V-Q Relationships

Question 1

How to get value of alveolar pO₂

Answer 1

calculate using

alveolar gas equation

Question 2

Alveolar gas equation

Answer 2

PA_O2 = PI_O2 - [pCO₂/R]

PA_O2 = alveolar pO₂

PI_O2 = inspired air pO₂

pCO₂ = measured arterial pCO₂

R = respiratory coefficient = CO₂ produced/O₂ consumed

Question 3

Purpose of calculating alveolar pO₂

Answer 3

compare it to arterial pO₂

using A-a gradient

Alveolar-arterial pO₂ gradient should be small (<15)

if >15, then there is pulmonary pathology for hypoxia

Question 4

Normal alveolar

pO₂

pCO₂

Answer 4

alveolar

pO₂: 100

pCO₂: 40

Question 5

Normal pulmonary artery

pO₂

pCO₂

Answer 5

pulmonary artery

pO₂: 40

pCO₂: 46

Question 6

Normal pulmonary vein

pO₂

pCO₂

Answer 6

pulmonary vein

pO₂: 100

pCO₂: 40

Question 7

Innervation of diaphragm

Answer 7

C3, 4, 5

keeps the diaphragm alive

Question 8

Perfusion obstruction name

Answer 8

thrombus

Question 9

Ventilation obstruction name

Answer 9

shunt

Question 10

Breathing compensation

hypoxia

hypercapnea

Answer 10

breathing cannot rectify hypoxia

-sigmoidal Hb-dependent dissociation-

can rectify hypercapnea (high CO₂)

-linear non-Hb dependent dissociation-