There are several techniques for removing a ring that is stuck on a patient’s finger, starting with the simplest – using ring cutters to cut it off. However, if the patient doesn’t want the ring destroyed, the string technique has been advocated, where a string is wrapped around the finger to compress the edema, then passed under the ring and unwound for removal. An oxygen mask strap works well for this purpose because of its elasticity and flatness; check out this AliEM trick of the trade post https://www.aliem.com/2012/08/trick-of-trade-ring-removal-using/. Also, this site provides a nice overview of the numerous methods https://aneskey.com/ring-removal/. Remember that tungsten and ceramic rings are usually hard to cut, but easy to break using vice or locking pliers.