A little more background that I should have given, is that the healer comes from a race of people that live on the coast, always near water. I'm figuring over thousands of years, they might have figured this out.!
Given that none of the races of humans who lived on coasts always near water in our world never figured out mouth-to-mouth respiration or chest compression either separately or in combination till the 20c -- there's no reason to assume some fantasy group of people could not have gotten there quicker, but equally no reason to assume they would have, and a pretty heavy burden of implausibility to lift.
(Bear in mind that those practices seem obvious to us because we've grown up with them as being obvious, and we take for granted the underlying physiological assumptions -- but the fact remains that there's nothing actually obvious about them, taken outside of that cultural matrix. Our ancestors for thousands of years were not stupid, and yet - no established practice of mouth to mouth or chest compression, anywhere, ever.)
Taking it a step further -- we frequently ascribe magical healing powers to CPR that it does not in fact possess. Ask anybody with actual EMT or ER experience what CPR is really good for, and how often it works: not what the lay person assumes from the media treatments.
You can certainly do whatever your story demands in your fantasy setting -- but keep in mind that context matters, and ideas & practices tend to exist in a matrix, not in isolation.