1At a glance
- Primary Cause
- Pulmonary barotrauma (lung overexpansion) during ascent
- Onset Time
- Seconds to minutes after surfacing
- Pressure Differential for Risk
- As little as 1.2 metres (4 feet) of ascent with breath-holding
- Commonly Affected Organ
- Brain (cerebral AGE)
- First Aid
- 100% oxygen, lying flat, emergency medical evacuation
- Definitive Treatment
- Recompression in a hyperbaric chamber
- Bubble Size
- Can range from microscopic to several millimetres
- Fatalities
- Approximately 10-15% of all diving fatalities
2Recognising the Signs and Symptoms of AGE
Immediate onset of symptoms is a hallmark of AGE. Unlike some forms of decompression sickness, which can have delayed onset, AGE symptoms typically appear within moments of surfacing. Divers or their buddies should be alert for sudden neurological changes such as disorientation, vision problems, weakness or paralysis on one side of the body, and loss of consciousness.
Other critical signs include severe dizziness (vertigo), difficulty speaking or swallowing, severe headache, confusion, and frothy, blood-tinged sputum if the lung tissue was significantly damaged. Any of these symptoms, especially following an uncontrolled or rapid ascent, should prompt immediate suspicion of AGE and initiate emergency protocols without delay. Remember, time is brain when dealing with arterial gas embolism.
3Comparing Pulmonary Barotrauma (PBT) Conditions
| Condition | Primary Cause | Symptoms | Onset | Liveaboard Relevance |
|---|---|---|---|---|
| Arterial Gas Embolism (AGE) | Air bubbles enter arterial system from lung overexpansion | Sudden neurological deficit (e.g., paralysis, unconsciousness) | Seconds to minutes after surfacing | Most severe; remote location prolongs recompression, increasing risk of permanent damage. |
| Pneumothorax | Air trapped in pleural space, collapsing lung | Chest pain, shortness of breath, rapid heart rate | Minutes to hours after surfacing | Can be debilitating; requires medical evacuation and may delay return to shore. |
| Mediastinal Emphysema | Air trapped in the chest cavity around heart/trachea | Chest pain, difficulty swallowing, change in voice | Minutes to hours after surfacing | Less severe than AGE/Pneumothorax, but still requires medical attention; limits further diving. |
| Subcutaneous Emphysema | Air trapped under skin (neck/collarbone area) | Swelling, crackling sensation on touch, discomfort | Minutes to hours after surfacing | Generally benign, resolves spontaneously, but indicates lung injury; no diving until cleared. |
4Prevention: Your Best Defence Against AGE
Preventing AGE is straightforward in principle: never hold your breath while ascending. This fundamental rule of scuba diving ensures that the expanding air in your lungs can escape freely as the ambient pressure decreases. Always ascend slowly, at a rate no faster than 9 metres (30 feet) per minute, and maintain continuous, controlled exhalation.
Furthermore, regular practice of buoyancy control and good trim helps maintain a slow, stable ascent. Staying hydrated and avoiding diving while unwell, particularly with respiratory infections or conditions that might impair gas exchange in the lungs, can also reduce risk. Proper training and adherence to safe diving practices are your most effective preventative measures.
5AGE on Liveaboards: Enhanced Risks and Preparedness
Liveaboard diving often involves multiple dives per day in potentially remote locations, elevating the risks associated with AGE. A rapid or breath-holding ascent on the last dive of the day, or any dive, can lead to severe consequences far from immediate medical help. The extended time until definitive recompression treatment can significantly worsen outcomes.
Therefore, liveaboard divers must be extra vigilant. Briefings from dive masters typically reiterate safe ascent procedures, and it's vital to follow them. Ensure your dive computer is always active, monitor your ascent rate, and always have an emergency action plan in mind. Knowing where the nearest recompression chamber is located, even if only theoretically, and understanding the liveaboard's emergency protocols for medical evacuation (medevac) is part of being a responsible diver on such trips.
6Common misconceptions
Myth: AGE only happens to inexperienced divers. Fact: While inexperience can contribute, AGE can affect any diver who holds their breath or ascends too quickly, regardless of their certification level or experience. Even experienced divers can make mistakes under stress or distraction.
Myth: If you feel fine immediately after a dive, you're safe from AGE. Fact: While AGE typically has immediate onset, in rare cases, symptoms might be subtle or delayed by a few minutes. Any unusual symptom within a short period of surfacing, especially after a challenging ascent, should be taken seriously.
Myth: A safety stop will prevent AGE. Fact: A safety stop is crucial for reducing nitrogen build-up and preventing decompression sickness, but it does not prevent AGE. AGE is caused by lung overexpansion during ascent, regardless of nitrogen load. Continuous exhalation throughout the entire ascent is the only prevention for AGE.
FAQ
What is the main difference between AGE and DCI (Decompression Sickness)?
AGE is caused by expanding air physically rupturing lung tissue and entering the bloodstream, leading to immediate blockages. DCI is caused by inert gas (nitrogen) coming out of solution in tissues and forming bubbles, usually with a delayed onset, due to insufficient decompression.
Can AGE be fatal?
Yes, AGE is a life-threatening condition. Due to the rapid blockage of blood flow to vital organs like the brain or heart, it can cause immediate loss of consciousness, severe organ damage, or death if not treated promptly with recompression therapy.
What should I do if I suspect AGE in my dive buddy?
Immediately bring them to the surface, ensure an open airway, administer 100% oxygen if available, place them in a comfortable position (often flat on their back), keep them warm, and arrange for immediate medical evacuation to the nearest hyperbaric chamber. Call for emergency services and inform them it's a diving injury.
Does AGE always cause unconsciousness?
No, not always. While loss of consciousness is a common and severe symptom, AGE can manifest with a range of neurological signs, including dizziness, confusion, weakness, vision problems, or partial paralysis, depending on where the air bubbles lodge.
Can I dive again after experiencing AGE?
A diver who has experienced AGE will require extensive medical evaluation, including pulmonary function tests and neurological assessments. Returning to diving would depend entirely on the medical team's clearance, and it's often advised against due to the high risk of recurrence and potential underlying lung vulnerabilities.