Ventilation Perfusion Relationship

Question 1

Reason why alveolar PO2 has fallen to 100mmHg (1/3)

Answer 1

Removal of oxygen by pulmonary capillary blood

Continual replenishment by alveolar ventilation

Question 2

Fluctuation in alveolar PO2 each breath

Answer 2

3 mmHg

Tidal volume is small

Question 3

Alveolar PO2 is largely determined by the level of

Answer 3

Alveolar ventilation

Question 4

Decrease in alveolar ventilation
Decrease in alveolar PO2
Accumulation of PCO2

Answer 4

Hypoventilation

Question 5

In alveolar gas equation, if R (respiratory exchange ratio is normal), 0.8,
Fall in alveolar PO2 is __________ than rise in PCO2

Answer 5

Slightly greater

Question 6

CO2 stores are much greater than O2 stores because

Answer 6

Large CO2 amount in the form of bicarbonate (blood and interstitial fluid)

Question 7

Alveolar gas equation

Answer 7

Question 8

Alveolar Ventilation equation

Answer 8

Question 9

PO2 difference between alveolar gas and end capillary blood from incomplete diffusion is

Answer 9

SMALL

*can become larger during exercise, BG barrier thickened
Low O2 mixture is inhaled

Question 10

Diffusion limitation RARELY causes hypoxemia because

Answer 10

Rbc spend enough time in pulmonary capillary to allow complete equilibration

Question 11

Examples of diffusion limitation

Answer 11

Question 12

Blood that enters the arterial system without going through ventilated areas of the lung

Answer 12

SHUNT

Question 13

Examples of SHUNT

Answer 13

Bronchial Artery blood collected by pulmonary veins

Small amount of coronary VENOUS blood draining to
CAVITY of left ventricle thru Thebesian veins

——————

Pulmonary arteriovenous malformation
CHD

Question 14

The ratio of SHUNT flow to TOTAL flow is

Answer 14

SHUNT FRACTION

Question 15

Term used on what shunt would be if depression of arterial O2 concentration were caused by mixed venous blood

Answer 15

AS IF shunt

Question 16

O2 supplementation no effect on shunt but some elevation in arterial PO2 because of

Answer 16

O2 added to the capillary blood of ventilated lungs

Question 17

100% fio2 in shunt will cause a relatively large fall in PO2 from small depression of arterial o2 concentration because of

Answer 17

Almost flat slope of o2 dissociation curve

Question 18

Regional differences in gas exchange. INCREASED

Answer 18

V/Q ratio (0.6)

PO2
O2 concentration

PH

Question 19

Variation in PN2 is because of

Answer 19

Total pressure in the alveolar gas

Question 20

Large difference in ph down the lung

Answer 20

Reflects considerable variation in PCO2 of the blood

Question 21

Minimal contribution to overall O2 uptake made by the apex can be attributed

Answer 21

Low blood flow at the base

*during exercise, apex assumes larger share of O2 uptake

Question 22

Difference in CO2 uptake is MUCH LESS because

Answer 22

Related to ventilation

Question 23

Respiratory exchange ratio (CO2 output/O2 uptake) is HIGHER at the

Answer 23

APEX

Question 24

Oxygen dissociated curve is NON LINEAR hence

Answer 24

Units with high V/Q ratio will not increase o2 concentration

Question 25

VQ ratio of emphysema
(Destruction of capillaries)

Answer 25

INCREASED

Question 26

VQ ratio of chronic bronchitis

Answer 26

LOW

Question 27

4 causes of hypoxemia

Answer 27

Question 28

Normal A-a gradient

Answer 28

= 10 to 15 mmHg

Question 29

How to calculate A a gradient

Answer 29

Question 30

Larger alveoli

Answer 30

Apex

Question 31

Computations

Answer 31

Question 32

Regional differences by levitzky

Answer 32