title: Increasing activity of H(2)-metabolizing microbes lowers decompression sickness risk in pigs during H(2) dives.
abstract: The risk of decompression sickness (DCS) was modulated by varying the biochemical activity used to eliminate some of the hydrogen (H(2)) stored in the tissues of pigs (19.4 +/- 0.2 kg) during hyperbaric exposures to H(2). Treated pigs (n = 16) received intestinal injections of Methanobrevibacter smithii, a microbe that metabolizes H(2) to water and CH(4). Surgical controls (n = 10) received intestinal injections of saline, and an additional control group (n = 10) was untreated. Pigs were placed in a chamber and compressed to 24 atm abs (20.6-22.9 atm H(2)). After 3 h, the pigs were decompressed and observed for symptoms of DCS for 1 h. Pigs with M. smithii had a significantly lower (P < 0.05) incidence of DCS (44%; 7/16) than all controls (80%; 16/20). The DCS risk decreased with increasing activity of microbes injected (logistic regression, P < 0.05). Thus the supplemental tissue washout of the diluent gas by microbial metabolism was inversely correlated with DCS risk in a dose-dependent manner in this pig model.
authors.affiliation: Naval Medical Research Center, 503 Robert Grant Ave., Silver Spring, MD 20910-7500, USA.
authors.forename: S R
authors.initials: SR
authors.lastname: Kayar
authors.forename: A
authors.initials: A
authors.lastname: Fahlman
authors.forename: W C
authors.initials: WC
authors.lastname: Lin
authors.forename: W B
authors.initials: WB
authors.lastname: Whitman
mesh_terms: D000818:Animals; D001274:Atmospheric Pressure; D001835:Body Weight / Q000502:physiology; D003664:Decompression; D003665:Decompression Sickness / Q000517:prevention & control*; D006859:Hydrogen / Q000378:metabolism*; D008297:Male; D008697:Methane / Q000378:metabolism; D017013:Methanobacteriaceae / Q000378:metabolism*; D012306:Risk; D013552:Swine
chemical_list: D006859:Hydrogen; D008697:Methane