Air embolism and veins is greater than atmospheric pressure, an air embolus does not often happen when a blood vessel is injured. In the veins above the heart, such as in the head and neck, the venous pressure may be less than atmospheric and an injury may let air in. This is one reason why surgeons must be particularly careful when operating on the brain, and why the head of the bed is tilted down when inserting or removing a central venous catheter from the jugular or subclavian veins. When air enters the veins, it travels to the right side of the
Fascial spaces of the head and neck rare and are associated with marked trismus. The pterygomandibular space lies between the medial side of the ramus of the mandible and the lateral surface of the medial pterygoid muscle. The infra-temporal space is the inferior portion of the deep temporal space. Modern understanding of the fascial spaces of the head and neck developed from the landmark research of Grodinsky and Holyoke in the 1930s. They injected a dye into cadevers to simulate pus. Their hypothesis was that infection in the head and neck mainly spread by hydrostatic pressure. This is now accepted to be true for most infections in