The lifesaving diving reflex
While the diving reflex can protect people during cold-water immersion, it can lead rescuers to wrongly conclude that the victims are beyond recovery.
Most people recovered in cold water near-drowning cases show the typical symptoms of death:
- cyanotic (blue) skin,
- no detectable breathing,
- no apparent pulse or heartbeat and
- fully dilated pupils.
These symptoms don’t always indicate death; they are also the body’s way of increasing its chances of survival through what scientists call the mammalian diving reflex.
The diving reflex is most evident in marine mammals such as whales, seals or porpoises. During this phenomenon, the body diverts blood to circulate it between the heart, brain and lungs (at only six to eight beats per minute in some cases).
Marine mammals have developed this ability, which allows them to remain underwater for extended periods (more than 30 minutes in some species) without brain or body damage.
In humans, the diving reflex is not as pronounced as in marine mammals. The factors that enhance the diving reflex in humans include
- Water temperature: Colder water creates a more profound response that may be more protective to the brain.
- Age: Younger victims have a more active reflex.
- Facial immersion: Cold-water stimulation of the face triggers the pathways necessary for these responses.
Although the diving reflex can protect people during cold-water immersion, it may confuse rescuers into thinking that a victim is dead. Resuscitative efforts such as CPR should be started immediately for these victims. Numerous children have been brought up from freezing water after 30 minutes and successfully resuscitated. –Greg Watt
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