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NBME 22 Answers

nbme22/Block 2/Question#6 (34.3 difficulty score)
A 52-year-old man is brought to the emergency ...
4 Months🔍

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 +10  upvote downvote
submitted by welpdedelp(198),
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It asw tsju igkasn het enpslaif of sRBC (021 yd)sa

haliburton  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. +7  
link981  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 +5  
baja_blast  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. +  

 +5  upvote downvote
submitted by iviax94(7),
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I geidfur they erwe igyrtn to teg at teh efli tneypaxcce of an ,RBC tub wlo’nutd lulsaneeptpm 2O ycalhcintel rplaece eht CO uonbd to CsB?R AF eevn noniemts taht CO nbsdi cvmeioytptiel ot RBCs, adn ins’t htat eht loehw tipon fo nivgig pr/hyi%0bce0ra1 O2?

nc1992  First aid has a lot of errors +  
yotsubato  Thats not an error though. Thats the actual reason behind giving hyperbartic O2 for CO poisoning... +9  
mumenrider4ever  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 +  

 +2  upvote downvote
submitted by link981(133),
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The tqsiouen elihw liysdupt tnitw,re kass who long teh 'BsCR ahtt crayr het CO keta to be rdemove mrfo eht utclciioanr, otn how olng het CO tsaek ot eb ormedev romf het CB.R utsJ saignk the aesnipfl of sCRB ni an ltpysdiu oeacidctmpl ay.w As we n,wko s'BRC eilf pans is utoba 012 ydas dan tnhe hety aer vremdoe form uor aulrt.noicic 210 dsay is butoa 4 nhsmot. xtNe miet eyht lliw rpaybolb ska eth RBC aispefnl ni seewk or ni osuh,r woh k?swon mhs

Oxygen can compete CO to bind Hb but i think not all CO-Hb can be removed. Notice " ALL" the C0-binding RBC so go with CO-Hb RBC die. though i spent a lot of time for this question too