Principles of gas exchange Flashcards
effects of high altitude
at high altitude there is a decrease in total pressure
each gas in a mixture is ___ of other gases present and exerts a __ according to its concentration
independent, pressure
inspired air is humidified, water vapor has a
partial pressure
the amount of gas dissolved in a liquid is __ to partial pressure
proportional
there is a ___ relationship between partial pressure of O2 and amount dissolved
linear
ways to increase diffusion of gases
increase membrane area
increase amount dissolved
increase partial pressure difference
decrease membrane thickness
gases move by
simple diffusion
diffusing capacity
the amount of a gas the lungs can transfer to the blood (O2)
perfusion-limited
diffusing capacity is limited by blood flow
- need to increase blood flow to the lungs to increase amount of O2 delivered to the blood
diffusion-limited
diffusing capacity is limited by rate of diffusion
- need to increase the rate of diffusion to increase the amount of O2 delivered to the blood
diffusing capacity of O2 is
perfusion limited
- O2 in alveoli and the blood comes to equilibrium, therefore increasing the rate of diffusion will not add O2 to the blood, so must increase blood flow
in disease conditions, if the O2 in the blood does not come to equilibrium with the alveoli, the diffusion capacity of O2 would now be
diffusion limited
O2 in alveoli come to equilibrium 1/3 of the way through the capillary so even if blood velocity increases (exercise) the O2 in the blood will come to equilibrium with alveoli
important
the pulmonary circulation is a __ pressure system compared to the systemic circulation
low
congestive (left) heart failure
blood builds up in pulmonary circulation, pulmonary capillary pressure increases, filtration at capillaries, pulmonary edema, poor gas exchange (potential death)
recruitment
open more capilaries
if there is not decrease in TPR during exercise then
increase MAP, filtration in lungs, pulmonary edema, death
distension
increase radius of each capillary
3 benefits of recruitment and distension
decreased resistance causes decreased pressure and prevents filtration
decreases velocity of blood flow so more time for gas exchange
increases surface area for gas exchange
effect of autonomic NS on pulmonary vascular resistance
not an important regulator
effect of hypoxia (low O2)
always want to match air flow and blood flow
- decreased air flow = decreased O2 = vasoconstriction
- decrease air flow leads to decreased blood flow
PO2 in the air is 160 mmHg but PO2 in alveoli is 105 mmHG, why the decrease
mine with dead space air
mixing with residual volume air
air is humidified (water vapor added)
shunting
some blood does not go past alveoli, the PO2 in this blood stays at PO = 40 mmHg
