OXYGEN

What is Hyperbaric Oxygen therapy?

• Hyperbaric oxygen therapy is used to increase the amount of oxygen dissolved in the plasma, by increasing the ambient pressure.

At normal atmospheric pressure, the amount of oxygen dissolved in the blood is so low, that we don’t even bother to quantify it. However, increasing the environmental pressure, using a hyperbaric chamber, increases the solubility of oxygen in the blood. If 100% oxygen is inspired at 3 atmospheres, the inspired PO₂ is over 2000mmHg, and this should increase the volume of oxygen in solution in the blood to approximately 6ml/100ml of blood. The normal A-V oxygen difference is 5ml/100ml. Increases in tissue oxygen tensions, however, vary widely – depending on local perfusion and metabolic conditions. The high pressure increases the solubility of other gases, principally nitrogen, which can come out of solution in rapid diving ascents (the bends) and embolize to tissues; a similar problem can occur with air embolism. Hyperbaric treatment reduces bubble size and improves oxygen delivery to tissues. In addition, anerobic bacteria which infect poorly perfused tissue should be terminally sensitive to increased tissue oxygen concentration, and hyperbaric oxygen (HBO) treatment is thus potentially bactericidal to clostridial and other anerobic species.

Diseases for which hyperbaric oxygen therapy is indicated (1):

• Arterial gas embolism

• Decompression sickness (the bends)

• Severe carbon monoxide poisoning

• Osteoradionecrosis

• Clostridial myonecrosis

References

   (1)    Moon RE, Camporesi EM. Hyperbaric oxygen therapy: from the nineteenth to the twenty-first century. Respir Care Clin N Am 1999; 5(1):1-5.

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