Scuba Diving club,
Southern California
Sea Sabres
Nitrogen Narcosis
Air contains approximately
78% nitrogen, when it is compressed and breathed under pressure the elevated partial
pressure (Dalton's Law) of nitrogen can have a narcotic type effect.
Physiologically inert under normal conditions nitrogen can induce an anesthesia
effect at raised pressures. How this effect occurs, is comparable to the way
anesthesia gases operate, which is not clearly understood. All that is known is
that gases affect the central nervous system in unique ways. The effects of
nitrogen under pressure can be compared to the effects of alcohol. The
relationship of nitrogen to alcohol is expressed by what has been called Martini's Law. Simply put it is: that for
every 1 ATM or 33 feet the diver receives the effect of one martini. At 99 feet
the diver has the effect of 3 martinis and is typically unaware of reduced
ability. Like alcohol the diver is unconcerned about how impaired he is and it
is difficult to discern. Accomplishing such actions as figuring decompression,
or reading gauges can be hindered. Reflexes, needed for emergency action, will
be slowed.
MARTINI'S
LAW
33FT = 
66FT =
99FT =
132FT =
Martini's Law: For each 33 fsw the effect
is similar to one Martini
The effects of
nitrogen fluctuate from day to day and diver to diver. Ill health, hard work,
cold water, and being fatigue, all increase its effect. Most divers think of
nitrogen narcosis as a sudden ''freaking out'' by someone like giving a
regulator to a fish but this does not happen until a great depth is achieved.
Like drinking, you never feel drunk until it is to late. Sport divers should
not exceed 130 feet and watch for the effects of nitrogen at around 100 feet,
with the most serious symptoms below 150 feet.
One defense is to
recognize the signs and ascend when present. It is characterized by a slowing
of mental activity and a general feeling of euphoria. The greatest problem is
it can prevent the diver from feeling about his own safety.
Ascending alleviates
the effect but you may have to surface. When deep diving stay nearby your buddy in case one
of you acquire symptoms that may bring on harm. If encountering someone, grab
their arm, and signal up. If required, take him up with you by holding on to
his arm, and ascending. Never send a conscious diver to the surface by making
him positively buoyant. As pressure decreases, and air expands (Boyle's Law)
and his velocity of ascent will increase, to a conceivably uncontrolled rate.
Over expansion injuries can transpire. After bringing the victim up, give 100%
oxygen as needed. Training, preplanning, and declining dives greater than 100
to 130 feet can help avert narcosis.
Signs and Symptoms of Nitrogen Narcosis
Loss of judgment
False sense of well being
Lack of concern
Near unconsciousness at great depth
Unusual behavior
Panic
Stupor and/or coma
Posted April 5, 2003
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