History

Much of what is known about the effects of hyperbaric treatment comes from observations and studies of caisson workers and divers. The first description of a pressurization vessel dates to 1662, when Henshaw used bellows to increase and decrease pressures to treat respiratory problems. The nineteenth century saw the advent of caisson workers for bridge construction and the subsequent description of caisson’s disease (or decompression sickness), bubble theory, and oxygen toxicity by Paul Bert in 1878 (Elliott, 1995). Eleven years later, Moir used recompression to treat decompression sickness in caisson workers building the Hudson River tunnel. The twentieth century also brought about extensive research and application of hyperbaric therapy for decompression sickness by the military. As we enter the twenty-first century, research is being conducted on a variety of disorders, including stroke, myocardial infarction, and autism.

Modern use of HBO to potentiate the effects of radiation in cancer patients began in 1955 (Kindwall, 1995). The National Academy of Science–National Research Council appointed a committee to review the physiologic basis for HBO in 1962. In 1966, this group published Fundamentals of Hyperbaric Medicine, which describes the physical and physiologic effects of HBO. However, it did not address clinical conditions treated with hyperbaric treatment (UHMS, 1996). The Undersea Medical Society (UMS) was founded in 1967 and was primarily devoted to diving and undersea medicine. The UMS became the Undersea and Hyperbaric Medical Society (UHMS) in 1986. The UHMS is the primary, worldwide source of information on hyperbaric and diving medicine. The purpose of the UHMS is to “improve the scientific basis of hyperbaric oxygen therapy, [and] promote sound treatment protocols and standards of practice” (UHMS, 2009).

Physiologic effects

The mechanical effect of HBO follows the physical law described by Boyle, which states that as pressure increases, volume decreases. Therefore, in the case of decompression sickness or air/gas embolism, hyperbaric treatment is used to decrease the size of the air bubble or embolism. Physiologic effects of HBO use the physical law described by Henry’s law, which states that the amount of gas dissolved in a liquid is directly proportional to the partial pressure of the dissolved gas. As a result, oxygen tensions can be raised 10 to 13 times higher than oxygen breathed at ambient pressure (Hammarlund, 1995). With these increases in oxygen tension, oxygen acts as a drug and has several effects on wound healing (Table 22-1).

TABLE 22-1 Effects and Mechanisms of Hyperbaric Oxygen Therapy on Wound Healing

HBO increases the capacity of blood to carry and deliver oxygen to tissues. This hyperoxygenation occurs because oxygen is administered under pressure to the patient. Consequently, hyperbaric treatment significantly enhances oxygen delivery to compromised tissues, increases oxygenation to the tissues, and may restore perfusion to compromised areas. The increased capacity of blood to carry oxygen assists in the restoration of cellular function. The volumetric levels of diffusion achieved with HBO are two to three times those obtained under normobaric conditions.

Oxygen is a powerful vasoconstrictor and can be helpful in managing edema related to traumatic wounding or crush injuries. Although HBO may seem injurious in that it decreases blood supply to an injured area, the increase in diffusion of oxygen more than compensates for the decrease in circulation associated with vasoconstriction. The effect of HBO in blood is instantaneous, with a subsequent plateau in soft tissues approximately 1 hour after exposure. The effect of HBO declines steadily over 2 to 4 hours after exposure (Hammarlund, 1995).

Indications

The UHMS continuously reviews scientific data regarding the therapeutic benefit of HBO. It currently has designated the conditions or disease processes listed in Box 22-1 as indications for hyperbaric therapy (Gesell, 2008). HBO is the primary therapy for arterial gas embolism, carbon monoxide poisoning, and decompression sickness. When used for any other indication, hyperbaric therapy must be incorporated as part of the plan of care that includes appropriate clinical and surgical treatments (Cianci and Sato, 1994; Gesell, 2008; Hopf et al, 2006; Marx, 1995). The effects of HBO on wound healing and the mechanisms for those effects are listed in Table 22-1. Patient selection should focus on the origin and hypoxic nature of wound. For example, a pressure ulcer is best treated with pressure reduction; a hypoxic wound is best treated by maximization of oxygen to the wound. Indications specific to wound management recommended by national organizations and guidelines are listed in Table 22-2.

TABLE 22-2 Wound-Related Indications for Hyperbaric Oxygen Therapy

HBO may be considered for the treatment of patients with limb-threatening diabetic and vascular insufficiency wounds of the lower extremity (Hopf et al, 2006; Steed, et al, 2006; UHMS, 2010; Wound, Ostomy and Continence Nurses Society [WOCN Society], 2004, 2008). To meet Centers for Medicare Medicaid Services criteria, the lower extremity diabetic wound must be Wagner grade III or higher and not responsive to standard wound care, including assessment and correction of vascular insufficiency, maximization of nutritional status, optimization of glycemic control, debridement of nonvital tissue, and maintenance of moist wound healing with the use of topical dressings. Infection should be resolving, and the wound must be appropriately offloaded as described in Chapter 14. Transcutaneous oximetric values greater than 400 mm Hg during HBO exposure indicates a likely successful outcome in the diabetic lower extremity wound. Transcutaneous oximetric values less than 15 mm Hg when breathing room air and less than 100 mm Hg during HBO exposure are predictive of wound healing failure (Broussard, 2003; Fife et al, 2002). Although it is understood that not all wounds heal, consideration for hyperbaric treatment should be given to those patients with lower extremity wounds when it is known that these wounds may not heal. Hyperbaric treatment could mean the difference between limb salvage, a transmetatarsal, below-the-knee or above-the-knee amputation with appropriate circulatory assessment, intervention, and preamputation preparation with HBO.

Crush injury, compartment syndrome, and acute traumatic ischemia benefit from hyperbarics because of the improved oxygen tension in tissue that is inadequately perfused because of a disruption of blood supply and edema associated with injury. HBO helps to decrease edema through its vasoconstrictive action. In addition, it helps to decrease reperfusion injury. The use of hyperbarics in these cases is emergent, and patients should be treated as early as possible for the best outcome.

Clostridial myonecrosis and necrotizing fasciitis are emergent conditions treated with surgical excision and HBO. Clostridial myonecrosis is an anaerobic bacterial infection where clostridial toxins cause tissue death in advance of the bacteria. HBO helps to neutralize the effects of the toxins and halts the progression of tissue destruction. Necrotizing fasciitis is an acute bacterial infectious process that may include anaerobic and aerobic bacteria that act synergistically to cause rapid tissue destruction. Hyperbarics, as an adjunct to surgical intervention, improves oxygenation and may have a direct effect on anaerobic bacteria as well as improving neutrophil activity.

Chronic osteomyelitis occurs when repeated attempts of standard interventions have failed. It is thought that HBO improves available oxygen at the bone site to improve leukocyte killing ability through oxidative mechanisms. In addition, antibiotic activity may be enhanced. It is also thought that osteoclastic activity and osteogenesis are improved with the use of HBO.

Delayed radiation injury results from endarteritis and subsequent tissue hypoxia. There typically is a latent period of at least 6 months before the effects of delayed injury are seen. Injury may not be seen for many years and often is precipitated by injury or surgical procedures. HBO is used prophylactically before oromaxillary surgical procedures to prevent osteoradionecrosis. Soft tissue radiation injuries, including proctitis and cystitis, can be treated with HBO. The rationale for use of hyperbarics is induction of neovascularization in the irradiated area.

Compromised grafts and flaps benefit from HBO by facilitating increased distance of oxygen diffusion, thereby supporting the ischemic graft or flap. In addition, it now is believed that graft and flap failure may have a component of reperfusion injury that is overcome with the administration of HBO. Hyperbarics is not indicated in uncomplicated grafts or flaps, nor is it indicated in bioengineered tissues.

HBO has been and is being used for other disease processes and conditions (Box 22-2). Although the UHMS currently does not recognize the use of hyperbaric treatment in these instances, research continues and is providing support (Asamoto et al, 2000; Baugh, 2000; Bern et al, 2000; Carl et al, 1998; Gottlieb and Neubauer, 1988; Hughes et al, 1998; Ishihara et al, 2001; Jordan, 1998; Laden, 1998; Mayer et al, 2001; Mychaskiw et al, 2001; Neubauer, 1998; Nighoghossian and Trouillas, 1997; Pascual, 1995; Reillo and Altieri, 1996; Wallace et al, 1995). In a systematic review of the literature, the WOCN concluded there is insufficient evidence to support the use of HBO in the treatment of pressure ulcers (WOCN, 2010).

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