Recognizing Decompression Illness: Symptoms and First Response
What "decompression illness" covers
Decompression illness (DCI) is the umbrella term for two related conditions. Decompression sickness (DCS) — "the bends" — happens when dissolved inert gas forms bubbles in tissues and blood as pressure drops. Arterial gas embolism (AGE) happens when expanding gas injures the lung and forces bubbles into arterial circulation, most classically after a breath-hold ascent. Divers Alert Network's overview of DCI treats them together because the field response is essentially the same. The clinical detail behind the classifications is laid out in the StatPearls article on decompression sickness, a peer-reviewed reference on the National Library of Medicine's bookshelf.
What symptoms actually look like
The textbook image of DCS is dramatic joint pain. The reality is often subtler, which is exactly why cases get missed:
- Pain, classically in or near joints — shoulders and elbows frequently
- Numbness, tingling, or patchy weakness, sometimes migrating
- Unusual, disproportionate fatigue after a dive
- Skin symptoms — itching or a marbled rash
- Dizziness, balance problems, ringing in the ears
- In serious cases: difficulty walking, confusion, trouble breathing, loss of consciousness
Most symptoms appear within hours of surfacing, though onset can be delayed — including after a flight home, as covered in our guide on flying after diving. The single most dangerous habit in recreational diving is explaining symptoms away: "I slept wrong," "I hauled tanks all day," "it's probably nothing." The StatPearls reference notes that presentations range widely in severity, and mild early symptoms do not guarantee a mild course.
The standard first response
Per DAN's guidance, the field response to suspected DCI is straightforward and worth memorizing before the trip, not during the emergency:
- Stop diving immediately. No "one more dive to see how it feels."
- Provide the highest available concentration of oxygen to a breathing, conscious diver — this is the cornerstone of dive first aid.
- Keep the diver lying down and comfortable; monitor closely.
- Activate emergency services and contact the DAN emergency hotline, which coordinates dive-injury evaluation and referral around the clock.
- Do not attempt in-water recompression. Definitive treatment is hyperbaric oxygen therapy in a chamber, delivered under medical supervision — the treatment side of the field is the domain of the Undersea & Hyperbaric Medical Society, the professional society for diving and hyperbaric medicine.
Prepare before you need it
Two items belong in every dive-trip plan: knowing where emergency oxygen is available at your dive site, and having the DAN emergency number saved in your phone and written in your logbook. Our Pre-Dive Readiness Checklist includes both, because emergency information you have to look up mid-crisis is barely information at all.
This page is reviewed reference material summarizing what the cited organizations publish. It is not medical advice or a substitute for emergency care — a diver with suspected DCI needs professional evaluation, full stop.