There Was A Wreck An Obese Lady Had Bad Injury

There was a wreck an obese lady had bad injury cut to left forearm. I looked for glass as blood wa coming out and quickly soaked her left pant leg. Cut on forearm 3-4 inched top n left side of forearm showing subcontaneous tissue. I wrapped towel around arm and told her to hold arm up. She had to be cut out of car. Could she have damaged the ulna artery with large amount of blood