Trauma to a limb, leading to direct tissue damage plus local hypoxic conditions from resulting edema, causes acute traumatic peripheral ischemia. The trauma can vary from mild to irreversible and may involve major blood vessels and nerve injuries. For severe injuries, amputations may be required. Sometimes, vascular repair and reimplantation may be required for the limb to be viable. Examples of trauma include crush injury and thermal injury. Even without major vascular injuries, the tissue damage may lead to edema formation causing tissue hypoxia, leading to more edema formation. This vicious cycle can lead to compartment syndrome within in poorly compliant muscle compartments, which then presents a surgical emergency to salvage the limb. Threatened flaps also fall into the category of acute traumatic peripheral ischemia where hyperbaric oxygen has shown to improve ischemia.
Surgical treatment and hyperbaric oxygen are not competing treatment modalities, but are best used to complement each other to provide the best outcome for the patient.
Treating acute traumatic peripheral ischemia is one of the 13 approved hyperbaric oxygen indications by the Undersea and Hyperbaric Medical Society.  It is, also, approved by the Centers for Medicare and Medicaid Services (CMS).
The organization states that when a patient has acute traumatic peripheral ischemia or when a patient is suffering from crush injuries, and surgeons have sutured severed limbs, HBO therapy is a valuable, supplementary treatment physicians may use in combination with accepted, standard, therapeutic measures when patients may lose function, limb, or life.
After an acute traumatic injury to a limb, injury to blood vessels will lead to bleeding into tissues with subsequent coagulation and stasis in the vessels, which leads to hypoxia in the cells and the inability to maintain the metabolic demand important to maintain adequate intra-cellular water. The resulting edema causes increased pressure, causing more ischemia and hypoxia, leading to more cell death and extra-vascular water. Once blood flow is restored, subsequent ischemia-reperfusion injury occurs. The endothelial layer of the vessels becomes injured and fluid extravasates causing edema besides progressive obstruction of blood flow caused by neutrophils that adhere to the injured vessel wall.
Hyperbaric oxygen works in multiple ways to help with those acute changes at the cellular level. First, it produces vasoconstriction by about 20%, which means less inflow of fluid (blood and plasma) into the injured area, but since the dissolved oxygen in plasma is at least doubled (from that of breathing 100% oxygen by facemask), there is a net increase in oxygen delivery. This vasoconstriction results in less edema and increased oxygen diffusion distance. Hyperbaric oxygen, also, reduces the adhesion of neutrophils to the injured endothelium which blunts the ischemia-reperfusion injury.
Emergency surgical treatments such as revascularization and fracture stabilization should come before considering hyperbaric oxygen treatments. In some less urgent cases, hyperbaric oxygen treatments may help the surgeon better demarcate viable from dead tissue and thus minimize tissue loss and reduce the risk of amputations. The decision to use and frequency of hyperbaric oxygen should be made in close collaboration with the surgeon and depends on the injury type, the injury severity, and patient host factors. It is best to use an objective grading system such as the Gustillo open-fracture crush injury grading system while adding a host factor function score that includes, age, smoking, steroid use, ambulation status, cardiovascular and kidney function. This improves patient selection and the treatment algorithm, with the idea that even milder type injuries in a compromised host benefit from hyperbaric oxygen as adjuvant therapy. Utilization review of hyperbaric treatments is an important part of the clinical care of those patients and is best done in close collaboration with the surgical and hyperbaric team after a certain number of predetermined hyperbaric treatments.
There are no direct contraindications to hyperbaric oxygen in acute traumatic peripheral ischemia unless use delays emergency, limb-saving operations such as revascularization or established compartment syndrome. There are few absolute contraindications to hyperbaric oxygen, such as an unrelieved tension pneumothorax.
A pressure vessel and 100% oxygen are the tools to provide the benefits of hyperbaric oxygenation to the body. There are 2 types of pressure vessels, mono-place chambers, and multi-place chambers. Mono-place chambers which can hold only one person. They are usually made of a transparent acrylic tube with patient access through a metal door on one end. In mono-place chambers, 100% oxygen is used to pressurize the tube while the patient is breathing the chamber's ambient oxygen. Some of those mono-place chambers are equipped with a separate breathing mask to provide air when air breaks are used. Mono-place chambers can be outfitted with ventilators, infusion pumps, and physiologic monitoring capabilities to provide high acuity care. Mono-place chambers can fit into a standard hospital room and get piped into the hospital oxygen and air supply.
Multi-place chambers are made of steel with acrylic viewing ports and can fit 2 to more than 20 people. They are pressurized with air while the patients breathe oxygen through either a tight-fitting mask or a special hood that is sealed around the neck with a rubber neck dam. For any potential air breaks the patients will breathe the chamber air. These multi-place chambers are often large complexes with large compressors and reserve air and oxygen tanks.
Both chamber types require special manufacturing and installation guidelines which are governed by special fire protection codes such as NFPA 99 in the United States. Facility accreditation of hyperbaric programs is recommended and available through the Undersea and Hyperbaric Medical Society in the United States and some international locations.
A transcutaneous oximeter can be helpful in determining the level of tissue oxygen tension on room air and during hyperbaric treatments and have been shown to have a positive predictive value of 0.88 for healing when a level over 200 mm Hg is reached during the treatment.
For mono-place chambers, one specially trained outside attendant may conduct and supervise up to 2 simultaneous hyperbaric chamber treatments and must be in continuous attendance outside the chambers. Multi-place chamber operations require both outside and inside specialty trained attendant(s). Those inside attendants are breathing compressed chamber air and can be at risk for decompression illness just like a scuba diver. Appropriate safety protocols and procedures must be in place to minimize that risk. An outside chamber operator is pressurizing the chamber and is in constant communication with the inside attendant.
A safety director is required to ensure maintenance and safe operations for the hyperbaric facility.
A specialty trained hyperbaric physician prescribes and supervises the pressure, time, and gas profiles of the hyperbaric treatments and examines the patient before and after the hyperbaric treatments. A specialty trained hyperbaric nurse provides expert wound care, administers medications, and provides training and education to the patients.
Safety procedures are required to minimize the introduction of static electricity, fuel and ignition sources into the hyperbaric environment, to decrease the risk of fire. Everyone inside must wear cotton or cotton blend sheets and scrubs. Oily substances and alcohol must be avoided, and ignition sources are not allowed. In rare cases, where the patient has difficulty equalizing their ears during the pressure change, myringotomy tubes may have to be placed.
Depending on the injury of the patient, dressing changes and wound debridement may be required before the patient enters the hyperbaric chamber. If patients require monitoring during the hyperbaric treatment, appropriate sensors will have to be applied and connected to pass-through connectors in the hull. If the patients require medications or infusions, those may need to be prepared for special infusion pumps. Good communication between the primary surgical service and the hyperbaric medical team is of the utmost importance.
The attending hyperbaric medicine specialist will prescribe the time, the pressure and the breathing gas in a treatment table for the patient (and if the treatment is scheduled in a multi-place chamber, they will also plan the dive profile for the inside attendants). Common treatment tables for acute traumatic peripheral ischemia are 2 atmospheres absolute (ATA) for 2 hours or 2.4 ATA for 90 minutes. The number of treatment tables that have been suggested varies by type of injury. For preventing ischemia-reperfusion injury, a single treatment may be sufficient. For crush injuries, a much more aggressive schedule of 8 treatments (1 treatment 3 times a day for 2 days, the twice a day for 2 days followed by once a day for another 2 days) may be required. For an impending compartment syndrome, 3 treatments (2 twice a day on the first day and 1 on the second day) are recommended. While any established compartment syndrome requires a fasciotomy, hyperbaric oxygen may still be useful following the fasciotomy to treat residual concerns such as tissue ischemia, massive swelling or nerve injury and may require twice daily treatments for up to 7 days. 
Hyperbaric oxygen is usually well tolerated. Occasionally patients who have difficulty equalizing may develop barotrauma to the ears. This can usually be managed with nasal decongestants and rarely requires myringotomy tubes to be placed by an otolaryngological surgeon. Pulmonary barotrauma is very rare; however, the possibility of pulmonary trauma should be considered when patients develop chest pain on an ascent. Pulmonary and cerebral oxygen toxicity is typically not an issue with the relatively short exposures used for acute traumatic peripheral ischemias but can occur.
Acute traumatic peripheral ischemia can be devastating and can lead to permanent loss of the limb or function. The cost of amputation with rehabilitation and the resulting loss of productivity far outweighs the cost of salvage and reconstruction, even including the use of appropriate hyperbaric oxygen therapy, which only adds about 10% to the overall cost. Hyperbaric oxygen therapy is an often overlooked adjunct therapy to surgery and can help reduce the vicious cycle of edema, ischemia, and hypoxia as well as reducing the deleterious effects of an ischemia-reperfusion injury. Unfortunately, hyperbaric oxygen is often only thought of to mitigate late complications, rather than applying it early helping to reduce tissue loss.
The management of acute traumatic peripheral ischemia is challenging and complex. While it is in the realm of the trauma surgeon and the orthopedist, there are other important members of the health care team that can offer expertise and skills to improve patient outcomes. Defining the patients who might best benefit from hyperbaric oxygen therapy, the Undersea and Hyperbaric Medical Society has suggested a treatment algorithm that considers the type and severity of trauma based on the Gustillo classification, but also patient host function factors that may influence the treatment decision. The optimal treatment plan after a severe traumatic injury is best done with a multi-disciplinary approach.
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