Pressure Thresholds - What your medic needs to know
Published on: Mar 4, 2016
Transcripts - Pressure Thresholds - What your medic needs to know
PRESSURE THRESHOLDS:What your medic needs to know
Numerous studies point out the dangers of overpressure in very real terms
he United States Department of Defense has
reported more than 250,000 Service
members have suffered from a traumatic
brain injury (TBI) between the years 2000 and 2012.1
For this reason, it’s not surprising that TBI has
become synonymous with the term “signature injury
of modern war.”
The main culprit of injury in blast TBI is peak
overpressure caused by shockwaves from an explosion.
The shockwave is undetectable to the human-eye, but
can create lasting damage to the brain and body.
Soldiers and Tactical Officers are often exposed to
harmful levels of peak overpressure both in training
and in the field. To counteract this threat, measuring
an individual’s exposure level is key.
Overpressure from an explosive event is measured in
pounds per square inch (psi), and like any form of
measurement, understanding what this metric means
is key. So what are the thresholds for bodily exposure
When talking about minimum safe distance, it’s
common to hear law enforcement agencies and
military operators cite 4 psi as a “safe” baseline
threshold. This is consistent with the assumptions
underlying the safe standoff curves currently used by
most military and law enforcement breachers.
However, research indicates this may be an
oversimplification, as multiple low level exposures can
still be damaging.
In addition to the damaging effects of a single event,
recent and ongoing studies of repeated blast exposures
have revealed that there is a cumulative effect
associated with chronic low-level blast (LLB)
exposures. These findings indicate that—like
concussive TBI injuries common in contact sports—
even small, cumulative exposures can be damaging.
Furthermore, factors other than frequency of exposure
can contribute to injury severity. Variability of factors
such as blast duration, reflections, bodily condition,
and dehydration can greatly affect degree of injury.2
For all these reasons, measuring exposure level
provides critical information to the health care
provider aiding in triage and treatment of this
This leads us to the original question: what are the
thresholds for bodily exposure to blast overpressure?
Simply put, a single exposure of 0 – 4 psi is typically
safe, though it’s critical to seek medical attention if
you’re not feeling well with symptoms such as
headaches or nausea. This is because it only takes 3
blast exposures at 3 psi to cause gastrointestinal and
pulmonary injury. 5 psi is enough to rupture an3
eardrum, and as exposure levels climb further
Defense and Veterans Brain Injury Center. http://dvbic.dcoe.mil/dod-worldwide-numbers-tbi1
Defense Center of Excellence for Psychological Health & Traumatic Brain Injury. Traumatic Brain Injury and Eﬀects of Altitude: An Analysis of Literature.2
September 14, 2010.
Dr. Daniel L Johnson, et al., Blast Overpressure Studies with Animal and Man. USAMRDC. Nov. 15, 1993.3
TACTICAL TECHNOLOGY ADVANCEMENTS
towards a peak overpressure of 16, the likelihood of
Two recent studies have shed new light on the
neurological impacts of blast overpressure exposure:
the Quantico Breacher Injury Study (QBIS) and the
Preventing Violent Explosive Neurological Trauma
(PREVENT) study.The QBIS study found that a single
blast overpressure exposure of 13 psi showed no changes
in neurobehavioral testing or imaging of the brain.
However, the PREVENT study using non-human
primates identified neurological changes post-mortem
as low as 12 psi in the absence of any symptoms.5
Additionally, the PREVENT study using swine found
biomarkers for brain injury and inflammation for
blast overpressure exposures above 24 psi. As the6
peak overpressure increases, the effects are more
devastating: 30-40 psi is the threshold for lung injury
and at 100 psi there is possibility of death.7
As mentioned earlier, it is not uncommon for a
Soldier or Tactical Officer to be subjected to multiple
blast events while performing his or her job. Multiple
studies, including one recently published in the
Journal of Neurotrauma, suggest that LLB causes a8
measurable degree of brain agitation known to cause
cognitive impairment and depression. In order to
protect our heroes, we need to be able to detect,
record, and monitor repeated exposures.
This is where the Blast Gauge™ System comes in.
Weighing less than an ounce, the Blast Gauge is a
powerful, easy-to-use overpressure sensor that
automatically records an operator’s exposure to an
explosive event. With the push of a button, the gauge
emits a discreet visual cue with green, yellow and red
status LEDs providing instant feedback on
The system’s ability to capture and record detailed
signatures from events provides invaluable
information that can be downloaded via a micro-USB
connection and used by medical personnel to aid in
the triage and treatment of TBI. In-depth reports can
be used to track cumulative exposure and create a
permanent health record for correlation to long-term
effects. Exposure can be measured and recorded in
both training and combat scenarios such as from
improvised explosive devices (IEDs), shoulder fired
weapons, and artillery live fire training.
The life-preserving aspects of the Blast Gauge
System are recognized by military and law
enforcement communities across the world.
Militaries, Bomb Squads, SWAT Teams, and other
Tactical Officers are often exposed to overpressure
from explosive breaching, flashbangs and IEDs, thus
the need for adopting an advanced sensor that can
measure exposure levels.
You may be wondering what more can be done to
protect your operators from this threat. Knowledge of
overpressure exposure is essential and can be achieved
by wearing advanced overpressure sensors in both
training and operations. Without them, you have no
way of knowing the magnitude of blasts and could be
guessing at the extent of possible injury.
Authored by Scott Featherman, Captain (R), U.S. Army,
101st Airborne (Air Assault). Featherman has signiﬁcant
experience leading breaching teams and currently serves as
Product Specialist at BlackBox Biometrics® Inc.
BlackBox Biometrics specializes in developing innovative
technology that measures the unseen impact of concussive
injuries, aiding in triage and treatment.
Find out more at blastgauge.com.
PSI level Possible Injury
3 (3+ blasts) Gastro-intestinal and pulmonary injury
5 Eardrum Rupture (threshold)
12 Neurological changes, no symptoms
24 Mild Neurological Damage
30-40 Moderate Neurological Damage,
Possible Blast Lung (threshold)
75 Lung Damage in 50% of patients
100 Possibility of death
Stewart, Charles. Blast Injuries: Preparing for the Inevitable. Emergency Medical Practice. Vol. 8 No. 4. April 2006.4
Lu, Jia, et al., “Eﬀect of Blast Exposure on the Brain Structure and Cognition in Macaca fascicularis.” Journal of Neurotrauma. May, 2012.5
Ahmed, Farid. Time dependent changes of protein biomarker levels in the cerebral spinal fluid after blast traumatic brain injury. Electrophoresis. 2012.6
Dr. Daniel L. Johnson. Nonauditory Damage Risk Assessment for Simulated Muzzle Blast from a 120mm M121 Mortar System. USAMRMC. Oct. 1997.7
Charmaine Tate and colleagues. Serum Brain Biomarker Level, Neurocognitive Performance, and Self-Reported Symptom Changes in Soldiers Repeatedly Exposed8
to Low-Level Blast: A Breacher Pilot Study. Vol. 30 No. 19. October 2013.