If air embolism is suspected while doing human autopsy, the head should be opened first and the surface vessels of the brain examined for gas bubbles, which must be prominent and definite, but not segmental breakup of the blood in the vessels with collapsed segments between.
Care should be taken to avoid pulling the sternum and ribs to avoid creating negative pressure in the tissues which may result in aspiration of air into vessels. Before handling the thoracic organs, the pericardium is opened, heart is lifted upwards and the apex is cut with a knife.
The left ventricle is filled with frothy blood, if air is present in sufficient quantity to cause death. If the right ventricle contains air, the heart will float in water.
Another method of demonstrating air embolism is by cutting the pericardium anteriorly and grasping the edges with hemostat on each side. The pericardial sac is filled with water and the heart is punctured with a scalpel and twisted a few times. Bubbles of air will escape if air is present.
A wide-bore needle attached to a 50 ml syringe filled with water is inserted into the right ventricle. If air is present it will bubble out through the water.
4 ml. of a 2% freshly prepared pyrogallol solution is collected into two 10 ml syringes. To the first syringe four drops of 0.5 M sodium hydroxide solution is added. Gas is aspirated from the right side of the heart.
The needle is removed and replaced with a stopper, and the syringe shaken. If air (oxygen) is present, the mixture turns brown. In the second syringe some air is introduced and the test repeated as a control. The solution should turn brown showing air embolism.
Chest x-ray Air in inferior vena cava can be demonstrated by puncturing it under water, and looking for escape of bubbles of gas. If fat embolism is suspected, the pulmonary artery should be dissected under water and the escape of fat droplets noted.