He held his breath for 22min? No they fucked up the procedure. Even if he had held his breath at first he should have been unconsious the first time he took one. I’ve nearly been knocked out by nitrogen hypoxia before. It takes one lungfull of non oxygenated air to make you start to black out. He must have still been getting some oxygen somehow. It sounds like they were trying to use a mask (which is a dumb way to do it) so they probably didn’t use a high enough flow rate for the nitrogen and he was breathing in air from around the mask. They probably would have been better off forgetting about the mask entirely and just blowing nitrogen at his face at a much higher flow rate (that’s what almost did it for me).