1, bench testing of the modified CEW cartridges demonstrated that the modified probes and wires could transmit simulated ECG signals produced by a rhythm generator. Further testing demonstrated unimpaired ability to discharge and deliver the probes at a static target. The discharged leads then successfully transmitted ECG signals from a rhythm generator (Fig. 1) and from surface electrodes placed on a human volunteer (Fig. 2). Finally, a modified CEW cartridge successfully delivered an incapacitating current to a human volunteer and then recorded an ECG signal from the CEW probes imbedded in the subcutaneous tissue of the volunteer's back (Fig. 3). Phase 2 involved mounting the technology onto a standard law enforcement issue CEW. An ILR was secured to the CEW via a custom fabricated mount (Fig. 4). Bench testing demonstrated the ability to discharge the CEW without impediment and for the ILR to record generated ECG signals via the modified CEW cartridges (Fig. 5). Phase 3 involved initial human testing of the prototype CEW with cardiac biomonitoring. A convenience sample of 6 law enforcement trainees were recruited. 5 of the 6 subjects (83%) were male. Additional demographics are shown in Table 1. The prototype CEW effectively deployed and delivered its intended discharge in all 6 subjects. The probe trajectory and placement was as expected in all subjects. ECG signals with 3 or more consecutive QRS complexes constituting an “interpretable” ECG as previously defined was clearly present in one of the cases, providing proof of concept (Fig. 6.). Other tracings were obscured by motion and artefactual noise. None of the subjects experienced any unexpected adverse effects from the exposure and all subjects continued with their training. 4. Discussion A rapidly expanding body of literature has defined the physiologic effects of CEW exposure in humans, and has to date revealed
Fig. 6. Simultaneous ECG tracings from anterior surface ECG reference (upper) and posterior CEW-mounted ILR (lower).
no life-threatening metabolic, respiratory, or cardiac effects with exposures up to 45 s.13 Despite these reassuring findings, there are ongoing concerns regarding possible cardiac rhythm disturbances from the electrical discharge of the CEW. Although a very low rate
52
J.P. Stopyra et al. / Journal of Forensic and Legal Medicine 43 (2016) 48e52
of significant injuries (0.25%) has been found in over 1200 field CEW uses by law enforcement personnel, cardiac complications continue to be a concern because of potential associated mortality.14 This work has demonstrated that ECG signals can be detected via standard law enforcement issue CEW probes and wires, providing proof-of-concept that it is possible to incorporate biomonitoring of cardiac rhythm into a CEW. Although the design had a low yield in providing identifiable ECG tracings, we were successful in demonstrating a sinus tachycardic rhythm in one subject. In the future, we would envision production and use of a combination CEW/ECG that incorporates existing miniaturized ECG technology internal to the CEW device with enhanced filtering to reduce artifacts and noise. In addition, it would include storage and downloading functions as well as user notification methods to alert non-medical law enforcement personnel of potential medical issues in real time. Audible alarms and visual signals indicating extreme tachycardia, ventricular fibrillation, or asystole could convey the potential urgency of the situation and guide nonmedical users to reassess subjects and to call for medical aid and/or apply an AED. Such a device could be used to provide biomonitoring of suspects after CEW use and rapid notification of police personnel of potential medical complications. The addition of respiratory rate monitoring by measurement of cyclic variations in impedance between ECG leads is also theoretically possible but not evaluated in this work. This technology is well developed and routinely incorporated into pre-hospital and hospital medical monitoring devices. Addition of these capabilities could increase suspect safety during and after the apprehension process and promote rapid activation of potentially life-saving medical care in rare instances of serious medical events. Partnerships between biomedical device manufacturers and less lethal weapon technology industries could benefit private companies, researchers, law enforcement agencies, and most importantly subjects who may be at risk for life threatening problems after CEW exposure. Similar capabilities could be incorporated into handcuffs or into a freestanding device with skin surface attachment for biomonitoring of suspects in police custody. 5. Limitations This work is an early demonstration and proof of concept. More development is required to have reliable, interpretable ECG recordings after exposure, and to incorporate additional features as discussed above. It is important to note that not all CEW uses result in sustained subcutaneous placement of both probes, which is a prerequisite for biomonitoring as discussed. 6. Conclusion ECG signals can be recorded via standard CEW probes and wires with minor modifications. Further, it is possible to combine an existing ECG analysis and storage device with the CEW without
negatively impacting its function. Incorporation of this type of biomonitoring into future law enforcement devices could increase safety and allow rapid treatment of suspects who may suffer a medical crisis while in police custody. Funding and acknowledgements This project was supported by Grants No. 2004-IJ-CX-K047 and 2006-DE-BX-K002 awarded by the National Institute of Justice, Office of Justice Programs, US Department of Justice. Points of view in the document are those of the authors and do not necessarily represent the official position or policies of the US Department of Justice. Phase 3 of this project was supported by an investigatorinitiated grant from the Medtronic Corporation, including Reveal® XT ILRs and technical support. The authors wish to acknowledge and thank Mt Airy North Carolina Police Department, Todd Lazarus, Jim Martin, Jackie Corino, Catherine Burgess and Travis Ardner for their valuable expertise and technical support. References 1. Vilke GM, DeBard ML, Chan TC, et al. Excited Delirium Syndrome (ExDS): defining based on a review of the literature. J Emerg Med. 2012;43:897e905. 2. Kroll MW, Lakkireddy D, Rahko, et al. Ventricular fibrillation risk estimation for conducted electrical weapons: critical convolutions. Conf Proc IEEE Eng Med Biol Soc. 2011;2011:271e277. 3. Sheridan RD. Letter by Sheridan regarding articles, “TASER electronic control devices can cause cardiac arrest in humans” and “TASER electronic control devices and cardiac arrests: coincidental or causal? Circulation. 2014;130:e167. 4. Kroll MW, Lakkireddy DR, Stone JR, Luceri RM. Response to letter regarding article, “TASER electronic control devices and cardiac arrests: coincidental or causal? Circulation. 2014;130:e168. 5. Zipes DP. Response to letter regarding article, “TASER electronic control devices can cause cardiac arrest in humans. Circulation. 2014;130:e169. 6. National Institute of Justice. Study of Deaths Following Electro Muscular Disruption; May 2011. https://www.ncjrs.gov/pdffiles1/nij/222981.pdf. 7. Ho JD, Heegaard WG, Dawes DM, Natarajan S, Reardon RF, Miner JR. Unexpected arrest-related deaths in america: 12 months of open source surveillance. West J Emerg Med. 2009;10:68e73. 8. Jauchem JR. Deaths in custody: are some due to electronic control devices (including TASER devices) or excited delirium? J Forensic Leg Med. 2010;17: 1e7. 9. Ho JD, Dawes DM, Chang RJ, Nelson RS, Miner JR. Physiologic effects of a newgeneration conducted electrical weapon on human volunteers. J Emerg Med. 2014;46:428e435. 10. Vilke GM, Payne-James J, Karch SB. Excited delirium syndrome (ExDS): redefining an old diagnosis. J Forensic Leg Med. 2012;19:7e11. 11. Vilke GM, Sloane C, Levine S, Neuman T, Castillo E, Chan TC. Twelve-lead electrocardiogram monitoring of subjects before and after voluntary exposure to the Taser X26. Am J Emerg Med. 2008;26:1e4. 12. Ho JD, Dawes DM, Bultman LL, et al. Respiratory effect of prolonged electrical weapon application on human volunteers. Acad Emerg Med. 2007;14:197e201. 13. Vilke GM, Bozeman WP, Chan TC. Emergency department evaluation after conducted energy weapon use: review of the literature for the clinician. J Emerg Med. 2011;40:598e604. 14. Bozeman WP, Hauda 2nd WE, Heck JJ, Graham Jr DD, Martin BP, Winslow JE. Safety and injury profile of conducted electrical weapons used by law enforcement officers against criminal suspects. Ann Emerg Med. 2009;53: 480e489.