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Flashcards in Pulmonary Gas Exchange Deck (11)
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1
Q

Ficks law of diffusion

A

Physical properties of membrane

Physiochemical properties of gas

PRessure gradient

All effect the diffusion

Thicker = less 
Area = more 

Molecular weight increase - less
More soluble - more

More pressure gradient - increase more (partial pressure of the gas on one side versus the other)

2
Q

Alveolar capillary membrane

A

Alveolar epithelium (where surfactant is, etc.)

On capillary side side - alveolar capillary endothelium cells

Basement membrane in between

3
Q

Solubilities of CO2 vs. O2 and effect

A

CO2 heavier

CO2 also muh more soluble

Means that CO2 diffuses much easier than O2

4
Q

Pressure gradient

A

PO2 venous blood about 40 and alveolar gas about 100

pCO2 is 46 in venous blood to about 40 in alveolar gas

Pressure gradient greater for oxygen

5
Q

Capillary blood transit

A

Less than .75 seconds to go through capillary

Time is shortened during exercise so about .25

Normally, saturated with O2 after about .25 seconds

Curve falltened in obstructive lung dz and takes longer to become oxygen saturated…could get hypoxemia during exercise

6
Q

Capillary reserve time

A

Amoutn of time it takes between O2 saturation and end of time in the capillary

7
Q

CO2 transfer along the capillary

A

Normally takes about .25 seconds

Abnormal would take longer

Exercise still shortens the amount of time

Edema or fibrosis could increase thickness..or emphysema could make abnormal

CO2 almost always gets out during normal resting condition

8
Q

Diffusion capacity

A

DL= diffusion rate /(P1-P2)

9
Q

Rationale for using carbon monoxide for DL, and what are 2 determinants

A

PCO in the blood is zero

Diffusion pattern of CO is similar to that of O2

Membrane and hemoglobin

10
Q

How does hemoglobin effect DL?

A

The rate of reaction with hemoglobin and the blood volume in the alveolar capillaries are both increasing the DL

Hemoglobin is EQUALLY important to the membrane

11
Q

Things that cause low DL

A

Increase the thickness
Decrease the SA
Decreased uptake by erythrocytes (anemia)
Ventilation-perfusion mismatch