For the past 10 years or so we have been aware of an interesting and
worrisome problem that occurs in some divers while they are underwater.
The problem is the rapid development of severe shortness of breath caused
by fluid leaking from the bloodstream into the air spaces in the lungs,
and impairing the flow of oxygen into the blood. In medicine we call
this pulmonary edema. It is somewhat akin to drowning, but the fluid
comes from the body and not from the outside environment. A letter from
a diver describes the sensation:
"...I went down to the bottom, knelt in the sand and remained
still so as not to disturb the fish. I was in about 25 to 30 feet of
water for about 10 minutes or so when I started coughing into my regulator.
I noticed my breathing was a little fast for someone who was inactive.
Over the next five minutes or so, my coughing became more and more frequent.
I started to become a little concerned and signaled to my buddy that
I was going up. By the time I surfaced I was very short of breath. I
swam to the stern of the boat and just hung on to the ladder. I kept
coughing and coughing and coughing. ...I kept coughing up a lot of
secretions. I was having coughing fits. By the time we got back to the
dock, my coughing slowed up. The shortness of breath cleared up after
I was inactive and sitting for a few minutes. It was about five or six
hours before I felt totally normal. If I had to put a label on what
I was experiencing, it would be that of pulmonary edema. This episode
was the third and worst yet..."
This problem was described in 1990 at a scientific meeting of diving
medical physicians. The syndrome occurred in divers who were wearing
wetsuits in cold water. In the first report they were all over 50 years
old, and it was thought that these individuals had heart problems that
occurred for the first time while diving. However, subsequent reports
were published that included younger divers in warm water with no medical
history of any serious disease. Some of these individuals were taken
to hospitals and were found to have fluid scattered throughout the air
spaces of the lungs and inadequate oxygen in the blood.
This problem, called pulmonary edema, usually occurs because the heart
is injured or damaged, or because a process has occurred in the lung
to allow fluid to leak from the bloodstream and fill the air spaces
with plasma. The most serious and discomforting symptom is the rapid
onset of severe shortness of breath and coughing while diving. The diver
describes this well in the letter, which is a typical description.
Although immersion pulmonary edema is rare, it is certainly not trivial
and can cause significant problems with divers. The mechanism for it
is not well-understood, but some precautions are worth stating:
Although the cause for immersion pulmonary edema is unknown, these precautions can provide some protection. If you develop severe shortness of breath underwater, ascend at a normal rate to avoid lung overpressure. If your symptoms persist on the surface, breathe 100 percent oxygen if it is available. Consult your physician to be certain that your health is normal before returning to diving.
You can find more information on