Nitrogen narcosis is caused by the increased partial pressure of nitrogen gas in the body when a person breathes compressed air at depth underwater. As a diver descends, the pressure around them rises, causing more nitrogen from the breathing gas to dissolve into their blood and tissues. This excess dissolved nitrogen affects the nervous system, particularly the brain, leading to a narcotic or intoxicating effect similar to alcohol intoxication.
At normal atmospheric pressure, nitrogen is an inert gas that does not affect brain function. However, under high pressure, such as at depths greater than about 10 meters (33 feet), nitrogen molecules interfere with the way nerve cells communicate. The exact mechanism is complex but involves nitrogen dissolving into the lipid membranes of nerve cells and altering the function of ion channels and neurotransmitter receptors. This disruption slows down brain activity and impairs cognitive and motor functions.
The symptoms of nitrogen narcosis typically start with a feeling of light-headedness, euphoria, and reduced attention. As pressure increases with depth, these symptoms can escalate to confusion, poor judgment, slowed reaction times, numbness, and emotional instability. In severe cases, a diver may experience hallucinations, panic, or unconsciousness. The effects vary widely between individuals; some divers feel symptoms at relatively shallow depths, while others tolerate much deeper dives without noticeable effects.
Because nitrogen narcosis impairs judgment and coordination, it poses a significant risk during diving. A diver under its influence might make dangerous decisions, such as ascending too quickly or failing to monitor air supply, which can lead to serious injury or death. Fortunately, the condition is reversible—once the diver ascends to shallower depths and the pressure decreases, the excess nitrogen leaves the tissues, and normal brain function returns without lasting damage.
To reduce the risk of nitrogen narcosis on deep dives, divers often use breathing gas mixtures where nitrogen is partially or fully replaced by helium, which is less narcotic due to its lower solubility in body tissues. This approach allows divers to go deeper with less risk of narcosis.
In summary, nitrogen narcosis is caused by the increased pressure underwater causing nitrogen to dissolve in the nervous system, disrupting brain function and producing intoxicating effects that impair a diver’s mental and physical abilities. The severity depends on depth, individual susceptibility, and the gas mixture breathed.
