Final answer:
To reduce the risk of air embolism for a large open neck wound, an occlusive dressing should be applied.
Step-by-step explanation:
To reduce the risk of air embolism for a large open neck wound, the appropriate step is to apply an occlusive dressing. This helps prevent the entry of air into the wound and bloodstream, reducing the risk of air embolism. A tourniquet is not recommended as it can further exacerbate bleeding and increase the risk of infection. Placing the patient seated upright can help minimize the pooling of blood around the neck wound, but it is not specifically targeted at reducing the risk of air embolism.
Applying gentle pressure on both sides of the neck can also help control bleeding but may not directly address the risk of air embolism. Meanwhile, placing gentle pressure on both sides of the neck is not recommended because this could obstruct blood flow to and from the brain, possibly leading to further complications.