and enables air trapped in the lungs to escape into
the pulmonary veins, which return oxygenated blood
to the heart. When this happens the escaped air can
enter the heart and traverse to the brain, where acute
neurological injury may occur. The speed with which
this happens explains the rapid onset of symptoms
following a dive — AGE occurs within minutes.
Pulmonary barotrauma can also manifest as free air
in the mediastinum (an area in the chest between the
lungs), which is known as pneumomediastinum, or
it may manifest as a pneumothorax (air in the chest
cavity outside the lungs). The greatest threat to divers
is an AGE that reaches the brain, a condition known as
cerebral arterial gas embolism (CAGE).
Symptoms of CAGE manifest at or near the surface
immediately after a dive, and approximately 50
percent of divers who suffer CAGE experience sudden
unconsciousness. Others may have acutely altered
mental status or loss of coordination or strength, which
are signs and symptoms of stroke and are the result
of restricted blood flow to parts of the brain. Those
who survive the initial injury may spontaneously revive
within minutes, showing varying degrees of neurological
injury or even a return to normal function.
Regardless of apparent normality, all victims of
pulmonary barotrauma, AGE or CAGE should
be evaluated urgently in a hospital emergency
department. Neurological symptom recurrence
is known to happen in patients with apparent
full recoveries. The consensus among hyperbaric
physicians is that anyone who shows signs of
neurological injury after a dive should be evaluated.
People diagnosed with AGE should receive hyperbaric
oxygen therapy (chamber treatment).
CT scans of the head are often part of these patients’
initial evaluation when they reach the emergency
department. It is important to assess the existence of
brain lesions or a stroke prior to initiating hyperbaric
chamber treatment — not because hyperbaric
treatment will worsen the condition but because
bleeding in the brain requires immediate surgical
intervention. Ruling out intracranial bleeds and blood
clots, which can also cause acute neurological injury,
is an important step; the absence of these factors
supports the diagnosis of diving-related AGE and the
use of hyperbaric oxygen therapy.
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From left: Although high bubble scores (as evalu-
ated by ultrasound) are not diagnostic of DCS,
they indicate considerable decompression stress
and are correlated with DCS symptoms. Multiplace
chambers enable accompaniment by medical staff,
which is important for seriously injured people.
STEPHEN FRINK
STEPHEN FRINK
