Parallels between blast and ballistic pressure waves

[Michael Courtney]

There are a number of historical and scientific parallels regarding neurological effects of blast and ballistic pressure waves.

Neurological effects of blast pressure waves were given the name "shell shock" in WWI, and observations of cognitive impairments were widespread. However, the lack of easily observable effects in tissue analysis, combined with governmental motives to return soldiers to service motivated Great Britain to greatly downplay the scientific support for the neurological effects of blast pressure wave exposure. The British government maintained that soldiers complaining of "shell shock" were avoiding their military duties and merely suffering from psychological trauma. (Today, both psychological trauma, in the form of PTSD, and physical brain injury, are recognized effects of blast exposure. Research is ongoing to better understand causes, diagnosis, and treatments.)

It is unclear when the term "hydrostatic shock" first came into use to describe remote effects of penetrating projectiles, but Frank Chamberlin, a WWII trauma surgeon and ballistics researcher, noted remote pressure wave effects. Other scientists of this era noted remote pressure wave effects in the peripheral nerves (Livingstone et al. and Puckett et al.) However, even though there was support for the idea of neural effects of ballistic pressure waves in the medical and scientific commuities, the phrase "hydrostatic shock" was used mainly by gunwriters (O'Conner, for example) and the small arms industry (Weatherby, for example).

Rejection of "hydrostatic shock” by Martin Fackler and others seemed like an instinctive reaction against unproven marketing claims of the small arms industry in favor of more easily demonstrated wounding mechanisms. These authors didn't provide any more concrete evidence against remote neural effects of ballistic pressure waves than the government of Great Britain provided against "shell shock." Rather than provide proof of absence, the case against "shell shock" and BPW effects both relied on absence of proof.

The denials of "shell shock" and "hydrostatic shock" (remote BPW effects) as real wounding mechanisms persisted for some time because of the absence of easily observable tissue damage. However, progress in tissue analysis (histology), careful experiments using behavioural observations, and improved understanding of traumatic brain injury (TBI) eventually allowed support in animal models.

Blast and ballistic pressure waves appear to have both numerous physical similarities in tissue, as well as similarities in how they cause neural effects in the brain. In tissue, both types of pressure waves have similar magnitudes, duration, and frequency characteristics. Both have been shown to cause damage in the hippocampus and hypothalamus. It has been hypothesized that both reach the brain from the thoracic cavity via major blood vessels.

For example, I. Cernak, a leading researcher in blast wave injury hypothesized, "alterations in brain function following blast exposure are induced by kinetic energy transfer of blast overpressure via great blood vessels in abdomen and thorax to the central nervous system." This hypothesis is supported by observations of neural effects in the brain from localized blast exposure focussed on the thoracic cavity in an animal model.

Michael Courtney

 

[Mad Magyar]

The denials of "shell shock" and "hydrostatic shock" (remote BPW effects) as real wounding mechanisms persisted for some time because of the absence of easily observable tissue damage.

There can't be too much denial since this is the basis for high-velocity rds, such as in the .357.....I'm not sure you have a question in your post, but high-speed X-ray photos show that the faster bullet causes a larger temporary cavity, a result of a momentary shock wave in the tissues that are largely water. Some call this "hydrostatic shock"; a fact....
I believe your research is sorely out-of-date....

 

[JDGray]

The only gun to put off a blast wave that I've fired, was a 50 cal Barrett. After 40 rds, of standing behind, and 3 rds firing, I couldn't get enough! Talk about a pressure wave... All our faces looked like this It definately did something to our brains.

 

[Cosmoline]

Nobody seriously denies that a .30 cal. rifle bullet at over 2,500 fps will generate a shockwave sufficient to create serious tissue damage and secondary wounding. I think the debate is whether or not you can get any demonstrably better results by making a standard handgun round slightly faster by decreasing bullet weight. I remain very skeptical on that score.

 

[DENALI]

Perhaps I'm in error but I thought hydraulic shock was the term, and it referenced a blood pressure spike that was overwhelming and could actually be the result of either or?

 

[jlbraun]

Hydrostatic shock causing a large temporary cavity as a wounding method has been largely debunked, otherwise the 5.45x39mm round would have worked better.

http://www.btammolabs.com/fackler/ak74_wounding_potential.pdf

Fackler found that most tissues were too stretchy to tear even when a large temporary cavity was formed.

Fragmentation and penetration are the primary means of wounding.

"Neural effects" from a bullet hitting you sounds to me like non-falsifiable psuedoscience.

Remember, a lot of people when shot with rifle rounds don't even realize they've been hit.

 

[Jim K]

In WWI, the term "shell shock" was used to describe not only the effect of blast pressure waves, but the general effect on the body of continual combat and continual shelling, even if the explosions were not close enough to have a direct effect. AFAIK, there was nothing like it in WWII or later wars.

Imagine wearing wet, dirty clothes and soiled underwear, standing up or trying to sleep in knee-deep water and mud for days, and having a hundred rock band drummers pounding away for hours on end. Then add the real possibility that the enemy arty may shift at any time and drop a shell right on your head. Tension, lack of sleep, total system collapse all added up to more than a man could take. The result was "shell shock" or "combat fatigue."

I suspect the actual blast effect from close shell bursts was only one factor in "shell shock."

Jim

 

[REC]

In many cases, victims of "shell shock" were not exposed to to blast pressure at all. In other many cases, large numbers of men were exposed to prolonged brass pressures without manifesting any symptoms of "shell shock."

 

[Michael Courtney]

In many cases, victims of "shell shock" were not exposed to to blast pressure at all. In other many cases, large numbers of men were exposed to prolonged brass pressures without manifesting any symptoms of "shell shock."

Of course, the term "shell shock" as used in WWI included many cases of what we would call "PTSD" today in addition to what is known as traumatic brain injury (TBI). The symptoms of TBI can be very similar to PTSD, and modern diagnostic methods have come a long way in distinguishing between them, but there is additional progress to be made.

The point in the original post was that many cases of "shell shock" in WWI and WWII would be accurately diagnosed as TBI today were misdiagnosed as merely psychological trauma. The British government's desire to return soldiers to service was so great that they downplayed the genuine brain injury aspects of "shell shock" and even banned the term.

See:

Blast-Related Traumatic Brain Injury: What is Known, Taber et al., J Neuropsychiatry Clin Neurosci, 18:2, Spring 2006.

Shell Shock and Mild Traumatic Brain Injury: A Historical Review, Jones et al., Am J Psychiatry 2007; 164: 1641-1645


"Combat fatigue" was a euphamism that downplayed the potential physical injury associated with "shell shock." There was an active and ongoing debate as to whether the symptoms of "shell shock" were associated with brain injury. During WWI, the term "commitio cerebri" was used in cases where a physical injury to the brain was believed to be involved. By WWII, the diagnosis for "shell shock" was "postconcussion syndrome" in cases where a brain injury was believed to be the cause.

Michael Courtney

 

[Michael Courtney]

Hydrostatic shock causing a large temporary cavity as a wounding method has been largely debunked, otherwise the 5.45x39mm round would have worked better.

The term "hydrostatic shock" was never really well defined. It seemed to evolve from an idea that probably originated with Frank Chamberlin, a WWII trauma surgeon and ballistics researcher. Chamberlin himself was reluctant to use the term "shock" because of the ambiguity between physiological shock and shock waves.

Chamberlin wrote about "explosive effects" and "hydraulic effects" writing [CHA66]:

In a live animal . . . the large wounds in 99.9% of the cases, without a doubt, are due to liquids in the tissues and cavities. Here your liquids are put in motion by 'shock waves' or hydraulic effects . . . the effects and destruction of tissue extend in all directions far beyond the wound axis.

Chamberlin had more in mind that temporary cavitation. Hydraulic effects certainly include temporary cavitation, and Martin Fackler referred to the temporary cavity as the inertial component of the pressure wave. In Chamberlin's mind, hydraulic effects included remote effects on the central nervous system:

If I had to pick one of these theories as gospel, I'd still go along with the Hydraulic Reaction of the Body Fluids plus the reactions of the Central Nervous System.

Today, we define the ballistic pressure wave to include every force per unit area that can be measured with a high-speed pressure transducer. Ming et al. [MYR88] identify features in their high-speed pressure transducer measurements as being due to temorary cavitation, but the pressure impulse is more complex than mere temporary cavitation.

"Neural effects" from a bullet hitting you sounds to me like non-falsifiable psuedoscience.

Remember, a lot of people when shot with rifle rounds don't even realize they've been hit.

Pressure wave magnitudes are properly parameterized in terms of the forces between bullet and tissue rather than the impact velocity. Some handgun loads that expand and transfer a lot of energy in a short distance can impart larger pressure waves than FMJ rifle bullets that fail to fragment or tumble.

There is a lot of scientific literature supporting the hypothesis that ballistic pressure waves produce remote injury in the brain:

1) Pressure pulses inducing incapacitation and brain injury in laboratory animals [THG97, TLM05].
2) Ballistic pressure waves originating remotely from the brain causing measurable brain injury in pigs and dogs [SHS87, SHS88, SHS90a, SHS90b, WWZ04].
3) Experiments in animals showing the probability of rapid incapacitation increases with peak pressure wave magnitude [COC07b, COC06b, COC07a].
4) Analysis of epidemiological data showing that the probability of incapacitation increases with the peak pressure wave magnitude [COC06a].
5) Brain damage occuring without a penetrating brain injury in a case study [THG96, COC07b].
6) Blast waves causing brain injury without penetrating injury or blunt force trauma [MAY97, TAH98, CWJ01].

The paper by Cernak et al. is particularly interesting. This group focussed a pressure wave in the lungs of animal test subjects and detected remote damage in the brain.

There is considerable published data supporting the pressure wave hypothesis. In contrast, there is very little published data contradicting it.

Michael Courtney

REFERENCES:

[COC06a] Courtney M, Courtney A, http://arxiv.org/ftp/physics/papers/0701/0701266.pdf

[COC06b] Courtney M, Courtney A, http://arxiv.org/ftp/physics/papers/0702/0702107.pdf

[COC07a] Courtney M, Courtney A: Experimental Observations of Incapacitation via Ballistic Pressure Wave without a Wound Channel,
www.ballisticstestinggroup.org/lotor.pdf

[COC07b] Courtney A, Courtney M: Links between traumatic brain injury and ballistic pressure waves originating in the thoracic cavity and extremities, Brain Injury, Volume 21, Issue 7 June 2007, pages 657 – 662. Pre-print available at www.ballisticstestinggroup.org/tbipwave.pdf

[CWJ01] Cernak I, Wang Z, Jiang J, Bian X, Savic J: Ultrastructural and functional characteristics of blast injury-induced neurotrauma. Journal of Trauma 2001;50(4):695-706

[MAY97] Mayorga MA: The pathology of primary blast overpressure injury. Toxicology 1997;121:17-28

[SHS87] Suneson A, Hansson HA, Seeman T: Peripheral High-Energy Missile Hits Cause Pressure Changes and Damage to the Nervous System: Experimental Studies on Pigs. The Journal of Trauma. 27(7):782-789; 1987.

[SHS88] Suneson A, Hansson HA, Seeman T: Central and Peripheral Nervous Damage Following High-Energy Missile Wounds in the Thigh. The Journal of Trauma. 28(1 Supplement):S197-S203; January 1988.

[SHS90a] Suneson A, Hansson HA, Seeman T: Pressure Wave Injuries to the Nervous System Caused by High Energy Missile Extremity Impact: Part I. Local and Distant Effects on the Peripheral Nervous System. A Light and Electron Microscopic Study on Pigs. The Journal of Trauma. 30(3):281-294; 1990.

[SHS90b] Suneson A, Hansson HA, Seeman T: Pressure Wave Injuries to the Nervous System Caused by High Energy Missile extremity Impact: Part II. Distant Effects on the Central Nervous System. A Light and Electron Microscopic Study on Pigs. The Journal of Trauma. 30(3):295-306; 1990.

[TAH98] Trudeau DL, Anderson J, Hansen LM, Shagalov DN, Schmoller J, Nugent S, Barton S: Findings of mild traumatic brain injury in combat veterans with PTSD and Mayorga MA: The pathology of primary blast overpressure injury. Toxicology 1997;121:17-28.

[THG96] Treib J, Haass A, Grauer MT: High-velocity bullet causing indirect trauma to the brain and symptomatic epilepsy. Military Medicine 1996;161(1):61-64

[THG97] Toth Z, Hollrigel G, Gorcs T, and Soltesz I: Instantaneous Perturbation of Dentate Interneuronal Networks by a Pressure Wave Transient Delivered to the Neocortex. The Journal of Neuroscience 17(7);8106-8117; 1997.

[TLM05] Thompson HJ, Lif****z J, Marklund N, Grady MS, Graham DI, Hovda DA, McIntosh TK: Lateral Fluid Percussion Brain Injury: A 15-Year Review and Evaluation. Journal of Neurotrauma 22(1):42-75; 2005.

[WWZ04] Wang Q, Wang Z, Zhu P, Jiang J: Alterations of the Myelin Basic Protein and Ultrastructure in the Limbic System and the Early Stage of Trauma-Related Stress Disorder in Dogs. The Journal of Trauma. 56(3):604-610; 2004.

[CHA66] Chamberlin FT, Gun Shot Wounds, in Handbook for Shooters and Reloaders, Vol. II, Ackley PO, ed., Plaza Publishing, Salt Lake City, Utah, 1966.

[MYR88] Ming L, Yu-Yuan M, Ring-Xiang F, Tian-Shun F: The characteristics of pressure waves generated in the soft target by impact and its contribution to indirect bone fractures. The Journal of Trauma 28(1) Supplement: S104-S109; 1988.

 

[Dr.Carbine]

Death by concussion

I've read of cases where soldiers were killed by a near miss of an artillery shell, but were not killed by the shrapnel, only the blast. What is the mechanism that causes death from the concussion alone? Are the internal organs or brain torn or smashed, but yet there is no wound on the body?

 

[Michael Courtney]

I've read of cases where soldiers were killed by a near miss of an artillery shell, but were not killed by the shrapnel, only the blast. What is the mechanism that causes death from the concussion alone? Are the internal organs or brain torn or smashed, but yet there is no wound on the body?

Effects in the lungs and intestines are the easiest to observe, but these usually take some time to be fatal. There have been occasional cases where death was immediate and was not accompanied by externally visible signs, suggesting severe and immediate traumatic brain injury.

It has never been debated whether or not the blast alone can kill or injure, the debate was whether the blast alone can cause brain injury. This has now been established with a high confidence level.

In the case of most improvised explosive devices, you've got to be within 1-2m of the explosion for the blast itself (rather than a projectile or blunt force trauma) to kill you. However, the evidence is clear that mild to moderate traumatic brain injury can occur at distances beyond which the blast can be fatal or even induce significant lung injury (blast lung).

Michael Courtney

 

[Cosmoline]

Perhaps I'm in error but I thought hydraulic shock was the term, and it referenced a blood pressure spike that was overwhelming and could actually be the result of either or?

Maybe we need to come up with a term besides "shock," which is ambiguous. Shock can mean:

Physical shock in a medical sense, where the body shuts down from loss of 02 to the cells.

Or it can mean "shock" in a mental sense--as in the "shock" of realizing you are hit.

Or it can mean "shock" in a kinetic sense, as in the the "shock" of the bullet's raw energy.

Or it can mean shock in the sense of hydrostatic shockwave, creating the temp. cavity and waves in the body's tissue as the bullet passes through and pushes them away.

Or as in the OP it can mean "shell shock" in the physical sense which is what happens when a massive shockwave literally knocks the brain back and forth in the skull, bruising it and causing it to swell. To add to the confusion "shell shock" can also mean PTSD.

All of these get tossed around when we're talking about the "shock" of getting shot.

 

[Cosmoline]

Hydrostatic shock causing a large temporary cavity as a wounding method has been largely debunked, otherwise the 5.45x39mm round would have worked better.

I wouldn't say that. The "explosive" effects of 7mm to 30 cal rounds hitting human flesh in excess of about 2,200 fps were noticed as far back as the Spanish-American war. And all you have to do is look at the bruising and secondary bleeding around an animal's wound when hunting to see that the supersonic stretching of tissues by a high velocity rifle bullet can indeed cause secondary wounds and even tear vital parts of the circulatory system. The body *can* flex to some extent to be sure. But there is a limit. Here's a good example of a rifle bullet that would exceed that limit:

http://www.barnesbullets.com/videos/308_180gr_TSX_6fps_logo.wmv

I would say, however, that in order to reach that level of secondary destruction with a handgun you need to move into the realm of the high end magnums. A hot .44 mag, a .454 Casull or the X-frame magnums can deliver some awesome damage beyond the wound channel even without reaching super high velocities. This is how you end up getting cracked boards below the gelatin, as here:

http://www.brassfetcher.com/Speer240grainJHP.html

ouch!

 

[jlbraun]

This is how you end up getting cracked boards below the gelatin, as here:

And this is why "hydrostatic shock" as a wounding method is hard to sort out because of all the anecdotal evidence surrounding it. "Broken boards" in no way are similar to the effect a bullet has on flesh. Boards are rigid. They break instead of deform. Flesh is not rigid. It deforms elastically with an impact and is rarely damaged.

Yes, the flesh that stretches will be bruised. But not significantly damaged at all.

 

[RyanM]

Rejection of "hydrostatic shock” by Martin Fackler and others seemed like an instinctive reaction against unproven marketing claims of the small arms industry in favor of more easily demonstrated wounding mechanisms. These authors didn't provide any more concrete evidence against remote neural effects of ballistic pressure waves than the government of Great Britain provided against "shell shock." Rather than provide proof of absence, the case against "shell shock" and BPW effects both relied on absence of proof.

You have to remember, Fackler was mainly fighting against people who believed that the "shock" effect of high-velocity rifle bullets (even FMJs) would cause devitalization of any tissue in a wide radius around the bullet wound. SOP in some places was to excise tissue in a several inch radius around any high-velocity gunshot wound, whether or not such tissue was actually necrotic or not; they expected the tissue to die due to "hydrostatic shock" effects, and so exised it before it would be a problem. Fackler showed that this was absolutely ridiculous, and bordering on butchering their patients.

 

[Michael Courtney]

Maybe we need to come up with a term besides "shock," which is ambiguous. Shock can mean:

Physical shock in a medical sense, where the body shuts down from loss of 02 to the cells.

Or it can mean "shock" in a mental sense--as in the "shock" of realizing you are hit.

Or it can mean "shock" in a kinetic sense, as in the the "shock" of the bullet's raw energy.

Or it can mean shock in the sense of hydrostatic shockwave, creating the temp. cavity and waves in the body's tissue as the bullet passes through and pushes them away.

Or as in the OP it can mean "shell shock" in the physical sense which is what happens when a massive shockwave literally knocks the brain back and forth in the skull, bruising it and causing it to swell. To add to the confusion "shell shock" can also mean PTSD.

All of these get tossed around when we're talking about the "shock" of getting shot.

Great point. Frank Chamberlin avoided the use of the term "shock" when describing these effects preferring the terms "explosive effects" and "hydraulic reaction." His reasoning was very similar to yours.

In our own scientific work, we use the term "ballistic pressure wave" which is unambiguous and defined to be the "force per unit area that would be measured with a high-speed pressure transducer."

Michael Courtney

 

[Michael Courtney]

And this is why "hydrostatic shock" as a wounding method is hard to sort out because of all the anecdotal evidence surrounding it. "Broken boards" in no way are similar to the effect a bullet has on flesh. Boards are rigid. They break instead of deform. Flesh is not rigid. It deforms elastically with an impact and is rarely damaged.

Yes, the flesh that stretches will be bruised. But not significantly damaged at all.

The scientific evidence cited above shows that effects of "hydrostatic shock" go beyond effects of temporary cavitation and include remote neural effects.

Frank Chamberlin, a World War II trauma surgeon and ballistics researcher, noted remote pressure wave effects. Col. Chamberlin described what he called “explosive effects” and “hydraulic reaction” of bullets in tissue:

. . . liquids are put in motion by ‘shock waves’ or hydraulic effects . . . with liquid filled tissues, the effects and destruction of tissues extend in all directions far beyond the wound axis. (See: Chamberlin FT, Gun Shot Wounds, in Handbook for Shooters and Reloaders, Vol. II, Ackley PO, ed., Plaza Publishing, Salt Lake City, Utah, 1966.)

He avoided the ambiguous use of the term “shock” because it can refer to either a specific kind of pressure wave associated with explosions and supersonic projectiles or to a medical condition in the body.

Col. Chamberlin recognized that many theories have been advanced in wound ballistics. During World War II, he commanded an 8500 bed hospital center that treated over 67,000 patients during the fourteen months that he operated it. P.O. Ackley estimates that 85% of the patients were suffering from gun shot wounds. Col. Chamberlin spent many hours interviewing patients as to their reactions to bullet wounds. He also conducted many live animal experiments after his tour of duty. On the subject of wound ballistics theories, he wrote:

If I had to pick one of these theories as gospel, I’d still go along with the Hydraulic Reaction of the Body Fluids plus the reactions on the Central Nervous System.

Michael Courtney