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 In the head and neck, potential spaces are primarily defined by the complex attachment of muscles, especially mylohyoid, buccinator, masseter, medial pterygoid, superior constrictor and orbicularis oris. Infections involving fascial spaces of the head and neck may give varying signs and symptoms depending upon the spaces involved. Trismus (difficulty opening the mouth) is a sign that the muscles of mastication (the muscles that move the jaw) are involved. Dysphagia (difficulty swallowing) and dyspnoea (difficulty breathing) may be a sign that the airway is being compressed by the swelling. Different classifications are used. One method distinguishes four anatomic groups: Since the