What is the highest reported incidence of venous air embolism during sitting craniotomies?

The highest reported incidence of venous air embolism during sitting craniotomies is indeed in the range of 20 - 40%. This is significant because sitting craniotomies involve the patient being positioned upright, which can create conditions conducive to the entry of air into the venous system. Factors such as the patient's position, the presence of negative pressure in the operative field, and the drainage of venous blood can increase the risk of air being introduced during the procedure.

Studies indicate that when patients are placed in a sitting position, especially during neurosurgery, the risk of venous air embolism can rise. The incidence figures you see in this context typically reflect a variety of clinical reports and surgical outcomes. Values higher than 40% would correlate with considerably greater risk factors or complications, which are generally not supported by the broader body of clinical evidence regarding sitting craniotomies. Hence, the answer of 20 - 40% aligns with the common findings and practices observed in clinical settings.