Posted on: February 27, 2014
Dive team members should be equipped with the
right protection for cold water diving. In most circumstances, this would
include a dry suit with insulating undergarments, dry gloves, a dry hood, and a
full-face mask.
In the real world of
public safety diving, there is no single definition of what constitutes “cold
water.” Defining cold water is difficult because it depends on so many factors,
i.e., the water temperature, the diver’s size, amount of subcutaneous fat,
state of acclimatization to cold water, individual physiology, and activity
level. What one person perceives as a comfortable water temperature may be
intolerable to another.
The real issue here is
at what point does exposure to cold water become debilitating? For the moment,
we’re assuming we’re talking about a diver who either is wearing inadequate
thermal protection, or whose thermal protection has been compromised, i.e. a
flooded dry suit. There is a continuum of responses to cold water that runs the
gamut from mild discomfort all the way to unconsciousness and death. As far as
I am concerned, the line is drawn at “debilitating effects” because once the
diver cannot perform at the peak of his ability, the risks in diving increase
to unacceptable levels.
Debilitating effects
range from loss of concentration to shivering and the inability to use one’s
hands properly. Any of these situations puts the diver at elevated risk and
indicate that the diver is not wearing adequate thermal protection for the task
at hand. If you notice these signs in yourself or another diver, it’s time to
terminate the dive and regroup.
When divers discuss
diving in cold water, the term “hypothermia” frequently comes up. Although we
all think we know what we mean when we discuss the issue of hypothermia, the
reality is that physiologists have a very different perspective on hypothermia
than most divers. For a physiologist, hypothermia is defined as a body core
temperature below 95 degrees F. Above this temperature, while you might be
uncomfortably cold, by definition, you are not hypothermic.
Dr. Neal Pollock,
Ph.D., Research Director for Divers Alert Network (DAN), points out that, “The
threshold core temperature for hypothermia is 35C (95F), a substantial drop. It
is unlikely that a diver with even modest protective garments will reach that
point. There is a big gulf between being cold and being hypothermic. Shivering
(episodic or continuous) and general impairment will develop long before the
definition of hypothermia is met. I think that the focus on the structure of
hypothermia stages (mild, moderate and severe) is unhelpful, confusing cold
impairment with hypothermia. You do not need both for serious problems to develop.”
Dr. Pollock knows that
of which he speaks, and has experienced a flooded dry suit during a polar dive
on a 43 minute excursion in 29 degree F seawater. Since he was wearing
Thinsulate® under his dry suit during the dive, he was able to continue the
dive, which was being conducted to measure his core temperature (don’t try this
at home!). The only reason he continued the dive was that it was being
conducted for the express purpose of measuring core temperature, otherwise this
type of occurrence would normally call for the dive to be aborted.
Interestingly enough, the largest drop in Dr. Pollock’s core temperature took
place after he exited the water.
True hypothermia is a
very serious condition and can lead to unconsciousness, cardiac arrhythmias
(irregular beat), and death. Clearly, these are scenarios that you don’t want
to occur underwater.
As mentioned earlier,
you don’t have to be hypothermic to place yourself at risk in cold water. A dry
suit (with insulating undergarments) alone is not adequate thermal protection
in cold water. Proper protection of the head and hands is equally important,
and dry hoods, full-face masks, and dry gloves are vital, especially for diving
under the ice. One issue that may occur with dry gloves and dry hoods are that
if they are compromised, their insulation value will be lost. Keep in mind that
every piece of equipment has its own advantages and disadvantages.
The language you use
as a public safety diver is important, since your actions may be scrutinized
and challenged in a court of law. In most cases, you will not be able to
properly diagnose a dive team member as hypothermic, unless you are using some
very sophisticated equipment. In any situation where you must describe a
diver’s inability to perform in cold water, it’s best to say that he suffered
from “cold stress.” Leave the medical diagnosis to the physiologists and
physicians.
About the author:
Steven M. Barsky is a professional diver, diving consultant and author. He has written 18 diving texts and and produced 9 diving DVDs. His latest DVD video, Careers in Diving, was released in December 2013.
Get in contact with Steve
Steven M. Barsky is a professional diver, diving consultant and author. He has written 18 diving texts and and produced 9 diving DVDs. His latest DVD video, Careers in Diving, was released in December 2013.
Get in contact with Steve
This
entry was posted in ERDI News.
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