P
ulmonary edema is an abnormal leakage of fluid from
the bloodstream into the alveoli, the microscopic
air sacs in the lungs. It is most often the result of
heart failure or other cardiac problems. Sometimes,
however, pulmonary edema is observed in swimmers and divers
when no underlying medical cause is apparent. This condition,
immersion pulmonary edema (IPE), presents as a rapid onset
of shortness of breath, cough and sometimes blood-tinged,
frothy sputum. Because the fluid builds up in the air-containing
spaces of the lungs and interrupts gas exchange, IPE resembles
drowning. The important difference is that the obstructing fluid
comes from within the body rather than from inhalation of
surrounding water.
The DAN Medical Information department receives a few
calls each month in which divers report symptoms suggestive
of IPE. Anyone who experiences sudden shortness of breath
or persistent cough while diving should abort the dive in as
safe a manner as possible and breathe 100 percent oxygen
on the surface. Further diving should be postponed until
a physician can be consulted. Although IPE often resolves
quickly once a diver has exited the water, respiratory distress
in the diving environment can be extremely dangerous.
Why does IPE occur?
Douglas Ebersole:
IPE is an uncommon condition first
reported in 1989. It was originally described in cold-water
diving and called “cold-induced pulmonary edema.” However,
it has now been reported in warm-water diving as well. An
absence of chest pain helps differentiate IPE from pulmonary
decompression sickness (“chokes”). The exact mechanism is
not known, but it is thought to be due to a combination of the
increased hydrostatic pressure in the pulmonary capillaries
that occurs with immersion in water and the presence of a
gradient between the hydrostatic pressure at mouth level and
at chest level when a diver is upright. Additionally, diving
causes increased negative pressure in the alveoli due to denser
breathing gas and when using a poorly tuned regulator.
Immersion in water causes a number of physiologic effects
including a rapid distribution of blood from the legs to the
thorax, which can increase blood volume in the thorax by up
to 700 ml. This additional blood causes an increase in pressure
in the right atrium by 16-18 mm Hg, a 30-percent increase
in cardiac output and a slight increase in blood pressure.
Divers with conditions such as hypertension or underlying
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FALL 2011
Immersion Pulmonary Edema
RESEARCH, EDUCATION & MEDICINE
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E X P E R T O P I N I O N S
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