BIG BANG THEORY PHYSICS AND PHYSIOLOGY OF BLAST

Transcription

1 BIG BANG THEORY PHYSICS AND PHYSIOLOGY OF BLAST JUSTIN LEMIEUX, MD STANFORD EMERGENCY MEDICINE DISCLOSURES This presentation includes proprietary (patent-pending) technology that my team is currently developing All animals depicted were euthanized in compliance with the Humane Slaughter Act prior to training 1

2 TRAUMATIC PHYSIOLOGY 2

3 UNIQUE PATHOPHYSIOLOGY We found the wounded men [they] had an uncovered hole under a tree. Itmust have been their first action because you never have an open hole under a tree in areas that are under enemy shell fire. There were five men in the open hole. A Germanshellhadhitthetreeandburst. I checkedthem overfor bleeding andcould notfind any woundsthat required immediate attention. However, they seemed to be in a great deal of pain.our doctors checked the wounded menandcouldnotfindanybadwounds. Theywereperplexedastowhatwaswrong. The wounded men were very angry and expected us to do something so the doctors decided to give them plasma. We werejust starting togive them blood plasmawhenone by one,allfive men died. Thedoctors speculatedthat themen had so many steel splinters in them that they were all cut up inside and had bled to death internally. I was shocked by the death of men who did not seem to have any bad wounds. I was alsosurprised by the reactions of these wounded men. Doctor Danger Forward by Allen Towne, p.112 McFarland & Co. Inc. Publishers, London 2000 BLAST MECHANICS Deflagration Rapid burning with subsonic blast propagation (low-grade explosives) Detonation Supersonic ignition and blast/shock wave (high-grade explosives) Type I blast injuries 3

4 Doppler shifting 4

5 Wilson cloud formation 5

6 Sine wave to N-wave FRIEDLANDER WAVE Compression Phase Rarefaction Phase Peak Overpressure Impulse 6

7 SIMPLE/SPHERICAL WAVES Blast impulse decreases with r 3 Spalling 7

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9 DEFLAGRATION TO DETONATION TRANSITION ZND detonation model, proposed duringworld War IIindependently byy. B. Zel'dovich, John von Neumann, and Werner Döring Accelerating pressure wave within a volatile vapor cloud compresses unburnt gas ahead of the wave to autoignition. This self-driven shock wave becomes a secondary combustion zone. DEFLAGRATION TO DETONATION TRANSITION Thermobaric weapons bunker busters Pulsed detonation engines Analogous thermonuclear plasma-phase mechanism proposed for Type Iasupernovae (Sedov-Taylor) Implicated in catastrophic industrial gas explosions Famous examples include: 1970 Port Hudson, MO propane pipeline break 1974 Flixborough, England chemical plant 1989 Pasadena, TX chemical plant 2005 Hertfordshire, England oil storage terminal 9

10 EXPERIMENTAL PDE COMPLEX BLAST WAVES 10

11 COMPLEX BLAST WAVES COMPLEX BLAST WAVES 11

12 SHAPED CHARGES Munroe-Neumann Effect SHAPED CHARGES Misznay-Schardin Effect 12

13 EXPLOSIVELY-FORMED PENETRATORS / SELF-FORMING FRAGMENTS SPALLING 13

14 BRISANCE STRESS AND SHEAR WAVES (MACH REFLECTION) 14

15 BLAST INJURY CLASSIFICATION Primary Caused by the direct effects of the blast wave/overpressue itself Injury is most severe in tissues of heterogeneous density, particularly air/fluid interfaces (ear, lung, GI tract, brain, eye) Secondary Caused by debris/shrapnel propelled by the blast-force Penetrating blast injury Tertiary Caused by acceleration and deceleration of the body and its impact with other objects E.g. patient thrown through the air and striking another object BLAST INJURY CLASSIFICATION Quaternary All other miscellaneous traumatic injuries caused by explosions E.g. Burns, crush injuries caused by structural collapse, toxic inhalation, exacerbation of chronic illness Quinary Infectious or radioactive materials added to a device and released with detonation Dirty Bombs 15

16 J Cereb Blood Flow Metab Feb; 30(2): Ibolja Cernak, Linda J Noble-Haeusslein TYPE I BLAST PATTERNS Ear injury TM rupture at 5 psi Respiratory injury lungs and bronchi: lung damage at 15 psi upper airways (trachea, pharynx and larynx) bronchopleuralfistulae nasal passages and sinuses Bowel injury high pressures: much more common in water LD 50 approximately 50 psi AGE is leading cause of sudden death due to blast Repeated exposure to blast waves significantly increases severity of injury/likelihood of death 16

17 AUDITORY BAROTRAUMA Ear is most susceptible organ TM rupture(most common) Hemotympanum without rupture Ossicle fracture or dislocation Round and oval window injury May present as tinnitus, vertigo, otalgia, bleeding from canal Once thought to be a marker for occult pulmonary injury but found low sensitivity and specificity PULMONARY BAROTRAUMA Most common fatal primary blast injuries May include: PTX/bronchopleural fistula (CT with air leak) Pulmonary contusion Blast lung Arterial gas embolism (common) SIRS, lipoxygenation, thrombosis, DIC ARDS as a result of direct lung injury or shock from other bodily injuries 17

18 BLAST LUNG Most common fatal primary blast injury among initial survivors Signs are usually present during initial evaluation but can be delayed up to 48 hours Severe pulmonary contusions and hemorrhage May present with chest pain, dyspnea, cough, hemoptysis, hypoxia Classic butterfly pattern on CXR Anticipate decompensation with sedation/intubation Chest tube recommended prior to air transport BLAST LUNG 18

19 PULMONARY CONTUSION ARTERIAL GAS EMBOLISM Primary cause of death within first hour Can affect brain, spinal cord, and anything else Can present as MI, stroke, acute abdomen, blindness, spinal cord injury Must exclude symptoms from the result of direct trauma Consider hyperbaric oxygen, be ready to treat seizure 19

20 THORACIC BAROTRAUMA Triad of bradycardia, hypotension, and apnea Vagally-mediated +/- direct myocardial depression Blood pressure falls in the absence of compensatory increase in SVR Can cause death even in the absence of observable physical injury Onset is in seconds. Recovery occurs in 15 minutes 3 hours if not fatal THORACIC BAROTRAUMA J Trauma Jul;47(1): Shock after blast wave injury is caused by a vagally-mediated reflex. Irwin RJ,Lerner MR,BealerJF,MantorPC,Brackett DJ,TuggleDW. Bradycardia, hypotension, and absence of compensatory peripheral vasoconstriction, typically seen in animals subjected to a blast pressure injury, were prevented by bilateral cervical vagotomy and intraperitoneal injection of atropine methyl-bromide. 20

21 THORACIC BAROTRAUMA Exp Physiol May;86(3): Reflex nature of the cardiorespiratory response to primary thoracic blast injury in the anaesthetised rat. Ohnishi M,KirkmanE,Guy RJ,Watkins PE. The bradycardia and apnea following thoracic blast were abolished by cervical vagotomy while the hypotension was attenuated. Atropine caused a significant reduction in the bradycardia but did not modulate either the hypotension or apnea. VASCULAR BAROTRAUMA Tex Heart Inst J. 2009;36(3): Pericardial tamponade consequent to a dynamite explosion: blast overpressure injury without penetrating trauma. OzerO,Sari I,DavutogluV,YildirimC. J Emerg Med Aug;43(2):263-5 Left ventricular rupture with resulting cardiac tamponade due to blast force trauma from gunshot wound. Branch CF, Adams J. Ventricular rupture and tamponade can occur in the absence of penetrating injury 21

22 ABDOMINAL INJURY High-energy blast and/or close proximity More common in underwater blasts Solid organ injury from blast wave is rare and seen only in very powerful blast Intestinal barotrauma Large intestine is the most commonly affected but any portion of the GI tract can suffer injury Associated with high mortality rate Can be occult until signs of an acute abdomen or sepsis INTESTINAL BAROTRAUMA Acute/Delayed perforation of the bowel No obvious external wound easily missed Early hemorrhage Delayed sepsis Pathology Mesenteric tears Hematomata in bowel wall Intraluminal hemorrhage Delayed perforation up to 8 days after injury 22

23 INTESTINAL BAROTRAUMA May present with abdominal pain, nausea, vomiting, hematemesis, BRBPR, rectal pain, tenesmus, testicular pain, unexplained hypovolemia, but often no signs or symptoms on initial presentation Suspect in under water blast exposure, CT if stable for scan, serial exams, H/H, FOBT indicated as CT can miss these injuries. OR if highly suspected. 23

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25 QUESTIONS? 25