Scuba Diving Overexpansion Injuries

These injuries occur when gases in the body or equipment expand due to pressure changes, typically during ascent, and can have serious consequences if not managed properly. This reflects current understanding and safety practices as of March 15, 2025.

Overexpansion injuries, often called pulmonary barotrauma or “lung overexpansion injuries,” result from gas expanding in enclosed spaces as pressure decreases during ascent. They’re among the most dangerous scuba-related injuries, but they’re preventable with proper technique. Here’s what you need to know.

What Are Overexpansion Injuries?

1. Definition

Occur when gas trapped in the lungs or other airspaces expands beyond their capacity as ambient pressure drops (Boyle’s Law: volume increases as pressure decreases).
Most common during rapid or uncontrolled ascents when divers hold their breath or ascend too quickly.

2. Types

Pulmonary Overexpansion (Lung Barotrauma):
- Alveoli (lung air sacs) rupture, releasing gas into surrounding tissues or bloodstream.
- Subtypes:
  - Pneumothorax: Collapsed lung from gas in the chest cavity.
  - Mediastinal Emphysema: Gas in the chest around the heart/lungs.
  - Subcutaneous Emphysema: Gas under the skin, often around the neck/chest.
  - Arterial Gas Embolism (AGE): Gas bubbles enter arteries, blocking blood flow (e.g., to the brain)—life-threatening.
Other Overexpansion:
- Ear Barotrauma: Gas trapped in the middle ear expands, causing pain or rupture (less common on ascent).
- Sinus Barotrauma: Expanded gas in sinuses causes pain or bleeding.
- Equipment Overexpansion: BCD or drysuit overinflating, leading to rapid ascent.

Causes

1. Breath-Holding

Primary Cause: Holding your breath during ascent prevents gas from escaping the lungs as it expands.
Risk: Even a 3–6 ft (1–2 m) ascent can double lung volume if pressure halves (e.g., from 10 ft to surface).

2. Rapid Ascent

Speed: Ascending faster than 30 ft/min (9 m/min) outpaces safe gas venting, especially if distracted or panicking.
Uncontrolled Ascent: BCD overinflation or dropped weights can rocket you up, amplifying risk.

3. Pre-Existing Conditions

Lung Issues: Asthma, scarring, or obstructions (e.g., mucus) trap air, increasing susceptibility.
Smoking: Damaged lung tissue may rupture more easily.

4. Equipment Misuse

BCD/Drysuit: Adding too much air near the surface without venting causes uncontrolled buoyancy.

Symptoms

1. Pulmonary Overexpansion

Immediate: Chest pain, shortness of breath, coughing, or a “popping” sensation on ascent.
Pneumothorax: Sharp pain, uneven breathing, rapid heart rate.
Subcutaneous Emphysema: Crackling under skin, swollen neck, hoarse voice.
AGE: Stroke-like symptoms within minutes—dizziness, confusion, paralysis, unconsciousness.

2. Other Areas

Ear: Pain, fullness, or muffled hearing during ascent.
Sinus: Facial pain, nosebleeds, or pressure.

Prevention Techniques

1. Breathe Continuously

Golden Rule: Never hold your breath—exhale steadily during ascent, even if using an alternate regulator.
Practice: Maintain a slow, normal breathing pattern—humming or saying “ahh” keeps airways open.

2. Control Ascent Rate

Speed: Ascend no faster than 30 ft/min (9 m/min)—follow your smallest bubbles or dive computer.
Safety Stop: Pause at 15 ft (5 m) for 3–5 minutes to off-gas safely, even on no-deco dives.
Look Up: Watch for boats or obstacles, but don’t rush.

3. Manage Buoyancy

BCD: Vent air gradually as you rise—start with small bursts to avoid overcorrection.
Weights: Ensure proper weighting (e.g., 10–20 lbs based on wetsuit) to avoid sudden buoyancy shifts.
Drysuit: Release air via valves—practice on training dives.

4. Pre-Dive Health Check

Fitness: Avoid diving with colds, allergies, or lung conditions—consult a dive doctor if unsure.
Training: Review equalization and ascent techniques—refresh if rusty.

5. Equipment Maintenance

Regulator: Ensure it delivers air smoothly—service annually or per manufacturer guidelines.
BCD/Drysuit: Test inflators and dump valves pre-dive—fix sticky valves immediately.

What to Do If It Happens

1. Immediate Action

Surface Safely: If you feel lung discomfort, stop ascending, signal your buddy, and exhale fully—then resume slowly.
Buddy Support: Signal “problem” (hand wobble) and stay close—share air if needed.

2. Post-Dive Response

Symptoms Present: Stop diving, administer 100% oxygen (if available), and seek medical help immediately.
AGE Suspected: Lie the diver flat, keep them calm, and call emergency services (e.g., DAN: 1-919-684-9111).
Transport: Get to a hyperbaric chamber ASAP—don’t delay for mild symptoms.

3. Reporting

Log It: Record details (depth, ascent rate, symptoms) for medical pros and future safety.

Risk Factors

Inexperience: New divers may forget to breathe or control ascent.
Panic: Bolting to the surface increases risk—stay calm with training.
Deep Dives: Greater pressure changes amplify expansion (e.g., 33 ft to surface doubles volume).

Practical Example

Scenario: Ascending from 60 ft, diver holds breath from 10 ft to surface.
Pressure Change: 1.3 ATA to 1 ATA = 30% volume increase.
Result: Lungs overexpand by ~1 liter (normal capacity 4–6L)—enough to tear alveoli if full.

Tips for Success

Train: Practice controlled ascents in a pool or shallow water—focus on breathing.
Buddy Check: Confirm “breathe all the time” in pre-dive talks.
Monitor: Watch your computer’s ascent rate alarm—slow down if it beeps.

Overexpansion injuries are rare but serious, stemming from simple mistakes. Breathe continuously, ascend slowly, and manage buoyancy—prevention is your best defense. Need more on treatment or specific scenarios? Let me know!

Motus Aquaticus

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