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T
he most effective treatment for decompression
sickness (DCS) and arterial gas embolism
(AGE) caused by gas bubbles that occur after
decompression is the return of the patient
to an environment of increased pressure. This is called
recompression. Ideally a patient can be recompressed within
minutes of symptom onset — bubbles would be quickly
eliminated, and symptoms would resolve. This occurs
sometimes in commercial and military diving. However,
in recreational diving, even when a chamber is available
locally, it generally takes hours rather than minutes to begin
recompression treatment. If a hyperbaric chamber is not
available locally, which is often the case, recompression
may be delayed for days. For divers in remote locations,
the question of the impact of the length of delay to
recompression on their chances of a complete recovery is an
important one. In asking this question, it is also important
to explore steps that can be taken to mitigate risks. The
available data do not provide straightforward answers, so we
turn to experts for advice.
What determines the degree of emergency in DCS?
Dr. Jordi Desola:
The degree of emergency in cases of DCS
is determined by the severity of its presentation. Severe cases
involve several organ systems and may involve impaired
circulation, breathing and consciousness. Such cases can
result in permanent disability or death.
Dr. Karen Van Hoesen:
The following responses represent
the collective opinions of the University of California San
Diego (UCSD) Hyperbaric Medicine Center physicians.
These opinions are based on review of the literature and
our collective experience of treating divers with DCS for
more than 30 years. In general, the degree of emergency
in DCS is determined by 1) the time to onset of symptoms
following the dive, 2) cardiopulmonary instability and 3)
rapidly progressing neurologic symptoms. The quicker the
onset of neurologic symptoms after a dive (including motor
and cerebellar symptoms and mental status changes, but not
including sensory deficits alone), the more serious the DCS
insult. Any evidence of cardiopulmonary instability with
DCS is a true emergency. Neurologic symptoms that present
quickly and rapidly progress are also an indication of serious
DCS and should be considered an emergency. AGE with
neurologic symptoms is a true emergency and is excluded
from the responses that follow.
In your opinion, starting at six hours after symptom
onset, how much additional delay to recompression may
affect the outcome of DCS?
Van Hoesen:
Based on very limited case reports and data,
it appears there is a subset of moderate to severe DCS cases
where early treatment within six to 12 hours may improve
outcome. However, this subset of individuals with DCS
has not been clearly defined. The severe cases described
above may make up part of this subset. Regardless, there are
numerous cases of DCS that show improvement even with
significant delay to treatment beyond 24 hours.
Desola:
I have worked in Barcelona’s hyperbaric unit
for more than 30 years and have treated several hundred
DCS cases of various severities and with various delays
to treatment. In 1977 we started a prospective study to
explore what affects the outcome of treated DCS. The
first analysis of 466 cases, presented in 1997, showed
that delay in recompression was not significant. Three
years later and with more cases (554), a comprehensive
statistical analysis revealed that clinical findings are the
most important prognostic factors for DCS outcome. Our
findings were not very popular because they went against
current beliefs at that time. Since then, several reports
from reputable hyperbaric centers have confirmed them. A
recent retrospective study in the French navy found that 25
percent of divers with DCS had incomplete resolution after
one month despite a short delay to recompression (median
35 minutes). Longer delays apparently did not significantly
increase the risk of incomplete resolution. A critical factor in
good outcomes in severe DCS is the quality of the combined
treatment: drug therapy, aggressive rehydration, hyperbaric
oxygen therapy and critical care assistance inside the
chamber when necessary.
Might the effects of a delay to recompression affect
severe and mild DCS differently?
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WINTER 2012
Delay to Recompression
RESEARCH, EDUCATION & MEDICINE
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