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Cold Shock — Information to Help Keep Paddlers SafeMartin Strand III (aka Marty) The American Canoe Association (ACA) says, “The keys to managing any risk are knowledge and skill.” (1) The former is the purpose of this paper; to caution and inform, not frighten. Keep in mind, venturing out on the water to have fun or exercise is optional. Returning home is mandatory. Before giving in to the temptation of going for that long awaited first, or subsequent, spring paddle this year on a beautiful warm sunny 70° F day, consider the following, even if you remember to think about the cold water and know about hypothermia.
DefinitionsCold Water has a number of definitions. In Alaska and British Columbia some sources say it is water below 77° F (25° C) (7) (8) or it is water below 70° F (21° C) (9). Others report it is below 60° F (15° C) (1) (6) (10). USCG data shows about 3/4 of all canoe and kayak fatalities occurred in water < 65° F (18° C). (6) Still others call the temperature at which water can be considered cold is “variable”.(11) The important concept for paddlers to recognize is the colder the water, the higher the risks with inadvertent cold water immersion. Cold Shock describes a series of rapid, linked, involuntary and detrimental physiological events in the inadequately protected human body characterized by immediate loss of breathing control, incapacitation and high risk of drowning or sudden death when suddenly immersed in cold water. Most of these immediate body responses are increasingly fatal as the water temperature decreases. Hypothermia is a process where the body loses heat to the environment (water or air) faster than it can produce heat. This lowers the body’s core (brain, heart and lungs) temperature with accompanying decrease in bodily functions critical for survival in proportion to the extent of the lowered core temperature. Hypothermia takes time; the rate at which it occurs is proportional to the coldness of the water temperature and the victim’s insulation. New thinking and research over the past decade has given birth to the concept of cold shock from sudden cold water immersion. This now explains why some experienced paddlers have been found dead in their overturned boats with their paddle still in their hands apparently without having made an attempt to wet exit or why observers of fatal cold water accidents have reported “He just tipped over and never resurfaced” or “He was a good swimmer and so close to shore but it looked like he was just flailing around and then just went under.” And why, in the most blunt message, 9 elite Marines in March 1968, trained as water safety instructors but wearing only sweat suits paddling the Potomac River on water that was 36° F, after their war canoe capsized, none could swim 100 yards to shore. None survived. (12) This signals that a physically fit person, who is a good swimmer in warmer water, has no guarantee of survival from the adverse effects of cold water unless they have prepared to be immersed. (1) It is now understood cold water kills by cold shock, drowning and advanced hypothermia. (13) Unless death occurs at any point, this occurs in three continuous phases: an initial cold shock response, a short term immersion and loss of performance phase and long term immersion with onset of hypothermia. (11) This writing addresses the first two since much has been written about hypothermia. Phase I: Initial Cold Shock Response (1 - 4 minutes)First, the extremely unpleasant sensation of sudden cold water on skin triggers a cluster of breathing and heart responses; their severity depending on the extent and rate of skin cooling. This immediate neuromuscular reaction can cause a series of huge uncontrollable gasps for air called the Involuntary Gasp Reflex. If your head is underwater, you immediately drown. It also causes the Inability to Hold Your Breath while under water from a pre-immersion mean of 45 seconds to a mean of 9.5 seconds (one subject averaged less than a second) in 41° F water.(14) Imagine the implication for an unprepared kayaker trying to set up for a roll or wet exit! However, if you manage to rapidly resurface, you may then have either your lungs full of cold water and can’t breath or you will immediately begin to Hyperventilate, which usually follows the gasp reflex and is characterized by rapid and deep in/out breaths along with Lack of Breathing Control which makes it easy to inhale water and drown. Also, as higher than normal blood levels of carbon dioxide are being quickly exhaled while gasping and hyperventilating, blood pH rises (respiratory alkalosis) which can cause cardiac arrhythmias, cramps from muscle tetanus, and cerebral vasoconstriction which starves the brain of oxygen resulting in disorientation, confusion and Loss of Consciousness. Simultaneously, cold water on body skin causes constriction of capillaries under the skin. This Increases Heart Rate, Cardiac Output and Blood Pressure. These changes alone may be tolerated by a young healthy person but can be dangerous for older paddlers with hypertension or other underlying heart disease. Other sequelae challenging the immersed paddler for survival in cold water include pain, claustrophobia and disorientation which causes Panic. This stimulates release of adrenaline in the body (“fight or flight” response) which, normally, is our way of automatically protecting ourselves from harm. Paradoxically here however, it adds dramatically to existing cardiac changes from capillary constriction. These conditions, along with a huge volume of cold water in the lungs cooling the heart with accompanying blood chemistry changes, can precipitate Cardiac Arrest and sudden death. Phase II: Short Term Immersion and Loss of Performance (1/2 hour)If cold shock is survived but immersion continues, cooling proceeds rapidly leading to decreased extremity neuromuscular activity and blood flow causing finger stiffness, poor coordination of motor activity and considerable loss of strength. This loss of motor control makes it difficult, or impossible, to perform survival procedures like rolling, reentry, blowing your whistle and signaling for help or grasping a rescue line. Along with disorientation and panic, it can easily account for the reports of apparent “flailing about” of good swimmers in their death throws of cold water immersion. In this phase, the cold water victim, by inhaling too much water or by inability to maintain survival skills of staying afloat, swimming or grasping a line, ultimately drowns. Phase III: Long Term Immersion With Onset of HypothermiaThe reader is referred to multiple other sources. Prevention of Cold Shock
ConclusionThe main objective in paddle sports is to stay safe. For the informed and responsible paddler on cold water, acceptance of the issues of cold shock means dressing appropriately, maintaining your skills and avoiding cold water immersion to keep from drowning in the short term and warding off hypothermia in the long term. Grandpa, an old Navy man, used to say, “Water (the sea) simply waits for the innocent but actually stalks the unprepared, the careless and the arrogant.” Addendum: Additional Cold Water Information
References(All links open in new browser windows.) (1) “Cold Water Survival”, www.acanet.org/safety |