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It’s cold out there. During this time of year, people generally spend more time inside than out, which is understandable. Regular outdoor activities don’t sound nearly as appealing when it’s below freezing outside. While this is true for some in the ITS community, I know that the vast majority of you are spending time in the outdoors despite the chill. We are outdoor people by nature and the winter provides a great environment for fun and adventure.
Although winter sports and trails offer a fantastic escape from suburban reality, they also bring with them many dangers due to the elements. The cold is a very real threat, but it’s one that can be fought and beaten with solid education. It’s our responsibility to learn the dangers of the environment and how to overcome them. This comes by gaining a good foundation of knowledge that can be built upon with time and experience.
I’m reminded of the movie The Edge where a wealthy genius is given a book on surviving the wilderness days before his plane crashes, leaving him stranded in the wild. With the limited amount of knowledge he’d received from reading the book he was able to fight off predators, keep warm and eventually survive until rescued. Although this was a fictional tale, it does demonstrate the power of knowledge in a survival situation. Perhaps it’s best to view the cold wilderness as an enemy to overcome and we should show that enemy the respect it deserves by learning what we can, when we can.
When the temperature drops inside of your body, the effects immediately evident. The body has a natural defense against a loss in core temperature, such as peripheral vasoconstriction that could lead to cold diuresis and shivering, which can cause lactic acid to build up in the muscles. Below is a list of the symptoms associated with a drop in core temp:
- 98.6 °F – Normal operation
- 97.0 °F – Mental impairment; poor judgment
- 96.0 °F – Onset of shivering; increased metabolism
- 94.0 °F – Gross motor skill impairment leading to stumbling and increased shivering; no self protection
- 92.0 °F – Difficulty walking; severe shivering
- 90.0 °F – On ground with convulsive shivering
- 86.0 °F – Shivering stops; coma; curtains
I do have a deep appreciation for the cold and its powerful effect on the mind and body. In my past, I’ve seen enough to understand the danger of losing body heat. It was on Tuesday night of Hell Week when I was called out from the rest of the class and told that I needed to have my temperature taken, but they weren’t about to ask me to open my mouth and put a thermometer under my tongue. No, they had bigger and better plans for me. In Hell Week, they use a long thermometer that is inserted where the sun don’t shine with a “way too long” lead that takes the temperature of your vital organs, not your extremities. The instructor actually apologized to me before taking my temperature. I’ve always found that funny. I’m glad that this happened though, because I have a recorded 93 °F on record. Had this been taken under the tongue it would have appeared lower, but the core is what matters.
I remember how I felt that night and can honestly say that I have been colder in the Teams. I had the “opportunity” to dive a lot and sometimes this involved cold water. In the Pacific Northwest, I dove an exhaustion dive on mixed gas in 35 °F water that lasted, not kidding, almost ten hours. I know that sounds like an exaggeration, but it’s actually quite generous. I can’t get into the specifics, but I can say that I was wearing a 3-2-1 wetsuit under a 6.4 semi-dry suit. My dive buddy wore a bare dry suit because he didn’t require the dexterity I did for this training operation. By the end, neither of us could walk under our own power. With help though, we drove back to the dive shop and rewarmed in a hot tub for an hour. I’m not saying we needed the hour, but it did make the beer go down smoother. That was the coldest that I’ve ever been. Had we needed to rewarm ourselves on the beach without help, I don’t know what would have come of it.
Note: Wind and Wetness take away body heat faster than it can be produced.
The state when the body core temperature falls to 95 °F or below. This is a life threatening, non-freezing, cold injury.
What causes Hypothermia?
- Ambient temperature
- Wind chill
- Wet or inadequate type or amount of clothing
- Water immersion
- Poor nutrition
- Decrease in physical activity
Prevent further heat loss by getting the person out of the elements. They’re a CPR risk and you should monitor ABC’s [Airway, Breathing and Circulation] constantly while observing and evaluating. Remove wet clothing and add external heat such as insulating clothing and sleeping bags. Wrap the person like a burrito in a vapor barrier and heat retention layer if possible. Feed them warm, sweet, high-calorie liquids.
Note: No one is DEAD until they are warm and DEAD.
This is a non-freezing injury that’s uncomfortable, but causes no impairment. Caused by repeated exposure of bare skin to wet windy conditions at temperatures ABOVE freezing. It looks white and red and it causes the area to itch. It also causes the skin to become rough and it will begin to crack. Chilblains are avoidable by using the appropriate gear for the weather situation at the time.
Many people don’t understand that frostbite is the actual freezing of the living tissue in the affected cells. It happens much quicker when a person is dehydrated, at higher elevation, or has had previous cold injuries. Tight fitting clothing doesn’t help either, because it restricts blood from warming the area. Frostbite can occur suddenly when uncovered skin has direct contact with extremely cold metals and liquids. Not many of you are going to like this, but three things that can have a negative impact on your body’s ability to fight frostbite are caffeine, tobacco and alcohol because they’re vasoconstrictors. Sorry to be the bearer of bad news.
The truth of the matter is that frostbite is usually the direct result of neglect. There are several symptoms that can serve as an early warning and if you know what to look for, you may be able to reverse the effects of the cold before it’s too late. The first sign that the cold is beginning to affect your body at the cellular level, is a burning pain in the area. This pain may actually go away as the skin turns from red to yellow. Your skin is the easiest way to know something is going on because the color indicates the activity of the tissue. After yellowing, the skin will go pale and eventually purple. The skin will begin to feel waxy and hard as if frozen, literally.
Superficial – If you have seen the early warning signs and decided to treat the issue quick enough, there’s hope. You can rewarm your body by finding shelter and staying dry and warm. Any method of rewarming your body temperature should be considered at this point. Whether starting a fire or using skin-to-skin contact, you may have less time then you think, so act quickly.
Deep – If it gets this bad, then you may require aid. When approaching a frostbite victim, make sure to carefully assess the situation and the patient. If he or she has any constricting clothing, remove it. The frozen extremity should be rewarmed rapidly by immersion in water between 100 to 108 °F for 30 to 60 minutes. If it’s the lower extremities that are affected, then treat them as litter cases. If necessary, give the patient pain medication while ensuring their body warmth is maintained.
Prevention – As mentioned above, avoid constricting clothing. Train and acclimate to whatever climate you are in before pushing your limits because you may not know what your limits are yet. Use lip balm (non-petroleum based) on your nose and ears to help protect the tissue. I’ll end this portion on frostbite by stressing the most important thing you can do to prevent it; keep your clothing and socks as dry as possible.
Knowledge is Power: Mechanisms of Heat Exchange
Radiation – The movement of heat rays from a warm object to a colder object. Heat is always moving. This is non negotiable, but if you know how it works then you can make the transfer of energy work for you.
Convection – The movement of air (wind) across an object. Wind is the cold’s little scoundrel of a buddy. It will literally rip the warmth right off of you. This is why layering is constantly reinforced. If you’re wearing more material than you should for your level of physical output, you’ll get wet from the inside out. The second you pull your heavy jacket off and the wind hits the wet clothing underneath, your body temperature will plummet. I have heard this referred to as “flash off”.
Conduction – Heat loss by touching a cold object (bare rock, ice, sitting in snow, water, etc.). If you sit on a cold rock, your pants and butt become cold, the rock doesn’t become warm. A practical application of this knowledge would be to always create space between you and the ground if you need to sleep. This can be done with a cot or ground pad in a camping scenario or with pine branches and moss in a survival situation. Either way the science is the same.
Evaporation – The evaporation of perspiration causes heat loss. Proper ventilation will aid in reducing perspiration, which will keep your clothes dry. Wearing a base layer is key because the moisture will work into your second layer. Remember, as long as your base layer is dry, you are dry.
Respiration – Breathing cold air can significantly affect body temperature. Heat escapes when warm air is exhaled. While it sounds like there is little to be done here, it’s actually quite the opposite. Anyone who’s been at serious altitude can attest to how humbling it can be. The better physical condition you’re in, the less O2 your body will need to function at higher levels of intensity. That being said, you will still need time to acclimate in order to function optimally, regardless of your stamina.
Hopefully this knowledge never proves too useful. Either way, it sure does feel good to be a little more prepared.
Editor-in-Chief’s Note: Nick recently left the Navy after serving for 10 years as a Navy SEAL with multiple deployments, having been awarded the Bronze star for operations in austere environments. Nick’s been with us since the beginning here at ITS on our Advisory Board and I’m thrilled to officially have him aboard as a contributor.
Title photo © Vincent Lock
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This article illustrates why doctors and medics insist that 'you're not dead until you're warm and dead."
Note this quote:
When the crew touched down at Tromso University Hospital, Anna’s heart had not beaten for at least two hours. Her core temperature was measured at 56.7 degrees Fahrenheit—42 degrees below her normal core, and lower at that point than any surviving patient in recorded medical history. This was genuine terra incognita. Any attempt to resuscitate Anna further could only proceed in the knowledge that in similar situations past medical teams had always failed.
Great article! I'll preface this as I work in the field of human thermal systems, clothing, and equipment. I laughed pretty hard when you talked about the rectal probe. People HATE the idea of that thing. For everyone else's schadenfreude, the standard depth is 10 to 15 cm (4" to 6") to get a good reading. In practice, it apparently isn't too bad. At least they used the correct end of the probe... We try and use the pills now when we can, just so we can get volunteers (we have to fully inform subjects of what's going to happen, and the general response is "you want to put what, where!?"). I wonder if they've started to use the pills in training as they're easy to monitor in real time. They are pricey though and are non MRI compatible, which could be an issue with high-risk training. Your average Olympic hopeful puts up with much worse in terms of invasive procedure and a probe "where the sun don't shine" is mild by comparison. Glad to hear they're monitoring core temps in training now, but I didn't expect anything less.
I feel I should add some. One is trying to plan ventilation to the layers. This is something that takes some time to figure out. When you feel yourself starting to sweat, unzip, unbutton, and cool off a bit. I know this might seem weird, but you have to get rid of that water especially if you're moving and being active. When I ski, I usually have my coat open on the way down and closed on the way up when I'm stationary. This also depends highly on the textile you're using. Vapor permeable membranes don't breathe that well, so just because it says it is 'waterproof/breathable' doesn't mean that it will magically get rid of your sweat. Its better than impermeable, generally but people sweat when active much faster than can be passed through the membrane. Wool and some synthetics will allow you to retain heat when wet (it is still compromised to some extent by the conduction through the water. I'm a big fan of merino wool, personally, for cold and warm (different weights and weaves) as a base layer. It is expensive, but wool retains heat when wet and has other properties such as being odor resistant and naturally FR (for those who need it, I don't). Things like down are useless when wet as it will clump and loose loft. There is "Dry Down" now but I don't know the specs on it offhand, and it is pretty new. Either way, you're generally going for "loft" and "layers" in trying to stay warm.
Socks, one of the best ones quotes from Band of Brothers: "You need four Minimum: "Feet, Hands, Neck, Balls, extra socks warms them all". In reality, if you're well equipped, two to three pairs is great if you're going to be outside for long periods, wear one, dry one. Buy quality. If your feet go down you're in a world of hurt. Been there, done that, never again. Nick touched on this "tight can be the enemy". Don't get tight warm socks. You're going for loft, like that fluffy coat. If your boots for the cold are too tight to fit warm socks, you might need new ones. Also when you stick your feet in your boots, you don't want your socks pulled tight across your toes! This also goes for gloves as well, not too tight.
Yes, yes, and kind of: "three things that can have a negative impact on your body’s ability to fight frostbite are caffeine, tobacco and alcohol because they’re vasoconstrictors." Caffeine and tobacco, yes. Alcohol is a constrictor on the rebound. To explain, alcohol is actually a temporary vasodilator. The after effect of alcohol can be as a vasoconstrictor, especially if you drank a lot. This occurs partially as the body tries to filter out the alcohol. Part of this is also because alcohol is a diuretic (dehydrates). The image of the St. Bernard with the barrel of whiskey is an icon for a reason, because alcohol makes you 'feel' warm by increasing capillary size (vasodilation). Anyone who has had a stiff drink knows how you feel warm and your face gets red, etc. These are symptoms of vasodilatation. In some cases Alcohol could be used to increase dexterity (I am in no way advocating this because it can be dangerous) in the cold by providing extra blood to the skin for a temporary period of time. However, this increases heat loss to the environment, and can lead to the rebound effect of possibly vasoconstricting hands/feet and making it worse. Especially if your core temperature drops while feeling warm when drinking alcohol (which also decreases your cognitive ability and you might not know you're actually getting colder). Granted this method was used by our ancestors who had to take off their mittens to do fine work in the cold. It is all about heat management.
Finally, bring food as well as water. This is fuel for your body and what you are using to create heat. High calorie foods are necessary as you burn more calories in the cold as your body tries to stay warm. Shivering is increasing your metabolic rate. If you can't fuel shivering, your core will sink faster. Complex and simple carbs are key here. That's why Nick talked about "warm, sweet, high calorie liquids". Offhand, I seem to recall it takes about/at least 5000 calories a day to sustain a typical soldier in cold weather operations. We're are different so it may take more or less for you, but the standard daily intake is supposed to be 2000 calories.
"Not many of you are going to like this, but three things that can have a negative impact on your body’s ability to fight frostbite are caffeine, tobacco and alcohol because they’re vasoconstrictors. Sorry to be the bearer of bad news."
Also important to remember how it can happen anywhere, not just out in the rough field. Here in Ohio the news of the day is a college student missing for 24 hours in a tiny college town. He'd stumbled out of a bar at 2:00 AM (purportedly--that's the tone in the news reports), and walked the wrong way, and then passed out. Then he died of exposure. Oh, and he wasn't wearing any winter clothing. It was close to zero Friday night. Professors out helping in the search found him.
There was a technique I used when mountain climbing and winter skiing to test if I was getting into the early mental and motor impairment stage of hypothermia. I'd hold my arms part of the way out and see if I could bring my finger tips together quickly. It's unambiguous, either you can or can't. When it happens, it'd be good to have a rule to take action immediately.
1. Drink a warm, sweet drink or eat high-calorie foods.
2. Put on more clothing, particularly covering the head where a lot of heat is lost.
3. Get out of a wet environment and/or change into dry clothing.
4. Check for frostbite, particularly the hands, feet and face. Touch and see if you can feel that touch.
Remember, the later stages of impairment affect your ability to see you have a problem. Even if you're with others, they may be so focused on themselves they don't notice what is happening to you. Have 'if this happens I do this' rules and stick with them no matter what.
I suspect the technique also work with other ills, including heat stroke, dehydration and low-blood sugar.
Years ago, when I worked in a hospital caring for kids with leukemia, I soon learned to watch their mental state very carefully. Our brains are very sensitive to our body status. Becoming groggy and unaware of surroundings often means something serious is wrong. That's why medics will ask simple questions like, "What day is this?"
I never got into hypothermia while climbing. The effort kept me warm. But on one climb, despite my efforts to eat and drink, I did hallucinate, in one case seeing a hot-dog stand high up on Mount Rainier. I actually had an argument with myself:
"That can't be real. It wasn't there when we passed through this morning on the way up."
"Well, maybe they flew it up under a big military helicopter."
"Naw, that doesn't make sense. Why would they do that?"
By that point I was close enough to see that hot-dog stand wasn't one. It was sheer wish fulfillment. I'd eaten all my food and was still several hours from the parking lot. Low blood sugar probably. I'd gone up about 10,000 feet and down about 6,000 feet since the evening before. I'd burned a lot of calories.
--Michael W. Perry, My Nights with Leukemia: Caring for Children with Cancer
Excellent post! Loved the gauge at the beginning showing how weak we really are. 1.6 degree fall in temp and we start making some sketchy decisions. Thanks for sharing. Really good info here.
Would love to get more collaboration going on this if anyone wants to share, or comment.
Fantastic post. I have one on the forums as well. Thats focused on tough decision making when dealing with frostbite. Really liked the temp gauge at the top. Shows you how weak we really are 1.6 degree change and we are already making poor decisions.
A couple of things to add:
Be very very careful when transporting a hypothermic patient, as they are very susceptible to v-fib.
Also, adequate hydration is critical during cold-weather activities. Everyone thinks about staying hydrated in hot weather, but not so much in cold, though you lose a surprising amount of fluid by evaporation and respiration even in cold conditions. Dehydration thickens the blood, which means it can't flow as easily to extremities, leading to greater risk of frostbite. And drinking warm fluids (if possible) warms the core, reducing the risk of hypothermia.
I'll add more details about frostbite. Once an extremity like a foot is frozen, the harm is done. As long as the frozen area doesn't spread, merely delaying treatment won't make their condition that much worse. What's frozen is frozen.
In a sense, it's one of those unpleasant choices like applying a tourniquet. What needs to be done in a combat or wilderness survival situation may be different from what is done in a hospital. It may be far from ideal.
Typically, it's the feet that are frozen. If there's no way to transport the victim to medical care, meaning that the person must walk, perhaps assisted by others, then it's better that they walk on frozen feet. Some harm is likely to result, but it'll be far less than if they're forced to walk on rewarmed feet. The pain may make that impossible anyway.
Also keep in mind that for someone who is immobilized and transported in a cold environment (i.e. on a snowmobile) their warmed up extremities can easily refreeze, making matter far worse. It may be better to delay that rewarming, while keeping it from spreading, until a warm environment is assured. Being frozen is also a crude sort of painkiller, so it's likely to be best to delay rewarming until painkillers can be given in a medical environment. That's why even frozen hands might be best left frozen and merely immobilized and protected from additional injury. Don't underestimate what severe pain can do to someone's ability to get out of a wilderness situation.
Here's a website with more details:
Note especially this: "If frostbite occurs far from help, it may be unwise to thaw out the affected areas in case they refreeze again. If the feet are frostbitten, but the person has no option other than to keep walking, it is better to walk on frozen feet, since thawed tissue can be greatly harmed by mechanical damage or pressure."
--Michael W. Perry, Across Asia on a Bicycle
@HTEngineer Thanks for a lot of helpful advice. I'd add some additional remarks about food and water.
1. As much as we need those added calories, it is possible to get too tired to want to eat and high altitude can also alter our taste and cut down on appetite. Find out what foods and drinks you like during strenuous activities and pack them along. In my case, spicy as in mustard helps and a slight tartness for drinks (as in grape juice) helps keep me pouring down the fluids.
2. Plan ahead. Snow is self-insulating. So you're depending on snow for water, it'll melt faster if added to a half-filled container and shaken up. The same is true with heating over a stove. Don't run out of liquid water and then try to melt snow. Make water from a snow-water mixture before you run out of water.