TIltS DO(-,UMFNT CONTAINS __ILPAGES. COPY NO. OF -R' COPII!-,S. ELEC'I'RIC CURRENT AS AN AcE,4,r FOR ?RRSONNEL INCAPACITATION -______@lrepared by: 22 Octobcr 1971 is report has been prepared by Th as a part of a Government Contract, @he views expressed are those of personnel and not necessarily those of the United SLates Government. TABLE OF CONTENTS pa Prf-ttocol 91.,itemc,.nt . . . . . . . . . . . . . . . . . . . . . . i Li,st >f Figures and Tibles . . . . . . . . . . . . . . . . . . Problem . . . . . . . . . . . . . . .2 . . . . . . . . . . . Discussicn . . . . . . . . . . . . . . . . . . . . . . . . . 1, P.:)tential Applications . . . . . . . .. . . . . . . . 11. P:iysical Variables of Electric Current . . . . . . . . . 3 Ill. P--iysiological Considerations . . . . . . . . A. Effects of Electrical Curren2t on Hurr-ans . . . . . . 5 F, -The Human Body as an Electrical Conductor . . . . . 10 C. Skin Resistance . . . . . . . . . . . . . . . . . . 11 D. Burns and Other Thermal Injuries . . . . . . . . . 12 E. Pulsed Current . . . . I . . . . . . . . . . . . 13 2 F. Overcoming Skin Resistance . . . . . . . . . . . . 14 G. Path of Current Flow Through the Body . . . . . . . is I-f. Physiological Conclusions . . . . . . . . . . . . . .17 IV. Other System Factors . . . . . . . . . . . . . . . . . 20 V. Equipment State of the Art . . . . . . . . . . . . . . . 23 5 VI. Recor):imendations . . . . . . . . . . . . . . . . . . . 25 References . . . . . . . . . . . . . . . . . . . . . . . . . 27 LIST OF FIGURES Figure I Approxirnate Thrcsliold of I-leart F'.brillation I Ilazard for Single 13rief Current Surges (AC or DC) . . . . . . . . . . . . . . . . . . 9 rigu-re 2 Diagrarn of 2Body Area Cornbinations for Current FtOw Througli Chest . . . . . . . . . . . . . 17 LIST OF TABLES Table I Definition of Basic Electricity Terms . . . . . . 3 Table 11 Sensation.and Effects on Heart and Respiratory Muscles of Currents Lasting I to 30 Seconds . . . 1. . . . . . . . . . 8 ELECTRTC CTJRRENT AS AN AGENT FOR PERSONNEL FNCAPACITATION PROBLEM To evaluate, especially frorn the pi-iysiologic point of view, electric current as an agent for personnel incapacitation. 2 DISCUSSION 1. Poteritial Applications for Incla@@@ Electric current possesses a number of possible advantages when compared, .to other proposed agents for personnel incapacitation. Controlled electric shock offers, not necessarily simultaneously, the following possibilities. .Droad spectrum of 2incapacitation: annoyance, fear, intimidation, pain, muscle spasm, mincr burns, paralysis, suffocaticn, unconsciousness, severe burns, death. Relative predictabilit)r of physiologic effect.: reliable relationship be- Lween dose and responses. C-ontro'-Iability- of dose and on/off fimes. Directivity: with respect to person to be inca2pacitated and bo@ly part(s) to be affected. Effecti,.,en(-ss on a wide range of subjq_cts.: re,ardless of determination or level of consciousness. Rapic'iity of inca]2acitation: onset of action witliin a second. Rapi(lity of recov=.- only a few seconds for the milder effects. Safety. f2or b@tli the operator and t-he subject,*if de-5ired. Througliout tt.s r,@port, stibjects irL- i.@,stimerl lo be lic,,ilthy, .1('Itllt 11LIrnanS in tl-se 45 to 90 kilogram weight range. Covertne-ss: quiet -tnci t;nt)l)triigive, cLn be clirnotifl.-Igerl. Aside from tcclinir,,i] detiiis of the delivery system, tl-t(@ oiil,,r I)ro.-Icl limita- tions to use of electric current as an i-.icapacita2tion agent liave to do with the number of stii)jects and the duration of incapicitr--tion, It is diffictilt to conceive of realistic circumstances th,-Lt would perrnit a safe and ti-niforrn dose to be administered to a n@imber of subjects at one time, altbotigh current would be as effective for the entire group as it is f2or an individual. In this report, current is coi-tsidered as an incapacitating agentf for individuals only. Elec'.ric ciirrent can be quite safe for periods of incapacitation of a few seconds only) hazards become much greater if current is used to ry)aintain incapacitation for a minute or longer, unless special techniques and pre- c2auti.ons are used. W'ithin these limitations, current could be used as an incapacititing agent under virtually any circurnstanc,@s. Power can be su-pplied from permanent supply lines, temporary generators and lines, or portable supplies (includ- ing pocket-sized battery packs in some cases). Delivery systems might be' p4@,,rmanent in5tallations, tem2porary traps, hand-held instruments or long- range project--le devices. Automatic controls would suffice for systems designed for brief incapacitations, but systems main-.a,'ning incapacitation for rnore than a. few seconds should be controll-ad by an operator who has some training in the methods of safeguarding the hea'th of the subject. II. Pliasicti Variibles of 1--lectric Ctirr(,nt The performtnce ind suitibility of electric shocir for persoi-inet inc,,ip;icita- tion may be affected by several variables which characterize the incapaci- t,iting current. The more important electrical 2parameters are voltige, current, power (or energy) and frequency. For familiarity, these and other ter-ns used in this stud), are briefly defined in Table 1. TABLE I DEFINITION Or 13ASIC ;'LECTRICITY TF'-'@@AS Characteristic Brief Defiriit,oii bymbot Unit Voltage E,:Iectrical pressure or the E volt electromotive force tending to move electrons, potential Current Volume of electron flow I arnperp Direct Current 2 Current that does not vary DC a-rnpe re in direction or magnitude with time Alternating Current Current that has continuous AC arnpere sinusoidal variation in direc- tion and magnitude xvith time 2 Frequenc-,r Rate of alteration of an AC f I-Te rtz current (cyc te s / sec) Resistance Opposition to the flow o--' di- R ohm -rect or atterilating current 2 Impedance Opposition to the flow oi z ohm alternating current Pulsed Current Current that flows inter- mittantly, but repe@tedly Energy Capacity to do work jokile Power 4 Rate of delivery of energy, p watt the product of voltage and current Electric cii-rrc-nts are most often supplicci from b,-Lttel-ics (direct clir -C-.nt) or from rc)titing F-ener-itors (either altc!T-niting or dirc-ct ctirrer.1). The ctir- rent is tistially cai-ried from one locale to ,inother ley low r(,,si.9tince concluc- tors, s!Lich as noi-i-fc-rrotis metils, or by ionizc,.cl liqtiicl.,-, or gases. and is prcventeci f-orn leaving the desireci path by high resist@tnce inskilators, Tllc application -)f ctirrent or volttge to 1),;iqic elc-c-tric-LI devici--s, inc-.Ititling resistors, coils, and capacitors, permits a wide range of ftii-ictions to be performed by electricity, These basic electrical 4@evicc-s cotipled with rnore cornpticated devices, such as vacuurn tubes and transistors, form the work- ing components of all electrical and elect-ronic sys@e2ms which generate, tr,-tnstiiit, store, amplify, modiiiate or otherwise ck)ntrol electric-, ti@rr(,nt. PkirposefuL control of the variables of electricity can be accomplished through the use of these basic devices. For exarnl:ple, a coil or incltictor ,.Vill tend to conduct direct current and lo,.v frequencv alternating citrrent, while irnpe@ing high frequency alternating current. Similarly, a capacitor or condenser acts as a conductor for high frequency alternating current, but impedes direct current and low frequency alter-nating current, The spectrum of physical and physiological effects produced by the varia- tions of volca-e, current and frequency is probably familiar to2 many read- ers: the tingle of a mild electric shock of low amperage, the appearance of a high volt,,ige arc discharge, the accidental bur-i from I 10 volt, 60-1-Tertz "house current" or the painful shocl@;. from the high vol-,@age of an automobile ignition system- In terms of incapacitation and biological effects on living sy8stems, ctirrent not voltage - is the most important variable of electricity. The frequency of the ckirrent may also be a factor in deterr@inirig the dcl(-teriotis effects of electric current, especially with regard to the sensit-ivity of the hklman heart. 4- III. Pli -.;if)lo icit on.@id@erati(Dns A. Effects of Electrical Ciirrent on I-Itimans With the exception of inconsequential effects such as the feel'Ing of 'hair.- standing-on-end, high voltages without current flow have no knowii effect on human 2welt-being or performance, Polarity of a dir@ct current or brief di@charge rnakf-s no apparent difference with regard to the incapaci- ta.ting effects of flowing current. As it relates to the incapacitation problem, electric =urren@, has only three significant e-EfeLts on human tissues: 1. Dep,31arization, of nerve and mus2cle tissue, @-ausing the "firing" of nerve or brain cells and coritraction of muscle fibers. Depolarization causes the subjective ti,-igle, involuntary muscular contractions and several other side-eff2cts of an electric shock. 2. Channe in sensitivity of cei-tain irritable tissues, such as increas@d heart irritability and s,.tnsjl&-i 2it-y to fibrillation. t Fib-illa'@ion is an uncoord- inated "bag-of-worms" contractile activity of the heart, and is a major threat to life which may ensue when moderate electrical currents pass through the heart. Death can follow because a fibrillating @zart c@,-nnot pu,mp blood. 3. Heating, to the pl@int of coagulation and burniz2,g if ctirrent flow is large enotigli or concentrated in a small atea, All three of the above effects could contribute'to the pain of a severe shock, although a laz- e part rnav be pain due to mlisc M. le spas Unless otherwise attributed, the material presente-J in this section is de- 3 rived from Re-'erence 1, which also provides a biblicigrapliy of the basic publications on the physiologic effects of electric cui-rent. t In this report, fibrillation rneans ventricular fibrillation, 5-, Detiilc-d effic@cts c,-iri bc prcdictcci if the @LT-np(, rage, rotit(- i-lirokigl,. tli,4, 1.)Ociy. dliration of current flo,@v anr3 freqtiency of t]-ie power supply are known. De- liberate exectition in an el(-2ctric chiir is an extreme examplc- in which approxirrately 10 @Lmperes of 50 to 60 Hert7, current are passed from 'head to both feet for longer than a minute. Such a lethal curr(-nt citises imnied- i,ite tinconsciousness, immediate and continuot:ts Ilt-6t@xnic" contriction of all rnajor rntiscles including the heart, thereby arresting respiration and. all useful heart activity, and severe heating effects most pronounced where the .,D-@@cial electrodes make contact with the ski-,i. The colloquial phrase "frying in the chairl@ seems apt. A less drastic but equally dramatic , -,a of electric current is in electro- 2 convulsive therapy or "shock treatment" for mentLI illness. In this case, 50 to 60 ho--rtz currents on the order of I ampere &re passed from one side z , of the head to the other for one-half second or less. @he patient irnriiedi- atei)r loses consciousness and ha2s a generalized convulsion that appears to last longer than the duration of current application. The patient usually regains cor-sciousness 'Within a few minutes and may be phys-ically able to walk promptly. There is likely to be residual muscular soreness and a confusional state may persist for any pz@riod of time from seccnds to days. 2 The patient retains perrnanert amnesia for the time of the shock and usually makes no serious objection to repeat treatments, Therapy personnel tale great care to make large-area, low-resistance ele,7.trical contact on both sides of the head to prevent current burns on the Facitnt's scalp. It must be emphasized that cur-ent flow2, and hence all direct effect, of electro- convulsive therapy, is confined to the head. Thu@ depolarizing action of the current on the brain causes convulsive stimuli to flow out to the muscles through the normal channels of the nervous system; there is no significant current flo,.v through the trunk or extremities althotigh they 6move violently. Only organs in the pati-k of the current flow can be affected directly. This is wh-@ there is no risk of direct electrical interference with betrt action during properly conducted electro-convulsive therapy. (,-iirrents passing t,,.Totigh the torso can cakise spas:ic -,2arilysi5 of I:Iic.- respiratory, baclz and abdominal rnuscl(,,s. Contin--ious pir,-Llysis of Llie re-qpiratory mtiscles for several mintitc@s cin lead -a stiffocition rei,,ardl@2-ss of other consequences. The most imr-nediate and potentially lethal threat posed by a ::tirrent passirg through the chest, however, is electricl] inter- tercnce wit-i heart activity. Table 11 outlines the hizards of currents xppl'cd c.-cternally to tile chest for several seconds. Inspect2ion of Table 11 reveals several key points. For a given curr(,nt level in the 0 to 3, 000 milliampere range, alternating current has greater physio- logic effect and is more ha@.ardous than direct current. Fibrillatic)ii of the heart is rarely caused by direct current regardless ul arnperage-. Vent- ricular fibrillation is almost always fatal unles2s given special treatment within minutes, but hearts that have bfen completely paralyzed for short periods usually resume normal activity spontaneously after the current stops. This difference accounts for the apparent Faradox in the dose- response relationships shown for alternating currents: other factors being equal, a current greater than 3 amperes is less litzely to b2e imrnediately fatal than currents in the 80 milliarr@pere to 3 ampere range. It must be ernphas-'-zed that the approximations indicated by T3Lble :11 are valid only for current applied externally acros,,z the chest and for the indicated durations. The voltage required to produce a given current, cf course, is highly depel- 2 dent on the nature of the electrodes, skin resistance, and olher factors. The fibrillation threshold rises for current durations sliorter than one sec- ond, at least for non-repetitive pulses of curre,,,it. Figure 1 indicat,?.s an approxii-nate "worst case hrc-shotd for fibrillation hazard in terms of tile current-tirrge factor for brief ex2posures to any type of current, including 60 Hz AC and capacitor discharges. For shocks lasting less than one second, the thresho'-d shown by Figure I is for constant enc-rgy ptilses of 1. 6 joule The stardard inethod of "closed" defibrillation -,s to apply abotit 300 joules of electrical energy in 0. 2 seconds yr less through large electrodes held firn0-i- ly on the skin of the anterior cle3L. One joule is <)ne watt-secoiid. 7- TA13 LE 11 Sr--iNSATION AND EFFECTS ON 14FART ANT) RRSPTI@ATORY MTTSCI,E@ Or CURRENTS LASTING I TO 30 SECONDS (THRESliOLDS APPROXIMATE) Current 2 Sensation Heart R@s iratory Muscles (rna) ACt DC ACT DC A DC 0-1 none none none none none norie 1-5 tingle none none none none none 5- 25 pain tingle none none sligh@ none contraction Zs-ao pain pain ncfc none P&ralysii Slight 2 contraction 80-300 p-in pain fibrillation none paralysis paralysis 300-3,000 pain pain fibrillation paralys--.s paralysis paralysis over 3, 000 pain, ptin, paralysis paralys@.a paralysis paralysis burns burns For curren,s applied externally to the chest; currents smaller than 0. I miltiarni:,tr?, can cause fibrillation if applied directly tc) the heart. 3 IO- 1, 000 He0rtz .-xpoeuve longer than 30 seconds may cause fibrillation CURRENT ioo ....... . . . VI j@; FIBRILLAT. A4AHO 2 10 14 $4 IVELY SAFF: !II RE!Lr iuu lo 71 2 10 100 1 10 .100 1 10 rnicxoseconds I rnilliseconds 5econds DURATION OF CURRENT (Continuous, Non-Repetitive Flow) Figtire 1. Approxii-nate Threshold of I-leart Fibrillation Hazard for Eingle, Brief Current Surges (AC or DC).i Adak each. Scvcrti atitharities suggest that 1-iazard threshold might well be at ent-rgy levels an order of magnitude higher Li-lan that shown; thus the thres- hold shown I)y r,'igiire I may be quite conservitive-I - Currents of stiffir-ient magnitude will cause pain2ful involuntary contraction of muscles as the currents pass through an extrem.ity. The motion made by the extremity as the muscles contract will depend upon. (1) the rnuscle groups stirnulated, and (Z) the relative Strengths of contraction of the various muscle groups. A person "thrown" or "knocked down" by electric shock has been moved by his own muscle cont2ract--ons rather than any direct T)ropulsive effect of the current. Relatively weak movements caused by sinalkl currents can be overcome by voluntary muscle control, especially in large po-.verful people. A "no-let-go" current thresho'd can be determi- ned by measuring progressively larger currents f'-owing through a person's 2 arm frorn an electrode grasped in his hand, up to the current at which he can no longer voluntarily release the electrode with the current flowing. The no-let- go threshold for adults is in the 6 to 3C rnilliampere range for 60 Hz AC. Current values will be similar for other AC frequencies in the 10 to 1, 000 Hz range, but DC currents would have to be about five times ag 2 large for s--milar effect.1 B. The Human Body as an Electrical Conductor From the standpoint of electrical shock, th-- normal human body can be con- sidered as a bony framework encased in a protein get with some lipids, all of which is permeated with an aqueous salt soltitio-,i and encased in a water- proof skin. The electrical resistance of organs generally varie2s inversely with water content. Tissiies such as blood and muscle display resistances in the order of 1, 000 ohms per cubic centimeter while dense bone, fat and nervous tissues have resistances several times hicyher. Whole body resis- tance, exclusive of skin, is on the order of ZOO- 1, -DOO ohms. TI-ie trunk has' a lower resistance than the extremities 9with their smaller cross section and high proportion of bone. Current inside the bc-dy appears to spread in a to- fairly uniforrn manner through tl-ie available volume between the point of entrance and the point of exit rat)-ler than being noticeably conc(-ntrated along any sp-2cial low-reSiStATice pith. The sicin usually presents the rnajor resistive barrier to electric ctirrent flow. Most Df the skin resistance is in the opider,-nis, the dry, horny outer Layer withotit blood vessels. Thickness of the epidermis, and hence the resistance of the skin, may vary widely between different parts of the body, Thin skin behind the knee or in the axilla may offer less than a thousand ohms resistance, especially if moist. At the other extreme, a tllick, dry callous may offer resistance approaching a rnill-lon :)hrns. Skin that is rela- tivety moist, such as on the palms, soles or axi',Iae, will be more conduc- tive than drier skin of the same thickness elsewhere on the body. 1 During sound sleep, all skin resistance rises greatly.4 C. Skin Resistance 1 The major factors in electrode-to-bod2y resistance through the skin are: 1. Thickness and intrinsic moisture of the skin, as noted above. Range: about 1, 000 - 1, 000, 000 ohms (dry contact). 2. "Wet" or dry contact. Presence or absence of an electrolyte solu- tion providing a conductive pathway between electrode and skin. "Wet" contact can be proveded by special preparati2ons suc@'i as electrode paste or fluids such as sweat, blood, saline solution or even tapwater. Conversion from a dry contact to a "wet" one usually drops the :,esistance one or two orders of maffnitude. 3. Intact or damaged skin. Any thinnii-g, scratching or penetration of the epidcrmis can drastically reduce skin resistance. In addtion to any 7 reduction due to a wet contact, painless, gentle sandpapering of the skin can also redtice the resistance one or two orders of magnitude. Even a tiny penetrating burn, such as that caused by a small area of contict witl-i high voltage, will cause a near-instantaneous drop in skin resistance to a few Iiiindrcd ohms or less. 4. Area of contact. Otl-Ler factors being cqtial, resistance is inversely proportional :o the area of contact. A large area of Liniforn-I dry contact is difficult to ac-hieve in practice. Significant and predictable redtiction in rcsist.ince by lirge area contact is ordinarily achie2ved only with wet con- tact such as immersion of a bod-,r part or wet clothin-,Y. 5. Pressure of contact. Increased pressure on a dry contact with intact slizin can reduce resistance, but the effect is usually not pronotinced enough to cause dry electrode-to-skin resistances lower than 10, 000 ohms untit the contact pressure exce2eds 10 kilograms per square centimeter. 6. Frequency of the electric power. Skin in-ipedence, or total tenden- cy to obstruct the flow of electric current, is inversely proportional to increases in the frcciuenc-)r of the applied electric power. The relationship ii not sufficient to lower the effective skin impedance two orders of magni- tude until the power supply 2frequency approaches 100 kHz. This repo--t is not concerned with such radio frequency currents because "skin effect" . keeps most of the current o-i the body surface where it is ineffective as an incapacitating agent. 7. Skin :zovering. Dry hair and most dry cloth-.ng can increase the electrode-to-body resistance by millions of ohms. D. B2urns and Other Therni@ I@nu@jLies The beating effects of electric current are dependent upon the amount of electrical ene.-gy being dissipated per unit time in a given volume of con- ductor. About four joules of eiectrical energy must be dissipated in a gram of water in order to beat the water one degree centigrade. In general, the tempe-rature rise of tissue being heated 2by electric current varies: 1) directly with the square of the current 2) directly with the resistance of the tissue 3) directly with the time of current flow 4) inversely with the effective volurne or cross-section of the conductor 12- Consider,-ition of tl)csc f,'Icts Ic,"fls to the conclusion th,-Lt the highest temper- attire rises in most cases of electrical sliocie will occur in the skin at one or both points of electrical contact -,vith the body. For significant current flnws, skin burns of some degree will rel-Liain a hazarci unless spe2cial precautiolis are taken to avoid high skin r@sistance and small effective cross-sections of electrical contact with the sirin. Conversely, the large effective cross-,,ection and lo-.v resistanci-. of the body beneath the skin means that n-iany amperes of current flowing for prolong- ed periods would usually be required to "cook" organs other than the ski2n. An electric arc in air at one atmosphere has a temperature of 2500' to 3000' C and can cause local heat effects other than those due to current passing through skin resistance. E. Pulsed Current Repeated brief pulses would seem to offer several decided advantages as a form of delivering electrical energy for incapacitatiz)n purposes. At a pulse 2repetit-'-on rate of one per second or faster, pulsed currents should be able to cause as much pain, paralysis and incoorjination as continuous current, per,iaps even rnoi,e than continuous direct current. Very brief pulses and a sr-nail duty cycle would mean low average power levels, resul- ting in: (1) reduced burn hazard to the subject; and (Z) reduced drain on the power supply 2system. For example, a one ampere pulse lasting one millisecond (0. Z5 joule of energy, assuming internal body resistance of 250 ohms) cculd be repeated at 10 pulses per second with a time-average power of oniv 2. 5 watts, one hundred times less than a continuous current of one ampere. If such pulses passed throug@% major portions of a man's body, they should be 5completely incapacitating with onlv minor burn hazard and low drain on the power supply. Figure 1 might be misconstrued to suggest that such a pulsed current is known to be safe as fkr as the 'heart is concerned. It must be emphasized that the figure relates to a single 13- AgMk w non- re petitive pkltse only, a,d that ha7ard thre,,ho"6s pulses 1-c-i-nain to be determined. Worki2ng will-i data from studies LiSing I-iurnans and expe-rirriental anirnals, Zoll and cc-woriers found that: (1) 3 millisecond pulses of abokit 100 rnil- liamperes (energy 0. 06 joule and less) applied across the @--host would trigger a 1-ieartbeat; and (2) pulses repeated 8 to Z) t2imes per second for periods on the order of a minute could cause fibrillation in some cases. 5 Thus a one ampere pulse lasting one millisecond lenergy 0. 25 joule) would be likely to trigger a heartbeat each time the pulse passed through the chest, and a fibrillation hazard could exist in normal hearts subjected to rapid rates of such "external heart pacing" for 2prolonged periods. From the information presented by Zoll et at, there would appear to be little danger of fibrillation or low cardiac output if the external pacing -is @arried out aL a rate within the normal heartbeat range. Thus a repetition rate of about two pulses per second might prove to be well tolerated for prolonged periods, at least as far as direct cardiovascular hazard is concerne2d. Incapacita--"Lng pulses passing through the chest at a rate of about two per second are likely to interfere seriously with breathing, and might prevent loud vocalization, along, with a-ay otl-ier coordinated action. If breathing were stopped by the pulses, the subject could eventually suffocate, The safety of repeated brief pulses for incapacitati2on p6rposes has not been proved by the Ireport dated 25 Sune 1971. The longert reported test period was four seconds and no evidence is pre- sented with regard to the subjects' cardiac or respiratory stattis durina the test period, the t-Lme required for functiona'i recovery after delivery of the last pulse, and the th3resholds for "no-let-gol I status and skin burns. F. Overco@@@@@ As previously noted, hum,-in skin and hair often present a trajor resistive 14- barrier to delivery of electric current for incapacitation purposes. 1%4cthods of overconniiig the skin resistince problem may be summarized as follows: Avoid tl-ie slzin. ?vlale cox)t,-Lct with moist mucosal surf,-Lces such as mouth and rectum. ],in. Make conta(,@t with sl;.in sui-faces that are already wet. u S@e Wt@5 I'@ @. or deliberately'moisten the eloctrode pi-,tcernent sitals. Use damac:ed slot in a rice paddy, and entirely differevt if he is standing in diy she -,s on a d-ry wooden floor. An,,r change in the --Libject's body contact with "ground, 11 such as falling onto or away from llg:-otind, 11 5 can radically alter the current flow situation. - 16- AML Heart U Umbilicus Figure 2. I)iagrarn of Body Area Cornbinations for Current Flow Through Chest. (See Text) H. physio It is possible to u4se electrical current as an agent :o cause a whole spectrum of human in-zapacitation from minor distract;on through muscle sp.-Lsm, pain, contortion, minor burn,3, x@espiratory arrest and perhaps vocai paralysis, cardiac arrest, unco-4@sciousnes@, xitli convulsion, severe burns and death. 17- The approxirnate degree and duration of incapacitation can, within lin-tits. be predetermined by appro-)riate selection of curren: type, amount, dura- tion, and patlt ira tl!e body, In generzli, electrical tc-cliniq@ies tc-.nd to he tirne-tirnited if safety is a consideration-, prolonged use of electric current 2 to i-naintiin incapacitation may present grave hazards to the subject in thi- forrn of burn:i, inadequate heart output or inadequate respiration. On the other hand, a brief "knock-do%vn" incapacitation can be achieved with rela- tive safety by almost any large current flowing for an extremely short period of time (less than a mi.Ilisecond), Several t2echniques can be,used to increase the safet-i factor of current being used to incapacitate for longer than the "knock-down. 11 A current large enotigh to cause extremely painful paralysis of the extrernities pre- sents no danger more serious than burns if t does not pass through the chest. In this respect, optimum safety with severely incapacitating currents could be achieved with the current flo2wing: (1) from one lower extremity to the other; or (2) from a distal point to a proximal point on the same extre- mity. Over such paths continuous AC current of rn,)re than Z5 milliamperes or DC currer-t of more than 80 milliamperes should keep at least one extre!- rnity of a man painfully paralyzed for the duration of current flc, ; currents larger t2han an arnpere could cause severe burns, especially if the current flows continuously for many seconds. If the current path is through the chest, the use of direct current will vir- tually obviate the hazard of heart fibrillation although the likelihood of res- piratory and cardiac arrest remains with direct currents in the effective range. Cardiac arrest causes unconsciousness within a few seconds and 2 death after severa" minutes. Complete respiratory arrest usually causes unconsciousness in iess than four minutes and death in about ten minutes. Both kiqds of arrest would be likely with direct currents larger than 300 milliampv-res passing through the chest, so incapacitating direct current would usuallv have to be kept in the 80 to 300 rnilliampere range if it is to be used9 for prolonged periods. 18- Ask w The safety rn.-Lrgin for incapacitating levels of alternating current flowing Llirotigh the cliest is ntrrow for periods as short as a few seconcis and tbc!rc is no m@irgin of safety if the clrrent flows for more than 30 se2conds. All such shocl-,s should be considered potentially, lethal. C.-Lrefully chosen piitsed currents, perhaps brief surges of one jottle or less delivered once or twice per second, may offer effective and relatively safe incapacitation when flowing between.Lna two widely zpaced points on the body. Several key questions regarding the2 safety and effectiveness remain to be answered by direct investigation, but indirect ev@,idence suggests that such pulses would offer the following ad,iantages; (1) no direct threat to aL normal heart for any duration of incapacitation; (2) only minor ski-.i burns at worst; and (3) low average2 current requirement for the paver supply. The facts remain to be verified, but such pulses passing from any point on the upper extremities or the upper body to any poi-nt below the waist may well be ca@-able of preventing respiration and effective speech in addition to causing conip,ete imrnobilization by muscle spasm and pain. If this is2 the case, an operator could be equipped with a system enabling him to: (1) knock P. subject down rapidly; (2) keep the subject incapacitated and un-- able to make an effective outcry for perhaps a minute; (3) turn the pulses off for long enough to allow the subject to take a breath or two. (4) turn the pulses Lack on unti2l the subject becomes blue or passes out; and (5) repeat steps 3 and 4 for a reasotiable length of time. Pr;Dperly handled, the sub- ject should recover promptly after the pulses have been turned off for sev- eral seconds, and have no permanent ill effects aside from probable small- area skin burns. Electrical currents are not 1 lil