3.3.1 Hypoxia

Question 1

What is the pathway for O₂ through the body?

Answer 1

Question 2

What are the normal sea level gas values for alveolar air, veins, and arteries?

Answer 2

Question 3

What is an example of low inspired PO₂

Answer 3

High altitude (due to the drop in barometric pressure)

Question 4

Are are the effects of high altitude on PIO2, PAO2, PaO2, PvO2, CaO2?

Answer 4

Question 5

In a high altitude scenario, how can you calculate PAO2 with normal ventilation?

Answer 5

If ventilation is normal, you can assume that the PACO2 will be fourty. Then, you plug it into the following equation:

PAO2 = 60 - (40 * 1.2) = 12 mm Hg

Question 6

Once you know the PAO2, how can you find the SaO2 and CaO2?

Answer 6

The ODC (with O2 content and O2 saturation)

Question 7

What pathway will lead to hyperventilation due to the reduced PaO2?

Answer 7

Peripheral (Central does not respond to PaO2)

Question 8

For a given PIO₂, a decrease in PACO₂ will result in what change in PAO₂?

Answer 8

Increase in PAO₂

Question 9

If you hyperventilate at a high altitude and blow your PACO2 down to 20, what will be the PAO2?

Answer 9

PAO2 = 60 - (20 *1.2) = 36 mm Hg

Question 10

In addition to blowing off CO2, what will aid in increasing the oxygen delivery to the tissues?

Answer 10

The alkalosis as a result of decreased CO2 will shift the ODC in such a way that Hb will saturate better at lower PO2 levels.

Question 11

What CV factor increases O2 tissue delivery in altitude hypoxia?

Answer 11

Q, cardiac output

Question 12

In what scenario could PIO2 be normal but PAO2 be low?

Answer 12

Hypoventilation

Question 13

Hypoventilation results in an increase in which alveolar gas value? decrease in what?

Answer 13

Increase PACO2

Decrease PAO2

Question 14

In long term hypoventilation, how will a person compensate for the resulting respiratory acidosis?

Answer 14

Metabolically, they will retain HCO3 to shift the pH up towards 7.4