Immune function in hyperbaric environments, diving, and decompression.

The purpose of this review is to examine the influence of exposure to hyperbaric oxygen (HBO2) deep diving, and decompression on various facets of the immune response. Potential changes during exposure include a decrease in the CD4+:CD8+ ratio, a decreased proliferation of lymphocytes, and an activation of neutrophils with migration to regions of high oxygen pressure. There may also be an activation of the complement cascade during decompression. Clinical indicators of overall immune suppression include a decreased response to antigens, a weakening of autoimmune responses, and a slower rejection of allografts. In professional divers, immune changes are at least partially offset by acclimatization, and seem to have little clinical significance. However, patients receiving HBO2 are a more vulnerable group; in their case, exposure may impair immune surveillance, and a careful monitoring of immune function may be important to the success of treatment.