DCS: THE REASON FOR ALL DECOMPRESSION THEORY
Introduction
When we talk about different decompression models, gradient factors, and dive profiles, it’s always about minimizing our risk as much as possible. Unfortunately, despite all precautions, there will always be cases where a dive ends with DCS.
In the section on human factors and the stigma surrounding DCS, we show in more detail why it’s so important to simply accept DCS as a sports injury. This section is primarily about recognizing the symptoms and responding correctly.
Before we start, first test your knowledge: Can you distinguish what’s fact and what’s dive folklore?
What is DCS?
Decompression sickness (DCS) describes a group of symptoms that can occur when dissolved inert gases—usually nitrogen—cannot be eliminated from the body quickly enough during ascent at the end of a dive. As we descend, nitrogen dissolves in tissue according to ambient pressure. During ascent, this gas must be released again. If this happens too quickly or incompletely, bubbles can form. These bubbles disrupt normal body function, irritate tissue and vessels, and depending on their location and size, can cause symptoms ranging from discomfort to life-threatening conditions.
What’s important: DCS is rare, but not “impossible.” It can also occur on dives that are completely within table or computer limits. Therefore, this section is not about creating fear, but about conveying a clear, objective picture: DCS is a rare but serious sports injury that one should be able to recognize and treat.
Simon Mitchell: Decompression Illness - a comprehensive overview
Detailed and clearly written overview of decompression illness
How does DCS develop?
To understand the development of DCS, it helps to look at gas transport in the body. During descent, ambient pressure increases, and nitrogen dissolves increasingly in the blood and tissues. The speed of this uptake depends on factors such as perfusion and tissue type: highly perfused organs saturate faster, fatty tissue somewhat slower, and poorly perfused areas like bones very slowly.
During ascent, ambient pressure decreases again. The tissue becomes “supersaturated”—the risk of bubble formation increases. Normally, nitrogen is transported in a controlled manner via the blood to the lungs and exhaled. However, if the ascent is too fast or supersaturation too great, the gas cannot remain completely in solution and bubbles form in the blood or in supersaturated tissue. These can enlarge, coalesce, and cause problems in tissue or vessels.
Although bubbles play a prominent role in the development of DCS, the exact interaction between bubbles and other factors is not fully understood. Different people can have different numbers of bubbles after the same dive; the same person can react differently on two different days. The only certainty is: More bubbles statistically mean a higher risk of DCS.
Symptoms of DCS
Decompression sickness (DCS) can present very differently. Some affected individuals have only mild, nonspecific symptoms, while others develop life-threatening deficits within minutes. This makes it difficult to draw the right conclusions early on. Therefore, in dive medicine the rule is: better to react too cautiously once than to overlook a serious sign.
Why the symptoms are so varied
The cause of DCS is gas bubbles that form in the body after a dive. Depending on where these bubbles accumulate, different symptoms arise: at joints you feel pain, on the skin a typical pattern appears, in the nervous system paralysis or altered consciousness can occur. Symptoms often appear within the first hour after surfacing, but they can also develop only after many hours—up to 24 hours are documented.
Typical key symptoms
- Neurological: Dizziness, staggering, unsteady gait, sensory disturbances (tingling, numbness), weakness in arms or legs, confusion, visual disturbances, headaches, seizures.
These symptoms are always serious—even if they seem mild. - Skin: Itching, redness, or marbled, painfully swollen skin. These signs often seem harmless but can indicate deeper problems.
- Musculoskeletal: Joint pain (“the bends”) is the classic but not the most dangerous form. It often occurs in episodes, can migrate, or persist at rest.
- Cardiovascular and respiratory: Chest pain, shortness of breath, cough, rapid heartbeat, or dizziness from circulatory problems. These signs can be life-threatening—even if they are mistaken for a heart attack or asthma.
- General: Fatigue, unusual tiredness, nausea, or vomiting. These symptoms are nonspecific but deserve increased attention after a dive.
Risk of confusion
Not everything that occurs after a dive is automatically DCS. Some symptoms have other causes:
- Sunburn: red patches on the skin located exactly where the sun has acted.
- Gastrointestinal problems: Diarrhea or nausea can also be infectious or diet-related.
- Pre-existing conditions: Chronic joint pain or old injuries did not suddenly arise from a dive.
- Fatigue: can simply be normal exhaustion after exertion.
Nevertheless, the rule is: Better to get it checked out. Especially neurological signs or unusual combinations should be taken seriously.
First Aid for DCS
We’ve already seen that the symptoms of DCS can be quite varied. If someone doesn’t feel well after diving, you should always consider DCS—but without losing sight of other health problems.
What distinguishes first aid for a diving accident from general first aid are two things:
Oxygen: If there is even the slightest suspicion that it could be a diving accident, oxygen should always be administered.
Dive medicine hotline: Since emergency services extremely rarely deal with diving accidents, you should always involve one of the dive insurance hotlines. Even if the patient is not insured there, you will receive expert advice. If the insurance is to pay, it must even be notified as soon as possible—life-threatening emergencies take priority, of course.
Oxygen and DCS
Blog article on why oxygen is so important in diving accidents
5-Minute Neuro Check
Is everything still normal, or is someone showing neurological abnormalities? You can test this with this tool.
What to do in a diving accident or suspected DCS?
Not everything that happens after diving is immediately an emergency. Managing symptoms should follow a graduated approach, which also forms the basis for our traffic light quiz:
- Red: Life-threatening or severe neurological signs, acute shortness of breath, chest pain.
→ Give O₂ and immediately call 112. Hotline can additionally be involved. - Yellow: Suspicious but not acutely threatening symptoms (e.g., skin marbling, tingling, dizziness).
→ Give O₂, monitor closely, and call hotline. The hotline coordinates further steps if needed. - Green: Probably not dive-related (e.g., sunburn, simple fatigue).
→ Monitor. Hotline only if uncertain.
Key takeaway
“Any unusual symptom after a dive is suspicious—better one too many oxygen administrations and one too many calls than one too few.”
