We previously hypothesized that the number of bubbles emerging on
decompression from a dive, and the resultant risk of
decompression sickness (DCS), may be reduced by a process whereby effective gas micronuclei that might otherwise have formed bubbles on
decompression are shrunk and eliminated. In a procedure defined by us as denucleation, exposure to hyperbaric
oxygen (HBO) would result in
oxygen replacing the resident gas in the micronuclei, to be subsequently consumed by the mitochondria when the
oxygen pressure is reduced. Support for the validity of our hypothesis may be found in our previous studies on the transparent prawn and the reduction of DCS in the rat. In all of these studies, HBO pretreatment was given before supersaturation with inert gas at high pressure. The purpose of the present study was to compare DCS outcome in rats that underwent
nitrogen washout (denitrogenation) alone (9 min O(2) at 507 kPa) after exposure to air at high pressure (33 min at 1,266 kPa), and rats treated by both procedures (denitrogenation + denucleation; 8 min of O(2) breathing followed by 5 min air breathing, both at 507 kPa) after high-pressure air exposure. This was done with the same
nitrogen load in both groups before the final
decompression (a
nitrogen pressure of 467 kPa in fatty and 488 kPa in aqueous tissue). Six of 20 rats in the denitrogenation + denucleation group died, compared with 13 in the denitrogenation group (P < 0.03). Three rats in the denitrogenation + denucleation group suffered mild DCS, recovering completely within 2 h of
decompression. The present study indicates an advantage in considering both denitrogenation and denucleation before
decompression. This may have practical application before escape from a disabled submarine, when aborting a technical dive, or in the preparation of aviators for high altitude.