mechanical analysis of survival in falls from

8/6/2019 Mechanical Analysis of Survival in Falls From

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INJURY CLASSIC

Mechanical analysis of survival in falls fromheights of fifty to one hundred and fifty feet*

Hugh De Haven

During the interval of velocity change in aircraftand automobile accidents many typical crashinjuries are caused by structures and objectswhich can be altered in placement or design soas to modify the large number of severe andconstantly recurring patterns of injury in theseaccidents. In order conscientiously to approach

some of the engineering problems encounteredin reduction of the potential injury hazards ofwindshield structures, seats, instrument panels,

safety belts, etc, it was necessary to have someunderstanding of the limits of mechanicalstrength of the human body.

The objective in studying the physiologicresults of rapid deceleration in the followinginstances of extraordinary survivalafter freefall and impact with relatively solid

structureswas to establish a working knowl-edge of the force and tolerance limits of thebody. On the basis of these data certainengineering improvements can be consideredfor aircraft and automotive design.

Loss of pilots through injury due to theincreased landing speeds of military planes hasbecome more and more frequent; this loss andthe ever present toll by accident in theautomotive field are matters of grave nationalconcern. Injuries in these fields are mechanicalresults stemming from localized pressuresinduced by force and applied to the body

Editors commentThe Classic by de Haven is more important than readers mayrealize. That is why I asked Flaura Winston, whosebackground in engineering and medicine is so unusual, tointroduce it. Together with my gentle encouragement, I hope

readers will fully appreciate de Havens remarkable contribu-tion. Three aspects of his paper are compelling. First, it isbased on simple observations and thus serves as a wonderfulexample of how important these can be. Beginning with thissmall series of case studies, by applying the inductiveapproach, de Haven formulated a general theory of preven-tion. In essence that theory says that the basic laws of physicsoperate as well in human injury as in other domains. Second,the application of these laws about how force is distributed orabsorbed to reduce damage, later elaborated on by Haddonand others, is the basis for most of the most eVective injuryprevention measures so popular today (harnesses, seat belts,helmets, playground surfaces, etc). Third, de Havens workwas, indeed, the birth of a science. Having laid a solid empiri-cal and theoretical foundation, the next concrete steps were

taken by Colonel Stapp (whose death is noted elsewhere inthis issue). Stapp began testing the force distribution theoriesby dynamic sled testing. We will publish some of his findingsin a later Classic. The bottom line is: Hugh de Haven was agenuine pioneer and this paper includes many messages thatare important to anyone working in injury prevention today.In a later paper, de Haven wrote: ... people knew more aboutprotecting eggs in transit than they did about protectinghuman heads and with respect to this issues Classic, headded: They [the cases] did more to support my theoriesabout crash injuries and crash survival than all the words inthe dictionary. Read and enjoy.

The beginning of injury scienceInjuries are not accidents. This simple statement hasbecome the mantra of injury control professionals. Whendid the realization begin that crashes and their resultantinjuries were not inevitable but rather were predictable

and, therefore, preventable events? In 1919, Hugh DeHaven ruptured his liver, pancreas, and gall bladder in anairplane crash as a cadet in the Royal Flying Corps. Dur-ing his convalescence, he began to question the inevitabil-ity of injury as a result of aviation crashes. Thus dawnedthe field of crash investigation and injury science. When hebegan presenting the findings of his research, he encoun-tered the resistance and inertia that many of us stillexperience today: his commanding oYcer preferred toattribute escapes from injury to the Jesus factor andpathology to the luck of the game. But Hugh De Havenpersisted and his commitment to applying a scientificapproach to injury led to the acceptance of safety belts asprotective devices. Mechanical analysis of survival in fallsfrom heights of fifty to one hundred and fifty feet

provides one of the earliest examples of injury science.The results of this research continue to be relevanttoday.

FLAURA KOPLIN WINSTON

Director of TraumaLink,

Interdisciplinary Pediatric Injury Control,

Research Center at the Childrens Hospital of Philadelphia and the

University of Pennsylvania,

34th Street and Civic Center Boulevard 2426,

Philadelphia,PA 19104, USA

This is the latest paper in aseries of Injury Classics.Our goal is to reprint one ortwo such papers in eachissue to introduce newcom-ers to these old,oftenquoted, and important con-tributions. As many arediYcult to find, it shouldhelp all of us to have a copyat hand. Your suggestionsabout future articles arewelcome. Write to the editorwith details of your favour-ite, most quoted paper.

*My interest in the mechanics of injury and safety design datesfrom experiences in the Royal Air Force during the last war.Observations made at that time, during investigation of aircrashes, gave strong indication that many of the traumaticresults of aircraft and automobile accidents could be avoided.Structures and objects, by placement and design, created aninevitable expectance of injury in even minor accidents.Occasionally, however, accidents apparently having every fatalcharacteristic would occur without causing physical injury.Detailed evidence of apparently miraculous survival in theinstances of free fall described here, indicates the strength of thebody under conditions of extreme force closely paralleling thoseencountered in many severe automobile and aircraft accidents.

Injury Prevention 2000;6:626862

Research Associate,

Department of

Physiology, Cornell

University, Medical

College, New York

This paper first appeared inWar Medicine (1942;2:58696)and is reproduced withpermission. Copyright 1942by the American MedicalAssociation.
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through the medium of structure. It is an axiomin the mechanical arts that modification ofcause will change results,but the nature and thedegree of structural alteration to modify injuryto human beings eVectively depend on thereactions of the body to abrupt pressure and itsdistribution. The strength of human anatomicstructure and its tolerance of pressure increaseare centrally important elements in any pro-posed increase of safety factors through engi-

neering eVort.Obviously, if the body could tolerate pres-

sure within only narrow limits, few improve-ments would be worth consideration, since theforce and resulting pressure of a severe crashare at best formidable. Evidence, on the otherhand, that the body can tolerate the force of anextreme crashwithout injurywould indi-cate that (1) extreme force within limits can beharmless to the body; (2) structural environ-ment is the dominant cause of injury; (3)mechanical structure, at present responsible forrecurring injury, can be altered to eliminate orgreatly modify many causes and results ofmechanical injury, and (4) the greater the evi-

dence of body tolerance of force and pressure,the wider the possibility for consideringengineering improvements.

Evidence of the extreme limits at which thebody can tolerate force cannot be obtained inlaboratory tests for obvious reasons, nor can itbe gained satisfactorily from most aircraft andautomobile accidents, because the variables ofspeed and angle are diYcult to appraise.Estimation of the exact speed of a crash is dif-ficult under most conditions. Also relativemovements during structural demolition gen-erally make it impossible to know the positionof the body at the time the injuries weresustained and whether the head or some other

injured part overtook the structure before itcame to a stop or after it had stopped. In thesecircumstances, the speed, deceleration, impactand force of the body and their relation to thestructure can seldom be fixed.

With the thought of overcoming many ofthese diYculties and in order to observe physi-ologic reactions to force under more simpleconditions, a study of cases of free fall wasundertaken.In several of the cases outlined herespeed of fall, striking position, deceleration andrelation of resultant injuries to structure couldbe determined with great precision. Other casesare included because of some specific interest orbecause they are relevant to the cases in whichthe evidence is clear.

The material is presented with the hope thatadditional instances of force survival may beclosely observed and recorded in order tofurther an understanding of the strength of thebody and the type of structure, position, etc,contributing to force survival.

It is, of course, obvious that speed, or heightof fall, is not in itself injurious. Also a moderatechange of velocity, such as occurs after a 10story fall into a fire net or onto an awning neednot result in injury, but a high rate of change ofvelocity, such as occurs after a 10 story fall ontoconcrete, is another matter. Between these two

extremes lies important evidence of physiologicforce tolerance.

In using expression free fall a fall free ofany obstruction other than that encountered atits termination is implied.

The word deceleration and its derivativedecelerative are used in preference to negativeacceleration, etc; velocity at contact, ispreferred to impact velocity.

The force of gravitydenoted by the symbol

gis used as a measure of the force of a positiveor a negative acceleration.

A deceleration exerting a force 150 times thenormal pull of gravity on a body will increaseits normal weight 150 times during the timethis increase of force acts. Thus, a force of 150g acting on a man normally weighing 150pounds (68 kg) would increase his apparentweight to 22 500 pounds (10 200 kg) duringthe force interval. This increase of forceandweightwould be distributed over, or appliedto, his body as pressure in areas of contact dic-tated by resisting structure.

The velocities reached in the following casesof free fall are estimated from the acceleration

equation v = 2 gs, in which the falling objectis accelerated by the force of gravity in avacuumv being the velocity, g the value ofgravity in the acceleration (32 feet [976 cm]per second per second) and s the distancefallen.

Deductions in velocity made on account ofthe resistance of the air are rather arbitrary andare estimated on the basis of weight, clothingworn and whether the body was observed to befalling head first flat or with a tumbling motion.The higher distances of fall are based on an AirCorps technical report.1

The estimated forces of deceleration aremade from an inversion of the equation for

acceleration, v2

= 2 gs, in which s equals thedistance in feet through which a known veloc-ity is decelerated. The resultant expression ofdecelerative force in pounds must be dividedby the force of gravity factor (32 feet persecond per second) to give the increase timesnormal gravity.

Minor contusions and lacerations have beenomitted in referring to sustained injuries unlessthey were of special significance.

Report of eight cases

CASE 1

A woman aged 42, 5 feet 2 inches (157 cm) talland weighing 125 pounds (57 kg), jumped

from a sixth floor and fell 55 feet (17 meters)onto fairly well packed earth in a garden plot,landing on the left side and back.

Deceleration and acceleration of gravityThedeceleration distance was about 4 inches(10 cm) as indicated by marks of the body inthe earth. The velocity at contact was 54 feet(17 meters) per second (37 miles [60 km]per hour), and the average gravity increase,140 g.

Injuries There was no evidence of material

injuries or shock. Examination of a sample of

spinal fluid showed it to be clear and colorless;

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there were no red cells in the urine. There wasno loss of consciousness or abdominal tender-ness.

CommentThe superintendent of the build-ing reached the victim immediately after shestruck the ground. She raised herself on her leftelbow and remarked: Six stories and nothurt.

CASE 2

A woman aged 27, 5 feet 3 inches (160 cm) talland weighing 120 pounds (54 kg) jumped froma seventh floor window and fell 66 feet (20meters) onto a wooden roof, landing head firstwith progressive contact of the shoulders andthe back.

Deceleration and acceleration of gravityThiswoman broke through a roof of_ inch (2 cm)pine boards which were supported on 6 by 2inch (15 by 5 cm) beams 16 inches (41 cm)apart and landed lightly on the ceiling below.Velocity at contact was 60 feet (18 meters) persecond (40 miles [64 km] per hour). Theaverage gravity increase was unknown. A holeapproximately 16 by 16.5 inches (41 by 42

cm) was sheared in the roof by the force of thefall. Three of the 6 by 2 inch beams werebroken.

Injuries The scalp was lacerated (occiput),but there was no evidence of other headinjuries. The victim suVered abrasions over thedorsal portion of the spine and an obliqueintra-articular fracture of the sixth cervical ver-tebra. There was some spasticity of theabdominal muscles on the right side. Urinalysisyielded normal results. There was evidence ofmild shock.

CommentThe fall was first known to haveoccurred when the woman appeared at an atticdoor and asked for assistance. She sat up in bed

at the hospital later in the day. It is diY

cult toreconcile the structural damage to the beamswith the absence of greater bodily injury in thiscase.

Another case in which injury occurred undersimilar circumstances but in which survival wasonly temporary is summarized as follows:

A man fell 121 feet (37 meters), landing in asupine position on a wooden roof after havingjumped from a 14th floor. In this case the roofwas broken in at one point to a depth of 8inches (20 cm), but this point was not directlyunder the area of force. The average force wasundoubtedly in excess of 200 g. The victimwalked away from the spot where he landed.His right arm had struck a 12 by 2 inch (30 by

5 cm) beam and stopped abruptly; the torsohad continued in movement, with a resultanttearing action in the shoulder area. There wereother injuries. Death was attributed to sever-ance of brachial arteries, hemorrhage andshock. The circumstances in this case aresomewhat similar to those in case 2, justdescribed, there being no evidence of loss ofconsciousness or head injury.

CASE 3

A woman aged 36, 5 feet 4 inches (163 cm) talland weighing an estimated 115 pounds (52

kg), jumped from an eighth floor and fell 72feet (22 meters) onto a fence, face downward.

Deceleration and acceleration of gravityThedistance of the deceleration could not beestimated. Velocity at contact was 65 feet (20meters) per second (44 miles [70 km] perhour) with minor gravity increase.

InjuriesThere was no evidence of materialinjury.

Comment The victim was seen during the

fall and landed jack-knifed over the fence,which was constructed of wood and wire. Thefence was broken down part way, and thevictim tumbled to the ground. She immedi-ately picked herself up and walked to a nearbyclinic for first aid. In this case, chief interestis centered on the patients having struck a1 by 4 inch (2.5 by 10 cm) board, edgeup, at the top of the fence at 44 miles perhour, without essential injury to chest orabdomen.

CASE 4

A woman aged 30, 5 feet 6 inches (168 cm) talland weighing 122 pounds (55 kg), jumped

from a ninth floor, falling 74 feet (23 meters)onto an iron bar, metal screens, a skylight ofwired glass and a metal lath ceiling; she landedface downward, prone.

Deceleration and acceleration of gravityThedecelerative distance must be computed inthree stages, combined and confused, totaling45 inches (114 cm). The velocity at contact was66 feet (20 meters) per second (45 miles [72km] per hour). The average gravity increasewas undetermined but was minor except inimpact areas.

InjuriesThis woman had minor patternedcontusions and an H-shaped laceration on theforehead from the screen wires. All otherinjuries were minor except in the thoracic area,

where there was marked tenderness of theupper ribs on the right side near the anterioraxillary line, with slight crepitus. There wereslight rigidity of the left side of the abdomen,contusions of the right side of the chest andsevere localized ecchymosis 6 cm above thecostal margin. Roentgen examination showedfractures of the fourth, the fifth, and thesixth rib on the right side. There had been noloss of consciousness and only moderateshock.

CommentThe fall was witnessed, and thereis little doubt that the victim struck a heavy ironbar at the termination of the fall, while speedwas substantially 45 miles per hour. The

contact was in the thoracic area, with theresultant injury just described. The bar wasT-shaped structural iron, 1.5 by 1.5 inches (4by 4 cm), 6 feet 6 inches (198 cm) long andweighing 13.5 pounds (6 kg); one end of it wasembedded in masonry. The stem of the T wasup. There was a fresh, localized bend in the bar13 inches (33 cm) deep. That more severechest and other injuries were not sustained isremarkable, especially in view of the extraordi-nary demolition of structural steel and glassresulting from the force of this fall.

The woman immediately sat up, rose to herfeet and was helped through an adjacent

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window and given immediate first aid. She wasadmitted to a hospital and made a rapid,uneventful recovery.

A case in which the conditions of free falland impact were similar is summarized asfollows:

A person fell 100 feet (30 meters) onto ascreen with iron supports over a skylight, land-ing face downward and demolishing thesestructures. Injuries included fracture of the

seventh, the eighth, and the ninth rib on theright side, a right pneumothorax and subcutan-eous emphysema; there was moderate shockbut no head injuries. At the end of three weeksthe right lung was expanded and the patientstemperature was again normal; recovery wasuneventful.

CASE 5

A woman aged21,5 feet and 7 inches (170cm)tall and weighing 115 pounds (52 kg) jumpedfrom a 10th story window, falling 93 feet (28meters) into a garden where the earth had beenfreshly turned and landing nearly supine on theright side and back, with the occiput striking

the soft earth.Deceleration and acceleration of gravityThedecelerative distance was a maximum of 6inches (15 cm), according to the marks in theearth, which varied for diVerent parts of thebody. The velocity at contact was 73 feet (22meters) per second (50 miles [80 km] perhour), and the minimum gravity increase was166 g.

InjuriesThis woman fractured a rib on theright side and the right wrist. There was, how-ever, no loss of consciousness and no concus-sion.

Comment Several people were standingnearby when this patient struck the ground.She talked almost immediately and wanted to

arise but was not permitted to do so. Sheentered the hospital,where she remained for 12days. The earth in the flower bed where shelanded had been spaded to a depth of 6 or 7inches (15 to 18 cm). The earth packed hardunder the force of this fall, and the gravityincrease was estimated to have mounted tomore than 200 g toward the end of thedecelerative movement.

CASE 6

A man aged 42, of unascertained height andweight, fell 108 feet (32 meters) from a 10thstory window and landed on the hood andfenders of an automobile, face downward.

Deceleration and acceleration of gravityThedecelerative distance varied from 6 to 12 inches(15 to 30 cm) for diVerent parts of the body,and impact due to inertia of the structure wasinvolved. With a velocity at contact of 79 feet(24 meters) per second (52 miles [83 km] perhour) the gravity increases were close to 100and 200 g without inertia and other considera-tion.

Injuries This man sustained a depressedfrontal fracture of the skull, but the immediatecause of this injury was not determined. Hehad bounced from the car to the pavement.Head injuries observed in like accidents have

occurred as a result of bouncing from a decel-erative structure to a hard surface.

Comment This patient survived and is nowin good health. Unfortunately, the medical his-tory of the case is not available, but at the timeof the accident the patient was reported to havesustained no loss of consciousness, to haveslept well and to have had a good appetite. Theforce was well distributed except in the areawhere the fracture occurred.

A case in which the conditions of fallingand impact were similar is summarized asfollows:

A man fell from the top of a factory building(134 feet [40 meters]), landing face downwardon the hood and fenders of a car. The force wasnot well distributed in the abdominal area. Thelower half of the abdomen (below the umbili-cus) was strongly supported by the hood of thecar; the head and chest struck the fender,which was demolished. There were no materialfacial injuries and only brief loss of conscious-ness, with no other indications of head injuryfrom this primary fall. The man bounced fromthe car to a height of2 or3 feet (60 to90 cm)

and was observed to land head downward onthe pavement after a fall of about 5 feet (152cm). There were frontal scalp lacerations at thehair line related to this secondary fall onto thehead, and this, in itself, was consideredsuYcient to cause temporary loss of conscious-ness. Preliminary roentgen examinationshowed a line of decreased density extendingupward from the orbital plate close to thecoronal suture. The upper portion of theabdomen, ie, between the thorax and theumbilicus, received little or no support duringthe deceleration of the speed of this fall, andthere was severe shearing stress in this region.There was no apparent intrathoracic injury.The patient died 24 hours after the accident,

death being attributed to shock. At autopsy norupture of major internal organs was revealed.

CASE 7

A man aged 27, 5 feet 7 inches tall and weigh-ing 140 pounds (64 kg), jumped from the roofof a 14 story building, falling 146 feet (44meters) onto the top and rear of the deck of acoupe and landing in a semisupine position.

Deceleration and acceleration of gravityThedecelerative distance varied, the extreme depthof the dent in the car structure being 8 inches(20 cm)about 5 inches (13 cm) where thehead and shoulders struck. The velocity atcontact was 86 feet (26 meters) per second (59

miles [94 km] per hour). The gravity increasewas not estimated because of the unknown fac-tors of relative movement, inertia of the struc-ture, action of the car springs, etc.

Injuries The patient sustained numerousfractures as follows: compound, comminutedfracture of the left elbow; impact fracture of thehead and the neck of the left humerus; commi-nuted fracture through the spine of the leftscapula; compression fracture of the seventhand the eighth dorsal vertebra, and fracturethrough the base of the greater tuberosity of theischium. He suVered moderate shock but wasconscious; there were no chest or head injuries.

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During the first week in the hospital the abdo-men was distended and the patient vomited,probably evidence of some internal injury. Inthe second week jaundice developed, butotherwise recovery was uneventful. The manreturned to work two months later, when thearm was healed.

Comment The chain of injuries to elbow,shoulder, scapula, and vertebrae indicates thatthe left arm was subjected to great force, prob-

ably before the body was otherwise wellsupported. It is conjectured that the left armstruck the lower sill of the rear window beforethe rest of the body struck and dented the roofstructure. The suggestion of internal injurymay also be related to this abrupt, localizedforce, or to the steamer chair position inwhich the general force of the fall was taken.

A case in which the position of the body atthe moment of impact was similar is summa-rized as follows:

A woman, who jumped from a 17th floor,falling 144 feet (43 meters) in a similarsteamer chair position, landed on a metalventilator box 24 inches (61 cm) wide, 18

inches (46 cm) high and 10 feet (300 cm)long. The force of her fall crushed thestructure to the depth of 12 to 18 inches (30 to46 cm). Both arms and one leg extendedbeyond the area of the ventilator, withresultant fractures of both bones of both fore-arms, the left humerus and extensive injuriesto the left foot. She remembers falling andlanding. There were no marks on her head orloss of consciousness. She sat up and asked tobe taken back to her room. No evidence ofabdominal or intrathoracic injury could bedetermined, and roentgen examination failedto reveal other fractures. The average gravityincrease was a minimum of 80 g and an aver-age of 100 g.

CASE 8

In this case the history has been reconstructedfrom a paper by Turner, written in 19192:

The victim of this mishap fell from the topof a cliV320 feet (96 meters) high. The face ofthe cliV was perpendicular from top tobottom except for a slight projection half waydown which can scarcely be called a ledge forit would be quite impossible to obtain afoothold on it. The beach is described as anordinary beach with chalk boulders and a littlegravel debris. Turner stated: Some Frenchlaborers were at work on the beach at the timeand two of them noticed a falling object

against the white of the cliV

, saw this strike andbounce from the ledge already described, andhardly realized it was a man until he fell on thebeach about 50 yards from where they wereworking.

The occurrence could be classed as survivalof two falls of 160 feet (48 meters) each, theassumption being that the fall was fullychecked about midway at the ledge. There is nocertainty that the fall was free in the first phase,as the man may have brushed against the faceof the cliV prior to striking the ledge. If oneassumed that the fall was free after the manbounced from the ledge and if one deducts 50

per cent from the speed of the first 160 foot fall,because of retarding action, the resultant speedwould be 41 feet (12 meters) per second as hepassed the midway point, equivalent to a fallfrom 25 feet (8 meters) above.

The velocity on striking the beach can there-fore be regarded conservatively, as equalingthat of a fall from a height of 185 feet (57meters)65 miles (104 km) per hour.

Aside from a large tearing wound of the right

knee where a flap of superficial tissue was tornup on the anterior, external, and posterioraspects of the joint, injuries were largely con-fined to the scalp where there were about 10wounds, four of which extended down to thebone.

There was no apparent fracture of the longbones or intrathoracic or abdominal injury.The flap wound was attributed to strikingagainst the ledge in passing, the scalp woundsto stones on the beach. The head struck someobject with suYcient inertia to cause a fissuredfracture of the skull, and the patient wasunconscious for three days.

The subsequent progress was remarkably

good ..... and the only sign of any intracranialtrouble was ..... slight left facial paralysis .....with inequality of the pupils, the right being thelarger. No further symptoms were noticed, andeven these cleared up in a week or 10 days.

Turner, in remarking on the comparativelyslight nature of the injuries in this case,suggested: It is just possible that an updraughtmight have got in beneath the heavy servicegreat coat and exercised suYcient parachuteaction to considerably break the fall. This,indeed, may have contributed to the result.

The distance of the decelerative action of thebeach and the depth of the imprint of the bodywere not noted. As a decelerative distance of 9inches (23 cm) after contact with the beachwould limit the gravity increase to 191 g, inview of the other cases in evidence survival canmore probably be attributed to the decelerativefactor.

CommentSeven cases of free fall are presented in whichthe height of the fall was exactly known and theresultant speed conservatively estimated. Inestimating the gravitational increases great dif-ficulties stood in the way of exactness. Even inthe falls to earth there was variation of thedecelerative distance of the fall for various partsof the body; the hand, for instance, might be

stopped in a distance of 2 inches, whereas thehips or head might leave a mark 5 or 6 inchesdeep. In falls to structure these conditions werealso greatly confused. A head striking a fenderof a car after a long fall might leave a materialdent or distortion, but where the feet struck thefender on the other side there might be only aslight mark.

There can be no doubt that gravity increasesoccurred greatly in excess of those estimatedfor the cases reported here. In the case summa-rized in the comment on case 7, in which thefall of 144 feet terminated on a metalventilator, a typical example is provided of

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yield, or give, in structure poorly designedfor the conditions imposed on it. The metalwas light and crumpled easily when firstsubjected to force, but as it assumed its finalflattened form, extreme force was required tocrumple or flatten it further. It is probable thatits resistance induced a gravity increase greatlyexceeding 200 g as it took its final form.

Since the blood weighs about 12 times theweight of an equal volume of iron under a force

of 100 g and about 25 times the weight of ironunder a force of 200 g, it seemed probablewhen this study was undertaken that someprogressive sequence of lesions would occurdue to hydraulic action of the blood underthese excessive conditions. It was thought thatthese lesions would in themselves serve as someevidence of the force to which the body hadbeen exposed. Absence of evidence of this kindis attributed to the brevity of the force intervalsinvolved in the cases studied.

As distribution and compensation of pres-sure play large parts in the defeat of injury, it issignificant that a deep sea diver can withstandcompensated pressures exceeding 300 pounds

(136 kg) to the square inch on his body withoutinjury. The pressure rise in the cited cases ofvelocity change was not high, but it was abruptand was sustained on one side of the body only.Absence of greater injury in the pressure areasor at their edges and larger indication of burst-ing eVect and injury by distortion is notewor-thy.

Two of the cases summarized, relate to puredeceleration; two represent extensive structuraldemolition with survival injuries, and two oth-ers relate to striking specific objects with greatdestructive force and minor injury.

In cases 1 and 5 the falls were to earth, wherethe deceleration began without great impact

and the decelerative distance could be accu-rately observed by the marks of the body.

In cases 6 and 7 the falls were onto automo-biles, where the force of the body demolishedmechanical structure without excessive injuryto the body. These decelerations included iner-tia and other factors which made the decelera-tion uneven and, in parts, extreme.

In case 2 the force of the fall demolished theroof planking and broke three 6 by 2 inchbeams, with only one skeletal fracture and littleother injury.

In case 3 a wooden fence was demolished bysome anterior portion of the chest or abdomen,with trivial injury.

In case 4 a 1.5 by 1.5 inch structuralT-shaped iron bar was bent 13 inches by theanterior portion of the chest, without extensivetraumatic result. In this case the circumstancesclosely resemble those in instances in which apilot is thrown through an instrument panel,bending and breaking tubular bracing struc-ture, with minor facial and thoracic injuries.

The injuries in cases 1 through 7 can besummarized as follows:

1. There was no skull fracture or concussionin case 1, 2, 3, 4, 5, or 7.

2. Intrathoracic injury was not in evidence inany case.

3. There was no indication of material inter-

nal injury in case l, 2, 3, 4, 5, or 6.4. Fracture of the long bones of the arm

occurred in 1 case only.5. There was no fracture of the long bones of

the legs in any case.6. Damage to the rib cage occurred in case 4,

in which the localized force was high because ofthe limited area of contact with the iron bar.

7. Pelvic fracture was lacking in all casesexcept for the fractured tuberosity in case 7.

8. The chain of injury in case 7 to the arm,shoulder, scapula, and vertebrae and the cause

have already been referred to.9. One other vertebral injury occurred, in

case 2, an injury of position.Any of the foregoing injuries can be substan-

tially duplicated in a 5 foot (152 cm) fall. Incorrelating the aforementioned injuries withthose incurred in many aircraft and automobileaccidents the direct relation of force todecelerative distance must be constantly con-sidered. A person who escapes in a high speedcrash, fatal to many others, owes his life to

some decelerative interval and to a favorabledistribution of pressure.It should be borne in mind that the

decelerative distance of an airplane, crashing ata speed of 120 miles (192 km) per hour is sel-dom limited to a distance of 4 feet (122 cm)except in the demolished frontal areas. If thepilots position is to the rear, 4 feet of decelera-tion will limit the force at this point to an aver-age of 121 g. The average 50 miles (80 km) perhour crash of an automobile usually involves astopping distance greater than 2 feet (60 cm)

and the passengers could be limited to a grav-ity increase of approximately 44 g if they werein contact with or otherwise related to the

structure. A slip on the street, however, wherethe head strikes the hard pavement may inducea gravity increase exceeding 300 g because ofthe small decelerative factor involved. Here theforce is highly localized both in time and inarea, and the results are often fatal. It is signifi-cant that crash survival without injuries in air-craft and automobiles occurs under conditionswhich are seemingly extreme and that fatal

injuries are often sustained under moderateand controllable circumstances.

The mechanical causes of injury and theengineering possibilities for protection arebeyond the scope of this paper.It is suYcient tostate that the cases reported or summarized

here present physiologic evidence of wellknown mechanical and physical laws; that theprimary causes of injuryimpact and localiza-tion of forceare defeated when distributed indistance (time) and area (space), and that thebrevity of the force interval and compensationof pressure can yield amazing results acciden-tally or when converted to safety purposesthrough engineering.

The fact that these survivals occurred whenthe necessary factors were accidentally contrib-uted is strong evidence of the large increase insafety which can be provided by design.

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Conclusions

The human body can tolerate and expend a

force of 200 times the force of gravity for brief

intervals during which the force acts in

transverse relation to the long axis of the body.

It is reasonable to assume that structural

provisions to reduce impact and distribute

pressure can enhance survival and modify

injury within wide limits in aircraft and

automobile accidents.

1 Determination of the rates of descent of a falling man andof a parachute test weight. Air Corps Technical Report,No 2916. Air Corps Inform Circ Nov 24, 1928, Vol 7, No628.

2 Turner P. A fall from a cliV three hundred and twentyfeet high without fatal injuries. Guys Hosp Gaz 1919;33:2780.

Blame that also falls on parentsNo one could fail to be sorry for David Davies who was seriously injured when he fell througha skylight on the roof of his school. Whether Liverpool ratepayers should fork out compensa-tion is another matter. It is natural enough for the boys mother to blame the school becauseteachers had not warned him that if he climbed on the roof, stamped on the skylight and fellthrough, it was a 20ft drop and he might be hurt. What I find amazing is that a judge shouldconclude that the boy was only 60% responsible for the accident and the school 40%, openingthe way to compensation. The compensation is a self destructive madness which benefitsno-oneexcept the lawyers and judges whose jobs depend on it (adapted from the Mail onSunday (London), November 1999).

Death associated with soda syphon bulbA 10 year old boy has died as the result of an exploding soda syphon bulb. A coronial inquest

has established that the boy had taped three soda bulbs together with plastic insulation tapeand then placed them inside aluminium foil along with strips of toy pistol caps. This was putin a fire and exploded. A fragment of the soda syphon entered the boys forehead and, althoughthe cap weighed only three grains, the forensic pathologist commented that it had donedamage equivalent to a gunshot injury using centrefire ammunition.

It appears the boy may have got the idea from conversations at school after a Scout camp atwhich there was a demonstration using a soda bulb to propel a handmade rocket along apiece of string.The boys father had purchased a box of 10 bulbs in order that they could repeatthe activity and they had done so a number of times.

Soda bulbs are sold in supermarkets in packs of 10 for about $8.50 (Aus). There is norestriction on sale to minors. Some packs are labelled with a compressed gas green hazardlabel; all carry a warning in relation to heat, either a warning to avoid temperatures over 50 Cor to keep the bulbs in a cool place.

Australian Bomb Data Centre reports record 1011 incidents of soda bulbs used as explosivedevices reported to police since 1989 but it is generally assumed the actual figure is muchhigher.

The coroner conducted the case as an open hearing to raise public awareness of the injuryrisk. She recommended labelling to make purchasers aware of the risk associated with fire andthat retailers consider voluntary restrictions on sale to minors (taken from State CoronerVictoria Case No 861/99).

Fatalities register and suicide mappingTwo separate measures will assist in understanding death in Australia.

A new Australian register will document every drug overdose, murder, suicide, and roaddeath in the nation within 48 hours. In (what is thought to be) a world first, details of all fatali-ties, murders, and suicides will be recorded on a national database. Legal authorities say thesystem will act as an early warning system across the whole country. Various authorities will beable to have early warning of dangerous products, transport issues, extra strong or adulterateddrugs and to take early action. Initial details of each death will be supplied by police oYcersattending the scene. Full coronial inquiries will then proceed with reports and findingsincluded in the database. The National Centre for Coronial Information at Monash Univer-sity is already collecting data with the system expected to be fully operational by mid-2000.While excellent data have been available in some states for a number of years, in others therehas not even been a central coroners collection. One of the driving forces behind the nationalsystem is Victorian State Coroner, Graeme Johnstone, who said that 10 years of work has goneinto the program (Herald-Sun (Melbourne) October 1999).

In what is also claimed to be a world first, Sydney researchers have been funded by theNational Health and Medical Research Council to produce a map charting self inflicted deathsacross the country and matching them with information on depression, socioeconomic status,and a range of other factors (The Age (Melbourne) November 1999).

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