Overexpansion injuries can manifest themselves in four ways.
1. Arterial Gas Embolism (AGE). In this case, air gets into the bloodstream and works its way to the small capillaries of the brain where they block the blood flow. The result is a stroke. This can result in paralysis, brain damage, and even death.
2. Mediastinal Emphysema. This condition results when air collects in the cavity surrounding the heart. This puts pressure on the heart and can result in heart failure.
3. Pneumothorax. Pneumothorax occurs when air gets in the pleural cavity on the outside of the lungs. This condition causes chest pain and can result in collapsed lung(s).
4. Subcutaneous Emphysema. This one is the least dangerous of the four manifestations of overexpansion injuries. In this case, air collects in the subcutaneous tissues usually around the shoulders and neck. The skin is itchy and spongy.
Symptoms of lung overexpansion injuries normally occur immediately, and can include difficulty breathing, chest pain, crackling under the skin, unconsciousness, or death. Dizziness can be a symptom of an arterial gas embolism from a lung overexpansion injury, and chest pain or tightness can be a symptom of lung barotrauma. These symptoms are associated with other signs of injury in cases of lung overexpansion, however note that other less serious causes can create similar symptoms. A mild middle ear barotrauma can also cause a feeling of dizziness after diving. Shifting heavy gear, breathing cold air, breathing deeply when you're not used to it can cause chest discomfort. Only a medical evaluation by medical personnel who know what to look for can give an accurate diagnosis.
If in doubt start first aid immediately while transportation to a medical facility is arranged.
First aid for lung injuries includes delivery of 100% oxygen and CPR if necessary.
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