SHOCK FROM THE COLD
The sudden decrease in skin temperature, such as that resulting from the sudden immersion or entry of cold water inside the isothermal fact, causes profound physiological changes: there is an immediate increase in heart rate and blood pressure and a period of frank difficulty or even inability to breathe. Even experienced swimmers may be unable to coordinate breathing with swimming movements and inhale water.
Rapid pulse increase and hypertension can cause circulation failure in physically poorly prepared individuals. If the victim survives this initial reaction the organic responses normalize and hypothermia begins to settle.
The diver who is not properly protected for the temperature of the water in which he is submerged will suffer progressive hypothermia (also called sub-acute or chronic).
THE MOST FREQUENT CAUSES OF HYPOTHERMIA IN THE DIVER ARE EXPOSURE TO COLD WIND BEFORE OR AFTER DIVING, THE CHOICE OF AN INAPPROPRIATE ISOTHERMAL SUIT, DIVING IN VERY COLD WATER AND LONG PERIODS OF INACTIVITY IN THE WATER
In a first phase, if the diver leaves the water, or is removed, with a central temperature of 33 to 35°C (mild hypothermia), he is conscious and breathing spontaneously. It presents some changes, such as generalized muscle tremor, cold sensation in the extremities that evolves to loss of sensitivity and increased diuresis that can lead to dehydration. The difficulty in performing small tasks is associated with slow thinking and reactions, which can cause dangerous situations, because the diver cannot handle his equipment effectively.
If the diver is pulled from the water at a more advanced stage of hypothermia, with a central temperature of 30 to 33°C (moderate hypothermia), he/she has difficulty responding to stimuli or may even be unconscious. Muscle tremor persists to the limit at which it is replaced by muscle stiffness. Heart rate and output decrease, respiratory rate decreases and consequently body tissues receive less oxygen. Most victims of hypothermia at sea die at this stage because they have difficulty swimming or keeping their heads out of water.
If the diver is removed at a central temperature below 30°C (severe hypothermia), he is unconscious or “semiconscious” and muscle tremor is replaced by muscle stiffness. Breathing and pulse are depressed or unfoundable and the risk of cardiac arrest is high.
First aid consists of avoiding further heat losses by removing the diver from the water and placing him in a sheltered place from the cold and protected from the wind. The victim should be handled with care always keeping it within the horizontal position when being removed from the water to prevent cardiovascular collapse.
In moderate cases of hypothermia, in which the diver is conscious should remove the isothermal suit, wear warm clothes, make him ingest sugary hot drinks and as soon as possible introduce it into hot water (40°C).
In more severe cases the dive companion must proceed according to basic life support techniques. If the decision is to start pulmonary cardiorection (CPR) do not forget that it should only be interrupted when the diver is heated.
A VICTIM OF SEVERE HYPOTHERMIA SHOULD BE CONDUCTED AS SOON AS POSSIBLE TO A MEDICAL CARE UNIT
If, for any reason, the diver is required to remain in the water waiting for help, he/she must adopt the following procedures:
- Adopt a fetal position, with the head out of water, knees shrunk next to the body and the arms between the legs (this attitude increases the survival time by 50%). Only swim if you’re too close to security.
- Group divers should stay together and embraced (this attitude minimizes heat loss and makes them easier to detect). If possible, use any additional protection on the head. Avoid diving again before they are well heated.
NEVER GIVE ALCOHOLIC BEVERAGES TO A VICTIM OF HYPOTHErmia, AS THESE INCREASE BODY HEAT LOSS