Decompression Sickness (DCS) is a medical condition affecting individuals experiencing rapid pressure changes. It occurs when dissolved inert gases, primarily nitrogen, form bubbles in the body as pressure reduces too quickly. While commonly associated with underwater diving, DCS can also arise from depressurization situations like emerging from a pressurized environment or ascending to high altitudes.
Understanding Decompression Sickness
During a dive, as a person descends, increased surrounding pressure causes more nitrogen from their breathing gas to dissolve in tissues and blood. The deeper and longer the dive, the more nitrogen is absorbed.
When a diver ascends, ambient pressure decreases, and dissolved nitrogen begins to come out of solution. If this pressure reduction happens too rapidly, nitrogen forms bubbles in tissues and blood. These bubbles can cause damage by blocking blood vessels, compressing tissues, or triggering inflammatory responses. An excessive number or size of bubbles leads to the various manifestations of DCS.
Key Factors Influencing Risk
DCS risk results from a complex interaction of factors: dive depth, duration (bottom time), and ascent rate. Deeper dives and longer bottom times allow for greater inert gas absorption, increasing the gas load for elimination during ascent.
A rapid ascent rate is a primary contributor to bubble formation. If pressure decreases too quickly, dissolved nitrogen lacks time to be safely exhaled, leading to bubble formation. Repetitive dives within a short timeframe also increase risk, as residual nitrogen accumulates, adding to the gas load for subsequent dives. This means a diver might be at higher risk on a shallower second dive with insufficient surface interval time.
Beyond dive profile, individual physiological and environmental factors influence susceptibility. Cold water increases DCS risk by reducing blood flow, affecting gas elimination. Dehydration reduces blood plasma volume, impairing the body’s ability to off-gas nitrogen and making bubble formation more likely. Other factors include age, higher body fat (nitrogen is more soluble in fat), strenuous exercise during or immediately after a dive, and certain pre-existing medical conditions like a patent foramen ovale (PFO).
Preventing Decompression Sickness
DCS prevention involves careful planning and adherence to safety protocols. Dive planning is foundational, determining maximum depth, bottom time, and ascent profile before entering the water. Sticking to these limits, especially “no-decompression limits” (NDLs), allows divers to ascend directly to the surface without mandatory decompression stops.
Dive tables and computers are essential tools for managing nitrogen absorption and elimination. Tables outline safe depth and time limits, while computers continuously monitor depth and time, calculating real-time nitrogen loading and providing personalized no-decompression limits and ascent guidance. A slow, controlled ascent rate is crucial, typically no faster than recommended, to allow nitrogen to exit the body safely.
Incorporating safety stops is another important preventative measure. A safety stop usually involves pausing for three to five minutes at a shallow depth (around 15 feet/5 meters) near the end of a dive. This pause allows additional dissolved nitrogen to off-gas before surfacing. Maintaining good hydration by drinking plenty of water and avoiding alcohol and caffeine before and after diving helps circulation and gas elimination. Avoiding strenuous physical activity immediately after a dive also reduces bubble formation and movement.
Recognizing and Responding to Decompression Sickness
Recognizing DCS symptoms is crucial for prompt response and effective treatment. Symptoms vary widely depending on bubble location and size, appearing immediately or delayed by several hours (90% within six hours). Common manifestations include joint pain, often described as a deep ache, giving DCS its common name “the bends.” Other symptoms can include numbness, tingling, muscle weakness, skin rash or mottling, and extreme fatigue.
More severe symptoms, indicating central nervous system involvement, include dizziness, headache, vision disturbances, coordination or balance difficulties, confusion, or even paralysis. Respiratory symptoms like shortness of breath or chest pain can occur in rare but serious cases. Any unusual symptom after a dive should prompt suspicion of DCS.
Immediate first aid for suspected DCS involves administering 100% oxygen, if available, using a tight-fitting mask. Laying the affected individual down and keeping them horizontal helps manage the condition; providing fluids aids recovery. Seek immediate medical attention, contacting emergency medical services and alerting them to a possible diving-related injury. Definitive treatment is recompression therapy in a hyperbaric chamber. Inside, pressure increases, causing nitrogen bubbles to shrink and redissolve, while breathing pure oxygen helps eliminate inert gas. Prompt recompression therapy significantly improves chances of full recovery.