Holding one’s breath is a common action, whether done playfully, during a swimming session, or in focused activities like freediving. While a brief period of breath-holding is generally harmless, prolonged breath-holding can lead to a dangerous lack of oxygen to the brain, potentially causing damage.
The Body’s Response to Breath Holding
When a person holds their breath, several immediate physiological changes occur. The primary trigger for the urge to breathe is not a lack of oxygen but rather an increase in carbon dioxide (CO2) levels in the blood. As CO2 accumulates, it makes the blood more acidic, which is detected by chemoreceptors in the brain and blood vessels, signaling the respiratory system to inhale.
During breath-holding, oxygen levels in the blood gradually decrease as the body continues to use it for cellular functions. Simultaneously, carbon dioxide levels rise. The body may also activate the mammalian dive reflex, a natural response that slows the heart rate and constricts blood vessels in the limbs to preserve oxygen for vital organs. This reflex helps extend breath-hold time, but it does not eliminate the eventual need for oxygen.
How Oxygen Deprivation Harms the Brain
The brain is highly sensitive to any reduction in oxygen supply due to its continuous and high energy demands. When oxygen levels to the brain are reduced, the condition is called hypoxia; a complete absence of oxygen is known as anoxia. Brain cells, particularly neurons, require a constant and uninterrupted supply of oxygen to function properly and generate energy.
Without sufficient oxygen, brain cells cannot produce enough energy to maintain their normal processes. This energy failure disrupts the delicate balance of ions within the cells, leading to a buildup of toxic substances and the release of excitatory neurotransmitters that can overstimulate and damage neurons. Prolonged oxygen deprivation causes neuronal cell death, which can result in permanent brain injury. The extent of damage depends on the severity and duration of oxygen deprivation.
High-Risk Breath-Holding Scenarios
Certain situations increase the risk of brain injury from breath-holding. One particularly dangerous practice is hyperventilation before holding one’s breath. Hyperventilation, or rapid and deep breathing, artificially lowers carbon dioxide levels in the blood. This delays the body’s natural urge to breathe, allowing oxygen levels to drop to dangerously low levels without warning, increasing the risk of losing consciousness.
Shallow water blackout is a serious consequence that can occur during underwater activities, such as swimming or freediving, when a person loses consciousness due to oxygen deprivation. This often happens after hyperventilating, as the delayed urge to breathe allows individuals to remain underwater until their oxygen levels become critically low, leading to fainting and potential drowning. Competitive freediving also carries inherent risks, as participants push their physiological limits, making them susceptible to hypoxic blackouts due to extreme oxygen depletion and pressure changes during ascent.
Recognizing Brain Injury Symptoms
Recognizing signs of brain injury due to oxygen deprivation is important. If someone experiences a significant lack of oxygen to the brain, they may lose consciousness, often within 15 seconds. Other immediate symptoms can include confusion, disorientation, and slurred speech.
Physical signs such as a bluish or grayish tint to the lips or face (cyanosis) may also be present, indicating inadequate oxygenation. Seizures are another possible symptom. If any of these symptoms are observed after a breath-holding incident, immediate medical attention is necessary.