Vol. 93, Issue 5, 1583-1589, November 2002
Modulation of decompression sickness risk in pigs with
caffeine during H2 biochemical decompression
Andreas
Fahlman1,
Winston C.
Lin2,
William B.
Whitman2, and
Susan R.
Kayar1
1 Environmental Physiology Department, Naval Medical
Research Center, Silver Spring, Maryland 20910-7500; and
2 Department of Microbiology, University of Georgia,
Athens, Georgia 30602
In
H2 biochemical decompression, H2-metabolizing
intestinal microbes remove gas stored in tissues of animals breathing
hyperbaric H2, thereby reducing decompression sickness
(DCS) risk. We hypothesized that increasing intestinal perfusion in
pigs would increase the activity of intestinal Methanobrevibacter
smithii, lowering DCS incidence further. Pigs (Sus scrofa,
17-23 kg, n = 20) that ingested caffeine (5 mg/kg) increased O2 consumption rate in 1 atm air by
~20% for at least 3 h. Pigs were given caffeine alone or
caffeine plus injections of M. smithii. Animals were
compressed to 24 atm (20.5-23.1 atm H2, 0.3-0.5
atm O2) for 3 h, then decompressed and observed for
signs of DCS. In previous studies, DCS incidence in animals without
caffeine treatment was significantly (P < 0.05) lower
with M. smithii injections (7/16) than in controls (9/10). However, contrary to our hypothesis, DCS incidence was marginally higher (P = 0.057) in animals that received caffeine
and M. smithii (9/10) than in animals that received caffeine
but no M. smithii (4/10). More information on gas kinetics
is needed before extending H2 biochemical decompression to humans.
cardiac output; hydrogen diving; hyperbaria; intestine; perfusion
