Q. When I attempt to go into the
outdoor pool at my beach club, I gasp for breath, get dizzy and
light-headed, and have to get out. Several years ago I read an
article that some people who are very sensitive to cold water may
sustain a heart attack from submersion into cold water. Is this a
A. Cold temperatures can have important
effects on your heart and circulation, so you're smart to be
cautious and get out of the water when you start feeling winded
Water conducts thermal energy 30 times more efficiently than air,
so taking a plunge into cold water is going to have a more
pronounced effect on body temperature than stepping out into air
that's the same temperature. Of course, we also tend to be less
covered when we swim, so we'll also lose more heat simply because
there's more skin exposed.
The body's normal response to cold, whether it's water or air, is
to go into a defensive posture and try to hold on to as much heat
as possible. Less heat gets lost to the cold water if there's
less warm blood circulating in your skin and through the parts of
the body with a lot of surface area, such as your fingers and
toes. So, blood gets shunted from the body's extremities to its
core (the trunk and head), and blood vessels in the skin clamp
down. Shivering, which creates body heat by cranking up
metabolism, usually kicks in at temperatures a couple of degrees
below those that put the circulatory system into heat-saving
The neurological signals that constrict blood vessels also have
cardiovascular effects. Blood pressure, heart rate, the amount of
blood pumped with each heartbeat — they all go up. The result can
be angina attacks from a heart that's working harder without
enough oxygen to meet its needs. Heart rhythm abnormalities can
also develop. Cold may also affect your breathing because cold
air may cause airways to constrict. Some people get full-blown
asthma attacks when they breathe in chilly air.
But there's another possibility that's unrelated to temperature.
Walking in water or swimming can be hard work that puts
additional strain on the heart. So there's a chance that the
symptoms you're experiencing are related to some kind of heart
problem that's apparent only when you are exerting yourself.
I'd let your doctor look you over, examine your
electrocardiogram, and see if there's any evidence of heart
disease. If you get a clean bill of health, then I'd conclude
that maybe you're just more sensitive to cold temperatures than
other people. I'd suggest that you continue to be appropriately
careful — and use common sense and get out of the water if you
feel any kind of discomfort at all.
— Thomas H. Lee, M.D.
Partners Healthcare System, Boston
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