L40: Altitude/hypoxemia/exercise

Question 1

How does high altitude affect the respiratory system?

Answer 1

Hypoxia and decreased PaO2.

Question 2

What equation would you use to calculate the PO2 of humidified inspired air?

Answer 2

Dalton’s law of PP of a gas:
Px= (Pb - PH20) x F
Pb= Barometric pressure
PH20= 47 (memorize this number)
F= 0.21 (Memorize this number)

Question 3

What is the most significant response to high altitude?

Answer 3

Increased ventilation rate

Question 4

How can hypoxemia be remedied? How does this affect PIO2, PAO2, PaO2?

Answer 4

Supplemental oxygen
PIO2 is increased
PAO2 is increased
PaO2 is increased after equilibration

Question 5

What is polycythemia?

Answer 5

High altitude produces increased RBCs, increased Hb, increased O2 carrying capacity= increased total blood O2 content.

• Advantageous in terms of O2 transport
• Disadvantageous in terms of increased blood viscosity (due to increased RBC, which will increase resistance)

Question 6

Why is 2,3 DPG a disadvantage for the lungs?

Answer 6

More difficult to load up pulmonary capillary blood with O2 since Hb now has decreased affinity.

Question 7

What is the A-a gradient?

Answer 7

The difference between PAO2 and PaO2

Question 8

What does a right-left shunt always result in?

Answer 8

Hypoxemia because shunted blood bypasses ventilated alveoli

• A-a gradient is increased
• Supplementl oxygen will not help since it will only raise the PO2 of non-shunted blood.

Question 9

How do mean values for PaO2 and PaCO2 change with exercise? Why?

Answer 9

They do not change because there is increased ventilation rate and increased efficiency of gas exchange.

Question 10

How does Venous PCO2 change during exercise? What does this mean?

Answer 10

It must increase because the skeletal muscle is adding more CO2 than normal to the venous blood. Ventilation must increase to clear out this CO2.

Question 11

How does exercise affect the O2 Hb dissociation curve?

Answer 11

It shifts to the right.