Hypoxemia - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
Home
USMLE Articles
USMLE News
USMLE Polls
USMLE Books
USMLE Apps
Go Back   USMLE Forums > USMLE Step 1 Forum

USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 01-17-2012
USMLE Forums Newbie
 
Steps History: Not yet
Posts: 2
Threads: 1
Thanked 0 Times in 0 Posts
Reputation: 10
Default Hypoxemia

In RR, it says, "carbon dioxide retention in the lungs always causes correspondng decrease in PO2 i.e. chronic bronchitis..etc"

Why is this an absolute rule?

I'm thinking that the lung can only have a certain volume of gas within it. Thus, an elevated partial pressure correlates to a higher fractional concentration of that gas and as a result, you have a smaller fractional concentration of gas occupied by O2 thus, you get a lower PaO2.

If anyone could give me feedback, that would be greatly apprecited.

Thank you in advance.
Reply With Quote Quick reply to this message



  #2  
Old 01-17-2012
Hope2Pass's Avatar
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 1,684
Threads: 213
Thanked 1,590 Times in 660 Posts
Reputation: 1600
Default

"carbon dioxide retention in the lungs always causes correspondng decrease in PO2 i.e. chronic bronchitis..etc"

You're on the right track..Basically, this has to do with atmospheric pressure. The lungs can't exceed a pressure of over 760 ( I think ). And CO2 and O2 together have to add up to that and keep their pressures in balance. So if you have an increase in O2 then CO2 goes down and if you have an increase in CO2 then O2 goes down .. and that's primarily why this is an absolute rule!

Hope thats right!
Reply With Quote Quick reply to this message
  #3  
Old 01-17-2012
doxorubicin's Avatar
USMLE Forums Guru
 
Steps History: 1+CK+CS+3
Posts: 391
Threads: 98
Thanked 160 Times in 98 Posts
Reputation: 170
Default

however exception i have found in ARDS in which there is sever hypoxemia ie low O2 with normal to respiratory alkalosis ie low CO2.
__________________
if ur ready to learn......world is ready to teach...take d leap!!
Reply With Quote Quick reply to this message
  #4  
Old 01-17-2012
MedicalExaminer's Avatar
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 824
Threads: 66
Thanked 463 Times in 298 Posts
Reputation: 473
Default alveolar gas equation

i simply explain this condition through this formula

PAo2=PIo2-PAco2/R


Increase in arterial CO2 decreases Partial pressure of alveolar oxygen which causes hypoxemia as in chronic bronchitis.
__________________
Everything is possible for him who believes (MARK 9:23)
245/247/passed on 1st attempt/223/2mos Obsie /3 US LORS/visa not needed/2008 grad
Reply With Quote Quick reply to this message
  #5  
Old 01-18-2012
MedicalExaminer's Avatar
USMLE Forums Master
 
Steps History: 1+CK+CS+3
Posts: 824
Threads: 66
Thanked 463 Times in 298 Posts
Reputation: 473
Default ...........

in ARDS the intraseptal and alveolar edema + hyaline membranes cause difusion problem of O2 and Hypoxemia,but as CO2 is 20x more soluble it is readily eliminated from body (even resp. alkalosis may occur due to hyperventilation)
__________________
Everything is possible for him who believes (MARK 9:23)
245/247/passed on 1st attempt/223/2mos Obsie /3 US LORS/visa not needed/2008 grad
Reply With Quote Quick reply to this message
The above post was thanked by:
alice (10-28-2012)



Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

Favorite USMLE Books
What USMLE books you really think are useful. Leave blank if you don't want to tell.
Location
Where you live. Leave blank if you don't want to tell.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Hypoxemia + Confusion + Petechiae rasheed USMLE Step 2 CK Classic Clues 1 07-09-2016 12:59 PM
Obstructive Lung Disease Hypoxemia and Dyspnea sequence donofitaly USMLE Step 1 Forum 4 01-16-2015 04:57 AM
NRDS and hypoxemia plasticsurgeon USMLE Step 1 Forum 8 08-02-2011 04:58 PM
Hypoxemia Case USMLE-Syndrome USMLE Step 2 CK Forum 5 06-08-2011 06:47 PM
Pulmonary Shunt and Hypoxemia Hope2Pass USMLE Step 1 Forum 4 04-09-2011 11:21 AM

RSS Feed
Find Us on Facebook
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2014)