Gas Exchange

Question 1

Downhill track of CO2

Answer 1

Tissues(highest), Venous blood, lungs, air (lowest)

Question 2

Downhill track of O2

Answer 2

Air (highest), lungs, blood, tissues.

Question 3

Px=Fx(Pb-Ph2o)

Which variables can we control?

Answer 3

Fx = Fraction of gas (100% O2)
Pb = Barometric pressure (hyperbaric chamber)

Question 4

Henry’s Law, what is it?

Answer 4

PP=[dissolved gas]/solubility coefficient

Question 5

How does hemoglobin alter Henry’s law?

Answer 5

It binds O2, which conjugates O2. This takes it out of solution for more to dissolve. It increases the O2 dissolved in blood.

Question 6

WHat is more soluble, CO2 or O2?

Answer 6

CO2, and it has a higher solubility coefficient

Question 7

What is the ideal gas law?

Answer 7

PV=nRT

Question 8

What are the implications from the ideal gas law?

Answer 8

Respiratory - If P1 is diff from P2, Volume will flow until it is equal
Anesthesia - If drugs are administered through the lungs, (high volume in the lung) partial pressures will equiilbrate

Question 9

What is fick’s law of diffusion?

Answer 9

DIffusion rates is proportional to the area, inversely proportional to the thickness of membrane

Question 10

Examples of altered diffusion

Answer 10

Atelectasis, pnemonia, pulmonary edema, pulmonary fibrosis - I think all are dealing with a thicker membrane

Question 11

What is the PO2 level in the interstitium?

What controls this number?

Answer 11

40mmHg. This is controlled by Blood flow and Tissue Metabolism

Question 12

Where is the PO2 lost from the blood?

Answer 12

Systemic capillaries

Question 13

Why is there a quick drop in PO2 levels after the pulmonary capillaries?

Answer 13

Mixture with shunt blood that has not been oxygenated

Question 14

What three factors rely on each other to control O2 diffusion?

Answer 14

Blood flow, Metabolism, Tissue PO2.
During sleep - metabolism dec, blood flow matches
During exercise - opposite

Question 15

CO2 diffusion relies on what three principles?

Answer 15

Tissue metabolism, blood flow, PCO2.
Much greater diffusion coefficient, smaller Pressure diff required
When increase in Metabolism, need increased blood flow

Question 16

How do they measure DIffusion capacity?

Answer 16

Using CO.
Give the patient a known amount and measure how much is in their alveoli after. (sensitive but non specific
O2 gets used by hemoglobbin
CO2 binds Hemoglobin tightly, doesnt get used.

Question 17

What are cases where Diffusing capacity would decrease?

Answer 17

Thickened or damaged membrane (Emphysema, pulmonary fibrosis, Interstitial lung disease, pulmonary hypertension, chronic pulmonary thromboembolism)d,
Anemia (not enough Hb to bind CO)

Question 18

What are cases where diffusing capacity would increase?

Answer 18

Polycythemia (increased RBC)

Question 19

What is the alveolar gas equation and why is it important?

Answer 19

PAO2=FiO2(Pb-Ph2o)-PaCO2/RQ
This tells you a relationship that should exist between inspired O2 and blood CO2. If you measure both and see that it is different, something is wrong.
You can alter FiO2 to treat.

Question 20

What is the difference between O2 and CO diffusion coefficient?

Answer 20

1.23

DLCO x 1.23 = DLO2