What Is DCI in Diving and What To Do About It

DCI in diving stands for decompression illness, a serious condition caused by harmful gas bubbles forming in the body when pressure changes too quickly during or after a dive. It is an umbrella term that includes both decompression sickness (DCS, often called “the bends”) and arterial gas embolism (AGE).

What Is DCI in Diving?

Decompression illness happens when the pressure around a diver drops too fast, such as during a rapid ascent, causing dissolved inert gas (mainly nitrogen) to come out of solution and form bubbles in tissues and blood. These bubbles can damage joints, nerves, the spinal cord, lungs, and other organs, leading to a wide range of symptoms from joint pain to paralysis or unconsciousness.

The term DCI is used because, in real-world diving, it can be difficult to distinguish between decompression sickness and arterial gas embolism at the scene. Both conditions share overlapping symptoms and are treated in similar ways in the emergency phase, especially with oxygen and recompression therapy.

Decompression Sickness vs. Arterial Gas Embolism

Decompression Sickness (DCS)

Decompression sickness occurs when nitrogen absorbed at depth forms bubbles as a diver ascends and pressure decreases. These bubbles can lodge in joints, soft tissue, or the nervous system, disrupting blood flow and normal function.

Common features of DCS include:

• Deep, aching joint or limb pain (“the bends”), often in shoulders, elbows, knees, or hips.
• Numbness, tingling, or weakness in arms or legs.
• Difficulty walking, balance problems, or coordination issues.
• Extreme fatigue, headache, dizziness, or feeling unusually weak.
• Skin changes like a marbled rash or itching.

Arterial Gas Embolism (AGE)

Arterial gas embolism usually results from lung overexpansion during ascent, often due to holding the breath or a rapid, uncontrolled ascent. Expanding air can damage the lungs and force gas bubbles into the arterial circulation, where they can block blood flow to the brain or other vital organs.

AGE tends to present suddenly and dramatically. Typical signs can include:

• Sudden loss of consciousness during or shortly after ascent.
• Stroke‑like symptoms: confusion, slurred speech, vision problems, or weakness on one side of the body.
• Seizures or convulsions.
• Chest pain, difficulty breathing, or coughing up frothy or bloody sputum.

Typical Causes and Risk Factors for DCI

DCI is most often related to how a dive is planned and executed, but individual factors also play a role. Key contributors include:

• Rapid ascent or uncontrolled buoyancy.
• Skipping safety stops or required decompression stops.
• Exceeding no‑decompression limits or pushing dive computers close to zero NDL.
• Doing multiple deep or long dives with short surface intervals.
• Diving in cold water, strong currents, or conditions causing heavy exertion.
• Dehydration, fatigue, illness, or poor physical condition.
• Flying or traveling to altitude too soon after diving.

While no diver can reduce risk to zero, understanding these factors helps keep DCI risk as low as reasonably possible.

Signs and Symptoms of DCI You Should Never Ignore

DCI can appear within minutes of surfacing or be delayed for several hours; most cases show up within the first 24 hours after a dive. Early recognition is critical for a good outcome.

Warning signs include:

• Persistent joint, muscle, or back pain after a dive.
• Tingling, numbness, “pins and needles,” or unusual sensations in limbs.
• Muscle weakness, difficulty standing, walking, or coordinating movements.
• Severe fatigue or an overwhelming sense of malaise out of proportion to the dive.
• Dizziness, vertigo, nausea, or balance disturbances.
• Changes in vision, hearing, speech, or mental clarity.
• Chest pain, shortness of breath, or breathing difficulties.
• Skin marbling or mottling, localized redness, or unusual rashes.
• Sudden collapse, unconsciousness, or seizure.

Any of these symptoms occurring after a dive should be treated as potentially dive‑related until proven otherwise by a medical professional.

What To Do If You Suspect DCI

If you or your buddy show possible signs of decompression illness, treat it as an emergency. Time matters because prompt treatment greatly improves outcomes.

Immediate First Aid Steps

1. Stop diving immediately
   Terminate further dives for that day and following days until cleared by a dive‑medicine professional.

2. Lay the diver flat and keep them still
   Place the diver in a comfortable, horizontal position unless vomiting or breathing problems require a different posture to protect the airway, and limit movement to reduce bubble circulation.

3. Administer 100% oxygen if available
   Use a well‑fitted mask connected to an oxygen source; high‑concentration oxygen helps wash out inert gas and reduces bubble size.

4. Monitor breathing and consciousness
   Check airway, breathing, and circulation regularly and be prepared to start CPR if the diver stops breathing or loses a pulse, following your training.

5. Keep the diver warm and hydrated (if conscious)
   Prevent chilling with blankets or dry clothing, and offer small sips of fluids if fully alert and not nauseated, avoiding alcohol or sedatives.

6. Do NOT attempt in‑water recompression
   Never return a symptomatic diver to depth in an attempt to “recompress” them in open water, as unsupervised in‑water recompression is dangerous and can be fatal.

Who To Call and Where To Go

• Activate local emergency medical services as soon as possible so transport and hospital care can be arranged quickly.
• Contact a dive‑medicine hotline or hyperbaric advice line for guidance, especially in remote locations.
• Get to a medical facility capable of coordinating transfer to a hyperbaric chamber, providing dive profile details and symptom timing.

Definitive Treatment

Most confirmed cases of DCI are treated with recompression therapy in a hyperbaric chamber, often using standardized oxygen treatment tables. Inside the chamber, the diver is re‑pressurized and given high‑concentration oxygen to shrink bubbles and restore blood flow. Early recompression significantly improves outcomes and reduces the risk of long‑term damage.

How To Prevent DCI in Recreational Diving

While DCI can never be completely eliminated, divers can greatly reduce the risk with disciplined habits and conservative planning.

Plan Conservatively

• Stay well within no‑decompression limits (NDL) rather than riding them to zero.
• Use your dive computer’s planning mode or dive tables to set maximum depth and bottom time.
• For multiple dives in a day, plan shallower second and third dives and build in generous surface intervals.

Ascend Slowly and Control Buoyancy

• Maintain a slow ascent rate, following agency or computer recommendations to limit bubble formation.
• Keep your buoyancy under control with small BCD adjustments, especially in the last 10 metres where expansion is greatest.
• Avoid “yo‑yo profiles” with repeated up‑and‑down depth changes during a dive.

Always Do a Safety Stop

• Make a 3–5 minute safety stop at around 3–5 metres (10–15 feet) at the end of every dive, even when your computer shows plenty of remaining NDL.
• Treat the safety stop as a standard part of your dive, not an optional extra.

Respect Surface Intervals and No‑Fly Times

• Allow adequate surface intervals to off‑gas nitrogen between dives; longer intervals add margin.
• Follow recommended no‑fly times before taking a flight or traveling to altitude after diving, and extend them after deep or repetitive diving.

Look After Your Health

• Stay well hydrated before and after diving, avoiding heavy alcohol use and excessive caffeine.
• Dive within your fitness level, and avoid diving when ill, exhausted, or congested.
• Dress appropriately for thermal protection, because being cold at depth may increase risk.

Dive Within Training and Conditions

• Stay within the limits of your certification level and experience.
• Avoid intentional decompression dives unless you have specific training and equipment.
• Take advanced and specialty courses (deep, nitrox, buoyancy, rescue) to improve skills and safety awareness.

Key Takeaways

DCI (decompression illness) is a collective term for decompression sickness and arterial gas embolism in diving, both caused by gas bubbles forming or moving in the body due to rapid pressure changes. Suspected DCI is a medical emergency: stop diving, provide 100% oxygen if available, keep the diver lying flat and warm, and seek urgent professional help and hyperbaric evaluation. Conservative dive planning, slow ascents, safety stops, appropriate surface intervals, and good overall health dramatically reduce the risk and help divers explore the underwater world more safely.