The effects of barometric pressure according to Paul Bert: the question today.

The scientific activity of Paul Bert was very diverse, but his main achievements concern the effects of barometric pressure upon life. The fundamental physiological effect of decreasing barometric pressure is due to the concomitant fall of the O2 partial pressure. The effects of lowering or raising the barometric pressure can be countered by increasing or decreasing the O2 fraction in the air. Extreme hyperoxia modifies cellular metabolism of all living beings: this is O2 poisoning, the Paul Bert effect. Rapid decompressions from several atmospheres, or even from sea level to high altitude, can entail the formation of bubbles of N2 dissolved under the high pressure in the tissues and blood. Decompression accidents may be prevented by decompressing slowly. Immediate recompression is the only way to overcome decompression accidents, as the N2 is forced back into solution. These main discoveries were not universally accepted before about 1915. However, since Paul Bert's time, some additional effects of changes of the barometric pressure, for example related to the variation of gas diffusivity and density, have been pointed out. It is also clear that some factors other than low barometric pressure, for instance radiation, temperature, humidity etc. may play important roles in the mechanism of mountain sickness. However, it remains that the main factor is hypoxia, since oxygen inhalation or recompression lead to a quick recovery.