“In patients who had cardiac arrest for less than 20 minutes, 60.9% of patients achieved ROSC, compared to 37.9% who arrested for more than 20 minutes.”
In the cases of 30 mins without arrest none survived.
If you have ever performed CPR you’ll also know performing it for 5 minutes is hard. 10 mins… 20 mins… 30 mins… swapping out 3 people and making sure it goes well. All 3 people will be broken tired by the time it’s done.