Tag Archives: mild hypothermia

HOW TO: Understanding hypothermia in swimmers – Mild Hypothermia

When all fails and I am at a loss for something to write about, I can write about cold, my favourite subject. Especially in the context of Cork Distance Week coming in two weeks, when we had a few people pulled from the water with hypothermia last year.

For anyone involved in open water swimming in Ireland, the UK and other Northern Hemisphere cold water locations, being able to spot and diagnose dangerous hypothermia in a swimmer is an essential skill. To do that properly an understanding of hypothermia is useful.

It’s essential to understand that there is no such thing as sudden hypothermia. Most of us grow up hearing this myth, (for example I remember stories of survivors from the Titanic freezing to death in five degree water within fifteen minutes, and that fifteen minute myth is repeated all the time).

The heat in your body can’t instantly disappear. The Second Law of Thermodynamics is always the Universe’s governing and inviolate principle. Hypothermia is a developing situation over time. Your body has enough stored heat that even in zero degree water, you probably won’t develop severe hypothermia until about thirty minutes, though you will be subject to After-drop and potentially lethal consequences even if you emerge before that time. And Afterdrop itself isn’t a myth, as is sometimes inversely claimed to sudden hypothermia, it does exist.

Cold shock response is an entirely different thing to hypothermia, it’s the bodies response to sudden cold, with gasping reflex, hyperventilation and possible acute pain in hands, feet, face and head, and even cardiac events. The biggest danger in immersion is uncontrolled hyperventilation leading to sudden aspiration of water. You gasp and breathe water into your lungs and drown.

Breathing rate increases for the first 20 seconds in cold water

This is the main reason why a diving or jumping entry into cold water for people not cold-acclimated is absolutely a stupid thing to do, and not tough or macho. This response is attenuated in cold-adapted swimmers.

Definitions of Mild Hypothermia can vary depending on where you look but a core body temperature of between 35° and 36° when body-normal is 37° is a good measure, i.e. a drop of about two degrees is a good indicator. The hormone ADH, (anti-diuretic hormone) which controls urination in suppressed and some blood volume is shunted to the core so there is a decrease in blood volume and some dehydration also. There are no long-lasting effects of mild hypothermia, (such that it can be used as a medical procedure for brain protection during certain operations). Almost every serious open water swimmer in these waters will have experienced it as completely normal, and the body acclimates and adapts as we have seen before, by blunting initial response, reducing stress hormones, and increasing brown adipose tissue.

However, people with any diagnosed cardiac problems should avoid cold water swimming.

And also as we’ve often discussed previously, mild hypothermia leads to peripheral vaso-constriction, the reduction of blood flow in the periphery. With experienced open waters mild hypothermia is the completely normal and usual state, in Irish and UK waters. The swimmer will still be able to talk and will still retain motor control in the fingers, but often with reduced dexterity. Surface temperature will be decreased.

Mild hypothermia will of course lead to more severe hypothermia shgould the swimmer continue to be immersed or unprotected. Hypothermia will eventually result for everyone in temperatures under twenty degree is they stay swimming long enough.

There are no great  concerns in recovering from mild hypothermia, just get dry and dressed quickly, following the usual procedure of dressing the torso and head first, and warming up with a walk. Do NOT vigorously dry the extremities even in mild hypothermia.

In diagnosing mild hypothermia, simply seeing if there is some chattering or shivering out of the water. In the water is more difficult, but the swimmer might have clenched jaws and have a minor difficulty speaking freely, or maybe report lesser claw-like symptoms in the hands (lessening on full hand motor control).

In the next article we look at Moderate Hypothermia.

How we FEEL cold water (loneswimmer.com)

Peripheral Vaso-constriction in pictures (loneswimmer.com)

Where did my CLAW go? (loneswimmer.com)

Extreme Cold Adaptation in Humans Part 1 (loneswimmer.com)

Click to embiggen

Swimming with The Second Law of Thermodynamics

This is a one subject site, open water swimming.

Everything on the site relates to open water swimming. But since open water swimming is part of my life, sometimes other parts of my life or some of my interests get pulled in. They may look tangential but it’s because I’m trying to contextualize my swimming life. Like all open water swimmers, you can’t extract open water swimming from our lives and somehow find the real person.

So I occasionally write about Ireland and Irish culture or humour, because it’s where I (mostly) swim. I write about pool swimming occasionally, because it’s where I swim half of the year. (But there are a multitude of better pool swimmers than me, so when I write about it, it’s from an average pool swimmer’s point of view).

I write about the sea, the weather, my dogs who accompany me to the coast, the books or media that inform or help my swimming. I write about my swimming friends, real life and online (I don’t distinguish, I don’t have to have met someone to consider them a friend) from whom I learn.

I was getting some aches as the training volume was building up so I had another massage at the end of the week. I was developing a tightness in the centre (belly) of my left deltoid (shoulder muscle) and a really deep and sore ache in my right trapezoid (upper centre back). I also has a serious pain above my left glute (butt cheek) that only expressed itself once a swim went over three hours, (so this wasn’t a problem much). The massage hurt like hell. The delt eased out completely, I won’t know about the glute until the next long swim. The trap was still really sore afterwards and I hoped it would ease out over the next 24 hours. To aid that I looked forward to the weekly (at this time of the year) cold water swim.

This is my home. Guillamene Cove, on Saturday, from side to side, Click to mucho embiggen

It was a horrible morning. Cold all week, it was a little bit warmer on Saturday while rest of Europe was being hammered on the anvil of an extreme cold snap, with even the sea-shore freezing in Britain. But the air temperature leaving the house was about 8 degrees Celsius. This is the advantage of Irish weather, it’s mild in average, no great summers, no terrible winters. But the sea water temperature was down to 6° Celsius (43°f). It was overcast, Force Three onshore wind and with about a two metre swell, but I didn’t care. Just let me out there.

According to Polar Bear Joe at the Guillamene, it was 41°f the previous day (5°C) with colder air, coldest water temperature of this winter so far.

The entry was fine, and the next 14 minutes were euphoric. That word actually came to me while I was swimming. Isn’t that part of the reason we swim, that feeling? I’ve been trying to explain that feeling for two years now. During the swim, all my existential worries evaporated and I was at peace for the first time in a week. At the fifteenth minute I noticed the cold pain beginning in fingertips and feet. Given conditions were a bit rough and I would need to navigate the rougher water returning over the Comolene reefs, I turned back before I reached the pier. I was in toward shore closer than my normal outside deeper returning track, and it was really rough passing beneath the last house on the cliff.

The coast road from the Guilllamene facing Tramore, running above the normal swim route

I was back to the steps at 41 minutes, stumbled upwards on my numb feet to my fake Crocs (thanks Nuala) high on the steps. Someone started talked to me as I fumbled to get my goggles, cap and earplugs off. All I heard was a voice. With the ear plugs off and as my eyes cleared, it was someone with an American accent standing right beside, I mean right beside me, asking me how far I’d gone. As I tried to mumble a frozen-jaw response I also tried to make my way quickly to my box to start getting changed as soon as possible.

41 minutes at six degrees Celsius is the furthest I’ve gone. I knew what was coming with the Afterdrop. It would tough. I needed to optimise getting dressed as soon as possible.

As I got changed, with some difficulty, trying to get covered as my core temperature was dropping due to the inward flow of cold blood, conversation continued about cold water swimming as I struggled to answer and make sense, not easy when in this state.

I was in that hazy post cold swim state of mild hypothermia, where I’m pretty certain that I am functioning fully and that I can remember everything clearly, but later realise it’s not necessarily the case.

Later I wonder to myself. 41 minutes at 41 minutes at six degrees Celsius doesn’t seem like that much to me. I know, as I always do, that I could have gone further, why didn’t I swim for a nice round 45 minutes? But I realise that in these circumstances, when I am by myself, I let my body and a sub-conscious experience decide my swim times. With doing 41 minutes in 6° Celsius, I now, finally, have no doubt that should we get a 5° degree temperature this winter, the ice-mile is well within my capability. But for now, I can’t actually prove that officially.

Swimming, like everything else, is governed by entropy, which always increases, therefore order (or you could term it information in certain circumstances) is always reducing. Entropy is a measure of disorder. Eventually the dead hand of the Second Law will hold sway over all, as scientist and author Stephen Baxter once wrote, it’s the ultimate scientific explanation of the universe’s evolution, which is governed by the Second Law of Thermodynamics. In a closed system, entropy increases, and the universe is a closed system. Within the smaller system of the earth, the human body is a closed system. It loses heat unless energy is input back into the system to offset loss. As cold water swimmers, we understand experientially the Second Law better than most. Hypothermia will always get you, regardless of experience. If the water temperature is below normal core temperature, no matter how high otherwise, it just will take a longer time. Because of the Second Law of Thermodynamics we get cold. So we need heat and food, two forms of energy, since mass and energy are the same thing. The Second Law of Thermodynamics is always there, always swimming with you, always waiting for you.

I have a deep integral sense of the numinous wonder of the world and the universe, that for me, expresses itself most deeply and is felt most strongly in open water swimming, in immersing myself in the green waters. The world is extraordinary, the sea is transforming, my friends are a value beyond price.  But that’s just my own world view.