Nitrogen Narcosis
Effects of Gas Pressure at Depth: Nitrogen Narcosis, CO and
CO2 Toxicity, Oxygen Toxicity, and "Shallow-Water
Blackout" WHAT HAPPENS TO GAS PRESSURES AT DEPTH?
Any gas taken to depth in a scuba tank will be unaffected as
long as it remains in the tank. Once it leaves the tank and
enters the diver's lungs it will have the same pressure as the
surrounding water, i.e., the ambient pressure. This statement
is
true for the two major components of compressed air
(nitrogen and oxygen), as well as for any gaseous impurities
(e.g., carbon monoxide).
WHAT IS NITROGEN NARCOSIS?
Nitrogen narcosis, also called "rapture of the deep" and "the
martini effect," results from a direct toxic effect of high
nitrogen pressure on nerve conduction. It is an alcohol-like
effect, a feeling often compared to drinking a martini on an
empty stomach: slightly giddy, woozy, a little off balance.
Nitrogen narcosis is a highly variable sensation but always
depth-related. Some divers experience no narcotic effect at
depths up to 130 fsw, whereas others feel some effect at
around
80 fsw. One thing is certain: once begun, the narcotic effect
increases with increasing depth. Each additional 50 feet depth
is said to feel like having another martini. The diver may feel
and act totally drunk. Underwater, of course, this sensation
can be deadly. Divers suffering nitrogen narcosis have been
observed taking the regulator out of their mouth and handing
it to a fish!
In The Silent World, Cousteau wrote about his early
experiences with the aqua-lung:
I am personally quite receptive to nitrogen rapture. I like it
and
fear it like doom. It destroys the instinct of life. Tough
individuals are not overcome as soon as neurasthenic persons
like me, but they have difficulty extricating themselves.
Intellectuals get drunk early and suffer acute attacks on all
the
senses, which demand hard fighting to overcome. When they
have beaten the foe, they recover quickly. The agreeable glow
of depth rapture resembles the giggle-party jags of the
nineteen-twenties when flappers and sheiks convened to sniff
nitrogen protoxide.
L'ivresse des grandes profoundeurs has one salient advantage
over alcohol no hangover. If one is able to escape from its
zone, the brain clears instantly and there are no horrors in the
morning. I cannot read accounts of a record dive without
wanting to ask the champion how drunk he was.
The effect, thought due to a slowing of nerve impulses from
inert gas under high pressure, is not unique to nitrogen; it can
occur from many gases (though not helium). The effect is
similar to what patients experience inhaling an anesthetic
such
as nitrous oxide (N2O). With increasing pressure of inhaled
N2O there is a progression of symptoms, from an initial
feeling of euphoria to drunkenness and finally to
unconsciousness.
Every year there are diving deaths attributed to nitrogen
narcosis, mainly among divers who exceed recreational depth
limits. To prevent the problem commercial divers switch to a
mixture of helium and oxygen (heliox) at depths exceeding
around 170 fsw. Helium is much less soluble in tissues than
nitrogen, and therefore is less likely to impair behavior (divers
using helium still have to decompress to prevent DCS). Even
setting aside the added cost and complexity, helium offers no
advantage for recreational divers over ordinary air.
Because of similar (and additive) effects to excess nitrogen,
alcohol should be avoided before any dive. A reasonable
recommendation is total abstinence at least 24 hours before
diving; by that time effects of alcohol should be gone.
Unlike the effects of alcohol, nitrogen narcosis dissipates
quickly, as soon as the diver ascends to a safe level (usually
less
than 60 feet depth). There is also some evidence that some
divers can become partially acclimated to the effects of excess
nitrogen; the more frequently they dive the less each
subsequent dive appears to affect them.
Effects of Gas Pressure at Depth: Nitrogen Narcosis, CO and
CO2 Toxicity, Oxygen Toxicity, and "Shallow-Water
Blackout" WHAT HAPPENS TO GAS PRESSURES AT DEPTH?
Any gas taken to depth in a scuba tank will be unaffected as
long as it remains in the tank. Once it leaves the tank and
enters the diver's lungs it will have the same pressure as the
surrounding water, i.e., the ambient pressure. This statement
is
true for the two major components of compressed air
(nitrogen and oxygen), as well as for any gaseous impurities
(e.g., carbon monoxide).
WHAT IS NITROGEN NARCOSIS?
Nitrogen narcosis, also called "rapture of the deep" and "the
martini effect," results from a direct toxic effect of high
nitrogen pressure on nerve conduction. It is an alcohol-like
effect, a feeling often compared to drinking a martini on an
empty stomach: slightly giddy, woozy, a little off balance.
Nitrogen narcosis is a highly variable sensation but always
depth-related. Some divers experience no narcotic effect at
depths up to 130 fsw, whereas others feel some effect at
around
80 fsw. One thing is certain: once begun, the narcotic effect
increases with increasing depth. Each additional 50 feet depth
is said to feel like having another martini. The diver may feel
and act totally drunk. Underwater, of course, this sensation
can be deadly. Divers suffering nitrogen narcosis have been
observed taking the regulator out of their mouth and handing
it to a fish!
In The Silent World, Cousteau wrote about his early
experiences with the aqua-lung:
I am personally quite receptive to nitrogen rapture. I like it
and
fear it like doom. It destroys the instinct of life. Tough
individuals are not overcome as soon as neurasthenic persons
like me, but they have difficulty extricating themselves.
Intellectuals get drunk early and suffer acute attacks on all
the
senses, which demand hard fighting to overcome. When they
have beaten the foe, they recover quickly. The agreeable glow
of depth rapture resembles the giggle-party jags of the
nineteen-twenties when flappers and sheiks convened to sniff
nitrogen protoxide.
L'ivresse des grandes profoundeurs has one salient advantage
over alcohol no hangover. If one is able to escape from its
zone, the brain clears instantly and there are no horrors in the
morning. I cannot read accounts of a record dive without
wanting to ask the champion how drunk he was.
The effect, thought due to a slowing of nerve impulses from
inert gas under high pressure, is not unique to nitrogen; it can
occur from many gases (though not helium). The effect is
similar to what patients experience inhaling an anesthetic
such
as nitrous oxide (N2O). With increasing pressure of inhaled
N2O there is a progression of symptoms, from an initial
feeling of euphoria to drunkenness and finally to
unconsciousness.
Every year there are diving deaths attributed to nitrogen
narcosis, mainly among divers who exceed recreational depth
limits. To prevent the problem commercial divers switch to a
mixture of helium and oxygen (heliox) at depths exceeding
around 170 fsw. Helium is much less soluble in tissues than
nitrogen, and therefore is less likely to impair behavior (divers
using helium still have to decompress to prevent DCS). Even
setting aside the added cost and complexity, helium offers no
advantage for recreational divers over ordinary air.
Because of similar (and additive) effects to excess nitrogen,
alcohol should be avoided before any dive. A reasonable
recommendation is total abstinence at least 24 hours before
diving; by that time effects of alcohol should be gone.
Unlike the effects of alcohol, nitrogen narcosis dissipates
quickly, as soon as the diver ascends to a safe level (usually
less
than 60 feet depth). There is also some evidence that some
divers can become partially acclimated to the effects of excess
nitrogen; the more frequently they dive the less each
subsequent dive appears to affect them.
Adventure Dominica
Nitrogen narcosis is a condition that occurs
in divers breathing compressed air. When
divers go below depths of approximately
100 ft, increase in the partial pressure of
nitrogen produces an altered mental state
similar to alcohol intoxication.
Description
Nitrogen narcosis, commonly referred to as
"rapture of the deep," typically becomes
noticeable at 100 ft underwater and is
incapacitating at 300 ft, causing stupor,
blindness, unconsciousness, and even death.
Nitrogen narcosis is also called "the martini
effect" because divers experience an effect
comparable to that from one martini on an
empty stomach for every 50 ft of depth
beyond the initial 100 ft.
Causes and symptoms
Nitrogen narcosis is caused by gases in the
body acting in a manner described by
Dalton's Law of partial pressures: the total
pressure of a gas mixture is equal to the
sum of the partial pressures of gases in the
mixture.
As the total gas pressure increases with
increasing dive depth, the partial pressure
of nitrogen increases and more nitrogen
becomes dissolved in the blood.
This high nitrogen concentration impairs
the conduction of nerve impulses and
mimics the effects of alcohol or narcotics.
Symptoms of nitrogen narcosis include:
wooziness; giddiness; euphoria;
disorientation; loss of balance; loss of
manual dexterity; slowing of reaction time;
fixation of ideas; and impairment of
complex reasoning. These effects are
exacerbated by cold, stress, and a rapid rate
of compression.
Diagnosis
A diagnosis must be made on
circumstantial evidence of atypical
behavior, taking into consideration the
depth of the dive and the rate of
compression. Nitrogen narcosis may be
differentiated from toxicity of oxygen,
carbon monoxide, or carbon dioxide by the
absence of such symptoms as headache,
seizure, and bluish color of the lips and nail
beds.
Treatment
The effects of nitrogen narcosis are totally
reversed as the gas pressure decreases.
They are typically gone by the time the
diver returns to a water depth of 60 ft.
Nitrogen narcosis has no hangover or
lasting effects requiring further treatment.
However, a doctor should be consulted
whenever a diver has lost consciousness.
Prognosis
When a diver returns to a safe depth, the
effects of nitrogen narcosis disappear
completely. Some evidence exists that
certain divers may become partially
acclimated to the effects of nitrogen
narcosis with frequency--the more often
they dive, the less the increased nitrogen
seems to affect them.
Prevention
Helium may be used as a substitute for
nitrogen to dilute oxygen for deep water
diving. It is colorless, odorless, tasteless,
and chemically inert. However, it is more
expensive than nitrogen and drains body
heat from a diver.
In diving with rapid compression, the
helium-oxygen mixture may produce
nausea, dizziness, and trembling, but these
adverse reactions are less severe than
nitrogen narcosis.
Nitrogen narcosis can be avoided by
limiting the depth of dives.
The risk of nitrogen narcosis may also be
minimized by following safe diving
practices, including proper equipment
maintenance, low work effort, proper
buoyancy, maintenance of visual cues, and
focused thinking. In addition, no alcohol
should be consumed within 24 hours of
diving.
Key Terms
Compressed air
Air that is held under pressure in a tank to
be breathed by underwater divers. A tank
of compressed air is part of a diver's scuba
(self-contained underwater breathing
apparatus) gear.
Compression
An increase in pressure from the
surrounding water that occurs with
increasing diving depth.
Partial pressure
The pressure exerted by one of the gases in
a mixture of gases.
The partial pressure of the gas is
proportional to its concentration in the
mixture. The total pressure of the gas
mixture is the sum of the partial pressures
of the gases in it (Dalton's Law) and as the
total pressure increases, each partial
pressure increases proportionally
in divers breathing compressed air. When
divers go below depths of approximately
100 ft, increase in the partial pressure of
nitrogen produces an altered mental state
similar to alcohol intoxication.
Description
Nitrogen narcosis, commonly referred to as
"rapture of the deep," typically becomes
noticeable at 100 ft underwater and is
incapacitating at 300 ft, causing stupor,
blindness, unconsciousness, and even death.
Nitrogen narcosis is also called "the martini
effect" because divers experience an effect
comparable to that from one martini on an
empty stomach for every 50 ft of depth
beyond the initial 100 ft.
Causes and symptoms
Nitrogen narcosis is caused by gases in the
body acting in a manner described by
Dalton's Law of partial pressures: the total
pressure of a gas mixture is equal to the
sum of the partial pressures of gases in the
mixture.
As the total gas pressure increases with
increasing dive depth, the partial pressure
of nitrogen increases and more nitrogen
becomes dissolved in the blood.
This high nitrogen concentration impairs
the conduction of nerve impulses and
mimics the effects of alcohol or narcotics.
Symptoms of nitrogen narcosis include:
wooziness; giddiness; euphoria;
disorientation; loss of balance; loss of
manual dexterity; slowing of reaction time;
fixation of ideas; and impairment of
complex reasoning. These effects are
exacerbated by cold, stress, and a rapid rate
of compression.
Diagnosis
A diagnosis must be made on
circumstantial evidence of atypical
behavior, taking into consideration the
depth of the dive and the rate of
compression. Nitrogen narcosis may be
differentiated from toxicity of oxygen,
carbon monoxide, or carbon dioxide by the
absence of such symptoms as headache,
seizure, and bluish color of the lips and nail
beds.
Treatment
The effects of nitrogen narcosis are totally
reversed as the gas pressure decreases.
They are typically gone by the time the
diver returns to a water depth of 60 ft.
Nitrogen narcosis has no hangover or
lasting effects requiring further treatment.
However, a doctor should be consulted
whenever a diver has lost consciousness.
Prognosis
When a diver returns to a safe depth, the
effects of nitrogen narcosis disappear
completely. Some evidence exists that
certain divers may become partially
acclimated to the effects of nitrogen
narcosis with frequency--the more often
they dive, the less the increased nitrogen
seems to affect them.
Prevention
Helium may be used as a substitute for
nitrogen to dilute oxygen for deep water
diving. It is colorless, odorless, tasteless,
and chemically inert. However, it is more
expensive than nitrogen and drains body
heat from a diver.
In diving with rapid compression, the
helium-oxygen mixture may produce
nausea, dizziness, and trembling, but these
adverse reactions are less severe than
nitrogen narcosis.
Nitrogen narcosis can be avoided by
limiting the depth of dives.
The risk of nitrogen narcosis may also be
minimized by following safe diving
practices, including proper equipment
maintenance, low work effort, proper
buoyancy, maintenance of visual cues, and
focused thinking. In addition, no alcohol
should be consumed within 24 hours of
diving.
Key Terms
Compressed air
Air that is held under pressure in a tank to
be breathed by underwater divers. A tank
of compressed air is part of a diver's scuba
(self-contained underwater breathing
apparatus) gear.
Compression
An increase in pressure from the
surrounding water that occurs with
increasing diving depth.
Partial pressure
The pressure exerted by one of the gases in
a mixture of gases.
The partial pressure of the gas is
proportional to its concentration in the
mixture. The total pressure of the gas
mixture is the sum of the partial pressures
of the gases in it (Dalton's Law) and as the
total pressure increases, each partial
pressure increases proportionally
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