Insulating And Protecting Casualties


We always discuss the importance of insulating and protecting casualties on our ITC Outdoor First Aid courses.  Here we share a few of the ideas we discuss and offer information on why keeping a casualty warm is so important.  We hope you find it useful.

The Problem

Casualties may be cold simply because they have been in challenging conditions without adequate insulation.  The problem could also be caused or multiplied by them being inactive and low on energy reserves.  Either way, if they become too cold they may become hypothermic.

However, hypothermia can also be a problem when conditions aren’t cold.  Trauma victims will be at significant risk.  Heat is generated by metabolism and this relies on oxygen being delivered to the cells.  A victim that is losing blood can’t deliver oxygen efficiently.  Around two thirds of trauma patients become hypothermic and death rates are significantly higher and happen quicker in cold casualties.

The Principles of Insulating And Protecting Casualties

With this in mind, it is essential to consider ways of insulating and protecting casualties on wilderness adventures.  The key requirement is to be able to insulate them from the environment and this can be challenging.  Cold temperatures, wind, rain or snow will all take their toll.

When planning an adventure the first thing to consider is how well equipped the group members are.  Do they have sufficient clothing and equipment to protect themselves as well as enough spare clothing.  Conditions may end up being more challenging than expected or the group may get delayed.  

Beyond that, what are the group carrying to protect themselves from the weather and to protect an individual casualty in an emergency? The group may have to wait for assistance or a casualty may need to be left alone while help is sought. 

How Do We Lose Heat? 

Understanding the ways humans lose heat can help us understand ways to counteract that loss.  We can lose heat in 4 ways.

Radiation is loss of heat to the environment due to the temperature gradient.  This will occur as long as the ambient temperature is below 37 degrees Celsius.  Factors important in radiant heat loss are the surface area and the temperature gradient.

Conduction is heat loss through direct contact between objects.  This could be between, for example, a casualty and the ground.  Water also conducts heat away from the body many times faster than air.  This happens because it has a greater density.  This emphasises the need to stay dry.

Convection happens where molecules against the surface of an object are heated and then move away.  They are then replaced by new molecules which are also heated. The rate of convective heat loss depends on the density of the moving substance.  For example, water convection occurs more quickly than air convection.  Wind Chill is an example of the effects of air convection.

Evaporation is heat loss caused by converting water from a liquid to a gas.  Perspiration, or evaporation of water to remove excess heat, is an example of evaporation.  Another form of heat loss is respiration.  In respiration air is heated as it enters the lungs and is exhaled with an extremely high moisture content.

So,  to best insulate and protect a casualty we need to try and counter all these heat loss mechanisms as effectively as we can. How well we can do that depends on a number of factors.  

What Are You Able Or Willing To Carry?

Assuming all the group members are suitably equipped, when deciding what else to carry it is always going to be a trade off between what you are able to take with you and offering the best help for the casualty. 

There is no doubt that a group with tents, sleeping bags, stoves and insulating mats will be able to better protect a casualty over a group with minimal resources.  However, no one wants to carry a huge amount of extra equipment on a fast and light adventure.  

The decision is best decided by a risk assessment of the individual endeavour as a broad number of factors will need to be considered.  Below we are simply sharing some simple principles to guide the decision making process.

Passive Versus Active Rewarming

As humans we use insulation to protect us from the cold.  Insulation works by warming air trapped between the insulation fibres.  This heat needs to be created and humans create heat through metabolism.  

In a cold person shivering is a mechanism to generate heat.  This is effective but demands a lot of both energy and oxygen.  We can also generate heat by activity, but this may not possible for a trauma casualty or someone whose alertness level is lowered.   

Energy can also be provided by energy rich food. However,  this relies on the casualty being alert and well enough to take food on board.  Giving food to a trauma victim also may not be a good idea if they may vomit or need onward treatment.

When a casualty gets colder the shivering mechanism starts to fail. It will still be of benefit to protect them from further heat loss, but wrapping up a very cold casualty won’t warm them very much unless you can use active rewarming.

Active rewarming may be practical for rescue professionals with the resources needed, but warming a casualty in a remote location with minimal resources is very difficult.  Getting a group inside a bothy shelter will offer some shared body heat.  Similarly, if you have a stove it may be practical to make some hot water bottles using drink bottles (but be aware or associated safety issues of burning and leakage).  Other than that, methods of effective active warming are heavy and relatively bulky. 

Equipment For Insulating And Protecting Casualties

So, with the limitations considered, what options are available for insulating and protecting casualties?  As stated above, the exact decisions about what to carry will depend on many factors, but as a minimum we carry something to protect a group and items to keep a group protected and to protect an individual casualty.

Group Shelters Come In Various Sizes – Make Sure You Have One Big Enough For The Whole Group

Group Shelters

Assuming all team members are suitably dressed, it is important to have a shelter that all group members can fit into.  The standard option for this is a group shelter.  Lots of companies make these and they come in a range sizes.  Our favourite, due to their light weight and bulk, are the Supalite models made by Summit Gear.  We usually take them out of the small stuff sack they come in and use a small dry bag.  This means it will stay waterproof in your rucksack and so, even if the inside of your pack has got wet, the shelter will remain dry.  

Just one other thing to note is that some group shelter models aren’t particularly big compared to their stated size. So, we tend to size up a bit (for example, we take an 8 person shelter for 6 people) to allow all group members to get inside and still have room inside for packs.  This adds minimal weight but makes use much more effective.  

Getting a group inside a shelter will soon start to make a difference.  The team will be protected from the elements and you soon start to notice a rise in temperature inside.  Getting everyone to sit on their packs (or something like a rope) will also minimise conductive cooling.  The other advantage to a group shelter is you can make space inside to manage a casualty.  They can stay protected and you and the group can also stay protected while you are helping them.

Sometimes, though, you may need to wrap a casualty up individually.  You may just want to protect them further or may be leaving them alone while you seek help.  What can you carry to protect them?  

(Clockwise From Right) OMM Duomat, Blizzard Blanket, Silver Blanket, Lifesystems Heatshield Bag & Plastic Survival Bag

Individual Casualties

There are lots of products on the market to protect casualties.  We will share a few ideas below but, whatever you choose, the key principles are to get a casualty off the floor and protected from above.

Ground Insulation

For campers the age old method to counter conductive heat loss has been to sleep on an insulated mat.  This also holds true for a casualty situation.  There are some very advanced inflatable mats that are light and compact. However, for speed, simplicity and lightness a closed cell foam mat may work best in an emergency.  The only problem is they are quite bulky.  

Our preference is to carry a section of closed cell matting that will easily fold up in a ‘Z’ shape and tuck inside the back of our rucksacks.  This is about two thirds of body length and would allow the torso of the casualty to be kept off the floor.  Then, an emptied out rucksack or two could be used for the legs and the head could be propped up on some spare clothing.  For compactness we use OMM Duomats.  You could also make your own version from a section of foam mat with the folds taped with duct tape.

Wet Casualties

Getting a casualty out of wet clothing and into dry layers is the best way to minimise evaporative cooling.  However, it may not be practical to unclothe a casualty if you are in challenging conditions.  Also, if the casualty can’t help undress and dress themselves or their alertness level is low it is very difficult to do it for them.

Sometimes the best you will be able to do is wrap a wet casualty in extra layers.  You can also help minimise more heat loss by sealing them into the clothing as much as possible.  If the water can’t evaporate it will slow evaporative cooling.

Convective Cooling

Simple and cheap silver Mylar blankets (often referred to as ‘foil’ blankets) can help by offering some weatherproofness.  They can also potentially reflect heat back to the casualty.  In optimum circumstances it is said up to 90% of heat can be reflected back.   However, as they rely on reflecting heat back, they will inevitably be less able to do this if the casualty is cold to start with.  Our experience has also been that some of these are very small and you will struggle to fully wrap up a casualty.  If you choose to carry one do check sizing when buying.  

There are more advanced options available.  Blizzard Protection Systems products have layers of Mylar with elastic cord between to make air channels.  The elastic keep the air channels open and the trapped air is warmed by the casualty (or by active warming methods).  They make their products as bags, jackets and blankets in 2 or 3 layer versions. 

We like the 2 layer blanket for general use as it only weighs 250 grams.  Blizzard have also added a thin adhesive strip along the edge so a blanket can be easily made into a bag if needed.  We also really like Lifesystems bivi bags and which offer extremely lightweight protection. Details about these are available on the Lifesystems website here.   Both of these products are made from strong, metallised low density polyethylene and the bivi, for example,  only weighs 110 grams.

You can get even simpler options.  The classic orange survival bag has been popular for many years.  They are simple and inexpensive and will certainly help protect a casualty.  If the casualty is unable to move themselves it will be difficult to get them into a bag.  On our first aid courses we encourage people carrying them as a blanket (simply a bag that has been sliced open).  It is easier to wrap some one up and they are very visible. 

We hope our guidance on Insulating And Protecting Casualties is useful.  To learn more do consider joining one of our ITC Outdoor First Aid Courses.  We also have a selection of other first aid advice articles that might be of use.  We have one about First Aid Information Recording is here, one about First Aid Kit Tapes is here and another about Gloves For First Aid is here.