Okay, as a nurse with an advanced cardiac life support certification for adults and a neonatal resuscitation certification, I feel like this is a question I can answer.
First, understand that the blood moved by cpr is much less than that moved by a normal heartbeat. Our goal with cpr is to maintain brain and critical organ perfusion until ROSC (return of spontaneous circulation) is achieved. The number of beats per minute recommended is based on what we know about about basically the maximum speed of cpr that can a) be achieved by an average person, b) be sustained by an average person, and c) (this is the most important) allow full chest recoil. Chest recoil is the chest getting back to full thickness after you release pressure on it. This is extremely important because that allows the heart to fill back up with blood so you can push it out with your next compression. Faster cpr doesn't move blood efficiently because there's not enough blood returning into the heart to push back out. We also compress in adults to a depth of 2-2.4 inches (5-6 cm) in an adult to ensure that we're emptying the heart sufficiently. This depth is smaller in children because they have a proportionately smaller chest cavity. The key is we want to compress to a depth around 1/3 the total depth of the chest.
Second thing to understand is that the movement of oxygen is via a gas gradient. Oxygen wants to move from where there's the most oxygen to the last oxygen until all fluids present have the exact same amount of oxygen. So we need to get oxygen into the blood. In one rescuer cpr this is achieved via compressions only because when you compress the chest you compress the lungs as well, which means that chest recoil also moves air into the lungs and this air allows for gas exchange which removes some CO2 and adds some oxygen. Chest recoil isn't as good at this as ventilation, which is why if there are two rescuers we prefer to have one ventilate and one compress (ideally you'll have more than 2 rescuers because best practice is to change compressors every 2 minutes). This will move more oxygen into the lungs.
Thirdly, we're trying to maintain a minimum blood pressure (we probably won't measure this during cpr until ROSC is achieved). In order to maintain brain, heart tissue, and kidney perfusion, we need enough blood pressure to move oxygenated red blood cells into the tissues and remove spent ones. Because we don't measure this, I can't remember the exact values, but I think in nursing school they said we needed a minimum of 80/40 to prevent kidney failure in sepsis, so I assume it's somewhere around there.
Fourth, every time you pause compressions to change compressors, a gap in compressions of more than roughly one second plummets that blood pressure we're trying to maintain down to zero. Your next 3 or so compressions won't move oxygen. They'll just be working to 'pump up' blood pressure to where we're properly moving oxygen again.
So now that we know what cpr does, let's talk Witcher physiology versus human physiology a little bit.
Now, in the shows, fan films, and games, witchers have roughly the same chest circumference as a human. This implies that the organs in the chest are roughly the same size as those of a human. So that means we should be keeping that compression depth of 2-2.4 inches or 1/3 the total chest depth to move blood.
We should also compare human pulse rate to Witcher, right? Well, a normal pulse rate for a human is 60-100 bpm. 1/4 that is 15-25. CPR is done at an ideal rate of around 120 bpm, meaning it's clinically tachycardic for a normal human. We also need to know that normal pulse range doesn't mean every human's resting pulse lays in that range. For very fit people, like say marathon runners and cross country skiers with excellent cardiovascular health, they often have a much lower resting pulse. I once looked after a marathon runner whose resting pulse rate was 30. What's the resting rate for a Witcher again? Up to 25? Pretty close, right?
We do not taper the rate of our cpr for marathon runners. A couch surfer like me with a resting pulse of 80 gets the same 120 bpm cpr as a marathon runner who is well oxygenated at 30 bpm.
Given this, I believe that the Witcher should receive standard human cpr.
But here's where it gets weird. Marathon runners and witchers live at a lower heartrate and (probably got witchers, definitely for marathon runners) blood pressure than your average human. Their body uses perfusion or efficiently. Which means that with good quality cpr, in marathon runners we sometimes achieve consciousness before ROSC. Which is great because it tells us we're achieving perfusion of the brain. We do not want to slow down just because they became conscious. We want that perfusion.
But most people who wake up disoriented with someone bouncing on their chest and cracking their ribs become combative. So fun fact, you're going to do cpr on your Witcher at normal human speed and then convince him to fucking stop fighting you until ROSC.
Now, we also use drugs and electricity to help restart the heart in ACLS and achieve ROSC. We probably don't have electricity, so let's consider drugs and run a 'chemical code'. Two big ones are atropine and adrenaline. If we want to be really nerdy, based on the ingredients and effects in the Witcher video games, Cat should have a decent amount of atropine. Maribor forest and Blizzard both generate adrenaline points so let's assume those are artificial adrenaline at least in part.
So depending on what you think caused your Witcher to go down, when he wakes up from your excellent human speed cpr, have him drink Blizzard, Maribor forest, or Cat and hopefully you'll achieve ROSC!
Tldr: it should be human speed.
