Several beneficial mechanisms are associated with intermittent exposure to hyperbaric doses of oxygen. Either alone, or more commonly, in a combination with other medical and surgical procedures, these mechanisms serve to enhance the healing process of treatable conditions.
HYPEROXYGENATION provides immediate support to poorly perfused tissue in areas of compromised blood flow. The elevated pressure within the hyperbaric chamber results in a 10–15 fold increase in plasma oxygen concentration. This translates to arterial oxygen values of between 1,500 and 2,000 mmHg, thereby producing a four-fold increase in the diffusing distance of oxygen from functioning capilliares. While this form of hyperoxygenation is only a temporary measure, it will often serve to buy time and maintain tissue viability until corrective measures can be implemented or a new blood supply established.
NEOVASCULARIZATION represents an indirect and delayed response to hyperbaric oxygen exposure. Therapeautic effects include enhanced fibroblast division, neoformation of collagen, and capillary angiogenesis in areas of sluggish neovascularization such as late radiation damaged tissue, refractory osteomyelitis and chronic ulcerations in soft tissue.
Hyperoxia Enhanced Antimicrobial Activity
Hyperoxia Enhanced ANTIMICROBIAL ACTIVITY has been demonstrated at a number of levels. Hyperbaric oxygen causes toxin inhibition and toxin inactivation in Clostidial perfringens infections (gas gangrene). Hyperoxia enhances phagocytosis and white cell oxidative killing, and has been shown to enhance aminoglycocide activity. Recent research has demonstrated a prolonged post-antibiotic effect, when hyperbaric oxygen is combined with Tobramycin against Pseudomonas aeroginosa.
ANTIBIOTIC SYNERGY. A number of antibiotics actually have enchanced results when combined with hyperbaric oxygen. A number of mechanisms get to work to cause this, including increased permeability of the cell wall. Oftentimes the prescribing physician can titrate the dosage down while achieving better results that are better than with antibiotics alone. Additionally, avoiding the toxic challenges and side effects of a medication response alone.
DIRECT PRESSURE utilizes the concept of Boyle’s Law to reduce the volume of intravascular or other free gas. For more than a century this mechanism has formed the basis for hyperbaric oxygen therapy as the standard of care for decompression sickness and cerebral arterial gas embolism. Commonly associated with divers, CAGE is a frequent iatrogenic event in modern medical practice. It results in significant morbidity and mortality and remains grossly undiagnosed.
Hyperoxia-induced VASOCONSTRICTION is another important mechanism. It occurs without component hypoxia, and is helpful in managing intermediate compartment syndrome and other acute ischemias in injured extremities, and reducting interstitial edema in grafted tissue. Studies in burn wound applications have indicated a significan decrease in fluid resuscitation requirements when hyperbaric oxygen therapy is added to standard burn wound management protocols.
Attenuation of Reperfusion Injury
ATTENUATION OF REPERFUSION INJURY is the most recent mechanism to be discovered. Much of the damage associated with reperfusion is brought about by the inappropriate activation of leukocyces. Following an ischemic interval, the total injury pattern is the result of two components: a direct irreversible injury component from hypoxia, and an indirect injury which is largely mediated by the inappropriate activation of leukocytes. Hyperbaric oxygen reduces the indirect component of injury by preventing such activation. The net effect is the preservation of marginal tissues that may otherwise be lost to ischermia-reperfusion injury.