Vol. 85, Issue 3, 798-806, September 1998
Relationship between T-wave amplitude and oxygen pulse in
guinea pigs in hyperbaric helium and hydrogen
Susan R.
Kayar,
Erich C.
Parker, and
Eugenia O.
Aukhert
Albert R. Behnke Diving Medicine Research Center, Naval Medical
Research Institute, Bethesda, Maryland 20889-5607
Diving is
known to induce a change in the amplitude of the T wave
(ATw) of
electrocardiograms, but it is unknown whether this is linked to a
change in cardiovascular performance. We analyzed ATw in guinea pigs at 10-60
atm and 25-36°C, breathing 2%
O2 in either helium (heliox;
n = 10) or hydrogen (hydrox;
n = 9) for 1 h at each pressure. Core
temperature and electrocardiograms were detected by using implanted
radiotelemeters. O2 consumption rate was measured by using gas chromatography. In a previous study (S. R. Kayar and E. C. Parker. J. Appl.
Physiol. 82: 988-997, 1997), we analyzed the
O2 pulse, i.e., the
O2 consumption rate per heart
beat, in the same animals. By multivariate regression analysis, we
identified variables that were significant to
O2 pulse: body surface area,
chamber temperature, core temperature, and pressure. In this study,
inclusion of ATw made a
significantly better model with fewer variables. After normalizing for
chamber temperature and pressure, the
O2 pulse increased with increasing ATw in heliox
(P = 0.001) but with decreasing
ATw in hydrox
(P < 0.001). Thus
ATw is associated with the
differences in O2 pulse for
animals breathing heliox vs. hydrox.
diving; gas density; electrocardiogram; heart rate; high pressure
neurological syndrome; metabolic rate; telemetry
