Hypoxemia

Question 1

Hypoxemia is?

Causes?

Answer 1

insuff O2 of arterial blood

Caused by: ºV/ºQ mismatch

limited diffusion

central hypovent

↓ P_IO₂

shunt (ºV/ºQ = 0)

Question 2

ºV/ºQ Mismatch affects PaO2 how?

A-a O2 how?

Answer 2

↓ PaO2

↑ A-a O2 gradient

Question 3

ºV/ºQ Mismatch can be normalized how?

Answer 3

O2 supplementation

Question 4

Limited Diffusion Hypoxemia caused by?

Answer 4

exercise (↓ transit time in capillaries)

↓ D_L: edema, fibrosis, emphy, CHF

Question 5

Central Hypovent Hypoxemia caused by?

Answer 5

drug OD

anesthesia

brain damage

Question 6

Central Hypovent Hypoxemia results in?

Answer 6

↓ V_T and V_A

↓ PaO2

↑ PaCO2

Question 7

↓ P_IO2 Hypoxemia caused by? (2)

Results in?

Answer 7

1) high altitude:

results in: hypervent, ↓ PaCO2

2) rebreathing:

Results in: hypervent, ↓ P_IO2, ↑ PaCO2

Question 8

Shunt Hypoxemia (ºV/ºQ = 0) caused by?

Results in?

Answer 8

complete collapse of lung/alveoli

R-L heart shunt (mixed blood)

↑ A-a O2 gradient

*does not respond to O2 supplement

Question 9

High altitude adaptation possible how? (2)

Answer 9

1) hyperventilation
2) polycythemia (↑ RBCs and [2,3 DPG])

Question 10

Hyperventilation caused by?

Consequences?

Answer 10

hypoxic stim of peripheral chemoreceptors

respiratory alkalosis (low PaCO2):

CSF pH ↑ to counteract hypervent for few days

Question 11

Polycythemia caused by?

Results in?

Answer 11

release of erythropoietin from kidney

↑ [O2]

↑ viscosity, puts extra load on heart

Question 12

Results of ↑ 2,3 DPG?

Answer 12

↓ affinity of Hb for O2:

Ѧ dissociaton curve shifts right

NOT reversed at lungs:

Ѧ O2 loading inhibited