Influence of Increased Ambient Pressure and Gas Density on Cardiac Rate in Man.
NAVY EXPERIMENTAL DIVING UNIT WASHINGTON D C
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Heart rate was measured in ten normal male subjects in a hyperbaric chamber during a two phase study. In phase I graded exercise was performed at ambient pressures of 1.0, 3.27, and 5.45 Ata. At these depths, subject breathed a gas mixture having a density equal to that of the surface 1.0 Ata. and then gas mixtures having greater densities. In phase II heart rate was recorded during an extended saturation dive. Graded exercise was performed at pressures of 1, 5.54, 10.09, 19.18, and 26.75 Ata. During all these exposures subjects breathed the ambient oxygen, helium, and nitrogen chamber atmosphere. The results of these studies suggest that both the increase in ambient pressure and the increase in inspired gas density contribute to the development of bradycardia under hyperbaric conditions. Author
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