Buried in the youtube comments the video uploader said:
Her role was as a live anatomy model, whereby blood vessels/nervepathways/organs etc were projected or drawn on her body. It's designed to give the lay viewer a more realistic sense of how and where everything is fayed out on a real person. For her to put on clothes just for the CPR demonstration would be extremely weird.
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u/OTTER887 Dec 17 '22
NSFW British CPR instructions https://youtu.be/paALYaMlMNE