@zen/sarim/or neone-urgent physio doubt..plz help - aru

[ArchivalUser]

hey guys i had givn nbme 13 and 7, 2 months back..there i had come across few respi mcqs .
one was something like there's a guy in the basement of the house n is smoking or something like that --so whats the abg changes?
another question--person in the garage-- something about gas exhaust from the car n so whats the various gas partial pressures?
3rd scene-- some guy's room heater has broken down so which gas has increased in the room??

i dont have of ne of the exact questions ---n i am really really bad at respi concepts, so guys if ne of u can give the proper questions with the options n explanations, i will be really grateful.. pl help..thanks a lot

[ArchivalUser]

hey guys plz help.. these questions are very very high yield n these concepts just dont go in my head!!!

[ArchivalUser]

Hey aru I am not currently home ... Give me 30 mins I'll try my best to help

[ArchivalUser]

thanks so much, luking fwd to the info..

[ArchivalUser]

Hi there @aru!!

Believe it or not !!! i just went through 400 question!!!! just to find the right match of those questions but in nbme 13 and 7 none of those sort of questions EXIST!!! so ill give you my thoughts and ideas...

well lets break it down... ill go with the information you have provided as follow:

q1- guy in basement of house and is smoking... what are arterial blood gas changes?
q2- person in garage... gas exhaust from car ... what is the various gas partial pressure?
q3- guys room heater broken down so which gas has increased in the room?


so here is my understanding:
q1- well im not going to discuss ABG here but rather the scenario.... the first thing that comes to mind or should click reading " guy in basement smoking " would be age and duration keeping that in mind.... the next thing would be "CYANIDE POISONING" ... because its found in tobacco smoke and closed environments without filtration or atleast without "great ventilation" such as basements... you also find cyanide in insecticides/pesticides which can be commonly seen in basements as people might use them to treat bugs.... so with keeping cyanide poisoning in mind ... we now need to understand WHAT IS AN ABG?
abg: is used to test for blood ph, CO2 , O2 and Hb saturation....
now in cyanide poisoning... which is most likely affected?
even though ABG is not usually used or not the prefered tool for diagnosis cyanide toxicity...

PH: ↑ why? because this is most likely a perfusion defect... causing decrease O2 increase CO2--> now if the body compensates it'll be due to metabolic alkalosis therefore increase PH

CO2: increase

O2 : decrease...

Hb saturation : increase in venous blood ....decrease in arterial blood....




q2- this is STRAIGHT UP CARBON MONOXIDE POISONING..... classic question.... id need to look at the full question for any further explanation...

q3- not a single clue...



this is to the best of my ability and knowledge... if i have made errors or you have any further concerns or anyone else please feel free to correct / discuss thanks!!

[ArchivalUser]

hey zen thanks sooo much..
u didnt find it in those nbmes?? then may be i'm mistaken.. just cant rem where i came across those questions....
hey but why is it a perfusion defect in q1? perfusion defect is mostly in pulm embolism..how will cn poisoning rsult in perfusion defct?

[ArchivalUser]

great questions @ aru. these tend to get confusing for some of us (including me) and its good we can discuss the concepts here.

in addition to what zen has written, i'd like to add some points (correct me if im wrong anyone)....

in Q3, i think the buzz word is "HEATER BROKEN DOWN". from UW, carbon monoxide poisoning can be caused by:
- automobiles in poor ventilated space
- faulty home heater

so i think Q2 and Q3 are really testing the same stuff.

*CO poisoning = NORMAL Pa02

*CO poisoning = INCREASED carbon monoxide gas (increased carboxyHb competitively binds with heme, displacing 02 ---> reduces O2 binding capacity ---> left shift O2 curve ---> increased O2 affinity)

* CO poisoning Rx = 100% or hyperbaric O2

regarding Q1, zen has already explained it

[ArchivalUser]

apologizes... not perfusion ... mixxed up thoughts ... disregard that portion...

Ph increases because its increase CO2 = resp acidosis compensate = metabolic alkalosis...

[ArchivalUser]

thanks a ton drsahiba for xplaining that..
thanks soo soo much zen for clearing that up.... love this forum ..all the best.)