Oxygen delivered under pressure, Hyperbaric Oxygen Therapy (HBOT) is one of the most
powerful drugs known to man. Simultaneously, HBOT delivers the substrate of life, oxygen, for
which there is no substitute. HBOT has profound beneficial effects on injury pathophysiologic
processes that are common in military casualties. Moreover, it has been shown to positively
impact traumatic brain injury, compartment syndrome, burns, hemorrhage, and reperfusion
injury. These injuries and injury processes comprise the bulk of battlefield casualties. With
timely intervention of HBOT the morbidity and mortality of injured soldiers should substantially
improve as they have in their civilian counterparts. Past foreign military experience strongly
suggests this benefit in extremity wounds and it is our conviction that United States soldiers
deserve nothing less. This is the goal of the Brain Injury Rescue & Rehabilitation Project (DoDBIRR).
HBOT has both acute and chronic drug effects. HBOT exerts these effects by obeying the
Universal Gas Laws, the most important of which is Henry’s Law (2). Henry’s Law states that
the concentration of a gas in solution is proportional to the pressure of that gas interfacing with
the solution.
At the point of three atmospheres absolute of pure oxygen (3 ATA), just slightly more than the
amount the U.S. Navy has used for 50 years in the treatment of divers with decompression
sickness, we can dissolve enough oxygen in the plasma to render red blood cells useless. Under
these conditions as blood passes through the tiniest blood vessels tissue cells will extract all of
the dissolved oxygen in the blood without touching the oxygen bound to hemoblogin. This
amount of dissolved oxygen alone can exceed the amount necessary for the tissue to sustain life.
In other words, you don’t need red blood cells for life at 3 ATA of 100% oxygen. This ability to
maintain life without blood has obvious potential to battlefield casualties awaiting transfusion.
As a result of Henry’s Law HBOT is able to exert a variety of drug effects on acute
pathophysiologic processes. These have been well documented over the past 50 years and
include reduction of hypoxia (lack of oxygen), inhibition of reperfusion injury (immune response
to injury), reduction of edema (swelling), blunting of systemic inflammatory responses, and a
multitude of others. In addition, repetitive HBOT in wound models acts as a DNA stimulating
drug to effect tissue growth. HBOT has been shown to interact with the DNA of cells in
damaged areas to begin the production of repair hormones, proteins, and cell surface receptors
that are stimulated by the repair hormones. The resultant repair processes include replication of
the cells responsible for tissue strength (fibroblasts), new blood vessel growth, bone healing and
strengthening, and new skin growth.
In the past 12 years scientific research has unequivocally shown that the only drug to completely
or nearly completely reverse the reperfusion injury process is hyperbaric oxygen. This is a
physiological reaction of the body to trauma is a major source of injury that battlefield casualties
experience. In multiple experiments with different animal models, different organ systems,
different types of blood flow reduction or absence (e.g., heart attack, stroke, cardiac arrest,
1. carbon monoxide, tourniqueting of an extremity, etc.) timely HBOT within hours of reperfusion
injury has been shown to completely or nearly completely reverse reperfusion injury.
Simultaneously, due to HBOT’s ability to dissolve large amounts of oxygen in the liquid portion
of the blood, oxygen-enriched plasma is able to reach damaged areas of tissue not accessible by
normal blood flow and restore oxidative function to these areas. The net result is a dramatic
reduction in the secondary injury process, improved viability of tissue that would otherwise die,
and salvage of the tissue and patient.
In addition, twenty percent of the wounded in Iraqi experience traumatic brain injury (TBI) a
diffuse cerebral insult characterized by primary mechanical disruption of tissue and secondary
injury from ischemia, hypoxia, edema, vasospasm, neurochemicals, and reperfusion injury. A
review of the medical literature shows that there is substantial data proving a beneficial effect of
HBOT on the secondary injury processes of acute TBI. HBOT has been shown indirectly to
improve ischemia and hypoxia in acute TBI by its effect on aerobic metabolism and EEG. The
neurosurgeon authors of the Rockswold study conclude that “HBOT should be initiated as soon
as possible after acute severe traumatic brain injury.”
HBOT also has beneficial effects on vasospasm and cellular reperfusion injury. Multiple studies
have shown that HBOT reduces cerebral edema and decreases intracranial pressure (ICP). A
summary of the HBOT/cerebral edema studies in animals is that HBOT has two different effects:
one reducing brain edema (injured brain), and another producing brain edema (normal brain).
This toxic effect on normal brain causes a breakdown in the protective vasoconstriction of
arterioles, resulting in a rapid rise in brain blood flow and deterioration in EEG.
Rockswold in 1992 reported the most exhaustive, rigorous, and important study to date in acute
TBI in an attempt to refute or affirm all of the above animal and human data. Conducted from
1983 to 1989 the study enrolled 168 patients with GCS of 9 or less in a RPCT design and
stratified the patients by age and GCS. Patients were treated at 1.5 ATA/60 every 8 hours for a
maximum of two weeks immediately post TBI or until awake or deceased during these two
weeks. The average patient entered treatment 26 hours post TBI and received 21 treatments.
Overall mortality was significantly reduced 50% in the HBOT group and as high as 56% and
60% in the elevated ICP and GCS 4-6 subgroups.
This reduction in mortality has never been equaled by any therapy in the medical armamentarium
except possibly the ambulance, or in the case of the military, the helicopter. Adding HBOT to
helicopter evacuation of casualties should further decrease morbidity and mortality of injured
soldiers. This is the foundation of the DoD-BIRR Project.
References:
Harch, Paul, M.D., “FEB Scientific Background & Overview,” 2005 (81 scientific references)
Harch, Paul, M.D., “Evidence for Use of Hyperbaric Oxygen Therapy for Acute Traumatic Brain Injury,” 2001
2. Department of Defense Brain Injury Rescue & Rehabilitation Project (DoD-BIRR)
SCIENTIFIC BACKGROUND AND OVERVIEW
The Use of Hyperbaric Medicine in Acute Trauma
By
Paul G. Harch, M.D.
Clinical Assistant Professor and
Director, Hyperbaric Medicine Fellowship,
Louisiana State University School of Medicine
New Orleans, Louisiana
Hyperbaric oxygen therapy (HBOT) is the use of greater than atmospheric pressure oxygen as a
drug to treat basic disease processes and their diseases (1). In the simplest terms HBOT is a
pharmaceutical or prescription medication similar to the thousands of medications routinely
prescribed by physicians everyday throughout the world. The key differences with HBOT,
however, are that it is a drug that treats basic disease processes that are common to every disease,
that it acts as a repair drug in these processes, and that it replaces an essential element of life for
which there is no substitute, oxygen. This effectiveness in treating basic common disease
processes explains the ability of HBOT to act in a generic beneficial fashion to a multitude of
diseases, including and especially traumatic injuries to all areas of the body.
HBOT has both acute and chronic drug effects. HBOT exerts these effects by obeying the
Universal Gas Laws, the most important of which is Henry’s Law (2). Henry’s Law states that the
concentration of a gas in solution is proportional to the pressure of that gas interfacing with the
solution. For example, the amount of oxygen dissolved in a glass of water is directly proportional
to the amount of oxygen in the air. Similarly, the amount of oxygen dissolved in our blood is
directly proportional to the amount of oxygen we are breathing. According to Henry’s Law, there
is a very small amount of oxygen dissolved in the liquid portion of the blood when breathing air
(21% oxygen) at sealevel. The remainder and majority of oxygen is bound to hemoglobin in the
red blood cells giving a 98% saturation of hemoglobin. As we increase the amount of oxygen in
inspired air by applying a nasal cannula or facemask of pure oxygen the final 2% of hemoglobin is
quickly bound by oxygen. All of the remaining available oxygen interfaces with and is dissolved
in the liquid portion of the blood. Once we reach 15 liters/minute of supplemental oxygen by a
tight fitting aviator’s mask or non-rebreather mask we have reached the maximum amount of
oxygen that can be dissolved in blood by natural means. However, this is not the absolute limit.
By placing a patient in an enclosed chamber, increasing the pressure above ambient pressure, and
giving the patient pure oxygen we can cause an increase in dissolved oxygen in blood in direct
proportion to the pressure increase.
At the point of three atmospheres absolute of pure oxygen (3 ATA), just slightly more than the
amount the U.S. Navy has used for 50 years in the treatment of divers with decompression
sickness, we can dissolve enough oxygen in the plasma to render red blood cells useless. Under
these conditions as blood passes through the tiniest blood vessels tissue cells will extract all of the
dissolved oxygen in the blood without touching the oxygen bound to hemoblogin. This amount of
dissolved oxygen alone can exceed the amount necessary for the tissue to sustain life. In other
words, you don’t need red blood cells for life at 3 ATA of 100% oxygen. This physical
phenomenon was proven in a famous experiment in 1960 and published in the first edition of the
Journal of Cardiovascular Surgery by Dr. Boerema of the Netherlands (3). Dr. Boerema
DOD-BIRR HBOT Acute Trauma PG Harch 2004 anesthetized pigs, removed nearly all of their blood, and replaced it with salt water while he compressed them to 3 ATA. At 3 ATA in a hyperbaric chamber pigs with essentially no blood were completely alive and well. Dr. Boerema then removed the saline, replaced the blood, and
brought the pigs to surface where they remained alive and well. This phenomenon has been
proven effective in other experiments and is the basis for clinical use in extreme blood loss anemia
(4). The best examples are Jehovah’s Witness patients who have lost massive amounts of blood
and because of religious proscription are unable to receive blood transfusions. These patients are
kept alive over weeks with repetitive HBOT until their blood system is able to naturally produce
enough blood to sustain life. This ability to maintain life without blood has obvious potential to
battlefield casualties awaiting transfusion.
As a result of Henry’s Law HBOT is able to exert a variety of drug effects on acute
pathophysiologic processes. These have been well documented over the past 50 years and include
reduction of hypoxia (5, 6), inhibition of reperfusion injury (7), reduction of edema (8), blunting of
systemic inflammatory responses (9), and a multitude of others (10). In addition, repetitive HBOT
in wound models acts as a DNA stimulating drug to effect tissue growth (11, 12). HBOT has been
shown to interact with the DNA of cells in damaged areas to begin the production of repair
hormones, proteins, and cell surface receptors that are stimulated by the repair hormones (13, 14).
The resultant repair processes include replication of the cells responsible for tissue strength
(fibroblasts) (15), new blood vessel growth (16, 17), bone healing and strengthening (18), and new
skin growth (19).
To best understand the effectiveness and potential of HBOT one must understand basic disease
processes, commonly referred to as pathophysiologic processes. Every insult or injury to living
organisms, particularly human beings, is distinct and different, and can be characterized by the
type of force, energy, or peculiar nature of that insult. For example, a blast force is different from
a blunt force, an electrical injury, a toxic injury, a biological injury, infectious injury, thermal
injury, nuclear injury, gunshot wound, stab wound, burn, or even a surgical wound. Regardless of
the exact nature and idiosyncratic character of the injury, however, every acute injury has a
common secondary injury called the inflammatory process (20). This secondary injury in fact
causes more damage than the primary injury. Moreover, it is a universal process common to
every human being regardless of race, color, creed, size, gender, or genetics. The beauty of
hyperbaric oxygen therapy is its ability to powerfully impact the inflammatory reaction and its
component processes like no other drug in the history of medicine.
The inflammatory process begins with tissue injury. The injury can be as innocuous as
apposition of tissues that normally do not interface against one another, such as spinal bony
compression of a nerve root due to a degenerative disk. Most often, however, tissue injury results
from much larger forces such as the type seen in military conflict. Once tissue is disrupted
proteins, fat, other molecules, and disrupted tissue is exposed to the circulation. In addition,
blood vessels are damaged both directly by mechanical forces and indirectly by tissue fragments
that interact with the vessel walls. The net effect is bleeding from broken blood vessels and
dilation of the unbroken blood vessels. As the vessels dilate, blood pressure forces the liquid
portion of the blood out of the vessels. The extravasated fluid, now referred to as edema, exerts
its own pressure that collapses blood vessels, leading to a reduction of blood flow. This
compounds the reduction in blood flow already caused by disrupted blood vessels and bleeding.
In addition, white blood cells in the circulation are attracted to the damaged tissue by molecules
DOD-BIRR HBOT Acute Trauma PG Harch 2004 2 released from the damaged tissue. The white blood cells traverse the blood vessel walls in a process called emigration (21) and disgorge themselves of their digestive enzymes. These enzymes cause further tissue damage in an attempt to clean up the primary damage, but also
cause constriction of blood vessels to limit further bleeding and leakage of fluid.
The cumulative effect of all of these processes, including tissue injury, fluid leakage, blood vessel
disruption, bleeding, white blood cell accumulation, indiscriminate release of digestive enzymes,
and blood vessel constriction is a reduction in blood flow and most importantly, reduction in the
crucial element for sustenance of life, oxygen. With the reduction of oxygen, blood vessel walls
become activated as do the white blood cell surface proteins. Activation of the white blood cell
surface proteins results in their prominence from the cell surface in a manner similar to a sail
rising on a sailboat. This drag slows down the white blood cells, resulting in their margination
(22) to the walls of blood vessels in an area of injury. The white blood cells then stick to the walls
of the blood vessels and generate tiny blood clots. This cascade of events is known as reperfusion
injury (23). The white blood cells now emigrate and compound the process described above,
resulting in greater reduction in blood flow and hypoxia. Thus, low oxygen leads to further tissue
damage, leakage of blood vessels, clotting of blood vessels, and more hypoxia, in essence, the
“vicious cycle” described by Holbach (24). This is the sequence of events at the site of every
bullet, shrapnel, blast, blunt, electrical, etc. impact in every soldier injured in battle. Finally, if
there is enough bleeding, clotting of blood vessels, and blood vessel leakage of fluid in the body to
drop blood pressure the entire body becomes activated by hypoxia, undergoes reperfusion injury,
and the soldier experiences shock, a critical point of no return for most human beings.
In the past 12 years scientific research has unequivocally shown that the only drug to completely
or nearly completely reverse the reperfusion injury process is hyperbaric oxygen. In multiple
experiments with different animal models, different organ systems, different types of blood flow
reduction or absence (e.g., heart attack, stroke, cardiac arrest, carbon monoxide, tourniqueting of
an extremity, etc.) timely HBOT within hours of reperfusion injury has been shown to completely
or nearly completely reverse reperfusion injury (25). The mechanism of action has been partly
elucidated and shown to be an effect on the white blood cell surface proteins and the inside lining
of the blood vessels to which the white blood cells stick (26, 27). The net result is a reduction in
clotting, blood vessel leakage, and an increase in oxygenation. In addition, HBOT has been shown
to constrict blood vessels (28), thus reducing bleeding and leakage of fluid that causes swelling
and further compression of blood vessels. This breaks the vicious cycle described above.
Simultaneously, due to its ability to dissolve large amounts of oxygen in the liquid portion of the
blood, oxygen enriched plasma is able to reach damaged areas of tissue not accessible by normal
blood flow and restore oxidative function to these areas. The net result is a dramatic reduction in
the secondary injury process, improved viability of tissue that would otherwise die, and salvage of
the tissue and patient.
The goal of the DoD-BIRR Battle Project is to use timely hyperbaric oxygen therapy to
hyperacutely interrupt the inflammatory reaction and its injurious cascade, reverse hypoxia that
results from disruption of blood vessels and bleeding, restore and prolong tissue viability, and
prevent the secondary injury processes that are so devastating. HBOT is uniquely suited to
battlefield casualties for its beneficial effects on five processes or conditions: acute severe
traumatic brain injury (TBI), extremity wounds with crush injury and compartment syndrome,
burns, acute hemorrhage, and reperfusion injury.
DOD-BIRR HBOT Acute Trauma PG Harch 2004 3
The literature for HBOT in acute severe TBI is amongst the strongest in hyperbaric medicine.
HBOT effects on brain injury pathophysiology have been well-documented (29-37). In humans
Holbach (38) demonstrated improved glucose metabolism in acute severe TBI patients with one
HBOT. He followed this study with a controlled trial of HBOT in TBI patients with the acute
mid-brain syndrome (24). Using 1-7 HBOT’s, he demonstrated an overall 55% reduction in
mortality and 81% improvement in short-term outcome (10d post TBI). These dramatic findings
were duplicated in the largest study performed to date, the Rockswold study in 1992 (39).
Rockswold showed that HBOT induced a 47% reduction in mortality overall and a 59% reduction
for the most severely injured, nearly identical to Holbach. Rockswold followed his study with two
additional studies that reinforced their and Holbach’s findings. The first one in 2001 (40), showed
that a single HBOT improved brain metabolism (similar to Holbach-38) and re-coupled brain
blood flow and metabolism in severely injured human brain FOR THE FIRST TIME IN THE
HISTORY OF SCIENCE AND MEDICINE.
This was a profound discovery and was consistent with all of the previous animal and human
experimentation performed with HBOT in acute TBI. The second study, an animal study (41),
proved that HBOT could increase oxygen consumption, brain tissue oxygen levels, and
mitochondrial function (the organelle that is the energy center for every cell in the body).
Additional randomized controlled studies by Artru (80) and Ren (81) at somewhat higher
pressures have shown the same result as Rockswold and Holbach. Taken collectively the
multitude of animal and human studies strongly argue that HBOT delivered within hours to days
of acute severe TBI unequivocally reduces mortality and improves outcome. The reduction in
mortality has never been equaled by any therapy in the medical armamentarium except possibly
the ambulance, or in the case of the military, the helicopter. Adding HBOT to helicopter
evacuation of casualties should further decrease morbidity and mortality of injured soldiers. This
is the foundation of the DOD-BIRR Project.
The second important impact of HBOT in acute battlefield trauma is the effect on extremity
injuries which include crush injury, major blood vessel disruption, and compartment syndrome.
Extremity gunshot, blast, and other high force military injuries cause massive tissue destruction,
hypoxia, and swelling. This swelling leads to what is called compartment syndrome where the
various muscle compartments that are bound by their dividing tissues (fascia and bone) increase in
pressure and occlude blood vessels. The subsequent lack of blood flow causes more hypoxia
leading to the “vicious cycle” described above in traumatic brain injury. A vicious cycle in the
extremities results in death of the tissue, loss of function, and often loss of limb. This sequence of
events is often complicated and worsened by disruption of major blood vessels that further lowers
oxygen levels. Multiple animal studies have demonstrated a benefit of HBOT in crush injury, lack
of blood flow, and compartment syndrome (42-47).
A human study in 1987 (48) reinforced these results by showing limb salvage in traumatized
extremities with low blood flow who were at risk for amputation after failed surgical therapy.
Stronger studies in 1989 (49) and 1996 (50) duplicated the previous animal and human data. In
particular the study by Bouachour (50) in open fractures and crush injuries demonstrated
significantly improved complete healing and bone healing with a reduction in additional surgical
procedures. Actual application to extremity war injuries has been reported by three separate
DOD-BIRR HBOT Acute Trauma PG Harch 2004
4 authors with good results (51, 52, 53). Most of these studies, especially the war studies, involved damage to major blood vessels with its accompanying loss of blood flow and oxygen until surgical repair was complete. Despite this arterial damage, the net result in most of the studies is a
reduction in major amputations. Very likely HBOT ameliorates compartment syndrome by
reducing edema and reversing hypoxia. Its most profound effect, however, maybe on prevention
of compartment syndrome by impacting reperfusion injury. Reperfusion injury is a normal feature
of direct tissue injury, but it can be compounded by the secondary reperfusion injury from
tourniqueting a massively bleeding extremity. HBOT delivered within the first few hours of injury
could significantly inhibit reperfusion injury (7, 25, 26) and prevent the major delayed
complications of R.I.: infection, compartment syndrome, and amputation. In addition, HBOT
could prevent the reperfusion injury that occurs during surgical repair of the injured extremity as
the extremity is tourniqueted during surgery to allow blood vessel reconstruction and bone repair.
HBOT has shown benefit in acute thermal burns since 1965 when Wada discovered that burned
patients treated for carbon monoxide poisoning from a coal mine fire experienced accelerated
healing of their burns (54). Since that time a plethora of studies in animals has shown improved
healing (55), reversal of hypoxia (56), reduction of inflammation/reperfusion injury (57, 58), burn
edema (59, 60, 61, 62), increased rate of skin growth (63), improvement in the blood vessels (63,
64, 65), prevention of progression of deep second degree burns to third degree burns (62, 65, 66,
67), reduction in burn shock (68)and a decrease in infections (55). Studies in humans have
mirrored the animal literature with clear or likely benefit in 19 of 21 studies (69), demonstrating a
drastic reduction in healing time for deep second degree burns (70-73). The effect on third degree
burns (all layers of the skin) is less apparent since modern burn care has evolved to early surgical
removal of burned tissue. Immediate HBOT in these cases, however, could likely minimize the
amount of questionable second degree burned tissue that would be inadvertently excised with the
third degree burn. This could be important in burns of the face, ears, hands and feet where tissue
preservation is critical. Lastly, early intervention with HBOT has reduced the cost of burn
treatment (73). Hyperacute HBOT at a battlefield MASH station should duplicate the civilian
experience and have a dramatic impact on the treatment of burned soldiers.
The fourth significant impact of HBOT on military casualties would be in the treatment of
massive hemorrhage. As mentioned above in the example of Jehovah’s Witness patients
HBOT can be used as a blood substitute until definitive treatment is available (74). A large
volume of animal and human studies consistently show better survival with HBOT (75) in
profound hemorrhage. Relying on Henry’s Law and Boerema’s experiment, massive amounts
of oxygen would be delivered to exsanguinating soldiers by its dissolution in the soldier’s
plasma. In the 1960’s major hospitals in the United States and Europe utilized Henry’s law to
hyperoxygenate babies with congenital heart disease undergoing cardiac surgery. In the
absence of the soon to be invented heart-lung bypass machine the dissolved oxygen provided
surgeons longer operating times during cardiac standstill. In a MASH unit soldiers could be
rapidly compressed to 3 ATA on 100% oxygen in hyperbaric chambers while awaiting or in
the process of receiving blood transfusions. Using air breaks between oxygen administration
periods they can remain at this pressure for 3-4 hours, 3-4 times per day (75). The reduction
of time in the shock state would pay dividends in decreased morbidity and mortality. In
addition, in times of mass casualties that overwhelm the blood supply and surgical
capabilities, HBOT could be delivered until blood is available or while the soldier is in flight
to another MASH. Alternatively, critical soldiers with massive ongoing bleeding could be
DOD-BIRR HBOT Acute Trauma PG Harch 2004
5 placed in a hyperbaric operating room and receive the benefits of life without blood while
time is bought for surgical control of bleeding and blood transfusions. The natural extension
of this application is to those soldiers who have cardiac arrest from massive hemorrhage.
Should this event occur even minutes before or after arrival at the MASH unit soldiers could
be compressed on oxygen while IV’s are placed, volume and blood are infused, and bleeding
is controlled. The precedent has been set for this in resuscitation from cardiac arrest in a
drowned diver with decompression sickness 22 minutes after loss of consciousness (76) and
guinea pigs 15 minutes (77) and swine 25 minutes post induced cardiac arrest (78). While the
human case was a partial exsangination and the animals had normal blood volume they
suggest an untapped potential for application to soldiers. The time has come to introduce to
the military medical therapeutics arsenal both this potential and the more certain application to
near-exsanguinated soldiers or soldiers in shock.
The fifth area of impact for HBOT in acute military casualty treatment is reperfusion injury. As
mentioned above, reperfusion injury is a ubiquitous process post injury. Specifically, it is a
secondary injury that occurs upon restoration of blood flow (23). In the case of battlefield
injuries it occurs with any blunt, blast, bullet, shrapnel, stab, electrical, burn, or other wound. In
addition, it causes tissue destruction post resuscitation from shock, upon release of any tourniquet
placed to control bleeding in the field or in the operating room, and upon restoration of blood
flow to re-attached limbs. HBOT’s effect on reperfusion injury has been argued to be a generic
drug that applies regardless of the affected organ system or species (25). It appears to also be a
dominant mechanism in the prevention of brain lipid peroxidation in the swine resuscitation
experiments above (79). When delivered in timely fashion after injury it protects the body from
further reperfusion injury should the soldier have to undergo surgery or have other complications.
Coupled with the known effects on bone healing and the ability to salvage marginally viable
tissue HBOT has the potential to significantly reduce major amputations. Overall, HBOT’s effect
on reperfusion injury could be huge in military casualty management.
In conclusion, HBOT is one of the most powerful drugs known to man. Simultaneously, HBOT
delivers the substrate of life, oxygen, for which there is no substitute. HBOT has profound
beneficial effects on injury pathophysiologic processes that are common in military casualties.
Moreover, it has been shown to positively impact traumatic brain injury, compartment syndrome,
burns, hemorrhage, and reperfusion injury. These injuries and injury processes comprise the bulk
of battlefield casualties. With timely intervention of HBOT the morbidity and mortality of
injured soldiers should substantially improve as they have in their civilian counterparts. Past
foreign military experience strongly suggests this benefit in extremity wounds and its our
conviction that United States soldiers deserve nothing less. This is the goal of the DoD-BIRR
Project.
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DOD-BIRR HBOT Acute Trauma PG Harch 2004 10
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DOD-BIRR HBOT Acute Trauma PG Harch 2004 11
EVIDENCE FOR USE OF HYPERBARIC OXYGEN THERAPY FOR ACUTE TRAUMATIC BRAIN INJURY
Traumatic brain injury (TBI) affects over 1.6 million United States residents annually and a
far greater number internationally (Ghajar). Over 50,000 of these individuals will die from their brain
injury and greater than 80,000 will have permanent severe neurological disability (Ghajar). Since the
development of modern emergency medical system (EMS) management of acute trauma no
therapeutic modality has further reduced the mortality of traumatic brain injury. The data below will
show that the only modality in the history of science and medicine with a scientifically proven
reduction in mortality in acute severe traumatic brain injury is timely low-pressure hyperbaric oxygen
therapy (HBOT). Some of this data also suggests a benefit for functional improvement.
Any discussion of the effect of HBOT on a medical condition should be based on the concept
of drug dosage. A comprehensive definition of HBOT as a drug is necessary: HBOT is the use of
greater than ambient atmospheric pressure oxygen as a drug to treat basic pathophysiologic
processes/states and their diseases (Harch, Jain). The dose of HBOT is a function of the fractional
percentage of oxygen, rapidity of pressurization and depressurization, depth of pressurization, length
of time at depth, frequency of treatments, presence or absence and duration of air breaks and surface
intervals, number of treatments, and time of intervention in the natural history of the disease, which
identifies the pathological targets. The data in this paper will be discussed and evaluated in terms of
dosing and will emphasize the absolute pressure, time at depth, frequency and number of treatments,
and time of intervention. The medical literature will be reviewed to first answer the question of
efficacy of HBOT on the underlying pathology, pathophysiology, and outcomes of acute TBI in
animals and second to see if this efficacy is duplicated and reinforced by the human clinical literature.
TBI is a diffuse cerebral insult characterized by primary mechanical disruption of tissue
(Peerless), (Strich), (Adams) and secondary injury from ischemia (Bouma), hypoxia(Adams), (van
den Brink), (Zhi), edema (Adams), (Schoettle), (Bullock), vasospasm (Martin), (Zurynski),
neurochemicals (McIntosh), (Hovda),and reperfusion injury (Zhuang), (Schoettle). A review of the
medical literature shows that there is substantial data proving a beneficial effect of HBOT on the
secondary injury processes of acute TBI. HBOT has been shown indirectly to improve ischemia and
hypoxia in acute TBI by its effect on aerobic metabolism and EEG. Contreras (ref) recorded a
persistent increased cerebral glucose utilization in 5 of 21 areas of brain remote from a cryogenic
injury 24 hours after the fourth HBOT. Treatments began 30 minutes after the injury and continued
daily at 2 ATA/90 minutes. Holbach (J. Neurol) obtained a similar result in humans with acute severe
TBI (23 patients), and stroke (7 patients) a few days post injury/ictus. Measuring the glucose
oxidation quotient, he found aerobic metabolism to be maximal in injured brain at 1.5 ATA. A single
10-15 minute excursion to 2.0 ATA had a toxic effect on glucose uptake and metabolism that
persisted after return to room air. Holbach (6th Int. Congress) reinforced this finding by
demonstrating simultaneously improved EEG and decreased regional cortical blood flow (rCBF) in a
similar or the same group of acute severe TBI patients at 1.5 ATA. Upon presure increase to 2.0 or
2.5 ATA for 30 minutes EEG markedly deteriorated and rCBF increased significantly. Some patients
experienced persistence of these toxic effects upon return to room air.
HBOT also has beneficial effects on vasospasm. Yufu showed that 30 minutes after subarachnoid hemorrhage a single HBOT at 2.0 ATA/60 minutes reversed reductions in Na+, K+-
ATPase activity and cell membrane alterations. Similarly, Kohshi documented a clinical benefit of
Evidence for use of Hyperbaric Oxygen Therapy for Acute Traumatic Brain injury – Harch
HBOT on vasospasm in a controlled human study. He found that HBOT at 2.5 ATA/60 once
or twice/day (average 10 treatments) soon after symptomatic vasospasm in post-op SAH/aneurysm
patients decreased strokes and improved neurological outcome and EEG over controls.
Multiple studies have shown that HBOT reduces cerebral edema and decreases ICP. Coe
used a single 3.0 ATA/120 HBOT immediately after cryogenic brain injury in rats to improve
neuronal destruction, cerebral edema, and length of survival from 2 hours to 12.5 hours. Coe
reinforced these results with a follow-up percussion brain injury experiment. He showed that a
single 3.0 ATA/60 HBOT with 2% carbogen immediately after injury resulted in a significant
improvement in maze running ability over controls at seven days that was nearly equal to non-injured
animals. Sukoff (1968), using cerebral implantation of psyllium seeds in dogs, delivered HBOT
beginning 24 hours after surgery at 3.0 ATA/ 45 (total dive time?) three times/day tapering to once or
twice/day, and found a reduction in cerebral edema and cisternal fluid pressures and an increase in
survival. In another model of cryogenic injury Miller, Ledingham, and Jennett showed that a single
HBOT at 2.0 ATA/15-30, beginning minutes after injury, reduced ICP, but at 40-60 minutes the
reduction in ICP began to reverse and rebounded (in some dogs) above baseline on return to air
breathing. With the same model Miller and Ledingham later showed that HBOT at 2.0 ATA/4 hours,
beginning one hour after injury, caused an initial reduction in ICP that progressively reversed and
then significantly rebounded post HBOT. Simultaneously, CSF lactate increased to the levels of
controls, contrary to Holbach’s experiment above. A third experiment by this group in the same
model confirmed the benefit of short exposures of HBOT at 2.0 ATA. Dogs subjected to 2.0 ATA/15
had a 33% reduction in ICP and an improvement in perfusion pressure while dogs at 3.0 ATA/15 had
a reversal of ICP reduction and rebound after return to surface, indicating a toxic effect of this
pressure. Kanshepolsky subjected cats to cryogenic brain injury and treated with HBOT at 2.5
ATA/90 three times/day for upto three days, beginning either two or 6 hours after injury. HBOT
increased survival and decreased brain edema if begun two hours after injury, but had no significant
effect if treatment was delayed to six hours. A summary of the HBOT/cerebral edema studies in
animals is that HBOT has two different effects (Hayakawa): one reducing brain edema (injured
brain), and another producing brain edema (normal brain). This toxic effect on normal brain causes a
breakdown in the protective vasoconstriction of arterioles, resulting in a rapid rise in brain blood flow
and deterioration in EEG (Holbach). If not reversed seizures follow (Bean), (Chavko). It appears that
high pressures (greater than or equal to 2.0 ATA) maybe beneficial for very short periods of time (15-
30 minutes) if delivered within a few hours after acute brain trauma. A similar conclusion has been
reached in global ischemia/anoxia/coma (Harch, Jain). These pressures, however, have a toxic effect
if used for greater duration and beyond the 2-3 hour post injury period. During this later period 1.5
ATA/30 minutes appears to be the optimal pressure/duration (human data).
HBOT also has beneficial effects on cellular reperfusion injury. Both Zamboni and Thom
have reported inhibition of white blood cell mediated reperfusion injury at 2.0 and from 2.0 to 2.8
ATA, respectively, when HBOT is initiated within approximately one hour after brain insult. This is
consistent with the data above on high pressure HBOT in cerebral edema immediately after brain
injury. Unfortunately, this may not be applicable to human TBI and its associated reperfusion injury
since time to initiation of HBOT is often many hours after injury.
The non-controlled human data is equally positive and consistent with the animal data.
Mogami, in 66 acute coma cases, 50 of which were severe TBI, reported neurological improvement in
50% and EEG improvement in 33% of cases with a decrease in CSF pressure, occurring mostly at
depth, that regressed or rebounded post treatment. The patients also exhibited a slight improvement
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Evidence for use of Hyperbaric Oxygen Therapy for Acute Traumatic Brain injury – Harch
in cerebral aerobic metabolism with a slight decrease in the lactate/pyruvate ratio. The best responses
were in the least injured patients. Treatment pressures were 2 ATA/60 minutes, once or twice/day
with an average of two treatments. The preponderance of benefit at depth with regression/rebound
post treatment suggests an excessive pressure of oxygen as reviewed above in the cerebral edema
animal studies. Hayakawa achieved similar results in 9 acute TBI and 4 post-op brain tumor patients
at 2ATA/60 minutes, measuring CSFP. He found three patterns of response, the most common of
which was a reduction of CSFP at the beginning and a rise at the end of HBOT. He proposed the
edema reducing effect of HBOT on injured brain and edema producing effect on normal brain
mentioned above. Both of these studies are reinforced by the two companion studies of Holbach on
EEG and rCBF above in 14 acute severe TBI patients exposed to different pressure profiles.. This
data is strongly supported by Holbach’s additional report in 1977 on metabolic data in the same or a
similar group of severe acute TBI (n=23) and CVA (n=7) patients, also noted above. This metabolic
data is further supported by Holbach’s 1974 report on crude outcomes of 102 patients, 43 with “lifethreatening” acute TBI, who were treated with an average 2.6 HBOT’s within a few days of injury: 52
at 2-3 ATA and 50 at 1.5 ATA. The TBI subset treated at 1.5 ATA demonstrated a 33% increase in
the number of markedly improved patients. Additionally, Lareng published two cases of deepening
coma secondary to TBI who were treated 4 and 10 days post TBI at 2.0 ATA/45 bid for 42
treatments. One patient was completely well with a normal EEG and the other had complete
neurological recovery. Belokurov treated 23 acute pediatric coma cases, 13 of which were traumatic,
at 1.7-2.0 ATA/60, once/day for four days. He found: a 50% reduction in time of coma if HBOT
was initiated within the first 24 hours after injury (indicating HBOT responsive pathology in this
period of time), a statistically significant improvement in coma score after the first HBOT, especially
in the TBI patients, and further improvement in eight of ten patients who were retreated with HBOT
after relapse into vegetative coma. In contrast, Artru measured CBF and metabolism in 6 severe
acute TBI patients 5-47 days post injury with 2.2 or 2.5 ATA/90 minute HBOT exposures and found
variable responses due to differential effects of HBOT on injured and normal brain. Curiously,
systemic arterial PO2 declined in 8 of 9 measurement trials, indicating a pulmonary or severe
brainstem toxicity/complication with this profile.
All of the above human studies were performed on severe acute TBI patients a few days post
injury. The data is remarkably consistently positive, but the exact dose of oxygen is less clear. In
general, the data suggests that approximately 48 hours or more after injury pressures from 1.5 to 2.0
ATA and treatment times less than or equal to one hour have reproducible beneficial effects and that
pressures above 2.0 ATA have negative effects on CBF, EEG, CSFP, and aerobic metabolism.
Specifically, higher pressures seem to reverse the brain’s protective vasoconstrictive capacity leading
to a marked increase in CBF/CSFP and simultaneous deterioration in EEG/aerobic metabolism.
Moreover, there may be competing effects in injured and normal brain that determine whether the
final result is positive or negative based on the relative proportions and possibly locations of the two
types of tissue. Unfortunately, due to small numbers of patients and inadequate data this complex
relationship cannot be adequately defined for all of the different levels of injury at different times of
intervention.
The more rigorously controlled human clinical studies recapitulate all of the above
data/conclusions and lead to more powerful conclusions. Holbach followed his 1971 study with a
randomized prospective controlled study of HBOT vs. standard intensive care in 99 acute TBI coma
(mid-brain syndrome) patients, 2-10 days post injury. The HBOT patients received 1-7 treatments at
1.5 ATA/45 minutes. The HBOT group achieved a 21% decrease in mortality and the apallic state
(vegetative coma) and a 450% increase in complete recovery. Artru published a similar RPCT on 60
3 Copyright Paul G. Harch, M.D., June, 2001
Evidence for use of Hyperbaric Oxygen Therapy for Acute Traumatic Brain injury – Harch
acute coma TBI patients 4.5 days post injury. HBOT patients were delivered 2.5 ATA/90 minute
treatments once/day on a 10 day schedule with a four day break and then repeat of the cycle until
consciousness or death. Despite multiple breaks in protocol, delays to treatment, and use of the a
high pressure, one of 9 subgroups, the brainstem contusion group, experienced a significantly higher
rate of recovery of consciousness at one month. Lastly, and most importantly, Rockswold in 1992
reported the most exhaustive, rigorous, and important study to date in acute TBI in an attempt to
refute or affirm all of the above animal and human data. Conducted from 1983 to 1989 the study
enrolled 168 patients with GCS of 9 or less in a RPCT design and stratified the patients by age and
GCS. Patients were treated at 1.5 ATA/60 every 8 hours for a maximum of two weeks immediately
post TBI or until awake or deceased during these two weeks. The average patient entered treatment
26 hours post TBI and received 21 treatments. Overall mortality was significantly reduced 50% in
the HBOT group and as high as 56% and 60% in the elevated ICP and GCS 4-6 subgroups,
respectively, however there was no difference in the good outcome categories between the groups at
12 months.
A summarization of the above data demonstrates an undeniable beneficial effect of HBOT on
mortality and recovery of consciousness and a suggestion of improved neurological outcome. The
best results were achieved at pressures less than 2.0 ATA, specifically 1.5 ATA. Unfortunately, there
is not a large amount of data generated from finely adjusted dose escalations of HBOT, but rather a
preponderance of studies performed at 1.5 ATA based on early dose escalation studies, with some
comparison data at 2.0 ATA and higher. These conclusions are derived from a number of RPCT’s
that en block constitutes one of the most powerful and consistent bodies of scientific evidence for any
accepted indication for HBOT. The TBI controlled trials alone already exceed the data for at least six
of the thirteen indications, including the last addition, cerebral abscess. While internally consistent
and stand alone sufficient this body of data was recently strengthened by the addition of the follow up
article of the Rockswold group in March, 2001.
On a group of severe TBI patients similar to those in the 1992 study the authors methodically
and meticulously studied brain metabolism at 1.5 ATA, once/day for 5-7 days post injury. They
found that HBOT improved the cerebral metabolic rate for oxygen and decreased CSF lactate ,
especially in those with reduced CBF or with ischemia, normalized the coupling of CBF and cerebral
metabolism, exerted a persistent effect on CBF and metabolism, and reduced elevated levels of ICP
and CBF. Notably, HBOT’s recoupling of flow and metabolism is the only demonstration of such in
the history of science. They recommended that shorter (30 minutes) more frequent (every 8 hours—
identical to their first study) treatments would optimize treatment.
This final study reaffirms the multiple studies above at both lower and higher pressures that
show reversal or deterioration of a beneficial HBOT effect after 30+ minutes in the chamber. The data
and scientific argument is strong and supports/demands low pressure HBOT in acute severe traumatic
brain injury. Some of the studies suggest that even a few treatments can have a profound effect. The
protocol is uncertain beyond the first two weeks, but should probably be delivered according to the
principle employed in medicine for any therapeutic modality: treat until clinical plateau. While the
data is not so consistent on long-term neurological outcome, this goal should be left to further
research and multi-modality therapy. After all, the first priority in life-threatening illness is to save
the patient.
As a matter of perspective, the American Heart Association has spent hundreds of millions if
not billions of dollars on CPR education, training, and research, yet has still have made very little
4 Copyright Paul G. Harch, M.D., June, 2001
Evidence for use of Hyperbaric Oxygen Therapy for Acute Traumatic Brain injury – Harch
progress in successful resuscitation of cardiac arrest. Very few survive and almost all who survive
are severely neurologically impaired. Despite these dismal results the research largesse continues in
an effort to find even the smallest improvement in mortality. At our fingertips is possibly the
therapeutic modality with the greatest and most dramatic effect on reduction of acute TBI mortality in
the history of medicine. The neurosurgeon authors of the Rockswold study conclude that “HBOT
should be initiated as soon as possible after acute severe traumatic brain injury.” I believe the UHMS
and medical profession should follow their lead and the UHMS list acute TBI as an accepted
indication for HBOT. I am ready, willing, and eager to defend this position. Thank you for the
opportunity.
Sincerely,
Paul G. Harch, M.D.
Clinical Assistant Professor
Department of Medicine
LSU School of Medicine
New Orleans, Louisiana
ADDENDUM TO:
EVIDENCE FOR USE OF
HYPERBARIC OXYGEN THERAPY
FOR ACUTE TRAUMATIC BRAIN INJURY
Paul G. Harch, M.D.
June 13, 2001
The evidence for use of hyperbaric oxygen therapy for acute traumatic brain injury is based on a
general review of the scientific animal and human data. While this body of consistent studies constitutes stand
alone proof of the efficacy of HBOT in acute TBI, scoring of efficacy using the Gottlieb and American Heart
Association schemes strengthens the argument. The scoring results are tabulated below, acknowledging that
some of the studies are difficult to classify by the Gottlieb system:
A. Gottlieb system: Assigned Points - Known etiology (known to be or logically can be expected to be positively 4 out of 4 (4/4)
Affected by HBO). (Bouma, Adams, van den Brink, Zhi, Adams, Schoettle,
Bullock, Martin, Zurynski, Zhuang studies). - Pathophysiology (irrespective of whether specific etiology is known) 5/5
demonstrated to be amenable to HBOT. [Contreras, Holbach (J. of Neurol,
6th Int Congress—two studies), Yufu, Kohshi, Coe, Sukoff, Miller (three studies),
Kanshepolsky, Hayakawa, Zamboni, Thom]. - Natural History of disease known to be “downhill.” (Ghajar). 7/7
- In vitro data. (None). 0/6
- Animal experimentation (one or more species). (Contreras, Yufu, Coe, Sukoff, 8/8
Miller, Kanshepolsky, Zamboni, Thom). - Human data: anecdotal (Lareng paper). 1/5
5 Copyright Paul G. Harch, M.D., June, 2001
Evidence for use of Hyperbaric Oxygen Therapy for Acute Traumatic Brain injury – Harch - Human data: patient controlled study(ies). Hayakawa, Mogami, and Sukoff studies). 7/7
- Human data: longitudinal study(ies). (Belokurov, Holbach-5th and 6th Int. 7/8
Congresses). - Human data: double blind (with or without crossover) study(ies). (Holbach, 10/10
S. Rockswold). - Human data: double blind [comparative therapeutic study(ies), “head-to-head” 10/10
comparison with currently accepted therapeutic agents]. (Artru, Holbach,
G. Rockswold). _
TOTAL: 59/70
Minimum of 35 points is necessary for inclusion. The total of 59 easily surpasses this requirement.
B. American Heart Association
Class I: Definitely recommended. One or more Level 1 studies are present, study results are consistently
positive and compelling. Artru, Holbach, and Rockswold studies. Supported by additional Rockswold and
Holbach metabolic studies. The lowest level of grading would be a Class IIa if one questions effectiveness,
however Class IIa studies have Level 1 studies that are absent, inconsistent, or lack power. This is not the
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