Pendulum breathing

A snorkeler in the water

In diving, pendulum breathing is the inhalation of air that has already been used and the resulting risk of unconsciousness due to a lack of oxygen . This effect usually occurs when a snorkel that is too long or too thick is used when diving or snorkeling . Due to this potential risk, which is mainly determined by the diver's lung volume, the dimensions of most snorkels are limited to 35 centimeters in length and 2.8 centimeters in diameter (smaller snorkels should be used for children) .These dimensions result in a volume of approx. 0 .25  liters of air , which is roughly half of a normal breath (0.5 liters) for an adult.

Emergence

With pendulum breathing, the exhaled air remains in the snorkel and, due to the length of the breathing tube, cannot be replaced with enough fresh air. With the next breath, the diver breathes in the used air again, the air "shuttles" back.

example

An adult person inhales and exhales on average a volume of 0.5 l per breath  . A snorkel with a length of 35  cm and a diameter of 2.8 cm contains a volume of about 0.25 l. In addition, there is a volume of around 0.15 to 0.2 l in the diver's airways. With each breath, only about 0.1 to 0.05 l are replaced by fresh air. About 0.4 to 0.45 l are pure pendulum volumes in which the oxygen content is steadily decreasing.

impact

The pendulum respiration already leads usually after a few breaths - by a lack of oxygen in the air we breathe - to unconsciousness. In the water, unconsciousness (without immediate rescue) can be fatal.

outlet valve

The problem of pendulum breathing can be solved by an outlet valve (" Y-piece ") with a side outlet , whereby the used air can be expelled directly. Under these circumstances, the breathing air in the snorkel would always be renewed as new air would be sucked in. However, an overly long snorkel has other disadvantages: The water pressure, which increases with depth, makes breathing difficult and leads to an accumulation of fluid in the lungs after just a few minutes. At a diving depth of two meters, the water pressure almost caused heart failure in a test person.

Individual evidence

1. ↑ ^{a b} snorkeling . Website of the Society for Diving and Hyperbaric Medicine , accessed July 1, 2012.
2. ↑ ^{a b c} Why is a snorkel not allowed to be more than 35 centimeters long when diving? Mareverlag, Hamburg, accessed on July 1, 2012, archived at web.archive.org .

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !