 The Cochrane Collaboration, a group of evidence-based medicine (EBM) reviewers, reviewed the use of "Nei guan" (Acupoint P6) for nausea and vomiting, and found it to be effective for reducing post-operative nausea, but not vomiting, when combined with an antiemetic.However, the review acknowledged concerns about study limitations, unexplained variation in effects between studies, and an insufficient number of studies.The Cochrane review included various means of stimulating P6, including acupuncture, electro-acupuncture, transcutaneous nerve stimulation, laser stimulation, acustimulation device and acupressure; it did not comment on whether one or more forms of stimulation were more effective.