RS5 Causes of Hypoxemia

Question 1

What are the 3 determinants of pulmonary vascular resistance?

Answer 1

Gravity
Lung volume
Hypoxic vasoconstriction

Question 2

Describe the hydrostatic pressure differences in the lung

Answer 2

It goes low to high (top to bottom). The bottom of the lungs have the greatest hydrostatic pressure

Question 3

Systemic arteries ___ in response to perfusion with blood low oxygen

Answer 3

dilate

Question 4

Pulmonary arteries ____ in response to alveolar hypoxia but not to perfusion with blood low in oxygen

Answer 4

constrict

Question 5

Deadspace unit

Answer 5

Normal ventilation
No pefusions
The alveoli is working great, but the capillary is not

Question 6

Shunt unit

Answer 6

No ventilation (no alveolar function)
Perfusion (blood vessel is fine)

Question 7

Silent unit

Answer 7

Neither vent or perf

Question 8

Draw the 4 types of V:P relationships

Question 9

In the healthy adult, a PaO2 above ___mmHg is considered normal while breathing room air at sea level

Answer 9

80

Question 10

What are the 2 exceptions to normal PaO2?

Answer 10

Newborn infant 50-70mmHg
Subtract 1mmHg for every year over 60years of age

Question 11

Normal PaCo2 ___-___mmHg

Answer 11

35-45mmHg

Question 12

Hyperventilation PaCo2

Answer 12

<35mmHg

Question 13

Hypoventilation PaCo2

Answer 13

> 45mmHg

Question 14

Expected values
PaO2 = __mmHg
PaCo2 = ___mmHg

Answer 14

100
40

Question 15

Hypoxemia

Answer 15

A decrease in the partial pressure of oxygen in the arterial blood PaO2 < 80mmHg

Question 16

What are the 5 causes of hypoxemia PaO2 < 80mmHg

Answer 16

Hypoventilation
Diffusion impairment
Ventilation-perf relationship
Reduction of inspired O2
Shunt

Question 17

Alveolar Air Equation

Answer 17

PAO2 = PIO2 - PACo2/R

Question 18

Diffusion impairment

Answer 18

The equilibrium does not occur between the PO2 in the pulmonary capillary blood and alveolar gas

Question 19

V:P inequality

Answer 19

vent and blood flow are mismatched in various regions of the lung with the result that gas transfer becomes inefficient

Question 20

VA =
Q =

Answer 20

alveolar ventilation
perfusion (blood flow)

Question 21

VA/Q values for Deadspace, normal, and shunt

Answer 21

Deadspace: infinity
1
Shunt: 0

Question 22

Reduction of inspired PO2

Answer 22

The alveolar PO2 and thus the arterial PO2 will be decreases

Question 23

Shunt

Answer 23

Blood reaches the arterial system without passing through ventilated regions

Question 24

How can we distinguish between the 5 causes of hypoexmia?

Answer 24

A-ADO2

Question 25

Normal value A-aDO2?

Answer 25

< 10 to 15mmHg

Question 26

What are the 5 causes of hypoxemia and their A-aDO2?

Answer 26

Reduction of inspired O2 (Normal)
Hypoventilation (Normal)
Diffusion impairment (Increase)
V-P inequality (Increase)
Shunt (Increase)