Skip breathing is a dangerous technique used in extreme breath-holding activities, such as competitive freediving, to override the body’s natural signals to inhale. This respiratory manipulation aims to artificially extend the duration a person can remain underwater on a single breath. The technique attempts to delay the intense discomfort and diaphragm contractions that signal the body’s need to breathe. This manipulation, however, masks a rapidly dropping oxygen level, making it extremely hazardous.
Physiological Manipulation of the Urge to Breathe
The body’s urge to take a breath is triggered primarily by the buildup of carbon dioxide (CO2) in the bloodstream, not by low oxygen levels. As the body metabolizes oxygen, it produces CO2, which dissolves in the blood and lowers its pH. Chemoreceptors in the brain and arteries detect this rise in acidity, signaling the respiratory center to initiate breathing.
Skip breathing attempts to exploit this CO2 drive by performing a minimal, controlled exchange of air, sometimes called a “mini-breath.” This small exhalation and subsequent partial inhalation vents a fraction of the accumulated CO2 from the lungs. By slightly lowering the CO2 partial pressure, the technique temporarily reduces the acidic stimulus on the chemoreceptors, effectively “resetting” the urge to breathe. While this action momentarily lowers CO2, it does not replenish a significant amount of oxygen (O2).
The Goal of Extending Breath-Hold Duration
The intent behind skip breathing is to extend the total time spent underwater, often called “bottom time.” This practice is typically sought by freedivers or spearfishermen who want to maximize their time at depth for competitive or hunting purposes. The delayed urge to breathe allows the diver to push past the involuntary contractions of the diaphragm, which signal the end of a safe breath-hold. By temporarily suppressing the CO2 warning, the diver gains a short window to continue their activity. This focus on extending performance relies on ignoring the body’s safety mechanism, leading to a false sense of security regarding oxygen saturation.
Critical Dangers of Hypoxia and Blackout
The most severe consequence of skip breathing is that it actively masks the onset of severe hypoxia—a dangerously low level of oxygen in the body’s tissues. By removing the CO2 warning signal, the technique allows the diver to continue the breath-hold until the O2 level in the blood drops below the threshold required to sustain consciousness. This leads directly to a hypoxic blackout, a sudden loss of consciousness caused by a lack of oxygen supply to the brain.
A particularly dangerous variant is Shallow Water Blackout (SWB), which often occurs during the ascent phase of a dive. As the diver rises, ambient water pressure rapidly decreases, causing the partial pressure of oxygen in the lungs to drop significantly. This rapid depressurization causes the already low oxygen concentration to fall below the critical level for consciousness just before or as the diver reaches the surface. Since the diver is unconscious, they cannot initiate a recovery breath, and drowning becomes the most common outcome. Skip breathing is strongly discouraged by all major freediving and safety organizations.