The chilling truth about cold water immersion
The chilling truth about cold water immersion, by Dr Patrick Buck PhD REMT
Every time you go for a paddle there is always the possibility that you could end up in the water. Capsizing a kayak or canoe is an everyday occurrence and while fatalities are rare, they demonstrate the need for constant water based vigilance. When things do go wrong, especially in fast moving cold water, they can go from bad to worse very quickly. Poor preparation, lack of understanding of the risks and of course not wearing a buoyancy aid (PFD – Personal Floatation Device) can all conspire against you to turn a relaxing day out into a living nightmare. So why does cold water have such a devastating effect on the body? Simply, humans require a stable core body temperature (CBT) of around 37°C to operate efficiently. Even very small CBT deviations from this can have a profound effect on how we feel, perform and think. As a consequence the body must constantly invoke physiological responses to offset any external temperature influence. Primarily this is achieved by either the body generating heat (shivering and increased metabolism) or by minimising heat loss through such mechanisms as vasoconstriction (narrowing of the blood vessels) or even perhaps by just putting on another layer of clothing. On land the body usually has little difficulty in achieving a stable CBT. However, if a person falls into cold water the challenge becomes much more significant. While the body will deploy every mechanism at its disposal to try and maintain its CBT at 37°C, it can only do it for so long. Over time, as the body runs out of energy, the CBT will start to drop. The more it does so, the more critical the situation. If you are still not convinced try this simple experiment next time you are out kayaking to see how long it would take you to rescue someone. Throw a ball or something that floats into the water and then shout RESCUE. Time how long it takes you or your paddle partner to recover the ball. You might get a surprise here. Not as quick as you thought you would be? Now consider doing the same experiment in different water conditions. I think you get the point. In my experience accidents rarely happen on those lazy hazy days of summer. 
There are four distinct stages that a person will experience when they fall into cold water and each has the potential to kill. Firstly a person will experience some level of Cold Shock as they enter the water. This usually lasts between 1 – 3 minutes (stage 1). This presents as the classic gasp reflex and if the airway is below the water when this occurs a person will most likely inhale (aspirate) water and immediately drown. Cardiac issues can also occur especially if a person has a pre existing heart condition. The key to surviving Cold Shock is to stay calm, bring the breathing under control and focus on escape. The Cold shock will pass but it can be fatal if not managed. It is estimated that 20% of casualties who fall into cold water die during this stage. 
Next a person will experience progressive Cold Incapacitation (stage 2). It is during this stage that a large percentage of casualties will succumb to the effects of cold water. In sub 10°C water, the typical Winter and Spring sea and inland water temperatures in many parts of the World, cold incapacitation can start to cause problems in around 10 minutes. Over the next 20 – 30 minutes it will get progressively worse usually rendering the casualty incapable of carrying out even simple tasks, like firing a flare or operating a portable VHF radio. It will also seriously impact on a persons swimming ability and if they were not wearing a buoyancy aid when they entered the water they will drown, make no mistake about it. Breath holding and making good decisions will also become compromised. As the situation worsens even a casualty wearing a PFD may drown as they become unable to coordinate their breathing to match the gaps in spray and wavelets as they wash over their face. 
The ability to self-rescue is lost during stage 2. It is therefore imperative that a person tries to exit the water as soon as possible after falling in. One should not forget that water strips away body heat 25 times faster than air of the same temperature. If a person is unable to self-rescue they should concentrate all their efforts on survival actions like adopting the Heat Escape Lessoning Posture (HELP). 
Hypothermia (stage 3) develops over time and may take between 30 to 60 minutes depending on factors such as water temperature, body composition, age, clothing etc. Hypothermia is certainly not instantaneous like many people think. While hypothermia can obviously result in death it is not necessarily a medical emergency and if treated early a casualty can make a full recovery. The more profound the level of hypothermia the more difficult it is to treat, especially outside of the Emergency Room. Every effort should be made to treat the casualty, as timely and appropriate field care can make the difference between life and death. Finally a casualty will experience some level of Post Rescue Collapse (stage 4). This is of course providing the casualty has not already drowned through swim failure, expired as a result of other injuries or has had a cardiac arrest. Post Rescue Collapse can be, and often is, fatal. An estimated 20% of conscious and viable hypothermic casualties recovered from cold water die as a consequence of Post Rescue Collapse either before, during or after rescue. So when you recover a casualty to the bank make sure you know the correct treatment procedures. Incorrect handling of a hypothermic casualty for example may trigger ventricular fibrillation, a chaotic and ineffectual heart rhythm. Ventricular fibrillation is the leading cause of sudden cardiac death. 
In conclusion the message from this article should be clear, prevention is always better than cure. If for some reason things do go wrong, make sure you have the necessary training and skills to cope with them. And finally always wear your PFD when paddling, because some day it might just save your life. Dr. Patrick Buck, Ph.D, REMT
© buy this book on e-paddleshop.com (worldwide delivery)
Patrick Buck has just recently published ‘A Field Guide for the treatment of Drowning, Hypothermia and cold water immersion incidents’, a book designed to empower and educate First Responder’s to manage drowning and hypothermia incidents in a pre hospital setting. The book has been cited as a ‘robust edition to a First Responder’s toolbox’ and a book ‘that can save lives’.
Patrick is a marine biologist, remote medic, educator and adventurer. Patrick has extensive experience in marine survival and a deep passion for remote medicine and its application in the marine environment.Patrick is currently conducting applied research in the area of marine survival and hypothermia and is specifically interested in modified PFD design to prolong life in austere settings. He is an avid water sports enthusiast with over 40 years experience in surf lifesaving, surfing, kayaking and marine guiding. Patrick is a director of Water Safety 4 All, a ‘not for profit’ organisation dedicated to bringing safety and fun to all water users from all walks of life.
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