Divers deliberately breathing fast before diving into water

Question

I have seen a few divers who practiced breathing fast before a dive. What good does it do?

• Does deliberate/forced hyperventilation help to hold breathe over long time?
• Is there a connection in the same technique and Some breathing practices in yoga?

Answer 1

Divers do this in an attempt to saturate their blood with Oxygen before diving.

Voluntary hyperventilation before beginning voluntary apnea is commonly believed to allow the person involved to safely hold their breath for a longer period. In reality, it will give the impression that one does not need to breathe, while the body is actually experiencing a blood-oxygen level that would normally, and indirectly, invoke a strong dyspnea. Some have incorrectly attributed the effect of hyperventilation to increased oxygen in the blood, not realizing that it is actually due to a decrease in CO2 in the blood and lungs. Blood leaving the lungs is normally fully saturated with oxygen, so hyperventilation of normal air cannot increase the amount of oxygen available. Lowering the CO2 concentration increases the pH of the blood, thus increasing the time before the respiratory center becomes stimulated, as described above. While hyperventilation will yield slightly longer breath-holding times, any small time increase is at the expense of possible hypoxia. One using this method can suddenly lose consciousness—a shallow water blackout—as a result. If a person loses consciousness underwater, there is considerable danger that they will drown. An alert diving partner would be in the best position to rescue such a person. Static apnea blackout occurs at the surface when a motionless diver holds a breath long enough for the circulating oxygen to fall below that required for the brain to maintain consciousness. It involves no pressure changes in the body and is usually performed to enhance breath-hold time. It should never be practiced alone, but under strict safety protocols with a safety beside the diver.

Answer 2

For scuba diving this practice has no use. as you will be under water for a while and will be breathing compressed air from your cylinder.

In the old days people used this for free diving / skin diving /snorkeling to be able to hold breath for longer. I do not want to go into long discussions why this works, but in layman's terms it suppresses the bodies urge to breath by lowering the Carbon dioxide in the blood, which is the main trigger for breathing.

Hyperventilation is no longer considered safe even for free divers.