Lecture 37+38 Flashcards
what is the ideal V/Q ratio
4/5 or 0.80
V = 4 L /min Q = 5L/min
compliance of the lung?
The apex of the lung is more compliant compared to the base of the lung
the apex of the lung is always distended
ventilation vs perfusion at the apex and base of lung?
where is gas exchange more efficient?
ventilation is higher at the bottom of the lung compared to the top
perfusion is higher at the bottom compared to the top
The V/Q ratio is higher at the apex compared to the base
gas exchange is more efficient at the apex of the lungs compared to the base
what happens for low V/Q ratios and high V/Q ratios
low = hypoxic vasoconstriction
high = bronchoconstriction
how does altering V/Q effect PO2 and PCO2?
low V/Q = low PO2 and high PCO2
high V/Q = high PO2 and low PCO2
A-a O2 gradient equation
PAO2 - PaO2
What increases the A-a O2 gradient?
reginal low V/Q ratio
anatomic shunt
diffusion block
what leads to hypoxemia if the A-a gradient is normal?
hypoventilation
what leads to hypoxemia if the A-a gradient is abnormal and it is not corrected with oxygen therapy?
shunt
what leads to hypoxemia if the A-a gradient is abnormal and it is corrected with oxygen therapy?
It is either a V/Q mismatch or diffusion problem
what is the diagnosis if the DL co is normal or abnormal?
normal = V/Q mismatch
abnormal = diffusion problem
what does increased altitude do to hypoxemia?
increases it!
ventilation is increased
equation for saturation
SO2 = HbO2 content / HbO2 capacity x 100%
O2 saturation curve?
loading phase? unloading phase?
loading phase: O2 content and saturation remains fairly constant over a range of partial pressures (lungs)
unloading: steep portion of the curve that allows for the release of O2 into tissues
saturation curve and P50?
what does an increase or decrease in P50 do?
P50 is when Hb is at 50 percent capacity
decrease: left shift (harder to unload)
increase: right shift (easier to unload)