Relative susceptibility of altitude-acclimatized mice to acute oxygen toxicity.

The influence of hypoxic acclimatization at altitudes of 0, 5,000, or 15,000 ft on the relative susceptibility to acute oxygen poisoning was determined in 288 adult female mice. After acclimatization periods of 1, 2, 4, or 8 wk, the mice were exposed to oxygen at high pressures (OHP) of 4, 6, or 9 ATA and the times to convulsion and death recorded. A factorial analysis of variance indicated that altitude and OHP level had inverse, log-linear effects on both parameters. The duration of acclimatization progressively decreased the time to death. The onset of convulsions and death was independent of body weight. There were significant interactions on the measured parameters between various combinations of altitude, OHP level, and duration of acclimatization. While alterations in the metabolism of gamma-aminobutyric acid and high-energy compounds are common to both hypoxia and hyperoxia, the most plausible explanation of the results relates to the decrease in buffer base induced by hypoxic acclimatization which might have caused CO2 potentiation of OHP symptoms.