Arguments
The best strategies to keep bodies cool in a heatwave, according to researchers
Posted on 21 July 2016 by John Abraham
As we hit high-heat season in the Northern Hemisphere, it is useful to clarify tactics that can be used to help maintain healthy body temperatures. These tips are not commonly known and can be adopted by anyone, anywhere. While I am a climate scientist, my funded work is in the area of heat transfer, particularly in the human body. I work with medical companies to maintain healthy body temperatures during surgeries or other situations. I also deal with scald burns and I often serve in burn injury litigation.
Here are some key tips. First, avoid hyperthermia in the first place – drink plenty of fluids, avoiding direct sunlight, trying to get a respite from heat each day, avoiding physical exertion during the hottest parts of the day are all great suggestions. But, if you need to lower a body temperature, Dr. Robert Huggins, VP of Research and Athlete Performance at the Korey Stringer Institute suggests:
The general rule is to cool as much of the body’s surface as possible …. the larger the area you cool and the colder the device you use to cool it the faster the cooling rate. An appropriate goal is to use a method that cools at a rate of 0.15°C per minute. This can typically be achieved by immersion techniques using a tub or other basin filled with ice cold water or via rotating cold ice towels over the body.
During exercise if there is limited access to the entire body (e.g. football or fire-fighters), cooling the hands, face and feet will help, and if possible, use a fan to increase evaporation from these surfaces. However, when heat stroke is suspected, these strategies are not nearly as effective as whole body methods; opt for immersion cooling.
So how do you know if someone is suffering from hyperthermia or heat stroke? A great resource is the Korey Stringer Institute, which lists many symptoms for heat stress such as fatigue, weakness, pale appearance, headache, nausea, vomiting, fainting, dizziness, and others. The heat stroke treatment they recommend, while geared toward athletes, is still useful for the rest of us.
In many actual situations, full body immersion isn’t possible. What can people do then? Well, there is extensive evidence that supports the cooling of the hands, face and feet. The technical term for these areas is glabrous (non-haired). These areas are excellent at transferring heat and in fact, the body can increase the blood flow to these regions which, when cooled, flows back to the body providing core cooling.
One paper looked at the impact of cooling athletes’ palms on their ability to recover between exercise sets. They found that “palm cooling hastened heat removal”. Another publication, just out in 2015 in the journal Wilderness and Environmental Medicine compared cold packs applied to the neck, groin and armpit with cold packs applied to the cheeks, palms and feet. That study found that applying cold packs to the cheeks, feet, and hands almost doubled the cooling effect. They write:
When I went through 117 degree Fahrenheit heat a few years ago, I had no airconditioner in my apartment (The electrical wiring couldn't allow for it with all the appliances running.). Fans did not work above 100F even with frozen water bottles in front of them.
It was that temperature outside and inside my apartment. Other than walking naked around the house I decided to improvise. I put a small bucket of water into a freezer overnight and the next morning I removed it. It was not frozen except for a thin crust of ice on top. The water was ice cold though.
I dunked a tight fitting T-shirt into the water; wrung out the excess water; then I put the T-shirt on.
I shivered from the cold for less than 3 seconds and immediately after that I felt an intense sense of relief. I was still naked from the waist down but there was no one to notice.
At night, with the temperature no lower than the mid 90s F I dunked a bed sheet into that same water and had a small fan blowing besides my bed. That's the only time that a fan can provide relief.
I would also suggest keeping your hair short and have a beanie for your head also soaked in ice water.
The following article describes the best way to use a fan. Basically it advises don't just blow air at the sofa or bed. It says point a fan at the open window at night, to blow hot air out of the room, and let the outside air which is sometimes cooler enter the room. Haven't tested the idea as yet.
www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=11590919
The article also says turn rooms into "chilly bins". So keep everything like windows and curtains closed during the day, to conserve cool air from the night before.
nigelj @2, I note that there is a contradiction between the advise on the proper use of a fan, and the proper employment of windows.
In my experience there are at least two human physiological approaches to cooling. I, for example, will sweat copiously at even slightly above normal temperatures or levels of excertion. Provided I am bathed in an air stream of relatively dry air I remain cool at temperatures up to 40 C and even with high levels of excertion. Lacking that air stream, or if the air is humid, I swelter. (I have noticed this pattern in other people who, like me, have grown up in hot arid areas with plenty of drinking water.) In contrast my wife sweats little unless it is very hot. The result is that, unlike me, in typical Brisbane summer weather she does not become drenched (or dehydrated) and her skin continues to cool; but she cannot cope with very hot dry air.
It seems probable to me that the advise from the NZ herald (keep overall room temperature down) would be good for my wife and people like her. For me, however, there is no substitute for a high volume air flow over the skin, so I am best of sitting directly in the air stream from a fan turned to high. Likewise I often benefit more from increased natural air flows from open windows, even if the air is hotter than the still, inside air (within limits).
Tom Curtis at 3
You could well be right. I haven't tried anything in the artcle yet, but thought it was worth posting as something to at least experiment with.
I respond more like your wife, so it might work for me. We all have different metabolisms.
You might end up in separate bedrooms to your wife on those extremely hot nights. Better solution, buy an air conditioner!
Read the article again, guys. It says that "full body immersion" is the best method in an emergency, but not always available.
No, it is always available in virtualy every modern house: a bathtub. Mine usualy holds cold water in summer (which comes from my rain tank therefore costs nothing) so that I can dunk for a moment as needed - usually every hour of so in record heatwave days. Less water usage and more effective than shower, truely zero-emmision method, unlike fan, or dreadfully emmsion-heavy AC. By overusing AC, the civilisation increased the heatwaves and now people are trying to crank AC more to escape from heatwaves? Where does this nonsense ends?
Chriskoz at 5
The article made many points. I just posted it to see what people thought. I'm not too sure about pointing a fan at the window, but will experiment to see.
Cold baths are a great idea, but tedious to do all night. This is when the heat really gets to me as I'm a light sleeper at the best of times.
I agree air conditioning has partly got us into the high emissions problem, but we could ideally use solar powered fans and AC, with battery storage at night. Fans and small AC units dont draw much electricity.
Was it above wet bulb 33 or was it 35 degrees C that humans can't survive without some artificial cooling. We lived in the desert for many years but there, despite 40 degrees every day, the wet bulb temperature was down around 20 due to the dryness of the air. How much of the earth is going to become uninhabitable.
Here it is. Apparently it is 35 degrees wet bulb.
"Heat stress reduces labor capacity under climate warming". Geophysical Fluid Dynamics Laboratory. Bibcode:2013NatCC...3..563D. doi:10.1038/nclimate1827
Link fixed [GT]
William
Steve Sherwood & Matthew Huber had a paper on this several years ago here.
And the limit is 35, although those in poor health may struggle at lower temperatures.
The biggest problem is high temperatures combined with high humidity, as the inability for sweat to evaporate means its harder to cool down. I think this creates high risk for heat stroke.
And guess what? We are creating a world with both higher temperatures and more atmospheric moisture. It wont be very nice, particularly in subtropical zones.