Lecture 13 - Ventilation - Perfusion (V/Q) Flashcards
PIO2 (Partial pressure of inspired O2) at sea level is about ____mmHg
150mmHg
Systemic PO2 is about ____mmHg
95mmHg
Normal shunting of blood accounts for about ___-___% of Cardiac Output (CO)
2-5%
If hypoxemia is not corrected with _____ _____, then it is likely caused by a shunt (e.g. Tetrology of Fallot).
Supplemental O2
Respiratory Exchange Ratio (R) = ______ production / ______ consumption, and we assume this to be ____.
CO2 production (VCO2) / O2 consumption (VO2)
We assume this to be 0.8.
PaO2 - PAO2 gradient (aka A-a gradient) is usually between ___-___mmHg.
5-15mmHg
Treating comatose patients with hypoxemia from Hypoventialtion will increase their ____ saturation, but the ______ will remain elevated bc their Ventilation has not improved, and the patient will remain comatose
PaCO2
The most common cause of hypoxemia is ______-______ mismatch.
Ventilation - Perfusion mismatch
The V/Q ratio describes the rate of _____ / the rate of _____. If Q decreases while V remains the same, the ratio increases, and PAO2 will ______ (increase or decrease?) while PACO2 will ______ (increase or decrease?). The opposite is true if V decreases while Q remains. Remember that normal V/Q ratio is about ___.
Ventilation/Perfusion
PAO2 will increase
PACO2 will decrease
1
Keep in mind the V/Q ratio at the apex of the lung differs from the V/Q ratio at the base. How so, and why?
Ventilation and Perfusion are both greater at the base of the lung, but the difference in Perfusion between the Apex and base is GREATER than the difference in ventilation. Thus, V/Q is greatest at the Apex, which means PAO2 is highest and PACO2 is lowest, while V/Q is lowest at the Base, which means PAO2 is lowest and PACO2 is highest.
Because V and Q are both greatest in the Base and Lowest in the Apex of the lungs, where does the majority of gas exchange occur?
At the Base, which should make sense since most of the ventilation and perfusion are occurring there.
