resp-5 gas properties Flashcards
what drives diffusion
different partial pressures
what is daltons law
total pressure is the sum of individual pressures (partial pressures)
what ranges is oxygen Po2
150-160mmHg
21%
ficks law of diffusion–> proportionalities
diffusion is proportional to area, diffusion constant, (P1-p2) and inverse to thickness
what is the diffusion constant
the amount of gas transferred between the alveoli and the blood/unit time
what is the diffusion constant proportional to
gas solubility
does co2 or o2 have a higher diffusion constant
co2
more soluble, same molecular weight
what entails diffusion constant
proportional to solubility, inversely proportional to molecular weight
henrys law
the amount of gas dissolved in a liquid is directly proportional to the partial pressure of gas in which the liquid is in equilibrium
what determines concentration of a gas in liquid (2 factors)
their solubility and their partial pressure
why is Po2 in air> po2 in alveoli
humidification of air in resp (more water, relative percentage of other molecules decreases)
loss O2 to blood diffusion (hemoglobin)
mixing inspired air with alveolar air (functional residual capacity)
what determines alveolar po2 and pco2
Po2 and PCO2 in atm
alveolar ventilation
metabolic rate (more you use, more you take)
perfusion
increasing alveolar ventilation does what do alveolar po2 and pco2
increase alveolar po2 and decrease alveolar pco2
increasing metabolic rate does what do alveolar po2 and pco2
decrease alveolar po2 and increase alveolar pco2
what determines arterial levels of gases
partial pressure of gas in alveoli
when does getting the first bit of o2 happen (in healthy person)
in the first third of the capillary system
what is cardiac output
volume of blood pumped by the heart per minute
does systemic or pulmonary system have higher pressure
systemic higher pressure
why is pulmonary low pressure system
only pumps blood to top of lung, shorter and wider vessels
why is the pulmonary high compliance vessels
lots of arterioles with low restine tone
thin walls and little smooth muscle can accept large amount of blood
can dilate in increase to pressure
when would alveolar capillaries collaps
if capillary pressure falls below
alveolar pressure, the capillaries close off, diverting blood to other pulmonary
capillary beds with higher pressures
what is the ventilation/perfusion ratio (V/Q0
balance
between LUNG ventilation (O2 ATM→ALVEOLI / CO2
ALVEOLI→ATM) and LUNG perfusion (O2 ALVEOLI → BLOOD
/CO2 BLOOD → ALVEOLI).
what is a major factor that the ventilation/pefusion ratio affects
the alveolar and arterial elvels of Po2 and Pco2
more ventilation does what to po2 and pco2
more closely alveolar po2 and pco2 will approach their respective valuesof the insipired air
more perfusion does what to po2 and pco2
the more closely the composition of
local alveolar air will approach that of mixed-venous blood.
what does high V/Q ratio mean
high ventilation
low perfusion
what causes a high V/Q ratio
alveolar/physiologic dead space
regions where air reaching them is not taken up by blood (underperfused, like from blood clot)
what is ventilation
the air that reaches the alveoli
what is perfusion
the blood that reaches the alveoli
What are relative po2 and pco2 in high V/Q ratio
high po2 low pco2
similarto air
what is anatomical dead space
volume of conducting airways that do not participate in gas exchange
what is alveolar dead space
regions of lung with high V/Q ratios. Regions that are relatively over
ventilated (UNDERPERFUSED) so that a portion of the fresh air reaching these alveoli
can not be taken up by the blood.
what could cause high V/Q ratio
blood clot, preventing perfusion
what could cause a low V/Q ratio
airway obstruction
What are relative po2 and pco2 in low V/Q ratio
low po2 high pco2, no fresh air coming in and cant remove co2
what is a shunt
portion of venous blood that doesnt get oxygenated and goes back to arterial blood
what does the local V/Q ratio determine
local alveolar Po2 and Pco2
where is perfusion greatest in the lungs and why
base of lungs
more weight at bottom and more air goes there
what does perfusion depend on
gravity and posture
po2 co2 relationship at top of lungs
high po2
low pco2
po2 co2 relationship at bottom of lungs
low po2
high pco2
does blood flow or ventilation increase more as you go lower in the lungs
blood flow increases more dramatically
how does V/Q change in top and bottom of lungs
top of lungs has high V/Q
bottom of lungs has low V/Q
what is pulmonary hypoxic vasoconstriction
low O2 to capillary, vasoconstrict to increase flow to an alveoli that works
what happens when theres decreased blood flow to a region of the lungs
bronchoconstriction (less co2 carried to the alveoli) so there is decreased air flow and it is rediverted to a better area
where is circuclation is there the most similar amount of pco2 and po2
venous
what determines alveolar po2 (3)
PO2 of atmospheric air
the rate of alveolar ventilation
the rate of total-body oxygen consumption
