Can babies breathe underwater?

Question: Why can babies naturally dive?

Immediately after birth, babies behave like experienced professional divers: As soon as their face gets underwater, they automatically hold their breath and their heartbeat slows down. At the same time, they even perform rudimentary swimming movements. But where does that come from? Is that a reflex? And if so, do we adults still have it or is it lost again after infancy?

The babies owe their unusual diving talent to several reflexes, as Claus-Martin Muth from the Ulm University Hospital explains. A respiratory protection reflex ensures that newborns hold their breath even if they run a little water on their faces. "It also works if you blow the baby's face with a blow dryer or blow into his nose," says the doctor. However, this protective reflex is already lost after five to eight months - presumably because the cerebrum is then mature enough to consciously control the holding of breath in critical situations. This no longer works in adults and cannot be trained or taken back.

It is similar with the swimming reflex: "It probably belongs to the behavioral reactions that are very, very deeply anchored in us," says Muth. Because there is hardly any wild animal that cannot keep afloat. “Even a cat, who is known to not particularly like water, can swim anyway.” The paddling and rowing movements of the babies are probably a legacy of our animal ancestors and are also unconscious. However, they are also lost again after infancy, as the doctor explains.

Water on your face slows your heartbeat

It is different with the actual diving reflex: "We all have that - even as adults," says Muth. It occurs in all warm-blooded animals and is particularly pronounced in marine mammals and other animals living and hunting in the water. The diving reflex ensures that our heartbeat slows down when our face gets underwater. “This is triggered by receptors on the right and left of the nose and in the forehead,” explains the anesthetist. These react to cold and wet. "That's why people used to treat acute palpitations by asking patients to dip their face in a bowl of ice water," says Muth. The diving reflex made the patients' heartbeat drop and thereby helped them.

The unconscious reaction of our body to water in the face can even be trained if one is frequently in the water: apnea divers, for example, make use of it because they use less oxygen with a slower heartbeat. "In trained apnea divers, the heartbeat can drop to just 17 beats per minute," says Muth. However, if diving goggles exactly cover the sensitive receptors on the face, the triggering signals no longer arrive correctly, and the diving reflex is then weaker.

In divers and marine mammals, the biological meaning of the diving reflex is obvious: They can stay under water longer without having to take a breath. "In principle, this is an oxygen-saving mechanism," explains the doctor. In our everyday life, this ability is certainly less important, but it can definitely save lives in an emergency. For example, it ensures that drowning people can survive longer in cold water without oxygen and thus survive longer. "In one case, a two and a half year old child was successfully resuscitated after being submerged in ice-cold water for 66 minutes," Muth reports. This is also thanks to the diving reflex and the greatly slowed heartbeat it causes.

11/12/2012 - NPO

November 12, 2012