Diffusion and Perfusion Flashcards
What is the equation for arterial oxygen content?
C(a[O2]) = Hb-bound O2 + freely-dissolved O2
The P(a[O2]) represents only ________.
the dissolved oxygen, not the oxygen bound to hemoglobin
The pressure gradient that drives oxygen into the capillaries is driven by __________.
the concentration of free oxygen in the blood, not that which is bound to hemoglobin
Exercise leads to a shallower oxygenation curve, because ___________.
blood moves faster through the capillaries, thus there is less time for oxygen to diffuse into the blood
Disorders of diffusion can affect ________ but not __________.
oxygen concentration; CO2 concentration
Minute perfusion is __________.
the amount of blood going through the lung capillary network in one minute (so = cardiac output)
Low oxygen concentration in the blood causes the pulmonary vessels to ________.
constrict (allowing for slower flow and hence more diffusion)
Factors that influence perfusion include _________.
gravity, capillary recruitment, and oxygen tension
What is the V/Q ratio?
The ratio of ventilation to perfusion in a lung unit
A lung unit with an obstructed airway would have a ______ V/Q ratio.
low
A lung unit with an obstructed capillary would have a ______ V/Q ratio.
high
If one lung unit has a low V/Q ratio, then the body will ___________.
increase the V/Q ratio in another unit to compensate
_________ saturation limits how much oxygen can be added by increasing the V/Q ratio.
Hemoglobin
V/Q mismatch will affect ______ levels but not _________ levels.
P(a[O2]); P(a[CO2])
Gravity can cause V/Q mismatch, because perfusion at the bottom of the lungs is ______ than the top, while ventilation at the bottom is only ______ than the top.
6 times greater; 2.5 times greater
To correct for abnormally high V/Q, the body can ___________.
bronchoconstrict to decrease V or vasodilate to increase Q
High V/Q ratios lead to __________ CO2 in the alveoli.
decreased
A shunt is a __________.
blocked alveoli (such as from pneumonia or other infiltrate)
What is the conversion between mM and Pa(O2) Torr?
0.0013 mM/Torr
What is Fick’s law?
Flux(of gas) = ∆P x (A/d) x k ∆P = difference in pressure across membrane A = surface area d = membrane thickness k = diffusion constant
The diffusible area of the lungs = ________.
roughly 100 m^2
Under resting conditions in a healthy individual, the Pa(O2) is 100 Torr when the blood is _______ through the capillary bed of the lungs.
halfway through
Both emphysema and interstitial lung disease are considered _______ disorders, because _________.
diffusion; emphysema destroys the surface area through which gas exchange occurs (A) and interstitial lung disease increases the distance (d)
Exercise causes the pulmonary blood vessels to _________.
dilate
For a healthy person, Ca(O2) is roughly _________.
9.1 mM or 20.7 ml O2 / 100 ml blood
One lung has about ______ alveoli.
300 million
______ is the most important vasoconstrictor in the pulmonary blood vessels and ______ is the most important vasodilator.
Thromboxane; prostacyclin
Increasing the V/Q ratio to much greater than 1 does not ___________.
increase Ca(O2) because hemoglobin is saturated when V/Q is 1
There are two local controls of V/Q mismatch: _____________.
high V/Q leads to decreased alveolar P(CO2), which leads to bronchoconstriction, thus decreasing V/Q; and low V/Q leads to low P(O2) which causes vasoconstriction and subsequent raising of V/Q
