title: Oxygen pretreatment as protection against decompression sickness in rats: pressure and time necessary for hypothesized denucleation and renucleation.
abstract: Pretreatment with HBO at 300-500 kPa for 20 min reduced the incidence of decompression sickness (DCS) in a rat model. We investigated whether this procedure would be effective with lower oxygen pressures and shorter exposure, and tried to determine how long the pretreatment would remain effective. Rats were pretreated with oxygen at 101 or 203 kPa for 20 min and 304 kPa for 5 or 10 min. After pretreatment, the animals were exposed to air at 1,013 kPa for 33 min followed by fast decompression. Pretreatment at 101 or 203 kPa for 20 min and 304 kPa for 10 min significantly reduced the number of rats with DCS to 45%, compared with 65% in the control group. However, after pretreatment at 304 kPa for 5 min, 65% of rats suffered DCS. When pretreatment at 304 kPa for 20 min was followed by 2 h in normobaric air before compression and decompression, the outcome was worse, with 70-90% of the animals suffering DCS. This is probably due to the activation of "dormant" micronuclei. The risk of DCS remained lower (43%) when pretreatment with 100% O(2) at normobaric pressure for 20 min was followed by a 2 h interval in normobaric air (but not 6 or 24 h) before the hyperbaric exposure. The loss of effectiveness after a 6 or 24 h interval in normobaric air is related to micronuclei rejuvenation. Although pretreatment with hyperbaric O(2) may have an advantage over normobaric hyperoxia, decompression should not intervene between pretreatment and the dive.
authors.affiliation: Israel Naval Medical Institute, IDF Medical Corps, P.O. Box 8040, 31080 Haifa, Israel. rarieli@netvision.net.il
authors.forename: Ran
authors.initials: R
authors.lastname: Arieli
authors.forename: Elran
authors.initials: E
authors.lastname: Boaron
authors.forename: Yehuda
authors.initials: Y
authors.lastname: Arieli
authors.forename: Amir
authors.initials: A
authors.lastname: Abramovich
authors.forename: Ksenya
authors.initials: K
authors.lastname: Katsenelson
mesh_terms: D000465:Algorithms; D000818:Animals; D003665:Decompression Sickness / Q000235:genetics / Q000473:pathology / Q000517:prevention & control*; D006931:Hyperbaric Oxygenation; D008297:Male; D048629:Micronuclei, Chromosome-Defective / Q000187:drug effects*; D010100:Oxygen / Q000494:pharmacology / Q000627:therapeutic use*; D010102:Oxygen Inhalation Therapy; D011312:Pressure; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D010100:Oxygen