DCS, Barotrauma, and Hyperbaric Emergency Management

Why Hyperbaric Emergencies Matter in Aquaculture Diving

Aquaculture and marine science divers regularly perform repetitive dives at working sites — inspecting net pens, collecting samples, cleaning fouling from structures — often far from the nearest hospital or recompression chamber. Recognizing a hyperbaric emergency quickly and applying correct first aid can mean the difference between full recovery and permanent injury or death. This lesson covers three critical conditions: Decompression Sickness Type I, Decompression Sickness Type II, and Arterial Gas Embolism (AGE).

Decompression Sickness: What It Is

Decompression sickness (DCS) occurs when dissolved inert gas (primarily nitrogen) comes out of solution in the body's tissues or blood because ascent was too rapid. Bubbles form and cause mechanical damage and inflammatory responses. DCS is divided into two types based on which body systems are affected.

DCS Type I — Musculoskeletal and Skin

Type I DCS involves the joints, limbs, and skin. Classic symptoms include:

• Joint and limb pain (historically called "the bends") — typically a deep, aching pain in the shoulders, elbows, hips, or knees
• Skin mottling (cutis marmorata) — a blotchy, marbled rash that may itch or burn
• Localized swelling or fatigue in the limbs

Type I symptoms are serious but not immediately life-threatening. They still require 100% oxygen first aid and medical evaluation. Never dismiss joint pain after a dive as simple muscle soreness.

DCS Type II — Neurological, Pulmonary, and Systemic

Type II DCS involves the central nervous system, spinal cord, inner ear, or lungs. It is a true emergency. Symptoms include:

• Neurological signs: numbness, tingling, weakness or paralysis (especially in the lower body), confusion, difficulty speaking, loss of bladder or bowel control
• Inner-ear (vestibular) symptoms: vertigo, nausea, vomiting, hearing loss
• Pulmonary ("the chokes"): substernal chest pain, shortness of breath, dry cough — indicates bubbles in the pulmonary circulation
• Unconsciousness or altered mental status

Spinal cord involvement is particularly common in Type II DCS and can produce paraplegia if untreated.

Arterial Gas Embolism (AGE)

AGE is caused by pulmonary barotrauma — air trapped in the lungs during an overly rapid ascent ruptures alveoli and enters the pulmonary veins. Bubbles travel to the arterial circulation and can reach the brain (cerebral AGE) or coronary arteries within seconds.

Key distinguishing features of AGE:

• Onset is sudden and immediate, typically within 10 minutes of surfacing (often within 1–2 minutes)
• Loss of consciousness on or immediately after surfacing
• Focal neurological deficits: sudden weakness, facial drooping, visual disturbance, seizure
• May be preceded by no warning symptoms at all

AGE must be distinguished from Type II DCS: AGE onset is dramatically faster and is caused by breath-holding or air trapping on ascent, not by inadequate decompression. However, in the field, the first-aid treatment is identical for both.

First-Aid Protocol: The Same Starting Point

For all suspected DCS (Type I or II) and AGE, apply this sequence:

1. Remove the diver from the water and place on a flat, stable surface.

2. Assess responsiveness and airway. Call EMS (911) immediately for any Type II or AGE presentation. For Type I, EMS should still be notified.

3. Administer 100% oxygen via a demand-valve or non-rebreather mask as soon as possible and continue without interruption. Oxygen accelerates the elimination of nitrogen bubbles and is the single most important first-aid measure.

4. Positioning: Lay the diver flat (supine). Current DAN guidance does not recommend the head-down (Trendelenburg) position. Keep the diver still and warm.

5. Do not allow re-immersion for further decompression — this is dangerous and not recommended.

6. Keep the diver hydrated if conscious and able to swallow — plain water or oral rehydration fluids; no alcohol.

7. Contact DAN (Divers Alert Network) emergency hotline for physician guidance and assistance locating the nearest recompression chamber.

8. Document everything: dive profile, symptom onset time, oxygen delivery time, and diver's condition. Complete a DAN Accident Report form.

Chamber Referral Pathway

Recompression in a hyperbaric oxygen chamber is the definitive treatment for DCS and AGE. The referral pathway at a remote aquaculture site typically works as follows:

1. Call EMS (911) and the DAN emergency line.

2. DAN physicians can advise on whether air or ground transport is appropriate and help identify the nearest operational chamber.

3. Continue oxygen throughout transport.

4. Provide the receiving facility with the written accident documentation.

Do not delay oxygen and EMS contact while debating whether symptoms are "serious enough." When in doubt, treat and refer.

Safety Reminders

• Always have a functioning oxygen unit, demand valve, and non-rebreather mask on site before any dive operation.
• PPE during oxygen delivery includes nitrile gloves; ensure no ignition sources near oxygen equipment.
• Oxygen units must be inspected before each dive day.
• Know the DAN emergency number before you enter the water — post it at the dive station.
• Document every dive with a dive log; this information is critical for medical personnel.