-
160
The Last Resource
position Switching off the air in the process. In this way the diver
breathes gas
at the ambient pressure.
Unfortunately, there is more which limits diving than Boyle’s
Law. Probably one of the most surprising discoveries was that oxygen
becomes toxic at the comparavely low pressure of two atmospheres
or 33 feet down in the sea—a fact which nearly cost Cousteau his
life during experiments with the oxygen—fed apparatus. Nor is
oxygen the only atmospheric gas to become dangerous: nitrogen
induces a form of narcosis not unlike that produced by alcoholic
intoxication. At 300 feet the diver can become so drunk that he will
gaily tear off his mask to join the sh—with fatal results. Cousteau
called this narcotic effect ‘rapture of the deep’. To complete the
picture, as the pressure increases the gases become so thick and
heavy that they are diicult to breathe.
_
The eminem British scientist, ]. B. S. Haldane, discovered many
years ago that raising the ambient pressure increases the oxygen—
carrying capacity of blood serum as opposed to the haemoglobin in
the corpuscles, the normal oxygen—carriers. This means that, volume
for volume, less oxygen is needed in air breathed under pressure.
.
Nevertheless the toxicity of pure oxygen supplies at pressures as low.
as two atmospheres has not been completely explained. Since the
_
amounts of oxygen in a breathing mixture can be reduced, this toxic
reaction does not present such a serious problem as the ill—effects
experienced from nitrogen—normally a physiologically inert gas.
_
After irtation with the idea that carbon dioxide accumulating in
the body under pressure might be the cause, most scientists have
come to the view that the nitrogen dissolves in the fatty surface
membranes of cells, including nerve cells, thereby slightly changing
their properties. Nitrogen is not the only inert gas to do this; it is
even possible to determine the likely effects of other gases being
considered for diving mixtures by their afnity with ‘fatty sub—
stances’.
»
-
By good fortune, one of the safest gases, helium, had already been
called into service largely because its lightness makes breathing
easier. The helium acts as a passive carrier for oxygen but, although
this inert gas does not react with the body’s tissues, the pressure still
forces it into them. The diver becomes the human equivalent of a
soda siphon with helium in place of Carbon dioxide. Release the
pressure abruptly by rapidly ascending from depth, and the gas
bubbles out of solution. Getting these bubbles in the wrong parts
160
The Last Resource
position Switching off the air in the process. In this way the diver
breathes gas
at the ambient pressure.
Unfortunately, there is more which limits diving than Boyle’s
Law. Probably one of the most surprising discoveries was that oxygen
becomes toxic at the comparavely low pressure of two atmospheres
or 33 feet down in the sea—a fact which nearly cost Cousteau his
life during experiments with the oxygen—fed apparatus. Nor is
oxygen the only atmospheric gas to become dangerous: nitrogen
induces a form of narcosis not unlike that produced by alcoholic
intoxication. At 300 feet the diver can become so drunk that he will
gaily tear off his mask to join the sh—with fatal results. Cousteau
called this narcotic effect ‘rapture of the deep’. To complete the
picture, as the pressure increases the gases become so thick and
heavy that they are diicult to breathe.
_
The eminem British scientist, ]. B. S. Haldane, discovered many
years ago that raising the ambient pressure increases the oxygen—
carrying capacity of blood serum as opposed to the haemoglobin in
the corpuscles, the normal oxygen—carriers. This means that, volume
for volume, less oxygen is needed in air breathed under pressure.
.
Nevertheless the toxicity of pure oxygen supplies at pressures as low.
as two atmospheres has not been completely explained. Since the
_
amounts of oxygen in a breathing mixture can be reduced, this toxic
reaction does not present such a serious problem as the ill—effects
experienced from nitrogen—normally a physiologically inert gas.
_
After irtation with the idea that carbon dioxide accumulating in
the body under pressure might be the cause, most scientists have
come to the view that the nitrogen dissolves in the fatty surface
membranes of cells, including nerve cells, thereby slightly changing
their properties. Nitrogen is not the only inert gas to do this; it is
even possible to determine the likely effects of other gases being
considered for diving mixtures by their afnity with ‘fatty sub—
stances’.
»
-
By good fortune, one of the safest gases, helium, had already been
called into service largely because its lightness makes breathing
easier. The helium acts as a passive carrier for oxygen but, although
this inert gas does not react with the body’s tissues, the pressure still
forces it into them. The diver becomes the human equivalent of a
soda siphon with helium in place of Carbon dioxide. Release the
pressure abruptly by rapidly ascending from depth, and the gas
bubbles out of solution. Getting these bubbles in the wrong parts