cardiovascular disease, especially those with weakened heart
muscle function, are less able to tolerate these physiologic
changes and are thus more prone to pulmonary edema. No
large studies have been performed, but review of the medical
literature shows several small case studies of patients with
IPE. In these, a high percentage of subjects had hypertension
or cardiovascular disease. Most of them also report a higher
proportion of women.
Alfred Bove:
There are several scenarios that provoke IPE. High-
intensity surface swimming causes it; this has been reported in
triathletes and U.S. Navy SEALs. Divers get IPE when swimming
on the bottom without clear evidence of stress. In some cases,
the diver relates a tight-breathing regulator, and in others no
evident stress or equipment problems are noted. In most cases,
cardiac evaluation is normal. Reduced diastolic relaxation (usually
a result of long-standing hypertension) can lead to increased
venous pressure in the lungs — the usual cause of pulmonary
edema from cardiac problems. Measurements of both systolic
and diastolic heart function can be readily obtained from an
echocardiogram. IPE is not a manifestation of decompression
sickness and does not require recompression. The treatment is
oxygen and diuretics to remove water from the lungs.
Pete Witucki:
We don’t know, and this is the dilemma.
There have been multiple proposed theories, but none seems
completely satisfactory. One theory suggests that prolonged
immersion in cold water causes peripheral blood vessels to
constrict and shunt blood to the heart and central circulation,
which then leads to fluid leaking into the lungs. However,
one would think that otherwise healthy individuals should
be able to compensate for this fluid shift. Not to mention,
IPE has been documented to occur in warm water. Another
theory, similar to the first, is that hydrostatic pressure
from the water causes blood to be shunted to the core. Yet
again, one would think this volume would not be enough to
overwhelm a young, healthy circulatory system. None of these
theories explains why IPE may occur in an individual during a
particular dive while other divers diving the same profile and
wearing the same thermal protection remain unaffected.
Yet another theory suggests IPE is the result of respiratory
mechanics. This idea is that a strong, forced inhalation against
resistance (essentially overbreathing a snorkel or regulator)
may cause the lungs to respond by leaking fluid out of the
capillaries and into the alveoli (pulmonary edema). This may
explain why young, healthy swimmers with strong lungs
may develop IPE especially during particularly strenuous
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