Asphyxiation is a term applied to death starting with the lungs. Death due to asphyxia can be caused by several contributing factors: carbon dioxide, carbon monoxide, drowning, hanging or strangulation.
One interesting aspect of this type of death is that by the time the person has actually died, the heart has often undergone such intense effort to carry oxygen to the body that its muscular walls have broken down and it is dilated.
This can cause embalming problems. The aorta is dilated, the aortic valve is useless, and when embalming chemical is injected arterially toward the heart, the chemical flows into the heart through the aortic valve, filling the left ventricle. Then the chemical fills the left auricle and follows the pulmonary system to the lungs. This most often will result in a persistent lung purge.
If the right side of the heart is also dilated, the flow of chemical will return to the right heart, carrying a volume of blood ahead of it, and will be forced into the vena cava. The main course of this flow will take the course of the superior vena cava, and the face will become discolored and possibly distended.
There are a variety of procedures which can be used to prevent this, but one sure and safe process is to inject the head separately using both the right and left common carotid and drainage from both the right and left internal jugular veins. The injection should be slow; this is not instant tissue fixation. A low index arterial, mixed with a quality co-injection chemical to the embalmer's discretion is recommended.
Once the head is cleared of stain or blood congestion, the rest of the body can be embalmed in the normal manner. Also, little or no trouble should be encountered in carbon monoxide cases, since the blood is cherry red and will remain in a liquid state for a considerable time.