Incident Insight reprinted from Alert Diver magazine
By Dr Nicholas Bird
Hyperbaric Oxygen Therapy: Beyond the Diving Injury
>For most divers, hyperbaric medicine is immediately associated with diving injuries. The use of hyperbaric chambers for treatment of decompression illness dates back to the 1800s, but the field of hyperbaric medicine has evolved beyond treating injured divers – although this remains an important pillar of hyperbaric medicine. Of the approximately 1,200 hyperbaric oxygen therapy (HBOT) centers around the United States, all but two (University of Southern California Catalina Hyperbaric Chamber and Pacific Grove Hyperbaric Chamber in Monterey, Calif.) spend most of their time treating non-diving associated injuries.
>In the 1950s, the role of HBOT started to expand, with applications including certain severe bacterial infections, radiation therapy, carbon monoxide poisoning and open heart surgery. Today, the field of hyperbaric medicine is overseen by the Undersea and Hyperbaric Medical Society, which provides scientific oversight and determines which treatment applications are acceptable based on supporting evidence.
>Applications of HBOT
>There are currently 13 approved indications for HBOT including diving-related injuries. Of these, the most frequently treated ailments are diabetic foot ulcers, delayed effects of radiation, threatened flaps/grafts, acute carbon monoxide poisoning, crush injuries, refractory osteomyelitis, gas gangrene and necrotizing fasciitis.
>HBOT treats patients for acute and chronic issues. For chronic conditions, the treatments are commonly performed on a once-daily basis and are approximately two hours in duration. When the need for treatment is acute or the condition sudden in its onset, treatments may occur more frequently or for longer durations.
>One of the great aspects of treating people with HBOT comes from watching their progress and the results that exceed expectation. To illustrate some of the applications of HBOT beyond diving injuries and the results it can have, I would like to describe a few case histories (names have been changed to protect the privacy of the individuals).
>Radiation cystitis is a potential manifestation of the delayed effects of radiation therapy and can result from treatment of pelvic cancers. In the months and years following external beam radiation therapy, the irradiated area can undergo progressive destruction of the capillaries that feed tissues. If this occurs, affected tissue sloughs or dies off, and exposed inflamed tissue can bleed. When bleeding like this occurs in the bladder, blood clots can form and block urinary outflow. As one might imagine, these patients feel miserable. They often require catheterization, bladder irrigation (because clots continually block outflow) and sometimes blood transfusions. For chronic conditions like radiation cystitis, HBOT is a daily procedure and commonly requires 30-40 treatments to reach resolution.
>John was referred to our clinic for radiation cystitis. He arrived frustrated, as he and his urologist had attempted the standard treatments with no result. When John started, he was fairly skeptical, and the thought of being in an enclosed space made him uncomfortable. With the help of our staff coupled with his motivation, he started down the road to recovery.
>About three weeks into the treatments, John reported his bleeding was slowing. After a month, he noted that his bleeding rate had reduced by half and after 40 treatments, it had stopped completely. When his urologist performed a cystoscopy (a camera examination of the bladder), he was pleased to see how healthy and intact the tissue appeared. John was discharged from our care and has not needed to return for subsequent treatment.
>Individuals that require this treatment almost invariably benefit. Significant improvements or resolution of bleeding and reductions in pain are expected results. HBOT is considered definitive in these cases. In my experience (and that of other hyperbaric physicians I've talked to), bleeding that presents after months or years of symptom control should prompt cystoscopic (bladder camera) evaluation for tumor recurrence, as this represents both the most likely and worrisome explanation.
>Diabetic Foot Ulcers
>Diabetes is a disease that impacts blood sugar control; the end result of this progressive condition is destruction of the microvasculature (capillaries). These small blood vessels are responsible for supplying tissues, and their compromise results in organ or tissue damage. Examples include diabetic retinopathy (eye disease), kidney disease and loss of sensation - especially affecting the feet (peripheral neuropathy), foot ulcers and tissue necrosis (dead tissue).
>One of the miraculous results of HBOT leveraged in both diabetic wound care and for delayed effects of radiation is the promotion of new blood vessel growth in compromised areas suffering from inadequate oxygen supply. As with radiation cystitis, diabetic ulcers commonly require 30-40 treatments along with wound care and sometimes surgical assistance.
>Robert came to us for treatment of a great toe ulcer that had progressed rapidly, become infected and now involved the underlying bone. In many of these cases, the toe is ultimately removed, but our treatment goals focus on preserving the foot and the ability to walk as well as ensuring the surgical wound heals. Because of the impact to his nerves from a lack of good circulation, Robert could not feel this ulcer (a condition known as peripheral neuropathy). Unfortunately, his vascular supply to the tissues at the base of the foot was unable to support post-operative healing; the inadequate circulation coupled with his lack of pain enabled him to walk on a limb that should have remained non-weight bearing.
>As one might anticipate, the surgical wound opened and the foot was vulnerable to both infection and subsequent tissue loss. This is where our HBOT story begins.
>We started him on a HBOT course coupled with regular wound care. Week by week, we saw improvement. After about 40 treatments, the wound healed and the rest of the foot was spared from further tissue loss and surgical amputation. After what amounted to months of work, watching him walk out of our clinic and back to his life and family was truly gratifying.
>HBOT is used with increasing frequency as adjunctive therapy for this pervasive problem. In conjunction with wound care, vascular surgery, blood sugar management and dietary counseling, HBOT is a powerful tool that promotes healing and tissue and limb salvage.
>Acute Carbon Monoxide Poisoning
>While the bulk of hyperbaric treatments performed are for chronic conditions, most of the approved indications are for acute issues. Of these acute indications, HBOT plays a significant role in the treatment of acute carbon monoxide (CO) poisoning – the leading cause of poisoning deaths in the US.1 CO poisoning is dangerous for several reasons. First, it impedes oxygen transportation to tissues, most importantly the brain and heart. It also sets up an inflammatory process that promotes additional tissue injury. Brain injury can impact cognitive and motor abilities, while heart muscle damage may result in rhythm disturbances (arrhythmias) or functional impairment.
>CO is bound and transported in the body on hemoglobin (the iron containing molecule in red blood cells that also transports oxygen and carbon dioxide). Hemoglobin has over 200 times more affinity for CO than oxygen. As such, CO not only preferentially occupies oxygen-binding sites on red cells, but also doesn't quickly release. Exposure to elevated CO levels may result in decreased tissue oxygen delivery as well as instigate a systemic inflammatory response that can cause further tissue injury.
>HBOT speeds the removal of CO from the body. In a study using volunteer subjects, the average time necessary to reduce blood CO levels by half, (written as T1/2, where T is time) was 320 minutes (range of 128 – 409 minutes).2 When exposed to HBOT at 3 atmospheres absolute (ATA), the T1/2 decreases to approximately 23 minutes.3 HBOT also inhibits the tissue destructive inflammatory processes instigated by CO, which can persist after CO levels drop to within normal limits. It is for this reason that measurement of CO blood concentration (abbreviated COHb – carboxyhemoglobin) alone is not the sole determinant of whether HBOT is used or a reliable measurement of poisoning severity. COHb will naturally decline with time, but tissue damage may persist after CO blood levels have declined to normal or expected levels. In cases of prolonged subacute exposure which can include warehouses, parking garages, auto shops etc.), COHb may never reach severe levels but may still produce signs of toxicity. Therefore symptom history, especially loss of consciousness or neurological or acute cognitive deficits, plays a larger role in determining whether HBOT is utilized in the acute period (within 24-48 hours) following documented exposure.
>Nancy was nearly unconscious and exhibited reduced motor and cognitive abilities when she arrived at our department. She was barely able to communicate or move; we started treatment immediately. We performed a total of seven treatments on a twice-daily basis noting the most remarkable improvement after her fourth. After her third treatment, she was able to talk to us, but still had some cognitive delays and motor impairments. Prior to her fourth treatment, she was unable to raise both of her arms and lacked that telling look in her eyes signifying cognitive engagement. I will always remember watching her through a porthole during her fourth treatment, when with a big smile, she raised both her arms, and I could see the twinkle in her eyes, that just an hour before wasn't there.
>Three days after her arrival, Nancy walked out of the hospital with minimal assistance and, within days of discharge, was walking on her own and reengaging in her life. A year later and fully recovered, Nancy and I had the opportunity to dive together.
>The use of HBOT for CO poisoning is available in many centers around the country and the world. Most treatment courses consist of one to three treatments and provide a powerful means of both removing CO from the body as well as minimizing the toxic effects on tissue.
>Prevention is the most important consideration. Ensure proper ventilation around any fire, furnace or engine and consider installing CO detectors in your home. In severe cases of CO toxicity, HBOT can be a powerful therapy, which speeds symptom resolution and minimizes delayed neurological sequela (symptoms that either remain or present after initial symptom resolution).
>Amongst the most dramatic and life changing of the hyperbaric indications is "flesh-eating bacteria," a condition known as necrotizing fasciitis. In this setting, HBOT is used in conjunction with antibiotics and surgery; HBOT helps reduce tissue loss and minimizes the extent of tissue removal during surgery. In some cases, HBOT may also enhance antibiotic effectiveness and reduce bacterial growth.
>On the evening we met Wendy, we received the call from the emergency department physician who was watching an infection spread before his eyes. Started from a minor injury at school, the infection had taken root and was spreading up her hand and into her arm. HBOT and antibiotics were started immediately, quickly followed by surgery. In the operating room we could see the damage clearly. We were concerned; if we couldn't stop the infection, Wendy would lose her arm or, worse, her life. She was treated twice daily, received advanced wound care and underwent multiple surgeries. After her first few treatments, we could see a slowing of the infection's destructive march up her arm and the involved tissues were improving. With each operation we removed less and less tissue and felt we were getting ahead of the problem. With a multidisciplinary team including plastic surgery, infectious disease, wound care and hyperbarics, Wendy kept her arm and hand. She did lose some function of her finger muscles and hand, but was still able to care for herself.
>Necrotizing fasciitis presents acutely and is potentially life threatening. These infections commonly stem from variants of streptococcal bacteria, but may also result from other bacterial combinations. Known risk factors include skin trauma, insect bites, burns, punctures and surgical wounds. Underlying health issues and lifestyle choices that increase the chances of these infections include: diabetes, obesity, alcoholism, smoking and intravenous drug use.
>There remains a lot we don't know about how HBOT works and how it promotes healing. These cases simply illustrate some notable examples of how HBOT is currently applied in departments around the world. HBOT teams address a spectrum of illnesses and, for those of us who dive, decompression illness is thankfully one of the rarer reasons that patients require hyperbaric treatment.
- Thom, SR, Keim, LW. (1989). "Carbon monoxide poisoning: A Review epidemiology, pathophysiology, clinical findings, and treatment options including hyperbaric oxygen therapy." Clinical Toxicology 27(3): 141-156
- Peterson JE, Steward RD (1970): "Absorption and elimination of carbon monoxide by inactive young men." Archives of Environmental Health 21:165-171.
- Pace N, Strajman E, Walken EL (1950): "Acceleration of carbon monoxide elimination in man by high pressure oxygen." Science 111:652-654.