Hypothermia: It’s All a Matter of Degrees

Full face mask diver in drysuit

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.

Ice Diving Training and Techniques – Straight from a Pro

Ice Hole Chain saw

As I write this article, I am comfortably sitting in my office in sunny South Florida. The weather is quite fair, around 75 degrees with a light wind, a few harmless clouds but mostly sunny. The water temperature recently has been in the mid to high 70F degree range; I consider a 5mm wetsuit to be adequate for my ventures. Diving other parts of the nation in mid February will have far different and most certainly more extreme conditions though, involving the much more technical aspects of scuba diving.

Freezing temperatures, blankets of snow, frozen water, and wind chill factors require a different type of dive plan. When I think of this type of training and diving (ice, rescue and technical training) the first name that comes to mind is Hank Woronka and all the guys over at Lake County Diver Supply out of Hobart, Indiana. Hank has been diving for over 50 years and ice diving in particular for over 34 years. When I had questions concerning diving these extreme environments, Hank would be the gentleman to answer them. I had the pleasure of speaking with him recently and inquire about some of the equipment requirements, planning, and execution for such intense diving and rescue training.

Of course, a great deal of training and education is required before attempting any sort of cold water dive and especially ice penetration, thermal conditions and over-head environments could pose a great threat to those inexperienced. This article will simply touch on some of the basics and techniques shared with me. Special considerations for equipment are a crucial topic when dealing with extreme climates. Exposure suits, full face masks, and thermal gear are all of course vital instruments to take into consideration. Every piece of equipment must be designed with special regard when the surrounding environment is at literally freezing temperatures. In particular, first stages, regulators, primaries, secondaries, inflation hoses, gauges etc. must be able to withstand freezing temperatures to prevent malfunction.

Training for buoyancy control, harness, weights and ropes, communication techniques and equipment malfunction or freezing is also advised when diving and especially in the mentioned environments. Ice conditions are also a critical variable: ice forms, depth of ice, and site preparation all account for performing a successful operation. When cutting (with the use of an ice saw or chain saw) into the ice when deemed acceptable conditions, a 6x6ft triangle is cut to allow easier entry and extraction from the ice hole. The closer angles of a triangle shape allow the diver greater capability hoisting him or herself (with help from the tender) out of the ice hole and onto the solid ice surface. Every aspect of diving must be scrutinized and carefully adjusted for these sub-zero conditions, there is truly little to no room for error. The effort and training for ice diving is truly astonishing.

Hank recounted from over the years countless victims, cars, and evidence retrievals from frozen lakes and ponds. The importance of proper ice training is significant for everyone and everything involved. It has become a crucial aspect of scuba diving worldwide, whether it is for recreation or for rescue/recovery attempts. He mentioned in our conversation that ice diving and rescue/recovery is a huge process, one that consists of a well prepared and well trained team. Each member performing a task for the overall safety of everyone involved. Working as a team in this type of environment is essential for the overall success of the dives. Ice diving is a true test against the elements; success is accomplished by those who are willing to put the time and effort into learning such a technical aspect of the field.

Iceberg Scuba Diving

Diving 10,000 Year Old Ice

There is a very old dive site that has just been floating around waiting to be discovered…

Iceberg Scuba DivingAsk the average scuba diver what they think of when someone mentions ice diving and chances are good they’ll tell you about diving under the winter ice cover of a freshwater lake. But did you know you can dive ice in the summer too?

Every year it is estimated that as many as 50,000 icebergs calve off the glaciers of Greenland to start their long journey south driven by ocean currents. A few hundred travel down the North Atlantic coast of America and make it as far as the island province of Newfoundland. The most famous got in the way of the Titanic 100 years ago (April 1912); and the stream of berg’s since that historic collision has grown stronger in recent years thanks to global climate change.

The process of carving goes on year-round but the best time to see Newfoundland (or Atlantic) icebergs “in person” is in the summer, and one of the best places to find ones that are “safe” to dive is Conception Bay, near that Canadian province’s capital city of St. John’s.

“Safe” of course is an entirely relative term in all types of diving but most certainly in this particular flavor of adventure-diving. An iceberg is a dynamic entity; constantly moving, shifting, stressing and straining. Rolling and splitting are two of the constant threats presented by a huge chunk of frozen fresh water floating in a slightly warmer flow of salt water – and gradually melting away. Of course, these events can be disastrous for anyone close by, whether on the surface or underwater. Because of this and other factors, diveable bergs are bergs that are grounded. These are sometimes called Ice Islands.

Iceberg ScubaGrounding? Let me explain. There is no such thing as an average Newfoundland iceberg. Some are the size of a football stadium, and some look as small as a garden shed (see table), but what they all share is that approximately ninety percent of their bulk is “hidden” underwater. What we see floating is just the tip of the iceberg (sorry; couldn’t resist the pun). As air temperatures effect it – making it melt and crack due to changes in surface temperatures and internal pressure – a free-floating berg is always at risk of turning over or calving off mini-bergs of its own.

You might say that the berg is constantly changing its buoyancy and trim! Only when that hidden portion of the berg bottoms out on the ocean floor is there ANY opportunity to partially manage these risks.

However, few icebergs are held fast for long. As their bulk and mass gradually lessens, buoyancy changes and ever-present currents and tides will tend to push it along, often dragging its way through the seabed. Many berg divers check out this Ice Scour or Gouging – given depth limits – before getting close to the body of the berg. This is an indication of how long the berg has been grounded, and in some part, how it has behaved during its time as an ice island. Also, since the seabed in Newfoundland is home to all manners of cold-water creatures, the gouge often uncovers hidden critters and can attract larger predators to an open feast — take a camera!

Once a berg is confirmed to be grounded, divers usually submerge at a safe distance and swim toward the iceberg. This is one of the most unique experiences. Remember, an iceberg is fresh-water, perhaps more than 10,000 years old. It is pure and unsullied by mankind. As a diver closes in on its walls – which incidentally have the appearance of a multi-hued abstract sculpture – she will pass through the meltwater zone, where seawater and freshwater mix. Her buoyancy will change and she will experience passing through a distinct halocline. Also, the quality of sunlight or daylight will change, and it is not unusual for the visibility around a berg to be “virtually limitless.” The ice itself seems to glow from transmitted sunlight and the berg’s walls will shimmer with countless shades of blue from pale aqua to deep violet.

It will be, all in all, an unforgettable experience.

Size Category Height Length
Growler Less than 1 metre (3.3 ft) Less than 5 metres (16 ft)
Bergy Bit 1–5 metres (3.3–16 ft) 5–15 metres (16–49 ft)
Small 5–15 metres (16–49 ft) 15–60 metres (49–200 ft)
Medium 15–45 metres (49–148 ft) 60–120 metres (200–390 ft)
Large 45–75 metres (148–246 ft) 120–200 metres (390–660 ft)
Very Large Over 75 metres (246 ft) Over 200 metres (660 ft)

Data supplied by International Ice Patrol

Iceberg Diving

SOMETHING TO THINK ABOUT

Often an iceberg will be surrounded by small chunks of calved ice (Growlers or smaller). If possible, collect one or two of these and use them in your cold drinks (in Newfoundland, this might be an after dive drink of Screech). When berg ice melts, it makes a fizzing sound called “Bergie Seltzer.” This sound is caused by escaping air originally trapped and then compressed as prehistoric snow layers became glacial ice.

WHO IS ICEBERG DIVING FOR?

Iceberg diving is great for advanced divers, equipped and experienced in cold-water diving since even in summer, the water temperatures at depth in Newfoundland hover only a few degrees above freezing. Divers with a sense of adventure and a yen for something out of the ordinary are also recommended.

There are several SDI/TDI instructors working in Newfoundland; to find out more about adventure diving, contact them through our website https://www.tdisdi.com or call us 207.729.4201

REMEMBER no dives outside your comfort and training should be undertaken without proper instruction and guaidance!