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  #1  
Old 06-26-2011
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Lungs Oxygen tension at pulmonary capillaries (Graph)

A 28 y/o medical student has a fourfold increase in CO (Cardiac output) during strenuous exercise. Which of the curves best represents the changes in oxygen tension that occur as blood flows from the arterial to the venous end of the pulmonary capillaries in this student?

Oxygen tension at pulmonary capillaries (Graph)-graph.png
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A) A
B) B
C) C
D) D
E) E

Last edited by bebix; 06-26-2011 at 12:50 PM. Reason: added (Cardiac output)
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  #2  
Old 06-26-2011
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i think it is A
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Quote:
Originally Posted by bebix View Post
A 28 y/o medical student has a fourfold increase in CO during strenuous exercise. Which of the curves best represents the changes in oxygen tension that occur as blood flows from the arterial to the venous end of the pulmonary capillaries in this student?

Attachment 1618
click image to enlarge

A) A
B) B
C) C
D) D
E) E
i think its curve D
in A n B max oxygen tension is reached by the end of aterial end
in curve C n E the oxygen tension is too low
i l go with D as the blood flows from pulmonary artery to pulm. vein there is gradual increase in oxygen tension n the max tension appears in pulm vein
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i will go with C. ....because CO has very high affinty to Hb as compared to O2 and 4 times increase in the CO indicates it is CO poisoning...so the normal oxygen pressure in the air will not replace CO completely from Hb. So the blood in the pulm vein will nt be fully saturated....Also this is the reason we use hyperbaric oxygen to treat CO poisoning....
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i think the answer is C!!
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i think its c
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Default E

i think the question shud be "co2" not "co".
I gues the ans is E coz in strenuous ex the venous 02 is decreased coz tissue draws more blood and arterial 02 remains same due to hyperventilation

PS : i meant systemic venous and arterial o2 not pulmonary

Last edited by rsin21; 06-26-2011 at 12:44 PM.
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Originally Posted by rsin21 View Post
i think the question shud be "co2" not "co".
I gues the ans is E coz in strenuous ex the venous 02 is decreased coz tissue draws more blood and arterial 02 remains same due to hyperventilation

PS : i meant systemic venous and arterial o2 not pulmonary
increase in CO during strenuous exercise..... increase in CARDIAC OUTPUT during strenuous exercise....
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Quote:
Originally Posted by bebix View Post
increase in CO during strenuous exercise..... increase in CARDIAC OUTPUT during strenuous exercise....
oops ....wil stil go vid E
wats d ans???
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Old 06-26-2011
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Default EEE

would go with E,
CO has very high affinity to Hb, and it shift to the left the O2 Hb dissociation curve
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Quote:
Originally Posted by bebix View Post
increase in CO during strenuous exercise..... increase in CARDIAC OUTPUT during strenuous exercise....
every1 is takin CO as carbon monoxide...i gues m not alone here
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Originally Posted by laurier View Post
would go with E,
CO has very high affinity to Hb, and it shift to the left the O2 Hb dissociation curve
CO = Cardiac Output....the poor guy is just doing exercise....if the CO2 or the carbon monoxide increases by 4x....he would probably be dead...
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Guys, why would it be Carbon Monoxide after it clearly states strenuous exercise? I don't think the person is exercising in his closed garage...

I also think its D)
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hihi..I was thinking CO is carbonmonoxide!!!
thax for correcting me
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guys its not a oxygen saturation curve...thr is not left or right shift
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Quote:
Originally Posted by rsin21 View Post
every1 is takin CO as carbon monoxide...i gues m not alone here
hahaha...I know!!!
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Quote:
Originally Posted by patelMD View Post
Guys, why would it be Carbon Monoxide after it clearly states strenuous exercise? I don't think the person is exercising in his closed garage...

I also think its D)
hahahaha.....good one!!!
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I will go for curve A
...want to know the ans bebix....:sorry:
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Correct Answer correct answer

The correct answer is E)

The PO2 of mixed venous blood entering the pulmonary capillaries is normally about 40mmHg, and the PO2 at the venous end of the capillaries is normally equal to that of the alveolar gas (104 mmHg). Under normal conditions, the capillary PO2 virtually reaches that of alveolar gas when the red cell is about one-third of the way along the capillary (Curve B => NORMAL curve)

During exercise, because of the faster flow of blood through the lungs, the O2 has less time to diffuse into the pulmonary capillary blood, therefore, the PO2 of the capillary blood does not reach its maximum values until it reaches the venous end of the pulmonary capillaries (curve D vs E)
Now, Curve E is the correct one, because shows a low PO2 of 25mmHg at the arterial end of the pulmonary capillaries, due to increased muscular blood flow and muscular oxygen extraction.
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  #20  
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good question dr!!
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Listening Good Q but if i may say...

Quote:
Originally Posted by bebix View Post
The correct answer is E)

The PO2 of mixed venous blood entering the pulmonary capillaries is normally about 40mmHg, and the PO2 at the venous end of the capillaries is normally equal to that of the alveolar gas (104 mmHg). Under normal conditions, the capillary PO2 virtually reaches that of alveolar gas when the red cell is about one-third of the way along the capillary (Curve B => NORMAL curve)

During exercise, because of the faster flow of blood through the lungs, the O2 has less time to diffuse into the pulmonary capillary blood, therefore, the PO2 of the capillary blood does not reach its maximum values until it reaches the venous end of the pulmonary capillaries (curve D vs E)
Now, Curve E is the correct one, because shows a low PO2 of 25mmHg at the arterial end of the pulmonary capillaries, due to increased muscular blood flow and muscular oxygen extraction.

I believe I read somewhere that venous Po2 is not affected by excersise and that the increase in oxygen extraction is reflected as a decrease in oxygen saturation thus D would be an answer!
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Originally Posted by Drothman2010 View Post
I believe I read somewhere that venous Po2 is not affected by excersise and that the increase in oxygen extraction is reflected as a decrease in oxygen saturation thus D would be an answer!
The PO2 of 25 mmHg represent the mixed venous blood entering the capillary. The correct answer is E (this question is from Guyton)
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Quote:
Originally Posted by Drothman2010 View Post
I believe I read somewhere that venous Po2 is not affected by excersise and that the increase in oxygen extraction is reflected as a decrease in oxygen saturation thus D would be an answer!
@Drothman2010, here is the complete explanation (guyton)

Oxygen tension at pulmonary capillaries (Graph)-alveoli.jpg

The top part of figure shows a pulmonary alveolus adjacent to a pulmonary capillary, demonstrating diffusion of oxygen molecules between the alveolar air and the pulmonary blood. The Po2 of the gaseous oxygen in the alveolus averages 104 mm Hg, whereas the Po2 of the venous blood entering the pulmonary capillary at its arterial end averages only 40 mm Hg because a large amount of oxygen was removed from this blood as it passed through the peripheral tissues. Therefore, the initial pressure difference that causes oxygen to diffuse into the pulmonary capillary is 104 40, or 64 mm Hg. In the graph at the bottom of the figure, the curve shows the rapid rise in blood Po2 as the blood passes through the capillary; the blood Po2 rises almost to that of the alveolar air by the time the blood has moved a third of the distance through the capillary, becoming almost 104 mm Hg.

During exercise, pulmonary blood flow increases substantially, and the pulmonary capillary blood volume also expands by a combination of capillary recruitment and distention. However, the relative increase in cardiac output outstrips that of capillary volumen such that mean transit time falls to about 0.4 to 0.5 seconds. In addition, because mixed venous PO2 falls during exercise, it takes longer than 0.25 seconds for capillary PO2 to reach alveolar values
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Originally Posted by bebix View Post
The correct answer is E)

The PO2 of mixed venous blood entering the pulmonary capillaries is normally about 40mmHg, and the PO2 at the venous end of the capillaries is normally equal to that of the alveolar gas (104 mmHg). Under normal conditions, the capillary PO2 virtually reaches that of alveolar gas when the red cell is about one-third of the way along the capillary (Curve B => NORMAL curve)

During exercise, because of the faster flow of blood through the lungs, the O2 has less time to diffuse into the pulmonary capillary blood, therefore, the PO2 of the capillary blood does not reach its maximum values until it reaches the venous end of the pulmonary capillaries (curve D vs E)
Now, Curve E is the correct one, because shows a low PO2 of 25mmHg at the arterial end of the pulmonary capillaries, due to increased muscular blood flow and muscular oxygen extraction.
wouldnt an increase in exercise that causes CO to increase 4x also increase the respiratory rate, thereby increasing the ventilation and oxygenation of the blood..kindly correct me where m goin wrong...
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Default d

Quote:
Originally Posted by bebix View Post
A 28 y/o medical student has a fourfold increase in CO (Cardiac output) during strenuous exercise. Which of the curves best represents the changes in oxygen tension that occur as blood flows from the arterial to the venous end of the pulmonary capillaries in this student?

Attachment 1618
click image to enlarge

A) A
B) B
C) C
D) D
E) E
would go with D
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  #26  
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wouldnt an increase in exercise that causes CO to increase 4x also increase the respiratory rate, thereby increasing the ventilation and oxygenation of the blood..kindly correct me where m goin wrong...
of course!!!...more extraction...we need more O2...CO and HR goes up...
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in what case answer would be D ?
just asking
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in what case answer would be D ?
just asking
in cases where you have problems with diffusion (not severe problems though)...
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i think i have to ask ma bro to send me my guyton from ma country for these types of graphs...if its nt in q-book and F.A then there should be a lot of other graphs which we didnt see after final year..
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i think i have to ask ma bro to send me my guyton from ma country for these types of graphs...if its nt in q-book and F.A then there should be a lot of other graphs which we didnt see after final year..
me too
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Originally Posted by IKR123 View Post
i think i have to ask ma bro to send me my guyton from ma country for these types of graphs...if its nt in q-book and F.A then there should be a lot of other graphs which we didnt see after final year..
If its not in Kaplan or FA, you dont need it!
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