Understanding Decompression Illness (DCI):
DCS, AGE, and the Role of PFO

What Is Decompression Illness?

Decompression illness (DCI) is a general term used to describe two potentially serious diving-related conditions:

• Decompression Sickness (DCS), often called "the bends"
• Arterial Gas Embolism (AGE)

Both result from gases coming out of solution inside the body due to pressure changes, but they have different mechanisms and symptoms. DCI is the term often used in emergency medicine and dive safety training to capture both conditions under one umbrella.

What to Do First: The Treatment Is the Same

Don’t worry about whether it’s DCS or AGE because the initial treatment is exactly the same. Do it immediately. Worry about the diagnosis later.

1. Administer 100 percent oxygen as soon as symptoms appear
2. Stop diving and keep the diver calm and still
3. Lay the diver flat unless they are struggling to breathe
4. Hydrate, if the diver is conscious and can safely swallow
5. Contact emergency services or DAN and get the diver to a hyperbaric chamber as quickly as possible

This is the same approach whether they have joint pain, tingling, paralysis, or collapse at the surface. Early oxygen and fast transport are your best chance to prevent lasting injury.

Decompression Sickness (DCS)

DCS occurs when inert gas (mostly nitrogen) absorbed into tissues under pressure forms bubbles during or after ascent. These bubbles can cause local tissue damage, inflammation, and interference with blood flow.

Common Causes

• Inadequate or skipped decompression
• Rapid ascents
• Long or deep dives
• Repetitive dives with inadequate surface intervals

Symptoms

• Joint or muscle pain
• Dizziness or vertigo
• Fatigue or weakness
• Skin rashes or marbling (cutis marmorata)
• Neurological symptoms (numbness, tingling, confusion)

Treatment

• Administer 100 percent oxygen immediately
• Begin hydration
• Evacuate to a hyperbaric facility for recompression therapy

Arterial Gas Embolism (AGE)

AGE is caused by gas bubbles entering the arterial bloodstream, typically due to lung overexpansion injuries during ascent. It is considered a more acute and immediately life-threatening form of DCI.

Common Causes

• Breath-holding during ascent
• Rapid uncontrolled ascent
• Lung conditions that trap air (asthma, bullae)

Symptoms (Often Sudden)

• Loss of consciousness
• Convulsions
• Visual disturbances
• Paralysis or weakness
• Chest pain or difficulty breathing

Treatment

• Immediate 100 percent oxygen
• Rapid transport to hyperbaric chamber
• Support airway and circulation if needed

Note: AGE can occur even in shallow water if a diver surfaces too quickly while holding their breath.

How a PFO Increases Your Risk

A patent foramen ovale (PFO) is a small hole between the right and left atria of the heart. In about 25 percent of adults, it never fully closes after birth.

Under normal conditions, venous gas bubbles are filtered out by the lungs. But with a PFO, bubbles can bypass the lungs and enter arterial circulation directly, increasing the risk of neurological DCS or stroke-like symptoms.

Key Points:

• You won’t know you have a PFO unless tested
• Most divers with PFOs never experience DCS
• PFO becomes more relevant in unexplained or repeated neurological DCS cases
• Closing a PFO is a personal and medical decision, not routine

Prevention Strategies

• Always ascend slowly and do your safety stop
• Dive within your limits and conservatively manage nitrogen loading
• Stay well-hydrated before and after diving
• Avoid strenuous activity immediately after diving
• Never hold your breath while ascending

Why This Matters for Recreational Divers

DCI is rare but serious. It can affect any diver, not just technical divers or those pushing the limits. Understanding the differences between DCS and AGE, and knowing how a PFO can complicate risk, makes you a more informed, safer diver.

You can follow every dive table, computer, and safety stop perfectly—and still get hit. These are called undeserved hits, and while they are uncommon, they do happen. Factors like hydration, exertion, temperature, microbubbles, or undiagnosed medical conditions (like a PFO) may contribute.

That’s why it matters who you dive with and how prepared you are:

• Dive with teammates trained in rescue and emergency oxygen administration
• Get trained yourself in rescue skills and first aid
• Carry DAN dive accident insurance, especially if traveling or diving in remote areas