Portable Hyperbaric Chambers and Emergency War Surgery - by Edward A. Betts

Introduction
There are 7 categories of injuries for which a hyperbaric chamber would have benefit in the military theater. They are: missile type (bullets and fragmentation) injuries, blast injuries, burn injuries, chemical injuries, radiation injuries, infection and post surgical recovery.

Missile-type Injuries
When bullets and fragmentation enter the body, surgeons debride (surgically remove) non.viable, damaged tissue. This is done so that tissue (usually muscle) that has been damaged to the point that it cannot survive is not left behind to cause an inevitable infection. The difficulty is in knowing exactly which tissue will and will not survive. While there are guidelines taught to surgeons to help them distinguish viable from non.viable tissue it is not an exact science. If the surgeon removes more tissue than is necessary, then the patient will end up with unnecessary disfigurement and dysfunction. If on the other hand, tissue is left behind that does not survive, infection is the result.

“Since blood flow in the muscle around the projectile path is changing it is difficult at best for the surgeon, at any point in time, using any set of guidelines, to be certain of excising only (but all of) the non-viable muscle, and not viable muscle. Writings in the past two decades have demanded this judgment of our young surgeons when even the most experienced combat surgeon was not always certain. This was demonstrated in the Vietnam conflict when some wounds, which were treated in accordance with the conventional “4 c” guidelines (color, contraction, consistency and circulation) were noted on arrival at another hospital, a few days later, to have obviously necrotic muscle. Some surgeons at this higher echelon of care concluded that the initial debridement had been done improperly. The 5th CINCPAC War Surgery Conference in 1971 corrected that misconception by stating that the later appearance of necrotic tissue in a wound does not necessarily mean that the original debridement was improperly done, but rather was the result of transient dynamics of wound physiology at the time of the original debridement.”

Whether a damaged piece of tissue survives is primarily dependent on its oxygen level. Thus, putting patients into a hyperbaric chamber after their initial surgery can both decrease the risk of borderline tissue from becoming necrotic as well as decrease the amount of tissue that must be initially removed.

Blast Injuries
While blast type injuries have always been a part of warfare, they are becoming more so in current asymmetrical scenarios. While body armor can prevent many lethal injuries from bullets, the Iraqi conflict has demonstrated the effectiveness of improvised-explosive-devices (IEDs). We can expect more of this type of engagement in the future as the military engages in more police actions, guerilla warfare and in dealing with insurgents around the world.

In addition to missile type wounds from fragmentation and burns, blast injuries from IEDs can also cause air embolism from lung punctures and blowouts. “Air emboli from a severe blast may be lethal within minutes....... If seen early enough, prompt use of a recompression chamber may be lifesaving. Hyperbaric therapy works both by physically reducing the size of the bubbles and by speeding their absorption.”

Furthermore, damage to the lungs from the blast and/or the inhalation of toxic gases from the explosion make hyperbaric therapy additionally useful by hyper.oxygenating the blood thus allowing oxygen to be delivered to the body even when the lungs are compromised. Carbon monoxide toxicity can also be alleviated through the use of HBOT.

Burn Injuries
Hyperbaric oxygen reduces swelling, limits progression of the burn injury (which continues 3.4 days after the initial injury) and may diminish lung damage from inhalation of heat and smoke. A large body of data supports the efficacy of hyperbaric oxygen therapy (HBOT) in the treatment of thermal burns, but the role of HBOT in the treatment of general burn injury remains a subject of controversy. The aim of the Croatia study was to evaluate possible positive effects of HBOT on the experimental burn wound healing. Deep second degree burns were produced on the depiliated backs of 70 male Wistar rats using a validated burn protocol. The animals were assigned randomly to one of two groups: 35 to the control group, which was treated with silver sulphadiazine and placebo gas, and 35 to the experimental group, which was treated with silver sulphadiazine and HBOT. The main outcome measure was wound healing, characterized by formation of post.burn edema, neoangiogenesis, number of regeneratory active follicles, necrosis staging, margination of leukocytes, and time of epithelization.

A significant reduction of the post.burn edema after treatment with HBOT (p = 0.009) was found. HBOT had a beneficial effect on neoangiogenesis (p = 0.009). The number of preserved regeneratory active follicles was significantly higher (p = 0.009) and epithelial regeneration was more rapid in the experimental group (p = 0.048). There were no significant differences for margination of leukocytes (p = 0.55) or necrosis staging (p = 1.00). These data further support earlier conclusions that HBOT is beneficial in the healing of burn wounds.

Chemical Injuries
Chemicals used in warfare range from toxic gases and nerve agents to white phosphorous. Some chemicals work by disabling the lungs, others by burning tissues. For such agents, hyperbaric oxygen therapy is indicated to allow for maximum delivery of oxygen to the tissue and accelerate repair of damaged systems.

Radiation
HBOT is currently used in hospitals to help patients recover from radiation damage due to cancer therapy. In a similar way, people exposed to nuclear radiation would also be greatly helped by hyperbaric oxygen therapy.

Infection
While deaths by infection are rare now in the military theater due to the broad use of new antibiotics, this was not always the case. Wars earlier in the 20th century showed a high rate of amputations and mortality due not to the trauma of the injury but to the inevitable infections that followed. Should some of the antibiotic resistant strains currently in US prisons and hospitals, or a weaponized infection make their way to the military theater, we may see a return to these earlier times when infections caused much more mortality and morbidity. HBOT is both directly bacteriostatic as well as protective against infections spreading.

"The frequent contamination of war wounds with clostridia is due to the ubiquitous nature of this organism. A high oxygen tension in the surrounding healthy tissues prevents invasions in these areas."

Post-surgical Recovery
In addition to the above mentioned applications, hyperbaric therapy is beneficial for post- surgical recovery due to its abilities to accelerate all wound repair, minimize infection and stimulate new blood vessel growth. Furthermore it is indicated in treating complications such as non.healing wounds, osteonecrosis and nerve damage.

Summary
There is little disagreement amongst physicians that nearly any trauma which may compromise circulation (and thus Oxygen delivery to the cells) will benefit by even small increases in Oxygen delivery. With the advent of lightweight, inexpensive and sturdy portable hyperbaric chambers, this technology, and the benefits it offers, can be made available to our fighting men and women and the doctors who care for them.

Portable HBOT can be put in ambulances, field hospitals, helicopters and of course, surgical/recovery centers. It is even possible for chambers in the field to be passed through the "pressure.lock doors" of larger, more stationary chambers such that the occupant would never need to under go "de.pressurization" from point of pick-up on the battle front to point of treatment by a physician. Consider the benefits of our injured being transported in a "pressure stretcher".

HyperbaricsRx portable hyperbaric chambers (FDA 510K approved) are easily operated and built to withstand extreme and challenging environments. For additional information or a product demonstration contact us at: www.hyperbaricsrx.com

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