The Risks Of Ascent
Posted By Erik Seedhouse on 2 December 2002
The nature of barotrauma may range from mild, to a complete collapse of the lung. In some cases the air may escape into the pulmonary venous system where it will move through the heart and into the arteries. When this occurs, bubbles form in the blood, causing an Arterial Gas Embolism (AGE). AGE is a major cause of death in conventional diving and the initiating cause (pulmonary barotrauma) often goes undetected. Experimental evidence demonstrates that intra-tracheal pressures of about 10 mm Hg are all that is needed for AGE to occur. Distention of the alveoli leads to rupture, alveolar leakage of gas, and leakage of the gas into the blood. As the free diver takes their first breath after surfacing, the extra-alveolar gas enters the ruptured blood vessels, and may migrate to the left side of the heart. Here it is distributed systemically as emboli sent to areas determined by buoyancy. AGE may arise from gas bubbles in the pulmonary capillaries, pulmonary veins to the left side of the heart (resulting in a rare coronary artery embolism) or internal carotid and vertebro-basilar arteries to the brain (causing a cerebral artery embolism - blockage) with the clinical picture of a stroke. As bubbles pass over the endothelium, there are direct cellular effects (within 1-2 minutes) causing local swelling, downstream coagulopathy and occasionally hemorrhages. There is also an immediate increased permeability of the blood-brain barrier, loss of cerebral auto-regulation, and a rise in the systemic blood pressure. In order to ensure immediate and effective response, it is important for free divers to recognize the symptoms of AGE and its associated problems. Some of these are listed below.
Symptoms:
- Bloody froth from mouth or nose (hemoptysis)
- Disorientation
- Chest pain
- Paralysis or weakness
- Dizziness
- Blurred vision
- Unconsciousness
- Convulsions
- Stopped breathing
- ir bubbles in the retinal vessels of the eye
- Death
If any of the above signs and symptoms are observed, certain steps should be taken as outlined below:
- CPR, if required
- Open airway, prevent aspiration, and intubate if trained person available
- Give O2, remove only to open airway or if convulsions occur.
- Place in horizontal, neutral position
- Restrain convulsing person loosely and resume O2 as soon as airway is open.
- Protect from excessive cold, heat, water or fumes.
- Transport to ER for evaluation in preparation for removal to the nearest recompression chamber.Air evacuation should be at sea level pressure
- Bookmark with :
- what are these?
