Respiratory Gases And Alveolar Air Equation

Question 1

Dalton’s law

Answer 1

Pgas = Fgas + PB

Question 2

Pressure of inspired air

Answer 2

PiO2 = 150mmHg

Question 3

Alveolar gas equation

Answer 3

PAO2 = PiO2 - (PACO2/R)

Normal
PAO2 = 100mmHg
PACO2 = 40mmHg

Question 4

Ambient air at sea level

Answer 4

150mmHg

Question 5

Hypoxemia

Answer 5

Decreased PaO2 
High alt: norm A:a gradient, O2
Hypoventilation: norm A:a gradient, O2
Diffusion defect: high A:a gradient, O2
Low V/Q: high A:a gradient, O2
R to L shunt: high A:a gradient, no O2

*L to R shunt does not cause hypoxemia

Question 6

Intrapulmonary shunts

Answer 6

Includes absolute shunts
No ventilation, V/Q = 0
Shunt like states
1 > V/Q > 0

Question 7

V/Q = 1

Answer 7

Blood is 100% oxygenated

Inc V/Q, blood still 100% oxygenated