Catecholamine and phagocytic responses in infected mice exposed to hyperbaric helium-oxygen atmospheres.

Exposure of mice to exotic gaseous environments (97% helium and 3% oxygen) maintained at 20% cand 8 ATA (100 psig) increased host susceptibility to aerosol infection with klebsiella pneumoniae. The animals became ill earlier than the controls and the respiratory LD50 for the hyperbaric mice was about 50% smaller than for controls under ambient conditions. Furthermore, hyperbaricity induced an acute depression in phagocytic activity and a marked elevation in the circulating levels of epinephrine, norepinephrine and dopamine.