Sunday, 12 February 2012

Scuba Diving Decompression Sickness: The Bends & Caisson Disease:Cerebral Arterial Gas Embolism (CAGE)


This is caused by rupture of the fragile lining of the lung's alveoli allowing large quantities of air to enter the blood vessels leading to the small arteries in the brain via the heart.
Cerebral Arterial Gas Embolism is the result of pulmonary barotrauma usually caused when a diver runs out of air. This will often result in a panic reaction, with breath-holding and rapid ascent to the surface leading to over expansion of the lungs as the volume of air in them increases with decreasing ambient water pressure (Boyle’s Law).
Signs and Symptoms of CAGE
Cerebral Arterial Gas Embolism is the result of pulmonary barotrauma, which may present with the following symptoms.
·         Subcutaneous emphysema, particularly around collarbone area.
·         Chest pain.
·         Shortness of breath (dyspnoea).
·         Coughing, possibly with blood (haemoptysis).
·         Increase in heart rate (tachycardia).
·         Decrease in blood pressure (hypotension).
The resulting cerebral damage may result in the following symptoms.
·         Severe headache.
·         Paralysis.
·         Numbness.
·         Unconsciousness.
Symptoms similar to those of neurological DCS may also be present. Any confusion between the diagnosis of CAGE or neurological DCS should not influence the immediate care of the affected diver, as both are medical emergencies treated initially in the same way.
Treatment of DCS (CAGE and DCI) 
Initial treatment for all suspected cases of decompression illness, whether thought to be DCS or CAGE, should be the same. Firstly, the accepted practice of "Safety, ABC" should be used.
·         Safety first - do not place yourself at risk of becoming another casualty, it is more difficult to treat two divers than just one.
·         If unconscious, place the casualty in the recovery position and ensure airway is open.
·         Administer high concentration oxygen if available.
·         Perform CPR if required.
·         Seek medical assistance immediately- see the contact section for details.
In addition, rescuers should ensure the following.
·         Lay the casualty down and keep them horizontal - this may help prevent bubble migration to the brain.
·         Encourage the diver to remain calm and still.
·         Protect against hypothermia - replace wet clothes with dry. Do not expose to excessive heat.
·         Encourage fluid intake (aim for 1 litre in the first hour) - if the casualty has a reduced conscious level or has difficulty in swallowing then avoid giving oral fluids. If available, intravenous fluid therapy is preferred.
·         Monitor for deterioration and record observations.
·         Notify the appropriate emergency service of any deterioration.
·         Do not give opiates as this may reduce respiratory rate and prolong nitrogen off-loading.
·         Never administer Entonox ("gas and air"), as this will worsen the condition due to its high nitrogen content.
Recompression Therapy
The definitive treatment for any form of decompression illness is recompression in a hyperbaric chamber.
The main purpose of this is to reduce the size of any existing bubbles. In addition, 100% oxygen is given in order to encourage the excretion of nitrogen from the body.
Symptoms may persist due to existing tissue damage and the accumulation of blood cells, etc, around the points where bubbles were situated.
At the Hyperbaric Medicine Unit in Aberdeen the most common therapy for bends is based on a modified U.S. Navy Table 6 profile. In this treatment, the patient is compressed to nearly three times normal atmospheric pressure, which equates to a depth of 18msw.
Depending on the patient's condition during the treatment, the table may be extended, or changed to a Heliox (HeO2) saturation table lasting several days. 

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