When bubbles of air or any other gas cause a blockage of blood vessels in the circulatory system then this is known as air embolism.
There are several symptoms that are associated with this condition such as loss of consciousness, difficulty in breathing, bloody sputum, tremors, convulsions, etc.
Since in the given condition, the diver is having frothy blood in his mouth and since he ascended rapidly calling for help he is most likely to be suffering from an air embolism.
