Signs and symptoms
In surgery
Symptoms include:
Hypotension
Shortness of breath

In divers
Symptoms of arterial gas embolism include:
Loss of consciousness
Cessation of breathing
Vertigo
Convulsions
Tremors
Loss of coordination
Loss of control of bodily functions
Numbness
Paralysis
Extreme fatigue
Weakness in the extremities
Areas of abnormal sensation
Visual abnormalities
Hearing abnormalities
Personality changes
Cognitive impairment
Nausea or vomiting
Bloody sputum
Symptoms of other consequences of lung overexpansion such as pneumothorax, subcutaneous or mediastinal emphysema may also be present. Causes
Interventional procedures
Interventional radiology procedures, cardiac, and neurosurgical procedures can predispose to air embolism. Besides, increasing use of pump injectors for contrast delivery, and percutaneous intervention to the lungs also increases the risk of air embolism. Decompression illness
Gas embolism is a diving disorder experienced by underwater divers who breathe gases at ambient pressure, and can happen in two distinct ways:

Pulmonary barotrauma:  Air bubbles can enter the bloodstream as a result of gross trauma to the lining of the lung following a rapid ascent while holding the breath; the air held within the lung expands to the point where the tissues tear (pulmonary barotrauma). This is easy to do as the lungs give little warning through pain until they do burst. The diver will usually arrive at the surface in pain and distress and may froth or spit blood. A pulmonary barotrauma is usually obvious and may present quite differently from decompression sickness. Decompression sickness: Inert gas bubbles form in the bloodstream if the gas dissolved in the blood under pressure during the dive is not allowed sufficient time to be eliminated in solution on ascent.
At this time, bubbles may be observed directly crossing a septal defect, or else a patent foramen ovale may be opened temporarily by asking the patient to perform the Valsalva maneuver while the bubbles are crossing through the right heart – an action which will open the foramen flap and show bubbles passing into the left heart. Such bubbles are too small to cause harm in the test, but such a diagnosis may alert the patient to possible problems which may occur from larger bubbles, formed during activities like underwater diving, where bubbles may grow during decompression. A PFO test may be recommended for divers intending to expose themselves to relatively high decompression stress in deep technical diving. Diagnosis
As a general rule, any diver who has breathed gas under pressure at any depth who surfaces unconscious, loses consciousness soon after surfacing, or displays neurological symptoms within about 10 minutes of surfacing should be assumed to be experiencing arterial gas embolism.Symptoms of arterial gas embolism may be present but masked by environmental effects such as hypothermia, or pain from other obvious causes. Neurological examination is recommended when there is suspicion of lung overexpansion injury. Symptoms of decompression sickness may be very similar to, and confused with, symptoms of arterial gas embolism, however, treatment is basically the same. Discrimination between gas embolism and decompression sickness may be difficult for injured divers, and both may occur simultaneously.