You are skiing off-piste with friends when you reach what appears to be an open field. You are halfway through when you hear cracking sounds under your skis. Suddenly, you fall into a frozen lake. The cold water is a shock. You feel as though thousands of needles are piercing your body. You gasp and begin to hyperventilate. You try to grab the edge of the ice, but the weight of your backpack and skis makes it almost impossible to stay afloat. You are convinced you will drown or die from hypothermia. What can you do?

Deaths from cold water immersion occur every year—even among swimmers trying to cool off in Lake Tremblant on a hot summer day! Most people believe hypothermia will kill them within 5 minutes of immersion, so they panic and drown. In reality, you have more than 30 minutes before becoming hypothermic, even in icy water. Let’s look at the different phases the body goes through during cold water immersion.

Phase 1: The Thermal Shock Response
The thermal shock response is the body’s initial reaction to immersion in water colder than 15-20°C. The rapid cooling of the skin triggers a gasp reflex, hyperventilation, and an inability to hold your breath. This response can lead to drowning if the victim’s head is submerged during the initial entry into cold water, and can contribute to drowning in situations where the victim needs to hold their breath (waves, backwash, white-water, current, open sea, etc.). Skin cooling also causes peripheral vasoconstriction and increases cardiac output, heart rate, and blood pressure. These sudden cardiovascular changes can lead to arrhythmias, heart attacks, and strokes in predisposed individuals. For those who manage to relax and control their breathing, thermal shock typically dissipates in 1 to 2 minutes.

Phase 2: Cold Incapacitation
Survivors of the thermal shock response will then experience cold incapacitation or loss of basic neuromuscular skills caused by the cold. Cold incapacitation generally occurs during the first 10 to 15 minutes of cold water immersion. Significant peripheral cooling of muscle fibers and nerves leads to stiffness in the limbs, poor coordination of both gross and fine motor skills, loss of strength, and an inability to swim. During this phase, it becomes increasingly difficult to perform basic survival actions, such as grabbing a rescue rope. Victims of cold incapacitation drown because they are unable to swim before hypothermia even has time to set in.

Phase 3: Onset of Hypothermia
Most deaths from cold water immersion result from drowning during the first two phases of immersion. Hypothermia only becomes a significant concern if immersion lasts longer than 30 to 60 minutes. Hypothermia occurs when continuous heat loss decreases the core temperature. Hypothermic victims will eventually lose consciousness and drown unless they are wearing a PFD (personal flotation device) or another factor allows them to stay afloat. If the victim’s head is kept above the water, they could survive for another hour or more before their heart stops.

Phase 4: Rescue Collapse
Despite recovery in an apparently stable condition, a survivor of cold water immersion may experience rescue collapse, ranging from fainting to cardiac arrest during the rescue period. Rescue collapse deaths have occurred anywhere from a few minutes before rescue to 24 hours afterward. Three causes of rescue collapse have been proposed. The first is secondary cooling of the core temperature, where the core temperature continues to drop even after leaving the cold water. The second is blood pressure collapse. When rescue is imminent, the victim may relax enough to cause a drop in blood pressure, which can then lead to fainting and drowning. The rescue itself can also lower blood pressure. Extracting a victim from the water in a vertical position removes the hydrostatic pressure around the lower limbs and causes blood to pool in the legs, which then lowers blood pressure. Therefore, it’s important to remove cold water immersion victims in a horizontal position. The third proposed cause of rescue collapse is related to factors that increase the risk of ventricular fibrillation, such as hypoxia, acidosis, and rapid changes in pH. Additional cardiac effort or sudden manipulation may be enough to trigger cardiac arrest in a hypothermic heart. Cold water immersion victims should be handled very gently during and after rescue to avoid heart irritation.

So, back to our case, what can you do? Well, it’s best to avoid exposure to cold water altogether, but when this isn’t possible, you can ensure you're prepared for the possibility of cold water immersion.

Before Possible Exposure:

• Assess your swimming ability and practice self-rescue techniques in different cold water conditions (waves, backwash, white-water, current, open sea, etc.).

• Wear insulating clothing, such as a dry suit or wetsuit.

• Wear a foam life jacket rather than an inflatable life jacket. Without a life jacket, you will expend precious energy trying to stay on the surface and will be unable to keep your head above water if you lose consciousness.

If You’re Immersed in Cold Water:

• If possible, try to enter the water slowly and avoid submerging your head. Never dive into cold water.

• In the first minute, control your breathing and DO NOT panic. Then get out of the water as soon as possible.

• Only start swimming if you can reach a safe place in less than 30 minutes.

• If self-rescue is not possible, minimize your exposure, ensure your flotation, and call for help. Actions to minimize heat loss should be initiated.

• If you are alone, use the HELP position (Heat Escape Lessening Posture). Stay as still as possible with your arms pressed against your chest and your legs bent and tightly together.

• If you are in a group, huddle together. Bring your chests as close as possible, wrap your arms around each other’s backs, and intertwine your legs.

Remember you have 1 minute - 10 minutes - 1 hour:
1 minute to control your breathing, 10 minutes of effective movement to exit the water or protect against drowning, and 1 hour before losing consciousness due to hypothermia.