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Asymptomatic Divers
Callers often ask DAN® if they should
administer oxygen to a diver who
reported a rapid ascent but has
no symptoms. There is no simple
or one-size-fits-all answer to this.
Factors to consider include the diver’s
decompression stress (missed mandatory
decompression, significantly deep or
long dives or many dives in a series) as
well as the true speed of the ascent and
the distance to definitive medical care.
Giving people oxygen is not harmful,
but providing it purely as a preventive
measure raises difficult questions about
how long to administer it, the goal of
treatment and in what circumstances a
medical evaluation is warranted. Consider
the available supply, and recognize that by
initiating oxygen administration you have
acknowledged that an incident has or is
likely to occur. The patient should not do
any more diving that day and should be
monitored for 24 hours. DAN is available
for consultation in these situations.
Use What You Have
Divers also ask DAN if they should set
the flow rate lower
than 10 to 15 liters
per minute to make a limited supply of
oxygen last longer. This is a reasonable
question, but remember why oxygen
therapy is used for divers: The goal is
to create a partial pressure gradient to
promote the elimination of inert gas
(
nitrogen). The way to achieve this goal
is to deliver the highest concentration of
oxygen possible. Therefore, the priority
should be to administer oxygen at the
maximum possible concentration until
you transfer care or supplies run out.
Oxygen Toxicity
From time to time DAN receives calls
from concerned dive buddies who are
hesitant to administer oxygen to a diver
who might have experienced CNS
oxygen toxicity at depth. However, once
a diver is on the surface, there is no
reason to withhold oxygen. Even if the
symptoms noted at depth were actually
the result of CNS toxicity, administering
oxygen is still recommended, and it will
not harm the diver.
Some people mistakenly believe that
if a diver is breathing oxygen from a
cylinder at surface pressure, air breaks
should be used to prevent CNS oxygen
toxicity. As well intentioned as that may
be, no air breaks are necessary; oxygen
should be provided without interruption.
Air breaks are employed during some
hyperbaric-chamber treatments to
minimize the risk of CNS toxicity.
However, such breaks are not necessary
for divers treated at the surface because
CNS toxicity is not a concern when the
maximum PO
2
is 1 ATA.
Breathing pure oxygen can irritate the
lungs (pulmonary oxygen toxicity), but
at sea level pulmonary toxicity (often
manifested by chest discomfort or a
burning sensation in the lungs) requires 12
to 16 hours of continuous therapy. While
this timeline may be shortened when the
PO
2
is greater than 1, such symptoms are
rare, and oxygen administration should
not be withheld or arbitrarily stopped in
an attempt to prevent symptoms that take
many hours to present.
Emergency oxygen administration
remains the cornerstone of treatment for
acute DCI. By keeping your oxygen unit
in good working order and practicing
deployment and administration
regularly, you will be prepared to provide
effective care. Remember, the person in
need may be you.
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PHOTOS THIS PAGE: STEPHEN FRINK