Lecture 14 - Ventilation/Perfusion Matching - Midterm 2

Question 1

blood has to deal with gravity air does not. Facts of cap

Answer 1

fact

Question 2

what symbol is blood flow represented by

Answer 2

Represented by Q (with a dot on top)
The dot on top represents rate (mls/min)

Question 3

VA/Q?

Answer 3

(ratio between alveolar ventilation and blood flood)

Question 4

what is the ideal VA/Q

Answer 4

we want this to be 1 ideally

Question 5

where is VA/Q high

Answer 5

at the top of the lung and low at the bottom of the lung

Question 6

what happens if there is too much blood

Answer 6

there will actually be less oxygen since the blood is taking oxygen at a faster rate than the alveoli is supplying

causes the PALV to drop, which also causes the Pa (arterial pressure) to drop as well

Question 7

what happens when VA/Q is not equal to 1 (or not ideal)

Answer 7

end up with less partial pressure of oxygen in the blood (leading to less total oxygen in blood) = not efficient gas exchange

Question 8

how do we make VA/Q ideal

Answer 8

drop in arterial oxygen is sensed by the body

This leads to a reflex vasoconstriction (blood vessels get smaller)

This decreases Q (blood flow) (volume is decreased, so pressure is increased, and the blood that wants to come in can’t since the pressure is to high; this blood actually goes to the top of the lungs so now there is an even distribution)

Now, the blood flow is coming in at a rate that matches VA (alveolar ventilation)

If VA/Q was less than 1, now that the Q is lower, VA/Q becomes 1

Blood flow is matched to air flow