Oral measurements do not accurately measure changes in the core temperature. This lowers the heart rate, increases blood pressure, shuts down blood circulation to all but the body's core. The result is a lowered metabolism, so the body can conserve oxygen. This may help survival in cold water, since oxygen in the blood is carried to the brain and vital organs where it is needed most. The dive reflex and hypothermia can lead to fatal cardiac or respiratory arrest.
Survival depends on prompt first aid and medical assistance.
Cold water near-drowning victims have been revived after as long as one hour under water. Professional medical care is needed to resuscitate these victims, but rescuers should not give up on victims of extended cold water submersion. Persistence in first aid and rescue efforts is also critical for cold air hypothermia victims. Rescuers may have to enter the water to get the victim. Once out of the water, gently remove wet clothing and cover the person with dry clothing or blankets.