Breath-Holding Risks and Shallow Water Blackout: Why Never in Water

Urgent first

Anyone motionless in the water is an emergency, even a strong swimmer who was fine seconds earlier. The American Red Cross says lifeguards are taught to respond quickly to any person who is motionless in the water for any reason, including loss of consciousness. [1] Alert a lifeguard and call emergency services (911 in the US). The UK Water Incident Research Hub lists a lack of purposeful movement over an extended period, and prolonged submersion, as warning signs. [2]

The clear rule

Never practice breath-holding, fast or deep breathing before it, or any breathing exercise in a bath, pool, lake, sea or other water. The American Red Cross, YMCA of the USA and USA Swimming say hyperventilation before underwater swimming and extended breath-holding in the water are "dangerous and potentially deadly activities." [1] This site gives no breath-holding instructions anywhere. That includes breath retention in yoga and breath-hold "challenges."

What the name means

"Shallow water blackout" is a common phrase, but those three groups do not endorse it, because water depth is not a factor in the body's response to hyperventilation and extended breath-holding. [1] They use the term hypoxic blackout. Hypoxia means low oxygen. A StatPearls review notes the older term is often misused as a synonym for drowning and says the condition can occur in any body of water at any depth. [3] The UK group agrees that it does not correlate with water depth. [2]

Who can be affected

The UK group lists three points under "Myths": it can occur in any depth of water, it can occur when stationary and submerged for long periods as well as while swimming, and it can occur in swimmers and non-swimmers of any level and ability. [2] It also lists repeated and rapid submersion and re-surfacing as a cause. [2]

What research found

Documented harm (case review). A CDC report on New York State found 16 drowning cases linked to what it called dangerous underwater breath-holding behaviors, 1988 to 2011. It describes two healthy young men who died at a swimming facility in 2011 after becoming unconscious underwater following intentional hyperventilation. [4] Practicing more than one such behavior increased the risk of fatality, in a small sample. [4] Evidence label: evidence of harm (case review, not a trial).

Physiology (laboratory study). In 18 volunteers with little freediving experience, 15 seconds of hyperventilation before each of five serial breath-holds lengthened the holds (133 vs 111 seconds) but lowered post-hold oxygen, and oxygen saturation fell lower by the last hold. [5] The authors say hyperventilation is considered a major risk factor for hypoxic blackout. [5] This shows why a longer hold is not a sign of safety: the body's urge to breathe is delayed, and oxygen is lower. Evidence label: physiological finding, small and conducted under supervision.

Safe limits. Proper evidence not found. In the Red Cross/YMCA/USA Swimming statement, the UK guidance, the CDC report, the StatPearls abstract and the lab study above, we found no safe breath-hold time, depth or routine for casual use, and we give none. What we checked: those four sources, the StatPearls abstract, and a PubMed search for hypoxic blackout.

What makes it more dangerous

The sources point to three things. Hyperventilating first is named as dangerous by the Red Cross, YMCA and USA Swimming. [1] Remaining submerged and largely stationary for long periods, and repeated and rapid submersion, are listed by the UK group as causes. [2] Repeated holds are a concern in the lab study, where oxygen fell further across a series of holds after hyperventilation. [5]

Other contexts

Breath-holding also appears in sports, social media trends and some breath practices. See freediving and breath-hold sports, breath-holding challenges and social media trends, Wim Hof-style breathing and water and kumbhaka and breath retention (a traditional term in pranayama, which has Indian roots and is described there in its own context). For the full safety map, see breathwork safety.