My colleague observed a cabin desent rate of 2000 - 3000 fpm
Since that ought to be a Cabin
climb rate of 2-3000fpm, was that just a typo or do you genuinely believe that you identified rate of
descent prior to donning the O2?
Hypoxia is (how?) quick at FL380 - interested to learn how fast and insipid errors in reading gauges could be. Perhaps your consciousness was already affected to some degree, even though everything else appears to have been done by the textbook.
If it was a typo, forgive me, I am not part of the spelling police!