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Old 10-05-2015
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Fire Thread exam in 3 days! partial pressure of 02 levels!!!! need help!

Hey guys, I'd appreciate any input regarding a concept that will help me understand when, where or under what factors P02 is increased or decreased....

like in anemia, or hypoxia, CO poisoning, high altitude....

i don't know if you guys will understand what im trying to ask....but I'm gonna be hopeful


PLEASE PLEASE help me understand this concept!

thanks in advance!
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Old 10-05-2015
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Originally Posted by Virgo11 View Post
Hey guys, I'd appreciate any input regarding a concept that will help me understand when, where or under what factors P02 is increased or decreased....

like in anemia, or hypoxia, CO poisoning, high altitude....

i don't know if you guys will understand what im trying to ask....but I'm gonna be hopeful



I

PLEASE PLEASE help me understand this concept!

thanks in advance!

am not sure but wouldn't that have to do with O2 being dissolved or released from the hb. For eg. Decreased hydrogen (acidosis) would push the O2 saturation curve to the right. Look in your first aid under respiratory physiology I think
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Old 10-05-2015
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Originally Posted by Virgo11 View Post
Hey guys, I'd appreciate any input regarding a concept that will help me understand when, where or under what factors P02 is increased or decreased....

like in anemia, or hypoxia, CO poisoning, high altitude....

i don't know if you guys will understand what im trying to ask....but I'm gonna be hopeful


PLEASE PLEASE help me understand this concept!

thanks in advance!
Decrease in PaO2 is hypoxemia. It is a decrease in dissolved oxygen. It has nothing to do with RBCs or hemoglobin.

It is crucial that you understand that gas exchange between the alveolar air and blood in the alveolar capillaries happens because of partial pressure difference. Oxygen goes into the blood, gets dissolved (PaO2), enters RBC and binds Hb. The things that can affect PaO2, therefore, are problems with the events prior to O2 entering red blood cells. In other words, problems with RBC can not affect PaO2 because RBCs come into play after oxygen has dissolved in the blood and reached a certain partial pressure.

That leaves us with the events occurring prior to O2 entering the RBCs.

High altitude as you have mentioned. At high altitudes there is a decreased atmospheric pressure. The percentage of gases in the air is the same, its just that there is "less air" at high altitudes. So the same 21% of oxygen (by partial pressure) in the air at high altitudes but instead of atmospheric pressure being 760mmHg at sea level, it is less at higher altitudes. That decreases partial pressure of oxygen in the alveolar air also. As I have already mentioned partial pressure difference is the driving force for oxygen entering the blood, if you decrease alveolar oxygen, you decrease the gradient, less oxygen is going to diffuse into the capillaries, driving PaO2 down.

Another factor can be lungs not getting good enough blood supply. If the blood is not going to the lungs to participate in gas exchange, you will have decreased PaO2. I think it is self-explanatory. By the way, the phenomenon is called dead space.

Diffusion defects can also cause hypoxemia. If the oxygen can not cross the alveolar and capillary membranes, it is going to interfere with gas exchange. Can be caused by fibrosis, edema. DLCO will be decreased.

Any problems with ventilation. Airway obstruction, alveolar collapse, etc. Basically creating a shunt. Blood is going through the pulmonary capillaries but there is no oxygen in there to participate in gas exchange.

Increased CO2 in the blood (respiratory acidosis). Whenever there is an increase in CO2 that drives the alveolar oxygen down. The more CO2 you "diffuse out" of the blood, the more oxygen it is going to displace in the alveoli (decreasing alveolar partial pressure of oxygen).

I think thats about it.

As for the increase in PaO2 the only thing I can think of is breathing 100% oxygen for example.

Hope this helps.
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1st of all god with u in exam and hope u will do well ist of all
PARTIAL O2 PRESSURE DEPEND ON = O2 CONC IN INHALED AIR *ATOMSPHERIC PRESSURE USUALLY NORMAL LEVEL EQUAL 150 SO IF U GO TO HIGH ATTITUE DECREASE ATOMPHERIC PRESSURE DECREASE PAO2 IF WE GIVE 100% PERCENT OXYGEN INCREASE POA2 SO HELP IN TREATMENT OF HYPOXEMIA

2ND OXYGEN ALVEOLAR O2 =(ATMOSPHERIC PRESSURE(USUALLY 760)-WATER PRESSURE OF ALVEOLI(USUALLY 40))*OXYGEN LEVEL IN INSPIRED AIR USUALLY (.20%)-(Paco2 level /fixed ration .8) SO ALVEOALAR PAO2 USUALLY BETWEEN 100-105
IF U FINE ALVEOLAR PAO2 EQUAL PAO2 THAT MEAN NO PCO2 IN ALVEOL mean no well perfussion as pulmonary embolis

oxygen blood content = equal dissolved blood (pao2) +carried o2 depend on (hb conc *pao2 level ?) so on decrease partial o2 conc mean total oxygen content decreae and hgb oxygen conc level decrease
if hgb level decrease mean decrease total oxygen content but normal partial arterial o2 so normal hgb oxygen saturation
if cyanid attach to hgb decrease oxygen carry so oxygen hgb saturation decrease decrease carriedn oxygen decrease total oxygen content but normal pao2 not changed i hope these help u
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