contractile force increases accordingly to compensate, but
an abnormally high blood volume can overwhelm cardiac
function in some individuals. This leads to immersion
pulmonary edema (IPE), which can develop on the surface,
during a dive or immediately after surfacing. Essentially the
body’s own fluids accumulate in the lungs, causing acute
shortness of breath and potential loss of consciousness.
Depending on the severity of symptoms, the person
may require anything from supportive care to aggressive
intervention by medical professionals.
The potential complications of excessive hydration
outweigh any perceived benefit. Adequate hydration
is important, but there are no
data that demonstrate that divers
need to significantly increase
their fluid intake. Be skeptical of
bold proclamations, and do not
hesitate to ask for sources of such
recommendations.
—MartyMcCafferty, EMT-P, DMT
Q:
I will be testing
equipment in a series of
two 60-minute dives to
10 feet (3 meters) at an altitude
of 5,400 feet (1,646 m). The
following day I will ascend to a
maximum altitude of 11,570 feet
(3,527 m) for a skiing trip. Is it
safe to drive to a high altitude
after my dives?
A:
You get credit for thinking
in advance about the issue
of ascent to altitude after
diving. While easily forgotten
in dive planning, it can be a
significant problem depending on
the dive(s) and altitudes.
Generally speaking, it is best to avoid altitude exposure,
either through ground travel or flying, soon after diving.
The current DAN guidelines for flying after diving
recommend a minimum preflight surface interval of
12 hours after a single dive within no-decompression
limits, 18 hours after multiple dive days or multiple
sequential days of diving, and “substantially longer”
than 18 hours after decompression dives.
1
The exposure
altitude covered by these guidelines is between 2,000
and 8,000 feet (610 and 2,438 m). Altitude changes of
less than 2,000 feet are ignored in the belief that the
pressure change fits within the normal variability of
meteorological pressure. The majority of available data
do not address travel to altitudes greater than 8,000
feet, but it certainly represents a greater degree of
decompression stress.
The dive exposures you describe, however, are
modest enough that it is useful to refer to the U.S. Navy
altitude tables.
2
They were constructed mathematically
to consider specific dive profiles in the calculation of
altitude exposure limits. The U.S. Standard Atmosphere
3
describes the ambient pressure at 5,400 feet altitude as
12.05 psi. The “equivalent depth” (which is necessary
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