Gas Exchange Flashcards
Dalton’s law of partial gas pressures
pressure of a gas is directly proprotional to the concentration of it’s molecules
How do obtain the dry gas pressure
Fractional concentration (barometric pressure - water vapor pressure)
how do you calculate partial pressure
concentration of dissolved gas / solubility coefficient
What happens if P1 > P2
gas exchange will take place until equilibiurm is achieved
How do anesthetic gases work
they diffuse into blood until the partial pressures in alveoli and blood are equal
Fick’s law of diffusion
the amount of gas that moves across a tissue sheet is porportional to the area, but inversely proportional to the thickness
How do you calculate diffusion
(change in pressure x area x solubility of gas) / (thickness x square root of (molecule water of gas))
blood perfusion through capillaries unde rnormal conditions
rapid rise in blood PO2
blood perfusion through capillaries during exercise
as much as 20 times O2 is required
no rapid rise
how does diffusing capiacity of O2 change during exercise
increases almost 3 fold
atelectasis
collapse of lung tissue, damage to membrane. decreases diffusion because increase in thickenss
pneumonia
increases thickness, decreases diffusion
pulmonary edema
happens in cardiac problems, can be coughing up pink stuff, very severe
pumonary fibrosis
increased thickness, decreases diffusion
why is systemic blood PO2 less than pulmonary capillary blood
shunt from bronchial circulation
what happens to O2 if blood flow through a tissue is increased
more O2 is transported to the tissue, and PO2 becomes higher
What happens to O2 if blood flow through a tissue is decreasd
decreased O2 is transported into the tissue, and the tissue PO2 becomes lower
How is CO2 diffusion different from O2 diffusion
opposite direction
much greater diffusion coefficent
much smaller change in partial pressure is needed
What happens to CO2 if blood flow through a tissue increases
decreases CO2
What happens to CO2 if blood flow through a tissue decreases
increases CO2
Lung diffusing capacity
common measurement of lung’s ability to transfer cases.
How do you calculate lung diffusing capcity
CO uptake / alveolar PCO2
What are some reasons why you would have decreased lung diffusing capcity (DLCO)
emphaysema, pulmonary fibrosis, pulmonary hypertension, chronic pulmonary thromboenbolism, anemia
What is a reason why you would have increased lung diffusing capacity (DLCO)
polycythemia
