NBME 22 Answers ↦
(34.3 difficulty score)
A 52-year-old man is brought to the emergency ...
If I'm reading this right, this is just a tricky dicky question. I think CO binds 200x stronger than O2. But if an O2 cycles through binding / unbinding 200 times before a CO gets kicked off, this should still clear the CO from that cell sooner or later. strange to think it is 1. essentially permanently trapped in a cell, and 2. doesn't kill you and can be treated with O2 to resolution within a few hours or a day. They must just be thinking, until that last RBC dies, you've got original CO in a circulating cell. but just a fraction (because you didn't die). not sure how that CO isn't just passed on during recycling, based on this line of thinking.
The question while stupidly written, asks how long the RBC's that carry the CO take to be removed from the circulation, not how long the CO takes to be removed from the RBC. Just asking the lifespan of RBCs in an stupidly complicated way. As we know, RBC's life span is about 120 days and then they are removed from our circulation. 120 days is about 4 months. Next time they will probably ask weeks or in hours, who knows? smh
If that's what they're looking for why cant the NBME people just ask "How long does it take for RBCs to turn over?" Ridiculous.
First aid has a lot of errors
Thats not an error though. Thats the actual reason behind giving hyperbartic O2 for CO poisoning...
The question ask how long it takes to remove all the CO-carrying RBC so I think they're implying that theoretically not every single CO-carrying RBC would be replaced with oxygen from the supplemental O2 and some would die off naturally