Alveolar Blood-Gas Exchange

Question 1

Normal difference between PAO2 and PaO2? (A-a Gradient)?

Answer 1

Normal A-a gradient: 10-15 mmHg

Question 2

What does an ⬆️A-a Gradient indicate in terms of oxygenation?

Answer 2

1. Hypoxemia

Question 3

What is the PIO2 at sea level?

Answer 3

150 mmHg

Question 4

Formula to calculate PACO2?

Answer 4

PACO2 = Metabolic CO2 production/ Alveolar Ventilation

Question 5

Most important factor affecting PACO2?

Answer 5

1. Alveolar Ventilation

Because CO2 production is constant

Question 6

Why is PACO2 important?

Answer 6

To evaluate Alveolar Ventilation

Question 7

⬆️Alveolar Ventilation causes what to PACO2?

Answer 7

⬇️PACO2

(X2) —> halved

Question 8

⬇️Alveolar Ventilation causes what to PACO2?

Answer 8

⬆️PACO2

(X2) —> Doubled

Question 9

Metabolic rate must = Ventilation rate in order to ?

Answer 9

Maintain constant PaCO2

Question 10

How do you calculate PO2?

Answer 10

1. PO2= Fgas (21%) x Patm (760 mmHg)

Question 11

Normal PO2?

Answer 11

1. 160 mmHg

Question 12

How do you calculate PAO2?

Answer 12

PAO2= (Patm - 47)FIO2 - PaCO2/RQ

Question 13

Factors that affect PAO2?

Answer 13

1. Patm (760 mmHg)
2. FiO2 % (21%)
3. PACO2 (40mmHg)
4. RQ (consumed/produced CO2) (0.8)

Question 14

Normal PAO2?

Answer 14

1. 100 mmHg

Question 15

Effect of PaCO2 on PAO2?

Answer 15

1. ⬆️PaCO2 —> ⬇️PAO2

2. ⬇️PaCO2 —> ⬆️PAO2

Question 16

How do you calculate the rate of Diffusion? (Vgas)

Answer 16

Vgas = A/T x D x (P1-P2)

A= Surface Area 
T= Thickness of membrane 
D= Diffusion constante 
P1-P2= gradient across membrane

Question 17

Examples of ⬆️ and ⬇️ of A?

Answer 17

⬆️Exercise

⬇️Emphysema

Question 18

Examples of ⬆️ in T?

Answer 18

1. Pulmonary Fibrosis

Question 19

D (diffusion constant). Which gas has higher solubility?

1. O2
2. CO2

Answer 19

2. CO2

Question 20

What factor is more important for gas diffusion ?

1. Solubility
2. Gradient

Answer 20

1. Solubility

Question 21

Normal gradient of O2? (PAO2 - PvO2) ?

Answer 21

100-40= 60 mmHg

Question 22

Normal gradient for CO2? (PvCO2- PACO2)

Answer 22

47-40= 7 mmHg

Question 23

Why is important about a difussion limited substance, clinically?

Answer 23

1. It lets you know about the structures (A and T) of the lungs in terms of damage.

Question 24

How is the Diffusion Capacity affected during exercise ?

Answer 24

1. DL ⬆️⬆️

Question 25

What happens to Diffusion capacity during emphysema?

Answer 25

1. DL ⬇️⬇️