Chronic hyperbaric exposure activates proinflammatory mediators in humans.

Decompression illness (DCI) is an illness affecting divers subjected to reductions in ambient pressure. Besides a mechanical explanation to DCI, an inflammatory mechanism has been suggested. In this study, levels of interleukin (IL)-8, IL-6, IL-1 receptor antagonist (IL-1ra), secretory leukocyte protease inhibitor (SLPI), and neutrophil gelatinase-associated lipocalcin (NGAL) were measured in divers before and after a 2-mo period of daily diving. The divers were military conscripts and completed their diving period with no clinical symptoms of DCI. We found no change in IL-6 and IL1-ra but did find an increase in IL-8 and NGAL together with a decrease in SLPI levels. The findings suggest an inflammatory activation. This activation is not severe because no changes in IL-6 or IL-1ra were found. The increase in NGAL and IL-8 levels were interpreted as a sign of leukocyte activation. The decreased SLPI levels suggest an influence on the inflammatory defense mechanism. All in all, the findings of this study show a compensated activation of the inflammatory defense mechanism without loss of homeostasis of the inflammatory system.