Albert Behnke: nitrogen narcosis.

As early as 1826, divers diving to great depths noted that descent often resulted in a phenomenon of intoxication and euphoria. In 1935, Albert Behnke discovered nitrogen as the cause of this clinical syndrome, a condition now known as nitrogen narcosis. Nitrogen narcosis consists of the development of euphoria, a false sense of security, and impaired judgment upon underwater descent using compressed air below 3-4 atmospheres (99 to 132 feet). At greater depths, symptoms can progress to loss of consciousness. The syndrome remains relatively unchanged in modern diving when compressed air is used. Behnke's use of non-nitrogen-containing gas mixtures subsequent to his discovery during the 1939 rescue of the wrecked submarine USS Squalus pioneered the use of non-nitrogen-containing gas mixtures, which are used by modern divers when working at great depth to avoid the effects of nitrogen narcosis.

[Diving: barometric pressure and neurochemical mechanisms]. / La plongée: pression barométrique et mécanismes neurochimiques.

The studies of Paul Bert, presented in his book "La Pression Barométrique" in 1878, were at the origin of the modern hyperbaric physiology. Indeed his research demonstrated the effects of oxygen at high pressure, that compression effects must be dissociated from decompression effects, and that neurological troubles and death of divers during or after decompression were due to the fast rate of decompression. However, it is only in 1935 that the work of Behnke et al. attributed the complaints reported at 3 bars and above in compressed air or nitrogen-oxygen mixture to the increase in partial pressure of nitrogen which induces nitrogen narcosis. Little is known about the origins and mechanisms of this narcosis. The traditional view was that anaesthesia or narcosis occurred when the volume of a hydrophobic membrane site was caused to expand beyond a critical amount by the absorption of molecules of a narcotic gas. The observation of the pressure reversal effect during general anaesthesia has long supported this lipid theory. However, recently, protein theories have met with increasing recognition since results with gaseous anaesthetics have been interpreted as evidence for a direct gas-protein interaction. The question is to know whether inert gases, that disrupt dopamine and GABA neurotransmissions and probably glutamatergic neurotransmission, act by binding to neurotransmitter protein receptors.

[From 1878 to 2006 - working in hyperbaric conditions during tunnelling]. / De 1878 à 2006 - Travaux hyperbares en tunnels.

To review the impact of Paul Bert's researches on hyperbaric work in tunnelling, the status of the industry in 1878 is described. Mostly based on the application of Triger's machine it was used to mine coal below the water table or to dig foundations for bridges in rivers or close to rivers. The results and conclusions obtained by Paul Bert which are applicable in that particular field are listed. The major steps of research or remarkable achievements in construction between 1878 and 2006 are presented as well as the evolution of decompression tables. Improvement in safety and conditions of caisson workers has been continuous until the technical revolution resulting from the introduction and the development of tunnelling boring machines (TBM) in the late 80's. TBM technology has resulted in major changes in tunnel construction. Hyperbaric interventions have also changed completely since human operators no longer work in pressurized conditions. Only occasional inspections and repairs are carried out under pressure. Present performance in hyperbaric conditions are reported, and high pressures reached in the 2000's using saturation technology are described. The future of hyperbaric works is also discussed whether for very high pressure, or complete replacement of caisson workers in TBMs. These descriptions show that Paul Bert provides us with very clear directions to improve safety in hyperbaric conditions and that none of his recommendations were mistaken, most being still relevant.

Submarine escape breathing air. A review and analysis of animal and human experiments by the Royal Navy.

The contribution of the Royal Navy to the development of modern submarine escape by free ascent, breathing air, from 1945 to the present time, is described. Much of the work is unpublished. Experiments in which goats were exposed to simulated escape pressure profiles while breathing air from 90 m to 300 m are described. The gradual testing of human subjects during such escape profiles is also reported up to real escapes by subjects from submarines lying at 180 m. Thus escapes are now feasible from almost anywhere on the continental shelf. Possible techniques of even deeper escape, i.e. hyperoxygenated air breathing, oxygen breathing, propulsion + retropulsion of the escaper, drogues + pressure retaining (2 atm abs) escape suits are briefly considered. The figures illustrate the Royal Navy series of animal and human, simulated and real escapes. Table I gives full details on human testing. Tables containing details of all goat exposures can be obtained from author.