Cold Water Protection and Hypothermia

[redhawk]

From:
Whitewater Rescue Manual
By Charles Walbridge & Wayne A. Sundmacher Sr.

Cold-Water Protection (Pg 24-25)

Water draws heat from the body 25 times faster than air. Like windchill, the effects of cold water increase when the current is fast. Sudden immersion in snowmelt or spring runoff is extremely debilitating, causing a substantial loss of strength, coordination, and judgment rather quickly. All cold-weather paddlers should select the gear needed for the insulation required to stay warm.

Drysuits and wetsuits both work effectively in cold water. In a wetsuit, air is trapped inside the neoprene material, and the suit fits snugly enough to keep most cold water out. What little water gets inside is quickly warmed by the user's body heat. Drysuits create an actual barrier between the environment and the paddler, eliminating that initial “cold-water shock.” Paddling drysuits are made of a waterproof material with latex seals at the neck, wrists, and ankles. The paddler regulates the inside temperature by adding or removing layers of insulation, such as pile or polypropylene. In milder weather, a water-proof shell top or paddle jacket can be combined with pile clothing or a wetsuit for comfort.

The first goal is to protect the torso, which shelters the "core" of the body. The greatest heat loss occurs in the armpits and crotch. Next, pay special attention to the extremities. The head radiates a surprising amount of heat. If the helmet alone is not warm enough, pile or neoprene liners can be worn inside. Neoprene booties cover the paddler's feet, and if the sole is thick enough they can be used alone. Another alternative is to wear lightweight neoprene socks inside sneakers. In cold weather a boater's hands quickly lose the strength and sensitivity needed for effective paddling. Neoprene gloves or mittens are one answer; mittens are warmer than gloves, but more awkward and harder to find. Pogies (mittens that cover both the hand and the paddle) permit direct hand-to-paddle contact for maximum control with a kayak paddle. In borderline weather, carry hand protection along for possible use later in the day.

Hypothermia (Pg 129-130)

The human body functions only within a narrow temperature range. Warmth must be maintained to support the chemical and metabolic functions sustaining life. When the body cools below acceptable levels (hypothermia), there is a significant loss of strength, coordination, and alertness. Patients suffering from hypothermia may become unable to paddle effectively or to assist in their own rescue.
Paddlers must often contend with water that is dangerously cold. The effects are felt with surprising speed. Just like the effects of windchill, those of moving water produce an enhanced cooling effect that multiplies the impact of co!d water. But hypothermia does not always occur in cold weather. Unexpected summer storms can soak an unprepared boater, or the wind can steal heat from his body. An unprotected boater who takes a long swim on a cool, overcast day may find it hard to rewarm. An injured victim may experience hypothermia as shock sets in

Levels of Hypothermia
The human body has three layers; an outer superficial layer, an intermediate layer; and the inner core. The superficial layer consists of the skin and subcutaneous tissue; the intermediate layer is made up of the extremities, skeletal and muscular tissues, and some lesser organs; the inner core contains the most critical organs; the heart, lungs, and brain. When hypothermia sets in, the body prioritizes heat distribution. It works to keep the vital core warm, hoarding the additional calories required to heat parts of the body that are not necessary for survival,

As the body begins to chill, the first signs of hypothermia come in the form of muscle tension and goose bumps. This non-shivering heat generation can double the metabolic rate. As the core temperature continues to drop, shivering begins. These uncontrolled contractions can increase the metabolism to five times the normal rate. Now the body is burning roughly 400 calories per hour. That's approximately the number of calories in two Snickers candy bars. Under the right conditions, the body can still rewarn itself.

At some point, the body starts to realize it is beginning to lose its battle to heat all its layers and decides it can survive without the superficial one. By shunting the blood flow away from the skin and outer tissues, it reduces the flow by about I to 2 percent. Strenuous activity could increase heat output, but the body has limited stores of fuel. Heating the entire body might burn what reserves are left and leave the victim to cool even more quickly.

When core body temperature fails below 95°F, shivering diminishes. The patient may become confused; reasoning becomes clouded. With continued heat loss, the body decides to sacrifice parts of itself so that the brain can survive. By reducing the area being heated, life is prolonged. First, the body decides it doesn't need the extremities, and carbon dioxide and lactic acid build up in these areas. Then it begins to shut down blood flow to unnecessary organs. And finally, it will limit flow to the three organs that sustain life itself.

As the body continues to cool, the victim begins to lose touch with reality. In some cases. they experience atypical mood swings and may become argumentative or combative when assistance is offered. Once the core body temperature drops lo 90°F, shivering is replaced by muscle rigidity, and mental facilities are severely impaired. The victim is semiconscious, progressing toward unconsciousness. As the core temperature continues to drop, the metabolic rate diminishes, oxygen consumption drops, and respiration slows. Cardiac output also slows and weakens, resulting in further reduction in blood flow.

As lung and cardiac function diminish, cardiac arrhythmias develop, and ventricular fibrillation, a spasm of the heart muscle, eventually leads to cardiac arrest. A review of hypothermia symptoms follows:
Temperature above 95°F. Conscious and alert. Vigorous uncontrollable shivering, pain or numbness in extremities, loss of manual dexterity, slurring of speech.
90° to 95°F. Conscious. Mildly impaired mental facilities. Diminished shivering is replaced by muscle rigidity.
86° to 90°F. Semi- or fully unconscious. Severely impaired mental abilities; may appear intoxicated. Rigid muscles, cardiac arrhythmias.
80° to 86°F. Unresponsive, unconscious. Rigid muscles, dilated pupils barely responsive to light, diminishing or nonexistent pulse and respiration, blue-gray skin color.
80°F. Ventricular fibrillation, cardiac arrest. Pupils fixed and dilated. Death.

Loss of body heat occurs in a number of ways that may affect a paddler simultaneously:
Radiation: Heat is given off to a cooler environment directly. The amount lost to cold water is many times that of cold air.
Conduction: Heat passes out of the body directly into a cooler object, such as the ground an injured person is Iying on.
Convection: Heat rises away from the body into the air. Clothing helps prevent this.
Evaporation: Heat is removed from the body as water or perspiration evaporates and the skin dries. This is why wet clothing should be removed from hypothermia victims.
Respiration: Heat is continually lost as cold air is drawn into the lungs, warmed, and then exhaled.

[redhawk]

Dressing for Cold Water
From: http://www.rutabaga.com/index.asp


Dressing for Likelihood of Immersion

Cold-water paddling is a fact of life to us Midwesterners. Lake Superior is one of our favorite paddling destinations, and to make things clearer for ourselves and our customers, we categorize things loosely in three basic levels of protection:

Level I Protection

Level I protection is what we call "wet protection." This means that you will not stop water from contacting your body, but will warm the water next to your skin and keep evaporative cooling to a minimum once you are out of the water. This typically means a wet suit against the skin, which will trap water and warm it up.

There is also coated polarfleece, a newer product that offers slightly less protection that neoprene, but is more comfortable to wear in most conditions, especially when you won't be in the water too long. The coating is polyurethane, which is waterproof, but water still leaks in around the ankles and wrists, like a wetsuit. All in all, it's nice stuff. I think it's more comfortable than a wet suit, almost as warm, and is much easier to paddle in than a wet suit. It does cost more, however. While a wet suit farmer-T (full torso and leg coverage, but no arm coverage) costs about $95 or $100 dollars, a coated fleece wetsuit costs about $150, more for a full suit (which is practical in this material - very warm and comfortable).

A good piece to combine with a wet suit or fleece is a paddle jacket. Paddle jackets are made of waterproof material, but with leak-resistant (neoprene or lycra) rather than leak-proof (latex) cuffs and neck gasket. They do not provide as much resistance against immersions as dry clothing, but cost about half as much. Paddle jackets cost from about $50 to $90.

On top of that, neoprene booties work well to protect the feet and keep them warm as well. Wear a polypropylene liner sock if you want more warmth. Booties are about $25 to $40 dollars.


Level II Protection

Level II protection is a compromise. Do not think that all compromises are bad, however. This is a good one.

We define Level II protection as a semi-dry environment. What this means in a nutshell is that if you stay in your kayak, you will stay dry. If you have an Eskimo roll, then you're a good candidate for Level II protection. If you do come out of your boat, you will have essentially a Level I protection.

This level consists of replacing a Level I paddle jacket with a dry top with latex gaskets instead of neoprene. This is a watertight seal that will keep you dry even if you capsize and do an Eskimo roll or an Eskimo rescue.

Consider breathable fabrics if you are contemplating a dry top. Because it is impossible to ventilate a dry top through the neck and wrist gaskets, you are prone to moisture build-up, especially if you are paddling hard or paddling in warm weather with cold water (like Lake Superior in August; 80 degree air temperature, 40 degree water). It costs slightly more, but is worth it in the long run if you paddle in these conditions.

The other advantage of Level II protection is that you can expand to Level III protection with the addition of other pieces.


Level III Protection

This is the sine qua non of protection from the elements. If you paddle in bad weather, cold water, ocean surf environments, etc., you would want to have Level III protection to be safe and comfortable.

Level III protection is a dry technology. This means that even if fully immersed, you will still stay warm and dry. There is no moisture against your skin other than that which you produce. There are two ways to accomplish this.

One way is with a dry suit, which is a one-piece unit that has latex gaskets at the wrists, ankles, and neck. You would want appropriate insulation (fleece is a good choice) under your dry suit for warmth, as the suit itself provides only nominal insulation. Gore-Tex dry suits are expensive, but provide the best protection and breathability, a must in hot weather combined with cold water.

[redhawk]

Cold Water Immersion

by John Browning

Cold water is the leading cause of death among paddle sport enthusiasts. Exposure to cold water can bring on hypothermia, which can lead to death if not recognized and treated. However, hypothermia is not nearly as life threatening as is cold water immersion. Cold water kills!

I remember reading in an issue of the CASKA (Chicago Area Sea Kayaking Association) newsletter a few years ago about an incident that happened in mid-November. The air temperature was 38 degrees, water temperature in the low 40s. Wind was around 10 m.p.h., and the waves were in the three to four feet range. Two kayakers were out for a Saturday afternoon paddle, when one of them went over. By the time his friend was able to turn around and get to him, the effects of the cold water had already taken a dangerous grip on the "victim." He was unable to assemble his paddle float, so he was trying to climb back into his boat without it-to escape the cold water-not a chance. Although only 150 yards from shore, he was unable to make any progress swimming. As his friend tried to tow him to shore, he lost his grip on the stern. After a couple of attempts at the towing, they made enough headway that the victim was able to touch bottom and stand, although hunched over and unable to walk because of the cold. He was lucky to be alive. He did have a full recovery and now realizes that there is no such thing as a comfortable paddle near shore when you're not dressed for cold water immersion. (I have since learned that these paddlers had made a conscious decision not to wear their wetsuits, though they did have them on shore.)

So, if we do become immersed in cold water what can we expect? And how do we prevent these dangerous, and perhaps lethal, situations?

First, what do we mean by "cold water"? You may have heard the myth that if the sum of the water temperature and the air temperature equals 100 degrees Fahrenheit, then there's nothing to worry about. Right? WRONG!!! As an illustration of of how wrong this is, let's look at a spring time example . You're paddling on Lake Michigan, out in Whitefish Bay, the water temperature is 50 degrees and the air temperature is 75-it is a really nice day and there's not a lot of wind either. Let's see. . .50 plus 75 equals 125. On the mythical cold water scale you are OK since the sum of the air temperature and water temperature is greater than 100 degrees Fahrenheit. You reach around to get another water bottle off the deck just behind the cockpit. The bottle is secured under the bungee cord and as you give it a tug the bottle comes loose and flies out of your hands. You instinctively grab for it, reaching a bit too far and you roll over in your boat. Having draped your paddle across your lap, you don't have it to execute a roll. So you do a "wet exit". Since it is a fairly calm day and pretty warm by our standards, you did not put on a wet suit, or a dry suit. You did have the good sense to put on your PFD (personal flotation device, aka lifejacket), but besides your swim suit and spray skirt that's it. Our body's response to immersion into 50 degree water is something we don't have a lot of control over.

Breathing response. The shock of the cold water causes you to gasp-it literally takes your breath away! The cold water triggers involuntary gasps for air, followed by hyperventilation. Within fifteen seconds hyperventilation can reduce blood levels of carbon dioxide which leads to respiratory alkalosis, which can diminish blood flow to the brain, resulting in confusion, dizziness, and possible loss of consciousness. Hyperventilation can also cause tetany which is a tingling and numbness beginning in the hands and feet that can progressively develop into severe cramping in the extremities. Along with the hyperventilation, there is a claustrophobic feeling of not being able to get enough air (subjective dyspnea). This continues for up to three minutes before beginning to gradually decline, but increases the potential for panic and disorganized behavior in the water and makes hyperventilation even more difficult to control.

Hyperventilation increases the rate of breathing four to five times the normal resting level within 30 to 60 seconds of immersion. Research on cold water immersion finds that it takes up to 5 minutes for "relaxed" volunteers to stabilize their breathing at around two times the pre-immersion level. Since fear and panic aggravate the shock response, it is very likely that in real survival situations victims actually experience greater difficulty stabilizing their breathing than the research subjects did.

Another threat in cold water immersion situations is the reduction in the length of time that one's breath can be held. The ability of an average person to hold their breath in water colder than 60 degrees Fahrenheit is in the range of 15 to 25 seconds, approximately one-third of normal. It has been further reported that a person in water at 41 degrees Fahrenheit was reduced from 45 to 9.5 seconds. One subject's ability was reduced to 0.2 seconds! This obviously has an impact on one's ability to escape from a capsized boat in cold water.

Cardiac and circulatory response. Besides the loss of breathing control, immersion in cold water increases the heart rate, cardiac output, and blood pressure. The heart rate and blood pressure increase within several seconds of immersion. These changes place a considerable strain on the cardiovascular system and increase the risk of heart failure and stroke for people with high blood pressure, weak or damaged hearts, or weak blood vessels.

Skeletal and muscle response. Another response our bodies have to cold water immersion is the constriction of the blood vessels in the skin and skeletal muscles. This establishes an outer "shell" that cools more quickly than the "core" where our vital organs are. However, this results in a cooling of the muscles and the nerves controlling them, which leads to slower, weaker, poorly coordinated movements. The ability to swim or tread water is greatly impaired. The inability to continue swimming commonly occurs within ten to fifteen minutes after immersion in water colder than 50 degrees Fahrenheit.

Besides the effect on the ability to swim, immersion in cold water for more than ten minutes (five minutes in icy water) lessens our ability to climb onto a floating object or to catch and put on a PFD, or rescue device. And, to properly inflate, attach and use a paddle float. During the first 15 minutes of immersion, the initial effects are mainly a function of skin temperature as it rapidly cools to and stabilizes just above the water temperature. After approximately 15 minutes, the core temperature begins to drop which we call hypothermia. Immersion in cold water is associated with a high rate of heat transfer from skin to water, at least 100 times greater than in air of the same temperature. Thus the importance of dressing for the water temperature, not the air temperature. "Dressing for the water temperature", means wearing protective clothing to minimize heat transfer to the water. For cold air we put on multiple layers of clothing that trap air around our body and are thus insulative from the cold. When immersed in cold water, the water quickly replaces the warm air trapped in these multiple layers of clothing, unless we prevent water from reaching them by wearing a dry suit.




Dry suits are made of either waterproof coated nylon or nylon laminated with Gore-Tex. These are generally one piece garments with a large zipper running diagonally from the shoulder down to the waist. The openings at the neck, wrists and ankles are sealed with latex gaskets that prevent water from entering the suit. The zipper, being the largest opening, is extremely critical to the waterproof integrity of the dry suit. Dry suits are made to keep water out, protecting the insulative clothing from becoming wet and ineffective. While dry suits are expensive, if you plan on paddling in cold water, you should use one. Another note about drysuits, follow the manufacturer's care instructions, especially about using 303 Protectant on the latex gaskets and the proper care and storage of the zippers.

If you plan on paddling in water that is cool, as opposed to cold, (i.e., in the 50 to 65 degree Fahrenheit range) a wetsuit of either neoprene or polar fleece will do. Depending on the air temperature, wind and wave action (which has some bearing on how wet I'll get from the splashing and spray), I will use additional layers on my upper body for greater protection. Insulation layers, vary from wearing a short sleeve T-shirt made of the latest fibers (i.e., polyester, not yesterday's old stinky polypro)--which I am virtually never without--to a heavier fleece top. For water and wind protection, I wear either a short sleeve top made of Activentâ„¢ (an extremely breathable, water resistant material), or when I need full arm coverage, I put on a Gore-tex paddling jacket--complete with latex gaskets at the wrists.

As you can see, there are a number of medical/physical problems associated with cold water immersion. The speed at which these problems set in is quicker than one might imagine. How can they be avoided? First, have the proper equipment. Think of clothing as equipment in addition to a kayak that is properly outfitted with flotation, deck lines, and a well fitted cockpit, paddle, paddle float, bilge pump, PFD, emergency gear (flares, signal mirror, smoke signals, marker dye, fire starter, light, whistle, VHF radio,etc.), extra clothing in a drybag and a warm drink in a thermos.

Second, work to increase your skills-practice makes permanent. Remember, paddle skills include rescue skills. The tendency is to practice boat control and paddle strokes and forego the rescues outside a formal class setting. You should be able to effectively execute a rescue in the most extreme conditions you paddle in. Practicing in rougher conditions builds confidence in one's abilities, as well as confidence in the abilities of those you paddle with if you've been practicing with them. If you don't have "rough" conditions to practice in, add some "pressure" to the practice sessions by having someone time them. During our British Canoe Union 3 Star Proficiency Assessment in October, our assessor timed our rescues-from the time the victim's head hits the water to the time they are back in their boat, spray skirt attached and paddling again in under two minutes-practice also makes quick! I know that when I paddle with those from that assessment, I feel confident that if one of us capsizes, we'll know what to do and will be able to execute the rescue quickly. This is especially important when paddling in cold water.

Finally, there is no substitute for the exercise of good judgment. "Good judgment" means dressing for the water temperature not the air temperature. It means assessing the conditions-wind, waves, mood (yours)-and deciding whether you are prepared, given your equipment and your skill to use it, for the conditions you are facing. It means having the good sense to decide "not to do today, what can be put off until tomorrow." Sometimes this is difficult, especially when you're with a group and others want to move on. It may mean that you need to take a hard look at your paddling buddies. Are they macho types or otherwise psychologically/physically incapable of paddling in a group? If so, they aren't going to be close enough to help rescue you and you won't be able to get to them in time either. Some buddies! However, without the proper equipment, and the skill to use it, one must be strong and suggest that you "put off today, what can be done tomorrow."

"Good judgment" also means not paddling alone in conditions that may give rise to cold water immersion. And, it means that when paddling with a group that the group stays together, and that you use a "buddy system"-two or more paddlers paddling parallel to each other, close enough that an Eskimo rescue could be accomplished without undue delay. I had thought that the Eskimo rescue was not all that practical while "on the move", until the BCU 3 star assessment this past fall. While paddling along on an open water crossing, practicing leans and braces, one of my colleagues went over. Though we were on the move, I was there in under ten seconds presenting the bow of my boat for an Eskimo rescue. Providing the "victim" doesn't panic, hangs in their boat for a reasonable period, a lot of time and energy can be saved by the Eskimo rescue. Another reason to paddle close together in a pod is that in the worse case scenario an "unconscious paddler rescue" can be made. Remember, the shock of hitting the cold water can literally take your breath away, it can cause cardiac arrest, it can bring on a stroke, it can quite simply kill you!

Cold water paddling is not for the unprepared. I hope that I have given you some things to think about, as well as a better understanding of how quickly things can go from a nice time on the water to absolute disaster.