Immersion in water below sixty degrees evokes dramatic physiologic changes that can make survival problematic. Understanding these changes can save a person's life.
Many people believe that the greatest danger of cold-water immersion is hypothermia, but the most common cause of death in this scenario is drowning. Unfortunately, swimming ability does not necessarily improve one’s chances of survival.
Sudden immersion in cold water (<60ºF) prompts a series of sequential and incapacitating physiologic reflexes that – if uninterrupted – vastly increase one’s likelihood of drowning.
The Four Stages of Cold-Water Immersion
Stage One: Cold Shock
- Begins immediately upon cooling of the skin, peaks within 30 seconds, and lasts two to three minutes.
- Characterized by instantaneous gasping, followed by rapid and deep breathing. If the victim’s head is beneath the water at this time, drowning can occur immediately. Additionally, rapid breathing leads to decreases in the normal levels of CO2 in the bloodstream, which leads in turn to confusion, dizziness, or even unconsciousness.
- Heart rate, blood pressure, and cardiac workload increase. Such changes can precipitate fatal arrhythmias or heart attacks in susceptible individuals.
- Breath holding ability decreases dramatically. This may complicate one’s ability to escape from a capsized boat or submerged vehicle.
Stage Two: Functional Disability
- Sets in after initial cold shock; lasts approximately 30 minutes.
- Muscles and nerves in the extremities cool significantly.
- Swimming efforts become increasingly difficult and ineffective.
- Manual dexterity and grip strength are markedly decreased. Victims lose the ability to grasp lifelines or floatation devices, climb ladders, or otherwise assist in their own rescue.
Stage Three: Hypothermia (Core temperature <95º)
- Usually begins after 30 minutes of immersion (the body’s core cools relatively slowly, even in cold water).
- Violent, painful shivering occurs (this may begin in stage two).
- Confusion and lethargy become problematic. Efforts to remain afloat become feeble.
- As core temperature drops further, victims assume “instinctive drowning response” (loss of voluntary control of arms; arms extend laterally in an effort to press downward on water; little or no supporting kick; unconsciousness and/or submersion and drowning are only 20 to 60 seconds away).
Stage Four: Post-Rescue Collapse
- Those who survive immersion are still at risk. Core temperature may continue to drop, even after rescue; if heart temperature falls to around 77º, cardiac arrest can occur.
- Hypothermia slows normal adaptive responses to changes in posture or skin surface warming. If rescued victims are left upright, sudden, uncompensated drops in blood pressure may cause unconsciousness or cardiac arrest. Metabolic changes (e.g., acidosis) caused by hypothermia can also contribute to fatal cardiovascular events.
Surviving Cold-Water Immersion
- Personal floatation devices (PFDs) are probably the most important factor in cold-water immersion survival. They will keep the victim’s face above water in the initial cold shock phase, when gasping could lead to immediate drowning. PFDs also allow individuals to assume heat-conserving postures (hands crossed over chest, arms pressed closely to sides, knees drawn toward chest, ankles crossed).
- In the absence of a PFD, victims should NOT remove clothing; it actually provides buoyancy and helps conserve body heat.
- Avoid swimming. Even strong swimmers only have a 50/50 chance of successfully swimming a half mile in 50º water. If swimming is absolutely necessary, a conservative stroke that keeps the head above water is recommended (i.e., breaststroke). Use small movements when treading water.
- If floating wreckage is very close, get out of the water and stay out. The rate of body heat loss is 25 times greater in water than in air of the same temperature, even when the body is wet.
(Adapted from Jacobs, M. Cold-water immersion. Wilderness Medicine Magazine 2008;25(3):6-7)
Initial cold shock only lasts a few minutes. Victims who understand the physiologic challenges – and who remain calm and control their breathing – have a much better chance of surviving cold-water immersion.
The copyright of the article How to Survive Cold-Water Immersion in Winter Sports is owned by Stephen Allen Christensen. Permission to republish How to Survive Cold-Water Immersion in print or online must be granted by the author in writing.
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